Application of a corona onset criterion to calculation of corona onset voltage of stranded conductors

The conditions under which corona first occurs for any set of electrodes are an important design consideration since corona can limit the performance of any given configuration of electrical conductors. Here, the 60 Hz ac corona onset voltage for a stranded wire in air is calculated. The criterion involves the characteristics, i.e. composition and pressure, of the gas in which the conductor is immersed and the electric field in the vicinity of the conductor surface. It is found that the calculated corona onset voltage agrees reasonably well with experimental data and that its behavior as a function of overall conductor radius and number of strands is as expected.     

Study of a Mo–Au TES deposited directly on a freestanding membrane

Transition edge sensor devices made with Mo–Au proximity bilayer thermometers have been fabricated. The bilayers were DC-sputter deposited directly on 250 nm thick pre-etched Si₃N₄ membranes. Mo was deposited at 700°C, whereas Au was deposited at room temperature in the same pumpdown in order to allow for a good proximity effect. The superconducting transition temperature of devices with 43 nm Mo and 200 nm Au was around 190 mK. The transition width of bilayers deposited on membranes was substantially larger than those measured on samples deposited on the bulk substrate in the same fabrication run (≈2 mK). We consider this difference to be the result of a large temperature gradient across the membrane during the deposition process. Devices were tested with a single stage SQUID array kept at 2.2 K. The resolution of a device that has a transition width of 30 mK is 30 eV at 6 keV. A detailed study shows that the detector noise roughly scales with I₀, confirming the importance of thermal fluctuation noise in the thermometer.     

Implicit Non-Rigid Structure-from-Motion with Priors

This paper describes an approach to implicit Non-Rigid Structure-from-Motion based on the low-rank shape model. The main contributions are the use of an implicit model, of matching tensors, a rank estimation procedure, and the theory and implementation of two smoothness priors. Contrarily to most previous methods, the proposed method is fully automatic: it handles a substantial amount of missing data as well as outlier contaminated data, and it automatically estimates the degree of deformation. A major problem in many previous methods is that they generalize badly. Although the estimated model fits the visible training data well, it often predicts the missing data badly. To improve generalization a temporal smoothness prior and a surface shape prior are developed. The temporal smoothness prior constrains the camera trajectory and the configuration weights to behave smoothly. The surface shape prior constrains consistently close image point tracks to have similar implicit structure. We propose an algorithm for achieving a Maximum A Posteriori (map) solution and show experimentally that the map-solution generalizes far better than the prior-free Maximum Likelihood (ml) solution.     

Rigorous identification and encoding of trace-links in model-driven engineering

Model-driven engineering (MDE) involves the construction and manipulation of many models of different kinds in an engineering process. In principle, models can be used in the product engineering lifecycle in an end-to-end manner for representing requirements, designs and implementations, and assisting in deployment and maintenance. The manipulations applied to models may be manual, but they can also be automated??for example, using model transformations, code generation, and validation. To enhance automated analysis, consistency and coherence of models used in an MDE process, it is useful to identify, establish and maintain trace-links between models. However, the breadth and scope of trace-links that can be used in MDE is substantial, and managing trace-link information can be very complex. In this paper, we contribute to managing the complexity of traceability information in MDE in two ways: firstly, we demonstrate how to identify the different kinds of trace-links that may appear in an end-to-end MDE process; secondly, we describe a rigorous approach to defining semantically rich trace-links between models, where the models themselves may be constructed using diverse modelling languages. The definition of rich trace-links allows us to use tools to maintain and analyse traceability relationships.     

In vitro stimulation of human peripheral blood B cells from normal individuals by activated T cells increases the efficiency of hybridoma generation

Peripheral blood B cells from normal individuals have been less than ideal as a resource for "fusible" cells for the generation of human hybridoma antibodies. In vitro stimulation of normal peripheral blood B cells by CD4+ T cells (HUT 78) that had been activated by a solid phase anti-CD3 monoclonal antibody (OKT3) was investigated to see if differentiation of B cells would result in an increased pool of B cells that could be immortalized. A comparison of the rate of successful fusion, an estimation of the frequency of the fusible cells from the input peripheral blood, and the amount of immunoglobulin secreted both in vitro, prior to fusion, and by the resulting clones in two different in vitro immunization protocols, with and without activated T cells indicated that inclusion of the activated T cells provided the necessary help to drive the B cells to a fusible state. Stimulation by activated T cells improves the efficiency of generating B cell hybrid clones from peripheral blood 10-fold compared to in vitro immunization with antigen alone.     

Temporal trends in hospital-based episodes of asthma care in a health maintenance organization

Studies reporting increased asthma hospitalizations and mortality in the United States and abroad have heightened concern about the changing epidemiology of asthma. We studied 20-yr patterns of acute asthma care occurring at two large community hospitals among members of a large health maintenance organization. The presentation focuses on the conceptualization and operationalization of an "episode" of asthma care, defined as a collection of encounters (emergency room visits, urgency care visits, and hospital admissions) that cluster in time, as well as on changes in episode rates over time. We found a statistically significant increase in asthma episodes among boys younger than 5 yr of age that continued unabated from 1967 to 1987 despite a drop in asthma hospitalization rates starting in 1985. We hypothesize that this difference may reflect a change in emergency room management practices and not a true change in the underlying epidemiology of asthma. The concept of an episode of acute asthma care has not been studied in the literature and represents a potentially useful methodologic innovation. Particularly in the context of managed health care systems, studies of such episodes may be less sensitive than studies of hospital admissions to changes in the organization and delivery of acute asthma care, and thus may be better suited for studying changes in the epidemiology of asthma.     

Biomechanical measurements of axial crush injury to the distal condyles of human and synthetic femurs

Few studies have evaluated the 'bulk' mechanical properties of human longbones and even fewer have compared human tissue to the synthetic longbones increasingly being used by researchers. Distal femur fractures, for example, comprise about 6% of all femur fractures, but the mechanical properties of the distal condyles of intact human and synthetic femurs have not been well quantified in the literature. To this end, the distal portions of a series of 16 human fresh-frozen femurs and six synthetic femurs were prepared identically for mechanical testing. Using a flat metal plate, an axial 'crush' force was applied in-line with the long axis of the femurs. The two femur groups were statistically compared and values correlated to age, size, and bone quality. Results yielded the following: crush stiffness (human, 1545 +/- 728 N/mm; synthetic, 3063 +/- 1243 N/mm; p = 0.002); crush strength (human, 10.3 +/- 3.1 kN; synthetic, 12.9 < or = 1.7 kN; p = 0.074); crush displacement (human, 6.1 +/- 1.8 mm; synthetic, 2.8 +/- 0.3 mm; p = 0.000); and crush energy (human, 34.8 +/- 15.9J; synthetic, 18.1 +/- 5.7J; p = 0.023). For the human femurs, there were poor correlations between mechanical properties versus age, size, and bone quality (R2 < or = 0.18), with the exception of crush strength versus bone mineral density (R2 = 0.33) and T-score (R2 = 0.25). Human femurs failed mostly by condyle 'roll back' buckling (15 of 16 cases) and/or unicondylar or bicondylar fracture (7 of 16 cases), while synthetic femurs all failed by wedging apart of the condyles resulting in either fully or partially displaced condylar fractures (6 of 6 cases). These findings have practical implications on the use of a flat plate load applicator to reproduce real-life clinical failure modes of human femurs and the appropriate use of synthetic femurs. To the authors' knowledge, this is the first study to have done such an assessment on human and synthetic femurs.     

Asymmetries in Global-Local Processing Ability in Elderly People With the Apolipoprotein E-ε4 Allele.

Previous studies have identified cognitive asymmetries in elderly people at increased risk for Alzheimer's disease (AD) by comparing standardized neuropsychological tests of verbal and spatial abilities in both preclinical AD and apolipoprotein ε4+ elderly groups. This prospective study investigated cognitive asymmetries within a single test by comparing cognitively intact elderly (with and without the ε4+ allele) on a learning and memory measure that uses global and local visuospatial stimuli. Both groups demonstrated comparable overall learning and recall. But the ε4+ group had a significantly larger discrepancy between their global and local learning scores and had a greater proportion of individuals with more than a one standard deviation difference between their immediate recall of the global and local elements, relative to the ε4- group. These findings build on previous studies identifying subgroups of elderly people at greater risk for AD who often demonstrate increased cognitive asymmetries relative to groups without significant risk factors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Physical and Mechanical Properties of Biobased Materials Starch,Polylactate and Polyhydroxybutyrate

Commercial and semi‐commercial biobased materials (Polylactate, PLA, polyhydroxy‐butyrate, PHB, wheat starch and corn starch) were investigated. Physical and mechanical characterisation (tensile strength, elongation, tear strength, compression, gas permeability (CO₂ and O₂) and water vapour permeability (WVP)) was examined. Tests on both films and cups show potential use of these materials for primary food packaging, especially PLA and PHB. An interesting O₂:CO₂ permeability ratio (1:7 to 1:12) was seen, which make these materials suitable for packaging of food with high respiration. The mechanical properties were comparable to conventional materials such as polyethylene (PE) and polystyrene (PS). The WVP measured on films ranged from 12.6 to 18.6 [g H₂O/(m² ? 24h)], and on cups the range was 2.2 to 10.5 [g H₂O ? 700 μm/(m² ? 24h)]. The WVP for the starch‐based materials seems to be the most crucial parameter, and needs improvement if these materials are to be used as food packaging.