Nuclear spin cooling by helicity-alternated optical pumping at weak magnetic fields in nn-GaAs

The spin dynamics of localized donor-bound electrons interacting with the nuclear spin ensemble in $n$-doped GaAs epilayers is studied using nuclear spin polarization by light with modulated circular polarization. We show that the observed build-up of the nuclear spin polarization is a result of competition between nuclear spin cooling and nuclear spin warm-up in the oscillating Knight field. The developed model allows us to explain the dependence of nuclear spin polarization on the modulation frequency and to estimate the equilibration time of the nuclear spin system that appears to be shorter than the transverse relaxation time $T_2$ determined from nuclear magnetic resonance.Comment: Several improvements to v1, 7 pages, 5 figures, corrected list of ref

Sequence Stratigraphy and Onlap History of the Donets Basin, Ukraine: Insight into Carboniferous Icehouse Dynamics

The degree to which Permo-Carboniferous cyclothemic successions archive evidence for long-term variations in ice volume during the Late Paleozoic Ice Age is insufficiently resolved. Here we develop the sequence stratigraphy and onlap-offlap history for a 33-my interval of the Carboniferous using the U-Pb calibrated succession of the Donets Basin, Ukraine, in order to assess the relationship between sea-level, high-latitude changes in glacial extent, and climate. Integrated subsurface and outcrop data permit meter-scale correlation of 242 biostratigraphically constrained limestones and coals, and in turn individual cyclothems, across ~250 km of the Donets Basin. Rapid uniform subsidence and basinwide continuity of marker beds indicate Pennsylvanian deposition under relatively stable tectonic conditions. Three scales of sequences (avg. durations of ~140 ky, ~480 ky and 1.6 my) are recognized on the basis of stratigraphic stacking patterns and basinwide architecture of marine to terrestrial facies assemblages. The hierarchy of sequences and the geographic and stratigraphic positions of shifts in base-level sensitive facies across the Donets ramp permit the construction of an onlap-offlap history at a sub-400 ky scale. Major sea-level lowstands occur across the mid-Carboniferous boundary and during the early Moscovian. These lowstands coincide with glacial maxima inferred from high-latitude glacigenic deposits. The middle to late Pennsylvanian is characterized by a stepwise onlap, culminating in an earliest Gzhelian highstand, suggesting contraction of Carboniferous ice sheets prior to the initiation of Early Permian glaciation. The stratigraphic position of climate sensitive facies within individual Donets cyclothems indicates a turnover from seasonal sub-humid or semi-arid climate to everwet conditions during the late lowstand and maximum ice sheet accumulation. Comparison of the stratigraphic and aerial distribution of coals and evaporites in the Donets Basin with the onlap-offlap history further indicates everwet conditions during lowstands and inferred glacial maxima and drier climate during onlap and inferred ice sheet contraction at the intermediate (~0.8 to 1.6 my) and long (106 yr) time-scales. Taken together, the relationship between inferred climate and glacioeustasy suggests a likely teleconnection between high-latitude ice sheet behavior and low-latitude atmospheric dynamics

Differentiating soils from arable and fallow land using spectrometry

In this study, we analyse soil system responses-in particular, the colours of soils resulting from different types of land use (arable land and residential areas) caused by the construction of an ancient boundary rampart near a multilayer monument dating from between prehistory and the Middle Ages within the boundaries of the Bosporus Kingdom (Eastern Crimea)-in an area of modern and ancient (4th–2nd centuries BC) land use (Northwestern Crimea

ФОРМУВАННЯ ГАЗОМЕТАЛЕВОГО ПОТОКУ В УМОВАХ «ХІМІЧНОГО» ВАКУУМУ У СТАЛЕВИПУСКНОМУ КАНАЛІ

The results of laboratory research to determine the hydro-gas-dynamic patterns the formation of gas-metal flow at an tapping from an oxygen converter to steel ladle are given due to the injection of subsonic argon jets into the melt flow through nozzles located in the steel-tapping channel.Using the method of low-temperature simulation, determined the influence of design parameters of the proposed design of a two-chamber steel-tapping channel (length of the reaction zone, the number and location of gas nozzles) and gas consumption on the degree of organization and protection of the gas-liquid flow (GLF) when the gas blowing into the working space of the steel-tapping channel.Was obtained mathematical relation characterizing the mutual influence on the opening angle of the GLF between of the relative length of the "reaction zone" (x) and the gas flow rate through the nozzle. It is shown that when the length of the "reaction zone" decreases, an extremum occurs at lower gas consumption, and the value of "subcritical" gas consumption has a greater range. So, when the length of the "reaction zone" decreases, an extremum occurs at lower gas consumption, and the value of "subcritical" gas consumption has a greater range.The possibility of retaining the angle of disclosure of the gas-liquid flow (α) in the range of up to 5° with a relative length of the reaction zone of 0,75 has been proved. It is shown that with an increase of α from 1...3° to 10°, the efficiency of the protective action of argon (k) decreases from 0,99 to 0,72. At x = 0,75, the coefficient k is in the range of 0,89...0,99. It is established that when the critical gas flow is exceeded and x = 0,25, the value of α rises to an inadmissible 10...15°.The classification of the purges of the melt flow in the steel-tapping channel is proposed, depending on the angle of inclination of the gas jets relative to the axis of the last (γ) in accordance with which are allocated: the mode of "interruption" (γ > 78°), at which the gas jets unclosed, the formation of the gas-liquid flow does not occur; the mode of "closing" (0  78°), при якому газові струмені розімкнуті, формування газорідинного потоку не відбувається; режим «змикання» (0 < γ < 78°), при якому газові потоки об’єднані, формується газорідинний потік з розвиненою міжфазною поверхнею і високим ступенем організації, та режим «пробою» (γ = 0°), при якому подальше збільшення витрати газу, що перевищує критичну, призводить до пробою і руху газорідинного потоку у дисперсно-кільцевому режимі із зменшенням ступеня організації потоку

Early carboniferous brachiopod faunas from the Baoshan block, west Yunnan, southwest China

38 brachiopod species in 27 genera and subgenera are described from the Yudong Formation in the Shidian-Baoshan area, west Yunnan, southwest China. New taxa include two new subgenera: Unispirifer (Septimispirifer) and Brachythyrina (Longathyrina), and seven new species: Eomarginifera yunnanensis, Marginatia cylindrica, Unispirifer (Unispirifer) xiangshanensis, Unispirifer (Septimispirifer) wafangjieensis, Brachythyrina (Brachythyrina) transversa, Brachythyrina (Longathyrina) baoshanensis, and Girtyella wafangjieensis. Based on the described material and constraints from associated coral and conodont faunas, the age of the brachiopod fauna from the Yudon Formation is considered late Tournaisian (Early Carboniferous), with a possibility extending into earlyViseacutean.<br /

Network Theory Analysis of Antibody-Antigen Reactivity Data: The Immune Trees at Birth and Adulthood

Motivation: New antigen microarray technology enables parallel recording of antibody reactivities with hundreds of antigens. Such data affords system level analysis of the immune system’s organization using methods and approaches from network theory. Here we measured the reactivity of 290 antigens (for both the IgG and IgM isotypes) of 10 healthy mothers and their term newborns. We constructed antigen correlation networks (or immune networks) whose nodes are the antigens and the edges are the antigen-antigen reactivity correlations, and we also computed their corresponding minimum spanning trees (MST) – maximal information reduced sub-graphs. We quantify the network organization (topology) in terms of the network theory divergence rate measure and rank the antigen importance in the full antigen correlation networks by the eigen-value centrality measure. This analysis makes possible the characterization and comparison of the IgG and IgM immune networks at birth (newborns) and adulthood (mothers) in terms of topology and node importance. Results: Comparison of the immune network topology at birth and adulthood revealed partial conservation of the IgG immune network topology, and significant reorganization of the IgM immune networks. Inspection of the antigen importance revealed some dominant (in terms of high centrality) antigens in the IgG and IgM networks at birth, which retain their importance at adulthood

Die Methoden zur Einschätzung der Übertragbarkeit beruflicher Kompetenzen

This paper compares two estimation methods of occupational skills transferability, both theoretically and empirically. The first method is based on Shaw's (1984) study, and the second one is based on Ormiston's (2014) study. The main difference between these two methods is that Shaw's skills transferability is a 'market' approach. It is estimated based on an actual occupational change. On the other hand, Ormiston's skills transferability is a 'skills' approach estimated based on the knowledge, skills, and abilities (KSAs) shared across occupations. Although these two approaches produce very different estimates of occupational skills transferability, both estimates significantly explain the earnings losses of displaced workers. In particular, the displaced workers who find jobs in occupations more similar to their previous jobs, as measured by occupational skills transferability, on average, suffer smaller earnings losses than those who find less similar jobs