1,366 research outputs found

    The Li-7 and Be-7 deexcitation lines: Probes for accelerated particle transport models in solar flares

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    The photon energy spectrum of a spectral feature composed of the 429 and 478 keV gamma-ray lines from Li-7 and Be-7 (produced by interactions of flare-accelerated alpha particles with ambient He in the solar atmosphere) depends on the angular distribution of the interacting accelerated particles. This spectrum is calculated for limb and disc-centered flares using a loop model for the transport of the ions. In this model, the flux tube magnetic field is constant in the corona and converges in the chromosphere to the photosphere. Magnetic mirroring and MHD pitch-angle scattering are both taken into account. Comparison of these results with data from other experiments is presented

    Distribution-free partial discrimination procedures

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    AbstractThis paper reviews discrimination procedures which provide distribution-free control over the individual misclassification probabilities. Particular emphasis is placed on the two-population rank method developed by Broffitt, Randles and Hogg, which utilizes the general formulation of Quesenberry and Gessaman. It is shown that the rank method extends from two to three or more populations in a natural and flexible fashion. A Monte Carlo study compares two suggested extensions with others proposed by Broffitt

    Genetic characteristics of the V3 region associated with CXCR4 usage in HIV-1 subtype C isolates

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    CXCR4 coreceptor usage appears to occur less frequently among HIV-1 subtype C viruses. The aim of this study was to investigate the genetic determinants within the V3 region of subtype C isolates able to use CXCR4. Thirty-two subtype C isolates with known phenotypes (16 R5, 8 R5X4 and 8 X4 isolates) were assessed. A subtype C-specific V3 heteroduplex tracking assay (HTA) was used to determine sample complexity, and nucleotide sequencing analysis was used to compare characteristics associated with CCR5 and CXCR4-using isolates. There were sufficient genetic differences to discriminate between R5 viruses and those able to use CXCR4. In general, R5 isolates had an HTA mobility ratio >0 .9 whereas CXCR4-using isolates were usually < 0.9. Multiple bands were more frequently seen among the dualtropic isolates. Sequence analysis of the V3 region showed that CXCR4-using viruses were often associated with an increased positive amino acid charge, insertions and loss of a glycosylation site, similar to HIV-1 subtype B. In contrast, where subtype B consensus V3 has a GPGR crown motif irrespective of coreceptor usage, all 16 subtype C R5 viruses had a conserved GPGQ sequence at the tip of the loop, while 12 of the 16 (75%) CXCR4-using viruses had substitutions in this motif, most commonly arginine (R). These findings were confirmed using a larger published data set. We therefore suggest that changes within the crown motif of subtype C viruses might be an additional pathway to utilise CXCR4 and thus GPGQ may limit the potential for the development of X4 viruses

    Behaviors that Predict Personality Components in Adult free-Ranging Tibetan Macaques (Macaca thibetana)

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    To further the potential for applied personality studies, we present a methodology for assessing personality in nonhuman animals without a priori assumptions, using behavioral measures to discriminate personality survey results. Our study group consisted of 12 free-ranging, provisioned, adult Tibetan macaques (Macaca thibetana) at the Valley of the Wild Monkeys, China. We asked familiar Chinese park guards and scientists to rate each of the 12 macaques using 27-item personality surveys. We also recorded behavioral observations (\u3e 100 hrs) from August–September, 2012. The personality surveys showed reliability in 22 of the items that were then utilized in a principal component analysis that revealed five components: Insecurity, Reactivity, Boldness, Sociability, and Leadership. Prior personality research on Macaca show comparable components. In order to determine which behaviors would best predict those five personality components, we conducted ­discriminant analyses using behavioral measures as predictors. We found that behavioral measures of avoidance, lunging, fear-grinning, self-directed behaviors, touching, proximity and chasing could significantly predict personality component scores in certain situations. Finally, we analyzed the effects of situation (provisioning and tourists) and found situation influenced proximity and rates of avoidance and self-directed behaviors. Wider implementation of this methodology may permit long-term analysis of personality using behavioral proxies for established personality traits, in particular on research investigating the effects of tourism and provisioning on personality

    Comparison of 3-, 5-, and 6-Phase Machines for Automotive Charging Applications

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    In this paper, the performance of a 5-phase claw-pole machine/converter system is compared with those of 3-phase and 6-phase systems of the same volume. It is shown that the acoustic output of the 5-phase machine compares favorably with that of the 6-phase machine and is much lower than that of the 3-phase machine over a majority of the operating range. In addition, the output current produced by the 5-phase machine Is, in general, 6-8% higher than those of the 3-phase and 6-phase machines. These results suggest that for maximizing power density while minimizing cost and acoustic noise, 5-phase machines provide a competitive alternative to 6-phase machines of identical volume

    Incorporating the Effects of Magnetic Saturation in a Coupled-Circuit Model of a Claw-Pole Alternator

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    A method of representing the effects of magnetic saturation in a coupled-circuit model of a claw-pole alternator is presented. In the approach considered, the airgap flux density produced by each winding is expressed as a function of magnetic operating point. A challenge in the implementation is that the airgap flux densities consist of several significant harmonics, each of which changes at a distinct rate as iron saturates. Despite this complication, it is shown that relatively simple measurements can be used to determine model parameters. The model is implemented in the analysis of several alternator/rectifier systems using a commercial state-model-based circuit analysis program. Comparisons with experimental results over a wide range of speeds and operating conditions demonstrate its accuracy in predicting both the steady state and transient behavior of the systems

    Comparative Effectiveness of Smoking Cessation Medications among Schizophrenic Smokers

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    Objective: To examine which medication could lead to a higher short and long term smoking abstinence in patients with schizophrenia. Methods: A retrospective cohort study was conducted using General Electric (GE) medical records database (1995 – 2011). The cohort consisted of adult smokers with diagnosis of schizophrenia newly initiating cessation medication. Short term and long term outcomes of cessation were measured at 3 weeks and 1 year. Descriptive and chi-square analyses were used to determine the frequencies and associations of patient characteristics with the abstinence outcomes. Logistic regression models were carried out to determine the predictors of short term and long term abstinence. Results: The cohort consisted of 3,976 patients. Abstinence rate was highest for Varenicline, followed by Bupropion, NRT, and lastly combination at week 12. At one year, abstinence rate was highest for Varenicline, followed by combination, NRT, and lastly Bupropion. Age, race, household locations and receiving counseling were associated with abstinence. No significant differences were found between cessation medications. Conclusions: There were no statistically significant differences in quitting with type of cessation medication. Predictors of better abstinence identified included older age, white race, western household location. These factors should be considered when designing future interventions for schizophrenic population as this minority population may need more tailored approaches to achieve a successful cessation outcome

    Effects of perceptual learning on local stereopsis and neuronal responses of V1 and V2 in prism-reared monkeys.

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    Visual performance improves with practice (perceptual learning). In this study, we sought to determine whether or not adult monkeys reared with early abnormal visual experience improve their stereoacuity by extensive psychophysical training and testing, and if so, whether alterations of neuronal responses in the primary visual cortex (V1) and/or visual area 2 (V2) are involved in such improvement. Strabismus was optically simulated in five macaque monkeys using a prism-rearing procedure between 4 and 14 wk of age. Around 2 yr of age, three of the prism-reared monkeys ( trained monkeys) were tested for their spatial contrast sensitivity and stereoacuity. Two other prism-reared monkeys received no training or testing ( untrained monkeys). Microelectrode experiments were conducted around 4 yr of age. All three prism-reared trained monkeys showed improvement in stereoacuity by a factor of 7 or better. However, final stereothresholds were still approximately 10-20 times worse than those in normal monkeys. In V1, disparity sensitivity was drastically reduced in both the trained and untrained prism-reared monkeys and behavioral training had no obvious effect. In V2, the disparity sensitivity in the trained monkeys was better by a factor of approximately 2.0 compared with that in the untrained monkeys. These data suggest that the observed improvement in stereoacuity of the trained prism-reared monkeys may have resulted from better retention of disparity sensitivity in V2 and/or from learning by upstream neurons to more efficiently attend to residual local disparity information in V1 and V
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