Conical refraction healing after partially blocking the input beam

In conical refraction, when a focused Gaussian beam passes along one of the optic axes of a biaxial crystal it is transformed into a pair of concentric bright rings at the focal plane. We demonstrate both theoretically and experimentally that this transformation is hardly affected by partially blocking the Gaussian input beam with an obstacle. We analyze the influence of the size of the obstruction both on the transverse intensity pattern of the beam and on its state of polarization, which is shown to be very robust

Conical refraction healing after partially blocking the input beam

In conical refraction, when a focused Gaussian beam passes along one of the optic axes of a biaxial crystal, it is transformed into a pair of concentric bright rings at the focal plane. We demonstrate both theoretically and experimentally that this transformation is hardly affected by partially blocking the Gaussian input beam with an obstacle. We analyze the influence of the size of the obstruction both on the transverse intensity pattern of the beam and on its state of polarization, which is shown to be very robust

Ce-doped Li6Ln(BO3)3 (Ln = Y, Gd) Single crystals fibers grown by micro-pulling down method and luminescence properties

Ce3+-doped borate crystal fibers of Li6Gd(BO 3)3 (LGBO) and Li6Y(BO3)3 (LYBO) compositions are grown by the micro-pulling down (μ-PD) method for potential application in developing new neutron detectors. The ternary equilibrium diagram of Li2O-Gd2O3-B 2O3 is drawn and the preparations of homogeneous mixed LGBO and LYBO powders and growth conditions for single crystal fibers are discussed. Absorption, excitation and X-ray luminescence spectra are investigated. Absolute light yield derived from energy spectra and kinetic decay curves measured under α- and γ-scintillations of Ce 3+-doped LGBO and LYBO single crystal fibers is provided. © 2012 Elsevier B.V. All rights reserved

Has education lost sight of children?

The reflections presented in this chapter are informed by clinical and personal experiences of school education in the UK. There are many challenges for children and young people in the modern education system and for the professionals who support them. In the UK, there are significant gaps between the highly selective education provided to those who pay privately for it and to the majority of those educated in the state-funded system. Though literacy rates have improved around the world, many children, particularly boys, do not finish their education for reasons such as boredom, behavioural difficulties or because education does not ‘pay’. Violence, bullying, and sexual harassment are issues faced by many children in schools and there are disturbing trends of excluding children who present with behavioural problems at school whose origins are not explored. Excluded children are then educated with other children who may also have multiple problems which often just make the situation worse. The experience of clinicians suggests that school-related mental health problems are increasing in severity. Are mental health services dealing with the consequences of an education system that is not meeting children’s needs? An education system that is testing- and performance-based may not be serving many children well if it is driving important decisions about them at increasingly younger ages. Labelling of children and setting them on educational career paths can occur well before they reach secondary schools, limiting potential very early on in their developmental trajectory. Furthermore, the emphasis at school on testing may come at the expense of creativity and other forms of intelligence, which are also valuable and important. Meanwhile the employment marketplace requires people with widely different skills, with an emphasis on innovation, creativity, and problem solving. Is education losing sight of the children it is educating

Электроснабжение станции нагрева нефти в скважине от ветроэлектрической установки

In this article, the authors reviewed a new technology to prevent the formation of asphalt-resin-paraffin deposits by the thermal method of electrothermal impact on the oil wellbore shaft using a wind-electric installation as an autonomous power source. The advantage of this thermal stimulation technique lies in its continuous nature, which will allow keeping the clear opening of the tubing constant. The scheme of the autonomous system for down-hole electric heating of oil is presented. A tubular or induction heater can serve as an electric heating element placed in the well. The heating element of the system can be used in the wells exploited by freeflow, gas lift and mechanized methods, while its installation does not require an overhaul. The paraffin oil saturation temperature and temperature distribution over the depth of the well were defined. The amount of heat, which must be transferred to the oil mixture in the tubing in order to ensure effective operation of the well, taking into account the dynamic state of the system, is calculated. The optimal depth of the heating element's location in the well and its power was determined. The calculation of the required power for wind-electric installation to maintain the set temperature in the wellbore was performed. Having conducted the studies, it was revealed that in order to prevent the asphalt-resin-paraffin deposits formation on the tubing walls of oil wells, it is expedient to use the in-line heater, which maintains the average steady-state temperature along the wellbore and at the wellhead above the initial crystallization point of the asphaltresin-paraffin deposits. The application of the developed electrothermal system is relevant in the conditions of formation of asphalt-resin-paraffin deposits in the wellbore shaft at the fields, which do not have a connection to the centralized power grid.Рассмотрена новая технология предупреждения образования асфальтосмолопарафиновых отложений тепловым методом электротермического воздействия на ствол нефтяной скважины с применением ветроэлектрической установки в качестве автономного источника питания. Достоинством данного теплового способа воздействия является его непрерывный характер, что позволяет сохранять пропускное сечение насосно-компрессорных труб постоянным. Представлена схема автономного комплекса для внутрискважинного электропрогрева нефти. В качестве электронагревательного элемента, размещаемого в скважине, может выступать трубчатый или индукционный нагреватель. Нагревательный элемент комплекса может применяться в скважинах, эксплуатируемых фонтанным, газлифтным и механизированным способами, при этом для его установки не требуется проведения капитального ремонта. Определены температура насыщения нефти парафином и ее распределение по глубине скважины. Рассчитано количество теплоты, которое необходимо сообщить скважинной продукции в насосно-компрессорных трубах для обеспечения эффективного режима эксплуатации скважины с учетом динамического состояния системы. Установлены оптимальная глубина расположения нагревательного элемента в скважине и его мощность. Выполнен расчет необходимой мощности ветроэлектрической установки для поддержания заданной температуры в стволе скважины. Проведенные исследования показали, что для предотвращения образования асфальтосмолопарафиновых отложений на стенках насосно-компрессорных труб нефтяных скважин целесообразно использовать проточный электронагреватель, который обеспечивает поддержание средней установившейся температуры по стволу и на устье скважины выше точки начальной кристаллизации асфальтосмолопарафиновых отложений. Применение разработанного электротермического комплекса является актуальным в условиях образования асфальтосмолопарафиновых отложений в стволе скважины на месторождениях, не имеющих подключения к централизованной энергосистеме установки для поддержания заданной температуры в стволе скважины

Blue-detuned optical ring trap for Bose-Einstein condensates based on conical refraction

We present a novel approach for the optical manipulation of neutral atoms in annular light structures produced by the phenomenon of conical refraction occurring in biaxial optical crystals. For a beam focused to a plane behind the crystal, the focal plane exhibits two concentric bright rings enclosing a ring of null intensity called the Poggendorff ring. We demonstrate both theoretically and experimentally that the Poggendorff dark ring of conical refraction is confined in three dimensions by regions of higher intensity. We derive the positions of the confining intensity maxima and minima and discuss the application of the Poggendorff ring for trapping ultra-cold atoms using the repulsive dipole force of blue-detuned light. We give analytical expressions for the trapping frequencies and potential depths along both the radial and the axial directions. Finally, we present realistic numerical simulations of the dynamics of a 87Rb Bose-Einstein condensate trapped inside the Poggendorff ring which are in good agreement with corresponding experimental results

Cognitive ability and physical health:A Mendelian randomization study

Causes of the association between cognitive ability and health remain unknown, but may reflect a shared genetic aetiology. This study examines the causal genetic associations between cognitive ability and physical health. We carried out two-sample Mendelian randomization analyses using the inverse-variance weighted method to test for causality between later life cognitive ability, educational attainment (as a proxy for cognitive ability in youth), BMI, height, systolic blood pressure, coronary artery disease, and type 2 diabetes using data from six independent GWAS consortia and the UK Biobank sample (N = 112 151). BMI, systolic blood pressure, coronary artery disease and type 2 diabetes showed negative associations with cognitive ability; height was positively associated with cognitive ability. The analyses provided no evidence for casual associations from health to cognitive ability. In the other direction, higher educational attainment predicted lower BMI, systolic blood pressure, coronary artery disease, type 2 diabetes, and taller stature. The analyses indicated no causal association from educational attainment to physical health. The lack of evidence for causal associations between cognitive ability, educational attainment, and physical health could be explained by weak instrumental variables, poorly measured outcomes, or the small number of disease cases

Behavioural Susceptibility Theory: Professor Jane Wardle and the Role of Appetite in Genetic Risk of Obesity

Purpose of Review: There is considerable variability in human body weight, despite the ubiquity of the 'obesogenic' environment. Human body weight has a strong genetic basis and it has been hypothesised that genetic susceptibility to the environment explains variation in human body weight, with differences in appetite being implicated as the mediating mechanism; so-called 'behavioural susceptibility theory' (BST), first described by Professor Jane Wardle. This review summarises the evidence for the role of appetite as a mediator of genetic risk of obesity. Recent Findings: Variation in appetitive traits is observable from infancy, drives early weight gain and is highly heritable in infancy and childhood. Obesity-related common genetic variants identified through genome-wide association studies show associations with appetitive traits, and appetite mediates part of the observed association between genetic risk and adiposity. Summary: Obesity results from an interaction between genetic susceptibility to overeating and exposure to an 'obesogenic' food environment