Scaling properties of noise-induced switching in a bistable tunnel diode circuit

Noise-induced switching between coexisting metastable states occurs in a wide range of far-from-equilibrium systems including micro-mechanical oscillators, epidemiological and climate change models, and nonlinear electronic transport in tunneling structures such as semiconductor superlattices and tunnel diodes. In the case of tunnel diode circuits, noise-induced switching behavior is associated with negative differential resistance in the static current-voltage characteristics and bistability, i.e., the existence of two macroscopic current states for a given applied voltage. Noise effects are particularly strong near the onset and offset of bistable current behavior, corresponding to bifurcation points in the associated dynamical system. In this paper, we show that the tunnel diode system provides an excellent experimental platform for the precision measurement of scaling properties of mean switching times versus applied voltage near bifurcation points. More specifically, experimental data confirm that the mean switching time scales logarithmically as the 3/2 power of voltage difference over an exceptionally wide range of time scales and noise intensities.Comment: 9 pages, 9 figures, accepted manuscript for publication in the European Physical Journal B, Topical Issue: Non-Linear and Complex Dynamics in Semiconductors and Related Material

High-performance light-weight electrodes for hydrogen-oxygen fuel cells

High performance light weight electrodes for hydrogen oxygen fuel cell

Numerical solution of the time-dependent compressible Navier-Stokes equations in inlet regions

The results of a study to determine the effects of compressibility on the viscous flow through channels that have straight, parallel walls are presented. Two channel configurations are considered, the flow between two semi-infinite flat plates with uniform flow prescribed at the inlet plane and a cascade of semi-infinite flat plates with uniform flow introduced upstream. The flow field is modeled by using the time dependent, compressible Navier-Stokes equations. Time dependent solutions are obtained by using an explicit finite difference technique which advances the pressure on near field subsonic boundaries such that accurate steady state solutions are obtained. Steady state results at Reynolds number 20 and 150 are presented for Mach numbers between 0.09 and 0.36 and compared with the incompressible solutions of previous studies

A Limited Habitable Zone for Complex Life

The habitable zone (HZ) is commonly defined as the range of distances from a host star within which liquid water, a key requirement for life, may exist on a planet's surface. Substantially more CO2 than present in Earth's modern atmosphere is required to maintain clement temperatures for most of the HZ, with several bars required at the outer edge. However, most complex aerobic life on Earth is limited by CO2 concentrations of just fractions of a bar. At the same time, most exoplanets in the traditional HZ reside in proximity to M dwarfs, which are more numerous than Sun-like G dwarfs but are predicted to promote greater abundances of gases that can be toxic in the atmospheres of orbiting planets, such as carbon monoxide (CO). Here we show that the HZ for complex aerobic life is likely limited relative to that for microbial life. We use a 1D radiative-convective climate and photochemical models to circumscribe a Habitable Zone for Complex Life (HZCL) based on known toxicity limits for a range of organisms as a proof of concept. We find that for CO2 tolerances of 0.01, 0.1, and 1 bar, the HZCL is only 21%, 32%, and 50% as wide as the conventional HZ for a Sun-like star, and that CO concentrations may limit some complex life throughout the entire HZ of the coolest M dwarfs. These results cast new light on the likely distribution of complex life in the universe and have important ramifications for the search for exoplanet biosignatures and technosignatures.Comment: Revised including additional discussion. Published Gold OA in ApJ. 9 pages, 5 figures, 5 table

Remote sensing of changes in morphology and physiology of trees under stress

Measurements on foliage samples collected from several drought and salt treated plants revealed that leaf thickness decreased with increasing severity of the drought treatment and increased with increasing severity of treatment with NaCl, but remained essentially unaffected by treatment with CaCl2. Airborne data collected by multispectral scanner indicated that false color images provide selective enhancement of a diseased area. Comparison of simulated and actual aerial color and color IR photography revealed that the color renditions of the MSS simulations agreed closely with those of the actual photography

Remote sensing applications in forestry - Remote sensing of changes in morphology and physiology of trees under stress Annual progress report

Remote sensing of changes in morphology and physiology of trees under stres

Understanding the measurement of hunger and food insecurity in the elderly

The elderly are one of the population subgroups at greatest risk for hunger and food insecurity. To date, no accurate measures of this problem have been developed. What is needed are a thorough understanding of the phenomenon, and an assessment of how the elderly perceive and answer items commonly used to measure hunger and food insecurity in other subgroups. In-depth, open-ended interviews were conducted with forty-one low-income urban black and rural white residents of upstate New York. Results suggest a conceptual framework of food insecurity in the elderly with two significant differences from frameworks proposed for younger families: the major role of health problems and physical disabilities, and the impact of personal history on perceptions of food insecurity. In a telephone follow-up (approximately six months after the initial interviews) twenty-four respondents were asked commonly used food insecurity questionnaire items from six different sources. Results suggest that hunger and food insecurity among the elderly can be measured directly. The commonly used measures tested here will help categorize the stages of food insecurity. However, these direct measures might underestimate the prevalence of food insecurity because of a perceived reluctance to report problems with food.

Alfalfa Silage Effect of Storage Methods on Feeding Value and on Preservation of Nutrients

Feeding trials using beef cattle were conducted with baled alfalfa hay and with alfalfa silage stored in the stack, trench, and upright silo. Based upon feed costs at the time of storage, the average feed costs per 100 pounds of gain for the several experiments were as follows: baled hay, $18.70; upright silo,$22.35; trench silo, $30.58; and stack silo,$33.58. The greatly increased costs in the case of the trench and stack were the result of excessive fermentation and spoilage losses because air was not properly excluded. The chemical composition of the dry matter of the various silages was quite similar. However, the spoilage was considerably different in its composition from the edib]e silage. This was especially true where chemical determinations of digestibility were made, the values for the spoiled silage being very low. Dry matter and nutrient losses were determined on hay and the various silages for 1 year\u27s work. The amount of loss was largest when air was not properly excluded (stack and trench). This work emphasizes the need to provide storage for alfalfa silage of a type which will prevent exposure to air for satisfactory preservation of nutrients. In deciding what type of storage to use, the operator should consider this as well as the many other factors related to cost and convenience

Egg Yolk Pigmentation as Influenced by Alfalfa Meal and Various Concentrates

This study was a continuation of testing natural and synthetic materials in the production of deeply pigmented egg yolk. Thus far ß-apo 8\u27 carotenoic acid ethyl ester (BACE) has been the most efficient pigmenter used, followed by ß-apo 8\u27 carotenal (BAC) and then various alfalfa concentrates, alfalfa or corn gluten meal and marigold meals. There has been a tendency for enhanced yolk color when the synthetic pigmenters were fed with alfalfa, suggesting synergism. This study was therefore conducted to determine if fractions of alfalfa meal with little or no xanthophyll would enhance the utilization of pure pigmenting material

Egg Yolk Pigmentation with Dehydrated Alfalfa Meal, Pro-Xan and Xanthophyll-free Freeze Dried Alfalfa Juice

This study concludes a series of tests in which natural and synthetic materials were used to produce deeply pigmented egg yolk. The most efficient pigmenter used was B-apo 8\u27 carotenoic acid ethyl ester followed by 6-apo 8\u27 carotenal, alfalfa concentrates and meals of alfalfa, corn gluten and marigold petals. In this test pure lutein, dehydrated alfalfa meal and Pro-Xan, an alfalfa concentrate, were used as sources of pigments^. The freeze dried alfalfa juice was tested for its possible effect in enhancing the utilization of pure lutein. Caged hens were depleted of body stored pigments by feeding an essentially pigment free, milo-soy diet for 12 months. Pigmenting materials were then added to the milo-soy basal to provide dietary pigment at levels of 10 and 20 ppm as shown in table 1