Геофизические особенности Верхнеюрского разреза месторождений углеводородов Томской области

Использованы петрофизические уравнения и данные геофизических исследований скважин месторождений углеводородов Томской области. Выявлены петрофизические типы коллекторов горизонта Ю1 и геофизические особенности пород баженовской свиты в разрезах с разным типом коллекторов

A combined theoretical and experimental study of the low temperature properties of BaZrO3

Low temperature properties of BaZrO3 are revealed by combining experimental techniques (X-ray diffraction, neutron scattering and dielectric measurements) with theoretical first-principles-based methods (total energy and linear response calculations within density functional theory, and effective Hamiltonian approaches incorporating/neglecting zero-point phonon vibrations). Unlike most of the perovskite systems, BaZrO3 does not undergo any (long-range-order) structural phase transition and thus remains cubic and paraelectric down to 2 K, even when neglecting zero-point phonon vibrations. On the other hand, these latter pure quantum effects lead to a negligible thermal dependency of the cubic lattice parameter below ~ 40 K. They also affect the dielectricity of BaZrO3 by inducing an overall saturation of the real part of the dielectric response, for temperatures below ~ 40 K. Two fine structures in the real part, as well as in the imaginary part, of dielectric response are further observed around 50-65 K and 15 K, respectively. Microscopic origins (e.g., unavoidable defects and oxygen octahedra rotation occurring at a local scale) of such anomalies are suggested. Finally, possible reasons for the facts that some of these dielectric anomalies have not been previously reported in the better studied KTaO3 and SrTiO3 incipient ferroelectrics are also discussed.Comment: 8 pages, 5 figures, submitted to Physical Review

Low temperature superlattice in monoclinic PZT

TEM has shown that the strongly piezoelectric material Pb(Zr0.52Ti0.48)O3 separates into two phases at low temperatures. The majority phase is the monoclinic phase previously found by x-ray diffraction. The minority phase, with a nanoscale coherence length, is a slightly distorted variant of the first resulting from the anti-phase rotation of the oxygen octahedra about [111]. This work clears up a recent controversy about the origin of superlattice peaks in these materials, and supports recent theoretical results predicting the coexistence of ferroelectric and rotational instabilities.Comment: REVTeX4, 4 eps figures embedded. JPG version of figs. 2&4 is also include

Phase diagram of the ferroelectric-relaxor (1-x)PbMg(1/3)Nb(2/3)O3-xPbTiO3

Synchrotron x-ray powder diffraction measurements have been performed on unpoled ceramic samples of (1-x)PbMg(1/3)Nb(2/3)O3-xPbTiO3 (PMN-xPT) with 30%<= x<= 39% as a function of temperature around the morphotropic phase boundary (MPB), which is the line separating the rhombohedral and tetragonal phases in the phase diagram. The experiments have revealed very interesting features previously unknown in this or related systems. The sharp and well-defined diffraction profiles observed at high and intermediate temperatures in the cubic and tetragonal phases, respectively, are in contrast to the broad features encountered at low temperatures. These peculiar characteristics, which are associated with the monoclinic phase of MC-type previously reported by Kiat et al and Singh et al., can only be interpreted as multiple coexisting structures with MC as the major component. An analysis of the diffraction profiles has allowed us to properly characterize the PMN-xPT phase diagram and to determine the stability region of the monoclinic phase, which extends from x= 31% to x= 37% at 20 K. The complex lansdcape of observed phases points to an energy balance between the different PMN-xPT phases which is intrinsically much more delicate than that of related systems such as PbZr(1-x)TixO3 or (1-x)PbZn(1/3)Nb(1/3)O3-xPbTiO3. These observations are in good accord with an optical study of x= 33% by Xu et al., who observed monoclinic domains with several different polar directions coexisting with rhombohedral domains, in the same single crystal.Comment: REVTeX4, 11 pages, 10 figures embedde

Transition Matrix Monte Carlo Reweighting and Dynamics

We study an induced dynamics in the space of energy of single-spin-flip Monte Carlo algorithm. The method gives an efficient reweighting technique. This dynamics is shown to have relaxation times proportional to the specific heat. Thus, it is plausible for a logarithmic factor in the correlation time of the standard 2D Ising local dynamics.Comment: RevTeX, 5 pages, 3 figure

Underpinning excellence in higher education – an investigation into the leadership, governance and management behaviours of high-performing academic departments

The changes in government funding alongside external pressures of increased international and national competition have meant that higher education institutions need to excel in a turbulent environment. The leadership, governance and management (LGM) of academic departments are key concerns. This study investigates the correlation between behaviours, attitudes and competencies at a department level and overall departmental performance in terms of hard data measures. The research question this paper seeks to address is: what are the LGM behaviours that are associated with high-performance in academic departments? More than 600 people across 50 academic departments in 5 UK universities were surveyed through the use of three research phases consisting of open-ended questionnaires, critical case sampled semi-structured interviews and a fixed-response survey. Synthesising the data and findings of the study revealed a thematic framework of eight broad themes that contribute to excellence in academic departments. These were in the areas of change management, research and teaching, communication, strategy and shared values, leadership, departmental culture, rewards and staffing. The behaviours associated with each of these themes were used to construct the Underpinning Excellence model

Landau model for uniaxial systems with complex order parameter

We study the Landau model for uniaxial incommensurate-commensurate systems of the I class by keeping Umklapp terms of third and fourth order in the expansion of the free energy. It applies to systems in which the soft mode minimum lies between the corresponding commensurate wave numbers. The minimization of the Landau functional leads to the sine-Gordon equation with two nonlinear terms, equivalent to the equation of motion for the well-known classical mechanical problem of two mixing resonances. We calculate the average free energies for periodic, quasiperiodic and chaotic solutions of this equation, and show that in the regime of finite strengths of Umklapp terms only periodic solutions are absolute minima of the free energy, so that the phase diagram contains only commensurate configurations. The phase transitions between neighboring configurations are of the first order, and the wave number of ordering goes through harmless staircase with a finite number of steps. These results are the basis for the interpretation of phase diagrams for some materials from the I class of incommensurate-commensurate systems, in particular of those for A$_2$BX$_4$ and BCCD compounds. Also, we argue that chaotic barriers which separate metastable periodic solutions represent an intrinsic mechanism for observed memory effects and thermal hystereses.Comment: 12 pages, 14 figures, LaTeX, to be published in Phys. Rev.

Competing orders in PZN-xPT and PMN-xPT relaxor ferroelectrics

Neutron and x-ray scattering studies on relaxor ferroelectric systems Pb(Zn$_{1/3}$Nb$_{2/3}$)O$_3$ (PZN), Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_3$ (PMN), and their solid solutions with PbTiO$_3$ (PT) have shown that inhomogeneities and disorder play important roles in the materials properties. Although a long-range polar order can be established at low temperature - sometimes with the help of an external electric field; short-range local structures called the ``polar nano-regions'' (PNR) still persist. Both the bulk structure and the PNR have been studied in details. The coexistence and competition of long- and short-range polar orders and how they affect the structural and dynamical properties of relaxor materials are discussed.Comment: Article submitted for JPSJ Special Topics (Novel States of Matter Induced by Frustration

Geographic patterns of mtDNA and Z-linked sequence variation in the Common Chiffchaff and the ‘chiffchaff complex’

We are grateful to the University of Washington Burke Museum (UWBM), US National Museum of Natural History (USNM), National History Museum Belgrade (NHMBEO), State Darwin Museum (SDM), Zoological Museum of Moscow State University (MSUZM), Yale Peabody Museum (YPM), University of Minnesota Bell Museum (MMNH), Texas A&M University Biodiversity Research and Teaching Collections (TCWC), Staffan Bensch, Stephen Menzie and Nigel Odin for sample loans. This is publication number 1585 of the Biodiversity Research and Teaching Collections at Texas A&M University. Funding: This work was supported by FEDER funds through the COMPETE programme, POPH/QREN/FSE funds to S.V.D. and NORTE2020/PORTUGAL funds (NORTE-01-0145-FEDER-AGRIGEN) to R.J.L., by the Fundação para a Ciência e a Tecnologia/MEC to S.V.D. (FCOMP-01-0124-FEDER-008941; PTDC/BIA- BEC/103435/2008) and R.J.L (SFRH/BPD/84141/2012), by the National Geographic Society to S.V.D, by Torino University Grant ex 60% 2017 and 2018 to M. P. and by Ministarstvo Kulture I Informisanja Republike Srbije (Project: Ptice zapadnog palearktika) to M.R. The Russian Science Foundation grant No. 14-50-00029 'Scientific basis of the national biobank – depository of living systems' (to E.A.K). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The Russian Science Foundation grant No. 14-50-00029 'Scientific basis of the national biobank – depository of living systems' (to E.A.K).Peer reviewedPublisher PD