We demonstrate the role of the proximity effect in the thermal hysteresis of superconducting constrictions. From the analysis of successive thermal instabilities in the transport characteristics of micron-size superconducting quantum interference devices with a well-controlled geometry, we obtain a complete picture of the different thermal regimes. These determine whether or not the junctions are hysteretic. Below the superconductor critical temperature, the critical current switches from a classical weak-link behavior to one driven by the proximity effect. The associated small amplitude of the critical current makes it robust with respect to the heat generation by phase slips, leading to a nonhysteretic behavior.

To keep the concept of a safe food supply to the consumers, animal feed industries world over are showing an increasing interest in the direct-fed microbials (DFM) for improved animal performance in terms of growth or productivity. This becomes all the more essential in a situation, where a number of the residues of antibiotics and/or other growth stimulants reach in milk and meat with a number of associated potential risks for the consumers. Hence, in the absence of growth stimulants, a positive manipulation of the rumen microbial ecosystem to enhance the feedstuff utilization for improved production efficiency by ruminants has become of much interest to the researchers and entrepreneurs. A few genera of live microbes (i.e., bacteria, fungi and yeasts in different types of formulations from paste to powder) are infrequently used as DFM for the domestic ruminants. These DFM products are live microbial feed supplements containing naturally occurring microbes in the rumen. Among different DFM possibilities, anaerobic rumen fungi (ARF) based additives have been found to improve ruminant productivity consistently during feeding trials. Administration of ARF during the few trials conducted, led to the increased weight gain, milk production, and total tract digestibility of feed components in ruminants. Anaerobic fungi in the rumen display very strong cell-wall degrading cellulolytic and xylanolytic activities through rhizoid development, resulting in the physical disruption of feed structure paving the way for bacterial action. Significant improvements in the fiber digestibility were found to coincide with increases in ARF in the rumen indicating their role. Most of the researches based on DFM have indicated a positive response in nutrient digestion and methane reducing potential during in vivo and/or in vitro supplementation of ARF as DFM. Therefore, DFM especially ARF will gain popularity but it is necessary that all the strains are thoroughly studied for their beneficial properties to have a confirmed ?generally regarded as safe? status for ruminants.authorsversionPeer reviewe

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Experiments were conducted to elucidate the effect of host density on sex ratio of parasitoid offspring, using Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) and its endoparasitoid Campoletis chlorideae Uchida (Hymenoptera: Ichneumonidae). The sex ratio of Campoletis chlorideae was female-biased showing a linear decrease with increasing parasitoid density at fixed host densities. However, with more hosts available, the number of parasitoids emerging increased, stabilising after a density of 32 hosts per parasitoid. To obtain a female-biased sex ratio, a low density of parasitoids should be released at a recommended site.

We demonstrate control of the thermal hysteresis in superconducting constrictions by adding a resistive shunt. In order to prevent thermal relaxation oscillations, the shunt resistor is placed in close vicinity of the constriction, making the inductive current-switching time smaller than the thermal equilibration time. We investigate the current-voltage characteristics of the same constriction with and without the shunt-resistor. The widening of the hysteresis-free temperature range is explained on the basis of a simple model. INTRODUCTIONA superconducting weak-link (WL), such as a constriction, between two bulk superconductors is of interest for its Josephson junction-like properties and subsequent application to micron size superconducting quantum interference devices (µ-SQUIDs) [1,2]. The latter can be used in probing magnetism at small scales [3][4][5][6]. Hysteresis present in current-voltage characteristics (IVCs) is a limiting factor in WL-based SQUIDs. In a hysteretic IVC when the current is ramped up from zero, the device typically switches to a non-zero voltage state at the critical current I c . The subsequent current ramp-down gives a switching to zero-voltage state at a smaller current, called re-trapping current I r . Hysteresis in IVCs is seen at low temperatures and disappears above a crossover temperature T h as I c and I r meet [7][8][9]. In a conventional tunnel-barrier type Josephson-junction, hysteresis arises from large junction capacitance and can be eliminated by adding a shunt-resistor in parallel to the junction [1,10]. The effect of the shunt resistor on nano-wire based WL devices was modeled recently using resistively and capacitively shunted junction (RCSJ) model with an effective capacitive time [11]. The hysteresis in similar devices is well understood using the thermal model [12]. The hysteresis in WLs is due to local Joule-heating [13,14], which gives rise to a self-sustained resistive hot-spot in the WL region, even below I c .Eliminating thermal hysteresis in WLs has been the subject of intense research in the past years. A normal metal shunt directly on top of the constriction [15][16][17] has been tried, but it affects both the superconductivity and thermal properties in a way that depends on the interface transparency. Using a bilayer with a superconductor (that can locally etched with a Focussed Ion Beam) covering a normal metal film allows one to obtain a WL that is also a good thermal bath [18]. A parallel shunt resistor far away from the WL [19] is more flexible approach, but it gives rise to relaxation oscillations due to large inductive time for switching of the current between the WL and the shunt. The performance of such SQUIDs with a distant shunt-resistor is eventually similar to that of the hysteretic ones [3,19]. A systematic study of the ability of a parallel shunt in preventing both the thermal runaway and hysteresis is thus highly desirable.The role of a shunt-resistor can be understood using a simple quasi-static thermal model discussed by Tinkham et al. [12...