A method for predicting interfacial freezing of a liquid flowing over a cold surface

Instantaneous thickness of a frozen layer is a function of specific heat, heat of fusion, temperatures, the frozen layer thickness at equilibrium, the thermal conductivity, and heat transfer coefficient. The equation can be evaluated on a desk calculator

Refractive Index Effects on Radiation in an Absorbing, Emitting, and Scattering Laminated Layer

A simple set of equations is derived for predicting temperature radiative energy flow in a two-region semitransparent laminated layer in the limit of zero heat conduction. The composite is heated on its two sides by unequal amounts of incident radiation. The two layers of the composite have different refractive indices, and each material absorbs, emits, and isotropically scatters radiation. The interfaces are diffuse, and all interface reflections are included. To illustrate the thermal behavior that is readily calculated from the equations, typical results an given for various optical thicknesses and refractive indices of the layers. Internal reflections have a substantial effect on the temperature distribution and radiative heat flow

Inviscid analysis of jet injection between two moving streams

An analytical method is developed for determining the flow interaction when a two-dimensional jet is injected between two moving streams. The jet is flowing out of channel and is turned as it enters between the external streams. The local velocity variation resulting from the flow interaction provides a static pressure variation along the jet bounding streamlines that is a priori unknown. Hense, the flow must be obtained by coupling the three flow regions (the jet and the free stream on either side) along the jet boundaries. Both external streams have the same total pressure, which is different from that in the jet. The solution is for the condition that the total pressure in the jet does not differ from the free-stream value by a large amount compared with the free-stream dynamic head. Results are given for the shape of the jet boundaries for various injection configurations

The evolving maintenance of certification process: update on the financial status of the medical boards

Medical board organizations have accumulated large asset balances, in part due to the monetization of physician board recertification, as well as capital gains in positive investment conditions. Physicians across the country have raised concerns regarding the effectiveness and efficiency of existing recertification processes, to which the American Board of Medical Specialties and independent accreditation boards have responded with newly instituted changes. The present article analyzes the publicly available F990 tax forms of the medical boards in an effort to provide data to the ongoing debate. Although some boards have begun to mobilize assets in recent years, many continue to accumulate wealth. It remains to be seen whether the new recertification programs will bring about change or perpetuate organizational wealth

Sociality Affects REM Sleep Episode Duration Under Controlled Laboratory Conditions in the Rock Hyrax, Procavia capensis.

The rock hyrax, Procavia capensis, is a highly social, diurnal mammal. In the current study several physiologically measurable parameters of sleep, as well as the accompanying behavior, were recorded continuously from five rock hyraxes, for 72 h under solitary (experimental animal alone in the recording chamber), and social conditions (experimental animal with 1 or 2 additional, non-implanted animals in the recording chamber). The results revealed no significant differences between solitary and social conditions for total sleep times, number of episodes, episode duration or slow wave activity (SWA) for all states examined. The only significant difference observed between social and solitary conditions was the average duration of rapid eye movement (REM) sleep episodes. REM sleep episode duration was on average 20 s and 40 s longer under social conditions daily and during the dark period, respectively. It is hypothesized that the increase in REM sleep episode duration under social conditions could possibly be attributed to improved thermoregulation strategies, however considering the limited sample size and design of the current study further investigations are needed to confirm this finding. Whether the conclusions and the observations made in this study can be generalized to all naturally socially sleeping mammals remains an open question

High efficiency deterministic Josephson Vortex Ratchet

We investigate experimentally a Josephson vortex ratchet -- a fluxon in an asymmetric periodic potential driven by a deterministic force with zero time average. The highly asymmetric periodic potential is created in an underdamped annular long Josephson junction by means of a current injector providing efficiency of the device up to 91%. We measured the ratchet effect for driving forces with different spectral content. For monochromatic high-frequency drive the rectified voltage becomes quantized. At high driving frequencies we also observe chaos, sub-harmonic dynamics and voltage reversal due to the inertial mass of a fluxon.Comment: accepted by PRL. To see status click on http://134.2.74.170:88/cnt/cond-mat_0506754.htm

Subcritical Superstrings

We introduce the Liouville mode into the Green-Schwarz superstring. Like massive supersymmetry without central charges, there is no kappa symmetry. However, the second-class constraints (and corresponding Wess-Zumino term) remain, and can be solved by (twisted) chiral superspace in dimensions D=4 and 6. The matter conformal anomaly is c = 4-D < 1. It thus can be canceled for physical dimensions by the usual Liouville methods, unlike the bosonic string (for which the consistency condition is c = D <= 1).Comment: 9 pg., compressed postscript file (.ps.Z), other formats (.dvi, .ps, .ps.Z, 8-bit .tex) available at http://insti.physics.sunysb.edu/~siegel/preprints/ or at ftp://max.physics.sunysb.edu/preprints/siege

Direct current superconducting quantum interferometers with asymmetric shunt resistors

We have investigated asymmetrically shunted Nb/Al-AlO$_x$/Nb direct current (dc) superconducting quantum interference devices (SQUIDs). While keeping the total resistance $R$ identical to a comparable symmetric SQUID with $R^{-1} = R_1^{-1} + R_2^{-1}$, we shunted only one of the two Josephson junctions with $R = R_{1,2}/2$. Simulations predict that the optimum energy resolution $\epsilon$ and thus also the noise performance of such an asymmetric SQUID can be 3--4 times better than that of its symmetric counterpart. Experiments at a temperature of 4.2\,K yielded $\epsilon \approx 32\,\hbar$ for an asymmetric SQUID with an inductance of $22\,\rm{pH}$. For a comparable symmetric device $\epsilon = 110\,\hbar$ was achieved, confirming our simulation results.Comment: 5 pages, 4 figure