Home & Garden Garden How to Start a Food Forest By Ilana Strauss Ilana Strauss Yale University University of Illinois at Urbana-Champaign Ilana Strauss is a journalist who began writing for the Treehugger family in 2015. Her work has been featured in The Atlantic, The Cut, New York Magazine, and other publications. Learn about our editorial process Updated July 25, 2017 Food forests are an old idea gaining traction in modern times. Ilana Strauss Home & Garden Planting Guides Indoor Gardening Urban Farms Insects Gardens and orchards may look orderly, but they don't stay that way naturally. That's why food forests --- forests made up entirely of plants that can be eated --- are becoming popular. These ecosystems take a long time to get going, but once they're in motion, they basically maintain themselves. Plus, they can provide much more food than most traditional gardens. Nimrod Hochberg, an Israeli community organizer, is building a food forest inside a Tel Aviv park. He also lives on his family's food forest in the countryside, where he helps maintains 500 acres of fruits and vegetables, all growing wildly. I sat down with Hochberg to find out how you can start one of these forests, whether you've got a huge tract of land or a small backyard. Start with the basics As with any type of gardening, know your soil before you start planting your food forest. Ilana Strauss "The first thing you need is patience and knowledge that you are starting a long-term project," explained Hochberg. "The second thing you need is a piece of land --- the bigger the better." It's tempting to immediately buy fruit trees and plant them, but Hochberg says the soil is the first thing you should pay attention to. "A good farmer doesn't grow plants, he grows soil," Hochberg told me. In a natural environment, the dead leaves from a tree fall to the ground, slowly composting and turning into dirt. In traditional orchards, those dead leaves are frequently removed and replaced with fertilizer, but in nature, trees use thiscompost to grow. "To create a sustainable system, you need to imitate patterns you see in nature," Hochberg continued. "When we put mulch on the ground, we are imitating this natural cycle." So start your forest by covering your land with a heavy dose of mulch and giving it time to decompose. Remember water City planners tend to divert water into tunnels and away from towns, which can make it hard for plants to grow. So you need to figure out where your forest's water will come from. In his forest, Hochberg set up a pool to catch rainwater. The rain hits a roof first, then flows into the pool and is used to water the forest. "It depends on where you are," pointed out Hochberg. If you're in Israel or California, you may need an elaborate system like this. On the other hand, if you're in Costa Rica and get too much rain, you can probably just rely on nature. Move onto the starter plants Now that your soil is composted and land watered, you're ready to start planting. But don't buy that apple tree just yet! "First, grow plants that grow fast and easy," Hochberg explained. You need to start off with hardy plants, like legume trees and clovers, before you invest in more delicate trees. Let the tough plants literally grow like weeds for a few months or even a year. They'll make the area more hospitable to other plants by putting more nutrition in the soil, blocking hard winds and creating a better microclimate. "Trees are amazing temperature moderators," Hochberg said. The main attraction Eventually, your food forest will yield yummy produce, like eggplants. Ilana Strauss Finally, it's time to plant those fruit trees. Pick trees that grow naturally in your area (i.e., don't try to grow oranges in New York), and plant them between your "starter" trees. For the first year, you'll need to pay close attention to these delicate fruit trees. Water them, add compost and just generally baby them. After a year, you'll have better soil and your trees will be stronger, so you'll be able to let them grow on their own. "After a few years, you don't really need to maintain anything," Hochberg said. "My family's forest is in its sixth year, and for about 80 percent of the trees, we don't treat anymore." Don't limit your forest to trees. Real forests have many different kinds of plants living in the same environment, and food forests should too. Hochberg recommends planting "layers" --- big trees, small trees, bushes, small plants, vines and herbs --- next to each other. You might have big pecan trees with small mulberry trees underneath them, and lettuce, broccoli, herbs and mushrooms on the ground. "Because of the layers, you can get a lot of food," said Hochberg. "You can get much more food from a food forest than from a regular orchard." In addition, the plants help each other. Trees give shade to vegetables, which provide mulch to trees. You might even consider getting some chickens to live in your new ecosystem so you get fresh eggs from your built-in insect eaters. "It creates the feeling of a forest, not an orchard," said Hochberg. Prune out the starters Food forests can bring you closer to all the cycles of nature. Ilana Strauss After a few years, your food plants will be thriving, and you won't need the starter plants anymore. "Take them down," said Hochberg. "They've done their job." Building a food forest is a time-consuming process, but the results can be pretty amazing. "You get very intimate with your land. You know every tree, you know every bush, every bug," said Hochberg. "It connects you to the real world, gets you out of screens. Because nature is much more interesting."


A gas lift or bubble pump is a type of pump that can raise fluid between elevations by introducing gas bubbles into a vertical outlet tube; as the bubbles rise within the tube they cause a drop in the hydrostatic pressure behind them, causing the fluid to be pulled up. Gas lifts are commonly used as artificial lifts for water or oil, using compressed air or water vapor.
Gas lifts have been used for a variety of applications:
Coffee percolators and electric drip coffeemakers use vaporized water to lift hot water
Airlift pumps use compressed air to lift water
Pulser pumps use a subterranean air chamber to lift underground water
Suction dredges use a variety of the gas lift called an airlift pump to vacuum mud, sand and debris
Mist lifts use vaporized water to draw seawater in ocean thermal energy conversion systems


## Petroleum industry uses
In the United States, gas lift is used in 10% of the oil wells that have insufficient reservoir pressure to produce the well. In the petroleum industry, the process involves injecting gas through the tubing-casing annulus. Injected gas aerates the fluid to reduce its density; the formation pressure is then able to lift the oil column and forces the fluid out of the wellbore. Gas may be injected continuously or intermittently, depending on the producing characteristics of the well and the arrangement of the gas-lift equipment.
The amount of gas to be injected to maximize oil production varies based on well conditions and geometries. Too much or too little injected gas will result in less than maximum production. Generally, the optimal amount of injected gas is determined by well tests, where the rate of injection is varied and liquid production (oil and perhaps water) is measured. Alternatively, mathematical models can be used to estimate the optimum gas injection rate. Such models offer significant economic benefit, since they allow one to simulate the performance of an actual or planned gas-lifted well using a digital replica of the well.
Although the gas is recovered from the oil at a later separation stage, the process requires energy to drive a compressor to raise the pressure of the gas to a level where it can be re-injected.
The gas-lift mandrel is a device installed in the tubing string of a gas-lift well onto which or into which a gas-lift valve is fitted. There are two common types of mandrels. In a conventional gas-lift mandrel, a gas-lift valve is installed as the tubing is placed in the well. Thus, to replace or repair the valve, the tubing string must be pulled. In the side-pocket mandrel, however, the valve is installed and removed by wireline while the mandrel is still in the well, eliminating the need to pull the tubing to repair or replace the valve.
A gas-lift valve is a device installed on (or in) a gas-lift mandrel, which in turn is put on the production tubing of a gas-lift well. Tubing and casing pressures cause the valve to open and close, thus allowing gas to be injected into the fluid in the tubing to cause the fluid to rise to the surface. In the lexicon of the industry, gas-lift mandrels are said to be "tubing retrievable" wherein they are deployed and retrieved attached to the production tubing. See gas-lift mandrel.
Gas lift operation can be optimized in different ways. The newest way is using risk-optimization which considers all aspects for gas lift allocation.


## Gulonolactone oxidase deficiency
The non-functional gulonolactone oxidase pseudogene (GULOP) was mapped to human chromosome 8p21, which corresponds to an evolutionarily conserved segment on either porcine chromosome 4 (SSC4) or 14 (SSC14). GULO produces the precursor to ascorbic acid, which spontaneously converts to the vitamin itself.
The loss of activity of the gene encoding L-gulonolactone oxidase (GULO) has occurred separately in the history of several species. GULO activity has been lost in some species of bats, but others retain it. The loss of this enzyme activity is responsible for the inability of guinea pigs to enzymatically synthesize vitamin C. Both these events happened independently of the loss in the haplorrhine suborder of primates, which includes humans.
The remnant of this non-functional gene with many mutations is still present in the genomes of guinea pigs and humans. It is unknown if remains of the gene exist in the bats who lack GULO activity. The function of GULO appears to have been lost several times, and possibly re-acquired, in several lines of passerine birds, where ability to make vitamin C varies from species to species.
Loss of GULO activity in the primate order occurred about 63 million years ago, at about the time it split into the suborders Haplorhini (which lost the enzyme activity) and Strepsirrhini (which retained it). The haplorhine ("simple-nosed") primates, which cannot make vitamin C enzymatically, include the tarsiers and the simians (apes, monkeys and humans). The strepsirrhine ("bent-nosed" or "wet-nosed") primates, which can still make vitamin C enzymatically, include lorises, galagos, pottos, and, to some extent, lemurs.
L-Gulonolactone oxidase deficiency has been called "hypoascorbemia" and is described by OMIM (Online Mendelian Inheritance in Man) as "a public inborn error of metabolism", as it affects all humans. There exists a wide discrepancy between the amounts of ascorbic acid other primates consume and what are recommended as "reference intakes" for humans. In its patently pathological form, the effects of ascorbate deficiency are manifested as scurvy.


## Consequences of loss
It is likely that some level of adaptation occurred after the loss of the GULO gene by primates. Erythrocyte Glut1 and associated dehydroascorbic acid uptake modulated by stomatin switch are unique traits of humans and the few other mammals that have lost the ability to synthesize ascorbic acid from glucose. As GLUT transporters and stomatin are ubiquitously distributed in different human cell types and tissues, similar interactions may occur in human cells other than erythrocytes.
Linus Pauling observed that after the loss of endogenous ascorbate production, apo(a) and Lp(a) were greatly favored by evolution, acting as ascorbate surrogate, since the frequency of occurrence of elevated Lp(a) plasma levels in species that had lost the ability to synthesize ascorbate is great. Also, only primates share regulation of CAMP gene expression by vitamin D, which occurred after the loss of GULO gene.
Johnson et al. have hypothesized that the mutation of the GULOP pseudogene so that it stopped producing GULO may have been of benefit to early primates by increasing uric acid levels and enhancing fructose effects on weight gain and fat accumulation. With a shortage of food supplies this gave mutants a survival advantage.

## Animal models
Studies of human diseases have benefited from the availability of small laboratory animal models. However, the tissues of animal models with a GULO gene generally have high levels of ascorbic acid and so are often only slightly influenced by exogenous vitamin C. This is a major handicap for studies involving the endogenous redox systems of primates and other animals that lack this gene.
Guinea pigs are a popular human model. They lost the ability to make GULO 20 million years ago.
In 1999, Maeda et al. genetically engineered mice with inactivated GULO gene. The mutant mice, like humans, entirely depend on dietary vitamin C, and they show changes indicating that the integrity of their vasculature is compromised. GULO--/-- mice have been used as a human model in multiple subsequent studies.
There have been successful attempts to activate lost enzymatic function in different animal species. Various GULO mutants were also identified.


Selection bias is the bias introduced by the selection of individuals, groups, or data for analysis in such a way that proper randomization is not achieved, thereby failing to ensure that the sample obtained is representative of the population intended to be analyzed. It is sometimes referred to as the selection effect. The phrase "selection bias" most often refers to the distortion of a statistical analysis, resulting from the method of collecting samples. If the selection bias is not taken into account, then some conclusions of the study may be false.

## Types of bias
### Sampling bias
Sampling bias is systematic error due to a non-random sample of a population, causing some members of the population to be less likely to be included than others, resulting in a biased sample, defined as a statistical sample of a population (or non-human factors) in which all participants are not equally balanced or objectively represented. It is mostly classified as a subtype of selection bias, sometimes specifically termed sample selection bias, but some classify it as a separate type of bias.
A distinction of sampling bias (albeit not a universally accepted one) is that it undermines the external validity of a test (the ability of its results to be generalized to the rest of the population), while selection bias mainly addresses internal validity for differences or similarities found in the sample at hand. In this sense, errors occurring in the process of gathering the sample or cohort cause sampling bias, while errors in any process thereafter cause selection bias.
Examples of sampling bias include self-selection, pre-screening of trial participants, discounting trial subjects/tests that did not run to completion and migration bias by excluding subjects who have recently moved into or out of the study area, length-time bias, where slowly developing disease with better prognosis is detected, and lead time bias, where disease is diagnosed earlier for participants than in comparison populations, although the average course of disease is the same.

### Time interval
Early termination of a trial at a time when its results support the desired conclusion.
A trial may be terminated early at an extreme value (often for ethical reasons), but the extreme value is likely to be reached by the variable with the largest variance, even if all variables have a similar mean.


## Types of bias
### Exposure
Susceptibility bias
Clinical susceptibility bias, when one disease predisposes for a second disease, and the treatment for the first disease erroneously appears to predispose to the second disease. For example, postmenopausal syndrome gives a higher likelihood of also developing endometrial cancer, so estrogens given for the postmenopausal syndrome may receive a higher than actual blame for causing endometrial cancer.
Protopathic bias, when a treatment for the first symptoms of a disease or other outcome appear to cause the outcome. It is a potential bias when there is a lag time from the first symptoms and start of treatment before actual diagnosis. It can be mitigated by lagging, that is, exclusion of exposures that occurred in a certain time period before diagnosis.
Indication bias, a potential mixup between cause and effect when exposure is dependent on indication, e.g. a treatment is given to people in high risk of acquiring a disease, potentially causing a preponderance of treated people among those acquiring the disease. This may cause an erroneous appearance of the treatment being a cause of the disease.

### Data
Partitioning (dividing) data with knowledge of the contents of the partitions, and then analyzing them with tests designed for blindly chosen partitions.
Post hoc alteration of data inclusion based on arbitrary or subjective reasons, including:
Cherry picking, which actually is not selection bias, but confirmation bias, when specific subsets of data are chosen to support a conclusion (e.g. citing examples of plane crashes as evidence of airline flight being unsafe, while ignoring the far more common example of flights that complete safely. See: availability heuristic)
Rejection of bad data on (1) arbitrary grounds, instead of according to previously stated or generally agreed criteria or (2) discarding "outliers" on statistical grounds that fail to take into account important information that could be derived from "wild" observations.

### Studies
Selection of which studies to include in a meta-analysis (see also combinatorial meta-analysis).
Performing repeated experiments and reporting only the most favorable results, perhaps relabelling lab records of other experiments as "calibration tests", "instrumentation errors" or "preliminary surveys".
Presenting the most significant result of a data dredge as if it were a single experiment (which is logically the same as the previous item, but is seen as much less dishonest).


## Types of bias
### Attrition
Attrition bias is a kind of selection bias caused by attrition (loss of participants), discounting trial subjects/tests that did not run to completion. It is closely related to the survivorship bias, where only the subjects that "survived" a process are included in the analysis or the failure bias, where only the subjects that "failed" a process are included. It includes dropout, nonresponse (lower response rate), withdrawal and protocol deviators. It gives biased results where it is unequal in regard to exposure and/or outcome. For example, in a test of a dieting program, the researcher may simply reject everyone who drops out of the trial, but most of those who drop out are those for whom it was not working. Different loss of subjects in intervention and comparison group may change the characteristics of these groups and outcomes irrespective of the studied intervention.
Lost to follow-up, is another form of Attrition bias, mainly occurring in medicinal studies over a lengthy time period. Non-Response or Retention bias can be influenced by a number of both tangible and intangible factors, such as; wealth, education, altruism, initial understanding of the study and its requirements. Researchers may also be incapable of conducting follow-up contact resulting from inadequate identifying information and contact details collected during the initial recruitment and research phase.

### Observer selection
Philosopher Nick Bostrom has argued that data are filtered not only by study design and measurement, but by the necessary precondition that there has to be someone doing a study. In situations where the existence of the observer or the study is correlated with the data, observation selection effects occur, and anthropic reasoning is required.
An example is the past impact event record of Earth: if large impacts cause mass extinctions and ecological disruptions precluding the evolution of intelligent observers for long periods, no one will observe any evidence of large impacts in the recent past (since they would have prevented intelligent observers from evolving). Hence there is a potential bias in the impact record of Earth. Astronomical existential risks might similarly be underestimated due to selection bias, and an anthropic correction has to be introduced.


## Types of bias
### Volunteer bias
Self-selection bias or a volunteer bias in studies offer further threats to the validity of a study as these participants may have intrinsically different characteristics from the target population of the study. Studies have shown that volunteers tend to come from a higher social standing than from a lower socio-economic background. Furthermore, another study shows that women are more probable to volunteer for studies than males. Volunteer bias is evident throughout the study life-cycle, from recruitment to follow-ups. More generally speaking volunteer response can be put down to individual altruism, a desire for approval, personal relation to the study topic and other reasons. As with most instances mitigation in the case of volunteer bias is an increased sample size.

## Mitigation
In the general case, selection biases cannot be overcome with statistical analysis of existing data alone, though Heckman correction may be used in special cases. An assessment of the degree of selection bias can be made by examining correlations between exogenous (background) variables and a treatment indicator. However, in regression models, it is correlation between unobserved determinants of the outcome and unobserved determinants of selection into the sample which bias estimates, and this correlation between unobservables cannot be directly assessed by the observed determinants of treatment.
When data are selected for fitting or forecast purposes, a coalitional game can be set up so that a fitting or forecast accuracy function can be defined on all subsets of the data variables.

## Related issues
Selection bias is closely related to:
publication bias or reporting bias, the distortion produced in community perception or meta-analyses by not publishing uninteresting (usually negative) results, or results which go against the experimenter's prejudices, a sponsor's interests, or community expectations.
confirmation bias, the general tendency of humans to give more attention to whatever confirms our pre-existing perspective; or specifically in experimental science, the distortion produced by experiments that are designed to seek confirmatory evidence instead of trying to disprove the hypothesis.
exclusion bias, results from applying different criteria to cases and controls in regards to participation eligibility for a study/different variables serving as basis for exclusion.


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PlotJuggler is a tool to visualize time series that is fast, powerful and intuitive.
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## Comparison of Life Cycle Environmental Impacts from Meal Kits and Grocery Store Meals
Meal kits contain ingredients for cooking a meal that are pre-portioned, packaged, and delivered to a consumer's residence. Life cycle environmental impacts associated with climate change, acidification, eutrophication, land use, and water use are compared for five dinner recipes sourced as meal kits and through grocery store retailing. Inventory data are obtained from direct measurement of ingredients and packaging, supplemented with literature data for supply chain and production parameters. Results indicate that, on average, grocery meal greenhouse gas emissions are 33% higher than meal kits (8.1 kg CO2e/meal compared with 6.1 kg CO2e/meal kit). Other impact categories follow similar trends. A Monte Carlo analysis finds higher median emissions for grocery meals than meal kits for four out of five meals, occurring in 100% of model runs for two of five meals. Results suggest that meal kits' streamlined and direct-to-consumer supply chains (-1.05 kg CO2e/meal), reduced food waste (-0.86 kg CO2e/meal), and lower last-mile transportation emissions (-0.45 kg CO2e/meal), appear to be sufficient to offset observed increases in packaging (0.17 kg CO2e/meal). Additionally, meal kit refrigeration packs present an average emissions decrease compared with retail refrigeration (-0.37 kg CO2e/meal). Meals with the largest environmental impact either contain red meat or are associated with large amounts of wasted food. The one meal kit with higher emissions is due to food mass differences rather than supply chain logistics. Meal kits are an evolving mode for food supply, and the environmental effects of potential changes to meal kit provision and grocery retailing are discussed.


In thermodynamics, an irreversible process is a process that cannot be undone. All complex natural processes are irreversible, although a phase transition at the coexistence temperature (e.g. melting of ice cubes in water) is well approximated as reversible.
A change in the thermodynamic state of a system and all of its surroundings cannot be precisely restored to its initial state by infinitesimal changes in some property of the system without expenditure of energy. A system that undergoes an irreversible process may still be capable of returning to its initial state. Because entropy is a state function, the change in entropy of the system is the same whether the process is reversible or irreversible. However, the impossibility occurs in restoring the environment to its own initial conditions. An irreversible process increases the total entropy of the system and its surroundings. The second law of thermodynamics can be used to determine whether a hypothetical process is reversible or not.
Intuitively, a process is reversible if there is no dissipation. For example, Joule expansion is irreversible because initially the system is not uniform. Initially, there is part of the system with gas in it, and part of the system with no gas. For dissipation to occur, there needs to be such a non uniformity. This is just the same as if in a system one section of the gas was hot, and the other cold. Then dissipation would occur; the temperature distribution would become uniform with no work being done, and this would be irreversible because you couldn't add or remove heat or change the volume to return the system to its initial state. Thus, if the system is always uniform, then the process is reversible, meaning that you can return the system to its original state by either adding or removing heat, doing work on the system, or letting the system do work. As another example, to approximate the expansion in an internal combustion engine as reversible, we would be assuming that the temperature and pressure uniformly change throughout the volume after the spark. Obviously, this is not true and there is a flame front and sometimes even engine knocking. One of the reasons that Diesel engines are able to attain higher efficiency is that the combustion is much more uniform, so less energy is lost to dissipation and the process is closer to reversible.
The phenomenon of irreversibility results from the fact that if a thermodynamic system, which is any system of sufficient complexity, of interacting molecules is brought from one thermodynamic state to another, the configuration or arrangement of the atoms and molecules in the system will change in a way that is not easily predictable. Some "transformation energy" will be used as the molecules of the "working body" do work on each other when they change from one state to another. During this transformation, there will be some heat energy loss or dissipation due to intermolecular friction and collisions. This energy will not be recoverable if the process is reversed.
Many biological processes that were once thought to be reversible have been found to actually be a pairing of two irreversible processes. Whereas a single enzyme was once believed to catalyze both the forward and reverse chemical changes, research has found that two separate enzymes of similar structure are typically needed to perform what results in a pair of thermodynamically irreversible processes.


## Well-being and GDP: why we need them both
By Romina Boarini, OECD
Measuring well-being is about going beyond the cold numbers of GDP. But cold as it may be, GDP remains a very important indicator for measuring the economic performance of countries, which is a fundamental driver of well-being. This is not only because income means higher material standards but also because income is needed to sustain private and public spending in non-material components of well-being, such as education and health. However, there is an increasing recognition that focusing on GDP alone is not enough to achieve better lives for all.
The chart below demonstrates this by showing a country's s GDP per capita alongside its performance on the OECD Better Life Index. The relationship is positive -- in other words, countries with higher GDP per capita are also those where well-being is higher on average. However this relationship becomes weaker as a country's income grows, suggesting that once income reaches a certain level, increased income is less likely to generate well-being. The other interesting feature of this chart is that some countries do better at delivering wellbeing as measured by the Better Life Index than they do if gauged only on the basis of economic production per capita. This is the case for all the Nordic European countries but also for New Zealand. On the other hand, there are countries that do better in GDP per capita than on average well-being, for instance the United States and Switzerland.
So why in these two sets of countries do economic performance and well-being not go strictly hand in hand? One explanation is that the countries that do better in terms of well-being have made the choice of working less to achieve a better work and life balance. This translates into lower income but also increased leisure time that can be shared with friends and family, or that is used for volunteering and engaging with the community. Another reason is that these countries have better environmental quality, partly because of lower economic production and thus pollution. Well-being is a matter of democracy and societal choices, what really matters at the end of the day is whether countries are where their citizens would like them to be. It can be higher economic production or more time for life, longer healthy lives or more connected neighbourhoods. What is important is to collect the relevant set of statistics to judge whether collective objectives are met and ensure that governments are paying the righight degree of attention to these statistics.
Note: Norway refers to mainland GDP per capita


## What Are Matching Orders?
Matching orders is the process by which a securities exchange pairs one or more unsolicited buy orders to one or more sell orders to make trades. This can be contrasted with requests for a quote (RFQ) in a security to proceed with a trade.
If one investor wants to buy a quantity of stock and another wants to sell the same quantity at the same price, their orders match, and a transaction is effected. The work of pairing these orders is the process of order matching whereby exchanges identify buy orders, or bids, with corresponding sell orders, or asks, to execute them. Over the past decade, this process has become almost entirely automated.

### Key Takeaways
- Matching orders is the process of identifying and effecting a trade between equal and opposite requests for a security (i.e., a buy and a sale at the same price).
- Order matching is how many exchanges pair buyers and sellers at compatible prices for efficient and orderly trading.
- Over the past decade, this process has become almost entirely automated.

## How Matching Orders Works
Matching the orders of buyers and sellers is the primary work of specialists and market makers in the exchanges. The matches happen when compatible buy orders and sell orders for the same security are submitted in close proximity in price and time.
Generally, a buy order and a sell order are compatible if the maximum price of the buy order matches or exceeds the minimum price of the sell order. From there, the computerized, order-matching systems of different exchanges use a variety of methods to prioritize orders for matching.

### Fast Fact
Today, most exchanges match orders using computer algorithms; but historically, brokers matched orders through face-to-face interactions on a trading floor in an open-outcry auction.
Quick, accurate order matching is a critical component of an exchange. Investors, particularly active investors and day traders, will look for ways to minimize inefficiencies in trading from every possible source. A slow order-matching system may cause buyers or sellers to execute trades at less-than-ideal prices, eating into investors' profits. If some order-matching protocols tend to favor buyers, and others favor sellers, these methods become exploitable.
This is one of the areas where high-frequency trading (HFT) was able to improve efficiency. Exchanges aim to prioritize trades in a way that benefits buyers and sellers equally so as to maximize order volume---the lifeblood of the exchange.


## Popular Algorithms for Matching Orders
All major markets have transitioned to electronic matching. Each securities exchange uses its own specific algorithm to match orders. Broadly, they fall under two categories: first-in-first-out (FIFO) and pro-rata.

### FIFO
Under a basic FIFO algorithm, or price-time-priority algorithm, the earliest active buy order at the highest price takes priority over any subsequent order at that price, which in turn takes priority over any active buy order at a lower price. For example, if a buy order for 200 shares of stock at \$90 per share precedes an order for 50 shares of the same stock at the same price, the system must match the entire 200-share order to one or more sell orders before beginning to match any portion of the 50-share order.

### Pro-Rata
Under a basic pro-rata algorithm, the system prioritizes active orders at a particular price, proportional to the relative size of each order. For example, if both a 200-share buy order and a 50-share buy order at the same price are active when a compatible 200-share sell order arrives, the system will match 160 shares to the 200-share buy order and 40 shares to the 50-share buy order.
Since the sell order is not large enough to fulfill both buy orders, the system will partially fill both. In this case, the pro-rata matching algorithm fills 80 percent of each order.


A tetanic contraction (also called tetanized state, tetanus, or physiologic tetanus, the latter to differentiate from the disease called tetanus) is a sustained muscle contraction evoked when the motor nerve that innervates a skeletal muscle emits action potentials at a very high rate. During this state, a motor unit has been maximally stimulated by its motor neuron and remains that way for some time. This occurs when a muscle's motor unit is stimulated by multiple impulses at a sufficiently high frequency. Each stimulus causes a twitch. If stimuli are delivered slowly enough, the tension in the muscle will relax between successive twitches. If stimuli are delivered at high frequency, the twitches will overlap, resulting in tetanic contraction. A tetanic contraction can be either unfused (incomplete) or fused (complete). An unfused tetanus is when the muscle fibers do not completely relax before the next stimulus because they are being stimulated at a fast rate; however there is a partial relaxation of the muscle fibers between the twitches. Fused tetanus is when there is no relaxation of the muscle fibers between stimuli and it occurs during a high rate of stimulation. A fused tetanic contraction is the strongest single-unit twitch in contraction. When tetanized, the contracting tension in the muscle remains constant in a steady state. This is the maximal possible contraction. During tetanic contractions, muscles can shorten, lengthen or remain constant length.
Tetanic contraction is usually normal (such as when holding up a heavy box). Muscles often exhibit some level of tetanic activity, leading to muscle tone, in order to maintain posture; for example, in a crouching position, some muscles require sustained contraction to hold the position. Tetanic contraction can exist in a variety of states, including isotonic and isometric forms---for example, lifting a heavy box off the floor is isotonic, but holding it at the elevated position is isometric. Isotonic contractions place muscles in a constant tension but the muscle length changes, while isometric contractions hold a constant muscle length.
Voluntary sustained contraction is a normal (physiologic) process (as in the crouching or box-holding examples), but involuntary sustained contraction exists on a spectrum from physiologic to disordered (pathologic). Muscle tone is a healthy form of involuntary sustained partial contraction. In comparison with tetanic contraction in an isometric state (such as holding up a heavy box for several minutes), it differs only in the percentage of motor units participating at any moment and the frequency of neural signals; but the low percentage and low frequency in healthy tone are the key factors defining it as healthy (and not tetanic). Involuntary sustained contraction of a hypertonic type, however, is a pathologic process. On the mild part of the spectrum, cramps, spasms, and even tetany are often temporary and nonsevere. On the moderate to severe parts of the spectrum are dystonia, trismus, pathologic tetanus, and other movement disorders featuring involuntary sustained strong contractions of skeletal muscle.


# High-Performance Computing Data Center Waste Heat Reuse
At the Energy Systems Integration Facility (ESIF), heat exchangers in the High-Performance Computing Data Center enable the reuse of energy from computing waste heat.
With heat exchangers, heat energy in the energy recovery water (ERW) loop becomes available to heat the facility's process hot water (PHW) loop. Once heated, the PHW loop supplies:
- Active chilled beams to heat the office space
- Air handlers to heat the conference and high bay spaces
- Snow melt loop in the courtyard of the ESIF's main entrance
- District heating loop:
  - If additional heat is needed for the building, the PHW loop can draw heat from the campus heating loop
  - If surplus heat is available, the PHW loop can provide heat to the campus heating loop. During transition months (April and October), excess heat from the ESIF has been sufficient to provide heat for other buildings, shortening the time boilers are needed to provide campus heat.
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Computer vision syndrome (CVS) is a condition resulting from focusing the eyes on a computer or other display device for protracted, uninterrupted periods of time and the eye's muscles being unable to recover from the constant tension required to maintain focus on a close object.

## Symptoms
Some symptoms of CVS include headaches, blurred vision, neck pain, fatigue, eye strain, dry eyes, irritated eyes, double vision, vertigo/dizziness, polyopia, and difficulty refocusing the eyes. These symptoms can be further aggravated by improper lighting conditions (i.e. glare, strong blue-spectrum backlights, or bright overhead lighting) or air moving past the eyes (e.g. overhead vents, or direct air from a fan).


# Men and things, women and people: a meta-analysis of sex differences in interests
- PMID: 19883140
- DOI: 10.1037/a0017364

## Abstract
The magnitude and variability of sex differences in vocational interests were examined in the present meta-analysis for Holland's (1959, 1997) categories (Realistic, Investigative, Artistic, Social, Enterprising, and Conventional), Prediger's (1982) Things-People and Data-Ideas dimensions, and the STEM (science, technology, engineering, and mathematics) interest areas. Technical manuals for 47 interest inventories were used, yielding 503,188 respondents. Results showed that men prefer working with things and women prefer working with people, producing a large effect size (d = 0.93) on the Things-People dimension. Men showed stronger Realistic (d = 0.84) and Investigative (d = 0.26) interests, and women showed stronger Artistic (d = -0.35), Social (d = -0.68), and Conventional (d = -0.33) interests. Sex differences favoring men were also found for more specific measures of engineering (d = 1.11), science (d = 0.36), and mathematics (d = 0.34) interests. Average effect sizes varied across interest inventories, ranging from 0.08 to 0.79. The quality of interest inventories, based on professional reputation, was not differentially related to the magnitude of sex differences. Moderators of the effect sizes included interest inventory item development strategy, scoring method, theoretical framework, and sample variables of age and cohort. Application of some item development strategies can substantially reduce sex differences. The present study suggests that interests may play a critical role in gendered occupational choices and gender disparity in the STEM fields.


If you've ever grown fresh herbs, you know that some plants just grow and grow---sometimes faster than you can eat them. Thankfully, eating them isn't the only thing you can do. Consider using fresh aromatic herbs like basil and rosemary as an all-natural air freshener for your car or another small space.
This tip comes to us from the folks at Stylist, which suggests using Basil to freshen your car by putting some fresh basil leaves on a piece of newspaper and just letting it dry itself out in the back of your car. The windows make it a natural greenhouse, so as the basil dries, the delicious smell will spread through your vehicle---it's much better than the gym socks in the backseat or the lingering smell of fast food from your last McDonald's stop.
The idea got us thinking though: why stop with basil? Rosemary, tarragon, and thyme are just as aromatic, and can work just as well. Plus, there's no reason to stop with your car: as long as you have a space that will get some light (and therefore heat), the herbs will dry nicely and smell great. Put a few leaves on some newspaper and rest them on your windowsill in your home office, and you'll have a natural air freshener that's perfect for small spaces (large spaces need not apply, obviously.) Just be careful, the smell might make you hungry.
How to Remove Car Odors with Basil \| Stylist
Photo by Chris Pillen.


The neocortex, also called the neopallium, isocortex, or the six-layered cortex, is a set of layers of the mammalian cerebral cortex involved in higher-order brain functions such as sensory perception, cognition, generation of motor commands, spatial reasoning, and language. The neocortex is further subdivided into the true isocortex and the proisocortex.
In the human brain, the cerebral cortex consists of the larger neocortex and the smaller allocortex, respectively taking up 90% and 10%. The neocortex is made up of six layers, labelled from the outermost inwards, I to VI.

## Etymology
The term is from cortex, Latin, "bark" or "rind", combined with neo-, Greek, "new". Neopallium is a similar hybrid, from Latin pallium, "cloak". Isocortex and allocortex are hybrids with Greek isos, "same", and allos, "other".

## Anatomy
The neocortex is the most developed in its organisation and number of layers, of the cerebral tissues. The neocortex consists of the grey matter, or neuronal cell bodies and unmyelinated fibers, surrounding the deeper white matter (myelinated axons) in the cerebrum. This is a very thin layer though, about 2--4 mm thick. There are two types of cortex in the neocortex, the proisocortex and the true isocortex. The pro-isocortex is a transitional area between the true isocortex and the periallocortex (part of the allocortex). It is found in the cingulate cortex (part of the limbic system), in Brodmann's areas 24, 25, 30 and 32, the insula and the parahippocampal gyrus.
Of all the mammals studied to date (including humans), a species of oceanic dolphin known as the long-finned pilot whale has been found to have the most neocortical neurons.


## Anatomy
### Cortical columns
The neocortex is often described as being arranged in vertical structures called cortical columns, patches of neocortex with a diameter of roughly 0.5 mm (and a depth of 2 mm, i.e., spanning all six layers). These columns are often thought of as the basic repeating functional units of the neocortex, but their many definitions, in terms of anatomy, size, or function, are generally not consistent with each other, leading to a lack of consensus regarding their structure or function or even whether it makes sense to try to understand the neocortex in terms of columns.

## Function
The neocortex is derived embryonically from the dorsal telencephalon, which is the rostral part of the forebrain. The neocortex is divided into regions demarcated by the cranial sutures in the skull above, into frontal, parietal, occipital, and temporal lobes, which perform different functions. For example, the occipital lobe contains the primary visual cortex, and the temporal lobe contains the primary auditory cortex. Further subdivisions or areas of neocortex are responsible for more specific cognitive processes. In humans, the frontal lobe contains areas devoted to abilities that are enhanced in or unique to our species, such as complex language processing localized to the ventrolateral prefrontal cortex (Broca's area). In humans and other primates, social and emotional processing is localized to the orbitofrontal cortex.
The neocortex has also been shown to play an influential role in sleep, memory and learning processes. Semantic memories appear to be stored in the neocortex, specifically the anterolateral temporal lobe of the neocortex. It is also involved in instrumental conditioning; responsible for transmitting sensory information and information about plans for movement to the basal ganglia. The firing rate of neurons in the neocortex also has an effect on slow-wave sleep. When the neurons are at rest and are hyperpolarizing, a period of inhibition occurs during a slow oscillation, called the down state. When the neurons of the neocortex are in the excitatory depolarizing phase and are firing briefly at a high rate, a period of excitation occurs during a slow oscillation, called the up state.


The extrinsic extensor muscles of the hand are located in the back of the forearm and have long tendons connecting them to bones in the hand, where they exert their action. Extrinsic denotes their location outside the hand. Extensor denotes their action which is to extend, or open flat, joints in the hand. They include the extensor carpi radialis longus (ECRL), extensor carpi radialis brevis (ECRB), extensor digitorum (ED), extensor digiti minimi (EDM), extensor carpi ulnaris (ECU), abductor pollicis longus (APL), extensor pollicis brevis (EPB), extensor pollicis longus (EPL), and extensor indicis (EI).


## Extensor digitorum tendons
The ED tendons are more complex in their course. Opposite the metacarpophalangeal joint each tendon is bound by fasciculi to the collateral ligaments and serves as the dorsal ligament of this joint; after having crossed the joint, it spreads out into a broad aponeurosis, which covers the dorsal surface of the first phalanx and is reinforced, in this situation, by the tendons of the Interossei and Lumbricalis.
Opposite the first interphalangeal joints this aponeurosis divides into three slips; an intermediate and two collateral: the former is inserted into the base of the second phalanx; and the two collateral, which are continued onward along the sides of the second phalanx, unite by their contiguous margins, and are inserted into the dorsal surface of the last phalanx. As the tendons cross the interphalangeal joints, they furnish them with dorsal ligaments. The tendon to the index finger is accompanied by the EI, which lies on its ulnar side. On the back of the hand, the tendons to the middle, ring, and little fingers are connected by two obliquely placed bands, one from the third tendon passing downward and lateralward to the second tendon, and the other passing from the same tendon downward and medialward to the fourth.
Occasionally the first tendon is connected to the second by a thin transverse band. Collectively, these are known as the sagittal bands; they serve to maintain the central alignment of the extensor tendons over the metacarpal head, thus increasing the available leverage. Injuries (such as by an external flexion force during active extension) may allow the tendon to dislocate into the intermetacarpal space; the extensor tendon then acts as a flexor and the finger may no longer be actively extended. This may be corrected surgically by using a slip of the extensor tendon to replace the damaged ligamentous band

## Anatomical snuff box
The EPL tendon crosses obliquely the tendons of the ECRL and ECRB, and is separated from the EPB by a triangular interval, the anatomical snuff box, in which the radial artery is found.


## Insertion and action
The ECRL inserts into the dorsal surface of the base of the second metacarpal bone on its radial side to extend and abduct the wrist. The ECRB inserts into the lateral dorsal surface of the base of the third metacarpal bone, with a few fibres inserting into the medial dorsal surface of the second metacarpal bone, also to extend and abduct the wrist. The ED inserts into the middle and distal phalanges to extend the fingers and wrist. Opposite the head of the second metacarpal bone, the EI joins the ulnar side of the ED tendon to extend the index finger. The EDM has a similar role for the little finger. The ECU inserts at the base of the 5th metacarpal to extend and adduct the wrist. The APL inserts into the radial side of the base of the first metacarpal bone to abduct the thumb at the carpometacarpal joint and may continue to abduct the wrist. The EPB inserts into the base of the first phalanx of the thumb to extend and abduct the thumb at the carpometacarpal and MCP joints.
The EPL inserts on the base of the distal phalanx of the thumb. It uses the dorsal tubercle on the radius as fulcrum to help the EPB with its action as well as extending the distal phalanx of the thumb. Because the index finger and little finger have separate extensors, these fingers can be moved more independently than the other fingers.

## Neurovascular supply
The ECU is supplied by the ulnar artery. The APL, EPB, EPL, EI, ED, and EDM are supplied by the Posterior interosseous artery, a branch of the ulnar artery. The ECRL and ECRB receive blood from the radial artery.
The ECRL is supplied by the radial nerve and the ECRB by its deep branch. The remaining extrinsic hand extensors are supplied by the posterior interosseus nerve, another branch of the radial nerve.

## See also
Extensor digitorum reflex


# Economics \> Econometrics
\[Submitted on 23 Mar 2018 (v1), last revised 1 Dec 2020 (this version, v4)\]

# Title:Difference-in-Differences with Multiple Time Periods
View PDF
> Abstract:In this article, we consider identification, estimation, and inference procedures for treatment effect parameters using Difference-in-Differences (DiD) with (i) multiple time periods, (ii) variation in treatment timing, and (iii) when the "parallel trends assumption" holds potentially only after conditioning on observed covariates. We show that a family of causal effect parameters are identified in staggered DiD setups, even if differences in observed characteristics create non-parallel outcome dynamics between groups. Our identification results allow one to use outcome regression, inverse probability weighting, or doubly-robust estimands. We also propose different aggregation schemes that can be used to highlight treatment effect heterogeneity across different dimensions as well as to summarize the overall effect of participating in the treatment. We establish the asymptotic properties of the proposed estimators and prove the validity of a computationally convenient bootstrap procedure to conduct asymptotically valid simultaneous (instead of pointwise) inference. Finally, we illustrate the relevance of our proposed tools by analyzing the effect of the minimum wage on teen employment from 2001--2007. Open-source software is available for implementing the proposed methods.

## Submission history
From: Pedro H. C. Sant'Anna \[view email\]
\[v1\] Fri, 23 Mar 2018 23:45:05 UTC (132 KB)
\[v2\] Fri, 31 Aug 2018 19:30:23 UTC (758 KB)
\[v3\] Tue, 18 Aug 2020 03:32:06 UTC (65 KB)
\[v4\] Tue, 1 Dec 2020 16:15:59 UTC (884 KB)
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Although it sounds esoteric, the feed conversion rate is at the heart of raising a sustainable chicken.  Also known as the feed to meat ratio, this number is simply the pounds of feed given to a chicken divided by the weight of the cleaned carcass.\
The sad truth is that the feed conversion rate for chickens raised by nearly all backyard hobbyists is two, three, or even four times as high as the ratio for industrial chickens.  Yes, you do end up with a higher quality chicken that lived a happier life if you raise it yourself, but that\
chicken will not only take more money out of your pocket than buying one from the store would, your homegrown chicken will also have a larger environmental footprint.  In my mind, that's unsustainable.
Let's look at some feed to meat conversion ratios:
- 2 : 1 --- what the industry claims they get for factory farmed Cornish Cross.\
  (Hard to tell if this is true. My other numbers come from extension service websites or my own experience, both of which I trust more.)
- 3.5 : 1 --- what you can expect to get from pastured Cornish Cross in optimum weather.
- 5.2 : 1 --- Freedom Rangers on pasture, again optimal conditions. (Other "slow" broiler breeds are in the same ball park.)
- 6.2 : 1 --- Our Dark Cornish at 12 weeks last year.
You'll notice that pastured chickens actually eat more feed to reach a certain weight than they would have eaten if they were confined.  (Side by side experiments have confirmed this.)  Although we think of\
pastured chickens as getting a lot of their nutrition from wild food,\
chickens can't digest much grass, so what you're really counting is how many bugs your birds found.  It seems to take broilers more energy to find bugs than they get from eating those bugs, thus the lower feed conversion rate on pasture.\
Although these numbers seem very disheartening, I hope they don't make you turn to supermarket chickens.  As I'll explain in a later post, I think that homesteaders can grow heritage chickens at nearly the same feed conversion rate that you'd get from Cornish Cross on pasture (and maybe even better) if we're willing to think outside the box.


A transmissible cancer is a cancer cell or cluster of cancer cells that can be transferred between individuals without the involvement of an infectious agent such as an oncovirus. The evolution of transmissible cancer has occurred naturally in other animal species, but human cancer transmission is rare. This transfer is typically between members of the same species or closely related species.

## General mechanism
Transmissible cancers require a specific combination of related circumstances to occur. These conditions involve both the host species and the tumors being transferred. These typically include low genetic diversity among individuals, an effective physical and environmental transport system, and a high enough dose of infective material. The cancers reproduce faster in larger quantities with different means of reproduction tend to be favored for transmission if host conditions are met. Transmissible cancers follow the general pattern of cancer spread, starting with the growth of primary cancer cells at tumor sites followed by invasion of surrounding tissue and subsequent spread throughout the organism. The main hurdles for surviving cells of a successful spread to a new host are histocompatibility barriers. The cancers have to bypass the self recognition system, survive the difference in nutrients and induce the correct response in the new hosts to begin the cycle anew.
Transmissible cancers behave as true parasites, relying primarily on transport systems like direct contact, environmental transport and vectors, rather than hematogenous and lymphatic carriers to spread between organisms. The amount of shedded cancer cells from initial host has to be high enough to increase survival probability. Direct contact transmissions through sexual or general contact such as in DFTD and CVTD ensures a higher potential for transmission. Population factors also play an important role. A dense population of available and uninfected potential hosts is ideal for the tumors given the complexity and difficulty of the overall process, hence its virulence and potency must be adequately controlled.


An afterimage, or after-image, is an image that continues to appear in the eyes after a period of exposure to the original image. An afterimage may be a normal phenomenon (physiological afterimage) or may be pathological (palinopsia). Illusory palinopsia may be a pathological exaggeration of physiological afterimages. Afterimages occur because photochemical activity in the retina continues even when the eyes are no longer experiencing the original stimulus.
The remainder of this article refers to physiological afterimages. A common physiological afterimage is the dim area that seems to float before one's eyes after briefly looking into a light source, such as a camera flash. Palinopsia is a common symptom of visual snow.


## Negative afterimages
Negative afterimages are generated in the retina but may be modified like other retinal signals by neural adaptation of the retinal ganglion cells that carry signals from the retina of the eye to the rest of the brain.
Normally, any image is moved over the retina by small eye movements known as microsaccades before much adaptation can occur. However, if the image is very intense and brief, or if the image is large, or if the eye remains very steady, these small movements cannot keep the image on unadapted parts of the retina.
Afterimages can be seen when moving from a bright environment to a dim one, like walking indoors on a bright snowy day. They are accompanied by neural adaptation in the occipital lobe of the brain that function similar to color balance adjustments in photography. These adaptations attempt to keep vision consistent in dynamic lighting. Viewing a uniform background while adaptation is still occurring will allow an individual to see the afterimage because localized areas of vision are still being processed by the brain using adaptations that are no longer needed.
The Young-Helmholtz trichromatic theory of color vision postulated that there were three types of photoreceptors in the eye, each sensitive to a particular range of visible light: short-wavelength cones, medium-wavelength cones, and long-wavelength cones. Trichromatic theory, however, cannot explain all afterimage phenomena. Specifically, afterimages are the complementary hue of the adapting stimulus, and trichromatic theory fails to account for this fact.
The failure of trichromatic theory to account for afterimages indicates the need for an opponent-process theory such as that articulated by Ewald Hering (1878) and further developed by Hurvich and Jameson (1957). The opponent process theory states that the human visual system interprets color information by processing signals from cones and rods in an antagonistic manner. The opponent color theory is that there are four opponent channels: red versus cyan, green vs magenta, blue versus yellow, and black versus white. Responses to one color of an opponent channel are antagonistic to those of the other color. Therefore, a green image will produce a magenta afterimage. The green color adapts the green channel, so they produce a weaker signal. Anything resulting in less green is interpreted as its paired primary color, which is magenta (an equal mixture of red and blue).


Binocular disparity refers to the difference in image location of an object seen by the left and right eyes, resulting from the eyes' horizontal separation (parallax). The mind uses binocular disparity to extract depth information from the two-dimensional retinal images in stereopsis. In computer vision, binocular disparity refers to the difference in coordinates of similar features within two stereo images.
A similar disparity can be used in rangefinding by a coincidence rangefinder to determine distance and/or altitude to a target. In astronomy, the disparity between different locations on the Earth can be used to determine various celestial parallax, and Earth's orbit can be used for stellar parallax.


## Definition
Human eyes are horizontally separated by about 50--75 mm (interpupillary distance) depending on each individual. Thus, each eye has a slightly different view of the world around. This can be easily seen when alternately closing one eye while looking at a vertical edge. The binocular disparity can be observed from apparent horizontal shift of the vertical edge between both views.
At any given moment, the line of sight of the two eyes meet at a point in space. This point in space projects to the same location (i.e. the center) on the retinae of the two eyes. Because of the different viewpoints observed by the left and right eye however, many other points in space do not fall on corresponding retinal locations. Visual binocular disparity is defined as the difference between the point of projection in the two eyes and is usually expressed in degrees as the visual angle.
The term "binocular disparity" refers to geometric measurements made external to the eye. The disparity of the images on the actual retina depends on factors internal to the eye, especially the location of the nodal points, even if the cross section of the retina is a perfect circle. Disparity on retina conforms to binocular disparity when measured as degrees, while much different if measured as distance due to the complicated structure inside eye.
Figure 1: The full black circle is the point of fixation. The blue object lies nearer to the observer. Therefore, it has a "near" disparity dn. Objects lying more far away (green) correspondingly have a "far" disparity df. Binocular disparity is the angle between two lines of projection . One of which is the real projection from the object to the actual point of projection. The other one is the imaginary projection running through the nodal point of the fixation point.
In computer vision, binocular disparity is calculated from stereo images taken from a set of stereo cameras. The variable distance between these cameras, called the baseline, can affect the disparity of a specific point on their respective image plane. As the baseline increases, the disparity increases due to the greater angle needed to align the sight on the point. However, in computer vision, binocular disparity is referenced as coordinate differences of the point between the right and left images instead of a visual angle. The units are usually measured in pixels.


## Tricking neurons with 2D images
Brain cells (neurons) in a part of the brain responsible for processing visual information coming from the retinae (primary visual cortex) can detect the existence of disparity in their input from the eyes. Specifically, these neurons will be active, if an object with "their" special disparity lies within the part of the visual field to which they have access (receptive field).
Researchers investigating precise properties of these neurons with respect to disparity present visual stimuli with different disparities to the cells and look whether they are active or not. One possibility to present stimuli with different disparities is to place objects in varying depth in front of the eyes. However, the drawback to this method may not be precise enough for objects placed further away as they possess smaller disparities while objects closer will have greater disparities. Instead, neuroscientists use an alternate method as schematised in Figure 2.
Figure 2: The disparity of an object with different depth than the fixation point can alternatively be produced by presenting an image of the object to one eye and a laterally shifted version of the same image to the other eye. The full black circle is the point of fixation. Objects in varying depths are placed along the line of fixation of the left eye. The same disparity produced from a shift in depth of an object (filled coloured circles) can also be produced by laterally shifting the object in constant depth in the picture one eye sees (black circles with coloured margin). Note that for near disparities the lateral shift has to be larger to correspond to the same depth compared with far disparities. This is what neuroscientists usually do with random dot stimuli to study disparity selectivity of neurons since the lateral distance required to test disparities is less than the distances required using depth tests. This principle has also been applied in autostereogram illusions.


Transparency Market Research Report Add "Geothermal Energy Market - Global Industry Analysis, Size, Share, Growth, Trends And Forecast, 2012 - 2018" to its database.
Albany, NY -- (SBWIRE) -- 06/10/2013 -- Geothermal energy is a type of heat energy that is produced in the earth's core. This energy is utilized in a wide range of applications from power stations to simple pumping systems. Geothermal energy is considered as a renewable source of energy since the water which is captured in the form of heat while extracting geothermal energy is continuously replenished by rainfall and again the heat generated from it can be used. A major concentration of geothermal energy on the planet is in the area bordering the Pacific Ocean and is called the Ring of Fire.
Browse Report : http://www.transparencymarketresearch.com/geothermal-energy-market.html
There are two types of geothermal systems -- hydrothermal and hot rock or enhanced geothermal systems. The most important type of geothermal energy is hydrothermal energy which is most widely used for generating electricity.
Increasing concerns regarding energy security, economic growth in developing markets, rising costs of fossil fuels, several incentives given by European countries, new technologies like binary technology, which can use even moderate temperatures to generate a decent amount of electricity, are some of the major drivers that are significantly fuelling this market.
The major impediments which this industry faces include initial financing of large scale projects, resource development risks like failure of drilling wells and insufficient productivity, lack of skilled labor to work on the projects, issues related to drilling rigs and market and network issues like proximity to the market and network capital costs. Also, there are some environmental problems in producing geothermal energy like release of hydrogen sulfide and disposal of toxic geothermal fluids while extraction.
Challenges to this industry are carrying out efficient programs for land leasing where reserves of geothermal energy are located, better drilling assistance in terms of accurate positioning of the site and its viability, and significant financial support needed to establish the plants at the desired locations.
The United States of America has the largest amount of installed capacity and is succeeded by Philippines, Indonesia, Mexico, and Italy. Currently there are over 150 projects under development in the U.S.. On the other hand, China is the largest direct user of geothermal energy followed by the United States, Sweden, and Turkey.


Often I've wondered about my computer standby mode power consumption. How much electricity does my computer use when it is in sleep mode? Since my computer (a tower desktop with two LCD monitors) is several years old it takes a while to boot up so I like to leave it in standby mode when I can.
To test the standby mode power consumption of my computer I got a P3 International Kill-a-Watt meter for about \$21 online to use as a PC power consumption monitor. The Kill-a-Watt power meter plugs into the wall and then the appliance plugs into the meter. It has a has an LCD screen to tell you how much electricity was consumed in that time period.
Here's what I found (cost per KWH in Maryland is 10.28 cents):
State
Time
Power Usage (KWH)
KWH per hr
KWH per day
Cost per day
Off but plugged in
8hrs
0.08
0.01
0.24
2.5
Sleep mode
14hrs 23min
0.16
0.011
0.27
2.8
Regular usage
6hrs 40 min
1.15
0.173
4.15
42.7

### In Summary ...
The standby mode power consumption is just a bit more than leaving the computer plugged in but off. So I can use standby mode without any significant additional cost.
While I'm away for more than 8 hours it makes sense to turn the computer off at the power strip. At this point no electricity is being used by any of the devices on the power strip. I usually do this when I am done using the computer in the evening or plan to be away for a while.
Note - if you have power supplies (the black boxes you plug into a power strip or the wall) plugged directly into the wall they will be using electricity (feel them, they'll be warm). The power strip allows you to turn them off completely. This goes for stereo systems, power tools, etc.
Search the Web for a Kill-A-Watt Power Meter:


The Real Driving Emissions (RDE) test measures the pollutants, such as NOx, emitted by cars while driven on the road. RDE does not replace the WLTP laboratory test, but complements it. RDE ensures that cars deliver low emissions over on-road conditions. Europe is the first region in the world to introduce such on-road testing, marking a major leap in the testing of car emissions.
Under RDE, a car is driven on public roads and over a wide range of different conditions. Specific equipment installed on the vehicle collects data to verify that legislative caps for pollutants such as NOx are not exceeded.
Conditions include:
- Low and high altitudes
- Year-round temperatures
- Additional vehicle payload
- Up- and down-hill driving
- Urban roads (low speed)
- Rural roads (medium speed)
- Motorways (high speed)
To measure pollutant emissions as the vehicle is being driven on the roads, cars are fitted with Portable Emission Measuring Systems (PEMS) that provide a complete real-time monitoring of the key pollutants emitted by the vehicle (ie NOx).
The PEMS used for regulated emissions are complex pieces of equipment that integrate advanced gas analysers, exhaust mass flow meters, weather station, Global Positioning System (GPS) and a connection to the vehicle networks.
All parties -- including approval authorities -- must learn the proper use of PEMS systems. There is no 'standard' PEMS equipment and equipment manufactured by different suppliers will always deliver slightly different results. The collected data is analysed to check that the RDE trip boundary conditions were achieved and that the emissions were within acceptable levels.
- RDE step 1 (with a NOx conformity factor of 2.1) applies since 1 September 2017 for new car types. It will apply to all types as from September 2019.
- RDE step 2 (with a NOx conformity factor of 1.0 plus an error margin of 0.5) will apply in January 2020 for new types and then from January 2021 for all types.


Flow in positive psychology, also known colloquially as being in the zone or locked in, is the mental state in which a person performing some activity is fully immersed in a feeling of energized focus, full involvement, and enjoyment in the process of the activity. In essence, flow is characterized by the complete absorption in what one does, and a resulting transformation in one's sense of time. Flow is the melting together of action and consciousness; the state of finding a balance between a skill and how challenging that task is. It requires a high level of concentration. Flow is used as a coping skill for stress and anxiety when productively pursuing a form of leisure that matches one's skill set.
First presented in the 1975 book Beyond Boredom and Anxiety by the Hungarian-American psychologist Mihály Csíkszentmihályi, the concept has been widely referred to across a variety of fields (and is particularly well recognized in occupational therapy).
The flow state shares many characteristics with hyperfocus. However, hyperfocus is not always described in a positive light. Some examples include spending "too much" time playing video games or becoming pleasurably absorbed by one aspect of an assignment or task to the detriment of the overall assignment. In some cases, hyperfocus can "capture" a person, perhaps causing them to appear unfocused or to start several projects, but complete few. Hyperfocus is often mentioned "in the context of autism, schizophrenia, and attention deficit hyperactivity disorder -- conditions that have consequences on attentional abilities."
Flow is an individual experience and the idea behind flow originated from the sports-psychology theory about an Individual Zone of Optimal Functioning. The individuality of the concept of flow suggests that each person has their subjective area of flow, where they would function best given the situation. One is most likely to experience flow at moderate levels of psychological arousal, as one is unlikely to be overwhelmed, but not understimulated to the point of boredom.

## Etymology
Flow is so named because, during Csíkszentmihályi's 1975 interviews, several people described their "flow" experiences using the metaphor of a water current carrying them along:
We have called this state the flow experience, because this is the term many of the people we interviewed had used in their descriptions of how it felt to be in top form: "It was like floating," "I was carried on by the flow."


## Characteristics
### Challenges to maintaining flow
Some of the challenges to staying in flow include states of apathy, boredom, and anxiety. The state of apathy is characterized by easy challenges and low skill level requirements, resulting in a general lack of interest in the activity. Boredom is a slightly different state that occurs when challenges are few, but one's skill level exceeds those challenges causing one to seek higher challenges. A state of anxiety occurs when challenges are high enough to exceed perceived skill level, causing distress and uneasiness. These states in general prevent achieving the balance necessary for flow. Csíkszentmihályi has said, "If challenges are too low, one gets back to flow by increasing them. If challenges are too great, one can return to the flow state by learning new skills."


In psychology and neuroscience, memory span is the longest list of items that a person can repeat back in correct order immediately after presentation on 50% of all trials. Items may include words, numbers, or letters. The task is known as digit span when numbers are used. Memory span is a common measure of working memory and short-term memory. It is also a component of cognitive ability tests such as the Wechsler Adult Intelligence Scale (WAIS). Backward memory span is a more challenging variation which involves recalling items in reverse order.

## As a functional aspect
Functionally, memory span is used to measure the number of discrete units over which the individual can successively distribute his attention and still organize them into a working unit. To generalize, it refers to the ability of an individual to reproduce immediately, after one presentation, a series of discrete stimuli in their original order.
Experiments in memory span have found that the more familiar a person is with the type of subject matter presented to them, the more they will remember it in a novel setting. For example, a person will better remember a sequence in their first-language than their second-language; a person will also remember a sequence of words better than they would a sequence of nonsense syllables.
According to a theory by Alan Baddeley and Graham Hitch, working memory is under the influence of three key mechanisms: the visuospatial sketchpad, the central executive, and the phonological loop. A mechanism called the episodic buffer was later added to the model. The phonological loop is the mechanism that facilitates learning and memory by storing information (in the articulatory loop) and refreshing or rehearsing it in memory (in the acoustic store). The phonological similarity effect is when items in a list have similar features (e.g. similar sound), they are more difficult to remember. Likewise, the more different the items in a list are, the easier it is to recall them. Memory span tasks since the formulation of Baddeley and Hitch's theory have been helpful as support for the phonological loop as part of the working memory.


In economics, a complementary good is a good whose appeal increases with the popularity of its complement. Technically, it displays a negative cross elasticity of demand and that demand for it increases when the price of another good decreases. If
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When two goods are complements, they experience joint demand - the demand of one good is linked to the demand for another good. Therefore, if a higher quantity is demanded of one good, a higher quantity will also be demanded of the other, and vice versa. For example, the demand for razor blades may depend on the number of razors in use; this is why razors have sometimes been sold as loss leaders, to increase demand for the associated blades. Another example is that sometimes a toothbrush is packaged free with toothpaste. The toothbrush is a complement to the toothpaste; the cost of producing a toothbrush may be higher than toothpaste, but its sales depends on the demand of toothpaste.
All non-complementary goods can be considered substitutes. If
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Complementarity may be driven by psychological processes in which the consumption of one good (e.g., cola) stimulates demand for its complements (e.g., a cheeseburger). Consumption of a food or beverage activates a goal to consume its complements: foods that consumers believe would taste better together. Drinking cola increases consumers' willingness to pay for a cheeseburger. This effect appears to be contingent on consumer perceptions of these relationships rather than their sensory properties.


## Examples
An example of this would be the demand for cars and petrol. The supply and demand for cars is represented by the figure, with the initial demand
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. Other examples include automobiles and fuel, mobile phones and cellular service, printer and cartridge, among others.


In passive solar building design, windows, walls, and floors are made to collect, store, reflect, and distribute solar energy, in the form of heat in the winter and reject solar heat in the summer. This is called passive solar design because, unlike active solar heating systems, it does not involve the use of mechanical and electrical devices.
The key to designing a passive solar building is to best take advantage of the local climate performing an accurate site analysis. Elements to be considered include window placement and size, and glazing type, thermal insulation, thermal mass, and shading. Passive solar design techniques can be applied most easily to new buildings, but existing buildings can be adapted or "retrofitted".

## Passive energy gain
Passive solar technologies use sunlight without active mechanical systems (as contrasted to active solar, which uses thermal collectors). Such technologies convert sunlight into usable heat (in water, air, and thermal mass), cause air-movement for ventilating, or future use, with little use of other energy sources. A common example is a solarium on the equator-side of a building. Passive cooling is the use of similar design principles to reduce summer cooling requirements.
Some passive systems use a small amount of conventional energy to control dampers, shutters, night insulation, and other devices that enhance solar energy collection, storage, and use, and reduce undesirable heat transfer.
Passive solar technologies include direct and indirect solar gain for space heating, solar water heating systems based on the thermosiphon, use of thermal mass and phase-change materials for slowing indoor air temperature swings, solar cookers, the solar chimney for enhancing natural ventilation, and earth sheltering.
More widely, solar technologies include the solar furnace, but this typically requires some external energy for aligning their concentrating mirrors or receivers, and historically have not proven to be practical or cost effective for widespread use. 'Low-grade' energy needs, such as space and water heating, have proven over time to be better applications for passive use of solar energy.


## As a science
Specific attention is divided into: the site, location and solar orientation of the building, local sun path, the prevailing level of insolation (latitude/sunshine/clouds/precipitation), design and construction quality/materials, placement/size/type of windows and walls, and incorporation of solar-energy-storing thermal mass with heat capacity.While these considerations may be directed toward any building, achieving an ideal optimized cost/performance solution requires careful, holistic, system integration engineering of these scientific principles. Modern refinements through computer modeling (such as the comprehensive U.S. Department of Energy "Energy Plus" building energy simulation software), and application of decades of lessons learned (since the 1970s energy crisis) can achieve significant energy savings and reduction of environmental damage, without sacrificing functionality or aesthetics. In fact, passive-solar design features such as a greenhouse/sunroom/solarium can greatly enhance the livability, daylight, views, and value of a home, at a low cost per unit of space.
Much has been learned about passive solar building design since the 1970s energy crisis. Many unscientific, intuition-based expensive construction experiments have attempted and failed to achieve zero energy -- the total elimination of heating-and-cooling energy bills.
Passive solar building construction may not be difficult or expensive (using off-the-shelf existing materials and technology), but the scientific passive solar building design is a non-trivial engineering effort that requires significant study of previous counter-intuitive lessons learned, and time to enter, evaluate, and iteratively refine the simulation input and output.
One of the most useful post-construction evaluation tools has been the use of thermography using digital thermal imaging cameras for a formal quantitative scientific energy audit. Thermal imaging can be used to document areas of poor thermal performance such as the negative thermal impact of roof-angled glass or a skylight on a cold winter night or hot summer day.
The scientific lessons learned over the last three decades have been captured in sophisticated comprehensive building energy simulation computer software systems (like U.S. DOE Energy Plus).
Scientific passive solar building design with quantitative cost benefit product optimization is not easy for a novice. The level of complexity has resulted in ongoing bad-architecture, and many intuition-based, unscientific construction experiments that disappoint their designers and waste a significant portion of their construction budget on inappropriate ideas.
The economic motivation for scientific design and engineering is significant. If it had been applied comprehensively to new building construction beginning in 1980 (based on 1970s lessons learned), The United States could be saving over \$250,000,000 per year on expensive energy and related pollution today.
Since 1979, Passive Solar Building Design has been a critical element of achieving zero energy by educational institution experiments, and governments around the world, including the U.S. Department of Energy, and the energy research scientists that they have supported for decades. The cost effective proof of concept was established decades ago, but cultural change in architecture, the construction trades, and building-owner decision making has been very slow and difficult.
The new subjects such as architectural science and architectural technology are being added to some schools of architecture, with a future goal of teaching the above scientific and energy-engineering principles.


## The solar path in passive design
The 47-degree difference in the altitude of the sun at solar noon between winter and summer forms the basis of passive solar design. This information is combined with local climatic data (degree day) heating and cooling requirements to determine at what time of the year solar gain will be beneficial for thermal comfort, and when it should be blocked with shading. By strategic placement of items such as glazing and shading devices, the percentage of solar gain entering a building can be controlled throughout the year.
One passive solar sun path design problem is that although the sun is in the same relative position six weeks before, and six weeks after, the solstice, due to "thermal lag" from the thermal mass of the Earth, the temperature and solar gain requirements are quite different before and after the summer or winter solstice. Movable shutters, shades, shade screens, or window quilts can accommodate day-to-day and hour-to-hour solar gain and insulation requirements.
Careful arrangement of rooms completes the passive solar design. A common recommendation for residential dwellings is to place living areas facing solar noon and sleeping quarters on the opposite side. A heliodon is a traditional movable light device used by architects and designers to help model sun path effects. In modern times, 3D computer graphics can visually simulate this data, and calculate performance predictions.

## Passive solar heat transfer principles
Personal thermal comfort is a function of personal health factors (medical, psychological, sociological and situational), ambient air temperature, mean radiant temperature, air movement (wind chill, turbulence) and relative humidity (affecting human evaporative cooling). Heat transfer in buildings occurs through convection, conduction, and thermal radiation through roof, walls, floor and windows.


## Passive solar heat transfer principles
### Convective heat transfer
Convective heat transfer can be beneficial or detrimental. Uncontrolled air infiltration from poor weatherization / weatherstripping / draft-proofing can contribute up to 40% of heat loss during winter; however, strategic placement of operable windows or vents can enhance convection, cross-ventilation, and summer cooling when the outside air is of a comfortable temperature and relative humidity. Filtered energy recovery ventilation systems may be useful to eliminate undesirable humidity, dust, pollen, and microorganisms in unfiltered ventilation air.
Natural convection causing rising warm air and falling cooler air can result in an uneven stratification of heat. This may cause uncomfortable variations in temperature in the upper and lower conditioned space, serve as a method of venting hot air, or be designed in as a natural-convection air-flow loop for passive solar heat distribution and temperature equalization. Natural human cooling by perspiration and evaporation may be facilitated through natural or forced convective air movement by fans, but ceiling fans can disturb the stratified insulating air layers at the top of a room, and accelerate heat transfer from a hot attic, or through nearby windows. In addition, high relative humidity inhibits evaporative cooling by humans.


## Passive solar heat transfer principles
### Radiative heat transfer
The main source of heat transfer is radiant energy, and the primary source is the sun. Solar radiation occurs predominantly through the roof and windows (but also through walls). Thermal radiation moves from a warmer surface to a cooler one. Roofs receive the majority of the solar radiation delivered to a house. A cool roof, or green roof in addition to a radiant barrier can help prevent your attic from becoming hotter than the peak summer outdoor air temperature (see albedo, absorptivity, emissivity, and reflectivity).
Windows are a ready and predictable site for thermal radiation.
Energy from radiation can move into a window in the day time, and out of the same window at night. Radiation uses photons to transmit electromagnetic waves through a vacuum, or translucent medium. Solar heat gain can be significant even on cold clear days. Solar heat gain through windows can be reduced by insulated glazing, shading, and orientation. Windows are particularly difficult to insulate compared to roof and walls. Convective heat transfer through and around window coverings also degrade its insulation properties. When shading windows, external shading is more effective at reducing heat gain than internal window coverings.
Western and eastern sun can provide warmth and lighting, but are vulnerable to overheating in summer if not shaded. In contrast, the low midday sun readily admits light and warmth during the winter, but can be easily shaded with appropriate length overhangs or angled louvres during summer and leaf bearing summer shade trees which shed their leaves in the fall. The amount of radiant heat received is related to the location latitude, altitude, cloud cover, and seasonal / hourly angle of incidence (see Sun path and Lambert's cosine law).
Another passive solar design principle is that thermal energy can be stored in certain building materials and released again when heat gain eases to stabilize diurnal (day/night) temperature variations. The complex interaction of thermodynamic principles can be counterintuitive for first-time designers. Precise computer modeling can help avoid costly construction experiments.

## Site specific considerations during design
Latitude, sun path, and insolation (sunshine)
Seasonal variations in solar gain e.g. cooling or heating degree days, solar insolation, humidity
Diurnal variations in temperature
Micro-climate details related to breezes, humidity, vegetation and land contour
Obstructions / Over-shadowing -- to solar gain or local cross-winds


Expanded polyethylene (EPE foam) refers to foams made from polyethylene. Typically it is made from expanded pellets ('EPE bead') made with use of a blowing agent, followed by expansion into a mold in a steam chest - the process is similar to that used to make expanded polystyrene foam.

## Properties
EPE foams are low density, semi-rigid, closed cell foam that are generally somewhere in stiffness/compliance between Expanded polystyrene and Polyurethane. Production of EPE foams is similar to that of expanded polystyrene, but starting with PE beads. Typical densities are 29 to 120 kg/m3 (49 to 202 lb/cu yd) with the lower figure being common. Densities as low as 14 kg/m3 (24 lb/cu yd) can be produced.
Base polymer for EPE foams range from Low-density polyethylene (LDPE) to High-density polyethylene (HDPE).

### Co-polymers
Expanded polyethylene copolymers (EPC) are also known - such as 50:50 (weight) materials with polystyrene. Though other properties are intermediate between the two bases, toughness for the copolymer exceeds either, with good tensile and puncture resistance. It is particularly applicable for re-usable products.

## Production
EPE foams were first manufactured in the 1970s.
Production of the PE beads is usually by extrusion, followed by chopping, producing a 'pellet'. Autoclave expansion is the most common route the bead foam. Butane or pentane is often used as a blowing agent (before 1992 CFCs may have been used). Depending on the specific process uses the beads may be cross-linked either by electron beam irradiation (see Electron beam processing), or by the addition of a chemical agent such as dicumyl peroxide.
An alternate route (JSP Process) to the beads uses carbon dioxide as a blowing agent which is impregnated into the pellets in an autoclave at a temperature close to the plastic's crystalline melting point. The pellets are foamed by "flashing" into the (lower pressure) atmosphere to expand.
Finally molding is done by steam chest compression molding; usually the low pressure variant of the process is used, though the high pressure variant may be used for HDPE based EPE foams.