Soft elasticity in biaxial smectic and smectic-C elastomers

Ideal (monodomain) smectic-$A$ elastomers crosslinked in the smectic-$A$ phase are simply uniaxial rubbers, provided deformations are small. From these materials smectic-$C$ elastomers are produced by a cooling through the smectic-$A$ to smectic-$C$ phase transition. At least in principle, biaxial smectic elastomers could also be produced via cooling from the smectic-$A$ to a biaxial smectic phase. These phase transitions, respectively from $D_{\infty h}$ to $C_{2h}$ and from $D_{\infty h}$ to $D_{2h}$ symmetry, spontaneously break the rotational symmetry in the smectic planes. We study the above transitions and the elasticity of the smectic-$C$ and biaxial phases in three different but related models: Landau-like phenomenological models as functions of the Cauchy--Saint-Laurent strain tensor for both the biaxial and the smectic-$C$ phases and a detailed model, including contributions from the elastic network, smectic layer compression, and smectic-$C$ tilt for the smectic-$C$ phase as a function of both strain and the $c$-director. We show that the emergent phases exhibit soft elasticity characterized by the vanishing of certain elastic moduli. We analyze in some detail the role of spontaneous symmetry breaking as the origin of soft elasticity and we discuss different manifestations of softness like the absence of restoring forces under certain shears and extensional strains.Comment: 26 pages, 6 figure

ИССЛЕДОВАНИЕ ПРОБЛЕМ БЕЗОПАСНОСТИ ИСПОЛЬЗОВАНИЯ КОРОТКИХ ССЫЛОК

В работе рассмотрены сферы применения коротких ссылок, указаны их преимущества и недостатки. Описаны возможные уязвимости и атаки, а также методы защиты от них. Проанализирован общий уровень безопасности использования коротких ссылок

BUILDING A TOMOGRAPHIC VELOCITY MODEL FOR SAMOYLOV ISLAND AREA (LENA DELTA) FROM LOCAL SEISMOLOGICAL DATA FOR THE PERIOD OF 2019–2021

In our paper we present the results of seismotomographic inversion for the local seismological monitoring data obtained in the area of the Samoylov Island (Lena River delta) in 2019–2021. Tomographic velocity model was used for refining hypocenter locations of local earthquakes and for geological interpretation. The results are shown as maps of anomalies of seismic waves and Vp /Vs ratios for the 5 and 10 km depths. The velocity anomalies structure made it possible to interpret low Vp /Vs ratio as rocks related to the Siberian platform, and to compare between the boundary of the low Vp /Vs area and the trace of the known geological fault running along the Olenekskaya Channel

The Effects of Fourth Generation on the double Lepton Polarization in B \rar K \ell^+ \ell^- decay

This study investigates the influence of the fourth generation quarks on the double lepton polarizations in B \rar K \ell^+ \ell^- decay. Taking |V_{t's}V_{t'b}|\sim \{0.01-0.03\} with phase about 100^\circ, which is consistent with the b\to s\ell^+\ell^- rate and the B_s mixing parameter Delta m_{B_s}$, we obtain that the double lepton(muon and tau) polarizations are quite sensitive to the existence of fourth generation. It can serve as a good tool to search for new physics effects, precisely, to indirect search for the fourth generation quarks(t', b').Comment: 30 pages, 27 figure

Aerodynamic investigations of ventilated brake discs.

The heat dissipation and performance of a ventilated brake disc strongly depends on the aerodynamic characteristics of the flow through the rotor passages. The aim of this investigation was to provide an improved understanding of ventilated brake rotor flow phenomena, with a view to improving heat dissipation, as well as providing a measurement data set for validation of computational fluid dynamics methods. The flow fields at the exit of four different brake rotor geometries, rotated in free air, were measured using a five-hole pressure probe and a hot-wire anemometry system. The principal measurements were taken using two-component hot-wire techniques and were used to determine mean and unsteady flow characteristics at the exit of the brake rotors. Using phase-locked data processing, it was possible to reveal the spatial and temporal flow variation within individual rotor passages. The effects of disc geometry and rotational speed on the mean flow, passage turbulence intensity, and mass flow were determined. The rotor exit jet and wake flow were clearly observed as characterized by the passage geometry as well as definite regions of high and low turbulence. The aerodynamic flow characteristics were found to be reasonably independent of rotational speed but highly dependent upon rotor geometry

ВОССТАНОВЛЕНИЕ ПОКРОВНЫХ ТКАНЕЙ У ПОСТРАДАВШИХ С ТЯЖЕЛЫМИ ОТКРЫТЫМИ ПЕРЕЛОМАМИ КОСТЕЙ ГОЛЕНИ

RESUME. The aim of our study is to develop and introduce the algorithm of the early soft tissue reconstruction for the patients with severe open tibia fractures. We analyzed the treatment results retrospectively and prospectively 84 patients with severe open tibia fractures, complicated by soft tissue defects. In the comparison group (56 patients) we apply late soft tissue reconstruction. In the study group (28 patients) we applied the algorithm of early soft tissue reconstruction by plastic surgery methods. Surgery tactic depends on the patient’s condition, trauma mechanism, soft tissue defects size and localization. The algorithm of early soft tissue reconstruction was used for patients with severe open tibia fractures decreases duration of hospital treatment, rate of deep wound infection and partial necrosis of tibia bone. РЕЗЮМЕ. Целью исследования являлась разработка и применение алгоритма ранней реконструкции мягких тканей у пациентов с тяжелыми открытыми переломами костей голени. Мы ретроспективно и проспективно изучили результаты лечения 84 пострадавших с открытыми переломами костей голени, осложненными дефектами мягких тканей. В группе сравнения (56 пострадавших) применяли тактику отсроченного восстановления мягких тканей. В исследуемой группе (28 пострадавших) применили алгоритм раннего восстановления покровных тканей методами пластической хирургии. Выбор хирургической тактики проводили в зависимости от тяжести состояния пострадавшего, механизма образования, величины и локализации дефекта мягких тканей. При применении алгоритма раннего восстановления покровных тканей у пострадавших с открытыми переломами костей голени отмечено значительное сокращение сроков стационарного лечения, частоты глубокой раневой инфекции и частоты некроза участков большеберцовой кости.