Aharanov-Bohm excitons at elevated temperatures in type-II ZnTe/ZnSe quantum dots

Optical emission from type-II ZnTe/ZnSe quantum dots demonstrates large and persistent oscillations in both the peak energy and intensity indicating the formation of coherently rotating states. Furthermore, the Aharanov-Bohm (AB) effect is shown to be remarkably robust and persists until 180K. This is at least one order of magnitude greater than the typical temperatures in lithographically defined rings. To our knowledge this is the highest temperature at which the AB effect has been observed in semiconductor structures

Microwave-induced magnetotransport phenomena in two-dimensional electron systems: Importance of electrodynamic effects

We discuss possible origins of recently discovered microwave induced photoresistance oscillations in very-high-electron-mobility two-dimensional electron systems. We show that electrodynamic effects -- the radiative decay, plasma oscillations, and retardation effects, -- are important under the experimental conditions, and that their inclusion in the theory is essential for understanding the discussed and related microwave induced magnetotransport phenomena.Comment: 5 pages, including 2 figures and 1 tabl

Wave Functions and Energies of Magnetopolarons in Semiconductor Quantum Wells

The classification of magnetopolarons in semiconductor quantum wells (QW) is represented. Magnetopolarons appear due to the Johnson - Larsen effect. The wave functions of usual and combined magnetopolarons are obtained by the diodanalization of the Schrodinger equation.Comment: 7 pages, 2 figure

Nonlinear acousto-electric transport in a two-dimensional electron system

We study both theoretically and experimentally the nonlinear interaction between an intense surface acoustic wave and a two-dimensional electron plasma in semiconductor-piezocrystal hybrid structures. The experiments on hybrid systems exhibit strongly nonlinear acousto-electric effects. The plasma turns into moving electron stripes, the acousto-electric current reaches its maximum, and the sound absorption strongly decreases. To describe the nonlinear phenomena, we develop a coupled-amplitude method for a two-dimensional system in the strongly nonlinear regime of interaction. At low electron densities the absorption coefficient decreases with increasing sound intensity, whereas at high electron density the absorption coefficient is not a monotonous function of the sound intensity. High-harmonic generation coefficients as a function of the sound intensity have a nontrivial behavior. Theory and experiment are found to be in a good agreement.Comment: 27 pages, 6 figure

Kinetics of exciton photoluminescence in type-II semiconductor superlattices

The exciton decay rate at a rough interface in type-II semiconductor superlattices is investigated. It is shown that the possibility of recombination of indirect excitons at a plane interface essentially affects kinetics of the exciton photoluminescence at a rough interface. This happens because of strong correlation between the exciton recombination at the plane interface and at the roughness. Expressions that relate the parameters of the luminescence kinetics with statistical characteristics of the rough interface are obtained. The mean height and length of roughnesses in GaAs/AlAs superlattices are estimated from the experimental data.Comment: 3 PostScript figure

Robot-assisted technologies for targeted prostate biopsy: a literature review

One key aspect in treating any cancer is timely diagnosis and treatment. Obtaining the right diagnosis depends mainly on running the biopsy algorithm. Most studies show a significant increase in sensitivity and specificity in the targeted tissue sampling method compared to standard biopsy. The human factor can result in more medical errors. This can be solved by replacing the standard biopsy method with a more advanced one. The human factor is excluded from the biopsy sampling process using the semi-automatic robotic biopsy needle guidance. This paper presents a literature review development in robot assisted prostate biopsy. A literature review was performed using PubMed and Scopus databases. Papers reporting on experiments using semi-automatic robotic systems were included. Using the literature, we described the prerequisites for the development the software for semi-automatic targeted biopsy to increase the sensitivity and specificity of prostate cancer diagnosis

First trimester prenatal screening in multiple pregnancies. Part II: serum proteins PAPP-A and β-hCG as markers of adverse pregnancy outcomes

Aim: to evaluate the ability of serum biochemical markers in pregnant woman - PAPP-A (pregnancy-associated plasma protein-A) and β-hCG (the в-subunit of human chorionic gonadotropin) studied in the first trimester (11+0-13+6) during combined prenatal screening to predict adverse perinatal outcomes of multiple pregnancy that occurred spontaneously and as a result of in vitro fertilization (IVF).Materials and methods. The main group consisted from 65 women with pregnancy occurred as a result of IVF; comparison group included 56 women with spontaneous pregnancy. All pregnancies were multiple and their outcomes were known. Serum PAPP-A and β-hCG levels were measured in the first trimester. The results were expressed in absolute values and in MoM (multiples of median). Subgroups were compared with mono- and dichorionic pregnancies, complicated and uncomplicated pregnancies, distributed according to MoM index: within the reference values (0.5-2.0), below or above the reference values.Results. PAPP-A MoM values in the spontaneous pregnancy group were 1.12 [0.8; 1.57], in the IVF group - 1.35 [1.11; 1.72] (p = 0.01). In subgroup of low PAPP-A MoM antenatal fetal death occurred in 50 %, in subgroup of normal PAPP-A MoM - in 14.58 %, in subgroup of high PAPP-A MoM - in 5.88 % (p = 0.011). In addition, a positive correlation was found between serum PAPP-A level and time of fetal death (rs = 0.564; p = 0.036). Low PAPP-A MoM values were associated with 50 % fetal mortality, 75 % of them were attributable to pregnancy as a result of IVF.Conclusion. Identification of adverse outcomes in multiple pregnancies is still a difficult task, but evaluation of serum biochemical markers during the first trimester screening can help in early diagnosis of necessity and extent of timely prophylaxis

First trimester prenatal screening in multiple pregnancies. Part I: comparative analysis of serum proteins PAPP-A and p-hCG in pregnancies conceived spontaneously or by in vitro fertilization

Introduction. Serum proteins PAPP-A (pregnancy-associated plasma protein-A) and β-hCG (the в-subunit of human chorionic gonadotropin) levels are components of the 1st trimester combined screening aimed to detect fetal aneuploidies. In contrast to singleton pregnancies, where the values are well established, this is not the case in twins.Aim: a comparative analysis of serum proteins PAPP-A and β-hCG levels, as well as parameters PAPP-A MoM and β-hCG MoM in the first trimester during pregnancy with dichorionic diamniotic twins that occurred spontaneously or as a result of in vitro fertilization (IVF).Materials and methods. The study group included multiple pregnancies as a result of IVF procedure (n = 100) and spontaneous multiple pregnancies (n = 121) considered as controls. The levels of PAPP-A, β-hCG, PAPP-A MoM and β-hCG MoM were compared using nonparametric Mann-Whitney U test.Results. The PAPP-A MoM level resulted higher in the group of IVF twins (p = 0,007) compared to spontaneous twins: 1.28 [0.97; 1.89] vs. 1.12 [0.87; 1.40] (median [interquartile range]). There were no statistically significant differences in в-hCG levels between the groups of IVF twins and spontaneous twins.Conclusion. The results justify the need for further study of PAPP-A and β-hCG to establish their association with adverse outcomes in both groups of multiple pregnancies

Оценка медицинских технологий в акушерстве: преимущества индивидуального консервативного ведения монохориальной беременности, осложненной синдромом обратной артериальной перфузии, перед хирургическим вмешательством

Introduction. Twin reversed arterial perfusion (TRAP) syndrome is one of the types of complications of monochorial twins (MT) with a frequency of occurrence of 1:35000 births. It is characterized by the presence of the main vessel instead of a normal 4 chambers heart and intrauterine developmental abnormalities. This pregnancy requires monitoring using dynamic ultrasound diagnostics every 7 days, in accordance with current recommendations. The treatment is intrauterine laser coagulation of blood vessels of the “acardial fetus” (AP) in order to prevent the development of a threatening condition for the “fetal pump” (PP). Aim: to demonstrate the possibilities of comprehensive conservative management of monochorial pregnancy complicated by TRAP.Materials and methods. An ultrasound examinations were performed on a weekly basis in monochorionic pregnancy, complicated by TRAP within the period 12-38 weeks. Serum concentrations of biochemical markers PAPP-A (pregnancy-associated plasma protein-A) and β-hGC (β-subunit of human chorionic gonadotropin) were studied in the first trimester to predict adverse perinatal outcomes.Results. The possibility of prolonging a pregnancy complicated by TRAP without performing intrauterine surgical intervention, during which quite serious complications can occur in this category of pregnancies, has been demonstrated. In a patient with monochorionic twins complicated by TRAP, totally 27 ultrasound examinations were performed within the period 12-38 weeks. This approach made it possible to dynamically monitor the condition of a pregnant and healthy fetus and to prolong pregnancy without surgery until the full term.Conclusions. Following the existing guidelines, without tailoring for individual risk, may lead to an unreasonable increase in surgical interventions. In turn, surgery is not only accompanied by a high risk of complications (up to 15%), but also constitute a certain financial burden on the budget, determined by the state on the level of 208,000 rubles. Performing routine ultrasound examinations according to the examination protocol for monochorionic pregnancy will contribute to avoiding the complications associated with surgery and better selection for surgery as well as reducing the government costs. Введение. Синдром обратной артериальной перфузии (СОАП) – один из видов осложнений монохориальной двойни (МХ) с частотой встречаемости 1:35000 родов, характеризующийся наличием магистрального сосуда вместо полноценного сердца у одного близнеца (акардиальный плод) и нарушениями внутриутробного развития разной степени. Данная беременность требует наблюдения с динамикой ультразвукового исследования (УЗИ) каждые 7 дней, что определено практическими рекомендациями. Операцией выбора является внутриутробная лазерная коагуляция сосудов, питающих акардиальный плод (АП) с целью не допустить развития угрожающих состояний для плода-помпы (ПП).Цель – продемонстрировать возможности успешного консервативного ведения монохориальной беременности, осложненной СОАП.Материалы и методы. УЗИ при монохориальной беременности двойней проводилось еженедельно, в течение 12-38 недель беременности. В первом триместре выполнялось исследование сывороточных концентраций биохимических маркеров PAPP-A (англ. – pregnancy-associated plasma protein-A, ассоциированный с беременностью протеин-А плазмы) и β-ХГЧ (свободная бета-субъединица хорионического гонадотропина человека) с целью прогнозирования неблагоприятных перинатальных исходов.Результаты. Продемонстрирована возможность пролонгации беременности, осложненной СОАП, без выполнения внутриутробного хирургического вмешательства (ВХ), в ходе которого в данной категории беременностей могут иметь место достаточно серьезные осложнения. У пациентки с монохориальной двойней, осложненной развитием СОАП, было выполнено 27 УЗИ в период 12-38 недель. Такой подход позволил динамически наблюдать за состоянием беременной и здорового плода и пролонгировать беременность без проведения хирургической операции до доношенного срока.Заключение. Следование регламентированным практическим рекомендациям к проведению ВХ, без учета индивидуальных особенностей каждого отдельного случая, может потенциально приводить к необоснованному увеличению оперативных вмешательств, повышая прямые затраты. ВХ не только сопровождаются высоким риском осложнений (до 15%), но и накладывают высокую финансовую нагрузку на бюджет, определенный государством на сегодняшний день квотой 208000 рублей. Выполнение рутинного УЗИ, согласно протоколу обследования для МХ, может способствовать снижению риска осложнений, ассоциированных с ВХ, более качественному отбору потенциальных кандидатов для ВХ, а также связанному с этим снижению бюджетных затрат на оказание медицинской помощи