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No-Observed-Adverse-Effect Level: The highest dosage administered that does not produce toxic effects. The Noael will depend on how closely dosages are spaced (lowest-observed-adverse-effect level and no-observed-effect level) and the number of animals examined. The ultimate objective is usually to determine not the "safe" dosage in laboratory animals but the "safe" dosage for humans. Therefore, the extrapolation most often required of toxicologists is from high-dosage studies in laboratory animals to low doses in humans. (Casarett and Doull's Toxicology: The Basic Science of Poisons, 4th ed)

Photoelectric Effect

JoVE 10413

Source: Yong P. Chen, PhD, Department of Physics && Astronomy, College of Science, Purdue University, West Lafayette, IN

Photoelectric effect refers to the emission of electrons from a metalwhen light is shining on it. In order for the electrons to be liberated from the metal, the frequency of the light needs to be sufficiently…

 Physics II

The Effect of Reflux Ratio on Tray Distillation Efficiency

JoVE 10432

Source: Kerry M. Dooley and Michael G. Benton, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA

Tray and packed columns are both commonly used for distillation, absorption, and stripping separation operations.1,2 The goal of this experiment is to distill a mixture of alcohols (methanol, isopropanol) and water …

 Chemical Engineering

Microscopy and Staining: Gram, Capsule, and Endospore Staining

JoVE 10513

Source: Rhiannon M. LeVeque1, Natalia Martin1, Andrew J. Van Alst1, and Victor J. DiRita1
1 Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America

Bacteria are diverse microorganisms found nearly everywhere on Earth. Many properties help distinguish them from…


Preparing and Administering IV Push Medications

JoVE 10262

Source: Madeline Lassche, MSNEd, RN and Katie Baraki, MSN, RN, College of Nursing, University of Utah, UT

Intravenous (IV) push is the rapid administration of a small volume of medication into a patient's vein via a previously inserted IV catheter. Preparations for IV push administration are commonly provided in vials or ampules for…

 Nursing Skills

Climate Change - Student Protocol

JoVE 10610

Melting Land and Sea Ice
NOTE: This activity is a simulation of land- and sea-ice melting and their effects on water levels.
First, label one graduated cylinder as 'Sea Ice' and the other graduated cylinder as 'Land Ice.' Hypotheses: the experimental hypothesis might be that the land ice melting will cause the water level to rise more than the…

 Lab Bio

Misattribution of Arousal and Cognitive Dissonance

JoVE 10333

Source: Peter Mende-Siedlecki & Jay Van Bavel—New York University

A host of research in psychology suggests that feelings of psychological arousal may be relatively ambiguous, and under certain circumstances, can lead us to make inaccurate conclusions about our own mental states. Much of this work flows from seminal research…

 Social Psychology

Temperature Dependence - Student Protocol

JoVE 11175

Temperature Dependent Decomposition of Hydrogen Peroxide

We suggest that students work in pairs for this experiment. Equipment controls may vary.

In this lab, you'll perform a decomposition reaction where a single compound breaks down into two or more simpler products. You will observe the decomposition of hydrogen…

 Lab: Chemistry

Trophic Efficiency

JoVE 10930

Trophic level transfer efficiency (TLTE) is a measure of the total energy transfer from one trophic level to the next. Due to extensive energy loss as metabolic heat, an average of only 10% of the original energy obtained is passed on to the next level. This pattern of energy loss severely limits the possible number of trophic levels in a food chain.

Following the second law of thermodynamics, large amounts of energy are lost from the ecosystem and from one trophic level to the next as it is transferred and transformed. In biological systems, this energy is lost as metabolic heat during respiration as one organism consumes the next. The measurement of energy transfer from one trophic level to the next is known as trophic level transfer efficiency (TLTE) and is a function of energy production of the present trophic level and that at the previous level. This measurement has broad implications concerning the total length of food chains. In general, only about 10% of energy is transferred from one trophic level to the next, and this number can vary from 5-20% depending on the ecosystem. This means that 90% of obtained energy is lost at each trophic level, greatly affecting the maximum number of possible levels in the ecosystem. For example, if an ecosystem received 600,000 Kcal of solar energy from the sun, primary producers would pass on only 60,000 K

 Core: Biology

Eusociality and Division of Labor- Concept

JoVE 10617

Social Organization

Varying levels of social organization are observed within the animal kingdom, ranging from simple to highly complex. These systems can greatly enhance the survival and reproductive success of an individual or a population. Of these, eusociality is the highest level of social organization, involving divisions of labor based on social castes. However, this system …

 Lab Bio
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