Conductivity of Metallic Si:B near the Metal-Insulator Transition: Comparison between Unstressed and Uniaxially Stressed Samples

The low-temperature dc conductivities of barely metallic samples of p-type Si:B are compared for a series of samples with different dopant concentrations, n, in the absence of stress (cubic symmetry), and for a single sample driven from the metallic into the insulating phase by uniaxial compression, S. For all values of temperature and stress, the conductivity of the stressed sample collapses onto a single universal scaling curve. The scaling fit indicates that the conductivity of si:B is proportional to the square-root of T in the critical range. Our data yield a critical conductivity exponent of 1.6, considerably larger than the value reported in earlier experiments where the transition was crossed by varying the dopant concentration. The larger exponent is based on data in a narrow range of stress near the critical value within which scaling holds. We show explicitly that the temperature dependences of the conductivity of stressed and unstressed Si:B are different, suggesting that a direct comparison of the critical behavior and critical exponents for stress- tuned and concentration-tuned transitions may not be warranted

Prospective associations of parental smoking, alcohol use, marital status, maternal satisfaction, and parental and childhood body mass index at 6.5 years with later problematic eating attitudes

Background: Few studies have prospectively investigated whether early-life exposures are associated with pre-adolescent eating attitudes. Objective: The objective of this study is to prospectively investigate associations of parental smoking, alcohol use, marital status, measures of maternal satisfaction, self-reported parental body mass index (BMI) and clinically measured childhood BMI, assessed between birth and 6.5 years, with problematic eating attitudes at 11.5 years. Methods: Observational cohort analysis nested within the Promotion of Breastfeeding Intervention Trial, a cluster-randomised trial conducted in 31 maternity hospitals and affiliated polyclinics in Belarus. Our primary outcome was a Children's Eating Attitudes Test (ChEAT) score ⩾22.5 (85th percentile), an indicator of problematic eating attitudes. We employed multivariable mixed logistic regression models, which allow inference at the individual level. We also performed instrumental variable (IV) analysis using parents' BMIs as instruments for the child's BMI, to assess whether associations could be explained by residual confounding or reverse causation. Subjects: Of the 17 046 infants enrolled between 1996 and 1997 across Belarus, 13 751 (80.7%) completed the ChEAT test at 11.5 years. Results: In fully adjusted models, overweight children at age 6.5 years had a 2.14-fold (95% confidence interval (CI): 1.82, 2.52) increased odds of having ChEAT scores ⩾85th percentile at age 11.5 years, and those who were obese had a 3.89-fold (95% CI: 2.95, 5.14) increased odds compared with normal-weight children. Children of mothers or fathers who were themselves overweight or obese were more likely to score ⩾85th percentile (P for trend ⩽0.001). IV analysis was consistent with a child's BMI causally affecting future eating attitudes. There was little evidence that parental smoking, alcohol use, or marital status or maternal satisfaction were associated with eating attitudes. Conclusion: In our large, prospective cohort in Belarus, both parental and childhood overweight and obesity at 6.5 years were associated with pre-adolescent problematic eating attitudes 5 years later

Critical Behavior of the Conductivity of Si:P at the Metal-Insulator Transition under Uniaxial Stress

We report new measurements of the electrical conductivity sigma of the canonical three-dimensional metal-insulator system Si:P under uniaxial stress S. The zero-temperature extrapolation of sigma(S,T -> 0) ~\S - S_c\^mu shows an unprecidentedly sharp onset of finite conductivity at S_c with an exponent mu = 1. The value of mu differs significantly from that of earlier stress-tuning results. Our data show dynamical sigma(S,T) scaling on both metallic and insulating sides, viz. sigma(S,T) = sigma_c(T) F(\S - S_cT^y) where sigma_c(T) is the conductivity at the critical stress S_c. We find y = 1/znu = 0.34 where nu is the correlation-length exponent and z the dynamic critical exponent.Comment: 5 pages, 4 figure

Threshold Laws for the Break-up of Atomic Particles into Several Charged Fragments

The processes with three or more charged particles in the final state exhibit particular threshold behavior, as inferred by the famous Wannier law for (2e + ion) system. We formulate a general solution which determines the threshold behavior of the cross section for multiple fragmentation. Applications to several systems of particular importance with three, four and five leptons (electrons and positrons) in the field of charged core; and two pairs of identical particles with opposite charges are presented. New threshold exponents for these systems are predicted, while some previously suggested threshold laws are revised.Comment: 40 pages, Revtex, scheduled for the July issue of Phys.Rev.A (1998

Scaling of the Conductivity with Temperature and Uniaxial Stress in Si:B at the Metal-Insulator Transition

Using uniaxial stress to tune Si:B through the metal-insulator transition we find the conductivity at low temperatures shows an excellent fit to scaling with temperature and stress on both sides of the transition. The scaling functions yield the conductivity in the metallic and insulating phases, and allow a reliable determination of the temperature dependence in the critical regions on both sides of the transition

The Effect of Longer-Term and Exclusive Breastfeeding Promotion on Visual Outcome in Adolescence.

Purpose: Breastfeeding may influence early visual development. We examined whether an intervention to promote increased duration and exclusivity of breastfeeding improves visual outcomes at 16 years of age. Methods: Follow-up of a cluster-randomized trial in 31 Belarusian maternity hospitals/polyclinics randomized to receive a breastfeeding promotion intervention, or usual care, where 46% vs. 3% were exclusively breastfed at 3 months respectively. Low vision in either eye was defined as unaided logMAR vision of ≥0.3 or worse (equivalent to Snellen 20/40) and was used as the primary outcome. Open-field autorefraction in a subset (n = 963) suggested that 84% of those with low vision were myopic. Primary analysis was based on modified intention-to-treat, accounting for clustering within hospitals/clinics. Observational analyses also examined the effect of breastfeeding duration and exclusivity, as well as other sociodemographic and environmental determinants of low vision. Results: A total of 13,392 of 17,046 (79%) participants were followed up at 16 years. Low vision prevalence was 19.6% (95% confidence interval [CI]: 17.5, 22.0%) in the experimental group versus 21.6% (19.5, 23.8%) in the control group. Cluster-adjusted odds ratio (OR) of low vision associated with the intervention was 0.92 (95% CI: 0.73, 1.16); 0.88 (95% CI: 0.74, 1.05) after adjustment for parental and early life factors. In observational analyses, breastfeeding duration and exclusivity had no significant effect on low vision. However, maternal age at birth (OR: 1.13, 95% CI: 1.07, 1.14/5-year increase) and urban versus rural residence were associated with increased risk of low vision. Lower parental education, number of older siblings was associated with a lower risk of low vision; boys had lower risk compared with girls (0.64, 95% CI: 0.59,0.70). Conclusions: Exclusive breastfeeding promotion had no significant effect on visual outcomes in this study, but other environmental factors showed strong associations. (ClinicalTrials.gov number, NCT01561612.

Анализ условий размещения на дорогах и характеристик железнодорожных переездов Республики Казахстан

Road traffic accidents of vehicles with a rolling stock of railways lead to the most serious consequences. Many level crossings are places of long delays of vehicles both before and after the traffic. In this case and in many others, the intersections of highways with railways sharply limit the capacity of the highway. Level crossings require the utmost attention of the traffic organization, since they must include not only devices for the movement of cars, but also pedestrian and sidings. Despite the fact that the problem of road traffic accidents at level crossings is not new, research and analysis of statistics in this area continues around the world. The paper considers the level crossings on the Republican highways of the Republic of Kazakhstan. Research has been carried out on ways to improve traffic safety at such crossings. The situation at the level crossings of the roads of Republican significance, as well as possible restrictions and regulatory requirements, have been studied in the paper. The paper presents results of a detailed collection of data at the facilities, which will serve as the basis for the development of a detailed program for improving the regulatory and technical base of the road sector in Kazakhstan to improve the safety of  road transport infrastructure, taking into account existing standards. Recommendations are given for the implementation and generalization of advanced international experience in organizing road traffic at railway crossings, which will contribute to the adaptation of the Republic of Kazakhstan in the context of the development of transport and communications.Дорожно-транспортные происшествия автомобилей с подвижным составом железных дорог приводят к наиболее тяжелым последствиям. Многие железнодорожные переезды являются местами длительных задержек транспортных средств как до, так и после дорожно-транспортного происшествия. Во многих случаях пересечения автомобильных дорог с железнодорожными путями резко ограничивают пропускную способность автомобильной дороги. Железнодорожные переезды требуют самого пристального внимания службы организации дорожного движения, поскольку должны включать не только устройства для движения автомобилей, но также пешеходные и запасные пути. Несмотря на то что проблема дорожно-транспортных происшествий на железнодорожных переездах не является новой, во всем мире продолжаются исследования и анализы статистики в данной области. В статье рассмотрены железнодорожные переезды на республиканских автомобильных дорогах Казахстана. Выполнены исследования направлений повышения безопасности движения на таких переездах. Изучены ситуации на железнодорожных переездах дорог республиканского значения, а также возможные ограничения и нормативные требования. Приведены результаты детального сбора данных на объектах, что послужит основанием для совершенствования нормативно-технической базы дорожного сектора Казахстана по улучшению безопасности дорожно-транспортной инфраструктуры с учетом существующих стандартов. Даны рекомендации по внедрению и обобщению передового международного опыта в организации дорожного движения на железнодорожных переездах, что будет способствовать адаптации Республики Казахстан в условиях развития транспорта и коммуникаций

Влияние сезона года и лактации на состав молока коз–продуцентов биоаналога лактоферрина человека

The seasonal variability of the physicochemical parameters of milk of both ordinary goats and goats producers of a biosimilar human lactoferrin has been established. The average values of the mass fraction of fat, protein, lactose, nonfat milk solids, density index in the second and third quarters were lower than in the first and fourth quarters. At the same time, the difference between the spring-summer and autumn-winter periods in the mass fraction of fat was 25%. In the mass fraction of protein, lactose, nonfat milk solids, density it was 5–7%. Comparative analysis of milk from goats-producers of a biosimilar human lactoferrin of various lactations revealed a number of changes in the physicochemical composition of raw materials in comparison with non-transgenic animals: an increase in the mass fraction of protein by 4–6% (P˂0.05), of lactose by 2–6 (P˂0.05), nonfat milk solids by 1–6, density by 2–5% (P˂0.05), freezing temperature by 5 and a decrease in the mass fraction of fat by 5–8% (P˂0, 05). At the same time, the indicators of active and titratable acidity of milk were similar in all groups of animals. At the same time, the concentration of human lactoferrin in the milk of producers of the second and third lactation had almost identical seasonal changes in the increase and decrease in the synthesis of lactoferrin in the mammary gland during the year: in the first quarter – 2.88 and 2.97 g/l, in the second – 4.76 and 4.63, in the third – 7.44 and 7.55 and in the fourth – 7.97 and 6.72 with an average annual value of 5.84 and 5.72 g/l, respectively.Установлена сезонная вариабельность физико-химических показателей молока как обычных коз, так и животных–продуцентов биоаналога лактоферрина человека. Средние значения массовой доли жира, белка, лактозы, СОМО, показателя плотности во втором и третьем кварталах были ниже по сравнению с первым и четвертым. При этом разница между весенне-летним и осенне-зимним периодами в массовой доле жира составила 25%, в массовой доле белка, лактозы, СОМО, плотности – 5–7%. Сравнительный анализ молока коз–продуцентов биоаналога лактоферрина человека различных лактаций позволил выявить ряд изменений в физико-химическом составе сырья по сравнению с нетрансгенными животными: увеличение массовой доли белка на 4–6% (P˂0,05), лактозы – на 2–6 (P˂0,05), СОМО – на 1–6, плотности – на 2–5 % (P˂0,05), температуры замерзания – на 5 и снижение массовой доли жира на 5–8 % (P˂0,05). При этом показатели активной и титруемой кислотности молока были аналогичны во всех группах животных. В то же время концентрация лактоферрина человека в молоке продуцентов второй и третьей лактации имела практически идентичные сезонные изменения усиления и ослабления синтеза лактоферрина в молочной железе в течение года: в первом квартале – 2,88 и 2,97 г/л, во втором – 4,76 и 4,63, в третьем – 7,44 и 7,55 и в четвертом – 7,97 и 6,72 при среднегодовом значении показателя 5,84 и 5,72 г/л соответственно

Activin signaling as an emerging target for therapeutic interventions

After the initial discovery of activins as important regulators of reproduction, novel and diverse roles have been unraveled for them. Activins are expressed in various tissues and have a broad range of activities including the regulation of gonadal function, hormonal homeostasis, growth and differentiation of musculoskeletal tissues, regulation of growth and metastasis of cancer cells, proliferation and differentiation of embryonic stem cells, and even higher brain functions. Activins signal through a combination of type I and II transmembrane serine/threonine kinase receptors. Activin receptors are shared by multiple transforming growth factor-β (TGF-β) ligands such as myostatin, growth and differentiation factor-11 and nodal. Thus, although the activity of each ligand is distinct, they are also redundant, both physiologically and pathologically in vivo. Activin receptors activated by ligands phosphorylate the receptor-regulated Smads for TGF-β, Smad2 and 3. The Smad proteins then undergo multimerization with the co-mediator Smad4, and translocate into the nucleus to regulate the transcription of target genes in cooperation with nuclear cofactors. Signaling through receptors and Smads is controlled by multiple mechanisms including phosphorylation and other posttranslational modifications such as sumoylation, which affect potein localization, stability and transcriptional activity. Non-Smad signaling also plays an important role in activin signaling. Extracellularly, follistatin and related proteins bind to activins and related TGF-β ligands, and control the signaling and availability of ligands