Conducting a thermal conductivity survey

A physically transparent approximate theory of phonon decay rates is presented starting from a pair potential model of the interatomic forces in an insulator or semiconductor. The theory applies in the classical regime and relates the 3-phonon decay rate to the third derivative of the pair potential. Phonon dispersion relations do not need to be calculated, as sum rules relate all the needed quantities directly to the pair potential. The Brillouin zone averaged phonon lifetime turns out to involve a dimensionless measure of the anharmonicity multiplied by an effective density of states for 3-phonon decay. Results are given for rare gas and alkali halide crystals. For rare gases, the results are in good agreement with more elaborate perturbation calculations. Comparison to experimental data on phonon linewidths and thermal conductivity are made

Astrophysical signatures of leptonium

More than 10^43 positrons annihilate every second in the centre of our Galaxy yet, despite four decades of observations, their origin is still unknown. Many candidates have been proposed, such as supernovae and low mass X-ray binaries. However, these models are difficult to reconcile with the distribution of positrons, which are highly concentrated in the Galactic bulge, and therefore require specific propagation of the positrons through the interstellar medium. Alternative sources include dark matter decay, or the supermassive black hole, both of which would have a naturally high bulge-to-disc ratio. The chief difficulty in reconciling models with the observations is the intrinsically poor angular resolution of gamma-ray observations, which cannot resolve point sources. Essentially all of the positrons annihilate via the formation of positronium. This gives rise to the possibility of observing recombination lines of positronium emitted before the atom annihilates. These emission lines would be in the UV and the NIR, giving an increase in angular resolution of a factor of 10^4 compared to gamma ray observations, and allowing the discrimination between point sources and truly diffuse emission. Analogously to the formation of positronium, it is possible to form atoms of true muonium and true tauonium. Since muons and tauons are intrinsically unstable, the formation of such leptonium atoms will be localised to their places of origin. Thus observations of true muonium or true tauonium can provide another way to distinguish between truly diffuse sources such as dark matter decay, and an unresolved distribution of point sources.Comment: Accepted for publication in EPJ-D, 9 pages, 4 figure

Assessment of Infiltration Rate under Different Drylands Types in Unter-Iwes Subdistrict Sumbawa Besar, Indonesia

Assessment of infiltration rate for each type of soil in dryland  areas need to do to get an idea of ??crop water requirement. The research objective was to analyze  the infiltration rate on a various landuse, and the factors that affect the infiltration rate. Infiltration rate measurements were carried out on dryland areas of Unter Iwes District, Sumbawa regency; using the double ring infiltrometer. The undisturbed soil sample were used ??to determine physical characteristics of soil. The results showed that infiltration rate as high as 45.10 cm.h-1 and infiltration volume as high as 41.82 cm3 on rainfed landuse (it is the very-fast infiltration), the infiltration rate as low as 17.70 cm.h-1 and infiltration volume as low as 17.58 cm3 on ‘Tegalan” landuse (it is the fast infiltration). Factors influencing infiltration are soil type, soil organic matter, porosity, bulk density, specific gravity and initial soil moisture content. Keywords: Infiltration, drylan

Elliott County - Place Names

Place names of Elliott County, Kentucky

Biomedical research publications: 1980 - 1982

Publications concerning the major physiological and psychological problems encountered by man when he undertakes space flight are listed. Nine research areas are included: cardiovascular deconditioning, motion sickness, bone alterations, muscle atrophy, blood cell alterations, fluid and eletrolyte changes, radiation effects and protection, behavior and performance, and general biomedical research

Kaleidoscope⁶: 400 students, 16 ensembles, 75 minutes, October 14, 2017

Fox Cities Performing Arts Center, Appleton, Wisconsi

Southern College Commencement Program May 3-5, 1991

Program for the seventy-fifth annual commencement at Southern College. The consecration, baccalaureate, commencement, and nursing pinning services took place May 3-5, 1991.https://knowledge.e.southern.edu/commencementprograms/1017/thumbnail.jp