Electron transport and optical properties of shallow GaAs/InGaAs/GaAs quantum wells with a thin central AlAs barrier

Shallow GaAs/InGaAs/GaAs quantum well structures with and without a three monolayer thick AlAs central barrier have been investigated for different well widths and Si doping levels. The transport parameters are determined by resistivity measurements in the temperature range 4-300 K and magnetotransport in magnetic fields up to 12 T. The (subband) carrier concentrations and mobilities are extracted from the Hall data and Shubnikov-de Haas oscillations. We find that the transport parameters are strongly affected by the insertion of the AlAs central barrier. Photoluminescence spectra, measured at 77 K, show an increase of the transition energies upon insertion of the barrier. The transport and optical data are analyzed with help of self-consistent calculations of the subband structure and envelope wave functions. Insertion of the AlAs central barrier changes the spatial distribution of the electron wave functions and leads to the formation of hybrid states, i.e. states which extend over the InGaAs and the delta-doped layer quantum wells.Comment: 14 pages, pdf fil

Kronecker's Double Series and Exact Asymptotic Expansion for Free Models of Statistical Mechanics on Torus

For the free models of statistical mechanics on torus, exact asymptotic expansions of the free energy, the internal energy and the specific heat in the vicinity of the critical point are found. It is shown that there is direct relation between the terms of the expansion and the Kronecker's double series. The latter can be expressed in terms of the elliptic theta-functions in all orders of the asymptotic expansion.Comment: REVTeX, 22 pages, this is expanded version which includes exact asymptotic expansions of the free energy, the internal energy and the specific hea

Decoherence produces coherent states: an explicit proof for harmonic chains

We study the behavior of infinite systems of coupled harmonic oscillators as t->infinity, and generalize the Central Limit Theorem (CLT) to show that their reduced Wigner distributions become Gaussian under quite general conditions. This shows that generalized coherent states tend to be produced naturally. A sufficient condition for this to happen is shown to be that the spectral function is analytic and nonlinear. For a rectangular lattice of coupled oscillators, the nonlinearity requirement means that waves must be dispersive, so that localized wave-packets become suppressed. Virtually all harmonic heat-bath models in the literature satisfy this constraint, and we have good reason to believe that coherent states and their generalizations are not merely a useful analytical tool, but that nature is indeed full of them. Standard proofs of the CLT rely heavily on the fact that probability densities are non-negative. Although the CLT generally fails if the probability densities are allowed to take negative values, we show that a CLT does indeed hold for a special class of such functions. We find that, intriguingly, nature has arranged things so that all Wigner functions belong to this class.Comment: Final published version. 17 pages, Plain TeX, no figures. Online at http://astro.berkeley.edu/~max/gaussians.html (faster from the US), from http://www.mpa-garching.mpg.de/~max/gaussians.html (faster from Europe) or from [email protected]

Multifractality in Time Series

We apply the concepts of multifractal physics to financial time series in order to characterize the onset of crash for the Standard & Poor's 500 stock index x(t). It is found that within the framework of multifractality, the "analogous" specific heat of the S&P500 discrete price index displays a shoulder to the right of the main peak for low values of time lags. On decreasing T, the presence of the shoulder is a consequence of the peaked, temporal x(t+T)-x(t) fluctuations in this regime. For large time lags (T>80), we have found that C_{q} displays typical features of a classical phase transition at a critical point. An example of such dynamic phase transition in a simple economic model system, based on a mapping with multifractality phenomena in random multiplicative processes, is also presented by applying former results obtained with a continuous probability theory for describing scaling measures.Comment: 22 pages, Revtex, 4 ps figures - To appear J. Phys. A (2000

Местный рецидив рака предстательной железы после радикальной простатэктомии. Трансректальная ультразвуковая диагностика

Research purpose. Investigate possibilities of the transrectal ultrasonography (TRUS) in early diagnostics of the local recurrence of the prostate cancer (PC) following radical prostatectomy (RPE). Materials and methods. 50 PC patients at the age of 52–73 years (mean age – 62,5 years) that have undergone RPE in different clinics were under our observation. Preoperational prostate-specific antigen (PSA) value mounted 1,7–30 ng/ml. The following stages were determined clinically: Т1N0M0 – 8 patients, Т2N0M0 – 42 patients (Т2а – 38, Т2b – 2, T2c – 2). Following RPE, a positive surgical edge was revealed in 7 patients, tumor invasion to the seminal vesicles – in 3. After performed RPE, PSA level was determined 1 time per 3 months and TRUS in B-mode using energetic mapping (EM) was performed in all the patients. For this, MEDISON company SonoAce 8800 device with convex intracavitary sensor with a frequency 7,5 MHz was used. Results. In 1,5 years after RPE, PSA level increase more then 0,2 ng/ml (0,58–28 ng/ml) was observed. Patients have been examined, including: digital rectal investigation (DRI), TRUS of the prostate bed, helical computed tomography (HCT) of the minor pelvis organs, skeleton scintigraphy. DRI revealed a hardening part in 1 patient, bone metastatic lesion in 2 patients. Via HCT of the minor pelvis organs, a pathologic structure in the prostate bed region with invasion of the posterior bladder wall was revealed. By B-mode TRUS using EM, the areas of solid structure in the region of vesico-urethral anastomosis or behind the posterior bladder wall were revealed in 9 patients, including hypoechogenic with deformed coiled vessels – in 6, isoechogenic with solitary signals by EM – in 2, mixed echogenicity with the posterior bladder wall invasion – in 1 patients. By histological examination of the biopsy materials from the doubtful regions, the PC recurrence is diagnosed in 8 patients, in 1 – histologically local PC recurrence has not been confirmed. Conclusions. TRUS with using EM – is a higly informative, economically and clinically significant method of early diagnostics of the local PC recurrence following RPE.

Psychosomatic aspects of managing patientsafter operative treatment in occasion of gynecological pathology

The analysis of the psychological sphere of the women who underwent surgical treatment for gynecological pathology in the amount of 70 people. For the assessment of psychological status of patients was used a number of standard techniques. The data obtained indicate the need psychological help to women with gynecological pathology after surgical treatment.Проведен анализ психологической сферы женщин, перенесших хирургическое лечение по поводу гинекологической патологии в количестве 70 человек. Для оценки психологического статуса пациенток использовались ряд стандартных методик. Полученные данные свидетельствуют о необходимости психологической помощи женщинам с гинекологической патологией после оперативного лечения

Результаты комбинированного и химиолучевого лечения больных раком грудного отдела пищевода по данным регионального онкологического центра

Background. esophageal cancer (ec) is one of the most aggressive malignancies of the gastrointestinal tract. chemoradiation therapy is the standard of care for locally advanced ec.The purpose of the study was to evaluate the efficacy of chemoradiation therapy given alone and in combination with surgery in patients with thoracic esophageal cancer.Material and Methods. From January 1, 2012 to december 31, 2021, a total of 940 patients with thoracic esophageal cancer were registered in the regional cancer registry, of which 178 patients were selected for concurrent chemoradiotherapy (CRT) at clinical stages I–III. thirty seven thoracic esophageal cancer patients who received CRT and required treatment interruption due to complications were not included in our analysis. The final analysis included 141 patients.Results. 37 (20.7 %) patients were unable to complete treatment due to intolerance and the development of severe complications of CRT. Hematological toxicity of grade 3-4 was noted in 21 patients (14.8 %). Non-hematological complications of grade 2-4 were noted in 109 patients (77.3 %). The 5-year relapse-free survival rates in patients undergoing and non-undergoing to surgery were 23.0 and 25.0 %, respectively (p=0.018). Overall 5-year survival rates were 24 and 27 %, respectively (p=0.020). The rate of pathological complete response (pcR) was 43.5 % (in 20 of 46 patients who underwent surgery after CRT). The median survival time in patients with clinical complete response (ccR) was 24.0 months and the median survival time in patients with pcR was 29.0 months. The 3-year survival rates were 21 and 45 %, respectively (p=0.050).Conclusion. The combination of chemoradiotherapy and surgery in patients with thoracic esophageal cancer demonstrated an increase in overall survival in our study. if there is a complete clinical response to CRT and contraindications for surgery or the patient’s refusal to undergo surgery, it is advisable to use the “wait & watch” tactic.Актуальность. Рак пищевода (РП) – одно из самых агрессивных онкологических заболеваний желудочнокишечного тракта. Химиолучевая терапия является стандартом лечения местнораспространенного РП.Цель исследования – изучить эффективность химиолучевой терапии как в самостоятельном варианте, так и в качестве предоперационного воздействия в лечении больных раком грудного отдела пищевода.Материал и методы. В период с 01.01.12 по 31.12.21 в регионарном канцер-регистре взято на учет 940 больных раком грудного отдела пищевода, из них отобрано 178 пациентов, которым проведена одновременная ХЛТ по поводу РП I–III клинической стадии. Данные пациентов (n=37), у которых на фоне ХЛТ возникли осложнения, требующие прерывания лечения, не учитывались при оценке непосредственных и отдаленных результатов. В окончательный анализ включены данные о 141 больном.Результаты. Не смогли завершить лечение по причине непереносимости и тяжелых осложнений химиолучевого лечения 37 (20,7 %) пациентов. Гематологическая токсичность III–iV степени отмечена у 21 (14,8 %), негематологические осложнения II–iV степени – у 109 (77,3 %) пациентов. Общая 5-летняя выживаемость в группе неоперированных и оперированных больных составила 24 и 27 % (p=0,020), 5-летняя безрецидивная выживаемость – 23,0 и 25,0 % соответственно (p=0,018). Частота полного патоморфологического ответа составила 43,5 % (у 20 из 46 оперированных пациентов после ХЛТ). Медиана срока дожития в группе с CCR составила 24,0 мес от начала наблюдения, медиана срока дожития в группе с pcR – 29,0 мес от начала наблюдения. Трехлетняя выживаемость составила 21 и 45 % соответственно (p=0,050).Заключение. Сочетание химиолучевой терапии и хирургического вмешательства у больных раком грудного отдела пищевода продемонстрировало в нашем исследовании увеличение общей выживаемости. При наличии полного клинического ответа на химиолучевое лечение и наличии противопоказаний или отказа от операции целесообразно использование тактики «wait&watch»

МЕХАНИЗМ СТАБИЛЬНОСТИ ТОРФЯНЫХ БИТУМОВ

It has been established that the reason for stability of peat bitumes during metamorphism process is the presence of “quasipolyconjugation” systems caused by synergistic effect of the interaction of individual aromatic rings and hydrogen bondings functional groups.Установлено, что стабильность торфяных битумов в процессе метаморфизма обязана наличию систем «квазипо­ лисопряжения», обусловленных синергическим эффектом взаимодействия одиночных ароматических колец и водо­ родных связей функциональных групп