17,477 research outputs found

    'POWs and purge victims: attitudes towards party rehabilitation, 1956-57'

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    In the wake of Stalin's death in 1953 and Khrushchev's Secret Speech three years later, many Soviet citizens hoped that past injustices would now be put right. For some, this meant the right to rejoin the Communist Party. This article explores how former party members - including many returning from the camps - sought rehabilitation in the years 1956 to 1957. Focusing in particular on the party organization in Vladimir province, the article examines the differing ways POWs and purge victims were treated, and asks how far the decisions made by the party elite in this oblast' reflected central policy or local concerns

    The prenatal effects of the Christchurch earthquake on executive function at five years of age : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Educational Psychology at Massey University

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    Despite the frequency of earthquakes, particularly in New Zealand, little is known about the long-term effects that they can have on vulnerable populations, such as mothers and unborn babies. This study looks at the way in which a major earthquake can impact on neurodevelopment, specifically the executive function (EF) abilities of children five years following the disaster. The aims of this study were to determine if prenatal earthquake exposure had an effect on EF, to determine how timing of exposure influenced EF, if there were different EF outcomes for boys and girls, and how maternal perceptions of severity influenced the child’s EF. Children from two groups (mothers from Christchurch who experienced the earthquakes and mothers from Dunedin and Timaru who did not) had their EF measured by a self-administered parent questionnaire, the Behaviour Rating Inventory of Executive Function Second Edition (BRIEF 2). Maternal demographics and earthquake severity experiences were gathered through a second self-administered questionnaire. This study found that children who prenatally experienced the earthquake had significantly worse scores on the measures of emotional control and emotional regulation than the standardised average provided by the BRIEF 2. Exposure during the third trimester was associated with the most significant increases in EF compared to children exposed during the second trimester and the standardised average. In addition to emotional control and emotional regulation difficulties, Christchurch boys also exhibited significantly higher scores on the Shift scale. Results also showed that the worse someone close to the mother was injured, the higher the child’s scores on the Inhibit, Organisation, and Emotional Control scale, and the Behaviour Regulation index (BRI) were. Also, children of mothers who reported more significantly injuring themselves in the earthquake had higher Emotional Regulation (ERI) scores. Children whose mothers reported being overall extremely stressed by the earthquake had the largest mean difference in emotional control and ERI scores compared to the standardised average. Despite the small group sizes and continuing aftershocks the variations in trimester and maternal perception of stress indicates that prenatal exposure to a natural disaster does impact EF

    Uniform in time estimates for the weak error of the Euler method for SDEs and a Pathwise Approach to Derivative Estimates for Diffusion Semigroups

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    We present a criterion for uniform in time convergence of the weak error of the Euler scheme for Stochastic Differential equations (SDEs). The criterion requires i) exponential decay in time of the space-derivatives of the semigroup associated with the SDE and ii) bounds on (some) moments of the Euler approximation. We show by means of examples (and counterexamples) how both i) and ii) are needed to obtain the desired result. If the weak error converges to zero uniformly in time, then convergence of ergodic averages follows as well. We also show that Lyapunov-type conditions are neither sufficient nor necessary in order for the weak error of the Euler approximation to converge uniformly in time and clarify relations between the validity of Lyapunov conditions, i) and ii). Conditions for ii) to hold are studied in the literature. Here we produce sufficient conditions for i) to hold. The study of derivative estimates has attracted a lot of attention, however not many results are known in order to guarantee exponentially fast decay of the derivatives. Exponential decay of derivatives typically follows from coercive-type conditions involving the vector fields appearing in the equation and their commutators; here we focus on the case in which such coercive-type conditions are non-uniform in space. To the best of our knowledge, this situation is unexplored in the literature, at least on a systematic level. To obtain results under such space-inhomogeneous conditions we initiate a pathwise approach to the study of derivative estimates for diffusion semigroups and combine this pathwise method with the use of Large Deviation Principles.Comment: 47 pages and 9 figure

    New insights into the biomechanics of Legg-Calvé-Perthes’ disease: The role of epiphyseal skeletal immaturity in vascular obstruction

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    ObjectivesLegg–Calvé–Perthes’ disease (LCP) is an idiopathic osteonecrosis of the femoral head that is most common in children between four and eight years old. The factors that lead to the onset of LCP are still unclear; however, it is believed that interruption of the blood supply to the developing epiphysis is an important factor in the development of the condition.MethodsFinite element analysis modelling of the blood supply to the juvenile epiphysis was investigated to understand under which circumstances the blood vessels supplying the femoral epiphysis could become obstructed. The identification of these conditions is likely to be important in understanding the biomechanics of LCP.ResultsThe results support the hypothesis that vascular obstruction to the epiphysis may arise when there is delayed ossification and when articular cartilage has reduced stiffness under compression.ConclusionThe findings support the theory of vascular occlusion as being important in the pathophysiology of Perthes disease

    Multiband radar characterization of forest biomes

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    The utility of airborne and orbital SAR in classification, assessment, and monitoring of forest biomes is investigated through analysis of orbital synthetic aperature radar (SAR) and multifrequency and multipolarized airborne SAR imagery relying on image tone and texture. Preliminary airborne SAR experiments and truck-mounted scatterometer observations demonstrated that the three dimensional structural complexity of a forest, and the various scales of temporal dynamics in the microwave dielectric properties of both trees and the underlying substrate would severely limit empirical or semi-empirical approaches. As a consequence, it became necessary to develop a more profound understanding of the electromagnetic properties of a forest scene and their temporal dynamics through controlled experimentation coupled with theoretical development and verification. The concatenation of various models into a physically-based composite model treating the entire forest scene became the major objective of the study as this is the key to development of a series of robust retrieval algorithms for forest biophysical properties. In order to verify the performance of the component elements of the composite model, a series of controlled laboratory and field experiments were undertaken to: (1) develop techniques to measure the microwave dielectric properties of vegetation; (2) relate the microwave dielectric properties of vegetation to more readily measured characteristics such as density and moisture content; (3) calculate the radar cross-section of leaves, and cylinders; (4) improve backscatter models for rough surfaces; and (5) relate attenuation and phase delays during propagation through canopies to canopy properties. These modeling efforts, as validated by the measurements, were incorporated within a larger model known as the Michigan Microwave Canopy Scattering (MIMICS) Model

    Long-time behaviour of degenerate diffusions: UFG-type SDEs and time-inhomogeneous hypoelliptic processes

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    We study the long time behaviour of a large class of diffusion processes on RNR^N, generated by second order differential operators of (possibly) degenerate type. The operators that we consider {\em need not} satisfy the H\"ormander condition. Instead, they satisfy the so-called UFG condition, introduced by Herman, Lobry and Sussman in the context of geometric control theory and later by Kusuoka and Stroock, this time with probabilistic motivations. In this paper we study UFG diffusions and demonstrate the importance of such a class of processes in several respects: roughly speaking i) we show that UFG processes constitute a family of SDEs which exhibit multiple invariant measures and for which one is able to describe a systematic procedure to determine the basin of attraction of each invariant measure (equilibrium state). ii) We use an explicit change of coordinates to prove that every UFG diffusion can be, at least locally, represented as a system consisting of an SDE coupled with an ODE, where the ODE evolves independently of the SDE part of the dynamics. iii) As a result, UFG diffusions are inherently "less smooth" than hypoelliptic SDEs; more precisely, we prove that UFG processes do not admit a density with respect to Lebesgue measure on the entire space, but only on suitable time-evolving submanifolds, which we describe. iv) We show that our results and techniques, which we devised for UFG processes, can be applied to the study of the long-time behaviour of non-autonomous hypoelliptic SDEs and therefore produce several results on this latter class of processes as well. v) Because processes that satisfy the (uniform) parabolic H\"ormander condition are UFG processes, our paper contains a wealth of results about the long time behaviour of (uniformly) hypoelliptic processes which are non-ergodic, in the sense that they exhibit multiple invariant measures.Comment: 66 page

    SIR-B measurements and modeling of vegetation

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    A summary is presented of the results derived from analysis of six SIR-B data takes over an agricultural test site in west central Illinois. The first part describes the procedure used to calibrate the SIR-B imagery, the second part pertains to the observed radar response to soil moisture content, and the last part examines the information derivable from multiangle observations