Investigation of the properties of quantum-dimensional semiconductor particles A3B5 by scanning probe microscopy, obtained by liquid chemical etching

The study was carried out with the financial support of the Russian Foundation for Basic Research in the framework of scientific projects 17-07-00407-а and 17-07-00139

Polaron and bipolaron transport in a charge segregated state of doped strongly correlated 2D semiconductor

The 2D lattice gas model with competing short and long range interactions is appliedused for calculation of the incoherent charge transport in the classical strongly-correlated charge segregated polaronic state. We show, by means of Monte-Carlo simulations, that at high temperature the transport is dominated by hopping of the dissociated correlated polarons, where with thetheir mobility is inversely proportional to the temperature. At the temperatures below the clustering transition temperature the bipolaron transport becomes dominant. The energy barrier for the bipolaron hopping is determined by the Coulomb effects and is found to be lower than the barrier for the single-polaron hopping. This leads to drastically different temperature dependencies of mobilities for polarons and bipolarons at low temperatures

Vortex matter in the charged Bose liquid at absolute zero

The Gross-Pitaevskii-type equation is solved for the charge Bose liquid in the external magnetic field at zero temperature. There is a vortex lattice with locally broken charge neutrality. The boson density is modulated in real space and each vortex is charged. Remarkably, there is no upper critical field at zero temperature, so the density of single flux-quantum vortices monotonously increases with the magnetic field up to B=infinity and no indication of a phase transition. The size of each vortex core decreases as about 1/sqrt(B) keeping the system globally charge neutral. If bosons are composed of two fermions, a phase transition to a spin-polarized Fermi liquid at some magnetic field larger than the pair-breaking field is predicted.Comment: 4 pages, 4 figures, references update

Comparison of perturbative expansions using different phonon bases for two-site Holstein model

The two-site single-polaron problem is studied within the perturbative expansions using different standard phonon basis obtained through the Lang Firsov (LF), modified LF (MLF) and modified LF transformation with squeezed phonon states (MLFS). The role of these convergent expansions using the above prescriptions in lowering the energy and in determining the correlation functions are compared for different values of coupling strength. The single-electron energy, oscillator wave functions and correlation functions are calculated for the same system. The applicability of different phonon basis in different regimes of the coupling strength as well as in different regimes of hopping are also discussed.Comment: 24 pages (RevTEX), 12 postscript figures, final version accepted in PRB(2000) Jornal Ref: Phys. Rev. B, 61, 4592-4602 (2000

Quasiparticle dynamics and gap structure in Hg1223 investigated with femtosecond spectroscopy

Measurements of the temperature dependence of the quasiparticle (QP) dynamics in Hg1223 with femtosecond time-resolved optical spectroscopy are reported. From the temperature dependence of the amplitude of the photoinduced reflection, the existence of two gaps is deduced, one temperature dependent Dc that closes at Tc, and another temperature independent ''pseudogap'' Dp. The zero-temperature magnitudes of the two gaps are Dc/kTc = 6 +/- 0.5 and Dp/kTc = 6.4 +/- 0.5 respectively. The quasiparticle lifetime is found to exhibit a divergence as T -> Tc from below, which is attributed to the existence of a superconducting gap which closes at Tc. Above Tc the relaxation time is longer than expected for metallic relaxation, which is attributed to the presence of the ''pseudogap''. The QP relaxation time is found to increase significantly at low temperatures. This behavior is explained assuming that at low temperatures the relaxation of photoexcited quasiparticles is governed by a bi-particle recombination process.Comment: accepted for publication in Phys.Rev.

Current-voltage characteristic of narrow superconducting wires: bifurcation phenomena

The current-voltage characteristics of long and narrow superconducting channels are investigated using the time-dependent Ginzburg-Landau equations for complex order parameter. We found out that the steps in the current voltage characteristic can be associated with bifurcations of either steady or oscillatory solution. We revealed typical instabilities which induced the singularities in current-voltage characteristics, and analytically estimated period of oscillations and average voltage in the vicinity of the critical currents. Our results show that these bifurcations can substantially complicate dynamics of the order parameter and eventually lead to appearance of such phenomena as multistability and chaos. The discussed bifurcation phenomena sheds a light on some recent experimental findings

Checkpoint inhibitors in non-small cell lung carcinoma therapy for progression to the brain (clinical observation)

The development of a new area of antitumor drug therapy, immunotherapy using immune checkpoint inhibitors targeting PD-1/PD-L1, has significantly changed approaches to the treatment of advanced non-small cell lung cancer (NSCLC). Many clinical trials have demonstrated the clinical benefit as well as the long-term effect of these drugs. Currently, the problem of treatment of patients after disease progression against the background of the use of checkpoint inhibitors is relevant. Equally relevant is the issue of choosing the correct and most effective treatment tactics for NSCLC patients with oligoprogression, as well as with abscopal effect. This paper describes a clinical case of a patient with lung adenocarcinoma without driver mutations with PD-L1-positive status, who was treated with nivolumab after second-line chemotherapy for disease progression, and after oligoprogression of the disease into the brain was given stereotactic radiotherapy of metastatic lesion and continued therapy with nivolumab. Partial regression of metastases was achieved with a prolonged effect on the background of continued treatment with nivolumab for 24 months. Tolerability of therapy was satisfactory: no adverse events were observed. The patient retained the result for 1.5 years

РЕЗУЛЬТАТЫ ЛЕЧЕНИЯ БОЛЬНЫХ МЕСТНОРАСПРОСТРАНЕННЫМ И МЕТАСТАТИЧЕСКИМ НЕПЛОСКОКЛЕТОЧНЫМ НЕМЕЛКОКЛЕТОЧНЫМ РАКОМ ЛЕГКОГО ПРЕПАРАТОМ ПЕМЕТРЕКСЕД (СОБСТВЕННЫЙ ОПЫТ)

Lung cancer is one of the most common malignant tumors. As over 70 % of patients at diagnosis have locally advanced or generalized process, the majority of patients receive drug treatment only. We evaluated effectiveness and toxicity of pemetrexed (Alimta) in 24 patients with locally advanced and metastatic non-squamous cell non-small-cell lung carcinoma with the known EGFR mutation status. Pemetrexed 500 mg/m2 was administered as monotherapy (8 patients) or in combination with platinum-based drugs (15 patients). Three (12.5 %) patients showed complete regression, 7 (29.2 %) – partial regression, 10 (41.7 %) – stabilization, 4 (16.6 %) – progression. The median survival was 14.8 months. Non-hematological complications were registered, usually concerning the digestive system. Hematological complications included first-degree leukopenia – 27 (21.3 %), second- and third-degree thrombocytopenia – 1 case of each (0.8%). The complications did not require administration of drugs or were corrected medicamentally. We observed a high effectiveness of pemetrexed in patients with non-squamous NSCLC, as well as a low rate of complications and controlled toxicity

Условия на ложе и поверхности ледникового купола Вавилова (Северная Земля) во время его подвижки по данным аэрорадиозондирования

The glacier surge at Vavilov Ice Cap, Severnaya Zemlya, Russia (79°18′ N, 94°40′ E) began as early as the mid-1960s with a slow advance of its margin in the western part. Since 2012, the advance switched to the phase of catastrophic movement, which reached its climax in 2016, when the glacier velocity reached 9.2 km a‒1. An ice fan with an area of about 140 km2 advanced into the Kara Sea water area 11 km from the shore, and a strongly crevassed ice stream was formed in the ice cap itself, which continues to move now with speeds of about 2 km a‒1. The dynamic instability of Vavilov Ice Cap can be triggered by changes in basal conditions, which are still poorly known. In this study, we used airborne radio-echo sounding data acquired in September 2014 over the ice cap to characterize its surface and bedrock conditions. Based on the delay time and reflection amplitudes, the power reflection coefficient (PRC) from glacier surface and bedrock was estimated. For its calibration, we used the amplitude of reflections from the sea surface registered from different altitudes. The bedrock PRC values were converted to dielectric permittivity and compared with the glacier surface velocities in 2014 obtained from Landsat-7 images. We found a high positive correlation between the bedrock PRCs and velocities in the area with glacier speed higher than 1000 m a-1. In this area, the PRC is 20 dB higher than in the neighboring slower moving areas. Such a difference may be because the ice stream advanced on marine loose sediments with higher dielectric permittivity and conductivity and a higher reflection coefficient. The range of estimated bedrock PRCs corresponds to bed materials with relative dielectric permittivity from 5 to 10 and electrical conductivity from 10–5 to 10–2 Sm m‒1.По данным измерений времени запаздывания и амплитуд радиоотражений от ложа ледникового купола Вавилова, полученным в период быстрой подвижки его западной части, определены значения коэффициента отражения от ложа по мощности, которые коррелируют с высокими скоростями (более 1000 м/год) движения ледника в области, наступившей на участок мелководья