Pseudogap from ARPES experiment: three gaps in cuprates and topological superconductivity

A term first coined by Mott back in 1968 a `pseudogap' is the depletion of the electronic density of states at the Fermi level, and pseudogaps have been observed in many systems. However, since the discovery of the high temperature superconductors (HTSC) in 1986, the central role attributed to the pseudogap in these systems has meant that by many researchers now associate the term pseudogap exclusively with the HTSC phenomenon. Recently, the problem has got a lot of new attention with the rediscovery of two distinct energy scales (`two-gap scenario') and charge density waves patterns in the cuprates. Despite many excellent reviews on the pseudogap phenomenon in HTSC, published from its very discovery up to now, the mechanism of the pseudogap and its relation to superconductivity are still open questions. The present review represents a contribution dealing with the pseudogap, focusing on results from angle resolved photoemission spectroscopy (ARPES) and ends up with the conclusion that the pseudogap in cuprates is a complex phenomenon which includes at least three different `intertwined' orders: spin and charge density waves and preformed pairs, which appears in different parts of the phase diagram. The density waves in cuprates are competing to superconductivity for the electronic states but, on the other hand, should drive the electronic structure to vicinity of Lifshitz transition, that could be a key similarity between the superconducting cuprates and iron based superconductors. One may also note that since the pseudogap in cuprates has multiple origins there is no need to recoin the term suggested by Mott.Comment: invited review, more info at http://www.imp.kiev.ua/~kor

Paraconductivity of K-doped SrFe2As2 superconductor

Paraconductivity of the optimally K-doped SrFe2As2 superconductor is investigated within existing fluctuation mechanisms. The in-plane excess conductivity has been measured in high quality single crystals, with a sharp superconducting transition at Tc=35.5K and a transition width less than 0.3K. The data have been also acquired in external magnetic field up to 14T. We show that the fluctuation conductivity data in zero field and for temperatures close to Tc, can be explained within a three-dimensional Lawrence-Doniach theory, with a negligible Maki-Thompson contribution. In the presence of the magnetic field, it is shown that paraconductivity obeys the three-dimensional Ullah-Dorsey scaling law, above 2T and for H||c. The estimated upper critical field and the coherence length nicely agree with the available experimental data.Comment: 12 pages, 5 figure

Normal-superconducting transition induced by high current densities in YBa2Cu3O7-d melt-textured samples and thin films: Similarities and differences

Current-voltage characteristics of top seeded melt-textured YBa2Cu3O7-d are presented. The samples were cut out of centimetric monoliths. Films characteristics were also measured on microbridges patterned on thin films grown by dc sputtering. For both types of samples, a quasi-discontinuity or quenching was observed for a current density J* several times the critical current density Jc. Though films and bulks much differ in their magnitude of both Jc and J*, a proposal is made as to a common intrinsic origin of the quenching phenomenon. The unique temperature dependence observed for the ratio J*/Jc, as well as the explanation of the pre-quenching regime in terms of a single dissipation model lend support to our proposal.Comment: 10 pages, 10 figures, submitted to Physical Review

Effects of Ferumoxides – Protamine Sulfate Labeling on Immunomodulatory Characteristics of Macrophage-like THP-1 Cells

Superparamagnetic Iron Oxide (SPIO) complexed with cationic transfection agent is used to label various mammalian cells. Labeled cells can then be utilized as an in vivo magnetic resonance imaging (MRI) probes. However, certain number of in vivo administered labeled cells may be cleared from tissues by the host's macrophages. For successful translation to routine clinical application of SPIO labeling method it is important that this mode of in vivo clearance of iron does not elicit any diverse immunological effects. The purpose of this study was to demonstrate that SPIO agent ferumoxides-protamine sulfate (FePro) incorporation into macrophages does not alter immunological properties of these cells with regard to differentiation, chemotaxis, and ability to respond to the activation stimuli and to modulate T cell response. We used THP-1 cell line as a model for studying macrophage cell type. THP-1 cells were magnetically labeled with FePro, differentiated with 100 nM of phorbol ester, 12-Myristate-13-acetate (TPA) and stimulated with 100 ng/ml of LPS. The results showed 1) FePro labeling had no effect on the changes in morphology and expression of cell surface proteins associated with TPA induced differentiation; 2) FePro labeled cells responded to LPS with slightly higher levels of NFκB pathway activation, as shown by immunobloting; TNF-α secretion and cell surface expression levels of CD54 and CD83 activation markers, under these conditions, were still comparable to the levels observed in non-labeled cells; 3) FePro labeling exhibited differential, chemokine dependent, effect on THP-1 chemotaxis with a decrease in cell directional migration to MCP-1; 4) FePro labeling did not affect the ability of THP-1 cells to down-regulate T cell expression of CD4 and CD8 and to induce T cell proliferation. Our study demonstrated that intracellular incorporation of FePro complexes does not alter overall immunological properties of THP-1 cells. The described experiments provide the model for studying the effects of in vivo clearance of iron particles via incorporation into the host's macrophages that may follow after in vivo application of any type of magnetically labeled mammalian cells. To better mimic the complex in vivo scenario, this model may be further exploited by introducing additional cellular and biological, immunologically relevant, components

Оптические, механические и электрические характеристики теплового неохлаждаемого детектора болометрического типа на основе оксида ванадия

Determination of optical, mechanical and electrical characteristics is one of the decisive factors in the design of instrumentation structures of thermal uncooled bolometer-type detectors (microbolometers). The paper presents the results of optimization calculations by means of computer simulation of absorption, transmittance and reflection spectra of device structures of microbolometers based on thermosensitive vanadium oxide film by finite-difference time-domain method (FDTD). The characteristics of the investigated microbolometer structure were checked for compliance with mechanical and electrical requirements for this class of devices.Определение оптических, механических и электрических характеристик является одним из решающих факторов при проектировании приборных структур тепловых неохлаждаемых детекторов болометрического типа (микроболометров). В статье представлены результаты оптимизационных расчетов посредством компьютерного моделирования спектров поглощения, пропускания и отражения приборных структур микроболометров на основе термочувствительной пленки оксида ванадия методом конечных разностей во временной области (англ. finite-difference time-domain, FDTD). Выполнена проверка на соответствие характеристик исследуемой структуры микроболометра механическим и электрическим требованиям, предъявляемым к данному классу приборов

Расчет оптических параметров тонких пленок конструкционных материалов теплового неохлаждаемого детектора болометрического типа

The increased interest in utilizing uncooled thermal bolometer-type detectors (microbolometers) within the infrared or terahertz detection field is justified by their operational and technological characteristics, in particular: relatively low manufacturing cost, high detection efficiency, compatibility with silicon CMOS technology, and operation at room temperature. The performance of such detectors depends on optimizing critical parameters, which are dictated by both the geometrical design and the electrical, optical, and thermal properties of the materials used. The determination of optical parameters stands as a decisive factor in the design of microbolometer structures. This article delves into the examination of optical parameters of thin films of structural materials of microbolometer based on thermosensitive vanadium oxide film manufactured at JSC “INTEGRAL”. The investigation showcases the results of determining optical constants (refractive indexes n and absorption coefficients k) of thin films from the transmission curve by applying the reflection-transmission method. Furthermore, a comparison is carried out between the results of computer modeling of the transmission, reflection and absorption spectra – taking into account the obtained values of the coefficients n and k – and the empirical data from the in-situ experiment.Повышенный интерес к применению неохлаждаемых тепловых детекторов болометрического типа (микроболометров) в инфракрасном или терагерцовом поле обнаружения обоснован их эксплуатационными и технологическими характеристиками, в частности: относительно низкой стоимостью изготовления, высокой эффективностью обнаружения, совместимостью с кремниевой КМОП-технологией, работоспособностью при комнатной температуре. Характеристики таких детекторов зависят от оптимизации критических параметров, которые определяются геометрией конструкции, а также электрическими, оптическими и тепловыми свойствами применяемых материалов. Определение оптических параметров является одним из решающих факторов при проектировании приборных структур микроболометров. В статье исследованы оптические параметры тонких пленок конструкционных материалов микроболометра на основе термочувствительной пленки оксида ванадия, изготовленных в ОАО «ИНТЕГРАЛ». Приведены результаты определения посредством применения метода отражения-передачи оптических констант (коэффициентов преломления n и поглощения k) тонких пленок по кривой пропускания. Выполнено сравнение результатов компьютерного моделирования спектров пропускания, отражения и поглощения с учетом полученных значений коэффициентов n и k с данными натурного эксперимента

Clinical significance of antinucleosome antibodies in patients with “early” systemic lupus erythematosus

Objective. To assess clinical and diagnostic value of antibodies to nucleosom e in «early» systemic lupus erythematosus (SLE).Material and methods. 37 pts with «early « SLE were included. The control groups consisted of 36 pts with rheumatoid arthritis (RA), 31 pts with primary Sjogren›s syndrom e (SS) and 45 healthy subjects. Concentration of antibodies to nucleosom e and to double stranded deoxyribonucleic acid (dsDNA) was measured with enzyme immunoassay (EIA).Results. The level of antinucleosom e antibodies in SLE pts (64,5 ± 53,7 U/ml) was significantly higher than in RA and SS pts (JO, 9 ±23,7 U/ml; p<0,05 и 15,7 ±11,5 U/ml respectively; p<0,05) or in donors (8,3 ± 5,2 U/ml; p<0,05). Correlation was found between level of antibodies to nucleosom e and antibodies to dsDNA (χ2 = 14,4; p<0,05). Sensitivity (87,5%) and specificity (95%) of antinucleosom e antibodies were similar to anti-dsDNA antibodies (85,2% и 93% respectively). Simultaneous evaluation of antibodies to nucleosom e and dsDNA provided 97 % specificity. There was a correlation between the level of antibodies to nucleosom e and disease activity in SLE (p<0,0001).Conclusion. Evaluation of antinucleosom e antibodies with EIA is a sensitive and specific serological test for early SLE diagnosis. The antibodies to nucleosom e reflect activity of SL

Development of comorbid infection in patients with polymyositis/dermatomyositis

Полимиозит (ПМ) и дерматомиозит (ДМ) – аутоиммунные заболевания скелетной мускулатуры неизвестной этиологии, которые относятся к системным заболеваниям соединительной ткани и объединяются общим термином – идиопатические воспалительные миопатии (ИВМ) [1-3].Ведущим клиническим признаком ПМ/ДМ является поражение скелетной мускулатуры, проявляющееся слабостью мышц плечевого и тазового пояса, проксимальных отделов верхних и нижних конечностей, мышц шеи и спины и др. Может развиваться отек мышц. Мышечная слабость нарастает от минимальных проявлений (утомляемость) до выраженного двигательного дефицита в течение нескольких недель или месяцев. Пациенты с трудом встают (или не могут встать) с низкого стула, не могут подняться в транспорт, поднять руки для умывания или причесывания. Наблюдаются также неуклюжая походка и эпизоды неожиданных падений, связанных со слабостью мышц тазового пояса и бедер. Пациенты не могут самостоятельно встать с кровати и оторвать голову от подушки. Мышечные атрофии развиваются у больных, длительно страдающих ПМ/ДМ и не получающих адекватную терапию глюкокортикоидами (ГК). Характерно поражение мышц глотки, гортани и верхней трети пищевода, ведущее к дисфонии, дисфагии. Основными признаками поражения кожи при ДМ являются: эритематозная сыпь на лице, на волосистой части головы, на груди («декольте») и на плечах («шаль»), параорбитальный гелиотропный отек, шелушащаяся эритема на коже тыльной поверхности пястнофаланговых, проксимальных межфаланговых, локтевых и коленных суставов (эритема Готтрона), фотосенсибилизация. Наряду с этим у многих больных наблюдаются такие системные проявления, как феномен Рейно, ревматоидноподобный полиартрит, плотный отек кистей, склеродактилия, рука«механика» и гипотония пищевода, что сближают ПМ/ДМ с другими системными заболеваниями соединительной ткани. У значительного числа больных ИВМ (от 20 до 55%) появляются симтомы дыхательной недостаточности, которая способствует ограничению двигательной активности пациента и обусловлена как сопутствующим интерстициальным поражением легких, так и слабостью дыхательной мускулатуры [1-4]