Ground state EIT cooling of 171^{171}Yb+^+ ion

The work propose a scheme of deep laser cooling of $^{171}$Yb$^{+}$. The cooling is based on the effect of electromagnetically induced transparency (EIT) in a polychromatic field with three frequency components are resonant to optical transitions of the ^2S_{1/2} \to \, ^2P_{1/2} line. The deep cooling down to the ground motional state in a trap allows for a significant suppression of the second order Doppler shift in frequency standards. Moreover, there is no need to use a magnetic field, which is required for Doppler cooling of $^{171}$Yb$^{+}$ in a field with two-frequency component. The cooling without use of magnetic field is important for deep suppression of quadratic Zeeman shifts of clock transitions from uncontrolled residual magnetic fields

Coherent interaction of laser pulses in a resonant optically dense extended medium under the regime of strong field-matter coupling

Nonstationary pump-probe interaction between short laser pulses propagating in a resonant optically dense coherent medium is considered. A special attention is paid to the case, where the density of two-level particles is high enough that a considerable part of the energy of relatively weak external laser-fields can be coherently absorbed and reemitted by the medium. Thus, the field of medium reaction plays a key role in the interaction processes, which leads to the collective behavior of an atomic ensemble in the strongly coupled light-matter system. Such behavior results in the fast excitation interchanges between the field and a medium in the form of the optical ringing, which is analogous to polariton beating in the solid-state optics. This collective oscillating response, which can be treated as successive beats between light wave-packets of different group velocities, is shown to significantly affect propagation and amplification of the probe field under its nonlinear interaction with a nearly copropagating pump pulse. Depending on the probe-pump time delay, the probe transmission spectra show the appearance of either specific doublet or coherent dip. The widths of these features are determined by the density-dependent field-matter coupling coefficient and increase during the propagation. Besides that, the widths of the coherent features, which appear close to the resonance in the broadband probe-spectrum, exceed the absorption-line width, since, under the strong-coupling regime, the frequency of the optical ringing exceeds the rate of incoherent relaxation. Contrary to the stationary strong-field effects, the density- and coordinate-dependent transmission spectra of the probe manifest the importance of the collective oscillations and cannot be obtained in the framework of the single-atom model.Comment: 10 pages, 8 figures, to be published in Phys. Rev.

Exploring the pre-immune landscape of antigen-specific T cells

Abstract Background Adaptive immune responses to newly encountered pathogens depend on the mobilization of antigen-specific clonotypes from a vastly diverse pool of naive T cells. Using recent advances in immune repertoire sequencing technologies, models of the immune receptor rearrangement process, and a database of annotated T cell receptor (TCR) sequences with known specificities, we explored the baseline frequencies of T cells specific for defined human leukocyte antigen (HLA) class I-restricted epitopes in healthy individuals. Methods We used a database of TCR sequences with known antigen specificities and a probabilistic TCR rearrangement model to estimate the baseline frequencies of TCRs specific to distinct antigens epitopespecificT-cells. We verified our estimates using a publicly available collection of TCR repertoires from healthy individuals. We also interrogated a database of immunogenic and non-immunogenic peptides is used to link baseline T-cell frequencies with epitope immunogenicity. Results Our findings revealed a high degree of variability in the prevalence of T cells specific for different antigens that could be explained by the physicochemical properties of the corresponding HLA class I-bound peptides. The occurrence of certain rearrangements was influenced by ancestry and HLA class I restriction, and umbilical cord blood samples contained higher frequencies of common pathogen-specific TCRs. We also identified a quantitative link between specific T cell frequencies and the immunogenicity of cognate epitopes presented by defined HLA class I molecules. Conclusions Our results suggest that the population frequencies of specific T cells are strikingly non-uniform across epitopes that are known to elicit immune responses. This inference leads to a new definition of epitope immunogenicity based on specific TCR frequencies, which can be estimated with a high degree of accuracy in silico, thereby providing a novel framework to integrate computational and experimental genomics with basic and translational research efforts in the field of T cell immunology

Resonant nonstationary amplification of polychromatic laser pulses and conical emission in an optically dense ensemble of neon metastable atoms

Experimental and numerical investigation of single-beam and pump-probe interaction with a resonantly absorbing dense extended medium under strong and weak field-matter coupling is presented. Significant probe beam amplification and conical emission were observed. Under relatively weak pumping and high medium density, when the condition of strong coupling between field and resonant matter is fulfilled, the probe amplification spectrum has a form of spectral doublet. Stronger pumping leads to the appearance of a single peak of the probe beam amplification at the transition frequency. The greater probe intensity results in an asymmetrical transmission spectrum with amplification at the blue wing of the absorption line and attenuation at the red one. Under high medium density, a broad band of amplification appears. Theoretical model is based on the solution of the Maxwell-Bloch equations for a two-level system. Different types of probe transmission spectra obtained are attributed to complex dynamics of a coherent medium response to broadband polychromatic radiation of a multimode dye laser.Comment: 9 pages, 13 figures, corrected, Fig.8 was changed, to be published in Phys. Rev.

Хирургическое лечение обширной скальпированной раны теменно-затылочной области

In the presented clinical case, we consider the surgical treatment of a 9-year-old girl with an extensive post-traumatic scalp wound in the parieto-occipital region resulting from hair getting into the moving mechanism of a go-kart car and incomplete separation of the scalp in the parieto-occipital region of the head. The early postoperative period (surgical treatment with primary wound closure) was complicated by the development of skin necrosis. An extensive wound defect in the soft tissues of the scalp (up to 150 cm2) was replaced with local related tissues. For this, various methods of plastic surgery were used in different areas of the wound defect: plastic surgery with local tissues, replacement of the defect with a rotated fascio-cutaneous flap and plastic surgery with local tissues using the dosed stretching method. The combined use of these methods made it possible to completely restore full-fledged soft tissues and hair of the injured parieto-occipital region. В представленном клиническом наблюдении рассматривается хирургическое лечение девочки 9 лет с обширной посттравматической скальпированной раной теменно-затылочной области, полученной в результате попадания волос в движущийся механизм автомобиля для картинга и неполного отрыва скальпа теменно-затылочной области головы. Ранний послеоперационный период (хирургическая обработка с первичным ушиванием раны) осложнился развитием некроза кожных покровов. Обширный раневой дефект мягких тканей волосистой части головы (до 150 см2) удалось заместить местными родственными тканями. Для этого на разных участках раневого дефекта применены различные методы пластической хирургии: пластика местными тканями, замещение дефекта ротированным кожно-фасциальным лоскутом и пластика местными тканями методом дозированного растяжения. Комбинированное применение этих методов позволило полностью восстановить полноценные мягкие ткани и волосяной покров травмированной теменно-затылочной области

Magnetic properties of colloidal suspensions of interacting magnetic particles

We review equilibrium thermodynamic properties of systems of magnetic particles like ferrofluids in which dipolar interactions play an important role. The review is focussed on two subjects: ({\em i}) the magnetization with the initial magnetic susceptibility as a special case and ({\em ii}) the phase transition behavior. Here the condensation ("gas/liquid") transition in the subsystem of the suspended particles is treated as well as the isotropic/ferromagnetic transition to a state with spontaneously generated long--range magnetic order.Comment: Review. 62 pages, 4 figure

CALCULATION OF THE INDICATORS OF THE RELIABILITY OF THE ELECTRIC POWER SYSTEM ELEMENTS OF A 110 KV

The paper discusses the main indicators of the structural reliability of the electrical network. The relative failure rate and recovery time of each air line for the entire period of operation is calculated.В работе рассматриваются основные показатели структурной надежности электрической сети. Рассчитана относительная частота отказов и время восстановления каждой воздушной линии за весь период эксплуатации

Spectroscopic and photoluminescence characterization of Eu 3+-doped monoclinic KY(WO4)2 crystal

Monoclinic 2 at% Eu-doped KY(WO4)2 is grown by top-seeded solution growth method. Polarizationresolved absorption and stimulated-emission cross-section spectra are determined for this crystal. Spectroscopic properties of Eu:KY(WO4)2 are modeled within conventional Judd–Ofelt theory, as well as theory of f–f transition intensities for systems with anomalously strong configuration interaction, yielding absorption oscillator strengths, luminescence branching ratios and radiative lifetime of 5D0 state. The impact of excited-state absorption from this state on possibility of laser operation is discussed. Photoluminescent properties of Eu:KY(WO4)2 are determined. This crystal provides intense red emission with CIE coordinates x¼0.670, y¼0.329