Beyond Moore's technologies: operation principles of a superconductor alternative

The predictions of Moore's law are considered by experts to be valid until 2020 giving rise to "post-Moore's" technologies afterwards. Energy efficiency is one of the major challenges in high-performance computing that should be answered. Superconductor digital technology is a promising post-Moore's alternative for the development of supercomputers. In this paper, we consider operation principles of an energy-efficient superconductor logic and memory circuits with a short retrospective review of their evolution. We analyze their shortcomings in respect to computer circuits design. Possible ways of further research are outlined.Comment: OPEN ACCES

STRUCTURE FORMATION PROCESS OF HYDRATED PORTLAND CEMENT COMPOSITIONS: NANOSCALE LEVEL CONTROL

Durability of cement-like construction materials, as well as durability of cement stone, depends on their humidity resistance, frost resistance, corrosion resistance. All of these properties depend not only on the composition of the original clinker, but also on structural organization at micro-and nanoscale level of hydrated portland cement compositions. In this research the authors used the method of small-angle neutron scattering to define structural parameters of hydrated portland cement compositions on nanoscale level, distribution of calcium hydrate silicate nanoparticles in size, medium nanoparticles radius, fractal dimension. It is shown, that introduction of modifying nanoadditives into portland cement compositions affects structural parameters of a cement stone. The following nanoadditives were used: of artificial (alpha aluminium oxide, gamma aluminum oxide) and of anthropogenic (carbonate and alumo-alkaline sludges) origin, as well as integrated nanoadditives containing surfactants. The change in structural parameters of portland cement compositions with nanoadditives in the process of hydration is investigated. It is shown that use of nanoadditives allows to control the process of forming the structure of hydrated portland cement composition on the nanoscale level, directly affect the values of structural parameters and, as a result, modify properties of cement stone

Proximity effect in [Nb(1.5nm)/Fe(x)]10_{10}/Nb(50nm) superconducting/ferromagnet heterostructures

We have investigated the structural, magnetic and superconducting properties of [Nb(1.5nm)/Fe(x)]$_{10}$ superlattices deposited on a thick Nb(50nm) layer. Our investigation showed that the Nb(50nm) layer grows epitaxially at 800$^\circ$C on Al$_2$O$_3$(1$\bar{1}$02) substrate. Samples grown at this condition posses a high residual resistivity ratio of 15-20. By using neutron reflectometry we show that Fe/Nb superlattices with $x<$ 4 nm form a depth-modulated FeNb alloy with concentration of iron varying between 60% and 90%. This alloy has properties of a weak ferromagnet. Proximity of this weak ferromagnetic layer to a thick superconductor leads to an intermediate phase that is characterized by co-existing superconducting and normal-state domains. By increasing the thickness of the Fe layer to $x$ = 4 nm the intermediate phase disappears. We attribute the intermediate state to proximity induced non-homogeneous superconductivity in the periodic Fe/Nb structure

Influence of the spin-dependent quasiparticle distribution on the Josephson current through a ferromagnetic weak link

The Josephson current flowing through weak links containing ferromagnetic elements is studied theoretically under the condition that the quasiparticle distribution over energy states in the interlayer is spin-dependent. It is shown that the interplay between the spin-dependent quasiparticle distribution and the triplet superconducting correlations induced by the proximity effect between the superconducting leads and ferromagnetic elements of the interlayer, leads to the appearence of an additional contribution to the Josephson current. This additional contribution $j_t$ can be extracted from the full Josephson current in experiment. The features of the additional supercurrent $j_t$, which are of main physical interest are the following: (i) We propose the experimental setup, where the contributions given by the short-range (SRTC) and long-range (LRTC) components of triplet superconducting correlations in the interlayer can be measured separately. It can be realized on the basis of S/N/F/N/S junction, where the interlayer is composed of two normal metal regions with a spiral ferromagnet layer sandwiched between them. For the case of tunnel junctions the measurement of $j_t$ in such a system can provide direct information about the energy-resolved anomalous Green's function components describing SRTC and LRTC. (ii) In some cases the exchange field-suppressed supercurrent can be not only recovered but also enhanced with respect to its value for non-magnetic junction with the same interface resistances by the presence of spin-dependent quasiparticle distribution. This effect is demonstrated for S/N/S junction with magnetic S/N interfaces. In addition, it is also found that under the considered conditions the dependence of the Josephson current on temperature can be nontrivial: at first the current rises upon temperature increasing and only after that starts to decline.Comment: 19 pages, 9 figures, published version, presentation improve

РАННИЙ РЕЦИДИВ МИНИМАЛЬНОГО РАКА ЭНДОМЕТРИЯ (КЛИНИЧЕСКИЙ СЛУЧАЙ)

Endometrial cancer is the 6-th most common malignancy in women worldwide, accounting for about 4.8 % of all female cancers. The treatment of recurrent endometrial cancer remains a major challenge. Some endometrial cancer recurrences, for example vaginal stump recurrence, are reported to be effectively treated with surgical resection and radiation therapy. Early recurrence of early-stage well-differentiated endometrial cancer is uncommon. Case report. Herein we report a rare case of recurrent well-differentiated endometrial cancer in a 65-year-old woman. The patient had recurrence 10 months after laparoscopic hysterectomy with bilateral salpingo-oophorectomy. Recurrent endometrial tumor with extension into the rectosigmoid colon, urinary bladder and the right ureter manifested itself clinically with severe pain requiring the use of opioids. The recurrent tumor was removed. Resection of the bladder, left ureter and upper ampular rectum was followed by anastomosis. The patient received multiple cycles of chemotherapy. Conclusion. Compliance with the principles of ablastics during the laparoscopic or laparotomic surgery helps to avoid recurrence in patients with prognostically favorable cancer. In case of recurrence, combined operations are the only possible chance of improving survival of patients with locally advanced or recurrent tumors, which are insensitive to chemoradiotherapy.Актуальность. Рак эндометрия занимает шестое ранговое место среди злокачественных новообразований у женского населения в мире, и его доля составляет 4,8 %. Одним из нерешенных вопросов при лечении данной патологии является лечение рецидивов рака эндометрия. Некоторые рецидивы, например в культе влагалища, в ведущих онкологических клиниках успешно лечат с помощью хирургического вмешательства, лучевой терапии или комбинированным методом. К редким случаям можно отнести ранние рецидивы при высокодифференцированном минимальном раке эндометрия, особенно требующие симультанных операций. Описание клинического случая. Представлен редкий случай рецидива минимального рака эндометрия у пациентки 65 лет, возникшего через 10 мес после экстирпации матки с придатками, выполненный лапароскопическим доступом. Рецидивная опухоль эндометрия с прорастанием в ректосигмоидный отдел толстой кишки, стенку мочевого пузыря и правого мочеточника клинически проявляла себя сильными болями, требовавшими назначения наркотических анальгетиков. Больной была выполнена комбинированная операция в объеме удаления рецидивной опухоли, резекции мочевого пузыря и левого мочеточника, верхнеампулярного отдела прямой кишки с формированием анастомозов и проведена последующая многокурсовая химиотерапия. Заключение. Соблюдение принципов абластики во время хирургического вмешательства лапароскопическим либо лапаротомным доступом помогает избежать рецидивов при прогностически благоприятных формах рака. При рецидиве опухолей, мало чувствительных к химиолучевому лечению, комбинированные операции являются единственным возможным шансом на улучшение состояния, а иногда и полное выздоровление

Observation of the Triplet Spin-Valve Effect in a Superconductor-Ferromagnet Heterostructure

The theory of superconductor-ferromagnet (S-F) heterostructures with two ferromagnetic layers predicts the generation of a long-range, odd-in-frequency triplet pairing at non-collinear alignment (NCA) of the magnetizations of the F-layers. This triplet pairing has been detected in a Nb/Cu41Ni59/nc-Nb/Co/CoOx spin-valve type proximity effect heterostructure, in which a very thin Nb film between the F-layers serves as a normal conducting (nc) spacer. The resistance of the sample as a function of an external magnetic field shows that for not too high fields the system is superconducting at a collinear alignment of the Cu41Ni59 and Co layer magnetic moments, but switches to the normal conducting state at a NCA configuration. This indicates that the superconducting transition temperature Tc for NCA is lower than the fixed measuring temperature. The existence of a minimum Tc, at the NCA regime below that one for parallel or antiparallel alignments of the F-layer magnetic moments, is consistent with the theoretical prediction of a singlet superconductivity suppression by the long-range triplet pairing generation.Comment: 7 pages, 4 fgures, Submitted to Physical Review Letter

Multi-channel phase-equivalent transformation and supersymmetry

Phase-equivalent transformation of local interaction is generalized to the multi-channel case. Generally, the transformation does not change the number of the bound states in the system and their energies. However, with a special choice of the parameters, the transformation removes one of the bound states and is equivalent to the multi-channel supersymmetry transformation recently suggested by Sparenberg and Baye. Using the transformation, it is also possible to add a bound state to the discrete spectrum of the system at a given energy $E<0$ if the angular momentum at least in one of the coupled channels $l\ge 2$.Comment: 9 pages, revtex; to be published in Phys. At. Nucl. (Oct. 2000

Polytene chromosomes reflect functional organization of the Drosophila genome

Polytene chromosomes of Drosophila melanogaster are a convenient model for studying interphase chromosomes of eukaryotes. They are giant in size in comparison with diploid cell chromosomes and have a pattern of cross stripes resulting from the ordered chromatid arrangement. Each region of polytene chromosomes has a unique banding pattern. Using the model of four chromatin types that reveals domains of varying compaction degrees, we were able to correlate the physical and cytological maps of some polytene chromosome regions and to show the main properties of genetic and molecular organization of bands and interbands, that we describe in this review. On the molecular map of the genome, the interbands correspond to decompacted aquamarine chromatin and 5’ ends of ubiquitously active genes. Gray bands contain lazurite and malachite chromatin, intermediate in the level of compaction, and, mainly, coding parts of genes. Dense black transcriptionally inactive bands are enriched in ruby chromatin. Localization of several dozens of interbands on the genome molecular map allowed us to study in detail their architecture according to the data of whole genome projects. The distribution of proteins and regulatory elements of the genome in the promoter regions of genes localized in the interbands shows that these parts of interbands are probably responsible for the formation of open chromatin that is visualized in polytene chromosomes as interbands. Thus, the permanent genetic activity of interbands and gray bands and the inactivity of genes in black bands are the basis of the universal banding pattern in the chromosomes of all Drosophila tissues. The smallest fourth chromosome of Drosophila with an atypical protein composition of chromatin is a special case.  Using the model of four chromatin states and fluorescent in situ hybridization, its cytological map was refined and the genomic coordinates of all bands and interbands were determined. It was shown that, in spite of the peculiarities of this chromosome, its band organization in general corresponds to the rest of the genome. Extremely long genes of different Drosophila chromosomes do not fit the common scheme, since they can occupy a series of alternating bands and interbands (up to nine chromosomal structures) formed by parts of these genes