Thermodynamic Entropy And The Accessible States of Some Simple Systems

Comparison of the thermodynamic entropy with Boltzmann's principle shows that under conditions of constant volume the total number of arrangements in simple thermodynamic systems with temperature-independent heat capacities is TC/k. A physical interpretation of this function is given for three such systems; an ideal monatomic gas, an ideal gas of diatomic molecules with rotational motion, and a solid in the Dulong-Petit limit of high temperature. T1/2 emerges as a natural measure of the number of accessible states for a single particle in one dimension. Extension to N particles in three dimensions leads to TC/k as the total number of possible arrangements or microstates. The different microstates of the system are thus shown a posteriori to be equally probable, with probability T-C/k, which implies that for the purposes of counting states the particles of the gas are distinguishable. The most probable energy state of the system is determined by the degeneracy of the microstates.Comment: 9 pages, 1 figur

Teacher education accreditation in Turkey: The creation of a culture of quality

Cataloged from PDF version of article.Turkey’s experience in developing and piloting accreditation criteria and national standards for teacher education is examined. The full implementation of an accreditation process for teacher education programs was not completed within the time of the development project. However, the effort to do so encouraged the formation of a ‘quality culture’ in the faculties of education. The paper discusses what took place and analyses the later response of teacher educators to the introduction of accreditation criteria and the way in which they were introduced. Educators largely welcomed national standards and accreditation, but wished to have flexible means of implementation

Comparison of bungee-aided and free-bouncing accelerations on trampoline

Trampolines remain the single best apparatus for the training of aerial acrobatics skills. Trampoline use has led to catastrophic injuries from poor landings. Passive injury prevention countermeasures such as specialized matting have been largely ineffective. Active injury countermeasures such as hand spotting, “throw-in” mats, and overhead spotting rigs provide the most effective methods. The recent addition of several bungee cords between the ropes and the gymnast’s spotting harness has resulted in altered teaching and coaching of trampoline-related acrobatics. Bungee cords have eliminated the need for a coach/spotter to manage the ropes during skill learning. The purpose of this study was to assess the influence of the addition of bungee cords with a traditional rope-based overhead spotting rig. There is a paucity of any research involving trampoline injury countermeasures. Ten experienced trampoline acrobatic athletes (5 males, 5 females) from the U.S. Ski and Snowboard Association Aerials National Team performed 10 bounces as high as they could control. A triaxial accelerometer (200 Hz) characterized 10 bungee cord aided bounces and 10 freebounces on a trampoline from each athlete. Bed contact times, peak accelerations, and average accelerations were obtained. The results supported our hypotheses that the bungeeaided bounces achieved only 40% (average) to 70% (peak) of the free-bouncing accelerations (all ρ 0.092). The bed contact time was approximately 65% longer during the bungee-aided bounces (ρ < 0.001). Bungee cords may reduce the harshness of landings on trampoline

Bone marrow transplantation alters the tremor phenotype in the murine model of globoid-cell leukodystrophy

Tremor is a prominent phenotype of the twitcher mouse, an authentic genetic model of Globoid-Cell Leukodystrophy (GLD, Krabbe’s disease). In the current study, the tremor was quantified using a force-plate actometer designed to accommodate low-weight mice. The actometer records the force oscillations caused by a mouse’s movements, and the rhythmic structure of the force variations can be revealed. Results showed that twitcher mice had significantly increased power across a broad band of higher frequencies compared to wildtype mice. Bone marrow transplantation (BMT), the only available therapy for GLD, worsened the tremor in the twitcher mice and induced a measureable alteration of movement phenotype in the wildtype mice. These data highlight the damaging effects of conditioning radiation and BMT in the neonatal period. The behavioral methodology used herein provides a quantitative approach for assessing the efficacy of potential therapeutic interventions for Krabbe’s disease

Tactile Data Entry for Extravehicular Activity

In the task-saturated environment of extravehicular activity (EVA), an astronaut's ability to leverage suit-integrated information systems is limited by a lack of options for data entry. In particular, bulky gloves inhibit the ability to interact with standard computing interfaces such as a mouse or keyboard. This paper presents the results of a preliminary investigation into a system that permits the space suit gloves themselves to be used as data entry devices. Hand motion tracking is combined with simple finger gesture recognition to enable use of a virtual keyboard, while tactile feedback provides touch-based context to the graphical user interface (GUI) and positive confirmation of keystroke events. In human subject trials, conducted with twenty participants using a prototype system, participants entered text significantly faster with tactile feedback than without (p = 0.02). The results support incorporation of vibrotactile information in a future system that will enable full touch typing and general mouse interactions using instrumented EVA gloves

Polyimide Aerogels and Porous Membranes for Ultrasonic Impedance Matching to Air

This work investigates acoustic impedance matching materials for coupling 200 kHz ultrasonic signals from air to materials with similar acoustic properties to that of water, flesh, rubber and plastics. Porous filter membranes as well as a new class of cross-linked polyimide aerogels are evaluated. The results indicate that a single impedance matching layer consisting of these new aerogel materials will recover nearly half of the loss in the incident-to-transmitted ultrasound intensity associated with an air/water, air/flesh or air/gelatin boundary. Furthermore, the experimental results are obtained where other uncertainties of the "real world" are present such that the observed impedance matching gains are representative of real-world applications. Performance of the matching layer devices is assessed using the idealized 3-layer model of infinite half spaces, yet the experiments conducted use a finite gelatin block as the destination medium

Classical and Quantum-like approaches to Charged-Particle Fluids in a Quadrupole

A classical description of the dynamics of a dissipative charged-particle fluid in a quadrupole-like device is developed. It is shown that the set of the classical fluid equations contains the same information as a complex function satisfying a Schrodinger-like equation in which Planck's constant is replaced by the time-varying emittance, which is related to the time-varying temperature of the fluid. The squared modulus and the gradient of the phase of this complex function are proportional to the fluid density and to the current velocity, respectively. Within this framework, the dynamics of an electron bunch in a storage ring in the presence of radiation damping and quantum-excitation is recovered. Furthermore, both standard and generalized (including dissipation) coherent states that may be associated with the classical particle fluids are fully described in terms of the above formalism.Comment: LaTex, to appear in Physica Script

Stretching the spines of gymnasts: a review

Gymnastics is noted for involving highly specialized strength, power, agility and flexibility. Flexibility is perhaps the single greatest discriminator of gymnastics from other sports. The extreme ranges of motion achieved by gymnasts require long periods of training, often occupying more than a decade. Gymnasts also start training at an early age (particularly female gymnasts), and the effect of gymnastics training on these young athletes is poorly understood. One of the concerns of many gymnastics professionals is the training of the spine in hyperextension-the ubiquitous 'arch' seen in many gymnastics positions and movements. Training in spine hyperextension usually begins in early childhood through performance of a skill known as a back-bend. Does practising a back-bend and other hyperextension exercises harm young gymnasts? Current information on spine stretching among gymnasts indicates that, within reason, spine stretching does not appear to be an unusual threat to gymnasts' health. However, the paucity of information demands that further study be undertaken