2,987 research outputs found

    A resource survey of the coastal lands from Vlaming Head to Tantabiddi Well, West Cape Range region

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    The report comprise four parts; a brief review of the area\u27s climate, discussion of the geomorphology of the major landform units, an assessment of the potential erosion hazards of the surveyed landforms, and recommendations for development

    Rapid and quantitative determination of hexanal in cooked muscle foods

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    A simple and rapid method was developed to quantify hexanaJ in cooked muscle foods. The method involves extraction of the 2,4-dinitrophenylhydrazones of carbonyls with hexane and their separation by reversed-phased high performance liquid chromatography. The method compared well with the classical thiobarbituric acid test. The method was successfully used to quantify hexana) in cooked beef and pork burgers during storage at 4 °C for up to 1 week as well as in cooked turkey burgers after diet supplementation with vitamin E. After 7 days' storage at 4 °C, the contents of hexanal increased from 0.71 to 22.50 μ.mol/kg in beef burgers, from 0.89 to 32.7S μmol / kg in pork burgers and from 1.31 to S2.16 μmol / kg in turkey burgers (20 mg vitamin E per kg feed). Supplementation of turkey feeds with 600 mg Yitamin E per kg resulted in a 24% reduction in hexanal content in cooked turkey burgers after storage for 7 days at 4 °C, compared to the control (unsupplemented) group

    A DEM study of silo discharge of a cohesive solid

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    Bulk handling of powders and granular solids is common in many industries and often gives rise to handling difficulties especially when the material exhibits complex cohesive behaviour. For example, high storage stresses in a silo can lead to high cohesive strength of the stored solid, which may in turn cause blockages such as ratholing or arching near the outlet during discharge. This paper presents a Discrete Element Method study of discharge of a granular solid with varying levels of cohesion from a flat-bottomed silo. The DEM simulations were conducted using the commercial EDEM code with a recently developed DEM contact model for cohesive solids implemented through an API. The contact model is based on an elasto-plastic contact with adhesion and uses hysteretic non-linear loading and unloading paths to model the elastic-plastic contact deformation. The adhesion parameter is a function of the maximum contact overlap. The model has been shown to be able to predict the stress history dependent behaviour depicted by a flow function of the material. The effects of cohesion on the discharge rate and flow pattern in the silo are investigated. The predicted discharge rates are compared for the varying levels of cohesion and the effect of adhesion is evaluated. The ability of the contact model to qualitatively predict the phenomena that are present in the discharge of a silo has been shown with the salient feature of mixed flow from a flat bottomed hopper identified in the simulation

    An ultra-bright atom laser

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    We present a novel, ultra-bright atom-laser and ultra-cold thermal atom beam. Using rf-radiation we strongly couple the magnetic hyperfine levels of 87Rb atoms in a magnetically trapped Bose-Einstein condensate. At low rf-frequencies gravity opens a small hole in the trapping potenital and a well collimated, extremely bright atom laser emerges from just below the condensate. As opposed to traditional atom lasers based on weak coupling, this technique allows us to outcouple atoms at an arbitrarily large rate. We demonstrate an increase in flux per atom in the BEC by a factor of sixteen compared to the brightest quasi-continuous atom laser. Furthermore, we produce by two orders of magnitude the coldest thermal atom beam to date (200 nK).Comment: 20 pages, 9 figures, supplementary material online at http://www.bec.g

    Cosmic Strings from Supersymmetric Flat Directions

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    Flat directions are a generic feature of the scalar potential in supersymmetric gauge field theories. They can arise, for example, from D-terms associated with an extra abelian gauge symmetry. Even when supersymmetry is broken softly, there often remain directions in the scalar field space along which the potential is almost flat. Upon breaking a gauge symmetry along one of these almost flat directions, cosmic strings may form. Relative to the standard cosmic string picture based on the abelian Higgs model, these flat-direction cosmic strings have the extreme Type-I properties of a thin gauge core surrounded by a much wider scalar field profile. We perform a comprehensive study of the microscopic, macroscopic, and observational characteristics of this class of strings. We find many differences from the standard string scenario, including stable higher winding mode strings, the dynamical formation of higher mode strings from lower ones, and a resultant multi-tension scaling string network in the early universe. These strings are only moderately constrained by current observations, and their gravitational wave signatures may be detectable at future gravity wave detectors. Furthermore, there is the interesting but speculative prospect that the decays of cosmic string loops in the early universe could be a source of ultra-high energy cosmic rays or non-thermal dark matter. We also compare the observational signatures of flat-direction cosmic strings with those of ordinary cosmic strings as well as (p,q) cosmic strings motivated by superstring theory.Comment: 58 pages, 16 figures, v2. accepted to PRD, added comments about baryogenesis and boosted decay products from cusp annihilatio

    When Political Will Is Not Enough: Jails, Communities, and Persons With Mental Health Disorders

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    This article describes a project that generated the recommendations of a panel of experts regarding the jail as a venue for the delivery of behavioral health care services. The project was a component of the MacArthur Foundation’s Safety and Justice Challenge initiative, which seeks to address over-incarceration by changing the way jails are conceptualized and used. The recommendations were grounded largely in the sequential intercept model that rests on two core principles: minimize the inappropriate penetration of persons with mental illness into the criminal justice system and recognize that the community is the unit of analysis to address criminal justice–mental health problems successfully. Other topics presented in the context of the initiative included bringing the community to scale, jail diversion, the limits of jail responsibility, and the Affordable Care Act’s role in providing insurance coverage for detainees

    How Community Organizations Promote Continuity of Care for Young People with Mental Health Problems

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    Young people between the ages of 16 and 25 who experience mental health problems experience transitions and need help from a variety of organizations. Organizations promote continuity of care by assisting young adults with developmental, service, and systemic transitions. Providers offer specific services to help transitions and also form cooperative relationships with other community organizations. Results from a survey of 100 service providers in one community describe organizational attributes and practices which are associated with continuity of care in a regional system for young adults. Data analyses show that full-service organizations which practice cultural competence offer more specific services that foster continuity of care. Larger, full-service organizations are also more likely to have more extensive and collaborative inter-organizational networks that help young adults continue care over time within the regional system of care

    Conceptualisation of an Efficient Particle-Based Simulation of a Twin-Screw Granulator

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    Discrete Element Method (DEM) simulations have the potential to provide particle-scale understanding of twin-screw granulators. This is difficult to obtain experimentally because of the closed, tightly confined geometry. An essential prerequisite for successful DEM modelling of a twin-screw granulator is making the simulations tractable, i.e., reducing the significant computational cost while retaining the key physics. Four methods are evaluated in this paper to achieve this goal: (i) develop reduced-scale periodic simulations to reduce the number of particles; (ii) further reduce this number by scaling particle sizes appropriately; (iii) adopt an adhesive, elasto-plastic contact model to capture the effect of the liquid binder rather than fluid coupling; (iv) identify the subset of model parameters that are influential for calibration. All DEM simulations considered a GEA ConsiGma™ 1 twin-screw granulator with a 60° rearward configuration for kneading elements. Periodic simulations yielded similar results to a full-scale simulation at significantly reduced computational cost. If the level of cohesion in the contact model is calibrated using laboratory testing, valid results can be obtained without fluid coupling. Friction between granules and the internal surfaces of the granulator is a very influential parameter because the response of this system is dominated by interactions with the geometry

    Nuclear rockets based on graphite reactor technology - Their applications and development status

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    Development and mission applications of nuclear rockets based on graphite reactor technolog
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