Thermoelectric performance of granular semiconductors

We study thermoelectric properties of granular semiconductors with weak tunneling conductance between the grains, g_t < 1. We calculate the thermopower and figure of merit taking into account the shift of the chemical potential and the asymmetry of the density of states in the vicinity of the Fermi surface due to n- or p-type doping in the Efros-Shklovskii regime for temperatures less than the charging energy. We show that for weakly coupled semiconducting grains the figure of merit is optimized for grain sizes of order 5nm for typical materials and its values can be larger than one. We also study the case of compensated granular semiconductors and show that in this case the thermopower can be still finite, although two to three orders of magnitude smaller than in the uncompensated regime.Comment: 4 pages, 4 figure

Thermoelectric performance of weakly coupled granular materials

We study thermoelectric properties of inhomogeneous nanogranular materials for weak tunneling conductance between the grains, g_t < 1. We calculate the thermopower and figure of merit taking into account the shift of the chemical potential and the asymmetry of the density of states in the vicinity of the Fermi surface. We show that the weak coupling between the grains leads to a high thermopower and low thermal conductivity resulting in relatively high values of the figure of merit on the order of one. We estimate the temperature at which the figure of merit has its maximum value for two- and three-dimensional samples. Our results are applicable for many emerging materials, including artificially self-assembled nanoparticle arrays.Comment: 4 pages, 3 figure

Draft genome sequence of Lactobacillus plantarum 2025

A draft genome sequence of Lactobacillus plantarum 2025 was derived using Ion Torrent sequencing technology. The total size of the assembly (3.33 Mb) was in agreement with the genome sizes of other strains of this species. The data will assist in revealing the genes responsible for the specific properties of this strain

Development of technology for deposition of thick copper layers onto ceramic substrates applied in power electronics

The basic element of the design of a power module is a metallized ceramic substrate. In this work, the formation of metallization coatings by the method of thermal transfer of metallization pastes (Mo-Mn-Si + binder) for alumina and aluminum nitride ceramics was carried out. The fixing of the metallization coating on the ceramic substrate was performed by firing at a temperature of 1320 °C. The subsequent deposition of the copper layer was carried out by the method of cold gas-dynamic spraying (CGDS) followed by annealing of the deposited coating. For high-quality adhesion, the optimum annealing temperature was 1000 °C

Spatial distribution of breeding Pied Flycatchers Ficedula hypoleuca in respect to their natal sites

Study of philopatry and dispersal of pied flycatchers Ficedula hypoleuca was launched on the Courish Spit (SE Baltic) in 1981. Since then, ca. 9,000 nestlings were ringed at different sites in the Russian part of the Courish Spit. A total of 557 individuals ringed as pulli were recaptured in subsequent seasons in the study area. Both males and females are more often recaptured in the plots where they were ringed than in other plots. These results were interpreted in the framework of the hypothesis forwarded by Löhrl (1959) and supported by Berndt & Winkel (1979). These authors suggested that cavity nesters (pied flycatchers and collared flycatchers F. albicollis) imprint their future local breeding area during the period of postfledging exploration. Birds that survive until the next spring, return to these imprinted areas to breed. A similar study done by Sokolov et al. (1984) on the Courish Spit in an open nesting species, the chaffinch Fringilla coelebs, confirmed this finding. We assumed that juvenile pied flycatchers disperse for varying distances during their postfledging movements and imprint a local area, some 1–5 kilometres in diameter. This area is the goal of their migration next spring. It is suggested that in spring, yearlings are non–randomly distributed in respect to the area they have imprinted as juveniles. Recently, Vysotsky (2000, 2001) re–analysed the same data on philopatry of pied flycatchers on the Courish Spit and forwarded an alternative hypothesis. He suggests that juveniles, both males and females, do not imprint any local area during the postfledging period, but are distributed randomly across the area of several dozens of kilometres in spring. Vysotsky was able to show that distribution of distances of natal dispersal did not differ from the random pattern the study plot which was an 8.5 km long line of nest boxes along the Courish Spit. The aim of this study was to test these two alternative hypotheses. To do so, we set up nine new study plots in 2000. Over 800 nest–boxes were made available for the birds (in addition to the old 400) in the 44 km long area. We recaptured pied flycatchers returning for breeding during four years, 2000–2003. The distribution of natal dispersal distances was compared with the null model which assumes that pied flycatchers settle randomly in the study area. We took all nest boxes from which pied flycatchers successfully fledged in a particular year and all next boxes where we were able to capture either a male or a female in the subsequent year, and calculated the distances between each pair of such nest boxes. Simulations were run separately for each sex. Theoretical distributions already include control efficiency. If some nest boxes were not checked in some year, or if we failed to capture one or both members of a breeding pair, we did not include this nest box in the model. Some birds could settle outside the study plot. Therefore, the theoretical distribution may underestimate the actual range of natal dispersal, but is unlikely to overestimate it. The number of females ringed as nestlings and recaptured as one–year–old birds was 43. The distribution of their natal distances (mean 6,8 km, SE = 0,81; median 5,4 km) was not significantly different from the pattern predicted by the null model (Wilcoxon matched pairs test: z = 1,25; p = 0,21). Conversely, males settled significantly closer to their natal nest box (n = 83; mean 4,3 km, SE = 0,57; median 2,5 km) than predicted by the model (Wilcoxon matched pairs test: z = 2,45; p = 0,014). For example, 24% of males settle within one km from their natal site, as compared with 7% predicted by the model. Males are found with a greater than chance probability within the 7 km zone around their natal site. The hypothesis by Vysotsky (2000) can thus be rejected for pied flycatcher males. Pied flycatcher females are known to settle at larger distances from their natal nest box. The very fact that were controlled 83 males and only 43 females suggests, assumed that sex ratio at fledging is close to being equal and that true survival rates during the first year of life do not differ greatly between the sexes, that many females emigrated from of our study plot. This does not mean that juvenile females do not imprint a home area during the postfledging period, as suggested by Vysotsky (2000). We think that the reason for this is not the inadequate navigational ability of the females but the fact that they were attracted by a prospecting male at some distance from their migratory destination and settle there. Such intercepting was suggested by Fedorov (1996) for Acrocephalus warblers, and it may exist in other migratory passerines. This is supported by the data on natal site fidelity from Spain which show that in Spanish pied flycatcher populations, recruitment rate did not differ between female and male juveniles (Potti & Montalvo, 1991). Females from these southern populations have a limited chance to be attracted by prospecting males in even more southern areas

Simulation design of PNL device for determining the spatial position of hydraulic fractures in three-dimensional space

The usage of modeling techniques allows to optimize the materials and construction of the neutron well logging apparatus and synthesized the recorded signal. This study focuses on modeling the construction of PNL device for determining the spatial position of hydraulic fractures in three-dimensional space. We used mathematical modeling by Monte Carlo method. PNL logs were synthesized, and it allowed to restore position of hydraulic fracture. The difference between angels simulated and the resulting equaled 3 degree, which confirms the possibility of using this technique

Development of multisector pulsed neutron logging tool constructional parts

© 2016,International Journal of Pharmacy and Technology. All rights reserved.This paper focuses on the results of mathematical modeling aimed to construct multisector pulsed neutron logging (PNL) tool,which can be used to locate the cracks that are formed during hydraulic fracturing operations. This project resulted in a model of multisector PNL tool containing 6 detectors placed in such a way that they are equidistant from the source. This paper also presents:a. optimal collimation design providingdetection of neutronsfrom specific formations;b. model allowingto assess the quality of collimation in multisector logging tools; c. optimal detector configuration for the multisector PNL tool. The project results have also shown the possibility of increasing the number of registered thermal neutronsby introducing special constructional parts into the PNL tool design,allowing to changedirection of the neutron flux from the source into the area adjacent to detection units. Consequently,special constructional parts for the multisector PNL toolwere modeled to increase thenumber of neutrons recorded and determine the azimuth of the hydraulic fractures

Mentoring as a Predominant Factor Affecting Well-Being of Older People

The authors of the paper studied the state of well-being of older people who retired and stop working at the company they have worked for over 20 years. The survey provided some useful insights into the problem with the reference to three samples of 10 older people from each group: 1) older people who retired and keep in touch with the previous organisation; 2) older people who retired and continue working at the company as consultants, supervisors, experts, mentors etc.; 3) older people who retired and work in another enterprise and lost the touch with the previous organisation. Retired people took part in present research by completing a questionnaire survey. A set of data was examined by being compared to reveal the state of older people’s well-being criteria predominance in the various sample groups

Study of drying process in full-size core by nuclear magnetic resonance method

The paper describes the results of study of the nuclear magnetic resonance (NMR) signal distribution along the axis of full-size core depending on the time of its extraction from the core tube. It was detected the presence of thin interlayers characterized by the significant heterogeneity in the distribution of the NMR signal amplitude. This fact demonstrates the need to develop appropriate criteria when selecting the standard samples for the study of reservoir properties and creation of relationships between petrophysical parameters. It was conducted the study of kinetic of NMR signal loss during the period in about 20 days from the time of core material extraction from the well. The experiment showed the heterogeneity in the distribution of the characteristics of the fluid evaporation process along the core. Two types of kinetic dependencies were revealed. Form one of them is nearly exponential dependence. Another form characterized by anomalous behavior consisting in that at the initial time part the fluid evaporation from the core is carried out slowly and only after about 150 hours it is observed the acceleration of the evaporation process and the transition of the kinetic curve to exponential type. It is suggested that such behavior of the kinetic dependence may be due either to the heterogeneity in the distribution of pores by core volume in the study area or the shape of pores, for example, the presence of dead-end pores