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October, 2006
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Dean-Stark Trap

JoVE 10340

Source: Vy M. Dong and Jan Riedel, Department of Chemistry, University of California, Irvine, CA

A Dean-Stark trap is a special piece of glassware, which allows the collection of water during a reaction through an azeotropic distillation. The desire to collect water from a reaction can have various reasons. It can drive the equilibria in reactions, where water is formed as a byproduct. According to Le Chatelier's principle, a change in temperature, pressure, concentration, or volume will cause a readjustment of a reversible reaction to establish a new equilibrium. An acetal formation is a reversible reaction, where water is formed as a byproduct. In such cases, achieving good yields is possible by driving the equilibrium towards the product side via the removal of water. The Dean-Stark trap also allows the determination of water content or can be used to remove water from a solvent mixture through an azeotropic distillation.

 Organic Chemistry II

Vectors in Multiple Directions

JoVE 10315

Source: Nicholas Timmons, Asantha Cooray, PhD, Department of Physics & Astronomy, School of Physical Sciences, University of California, Irvine, CA

This experiment demonstrates how vectors add and subtract in multiple directions. The goal will be to analytically calculate the addition or subtraction of multiple vectors and then to experimentally confirm the calculations. A vector is an object with both magnitude and direction. The magnitude of a vector is simply denoted as the length, while the direction is typically defined by the angle it makes with the x-axis. Because forces are vectors, they can be used as a physical representation of vectors. By setting up a system of forces and finding which additional force will create an equilibrium between the forces, a system of vectors can be experimentally verified.

 Physics I

Sound Waves and Doppler Shift

JoVE 10411

Source: Arianna Brown, Asantha Cooray, PhD, Department of Physics & Astronomy, School of Physical Sciences, University of California, Irvine, CA

Waves are disturbances that propagate through a material medium or empty space. Light waves can travel through a vacuum and some forms of matter, and are transverse in nature, which means that the oscillations are perpendicular to the direction of propagation. However, sound waves are pressure waves that travel through an elastic medium like air, and are longitudinal in nature, which means the oscillations are parallel to the direction of propagation. When sound is introduced to a medium by a vibrating object, like the vocal chords of a person or strings in a piano, the particles in the air experience forward and backward motion as the vibrating object moves forward and backward. This results in regions in the air where the air particles are compressed together, called compressions, and other regions where they are spread apart, called rarefactions. The energy created by a sound wave oscillates between the potential energy created by the compressions and the kinetic energy of the small movements and speeds of the particles of the medium. Compressions and rarefactions can be used to define the relationship be

 Physics II

Hooke's Law and Simple Harmonic Motion

JoVE 10326

Source: Ketron Mitchell-Wynne, PhD, Asantha Cooray, PhD, Department of Physics & Astronomy, School of Physical Sciences, University of California, Irvine, CA

Potential energy is an important concept in physics. Potential energy is the energy associated with forces that depend upon the position of an object relative to its surroundings. Gravitational potential energy, which is discussed in another video, is the energy associated that is directly proportional to the height of an object above the ground. Similarly, it is possible to define spring potential energy, which is directly proportional to the displacement of a spring from its relaxed state. A stretched or compressed spring has potential energy, as it has the ability to do work upon an object. The “ability to do work” is often quoted as the fundamental definition of energy. This video will demonstrate the potential energy stored in springs. It will also verify the restoring force equation of springs, or Hooke’s Law. The spring constant is different for springs of different elasticities. Hooke’s law will be verified and the spring constant measured by attaching varying weights to a suspended spring and measuring the resulting displacements.

 Physics I

Energy and Work

JoVE 10313

Source: Ketron Mitchell-Wynne, PhD, Asantha Cooray, PhD, Department of Physics & Astronomy, School of Physical Sciences, University of California, Irvine, CA

This experiment demonstrates the work-energy principle. Energy is one of the most important concepts in science and is not simple to define. This experiment will deal with two different kinds of energy: gravitational potential energy and translational kinetic energy. Gravitational potential energy is defined as the energy an object possesses because of its placement in a gravitational field. Objects that are high above the ground are said to have large gravitational potential energy. An object that is in motion from one location to another has translational kinetic energy. The most crucial aspect of energy is that the sum of all types of energy is conserved. In other words, the total energy of a system before and after any event may be transferred to different kinds of energy, wholly or partly, but the total energy will be the same before and after the event. This lab will demonstrate this conservation. Energy can be defined as "the ability to do work," which relates mechanical energy with work. Flying projectiles that hit stationary objects do work on those stationary objects,

 Physics I

Kinematics and Projectile Motion

JoVE 10314

Source: Ketron Mitchell-Wynne, PhD, Asantha Cooray, PhD, Department of Physics & Astronomy, School of Physical Sciences, University of California, Irvine, CA

This experiment demonstrates the kinematics of motion in 1 and 2 dimensions. This lab will begin by studying motion in 1 dimension, under constant acceleration, by launching a projectile directly upward and measuring the maximum height reached. This lab will verify that the maximum height reached is consistent with the kinematic equations derived below. Motion in 2 dimensions will be demonstrated by launching the ball at an angle θ. Using the kinematic equations below, one can predict the distance to where the projectile will land based upon the initial speed, total time, and angle of trajectory. This will demonstrate kinematic motion with and with out acceleration in the y- and x-directions, respectively.

 Physics I

Preparing and Administering Enteric Tube Medications

JoVE 10287

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

An enteric tube is a tube that is inserted and passed into the stomach or intestines. Enteric tubes serve multiple purposes, including stomach decompression (through the removal of air, gastric contents, and secretions), enteric feeding, and/or the administration of medications or oral contrast. Enteric tubes are indicated for patients with impaired swallowing and for patients with neurological or other conditions associated with an increased risk of aspiration, or when the patient is unable to maintain adequate oral intake of fluid or calories. There are multiple types of enteric tubes, with their generic names assigned according to the insertion site and the gastrointestinal termination point. For instance, one of the common tube types is the nasogastric tube, which is inserted through a nostril and passed along the upper gastrointestinal tract into the stomach. When administering medications through an enteric tube, it is important to ensure that the tube terminates in the intended gastrointestinal location. When enteric tubes are initially placed, the position of the tube is verified by X-ray. However, due to gastric peristalsis, enteric tubes may migrate out of their intended

 Nursing Skills

Perspectives on Social Psychology

JoVE 10434

Social Psychology is a complex field—one that investigates how social contexts affect people’s actions, thoughts, and attitudes. It brings the scientific method into our everyday lives by addressing questions relevant to interactions amongst individuals near and far or even over the internet. For example, the video about ostracism details an approach to induce feelings of exclusion without direct face-to-face contact. These videos are meant to show the wide reactionary nature of human beings, which also makes the experimental process more complicated. By providing students and scientists a transparent look at the intricate research methods behind classic experiments, this collection strengthens their understanding into just how researchers manipulate contexts to elicit behaviors—some that we are not even aware of harboring. For instance, the video "Implicit Association Test" explores how to measure unconscious attitudes for sensitive topics, like racial prejudice. This collection in Social Psychology provides the perfect introduction to this subject and insight into future directions, such as integration with neuroscience and big data collected via social media outlets.

 Social Psychology

Melting Point

JoVE 10356

Source: Vy M. Dong and Jan Riedel, Department of Chemistry, University of California, Irvine, CA

One of the most important properties of a crystalline solid is its melting point. It can be used to determine the purity of a known compound and gives important information about the stability of the formed crystals.

 Organic Chemistry II

Solid Phase Synthesis

JoVE 10349

Source: Vy M. Dong and Diane Le, Department of Chemistry, University of California, Irvine, CA

Merrifield's solid-phase synthesis is a Nobel Prize winning invention where a reactant molecule is bound on a solid support and undergoes successive chemical reactions to form a desired compound. When the molecules are bound to a solid support, excess reagents and byproducts can be removed by washing away the impurities, while the target compound remains bound to the resin. Specifically, we will showcase an example of solid-phase peptide synthesis (SPPS) to demonstrate this concept.

 Organic Chemistry II

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