A semaphorin code defines subpopulations of spinal motor neurons during mouse development.
In the spinal cord, motor neurons (MNs) with similar muscle targets and sensory inputs are grouped together into motor pools. To date, relatively little is known about the molecular mechanisms that control the establishment of pool-specific circuitry. Semaphorins, a large family of secreted and cell surface proteins, are important mediators of developmental processes such as axon guidance and cell migration. Here, we used mRNA in situ hybridization to study the expression patterns of semaphorins
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Tips for Identifying Poison Ivy
This online article, from Biodiversity Counts, is a tip sheet to help students learn how to spot and avoid poison ivy. Specifically, it covers: an overview of the different varieties of the plant that grow in the Americas and Asia; an illustration of the compound leaf with three leaflets (trifoliate); details about poison ivy's leaf type, leaf arrangement, growth form, flowers, fruits, and relatives; how contact with the plant causes a hypersensitivity reaction in most people; a trick you can tr
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Fairly Simple Geology Exercises
This is a collection of 18 geology exercises that are designed for teachers with little or no geology background. Each exercise includes relevant background information, complete instructions, student handouts and answer keys. Topics include rock and mineral identification, Bowen's reaction series, crystal models, topographic maps, earthquakes, groundwater, oil exploration, plate tectonics and more.
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Language and genes of the greater Himalayan region
This Web page outlines research using molecular population genetics to gain an insight into the prehistory of the greater Himalayan region, and the development and distribution of its incredible linguistic diversity. DNA samples were taken from populations within Nepal and Bhutan and compared with samples from India and China, allowing the genetic map of the region to be compared with the linguistic. The website includes links to published outcomes, and details of researchers involved in the pro
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East Asia in Transition: Comprehensive Security in the Pacific Rim
East Asia in Transition: Comprehensive Security in the Pacific Rim with introductory remarks by: T.J. Pempel, UC Berkeley Robert Scalapino, UC Berkeley Panel 1: "Finding Multilateral Solutions to New and Enduring Problems" Chair: TJ Pempel, UC Berkeley Panelists: Susan Shirk, UC San Diego Track II Diplomacy in Northeast Asia David Shambaugh, George Washington University. China and Multilateralism in Asia Mely Caballero-Anthony, Institute of Defence and Strategic Studies (IDSS), Singapore. East
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The Microbial Biorealm
The Microbial Biorealm is an informational site about microbes written by students for students. Hosted by Kenyon College, the site includes molecular and taxonomic information about microbes from all three domains of life. A comprehensive table lists the properties and characteristics of each domain of life while taxonomy pages list classification, description, significance, genome structure, cell structure, metabolism, ecology, isolation, cultivation, and references specific to individual taxa
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NCBI: Education
This Web site from the National Center for Biotechnology Information (NCBI) offers a set of detailed tutorials to help users make full use of NCBI's bioinformatics tools. The tutorials, which target both new and veteran users, cover NCBI's BLAST and PSI-BLAST, Entrez data retrieval system, Cn3D molecular structure software, and more. Additionally, the Science Primer tutorial offers a "basic introduction to the science underlying NCBI resources" geared more toward the general reader.
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Northern Fur Seal Information
This National Marine Mammal Laboratory website provides links to detailed information about the distribution of fur seals in the Bering Sea region. It also features related links that lead to maps of fur seal rookeries on St. Paul Island and St. George Island, as well as PDF reports that describe fur seal population dynamics from 1993-2001.
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20.441J Biomaterials-Tissue Interactions (MIT)
This course covers the principles of materials science and cell biology underlying the design of medical implants, artificial organs, and matrices for tissue engineering. Methods for biomaterials surface characterization and analysis of protein adsorption on biomaterials. Molecular and cellular interactions with biomaterials are analyzed in terms of unit cell processes, such as matrix synthesis, degradation, and contraction. Mechanisms underlying wound healing and tissue remodeling following imp
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Content within individual OCW courses is (c) by the individual authors unless otherwise noted. MIT OpenCourseWare materials are licensed by the Massachusetts Institute of Technology under a Creative C

Reversible Reactions
Watch a reaction proceed over time. How does total energy affect a reaction rate? Vary temperature, barrier height, and potential energies. Record concentrations and time in order to extract rate coefficients. Do temperature dependent studies to extract Arrhenius parameters.
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Anisotropic Oscillator Model
The EJS Anisotropic Oscillator model displays the dynamics of a mass connected to two opposing springs. The simulation displays the motion of the mass as well as the trajectory plot. The initial position of the mass can be changed by dragging. The unstretched lengths of the springs can changed as well via textboxes.
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Lennard-Jones Potential Model
The EJS Lennard-Jones Potential model shows the dynamics of a particle of mass m within this potential. You can drag particle to change its position and you can drag the energy-line to change its total energy. The Lennard-Jones potential function is a reasonably accurate model of interactions between noble gas atoms.  The binding energy epsilon is the depth of the potential well and minimum molecular separation are set equal to unity.  This simulation uses uses a natural system of units the m
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Molecular Dynamics Demonstration Model
The EJS Molecular Dynamics Demonstration model is constructed using the Lennard-Jones potential truncated at a distance of 3 molecular diameters. The motion of the molecules is governed by Newton's laws, approximated using the Verlet algorithm with the indicated Time step. For sufficiently small time steps dt, the system's total energy should be approximately conserved. Users can select various initial configurations using the drop down menu.
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Ejs TPT Ladder Demonstration Model
The EJS TPT Ladder Demonstration model displays the statics and dynamics of a ladder leaning against a wall. The standard (textbook) statement of this problem assumes that there is no frictional force between the wall and the ladder, but a frictional force between the ground and the ladder. In the simulation you can set the initial lean angle and the coefficients of static and kinetic friction between the floor and the ladder.
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Circumnavigating Pendulum Model
The EJS Circumnavigating Pendulum model displays the dynamics of a mechanical oscillator in uniform circular motion. The mechanical oscillator is free to move in two directions. This 2-dimensional simulation displays all the dynamical features of the Foucault pendulum, except for the dependency of the Foucault pendulum precession on latitude. The simulation shows simultaneously the motion with respect to the inertial coordinate system, and the motion as seen from a co-rotating point of view.
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Newton's Second Law
This lesson introduces students to Sir Isaac Newton's Second Law of Motion. Topics include the two ways to study the dynamics of a system in which there is motion and a brief description of Newton's work in studying and measuring the motion of objects.
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Understanding Your Water
Over two class periods, you will be guiding your students through the basics of water treatment -- both tap water treatment and sewage (or wastewater) treatment. To prepare for the lessons on the treatment process, the students will be researching where their drinking water comes from and where their wastewater goes once it goes down the drain for homework. After learning about their local water treatment and traditional tap water and sewage treatment processes, students will watch the NewsHour
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Virtual Laboratory
The simulation program is based on the Nobel Prize winning Hodgkin-Huxley model for excitation of the squid axon. The program simulates an excised squid axon by applying stimuli or clamps after setting the environment of the axon, changing its properties, and/or adding drugs or toxins. By using the program tools, experiments can be developed that explore a variety of nerve properties, ranging from classical phenomena such as threshold, summation, refractory period, and impulse propagation to mo
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Mixed Reception Scenario
This activity is set in a research group that is developing an antivenom for spider bites. In the opening scene, Nelson Pogline, a talented graduate student, dies unexpectedly at a university reception. As a detective, you must use chemistry concepts to determine if this was murder and if so, solve the case. You can interview suspects using Quicktime movies, investigate the crime scene for clues with Quicktime Virtual Reality images, and analyze the evidence from the crime lab. This activity req
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Limiting Reagents
We are now ready to pull everything we know about reaction stoichiometry together, and answer the question: Given some initial amount of reactants, what should be present after a chemical reaction goes to completion? The procedure for answering this question is often called the "limiting reagent problem." You'll see why this name is appropriate in the following video.
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