5,190 Matching Annotations
  1. Feb 2022
    1. Reynolds number

      A ratio of the internal forces to the viscous forces in a fluid. A low Reynolds number indicates stronger viscous force and smoother (laminar) flow, whereas a high Reynolds number indicates greater internal forces and irregular (turbulent) flow.

    1. organic field-effect transistors

      A three-terminal active organic semiconductor device where the output current is controlled by an electric field generated by the input voltage. These are compact and have lower power consumption.

    1. arthropods

      A classification of the animal kingdom that encompasses organisms that have an exoskeleton, a segmented body, and jointed appendages (i.e. insects, crustaceans, arachnids, centipedes).

  2. Jan 2022
    1. reverse transcription quantitative real-time fluorescence polymerase chain reaction (qRT-PCR)

      Reverse transcription quantitative real-time fluorescence polymerase chain reaction, or qRT-PCR, is a widely used molecular technique to measure RNA levels.

      RNA is first reverse transcribed into complimentary DNA. This complimentary DNA is then used as a template for a fluorescence-tagged amplification reaction to calculate the relative amount of a specific starting transcript.

      The transcript levels are compared between genes of interest, which are all compared to a "housekeeping gene" or a transcript that has the same levels of expression across conditions. This comparison standardizes the levels of overall transcription across samples.

      Thermo Fisher provides an extensive introduction to gene expression measuring technologies here: https://www.thermofisher.com/us/en/home/life-science/pcr/real-time-pcr/real-time-pcr-learning-center/gene-expression-analysis-real-time-pcr-information/introduction-gene-expression.html

  3. Dec 2021
    1. PeVN

      The periventricular nucleus is a thin sheet of neurons located in the hypothalamus. For the purpose of this paper, PeVN can be defined as the part of the hypothalamus that is a major source of dopamine and somatostatin expression.

    2. PaVN

      The paraventricular nucleus is a region of the hypothalamus, considered to be the body's most important autonomic control center. The neurons of the PaVN are involved in controlling stress, metabolism, growth, reproduction, immune, gastrointestinal, renal, and cardiovascular functions. For the purpose of this paper, PaVN can be defined as the part of the hypothalamus that is a major source of dopamine and somatostatin expression.

    1. dynamical variability

      Dynamical variability refers to naturally occurring changes in the climate from year to year.

      Halogen-induced changes become more apparent when naturally occurring changes are removed from the analysis.

    2. halocarbons

      Halocarbons are chemicals that contain bonds between carbon and halogen atoms.

      Halogens are a group of elements that includes fluorine, chlorine, bromine, iodine, astatine, and tennessine.

      Halocarbons are highly reactive in the Earth's atmosphere and lead to ozone depletion.

    3. anthropogenic

      Anthropogenic means caused by human activity.

      In this context, humans released chemicals into the atmosphere, and these chemicals produced the hole in the ozone layer.

    4. mid-latitudes

      Latitude is the coordinate that specifies the north-south location on the surface of the Earth and ranges from 0 degrees at the equator to 90 degrees at the North and South Poles.

      Mid(or middle)-latitudes are approximately between 30 degrees and 60 degrees.

    5. total integrated column amount

      The integrated column is a way to quantify how much of a particular gas is found in the Earth's atmosphere.

      For a vertical path, or column, that extends through the atmosphere, the number of gas molecules is measured at each point along the path. Then, the sum total is calculated for the entire path.

      In this case, it is used to measure the amount of ozone in the atmosphere.

    6. ozone

      Ozone is a gaseous molecule composed of 3 oxygen atoms with the chemical formula O\(_{3}\).

      Here, the authors are referring to the layer of ozone in the Earth's atmosphere that filters harmful ultraviolet radiation from the sun.

    1. Paleoclimatic

      Paleoclimatology is the study of climate before direct measurements were taken. Analysis of samples from rock, ice, and trees can allow scientists to reconstruct climate patterns from hundreds to thousands of years ago.

    2. correlation coefficient

      The correlation coefficient is a measure of how closely the variation in one quantity is related to the variation in another quantity. This value ranges from 0 to 1, with 0 indicating no correlation and 1 indicating perfect correlation.

    3. Mount Agung

      Mount Agung is an active volcano in Bali, Indonesia. Its eruption in 1963 sent debris 10 km into the air and killed over 1,000 people. The volcano experienced several smaller eruptions between 2017 and 2019.

    4. optical thickness

      Optical thickness, or optical depth, is a measure of how much light can be transmitted through a material. The higher the optical thickness, the less light will make it through the substance.

    5. thermocline

      The thermocline is the horizontal layer in a body of water where the change in temperature with depth is greater than the layers above or below. Most sunlight is absorbed by the ocean above the thermocline, and this is also where most of the turbulent mixing by waves occurs.

    6. Wisconsin ice age

      The Wisconsin ice age, also known as the Wisconsin glaciation, was a period of colder temperatures and glacier advance in North America. This glaciation occurred between 75,000 and 11,000 years ago.

    7. moist adiabatic limiting lapse rate

      The moist adiabatic lapse rate is the rate at which the temperature of a moist air parcel changes as it rises adiabatically (zero heat transfer).

      Unlike the dry adiabatic lapse rate, the moist rate depends strongly on temperature. This is because cold air can hold less water than warm air, so as the parcel rises, water begins to condense and release heat to the air around it. This means that the moist rate is generally lower than the dry rate.

    8. model sensitivity

      The model sensitivity refers to how much the output changes for a given change in input. Here, we are interested in the amount of warming predicted for a doubling in carbon dioxide concentration.

    9. Mie scattering theory

      Mie scattering theory is a model of light scattering that assumes that the particles scattering the light are spherical. This theory applies best when the particles have similar diameter to the wavelength of the incident light. Scattering in the lower 4,500 m of the atmosphere is well described by these equations.

    10. flux divergences

      The divergence of a flux is a measure of how much some process flows in or out through a surface. If something is a source of the flow, its divergence will be positive, and if it is a sink, its divergence will be negative.

    11. heat capacity

      Heat capacity is the energy it takes to raise the temperature of a substance by a given amount (e.g., 1 degree). It usually has units of joules per mole per kelvin.

    12. convectively unstable

      Convective stability is the ability of a mass of air to resist vertical motion (convection). When an atmosphere is unstable, air masses have larger vertical movements. In the extreme, this can create turbulence and sometimes severe weather.

    13. latent heat

      Latent heat is heat transfer that is not accompanied by a change in temperature. This occurs when water condenses (releasing heat) or evaporates (absorbing heat).

      This is the mechanism by which sweat cools our bodies, even though the temperature of the water remains the same before and immediately after evaporation.

    14. dry adiabatic value

      An adiabatic process is one that occurs with no heat transfer between a system and its surroundings.

      As an air mass rises or falls adiabatically, its temperature changes with altitude due to the change in pressure. The rate of this change for a dry air mass is the dry adiabatic lapse rate.

    15. troposphere

      The troposphere is the lowest layer of Earth's atmosphere, extending from the surface to 13 km above ground on average. This layer contains most of the mass of the atmosphere and is where most weather phenomena take place.

    16. flux-weighted

      Radiant flux refers to light emitted through a surface and has units of watts per square meter. A spherical object emitting radiation will have a radiant flux that gets smaller as one gets further from the source's center.

    17. Stefan-Boltzmann constant

      The Stefan-Boltzmann constant is a number used in the Stefan-Boltzmann law. This equation relates an object's temperature to the wavelengths of light it emits.

      The constant's value is about 5.67 W / (m^2 K^4).

    18. albedo

      Albedo is the proportion of incoming light that is reflected back into space. This reflected light is in the visible and ultraviolet range, rather than the light emitted by Earth itself which is in the infrared.

      Clouds and snow are responsible for much of the planet's albedo.

    19. greenhouse effect

      The greenhouse effect is the warming of Earth's surface due to the behavior of certain atmospheric gases, called greenhouse gases.

      Greenhouse gases absorb and emit the same wavelengths of light (infrared) that are emitted by the planet's surface. This slows down the loss of heat energy to space.

    20. atmospheric "window"

      The atmospheric window refers to the range of wavelengths of light that are emitted from Earth to space with little absorption by atmospheric gases.

      Radiation in this range allows the Earth to get rid of excess heat energy from the Sun and maintain a constant temperature.

    21. anthropogenic carbon dioxide

      Anthropogenic pollutants are harmful substances released into the environment from human activities.

      Carbon dioxide is one such pollutant, and is released from the burning of fossil fuels, such as coal and gasoline.

    22. Northwest Passage

      The Northwest Passage is the sea route that connects the Atlantic and Pacific Oceans along the northern coast of North America.

      Early European explorers believed the Northwest Passage could allow easy access to Asia, but the waters were too shallow and icy to be navigable.

    23. volcanic aerosols

      Aerosols are small particles of solid and liquid that are suspended in air.

      When volcanoes erupt, they release a large quantity of aerosols. These aerosols can reflect sunlight back into space, cooling the ground below.

  4. Nov 2021
  5. Oct 2021
    1. intron retention

      RNA transcripts have two major components - exons and introns. Exons stay in the transcript that gets made into a protein, whereas introns are cut out, and this is known as splicing.

      Intron retention refers to a transcription event where an intron is kept in the RNA instead of being removed. This process can allow for more diversity of transcripts from the same gene.

      You can visualize the splicing process here: https://www.biointeractive.org/classroom-resources/rna-splicing

    2. lentivirus

      Lentivirus is a type of virus that contains reverse transcriptase - a molecule that transcribes RNA into DNA to integrate into the genome and infect host cells.

      Lentivirus can be used to deliver desired DNA into cells. This lentiviral transduction allows for gene expression of desired sequences in organisms of interest.

      You can watch more about cloning to make the DNA for transduction here: https://www.biointeractive.org/classroom-resources/dna-cloning-plasmids, and you visualize the workflow of lentiviral transduction here: https://www.mirusbio.com/applications/high-titer-virus-production/lentivirus-production#figure1303

    3. H3 lysine 27 (H3K27) demethylase KDM6B

      The histone proteins have exposed "tails" of peptides that can be modified with additional chemical groups, such as methyl or acetyl molecules. These molecules can alter how the histone interacts with its associated DNA.

      These chemical modifications can be added or removed by specific proteins, such as KDM6B, which removes histone subunit 3 lysine residue 27 methylations.

      You can learn more about histone modifications here: https://www.youtube.com/watch?v=OqRt723t33o

    4. chromatin immunoprecipitation (ChIP)

      Chromatin immunoprecipitation, or ChIP, identifies the DNA regions were a protein binds across the genome.

      First, an antibody recognizes and binds a protein of interest in the nucleus. Then the antibody holding onto the protein is isolated and any DNA bound the protein is captured for analyses.

      This article describes ChIP and it's application, with some example data analysis, here: https://www.sigmaaldrich.com/US/en/technical-documents/technical-article/genomics/gene-expression-and-silencing/chromatin-immunoprecipitation-chip

    5. in situ hybridization

      A common technique to visualize nucleotide (DNA or RNA) in cells.

      A chemical or radioactive label is added to a nucleotide sequence that is complimentary to the sequence of interest. When added to the cells, this complimentary nucleotide sequence will bind to and tag the sequence of interest, allowing scientists to visualize the DNA or RNA of interest within the cell.

      You can read more about in situ hybridization methods here: https://www.nature.com/scitable/topicpage/fluorescence-in-situ-hybridization-fish-327/

    6. quantitative PCR (qPCR)

      Quantitative polymerase chain reaction (qPCR) measures RNA or DNA levels for comparison among samples.

      This technique is very similar to qRT-PCR (described in above annotations), but does not always require reverse transcription.

    7. molecular basis

      The authors are hoping to reveal the molecular biology underlying Kdm6b-depletion sex reversal. They will test for the genes that KDM6B can directly bind and activate expression for in developing T.scripta gonads.

    8. ectopic

      Ectopic describes events occurring in locations that do not naturally have such events.

      For example, expression of a brain-specific gene in a toenail would be considered ectopic gene expression.

      Here ectopic describes the presence of aromatase in Kdm6b-depleted gonads at MPT, which produces female sex hormones.

    9. loss-of-function mutants

      A mutation is a change to the structure or sequence of a gene compared to a reference.

      Loss of function mutations cause a gene not to make functional amounts or forms of its protein.

      Here, the shRNA is blocking Kdm6b expression, meaning that there is not enough KDM6B to function normally in the Kdm6b-RNAi embryos.

    10. master regulator

      A master regulator often refers to a protein that initiates the cascade of expression for all genes involved in a specific pathway, such as cell fate and development pathways.

    11. phenotypic plasticity

      A phenotype describes the physical properties of an organism that can be observed.

      A genotype defines the genetic composition of an organism, including chromosomes and DNA sequences.

      Together, phenotypic plasticity is the ability of one genotype to produce multiple different phenotypes in an organism.

    1. public health (non-pharmaceutical) interventions

      Public health interventions are everyday actions that the public can take to stop the spread of an infectious disease. As indicated by the word in the parentheses, taking medication or vaccination is not considered a public health intervention.

  6. Sep 2021
    1. 6-hydroxydopamine (6-OHDA)

      a neurotoxic synthetic organic compound used by researchers to selectively destroy the brain's dopaminergic as well as noradrenergic neurons. In this paper, it was used to ablate dopaminergic neurons, so as to stop dopamine synthesis.

    2. reserve pool of cells

      In a review article on reserve pool neuron transmitter respecification, Dulcis et al. provide a helpful analogy for understanding reserve pools. In this analogy, the role of reserve pools is compared to having two jobs, and following certain physiological stimuli, one of those jobs is relinquished. Dulcis et al. defines reserve pool neurons as "cells that share inputs and outputs with adjacent core pools of neurons but express different neurotransmitters." In one situation, the neurons from both pools could be expressing the same transmitters, but the core neurons also express a secondary transmitter; following the change in circuit activity, the neurons of the reserve pool will stop expressing the transmitter that it has in common with the core pool of neurons. In an alternative scenario, these two pools of neurons could be expressing different neurotransmitters, and the change in circuit activity results in the neurons of the reserve pool acquiring the expression of the transmitter that is already expressed by the core neurons (23).

    3. BrdU

      BrdU is an analog of the nucleoside thymidine, and would be incorporated into newly synthesized DNA. Since the fundamental requirement for cell proliferation is DNA synthesis, quantifying the incorporation of BrdU following application of anti-BrdU antibodies will therefore enable measurements of cell proliferation.

    1. nested topology—specialist species tend to interact with subsets of partners of the most generalist species

      Metaphorically, nestedness can be compared to a Russian doll, where the diet of specialist species (smaller dolls) fits within the diet of the more generalist species (larger dolls).

    2. weighted

      A weighted network assigns some form of quantitative value to each connection between two partners (an example is shown below in figure 4). In this case, the value assigned was the frequency of interaction.

    3. We decomposed this metric into two components: species turnover (βST—the proportion of interactions that are not shared owing to differences in species composition between two networks) and linkage turnover [βOS, also called rewiring—the proportion of interactions unique to a single network despite the occurrence of both partners in both networks (30)

      The authors measured the overall dissimilarity between different locations by two factors:

      species turnover when — two  locations do not share similar interaction patterns because they are inhabited by different species,

      and linkage turnover — when species found in both locations develop different interactions specific to their site

    4. The wider variety of partners used at the larger scale (regional network) corresponds to the “fundamental niche,” whereas the subset of partners found at local scales indicates that local populations have much more restricted “realized niches” (27, 28).

      A species' fundamental niche encompasses all of the possible roles it has in its environment, whereas the realized niches are the actual roles that a species plays in its environment, taking into account competition, predation, and other interactions with neighboring species.

      The video below further explains this: https://www.youtube.com/watch?v=-6COob_bymw

    1. replacement rate

      The replacement rate of 1 means that one case in a completely susceptible population can lead to one secondary case. Assuming that the initial case can be cured and reach full recovery — which is what all of us hope — a rate equal to 1 means that one is infected when another gets well, leading to an unchanged number of cases.

    2. U = 8197, z = –3.4, P < 0.01

      The Mann-Whitney U statistic can be seen as the cumulative result of comparing the randomly drawn values from two populations. z is the standardized value and is dependent on the sizes of the two populations. P is the probability for a null hypothesis to be true.

    3. Mann-Whitney

      The Mann-Whitney U test is a test for a null hypothesis that it is equally possible for a value drawn from a population to be greater or smaller than another from a different population. This test is useful when the distributions of values are unspecified. In this study, one population comprises cities that took action earlier, and the other is for cities that responded later.

    4. P < 0.01

      P is the probability that the null hypothesis is true. The null hypothesis, in this case, is that the total number of cases reported from each province shows no significant linear correlation with the total number of travelers from Wuhan.

    5. r = 0.98

      r is the correlation coefficient for an association between two factors. It can take values between -1 and 1. A correlation coefficient equal to -1 indicates a perfectly inverse linear correlation, meaning that one variable decreases in its value in response to the increase of the other linearly. In contrast, an r equal to 1 indicates a perfect linear positive correlation. An r of zero signifies the nonexistence of an association.

    6. agent

      Agents are the causes of diseases and injuries, but they are not the sole determinant for the occurrence of a disease. The other two factors are the host (the human who can get the disease) and the environment that brings the agents and the host together.

    1. inline

      Inline refers to the insertion of a smaller computer program into a larger, main code.

      The inline code performs a specific function.

      Here, the inline code generates the aerosol properties needed for the ozone calculation.

  7. Aug 2021
    1. isostere

      Elements that have the same number of electrons in the outermost shell (also known as valence shell) and have similar electronic properties. For example, carbon and silicon are isosteres as they both have four valence electrons.

    2. directed evolution

      IA method of engineering proteins towards a defined property. Process of directed evolution: Directed evolution mimics "real" evolution and is accelerated in the laboratory by focusing on individual genes expressed in fast‐growing microorganisms such as E. coli. Enzyme chosen (known as wild-type) must show at least a minimal desired reactivity. Mutations are randomly or site specifically introduced to the gene of the wild type protein. Then, the library of protein variants is screened for the ones with enhanced reactivity. The improved enzymes are used as parents for the next round of mutation and screening. Additional beneficial mutations are introduced if needed. This can continue for several cycles until a desired and new property of the enzyme is attained.

    1. interneurons

      Interneurons connect sensory neurons, the nerve cells that convert environmental stimuli into internal electrical impulses, and motor neurons, which transmit signals from the brain to control muscle movements. Therefore, interneurons act as a "middle-man", passing signals from sensory neurons to motor neurons.

    2. dopamine

      Commonly called the "feel-good" chemical because of its role in the brain's reward system, dopamine is a neurotransmitter associated with feelings of pleasure, learning, memory, and motor system functions.

    3. somatostatin

      Also known as growth hormone-inhibiting hormone, somatostatin is a peptide hormone that primarily functions to prevent the unnatural rapid proliferation of cells, the hallmark of tumors. Somatostatin also plays a role in the gastrointestinal system.