Dissipative phase transition in systems with two-photon drive and nonlinear dissipation near the critical point

We study dissipative phase transition near the critical point for a system with two-photon driving and nonlinear dissipation. The proposed mean-field theory, which explicitly takes into account quantum fluctuations, allowed us to describe properly the evolution dynamics of the system and to demonstrate the new effects in the steady-state. We show that the presence of quantum fluctuations leads to a power-law dependence of the anomalous average at the phase transition point, with which the critical exponent is associated. Also, we investigate the effect of the quantum fluctuations on the critical point renormalization and demonstrate the existence of a two-photon pump threshold. It is noteworthy that the obtained results are in a good agreement with the numerical simulations.Comment: 7 pages, 4 figure

Dynamics of spatial coherence and momentum distribution of polaritons in a semiconductor microcavity under conditions of Bose-Einstein condensation

The study was supported by the Russian Foundation for Basic Research (project nos. 12-02-33091, 13-02-12197, and 14-02-01073) and the Presidium of the Russian Academy of Sciences. The work of V.V.B. was supported in part by a scholarship of the President of the Russian Federation.The dynamics of spatial coherence and momentum distribution of polaritons in the regime of Bose-Einstein condensation in a GaAs microcavity with embedded quantum wells under nonresonant excitation with picosecond laser pulses are investigated. It is shown that the establishment of the condensate coherence is accompanied by narrowing of the polariton momentum distribution. At the same time, at sufficiently high excitation densities, there is significant qualitative discrepancy between the dynamic behavior of the width of the polariton momentum distribution determined from direct measurements and that calculated from the spatial distribution of coherence. This discrepancy is observed at the fast initial stage of the polariton system kinetics and, apparently, results from the strong spatial nonuniformity of the phase of the condensate wavefunction, which equilibrates on a much longer time scale.Publisher PDFPeer reviewe

Partially coherent conical refraction promises new counter-intuitive phenomena

In this paper, we extend the paraxial conical refraction model to the case of the partially coherent light using the unified optical coherence theory. We demonstrate the decomposition of conical refraction correlation functions into well-known conical refraction coherent modes for a Gaussian Schell-model source. Assuming randomness of the electrical field phase of the input beam, we reformulated and significantly simplified the rigorous conical refraction theory. This approach allows us to consider the propagation of light through a conical refraction crystal in exactly the same way as in the classical case of coherent radiation. Having this in hand, we derive analytically the conical refraction intensity both in the focal plane and in the far field, which allows us to explain and rigorously justify earlier experimental findings and predict new phenomena. The last include the counterintuitive effect of narrowing of the conical refraction ring width, disappearance of the dark Poggendorff’s ring in the Lloyd’s plane, and shift of Raman spots for the low-coherent conical refraction light. We also demonstrate a universal power-law dependence of conical refraction cones coherence degree on the input correlation length and diffraction-free propagation of the low-coherent conical refraction light in the far field

Zero-bias photodetection in 2d materials via geometric design of contacts

Structural or crystal asymmetry are necessary conditions for emergence of zero-bias photocurrent in light detectors. Structural asymmetry has been typically achieved via $p-n$ doping being a technologically complex process. Here, we propose an alternative approach to achieve zero-bias photocurrent in 2d material flakes exploiting the geometrical non-equivalence of source and drain contacts. As a prototypical example, we equip a square-shaped flake of PdSe$_2$ with mutually orthogonal metal leads. Upon uniform illumination with linearly-polarized light, the device demonstrates non-zero photocurrent which flips its sign upon 90$^\circ$ polarization rotation. The origin of zero-bias photocurrent lies in polarization-dependent lightning-rod effect. It enhances the electromagnetic field at one contact from the orthogonal pair, and selectively activates the internal photoeffect at the respective metal-PdSe$_2$ Schottky junction. The proposed technology of contact engineering can be extended to arbitrary 2d materials and detection of both polarized and natural light

Mitoxantrone Quantification by HPLC-MS/MS in Caco-2 Culture Media

Mitoxantrone is a marker substrate of breast cancer resistance protein (BCRP). BCRP is involved in a number of pharmacokinetic drug-drug interactions. The transporter’s possible saturability makes it advisable to use low concentrations of mitoxantrone for in vitro studies. Consequently, mitoxantrone quantification requires   a method with high sensitivity.The aim of the study was to develop and validate a procedure for mitoxantrone quantification in Caco-2 culture media by HPLC-MS/MS.Materials and methods.  The  authors  used  an  Ultimate  3000  HPLC  system  and a TSQ Fortis triple quadrupole mass spectrometer by Thermo Fisher Scientific and a Selectra C18 column (4.6×100 mm, 5 μm, 100 Å) by United Chemical Technologies. The elution ran in a gradient mode with a mobile phase of 1% formic acid solution and methanol. Experimental parameters were as follows: eluent flow rate, 0.3 mL/min; separation column temperature, 35 °C; injection volume, 5  μL; ana lysis time, 10 min; approximate mitoxantrone retention time, 5.51 min. The sample preparation involved protein precipitation from the culture medium with methanol, followed by centrifugation at 13,000 g for 10 min. The detection was performed using electrospray ionisation in the positive ion mode. Detection parameters were   as follows: electrospray voltage, 3700 V; sheath gas flow rate, 50 L/min; auxiliary    gas flow rate, 10 L/min; sweep gas flow rate, 1 L/min; ion-transfer tube temperature, 300 °C; and evaporator temperature, 350 °C. The detection was set at mass transitions of m/z 455 to 88.2 and m/z 455 to 358.1, with the collision energy for these transitions amounting to 25 V and 18 V, respectively. The source fragmentation was at 0, and the CID gas pressure was at 2 mTorr.Results. The analytical procedure showed selectivity, high sensitivity (limit of detection, 10 nmol/L; lower limit of quantification, 50 nmol/L), accuracy, precision, and linearity in the concentration range of 50–1000 nmol/L. The authors observed no carryover or matrix effects. A simulation of real-life storage conditions demonstrated high stability of mitoxantrone samples. Thus, the analytical procedure enables preclinical evaluation of medicinal product effects on the functional activity of BCRP, based on assessing the transcellular mitoxantrone transport in the presence of a test product.Conclusion. The authors developed and validated the analytical procedure for mitoxantrone quantification in Caco-2 culture media by HPLC-MS/MS

INTERSTICIAL PNEUMONITIS, CAUSED BY PEGYLATED INTERFERON ALFA-2A IN A 4 MONTHS CHILD WITH GIGANTIC KAPOSI'S HAEMANGIOEPITHELIOM AND KASABACH – MERRIT PHENOMENON: A CASE REPORT

The article presents the description of a case of drug-induced lung impairment in a child

Conical refraction with low-coherence light sources

We report on conical refraction (CR) with low-coherence light sources, such as light-emitting diodes and decoherentized HeNe laser radiation, and demonstrate different CR patterns. In our experiments, a variation of the pinhole sizes from 25 to 100 µm and the distances to pinhole from 50 to 5 cm reduced spatial coherence of radiation that resulted in the disappearance of the dark Poggendorff’s ring in the Lloyd’s plane. This is attributed to the interference nature of the Lloyd’s distribution and found to be in excellent agreement with the paraxial dual-cone model of conical refraction

Методика количественного анализа маркерного субстрата ABCB1-белка фексофенадина в лизате клеток Caco-2

One way to analyze the activity of the ABCB1 protein is to assess the accumulation of its substrate fexofenadine (F.) inside the test cells. The goal is to develop and validate a method for the quantitative analysis of F. in Caco-2 cell lysate using HPLC-MS/MS. Materials and methods. Caco-2 cell lysate was used as a matrix. The analysis was performed on an "Ultimate 3000" chromatograph with a TSQ Fortis triple quadrupole mass detector, a UCT Selectra C18 4.6 mm*100 mm 5 µm column in a gradient elution mode. The mobile phase rate was 0.3 ml/min, the sample volume was 20 µl, the ionization mode was positive, and the internal standard was amantadine (ng/ml). Sample preparation — precipitation of cell lysate protein with acetonitrile. The method was validated for the following parameters: selectivity, linearity, lower limit of quantitation (LLOQ), correctness, precision, sample transfer and sample stability. Results. Chromatograms of the blank lysate of Caco-2 cells showed no peaks with retention times characteristic of F. (5.70 min) and amantadine (3.58 min). NPKO F. was 0.5 ng/ml. F.'s transfer did not exceed 20% of NPKO, and amantadine — 5%. Based on the results of the analysis of three series of calibration standards (0.5; 1; 1.5; 5; 10; 25; 40; 50 ng/ml), linear regression equations were obtained, the correlation coefficients exceeded 0.99. Accuracy and precision were assessed within and between cycles by analyzing F. solutions in the matrix (0.5; 1.5; 25 and 40 ng/ml) within three cycles. The parameters did not exceed 20% for LLPO and 15% for other points. The stability of F. solutions (1.5 and 40 ng/ml) in the lysate was analyzed during storage at room temperature, after 3-fold freezing-thawing, storage at -80 °C for 60 days, after sample preparation and being in the autosampler for 24 hours. The accuracy was within 15% of the nominal values. Conclusions. A method for the quantitative determination of F. in Caco-2 cell lysate using HPLC-MS/MS has been developed and validated.Один из способов анализа активности ABCB1-белка — это оценка накопления его субстрата фексофенадина (Ф.) внутри тест-клеток. Цель — разработка и валидация методики количественного анализа Ф. в лизате клеток Caco-2 с помощью ВЭЖХ-МС/МС. Материалы и методы. В качестве матрицы использовался лизат клеток Caco-2. Анализ выполняли на хроматографе «Ultimate 3000» с тройным квадрупольным масс-детектором TSQ Fortis, колонкой UCT Selectra C18 4,6 мм×100 мм 5 мкм в градиентном режиме элюирования. Скорость подвижной фазы — 0,3 мл/мин, объём пробы — 20 мкл, режим ионизации — положительный, внутренний стандарт — амантадин (нг/мл). Пробоподготовка — осаждение белка лизата клеток ацетонитрилом. Методику валидировали по параметрам: селективность, линейность, нижний предел количественного определения (НПКО), правильность, прецизионность, перенос пробы и стабильность образцов. Результаты. На хроматограммах холостого лизата клеток Caco-2 не было пиков со временем удерживания, характерным для Ф. (5,70 мин) и амантадина (3,58 мин). НПКО Ф. составил 0,5 нг/мл. Перенос Ф. не превышал 20 % НПКО, а амантадина — 5 %. По результатам анализа трёх серий градуировочных стандартов (0,5; 1; 1,5; 5; 10; 25; 40; 50 нг/мл) получены уравнения линейной регрессии, коэффициенты корреляции превышали 0,99. Правильность и прецизионность оценивали внутри и между циклами, выполняя анализ растворов Ф. в матрице (0,5; 1,5; 25 и 40 нг/мл) в рамках трёх циклов. Параметры не превышали 20 % для НПКО и 15 % — для остальных точек. Стабильность растворов Ф. (1,5 и 40 нг/мл) в лизате анализировали при хранении при комнатной температуре, после 3-кратной заморозки–разморозки, хранении при -80 °С 60 сут., после пробоподготовки и нахождения в автосемплере 24 ч. Правильность находилась в пределах 15 % от номинальных значений. Выводы. Разработана и валидирована методика количественного определения Ф. в лизате клеток Caco-2 с помощью ВЭЖХ-МС/МС

ПРОБЛЕМЫ ОРГАНИЗАЦИИ МЕДИЦИНСКОЙ ПОМОЩИ ПАЦИЕНТАМ С ДЫХАТЕЛЬНОЙ НЕДОСТАТОЧНОСТЬЮ ПРИ ВОСПАЛИТЕЛЬНОЙ ДЕМИЕЛИНИЗИРУЮЩЕЙ ПОЛИРАДИКУЛОНЕЙРОПАТИИ

The number of patients with severe forms of demyelinating polyradiculoneuropathy and respiratory failure is constantly increasing. The current state of health care system and funding of medical services do not allow full compensation of the costs for provision of care for those with this disorder. Goal of the article: the specific clinical case is used to raise the awareness of the need for taking system decisions to provide treatment for the patients requiring continuous respiratory support. Legal regulations and approaches to payment for medical services are to be changed, special centers able to accumulate such patients are to be organized, care at home is to be provided. Число пациентов с тяжелыми формами демиелинизирующей полирадикулонейропатии и дыхательной недостаточностью неуклонно возрастает. Текущее состояние системы здравоохранения и финансирования медицинских услуг не позволяет в полной мере компенсировать затраты на оказание помощи больным с данной патологией. Цель работы: на примере конкретного случая привлечь внимание к необходимости принятия системных решений для организации лечения пациентов, нуждающихся в длительной респираторной поддержке. Требуются изменение законодательной базы, подходов к оплате медицинских услуг, создание специальных центров, способных аккумулировать таких пациентов, организация медицинской помощи в домашних условиях.

МИНИ-ИНВАЗИВНЫЙ ПОДХОД В ЛЕЧЕНИИ РАКА ПРАВОЙ ПОЛОВИНЫ ТОЛСТОЙ КИШКИ, ОСЛОЖНЕННОГО ТОЛСТОКИШЕЧНОЙ НЕПРОХОДИМОСТЬЮ

The case demonstrates an opportunity of safe and successful colonic stenting to treat bowel obstruction with following laparoscopic radical intervention for right-sided colon cancer localization. The colonic stent as a “bridge to the surgery” improves immediate results and surviving rate in elderly patients with complicated right-sided colon cancer and severe concomitant disease.Клинический случай демонстрирует возможность успешного и безопасного применения стентирования толстой кишки для лечения кишечной непроходимости и последующей лапароскопической радикальной операции при правосторонней локализации опухоли толстой кишки. Использование стентирования толстой кишки в качестве «моста к хирургии» позволяет улучшить непосредственные результаты и выживаемость среди пожилых больных с осложненным раком правой половины толстой кишки и тяжелой сопутствующей патологией