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Reaction
As described by the third of Newton's laws of motion of classical mechanics, all forces occur in pairs such that if one object exerts a force on another object, then the second object exerts an equal and opposite reaction force on the first. The third law is also more generally stated as: "To every action there is always opposed an equal reaction: or the mutual actions of two bodies upon each other are always equal, and directed to contrary parts." The attribution of which of the two forces is the action and which is the reaction is arbitrary. Either of the two can be considered the action, while the other is its associated reaction.
  • 2.4K
  • 30 Oct 2022
Topic Review
California Proposition 71 (2004)
Proposition 71 of 2004 (or the California Stem Cell Research and Cures Act) is a law enacted by California voters to support stem cell research in the state. It was proposed by means of the initiative process and approved in the 2004 state elections on November 2. The Act amended both the Constitution of California and the Health and Safety Code. The Act makes conducting stem cell research a state constitutional right. It authorizes the sale of general obligation bonds to allocate three billion dollars over a period of ten years to stem cell research and research facilities. Although the funds could be used to finance all kinds of stem cell research, it gives priority to human embryonic stem cell research. Proposition 71 created the California Institute for Regenerative Medicine (CIRM), which is in charge of making "grants and loans for stem cell research, for research facilities, and for other vital research opportunities to realize therapies" as well as establishing "the appropriate regulatory standards of oversight bodies for research and facilities development". The Act also establishes a governing body called the Independent Citizen’s Oversight Committee (ICOC) to oversee CIRM. Proposition 71 is unique in at least three ways. Firstly, it uses general obligation bonds, which are usually used to finance brick-and-mortar projects such as bridges or hospitals, to fund scientific research. Secondly, by funding scientific research on such a large scale, California is taking on a role that is typically fulfilled by the U.S. federal government. Thirdly, Proposition 71 establishes the state constitutional right to conduct stem cell research. The initiative also represents a unique instance where the public directly decided to fund scientific research.
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  • 30 Oct 2022
Topic Review
Generalizing the Local Average Treatment Effect
The local average treatment effect (LATE), also known as the complier average causal effect (CACE), refers to the treatment effect among compliers. The LATE may not be of the same value as the average treatment effect (ATE), so extrapolating the LATE directly should be done cautiously. In addition, the LATE retrieved from an experiment may not immediately be externally valid, especially when there is a case for treatment effect heterogeneity (i.e. the treatment effect varies across individuals).  However, generalizing the LATE through reweighting can be attempted, given certain key assumptions.
  • 4.3K
  • 30 Oct 2022
Topic Review
Leadership in Energy and Environmental Design
Leadership in Energy and Environmental Design (LEED) is a green building certification program used worldwide. Developed by the non-profit U.S. Green Building Council (USGBC), it includes a set of rating systems for the design, construction, operation, and maintenance of green buildings, homes, and neighborhoods, which aims to help building owners and operators be environmentally responsible and use resources efficiently. By 2015, there were over 80,000 LEED-certified buildings and over 100,000 LEED-accredited professionals. Most LEED-certified buildings are located in major U.S. metropolises. LEED Canada has developed a separate rating system for the regulations and climate of that country. Some U.S. federal agencies, state and local governments require or reward LEED certification. This can include tax credits, zoning allowances, reduced fees, and expedited permitting. Studies have found that for-rent LEED office spaces generally have higher rents and occupancy rates and lower capitalization rates. LEED is a design tool rather than a performance-measurement tool and focuses on energy modeling rather than actual energy consumption. It lacks climate specificity, and has been criticized for a point system that can encourage inappropriate design choices and make energy conservation the weakest part of the evaluation. It has also been criticized for the phenomenon of "LEED brain" in which the public relations value of LEED certification drives the development of buildings.
  • 2.6K
  • 30 Oct 2022
Topic Review
Sick Leave
Sick leave (or paid sick days or sick pay) is time off from work that workers can use to stay home to address their health and safety needs without losing pay. Paid sick leave is a statutory requirement in many nations. Most European, many Latin American, a few African and a few Asian countries have legal requirements for paid sick leave. The Book of Leviticus prescribed (7) days of medical isolation for a skin condition in chapter 13. Already in 1500 BCE, at least some of the workers who built the tombs of Egyptian pharaohs received paid sick leave as well as state-supported health care. In nations without laws mandating paid sick leave, some employers choose to offer it. Those that do offer sick leave do so as a matter of workplace policy or because it is in some or all of the employees' employment contracts or required by a collective bargaining agreement. Currently, nine US states (Arizona, California, Connecticut, Maryland, Massachusetts, Oregon, Rhode Island, Vermont, Washington); 23 US cities; and two US counties (Montgomery County, MD and San Francisco County, CA) have laws mandating paid sick leave. Currently, there are additional US city, county and state jurisdictions with proposed legislation to enact paid sick leave.
  • 2.6K
  • 30 Oct 2022
Topic Review
MicrOmega-IR
MicrOmega-IR is an infrared hyperspectral microscope that is part of the science payload on board the European Rosalind Franklin rover, tasked to search for biosignatures on Mars. The rover is planned to land on Mars in the mid- or late 2020s. MicrOmega-IR will analyse in situ the powder material derived from crushed samples collected by the rover's core drill.
  • 544
  • 30 Oct 2022
Topic Review
Helmy Eltoukhy
Helmy Eltoukhy is an American scientist and entrepreneur, best known for his contributions to genomics, semiconductor DNA sequencing, and personalized medicine. The co-founder of startups Avantome and Guardant Health, Eltoukhy was named to Time (magazine) ’s inaugural 50 Most Influential People in Healthcare (2018) and Fortune’s 40 under 40 (2017). Acquired by Illumina in 2008, Avantome was founded to develop and commercialize semiconductor-based DNA sequencing, during the race for the $1,000 genome. Guardant Health was founded to pioneer non-invasive liquid biopsy approaches for cancer diagnosis, monitoring, personalized medicine treatment, and research.
  • 1.4K
  • 28 Oct 2022
Topic Review
Armoured Vehicle Royal Engineers
Armoured Vehicle Royal Engineers (AVRE), also known as Assault Vehicle Royal Engineers is the title given to a series of armoured military engineering vehicles operated by the Royal Engineers (RE) for the purpose of protecting engineers during frontline battlefield operations. In protecting engineers, the vehicles also became a mobile platform for a variety of engineering purposes, mounting large calibre weapons for demolition, carrying engineering stores, mine clearance explosives, a variety of deployable roadways, and modified engineering bridges for gaps that the related Armoured Ramp Carrier ("ARK") vehicles could not overcome.
  • 3.2K
  • 28 Oct 2022
Topic Review
Power (Statistics)
The power of a binary hypothesis test is the probability that the test rejects the null hypothesis (H0) when a specific alternative hypothesis (H1) is true. The statistical power ranges from 0 to 1, and as statistical power increases, the probability of making a type II error (wrongly failing to reject the null hypothesis) decreases. For a type II error probability of β, the corresponding statistical power is 1 − β. For example, if experiment 1 has a statistical power of 0.7, and experiment 2 has a statistical power of 0.95, then there is a stronger probability that experiment 1 had a type II error than experiment 2, and experiment 2 is more reliable than experiment 1 due to the reduction in probability of a type II error. It can be equivalently thought of as the probability of accepting the alternative hypothesis (H1) when it is true—that is, the ability of a test to detect a specific effect, if that specific effect actually exists. That is, If [math]\displaystyle{ H_1 }[/math] is not an equality but rather simply the negation of [math]\displaystyle{ H_0 }[/math] (so for example with [math]\displaystyle{ H_0:\mu=0 }[/math] for some unobserved population parameter [math]\displaystyle{ \mu, }[/math] we have simply [math]\displaystyle{ H_1:\mu\ne 0 }[/math]) then power cannot be calculated unless probabilities are known for all possible values of the parameter that violate the null hypothesis. Thus one generally refers to a test's power against a specific alternative hypothesis. As the power increases, there is a decreasing probability of a type II error, also referred to as the false negative rate (β) since the power is equal to 1 − β. A similar concept is the type I error probability, also referred to as the "false positive rate" or the level of a test under the null hypothesis. Power analysis can be used to calculate the minimum sample size required so that one can be reasonably likely to detect an effect of a given size. For example: "how many times do I need to toss a coin to conclude it is rigged by a certain amount?" Power analysis can also be used to calculate the minimum effect size that is likely to be detected in a study using a given sample size. In addition, the concept of power is used to make comparisons between different statistical testing procedures: for example, between a parametric test and a nonparametric test of the same hypothesis. In the context of binary classification, the power of a test is called its statistical sensitivity, its true positive rate, or its probability of detection.
  • 614
  • 28 Oct 2022
Topic Review
Public Health Genomics
Public health genomics is the use of genomics information to benefit public health. This is visualized as more effective preventive care and disease treatments with better specificity, tailored to the genetic makeup of each patient. According to the Centers for Disease Control and Prevention (U.S.), Public Health genomics is an emerging field of study that assesses the impact of genes and their interaction with behavior, diet and the environment on the population's health. This field of public health genomics is less than a decade old. A number of think tanks, universities, and governments (including the U.S., UK, and Australia) have started public health genomics projects. Research on the human genome is generating new knowledge that is changing public health programs and policies. Advances in genomic sciences are increasingly being used to improve health, prevent disease, educate and train the public health workforce, other healthcare providers, and citizens.
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