Quantum Transport in Ladder-Type Networks: Role of nonlinearity, topology and spin

We investigate quantum transport of electrons, phase solitons, etc. through mesoscopic networks of zero-dimensional quantum dots. Straight and circular ladders are chosen as networks with each coupled with three semi-infinite leads (with one incoming and the other two outgoing). Two transmission probabilities (TPs) as a function of the incident energy $\epsilon$ show a transition from anti-phase aperiodic to degenerate periodic spectra at the critical energy $\epsilon_c$ which is determined by a bifurcation point of the bulk energy dispersions. TPs of the circular ladder depend only on the parity of the winding number. Introduction of a single missing bond (MB) or missing step doubles the period of the periodic spectra at $\epsilon>\epsilon_c$ . Shift of the MB by lattice constant results in a striking switching effect at $\epsilon<\epsilon_c$. In the presence of the electric-field induced spin-orbit interaction (SOI), an obvious spin filtering occurs against the spin-unpolarized injection. Against the spin-polarized injection, on the other hand, the spin transport shows spin-flip (magnetization reversal) oscillations with respect to SOI. We also show a role of soliton in the context of its transport through the ladder networks.Comment: 10 pages, 16 figure

Содержание цезия-137 в почвенном покрове Центрального и Южного Таджикистана

The content of cesium-137 in the soil cover of the central and southern parts of Tajikistan was studied. The study area of the regions of the republic is about 45,000 km2. 92 soil samples from the Central and Southern parts of the republic were collected from cultivated and uncultivated fields to a depth of 25 cm from the ground surface. Each sample at the sampling point was cleared of stones, roots and other inclusions. The sample was dried to an air-dry state, crushed and sieved through a sieve with a hole diameter of 2 mm. When measuring the samples, we used a standard 1 L Marinelli beaker. Measurements of the specific activity of cesium-137 in soil samples were carried out on a gamma spectrometer based on highly pure germanium. The maximum content of cesium-137 was observed in soil sample No. 1 of the Kamarob area of the Rasht district, which specific activity in the sample is 148 Bq / kg. The minimum specific activity of cesium-137 is observed in soil samples from the Tajikabad district. The dependence of the concentration of cesium-137 on the topography in the region under study has been established. In some of the investigated samples, the cesium-137 isotope was not detected (sample no. 2 from the Ayvaj area of the Shahritus district and sample no. 4 from the Farkhor district). The dynamics of the distribution of cesium-137 on the soils of uncultivated fields and soils of cultivated fields of the Khatlon region of Tajikistan has been studied. It was found that the content of the isotope of cesium-137 in the treated fields differs from the untreated ones. It has been determined that in the soils of cultivated lands, the content of cesium-137 is concentrated at a depth of 20-25 cm. At the foot of the mountains and clay soils, a relatively high content of the isotope of cesium-137 is observed in comparison with plains and sandy soils.Проведено исследование содержание цезия-137 в почвенном покрове Центрального и Южного Таджикистана. Площадь территории исследования регионов республики составляет около 45 000 км2. Традиционным методом отобрано 92 образца почв Центрального и Южного Таджикистана из обрабатываемых и необрабатываемых полей до глубины 25 см от поверхности земли. Каждую пробу в точке отбора очищали от камней, корней и других включений. Пробу высушивали до воздушносухого состояния, измельчали и просеивали через сито диаметром отверстий 2 мм. При измерении проб использовали стандартный сосуд «Маринелли» объёмом 1 л. Измерения удельной активности цезия-137 в пробах почв проводились на гамма-спектрометре на основе особо чистого германия. Максимальное содержание цезия-137 наблюдается в пробе почвы № 1 местности Камароб Раштского района, удельная активность в которой составляет 147,5 Бк/кг. Минимальная удельная активность цезия-137 наблюдается в пробах почв местности Таджикабад. Установлена зависимость содержания цезия-137 от рельефа местности в исследуемом регионе. В некоторых исследуемых пробах изотоп цезий-137 не был обнаружен (проба № 2 из пустыни Айвадж района Шахритус и проба № 4 из района Фархор). Исследовано распределение цезия-137 на почвах необрабатываемых полей и почвах обрабатываемых полей Хатлонской области Таджикистана. Обнаружено, что содержание изотопа цезия-137 на обрабатываемых полях отличается от необрабатываемых. Определено, что в почвах обрабатываемых земель цезий-137 концентрируется на глубине до 20–25 см. У подножия гор и в глинистых почвах наблюдается относительно высокое содержание изотопа цезия-137 по сравнению с равнинами и песчаными почвами

Gene duplication and fragmentation in the zebra finch major histocompatibility complex

BACKGROUND: Due to its high polymorphism and importance for disease resistance, the major histocompatibility complex (MHC) has been an important focus of many vertebrate genome projects. Avian MHC organization is of particular interest because the chicken Gallus gallus, the avian species with the best characterized MHC, possesses a highly streamlined minimal essential MHC, which is linked to resistance against specific pathogens. It remains unclear the extent to which this organization describes the situation in other birds and whether it represents a derived or ancestral condition. The sequencing of the zebra finch Taeniopygia guttata genome, in combination with targeted bacterial artificial chromosome (BAC) sequencing, has allowed us to characterize an MHC from a highly divergent and diverse avian lineage, the passerines. RESULTS: The zebra finch MHC exhibits a complex structure and history involving gene duplication and fragmentation. The zebra finch MHC includes multiple Class I and Class II genes, some of which appear to be pseudogenes, and spans a much more extensive genomic region than the chicken MHC, as evidenced by the presence of MHC genes on each of seven BACs spanning 739 kb. Cytogenetic (FISH) evidence and the genome assembly itself place core MHC genes on as many as four chromosomes with TAP and Class I genes mapping to different chromosomes. MHC Class II regions are further characterized by high endogenous retroviral content. Lastly, we find strong evidence of selection acting on sites within passerine MHC Class I and Class II genes. CONCLUSION: The zebra finch MHC differs markedly from that of the chicken, the only other bird species with a complete genome sequence. The apparent lack of synteny between TAP and the expressed MHC Class I locus is in fact reminiscent of a pattern seen in some mammalian lineages and may represent convergent evolution. Our analyses of the zebra finch MHC suggest a complex history involving chromosomal fission, gene duplication and translocation in the history of the MHC in birds, and highlight striking differences in MHC structure and organization among avian lineages