Temperature evolution of magnetic structure of HoFeO3_3 by single crystal neutron diffraction

We have investigated the temperature evolution of the magnetic structures of HoFeO$_3$ by single crystal neutron diffraction. The three different magnetic structures found as a function of temperature for \hfo\ are described by the magnetic groups Pb$'$n$'2_1$, Pbn$2_1$ and Pbn$'2_1'$ and are stable in the temperature ranges $\approx$ 600-55~K, 55-37~K and 35$>T>2$~K respectively. In all three the fundamental coupling between the Fe sub-lattices remains the same and only their orientation and the degree of canting away from the ideal axial direction varies. The magnetic polarisation of the Ho sub-lattices in these two higher temperature regions, in which the major components of the Fe moment lie along $x$ and $y$, is very small. The canting of the moments from the axial directions is attributed to the antisymmetric interactions allowed by the crystal symmetry. They include contributions from single ion anisotropy as well as the Dzyaloshinski antisymmetric exchange. In the low temperature phase two further structural transitions are apparent in which the spontaneous magnetisation changes sign with respect to the underlying antiferromagnetic configuration. In this temperature range the antisymmetric exchange energy varies rapidly as the the Ho sub-lattices begin to order. So long as the ordered Ho moments are small the antisymmetric exchange is due only to Fe-Fe interactions, but as the degree of Ho order increases the Fe-Ho interactions take over whilst at the lowest temperatures, when the Ho moments approach saturation the Ho-Ho interactions dominate. The reversals of the spontaneous magnetisation found in this study suggest that in \hfo\ the sums of the Fe-Fe and Ho-Ho antisymmetric interactions have the same sign as one another, but that of the Ho-Fe terms is opposite

Threshold Implementations of all 3x3 and 4x4 S-boxes

Side-channel attacks have proven many hardware implementations of cryptographic algorithms to be vulnerable. A recently proposed masking method, based on secret sharing and multi-party computation methods, introduces a set of sufficient requirements for implementations to be provably resistant against first-order DPA with minimal assumptions on the hardware. The original paper doesn\u27t describe how to construct the Boolean functions that are to be used in the implementation. In this paper, we derive the functions for all invertible $3 \times 3$, $4 \times 4$ S-boxes and the $6 \times 4$ DES S-boxes. Our methods and observations can also be used to accelerate the search for sharings of larger (e.g. $8 \times 8$) S-boxes. Finally, we investigate the cost of such protection

A saddle in a corner - a model of collinear triatomic chemical reactions

A geometrical model which captures the main ingredients governing atom-diatom collinear chemical reactions is proposed. This model is neither near-integrable nor hyperbolic, yet it is amenable to analysis using a combination of the recently developed tools for studying systems with steep potentials and the study of the phase space structure near a center-saddle equilibrium. The nontrivial dependence of the reaction rates on parameters, initial conditions and energy is thus qualitatively explained. Conditions under which the phase space transition state theory assumptions are satisfied and conditions under which these fail are derived

Applying General Access Structure to Proactive Secret Sharing Schemes

Verifiable secret sharing schemes (VSS) are secret sharing schemes (SSS) dealing with possible cheating by participants. In this paper we use the VSS proposed by Cramer, Damgard and Maurer \cite{CDM99,CDM00,Cra00}. They introduced a purely linear algebraic method to transform monotone span program (MSP) based secret sharing schemes into VSS. In fact, the monotone span program model of Karchmer and Wigderson \cite{KW93} deals with arbitrary monotone access structures and not just threshold ones. Stinson and Wei \cite{SW99} proposed a proactive SSS based on threshold (polynomial) VSS. The purpose of this paper is to build unconditionally secure proactive SSS over any access structure, as long as it admits a linear secret sharing scheme (LSSS)

Some remarks on the geometry of the Standard Map

We define and compute hyperbolic coordinates and associated foliations which provide a new way to describe the geometry of the standard map. We also identify a uniformly hyperbolic region and a complementary 'critical' region containing a smooth curve of tangencies between certain canonical 'stable' foliations.Comment: 25 pages, 11 figure

Эффективное управление развитием науки как единым целым: подходы к теме

The paper examines the issues of managing the science development as a whole. The purpose of the study is to increase the efficiency of management of the development of science by identifying factors that contribute to or hinder the development of science as a whole and to consider approaches to assessing the level of development of science. The article suggests approaches to this topic, which are expressed in the consideration of science as a whole, as well as in an attempt to approach the construction of a model that allows taking into account the intensity of the influence of the whole set of factors on the development or inhibition of science as a whole. For this purpose, the following factors were identified and systematized, those that: always contribute to the development of science as a whole; always inhibit the development (hinder the development) of science as a whole; as well as those that both slow down and accelerate the development of science.For this reason, some of the factors have been identified that: always contributing to the development of science as a whole; always hindering the development of science as a whole; both hindering and accelerating the development of science. The systematization of these factors has been carried out. A statement of the research goal is proposed and, based on its decomposition, five tasks are set. Some shortcomings of modern methods and techniques of monitoring, evaluating the progress of scientific research and determining the level of development of science, based on scientometric indicators, are indicated. An approach is proposed to assess the level of science development depending on the time period under consideration, external conditions and the intensity of the factors influence on the development or inhibition of science as a wholeВ работе исследуются вопросы управления развитием науки. Целью исследования является повышение эффективности управления развитием науки путем выявления факторов, которые комплексно меняют динамику развития науки, и рассмотреть подходы к оценке уровня развития науки. В статье предложены подходы к этой теме, которые выражаются в рассмотрении науки как единого целого, а также в попытке подойти к построению модели, которая позволяет учесть интенсивность влияния всей совокупности факторов на развитие или торможение науки. Для этого были выявлены и систематизированы три группы факторов: всегда способствующих развитию науки; всегда тормозящих развитию (препятствующих развитию) науки; как замедляющих, так и ускоряющих развитие науки. Указаны некоторые недостатки современных методик и техник мониторинга, оценки прогресса научных исследований и определения уровня развития науки, базирующиеся на наукометрических показателях. Предложен подход к оценке уровня развития науки в зависимости от рассматриваемого периода времени, внешних условий и интенсивностей влияния факторов на развитие или сдерживание наук

Little-Parks effect and multiquanta vortices in a hybrid superconductor--ferromagnet system

Within the phenomenological Ginzburg-Landau theory we investigate the phase diagram of a thin superconducting film with ferromagnetic nanoparticles. We study the oscillatory dependence of the critical temperature on an external magnetic field similar to the Little-Parks effect and formation of multiquantum vortex structures. The structure of a superconducting state is studied both analytically and numerically.Comment: 7 pages, 1 figure. Submitted to J. Phys.: Condens. Mat

Genotyping of tick-borne encephalitis and Kemerovo viruses in taiga ticks collected in the Komi Republic

Over the last years, an increasing rate of ixodes tick bites has been registered in the northern regions of the European Russia. In addition, the number of subjects request medical assistance due to tick bites has been dramatically increased in the Komi Republic. In addition, incidence of tick-borne encephalitis was also increased particularly starting since 2009. However, highly limited data on pathogen genetic diversity related to viral tick-borne infections in this region are currently available. Taiga ticks (Ixodespersulcatus) collected from the Komi Republic southern and central part vegetation were examined to identify and genotype tick-borne viruses. Individual ticks were used to identify by RT-PCR viral RNA coupled to tick-borne encephalitis and Kemerovo viruses. Viral genome fragment sequencing allowed to unambiguously identify these viruses. It was found that viral RNA tick-borne encephalitis was detected in 6.8±1.2% individual ticks. Moreover, tick-linked isolate genotyping based on analyzing E protein gene fragment nucleotide sequence derived from tick-borne encephalitis discovered that 35% and 65% isolates belonged to the Far Eastern and Siberian subtype, respectively. In addition, subsequent phylogenetic analysis demonstrated that at least four variants of the Siberian and Far Eastern subtypes of tick-borne encephalitis virus were detected, which were close to the viruses circulating in the Urals and Siberia. In contrast, prevalence of Kemerovo virus in taiga ticks was 0.8±0.2%. Sequencing of Kemerovo virus RNA-dependent RNA polymerase gene fragment showed around 94% homology with the remainder of the Kemerovo virus strains. Phylogenetic analysis of the Kemerovo virus genome fragments demonstrated at least two subtypes circulating in the Komi Republic. Thus, it was suggested that tick-borne encephalitis virus was introduced relatively recently from the Urals and Siberian region into the natural foci of the Komi Republic. Moreover, genetic differences found in Kemerovo virus strains presume for them a longer lasting evolution throughout the natural foci of this region. In addition, a potential role for birds and their ticks in rapid spreading of viral tick-borne infections in the Komi Republic is also discussed. Thus, the data on genetic diversity of the viral agents related to tick-born encephalitis and Kemerovo fever may be useful for improving their diagnostics, prevention and treatment in the Komi Republic

ЭКЗОСОМЫ И ПЕРЕДАЧА (ЭПИ)ГЕНЕТИЧЕСКОЙ ИНФОРМАЦИИ ОПУХОЛЕВЫМИ КЛЕТКАМИ

In this review, we will introduce the current knowledge about exosomes – vesicles that are generated in the cells and released into the extracellular space. Exosomes are forming in the cell plasma membrane and represent the spherical shapes restricted by their membrane and contained the various biomolecules including nucleic acids, proteins, lipids etc. The intent interest to exosomes is based on their ability to horizontal transfer between the cells, to permeate into vascular system reaching the different tissues and to incorporate into the recipient cells. It was shown that exosome incorporation into the cells lead to remarkable changes in the recipient cells both in genomic level (via the integration of exosomal DNA into the host DNA) and in epigenomic level (via the modulation of the content and/or activity of the signaling proteins, microRNA etc.). Undoubtedly, one of the most interesting and perspective achievements in the exosome study is the demonstration of exosome ability to provide the horizontal transfer of the genetic information from cell to cell – the fact supported in the different studies with the various cell models. Here, we will discuss the recent data regarding the main characteristics and properties of exosomes, the role of exosomes in the tumorigenesis including neoplastic transformation, metastasis, multi-drug resistance. The final part of the review involves the most growing area in the exosome study – the possible usage of exosomes in the cancer treatment, in particular – as the specific drug delivery system.В обзоре рассматриваются современные представления об экзосомах – везикулах, образующихся внутри клеток и секретируемых в окружающую среду. Они формируются на плазматической мембране клеток и представляют собой сферические структуры, ограниченные своей мембраной и содержащие различные биомолекулы, включая нуклеиновые кислоты, белки, липиды и проч. Обнаруженные в последние годы свойства экзосом перемещаться между клетками, проходить в кровяное русло, достигая самых различных тканей, и в итоге проникать внутрь клеток-реципиентов обеспечили пристальное внимание исследователей к изучению их биологических функций. Установлено, что экзосомы, проникая в клетки-реципиенты, могут вызывать в них целый каскад изменений на геномном (за счет интеграции ДНК) и эпигеномном (за счет изменения экспрессии/содержания белков, микроРНК и проч.) уровнях. Безусловно, одним из самых интересных и значимых достижений в изучении экзосом явилось установление возможности горизонтальной передачи информации от клетки к клетке с их участием – факт, неоднократно продемонстрированный исследователями на разных моделях. В обзоре приводятся современные данные об основных характеристиках и свойствах экзосом; о роли экзосом в развитии злокачественных новообразований, в частности – об их участии в опухолевой трансформации, метастазировании, формировании лекарственной устойчивости. Заключительный раздел обзора посвящен одному из наиболее стремительно развивающихся направлений в этой области – использованию экзосом в клинической практике, в том числе для избирательной доставки противоопухолевых препаратов в опухоль

Metabolites of Purine Nucleoside Phosphorylase (NP) in Serum Have the Potential to Delineate Pancreatic Adenocarcinoma

Pancreatic Adenocarcinoma (PDAC), the fourth highest cause of cancer related deaths in the United States, has the most aggressive presentation resulting in a very short median survival time for the affected patients. Early detection of PDAC is confounded by lack of specific markers that has motivated the use of high throughput molecular approaches to delineate potential biomarkers. To pursue identification of a distinct marker, this study profiled the secretory proteome in 16 PDAC, 2 carcinoma in situ (CIS) and 7 benign patients using label-free mass spectrometry coupled to 1D-SDS-PAGE and Strong Cation-Exchange Chromatography (SCX). A total of 431 proteins were detected of which 56 were found to be significantly elevated in PDAC. Included in this differential set were Parkinson disease autosomal recessive, early onset 7 (PARK 7) and Alpha Synuclein (aSyn), both of which are known to be pathognomonic to Parkinson's disease as well as metabolic enzymes like Purine Nucleoside Phosphorylase (NP) which has been exploited as therapeutic target in cancers. Tissue Microarray analysis confirmed higher expression of aSyn and NP in ductal epithelia of pancreatic tumors compared to benign ducts. Furthermore, extent of both aSyn and NP staining positively correlated with tumor stage and perineural invasion while their intensity of staining correlated with the existence of metastatic lesions in the PDAC tissues. From the biomarker perspective, NP protein levels were higher in PDAC sera and furthermore serum levels of its downstream metabolites guanosine and adenosine were able to distinguish PDAC from benign in an unsupervised hierarchical classification model. Overall, this study for the first time describes elevated levels of aSyn in PDAC as well as highlights the potential of evaluating NP protein expression and levels of its downstream metabolites to develop a multiplex panel for non-invasive detection of PDAC