Color Effects Associated with the 1999 Microlensing Brightness Peaks in Gravitationally Lensed Quasar Q2237+0305

Photometry of the Q2237+0305gravitational lens in VRI spectral bands with the 1.5-m telescope of the high-altitude Maidanak observatory in 1995-2000 is presented. Monitoring of Q2237+0305 in July-October 2000, made at nearly daily basis, did not reveal rapid (night-to-night and intranight) variations of brightness of the components during this time period. Rather slow changes of magnitudes of the components were observed, such as 0.08 mag fading of B and C components and 0.05 mag brightening of D in R band during July 23 - October 7, 2000. By good luck three nights in 1999 were almost at the time of the strong brightness peak of image C, and approximately in the middle of the ascending slope of the image A brightness peak. The C component was the most blue one in the system in 1998 and 1999, having changed its (V-I) color from 0.56 mag to 0.12 mag since August 1997, while its brightness increased almost 1.2 mag during this time period. The A component behaved similarly between August 1998 and August 2000, having become 0.47 mag brighter in R, and at the same time, 0.15 mag bluer. A correlation between the color variations and variations of magnitudes of the components is demonstrated to be significant and reaches 0.75, with a regression line slope of 0.33. A color (V-I) vrs color (V-R) plot shows the components settled in a cluster, stretched along a line with a slope of 1.31. Both slopes are noticeably smaller than those expected if a standard galactic interstellar reddening law were responsible for the differences between the colors of images and their variations over time. We attribute the brightness and color changes to microlensing of the quasar's structure, which we conclude is more compact at shorter wavelengths, as predicted by most quasar models featuring an energizing central source.Comment: 14 pages, 7 figures, LaTeX, submitted to A&

Superconductivity in the Pseudogap State due to Fluctuations of Short-Range Order

We analyze the anomalies of superconducting state (s and d-wave pairing) in a simple model of pseudogap state, induced by fluctuations of short - range order (e.g. antiferromagnetic), based on the model Fermi surface with "hot patches". We derive a system of recursion relations for Gorkov's equations which take into account all diagrams of perturbation theory for electron interaction with fluctuations of short-range order. Then we find superconducting transition temperature and gap behavior for different values of the pseudogap width and correlation lengths of short-range order fluctuations. In a similar approximation we derive the Ginzburg-Landau expansion and study the main physical characteristics of a superconductor close to the transition temperature, both as functions of the pseudogap width and correlation length of fluctuations. Results obtained are in qualitative agreement with a number of experiments on underdoped HTSC-cuprates.Comment: 18 pages, 12 figures, RevTeX 3.0, minor misprints corrected, to appear in JET

Nesting Induced Precursor Effects: a Renormalization Group Approach

We develop a controlled weak coupling renormalization group (RG) approach to itinerant electrons. Within this formalism we rederive the phase diagram for two-dimensional (2D) non-nested systems. Then we study how nesting modifies this phase diagram. We show that competition between p-p and p-h channels, leads to the manifestation of unstable precursor fixed points in the RG flow. This effect should be experimentally measurable, and may be relevant for an explanation of pseudogaps in the high temperature superconductors (HTC), as a crossover phenomenon.Comment: 4 pages, 4 figures, 1 tabl

Проблема хирургической инфекции у больных Сахарным диабетом, оперированных на аорто-подвздошном сегменте

The aim of the work: to analyze the frequency and causes of purulent-septic complications in patients who underwent endoprosthetic repair of the aorto-iliac segment. Analysis of purulent-septic complications in 54 patients who were operated for ischemic lesions of the vessels of the lower extremities in diabetes mellitus was conducted. All patients underwent interventions on the aorto-iliac segment using synthetic vascular prostheses. In accordance with the classification of purulent-septic complications of reconstructive operations 5 cases of complications available in our practice, we divided into 2 groups – prosthetic sepsis; infection of the graft without clinical and laboratory manifestations of sepsis. The frequency of purulent-septic complications 9.2 percent, almost all of these patients had grade III-IV ischemia and were operated on urgent indications. In 3 cases, infection of the graft without bacteremia patients were operated before the development of erosive bleeding, which allowed 2 patients to save limbs, and 1 patient was discharged after performing the high amputation of the limb. In two cases a partial resection of the infected portion of the bifurcation prosthesis from separate access and subsequent re-reconstruction. In one case in a patient with progressive limb ischemia removed the infected bifurcation prosthesis, and surgery was performed subclavianfemoral bypass grafting extraanatomical on the one hand, and high amputation of the contralateral limb. Prosthetic sepsis occurred in 2 patients, 1 patient died.Цель работы: проанализировать частоту и причины гнойно-септических осложнений у больных, которым выполнено эндопротезирование аорто-подвздошного сегмента. Проведен анализ гнойно-септических осложнений у 54 больных, которые были оперированы по поводу ишемических поражений сосудов нижних конечностей на фоне сахарного диабета. У всех больных были выполнены вмешательства на аорто-подвздошном сегменте с использованием синтетических сосудистых протезов. В соответствии с классификацией гнойно-септических осложнений реконструктивных операций 5 случаев осложнений, имеющихся в нашей практике, мы условно разделили на 2 группы: протезный сепсис; инфицирование трансплантата без клинических и лабораторных проявлений сепсиса. Частота гнойно-септических осложнений составила 9,2 %, почти все больные имели III–IV степень ишемии и были оперированы по неотложным показаниям. В 3 случаях инфицирования трансплантата без бактериемии пациенты оперированы до развития аррозивного кровотечения, что позволило у 2 пациентов сохранить конечности, и один пациент выписан после выполнения высокой ампутации конечности.В двух случаях выполнена частичная резекция инфицированной части бифуркационного протеза из отдельного доступа с последующей повторной реконструкцией. В одном случае у пациента с нарастающей ишемией конечности снят инфицированный бифуркационный протез и выполнена операция подключично-бедренного экстраанатомического шунтирования с одной стороны и высокая ампутация контрлатеральной конечности. Протезный сепсис имел место у 2 больных, умер один больной.Мета роботи: проаналізувати частоту і причини гнійно-септичних ускладнень у хворих, яким було виконано ендопротезування аорто-клубового сегмента. Проведено аналіз гнійно-септичних ускладнень у 54 хворих, які були оперовані з приводу ішемічних уражень судин нижніх кінцівок на тлі цукрового діабету. У всіх хворих були виконані втручання на аорто-клубовому сегменті з використанням синтетичних судинних протезів. Відповідно до класифікації гнійно-септичних ускладнень реконструктивних операцій 5 випадків ускладнень, наявних у нашій практиці, ми умовно розділили на 2 групи: протезний сепсис; інфікування трансплантата без клінічних та лабораторних проявів сепсису.Частота гнійно-септичних ускладнень становила 9,2 %, майже всі хворі мали III–IV ступінь ішемії і були оперовані за невідкладними показаннями. У 3 випадках інфікування трансплантата без бактеріємії пацієнти оперовані до розвитку арозивної кровотечі, що дозволило у 2 пацієнтів зберегти кінцівки, і одного пацієнта виписали після виконання високої ампутації кінцівки. У двох випадках виконана часткова резекція інфікованої частини біфуркаційних протеза з окремого доступу з наступною повторною реконструкцією. В одному випадку у пацієнта з наростаючою ішемією кінцівки знятий інфікований біфуркаційний протез, і виконана операція подключично-стегнового екстраанатомічного шунтування з одного боку, і висока ампутація контрлатеральної кінцівки. Протезний сепсис мав місце у 2 хворих, помер один хворий

PG 1115+080: variations of the A2/A1 flux ratio and new values of the time delays

We report the results of our multicolor observations of PG 1115+080 with the 1.5-m telescope of the Maidanak Observatory (Uzbekistan, Central Asia) in 2001-2006. Monitoring data in filter R spanning the 2004, 2005 and 2006 seasons (76 data points) demonstrate distinct brightness variations of the source quasar with the total amplitude of almost 0.4 mag. Our R light curves have shown image C leading B by 16.4d and image (A1+A2) by 12d that is inconsistent with the previous estimates obtained by Schechter et al. in 1997 - 24.7d between B and C and 9.4d between (A1+A2) and C. The new values of time delays in PG 1115+080 must result in larger values for the Hubble constant, thus reducing difference between its estimates taken from the gravitational lenses and with other methods. Also, we analyzed variability of the A2/A1 flux ratio, as well as color changes in the archetypal "fold" lens PG 1115+080. We found the A1/A2 flux ratio to grow during 2001-2006 and to be larger at longer wavelengths. In particular, the A2/A1 flux ratio reached 0.85 in filter I in 2006. We also present evidence that both the A1 and A2 images might have undergone microlensing during 2001-2006, with the descending phase for A1 and initial phase for A2. We find that the A2/A1 flux ratio anomaly in PG 1115 can be well explained both by microlensing and by finite distance of the source quasar from the caustic fold.Comment: 14 pages, 7 figures, 8 tables, Accepted for publication in MNRA

Имитационное моделирование метода оценки защищенности канала утечки информации по огибающей речевого сигнала

A method of information leakage channel security estimating based on the test speech signal envelope cross-correlation analysis is proposed and its includes: test signal generating and extracting its envelope, emitting and measuring in a leakage channel, extracting the resulting signal envelope, calculating the correlation coefficient between the original and received envelopes, and comparing with a threshold value. A metod for extracting a low-frequency signal envelope using the Hilbert transform is shown. A description of the cross-correlation analysis based on the Pearson correlation coefficient is given. The leakage channel simulation modeling, formation and measurement of the test signals was performed in the MatLab. The obtained results confirm the greater efficiency of using the envelope compared to the original signal, and demonstrate the speech signals advantage over harmonic signals as test signals for assessing the information leakage channel security.Предложен метод оценки защищенности канала утечки информации на основе взаимно- корреляционного анализа огибающей измерительного сигнала в речевом диапазоне частот. Алгоритм включает генерацию измерительного сигнала и выделение его огибающей, излучение и измерение в канале утечки, выделение огибающей результирующего сигнала, вычисление коэффициента корреляции между исходной и полученной огибающими, сравнение с пороговым значением. Описан метод выделения низкочастотной огибающей сигнала с помощью преобразования Гильберта. Приведено описание взаимно-корреляционного анализа на основе коэффициента корреляции Пирсона. Выполнено имитационное моделирование канала утечки, формирования и измерения измерительных сигналов, а также их обработка в программной среде MatLab. Полученные результаты подтверждают большую эффективность использования огибающей по сравнению с исходным сигналом, а также демонстрируют преимущество речевых сигналов перед гармоническими сигналами в качестве измерительных для оценки защищенности канала утечки информации

Correlation functions for a two-dimensional electron system with bosonic interactions and a square Fermi surface

We calculate zero-temperature correlation functions for a model of 2D interacting electrons with short-range interactions and a square Fermi surface. The model was arrived at by mapping electronic states near a square Fermi surface with Hubbard-like interactions onto one-dimensional quantum chains, retaining terms which can be written in terms of bosonic density operators. Interactions between orthogonal chains, corresponding to orthogonal faces of the square Fermi surface, are neglected. The correlation functions become sums of Luttinger-type correlation functions due to the bosonic model. However, the correlation function exponents differ in form from those of the Luttinger model. As a consequence, the simple scaling relations found to exist between the Luttinger model exponents, do not carry over to the leading exponents of our model. We find that for repulsive effective interactions, charge-density wave/spin-density wave instabilities are dominant. We do not consider d-wave instabilities here.Comment: 12 pages, no figures; to be published in Physical Review

Mid-infrared Hall effect in thin-film metals: Probing the Fermi surface anisotropy in Au and Cu

A sensitive mid-infrared (MIR, 900-1100 cm-1, 112-136 meV) photo-elastic polarization modulation technique is used to measure simultaneously Faraday rotation and circular dichroism in thin metal films. These two quantities determine the complex AC Hall conductivity. This novel technique is applied to study Au and Cu thin films at temperatures down to 20 K and magnetic fields up to 8 T. The Hall frequency is consistent with band theory predictions. We report the first measurement of the MIR Hall scattering rate, which is significantly lower than that derived from Drude analysis of zero magnetic field MIR transmission measurements. This difference is qualitatively explained in terms of the anisotropy of the Fermi surface in Au and Cu.Comment: 14 pages of text, 5 figure

Probing photo-ionization: simulations of positive streamers in varying N2:O2 mixtures

Photo-ionization is the accepted mechanism for the propagation of positive streamers in air though the parameters are not very well known; the efficiency of this mechanism largely depends on the presence of both nitrogen and oxygen. But experiments show that streamer propagation is amazingly robust against changes of the gas composition; even for pure nitrogen with impurity levels below 1 ppm streamers propagate essentially with the same velocity as in air, but their minimal diameter is smaller, and they branch more frequently. Additionally, they move more in a zigzag fashion and sometimes exhibit a feathery structure. In our simulations, we test the relative importance of photo-ionization and of the background ionization from pulsed repetitive discharges, in air as well as in nitrogen with 1 ppm O2 . We also test reasonable parameter changes of the photo-ionization model. We find that photo- ionization dominates streamer propagation in air for repetition frequencies of at least 1 kHz, while in nitrogen with 1 ppm O2 the effect of the repetition frequency has to be included above 1 Hz. Finally, we explain the feather-like structures around streamer channels that are observed in experiments in nitrogen with high purity, but not in air.Comment: 12 figure

Exact solution of a 2D interacting fermion model

We study an exactly solvable quantum field theory (QFT) model describing interacting fermions in 2+1 dimensions. This model is motivated by physical arguments suggesting that it provides an effective description of spinless fermions on a square lattice with local hopping and density-density interactions if, close to half filling, the system develops a partial energy gap. The necessary regularization of the QFT model is based on this proposed relation to lattice fermions. We use bosonization methods to diagonalize the Hamiltonian and to compute all correlation functions. We also discuss how, after appropriate multiplicative renormalizations, all short- and long distance cutoffs can be removed. In particular, we prove that the renormalized two-point functions have algebraic decay with non-trivial exponents depending on the interaction strengths, which is a hallmark of Luttinger-liquid behavior.Comment: 59 pages, 3 figures, v2: further references added; additional subsections elaborating mathematical details; additional appendix with details on the relation to lattice fermion