First evidence for charge ordering in NaV2_2O5_5 from Raman spectroscopy

We argue on the basis of symmetry selection rules and Raman scattering spectra that NaV$_2$O$_5$ undergoes a charge ordering phase transition at T$_c$=34 K. Such a transition is characterized by the redistribution of the charges at the phase transition and corresponds to the change of the vanadium ions, from uniform V$^{4.5+}$ to two different V$^{4+}$ and V$^{5+}$ states. In the low temperature phase the V$^{4+}$ ions are forming a "zig-zag" ladder structure along the {\bf b}-axis, consistent with the symmetry of the P2/b space group.Comment: to be published in solid state communication

Hybrid heterostructures with superconducting/antiferromagnetic interfaces

We report on structural, DC, X-ray and neutron studies of hybrid superconducting mesa-heterostructures with a cuprate antiferromagnetic interlayer Ca1-xSrxCuO2 (CSCO). The upper electrode was bilayer Nb/Au superconductor and copper oxide superconductor YBa2Cu3O7 (YBCO) was the bottom electrode. It was experimentally shown that during the epitaxial growth of the two films YBCO and CSCO a charge carrier doping takes place in the CSCO interlayer with a depth about 20 nm. The conductivity of the doped part of CSCO layer is close to the metal type, while the reference CSCO film, deposited directly on NdGaO3 substrate, behaves as Mott insulator with the hopping conductivity. The interface Au/CSCO is clearly seen on bright-field image of the cross-section of heterostructure and gives the main contribution to the total resistance of mesa-heterostructure.Comment: 16 pages, 9 figure

Anomalous thermal conductivity of NaV2O5 as compared to conventional spin-Peierls system CuGeO3

A huge increase of thermal conductivity k is observed at the phase transition in stoichiometric NaV2O5. This anomaly decreases and gradually disappears with deviation from stoichiometry in Na(1-x}V2O5 (x = 0.01, 0.02, 0.03, and 0.04). This behavior is compared with that of pure and Zn-doped CuGeO3 where only modest kinks in the k(T) curves are observed at the spin-Peierls transition. The change of k at critical temperature Tc could be partially attributed to the opening of an energy gap in the magnetic excitation spectrum excluding the scattering of thermal phonons on spin fluctuations. However, the reason for such a strong anomaly in the k(T) may lie not only in the different energy scales of CuGeO3 and NaV2O5, but also in the different character of the phase transition in NaV2O5 which can have largely a structural origin, e.g. connected with the charge ordering.Comment: PostScript 4 pages, 4 PostScript pictures. Submitted to Physical Review Letter

Relationships of nosological form of the primary and second neoplasms in oncological patients

ЗЛОКАЧЕСТВЕННЫЕ НОВООБРАЗОВАНИЯНОЗОЛОГИЧЕСКИЕ ФОРМЫ РАКАЗАБОЛЕВАЕМОСТЬ, ЧАСТОТА СЛУЧАЕВУКРАИНАЦель. Исследование зависимости между нозологическими формами первых и вторых раков у пациентов, которые проходили специальное лечение по поводу онкологического заболевания и у которых возникли вторые раки через 3 года и более после окончания лечения. Материал и методы. В исследовании проводилось сравнение между нозологической структурой вторых раков, которые возникли у 203 пациентов, проходивших лечение по поводу онкологической патологии, и официальными данными об удельном весе 10 основных нозологических форм злокачественных новообразований населения Украины. Статистическая значимость полученных результатов оценивалась с помощью доверительных интервалов, нормированных с учетом специфики контингента пациентов клиники, где проводилось исследование. Результаты. В соответствии с удельным весом нозологических форм первых раков, обусловленных, в первую очередь, специализацией клиники, обследуемые группы пациентов были разделены на 5 нозологических подгрупп: пациенты с раком молочной железы, щитовидной железы, тела матки, шейки матки, рак яичников и с иными формами рака. Для каждой из подгрупп была исследована нозологическая структура вторых раков и сопоставлена с общей структурой злокачественных новообразований по данным официальной статистики. Показано, что частота пяти выделенных нозологических форм, рассчитанных для клиники, достаточно хорошо соответствует популяционному среднему, при этом для двух наиболее представительных нозологических форм соответствие находится в пределах ожидаемой стохастической изменчивости. Таким образом, показано, что не существует статистически значимых различий между процентным составом 10 основных нозологических форм рака населения Украины и структурой нозологических форм вторых раков у исследуемой группы пациентов. Заключение. Нозологическая форма вторых раков не является следствием первого рака, а воспроизводит общую нозологическую структуру заболеваемости злокачественными новообразованиями.Objective. To investigate the relationship between nosological forms of the primary and second neoplasms in patients who have undergone special treatment for cancer, and who have developed second neoplasms three and more years after the end of treatment. Methods. The study has compared the nosological structure of second neoplasms that developed in 203 patients undergoing treatment for oncological pathology with the official data on the specific weight of 10 major nosological forms of malignant neoplasms in Ukraine. The statistical significance of the obtained results has been estimated using confidence intervals normalized taking into account the specificity of the patients of the clinic where the study was conducted. Results. In accordance with the specific weight of the nosological forms of the primary neoplasms, conditioned first by the specialization of the clinic, the study groups were divided into 5 nosological subgroups: patients with breast, thyroid, uterine, cervical, ovarian, and subgroup with other forms of cancer. For each of the subgroups, the nosological structure of the second neoplasms was investigated and compared with the overall structure of malignant neoplasms according to the official statistics. It is shown that the frequencies of five allocated nosological forms calculated for the clinic correspond fairly well to the population mean, while for two most representative nosological forms the correspondence is within the expected stochastic variability. Thus, it has been demonstrated that there are no statistically significant differences between the percentage composition of 10 major nosological forms of cancer in Ukraine and the structure of nosological forms of second neoplasms in the study group of patients. Conclusions. The nosological form of second neoplasms is not a consequence of the primary cancer, but reproduces the overall nosological structure of the incidence of malignant neoplasms

Enhancement of the Thermal Conductivity in gapped Quantum Spin Chains

We study mechanism of magnetic energy transport, motivated by recent measurements of the thermal conductivity in low dimensional quantum magnets. We point out a possible mechanism of enhancement of the thermal conductivity in gapped magnetic system, where the magnetic energy transport plays a crucial role. This mechanism gives an interpretation for the recent experiment of CuGeO_3, where the thermal conductivity depends on the crystal direction.Comment: 4 pages, 2 figure

Strong damping of phononic heat current by magnetic excitations in SrCu_2(BO_3)_2

Measurements of the thermal conductivity as a function of temperature and magnetic field in the 2D dimer spin system SrCu$_2$(BO$_3$)$_2$ are presented. In zero magnetic field the thermal conductivity along and perpendicular to the magnetic planes shows a pronounced double-peak structure as a function of temperature. The low-temperature maximum is drastically suppressed with increasing magnetic field. Our quantitative analysis reveals that the heat current is due to phonons and that the double-peak structure arises from pronounced resonant scattering of phonons by magnetic excitations.Comment: a bit more than 4 pages, 2 figures included; minor changes to improve the clarity of the presentatio

ХИМИЯ И ФУНКЦИОНАЛЬНЫЕ МАТЕРИАЛЫ. НАУЧНАЯ ШКОЛА АКАДЕМИКА Ф. А. КУЗНЕЦОВА

The paper presents a wide range of problems associated with the formation, development and practical implementation of research in materials science, carried out under direct leadership of Academician F. A. Kuznetsov by the team of researchers from the Nikolaev Institute of Inorganic Chemistry SB RAS. It shows the fruitfulness of his ideas of complex physicochemical research into each stage of the preparation of material from the precursor to the finished specific device element. Attention is drawn to his accurate prediction of the importance of selectable objects of study, his ability to correlate ongoing research with urgent global issues such as electronics, computer science, energy and photovoltaics and his skill to rally the team with a common idea and encourage active participation in the development of science both in Russia and internationally while remaining the main driving force of conducted advanced work. The paper is written in the memory of the eminent person, organizer of science, scientist and patriot whose work has always been focused on breakthrough technologies that ensure the prosperity and security of the Motherland.Рассмотрен широкий круг проблем, связанных со становлением, развитием и практической реализацией научных исследований в области материаловедения, выполненных коллективом сотрудников Института неорганической химии им. А. В. Николаева СО РАН под руководством академика Ф. А. Кузнецова. Показана плодотворность его идеи комплексного физико-химического изучения каждой стадии приготовления материала: от предшественника к готовому элементу конкретного устройства. Отмечено его безошибочное предвидение значимости выбираемых объектов исследования, его умение связывать проводимые исследования с такими насущными и глобальными проблемами, как электроника, информатика, энергетика, фотовольтаика, а также его способность сплачивать коллектив общей идеей и активное участие в развитии как российской, так и международной науки, оставаясь при этом локомотивом проводимых передовых работ. Статья написана в память о человеке, организаторе науки, ученом и патриоте, чья деятельность всегда была нацелена на прорывные технологии, обеспечивающие процветание и безопасность Родины

Theory of Two-Dimensional Quantum Heisenberg Antiferromagnets with a Nearly Critical Ground State

We present the general theory of clean, two-dimensional, quantum Heisenberg antiferromagnets which are close to the zero-temperature quantum transition between ground states with and without long-range N\'{e}el order. For N\'{e}el-ordered states, `nearly-critical' means that the ground state spin-stiffness, $\rho_s$, satisfies $\rho_s \ll J$, where $J$ is the nearest-neighbor exchange constant, while `nearly-critical' quantum-disordered ground states have a energy-gap, $\Delta$, towards excitations with spin-1, which satisfies $\Delta \ll J$. Under these circumstances, we show that the wavevector/frequency-dependent uniform and staggered spin susceptibilities, and the specific heat, are completely universal functions of just three thermodynamic parameters. Explicit results for the universal scaling functions are obtained by a $1/N$ expansion on the $O(N)$ quantum non-linear sigma model, and by Monte Carlo simulations. These calculations lead to a variety of testable predictions for neutron scattering, NMR, and magnetization measurements. Our results are in good agreement with a number of numerical simulations and experiments on undoped and lightly-doped $La_{2-\delta} Sr_{\delta}Cu O_4$.Comment: 81 pages, REVTEX 3.0, smaller updated version, YCTP-xxx