Multiphoton Transitions in a Spin System Driven by Strong Bichromatic Field

EPR transient nutation spectroscopy is used to measure the effective field (Rabi frequency) for multiphoton transitions in a two-level spin system bichromatically driven by a transverse microwave (MW) field and a longitudinal radio-frequency (RF) field. The behavior of the effective field amplitude is examined in the case of a relatively strong MW field, when the derivation of the effective Hamiltonian cannot be reduced to first-order perturbation theory in w_{1} / w_{rf} (w_{1} is the microwave Rabi frequency, w_{rf} is the RF frequency). Experimental results are consistently interpreted by taking into account the contributions of second and third order in w_{1} / w_{rf} evaluated by Krylov-Bogolyubov-Mitropolsky averaging. In the case of inhomogeneously broadened EPR line, the third-order correction modifies the nutation frequency, while the second-order correction gives rise to a change in the nutation amplitude due to a Bloch-Siegert shift.Comment: 7 pages, 6 figure

What have we already learned from the CMB?

The COBE satellite, and the DMR experiment in particular, was extraordinarily successful. However, the DMR results were announced about 7 years ago, during which time a great deal more has been learned about anisotropies in the Cosmic Microwave Background (CMB). The CMB experiments currently being designed and built, including long-duration balloons, interferometers, and two space missions, promise to address several fundamental cosmological issues. We present our evaluation of what we already know, what we are beginning to learn now, and what the future may bring.Comment: 20 pages, 3 figures. Changes to match version accepted by PAS

Автоматические измерения в металлографии

Quantitative analysis of the structure of metals and alloys is an important part of modern metal science. To obtain quantitative data and build dependencies, metallographic image processing programs are used, oriented both for scientific research and for use in industry. Programs capable of automatically performing metallographic analysis are of great interest to consumers. When advertising such programs, it is often claimed that they allow quantitative analysis of the structure with virtually no time. The purpose of this work was to determine the time spent on quantitative metallographic analysis in some image processing programs presented on the Belarusian market. Connected and unconnected metallographic objects were considered. It is shown that automatic quantitative analysis is possible for unconnected objects (powders, cast iron graphite). The time required is within a minute. For connected objects (structures of metals and alloys after metallographic etching), the time required to detect objects and obtain digital data is 10–40 min or more, depending on the complexity of the object, which is unacceptable for factory laboratories that analyze a large number of samples per shift. Therefore, it is recommended that potential users of metallographic image processing software always require a substantive demonstration of the automatic measurement capabilities of the proposed software.Количественный анализ структуры металлов и сплавов является важной частью современного металловедения. Для получения количественных данных и построения зависимостей используются металлографические программы обработки изображений, ориентированные как на научные исследования, так и для использования в промышленности. Большой интерес у потребителя вызывают программы, способные автоматически проводить металлографический анализ. При рекламе таких программ зачастую утверждается, что они позволяют провести количественный анализ структуры практически без затрат времени. Целью данной работы являлось определение затрат времени на количественный металлографический анализ в некоторых программах обработки изображений, представленных на белорусском рынке. Рассматривались связанные и несвязанные металлографические объекты. Показано, что для несвязанных объектов (порошки, графит чугуна) возможен автоматический количественный анализ; затраты времени при этом составляют в пределах минуты. Для связанных объектов (структуры металлов и сплавов после металлографического травления) затраты времени на обнаружение объектов и получение цифровых данных составляют 10–40 мин и более в зависимости от сложности объекта, что неприемлемо для заводских лабораторий, которые анализируют большое количество образцов за смену. Поэтому потенциальным потребителям программ обработки металлографических изображений рекомендуется всегда требовать предметной демонстрации возможности автоматических измерений предлагаемого программного обеспечения

Woodland in a fluvio-lacustrine environment on the dry Mongolian Plateau during the late Paleocene: Evidence from the mammal bearing Subeng section (Inner Mongolia, PR China)

In the understanding of the global faunal turnover during the Paleocene-Eocene transition, an important role has been attributed to the Asian continent, although the Asian fossil record for this period is still incomplete. Here we present a multidisciplinary study of the Subeng section (Inner Mongolia, P.R. China), integrating sedimentological, stratigraphical and diverse palaeontological data, in order to reconstruct the palaeoenvironment and to enhance the understanding of the late Paleocene communities that once thrived on the Mongolian Plateau. The Subeng section starts with the Maastrichtian Iren Dabasu Formation directly covered by the late Paleocene Nomogen Formation. This Nomogen Formation is composed of typical lacustrine deposits at the base, covered by fluvio-lacustrine deposits at the top. Both types of deposits provided rich ostracod and charophyte assemblages, closest to those of the Naran Member, Naran Bulak Formation of Mongolia. Palynomorphs from the lake sediments suggest a local flora at Subeng more wooded and closed than reported from elsewhere in this region. The fluvio-lacustrine deposits of the Nomogen Formation have yielded a vertebrate fauna especially rich in mammals. The mammal fauna from Subeng is close to that from Bayan Ulan and typical for the Gashatan Asian Land Mammal Age. The presence of reworked pedogenic carbonate nodules and mud aggregates suggests an at least seasonally dry regional climate. Combined sedimentological and palaeontological data suggest the late Paleocene Nomogen Formation at Subeng was an isolated woodland in a fluvio-lacustrine environment, representing a locally humid environment on the semi-arid Mongolian Plateau. The mammal fauna reflects these differences and shows a number of relatives to mammals from the more humid northeastern Chinese biotic province as well as some North American immigrants. © 2006 Elsevier B.V. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Acceptor levels of the carbon vacancy in 4H4H-SiC: combining Laplace deep level transient spectroscopy with density functional modeling

We provide direct evidence that the broad Z$_{1/2}$ peak, commonly observed by conventional DLTS in as-grown and at high concentrations in radiation damaged $4H$-SiC, has two components, namely Z$_{1}$ and Z$_{2}$, with activation energies for electron emission of 0.59 and 0.67~eV, respectively. We assign these components to $\mathrm{Z}_{1/2}^{=}\rightarrow\mathrm{Z}_{1/2}^{-}+e^{-}\rightarrow\mathrm{Z}_{1/2}^{0}+2e^{-}$ transition sequences from negative-$U$ ordered acceptor levels of carbon vacancy (V$_{\mathrm{C}}$) defects at hexagonal/pseudo-cubic sites, respectively. By employing short filling pulses at lower temperatures, we were able to characterize the first acceptor level of V$_{\mathrm{C}}$ on both sub-lattice sites. Activation energies for electron emission of 0.48 and 0.41~eV were determined for $\mathrm{Z}_{1}(-/0)$ and $\mathrm{Z}_{2}(-/0)$ transitions, respectively. Based on trap filling kinetics and capture barrier calculations, we investigated the two-step transitions from neutral to doubly negatively charged Z$_{1}$ and Z$_{2}$. Positions of the first and second acceptor levels of V$_{\mathrm{C}}$ at both lattice sites, as well as $(=\!/0)$ occupancy levels were derived from the analysis of the emission and capture data

THE ANTHOLOGY OF STRESS FRACTURES

The article is devoted, to the history of studying of a problem, of stress fractures. The article raised, questions of terminology and statistics of stress fracture at different times by different authors and. the stage-by-stage scientific accumulation of information on this topic is shown

Effective Field and the Bloch-Siegert Shift at Bihromatic Excitation of Multiphoton EPR

The dynamics of multiphoton transitions in a two-level spin system excited by transverse microwave and longitudinal RF fields with the frequencies w_{mw} and w_{rf}, respectively, is analyzed. The effective time-independent Hamiltonian describing the "dressed" spin states of the "spin + bichromatic field" system is obtained by using the Krylov-Bogoliubov-Mitropolsky averaging method. The direct detection of the time behavior of the spin system by the method of nonstationary nutations makes it possible to identify the multiphoton transitions for resonances w_{0} = w_{mw} + rw_{rf} (w_{0} is the central frequency of the EPR line, r = 1, 2), to measure the amplitudes of the effective fields of these transitions, and to determine the features generated by the inhomogeneous broadening of the EPR line. It is shown that the Bloch-Siegert shifts for multiphoton resonances at the inhomogeneous broadening of spectral lines reduce only the nutation amplitude but do not change their frequencies.Comment: 6 pages, 5 figure

The Dynamics of Zeroth-Order Ultrasensitivity: A Critical Phenomenon in Cell Biology

It is well known since the pioneering work of Goldbeter and Koshland [Proc. Natl. Acad. Sci. USA, vol. 78, pp. 6840-6844 (1981)] that cellular phosphorylation- dephosphorylation cycle (PdPC), catalyzed by kinase and phosphatase under saturated condition with zeroth order enzyme kinetics, exhibits ultrasensitivity, sharp transition. We analyse the dynamics aspects of the zeroth order PdPC kinetics and show a critical slowdown akin to the phase transition in condensed matter physics. We demonstrate that an extremely simple, though somewhat mathematically "singular" model is a faithful representation of the ultrasentivity phenomenon. The simplified mathematical model will be valuable, as a component, in developing complex cellular signaling network theory as well as having a pedagogic value.Comment: 8 pages, 3 figure

Dissipative dynamics of qubits driven by a bichromatic field in the dispersive regime

We study the coherent dynamics of relaxing qubits driven by a bichromatic radiation in the dispersive regime, when detuning of the frequency $\omega_{rf}$ of a longitudinal radiofrequency field from the Rabi frequency $\omega_{1}$ in a transverse microwave field is comparable in magnitude to $\omega_{rf}$ and $\omega_{1}$. We analytically describe this regime beyond the rotating wave approximation and find that the dominant feature of dynamics of qubits is the shift of the Rabi frequency caused by the dynamical Zeeman and Bloch-Siegert-like effects. These fundamental effects can be experimentally separated because, unlike the Bloch-Siegert effect, the dynamical Zeeman effect depends on the detuning sign. Our theoretical results are in a good agreement with the experimental data obtained in pulse EPR for the $E'_{1}$ centers in crystalline quartz.Comment: 11 pages, 4 figure

THE ROLE OF MESOZOIC GEODYNAMIC EVENTS IN FORMATION OF SEDIMENTARY BASINS ON THE FRAMING OF THE EASTERN MONGOL-OKHOTSK OROGENIC BELT

The Mongol-Okhotsk orogenic belt, finally formed in the end of the Mesozoic as a result of later tectonic events, is divided into two flanks: western and eastern. Its formation is obviously due to a regular change in geodynamic events significantly obscured by late tectonic and magmatic processes in the western flank and more clearly defined in the eastern flank from both magmatic and stratified formations. The early changes in geodynamic environment are most clearly determined by the formation of magmatic complexes whose completion is usually accompanied by the strata formation. Stratons framing the eastern flank of the Mongol-Okhotsk orogenic belt in the Mesozoic were formed in sedimentary basins, which are currently isolated to the Krestovkinsky and Ogodzhinsky basins along the southern border and to the Strelkinsky, Malotyndinsky, Toromsky and Udsky basins along the northern border. The deposition environment varied from deep-sea marine to continental. The article attempts to correlate the cross-sections of sedimentary basins on the framing of the eastern Mongol-Okhotsk orogenic belt and considers similarity or difference in their structure, conditions of sedimentation, tectonic positions and dependence of their evolution on geodynamic processes in the regio