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

Пути создания инвертированного микроскопа на базе микроскопа биологического

В роботі описано засіб виготовлення інвертованого мікроскопу шляхом доробки мікроскопу біологічного. Описано інвертований мікроскоп, створений на базі мікроскопу МБР-3. Наведено методику розрахунку основних оптичних характеристик інвертованого мікроскопу, виконано розрахунки для широко розповсюджених об’єктивів і окулярів.In this work the manufacturing of the inverted microscope by the way of revision of biological microscope is described. There is described the inverted microscope manufactured on the basis of MBR-3 microscope. It contains calculations methods of the main optical specifications of the inverted microscope and the results of calculations for the most spread objectives lenses and eyepieces.В работе описан способ изготовления инвертированного микроскопа путем доработки микроскопа биологического. Описан инвертированный микроскоп, созданный на базе микроскопа МБР-3. Приведена методика расчета основных оптических характеристик инвертированного микроскопа, выполнены расчеты для наиболее широко распространенных объективов и окуляров

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

Coloured nanocapsules formation process by ink-jet printing

Разработан и исследован процесс формирования окрашенных капсул в пленках анодного оксида алюминия методом струйной печати. Получены окрашенные слои толщиной до 150 мкм с разрешением порядка 50 мкм, как на типографском алюминиевом листе, так и на фольге, приваренной анодной сваркой к стеклянной подложке, при частичном либо сквозном анодировании алюминия с последующим заполнением нанопор анодного оксида. Полученные таким образом окрашенные слои обладают исключительной термической и химической стойкостью. Описанный в настоящей статье низкотемпературный и достаточно дешевый процесс перспективен для организации массового производства дисплейных устройств и элементов электронной техники нового поколения с использованием высокопроизводительной "с рулона на рулон" (roll-to-roll) технологии.The coloured capsules formation process was developed and researched by ink-jet printing in a film of nanostructural anodic aluminum oxide. The coloured layers were obtained with thickness up to 150 m and resolution of about 50 m at partial and through aluminum anodizing with the follow- ing anodic oxide nanopores filling as on typographical aluminum as on foil welding to glass substrate. Thermal and chemical stability of the obtained coloured layers were obtained. This low-temperature inexpensive process is perspective for organization of mass display production and electronic technique elements of new generation with using of the highly productive of "roll-to-roll" technology

Tracking with capillaries and liquid scintillator

The technique of glass capillaries filled with liquid scintillator allows the reconstruction of ionizing particle tracks with high spatial resolution. Detectors based on this technique consist of coherent arrays of capillaries having diameters of the order of 20 mu m. Light signals are amplified by an optoelectronic chain composed of a series of image intensifiers: the readout is performed through a CCD. The ongoing research in the field of liquid scintillators has led to excellent results in terms of information density (greater than or equal to 5 hits/mm) and radiation resistance (order of 1 MGy). In this paper new results about the effect of ageing and purification of liquid scintillators will be presented. The RD46 collaboration has developed a completely new detector having a readout chain composed of only one image intensifier followed by a new device: a Megapixel Electron Bombarded CCD. First images of neutrino interactions will be shown, together with preliminary measurements of the resolution of the detector