2,442 research outputs found
Evidence for a Finite Temperature Insulator
In superconductors the zero-resistance current-flow is protected from
dissipation at finite temperatures (T) by virtue of the short-circuit condition
maintained by the electrons that remain in the condensed state. The recently
suggested finite-T insulator and the "superinsulating" phase are different
because any residual mechanism of conduction will eventually become dominant as
the finite-T insulator sets-in. If the residual conduction is small it may be
possible to observe the transition to these intriguing states. We show that the
conductivity of the high magnetic-field insulator terminating superconductivity
in amorphous indium-oxide exhibits an abrupt drop, and seem to approach a zero
conductance at T<0.04 K. We discuss our results in the light of theories that
lead to a finite-T insulator
Characterization of village chicken production performance under scavenging system in Halaba district of southern Ethiopia
Village chicken production was characterized using retrospective and crosssectional methods, where 280 households rearing local chickens in Halaba district of southern Ethiopia were used for data collection. The study revealed that the average flock size was 8.5 chickens (95% CI=7.98 – 9.08). The average number of chickens added to a flock annually was 28.3 birds (95% CI=27.76 – 28.86) while 22.9 birds (95% CI=22.36 – 23.53) were leaving the flock. The majority of the households (77.7%) constructed a wooden perch for night resting of their chickens inside the main house. Scavenging was the major avenue of feeding chickens. Most of the respondents (83.6%) practiced selection in their chicken flocks for females (68.4%) and both sexes (31.6%). The average number of eggs laid by local hen was 13.3 eggs/hen/clutch (95% CI=12.81 – 13.85) and the mean annual egg production was 50.8 eggs per year with an average clutching frequency of 3.8 clutches (95% CI = 3.69 – 3.92). The average clutch length was 26 days (95% CI = 24.92 – 27.08). While the age at first lay of village chickens was 6.53 months (95% CI = 6.45 – 6.61), the average weight at first lay was 0.91 kg (95% CI = 0.87 – 0.96). The mean egg weight for the village chickens was 39.4 g (95% CI = 38.79 – 39.91). The average hatchability of eggs in this study was 83.7 % (95% CI = 81.73 – 85.72). The survival rate of chicks to 6 months of age was 52.3% (95% CI = 51.09 - 53.45). It was concluded that village chicken production was characterized by low input and output system, and scavenging was the dominant form of feeding of village chicken.Key words: Village chicken – Scavenging – Productivity – Clutc
Determinants of Protein Abundance and Translation Efficiency in S. cerevisiae
The translation efficiency of most Saccharomyces cerevisiae genes remains fairly constant across poor and rich growth media. This observation has led us to revisit the available data and to examine the potential utility of a protein abundance predictor in reinterpreting existing mRNA expression data. Our predictor is based on large-scale data of mRNA levels, the tRNA adaptation index, and the evolutionary rate. It attains a correlation of 0.76 with experimentally determined protein abundance levels on unseen data and successfully cross-predicts protein abundance levels in another yeast species (Schizosaccharomyces pombe). The predicted abundance levels of proteins in known S. cerevisiae complexes, and of interacting proteins, are significantly more coherent than their corresponding mRNA expression levels. Analysis of gene expression measurement experiments using the predicted protein abundance levels yields new insights that are not readily discernable when clustering the corresponding mRNA expression levels. Comparing protein abundance levels across poor and rich media, we find a general trend for homeostatic regulation where transcription and translation change in a reciprocal manner. This phenomenon is more prominent near origins of replications. Our analysis shows that in parallel to the adaptation occurring at the tRNA level via the codon bias, proteins do undergo a complementary adaptation at the amino acid level to further increase their abundance
Sensitivity of the superconducting state in thin films
For more than two decades, there have been reports on an unexpected metallic state separating the established superconducting and insulating phases of thin-film superconductors. To date, no theoretical explanation has been able to fully capture the existence of such a state for the large variety of superconductors exhibiting it. Here, we show that for two very different thin-film superconductors, amorphous indium oxide and a single crystal of 2H-NbSe2, this metallic state can be eliminated by adequately filtering external radiation. Our results show that the appearance of temperature-independent, metallic-like transport at low temperatures is sufficiently described by the extreme sensitivity of these superconducting films to external perturbations. We relate this sensitivity to the theoretical observation that, in two dimensions, superconductivity is only marginally stable
Spacecraft with gradual acceleration of solar panels
A spacecraft (8) includes a movable appendage such as solar panels (12) operated by a stepping motor (28) driven by pulses (311). In order to reduce vibration andor attitude error, the drive pulses are generated by a clock down-counter (312) with variable count ratio. Predetermined desired clock ratios are stored in selectable memories (314a-d), and the selected ratio (R) is coupled to a comparator (330) together with the current ratio (C). An up-down counter (340) establishes the current count-down ratio by counting toward the desired ratio under the control of the comparator; thus, a step change of solar panel speed never occurs. When a direction change is commanded, a flag signal generator (350) disables the selectable memories, and enables a further store (360), which generates a count ratio representing a very slow solar panel rotational rate, so that the rotational rate always slows to a low value before direction is changed. The principles of the invention are applicable to any movable appendage
A Survey on Approximation Mechanism Design without Money for Facility Games
In a facility game one or more facilities are placed in a metric space to
serve a set of selfish agents whose addresses are their private information. In
a classical facility game, each agent wants to be as close to a facility as
possible, and the cost of an agent can be defined as the distance between her
location and the closest facility. In an obnoxious facility game, each agent
wants to be far away from all facilities, and her utility is the distance from
her location to the facility set. The objective of each agent is to minimize
her cost or maximize her utility. An agent may lie if, by doing so, more
benefit can be obtained. We are interested in social choice mechanisms that do
not utilize payments. The game designer aims at a mechanism that is
strategy-proof, in the sense that any agent cannot benefit by misreporting her
address, or, even better, group strategy-proof, in the sense that any coalition
of agents cannot all benefit by lying. Meanwhile, it is desirable to have the
mechanism to be approximately optimal with respect to a chosen objective
function. Several models for such approximation mechanism design without money
for facility games have been proposed. In this paper we briefly review these
models and related results for both deterministic and randomized mechanisms,
and meanwhile we present a general framework for approximation mechanism design
without money for facility games
Extreme Sensitivity of the Superconducting State in Thin Films
All non-interacting two-dimensional electronic systems are expected to
exhibit an insulating ground state. This conspicuous absence of the metallic
phase has been challenged only in the case of low-disorder, low density,
semiconducting systems where strong interactions dominate the electronic state.
Unexpectedly, over the last two decades, there have been multiple reports on
the observation of a state with metallic characteristics on a variety of
thin-film superconductors. To date, no theoretical explanation has been able to
fully capture the existence of such a state for the large variety of
superconductors exhibiting it. Here we show that for two very different
thin-film superconductors, amorphous indium-oxide and a single-crystal of
2H-NbSe2, this metallic state can be eliminated by filtering external
radiation. Our results show that these superconducting films are extremely
sensitive to external perturbations leading to the suppression of
superconductivity and the appearance of temperature independent, metallic like,
transport at low temperatures. We relate the extreme sensitivity to the
theoretical observation that, in two-dimensions, superconductivity is only
marginally stable.Comment: 10 pages, 6 figure
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