5,897 research outputs found

    The Use and Content of Formal Rating Systems in Angel Group Investment Initial Screening Stages

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    We examined the formal screening process of thirty-eight Angel Investment Groups. Within our sample, over eighty percent of the Angel Investment Groups used a committee of members to perform the initial screening of submitted business plans, while the remaining relied upon the managing partner or senior director to perform the initial screening. Of the Angel Investment Groups that use a screening committee, approximately half also employed a formal scoring system. With respect to the important dimensions used in the scoring systems, the quality/experience of the management team and the competitive advantage of the firm's product or service, including strength of intellectual property protection, were consistently the most common dimensions seen in the scoring systems examined. A content analysis of the scoring sheets was also performed in order to determine the various sub-topics and linguistic themes associated with Angel rating systems

    Notification of pesticide poisoning in the western Cape, 1987 - 1991

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    There is a paucity of data on pesticide-related morbidity and mortality in South Africa. A review of notifications to the western Cape office of the Department of National Health and Population Development from 1987 to 1991 was undertaken to describe the epidemiological profile of pesticide poisoning in the region. Two hundred and twenty five cases of pesticide poisoning were identified, of which the majority were from rural areas. Farmers, farm workers and their families were most frequently involved in poisoning events, which included accidents arising outside of workplace production (44%), self-inflicted injury (35%) and direct occupational contamination (11%). Farm pesticide stores were the most frequent source of pesticide and a seasonal variation in the trend of poisoning events could be discerned; this corresponded to agricultural spraying practices in the region. The mortality rate was significantly higher among those with self-inflicted injury, particularly farm workers. A concurrent review of hospital admissions for 1991 found that 78% of cases had not been notified. In view of the key role of surveillance in reducing pesticide-related morbidity and mortality, a call is made to improve notification of pesticide poisoning so as to facilitate control of an important potential public health problem

    Fear Memory Retrieval Is Associated With a Reduction in AMPA Receptor Density at Thalamic to Amygdala Intercalated Cell Synapses

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    The amygdala plays a crucial role in attaching emotional significance to environmental cues. Its intercalated cell masses (ITC) are tight clusters of GABAergic neurons, which are distributed around the basolateral amygdala complex. Distinct ITC clusters are involved in the acquisition and extinction of conditioned fear responses. Previously, we have shown that fear memory retrieval reduces the AMPA/NMDA ratio at thalamic afferents to ITC neurons within the dorsal medio-paracapsular cluster. Here, we investigate the molecular mechanisms underlying the fear-mediated reduction in the AMPA/NMDA ratio at these synapses and, in particular, whether specific changes in the synaptic density of AMPA receptors underlie the observed change. To this aim, we used a detergent-digested freeze-fracture replica immunolabeling technique (FRIL) approach that enables to visualize the spatial distribution of intrasynaptic AMPA receptors at high resolution. AMPA receptors were detected using an antibody raised against an epitope common to all AMPA subunits. To visualize thalamic inputs, we virally transduced the posterior thalamic complex with Channelrhodopsin 2-YFP, which is anterogradely transported along axons. Using face-matched replica, we confirmed that the postsynaptic elements were ITC neurons due to their prominent expression of μ-opioid receptors. With this approach, we show that, following auditory fear conditioning in mice, the formation and retrieval of fear memory is linked to a significant reduction in the density of AMPA receptors, particularly at spine synapses formed by inputs of the posterior intralaminar thalamic and medial geniculate nuclei onto identified ITC neurons. Our study is one of the few that has directly linked the regulation of AMPA receptor trafficking to memory processes in identified neuronal networks, by showing that fear-memory induced reduction in AMPA/NMDA ratio at thalamic-ITC synapses is associated with a reduced postsynaptic AMPA receptor density

    Numerical test of the damping time of layer-by-layer growth on stochastic models

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    We perform Monte Carlo simulations on stochastic models such as the Wolf-Villain (WV) model and the Family model in a modified version to measure mean separation ℓ\ell between islands in submonolayer regime and damping time t~\tilde t of layer-by-layer growth oscillations on one dimension. The stochastic models are modified, allowing diffusion within interval rr upon deposited. It is found numerically that the mean separation and the damping time depend on the diffusion interval rr, leading to that the damping time is related to the mean separation as t~∼ℓ4/3{\tilde t} \sim \ell^{4/3} for the WV model and t~∼ℓ2{\tilde t} \sim \ell^2 for the Family model. The numerical results are in excellent agreement with recent theoretical predictions.Comment: 4 pages, source LaTeX file and 5 PS figure

    Rate theory for correlated processes: Double-jumps in adatom diffusion

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    We study the rate of activated motion over multiple barriers, in particular the correlated double-jump of an adatom diffusing on a missing-row reconstructed Platinum (110) surface. We develop a Transition Path Theory, showing that the activation energy is given by the minimum-energy trajectory which succeeds in the double-jump. We explicitly calculate this trajectory within an effective-medium molecular dynamics simulation. A cusp in the acceptance region leads to a sqrt{T} prefactor for the activated rate of double-jumps. Theory and numerical results agree

    Diazotroph Activity in Surface Narragansett Bay Sediments in Summer is Stimulated by Hypoxia and Organic Matter Delivery

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    Bacteria that carry out many processes of the nitrogen cycle inhabit estuarine sediments. Denitrification is known to be a dominant process causing estuarine sediments to behave as net nitrogen sinks. However, measurements of nitrogen fluxes in the sediments of Narragansett Bay, Rhode Island, USA, have at times revealed high rates of net nitrogen (N2) fixation. Whereas changes in primary production, in magnitude and phenology, within Narragansett Bay have been identified as possible causes for these changes in nitrogen cycling within the benthos, a factor that has not been examined thus far is seasonal hypoxia. Since anaerobic diazotrophs figure so prominently within the sediments of Narragansett Bay, we hypothesized that dissolved oxygen concentrations in the bottom waters affect their activity. In order to explore this relationship, we measured the activity of diazotrophs in the surface sediments of 3 study areas during the summers of 2013 and 2014 using the acetylene reduction assay. We explored the effects of several water quality parameters on nitrogenase activity including, among others, dissolved oxygen and chlorophyll concentrations. Our measurements of nitrogenase activity were generally low, ranging between 2 and 5 nmol ethylene g-1 d-1 but spiked to 16 nmol ethylene g-1 d-1 at an area experiencing severe hypoxia in July 2013. Our data suggest that diazotrophy in estuarine sediments is enhanced when the benthos experiences very low dissolved oxygen in conjunction with recent influxes of autochthonous organic matter. Experiments with sediment core incubations conducted in the laboratory support our hypothesis that low dissolved oxygen and organic matter additions promote N2 fixation

    Lattice Effects in Crystal Evaporation

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    We study the dynamics of a stepped crystal surface during evaporation, using the classical model of Burton, Cabrera and Frank, in which the dynamics of the surface is represented as a motion of parallel, monoatomic steps. The validity of the continuum approximation treated by Frank is checked against numerical calculations and simple, qualitative arguments. The continuum approximation is found to suffer from limitations related, in particular, to the existence of angular points. These limitations are often related to an adatom detachment rate of adatoms which is higher on the lower side of each step than on the upper side ("Schwoebel effect").Comment: DRFMC/SPSMS/MDN, Centre d'Etudes Nucleaires de Grenoble, 25 pages, LaTex, revtex style. 8 Figures, available upon request, report# UBFF30119

    Spiral surface growth without desorption

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    Spiral surface growth is well understood in the limit where the step motion is controlled by the local supersaturation of adatoms near the spiral ridge. In epitaxial thin-film growth, however, spirals can form in a step-flow regime where desorption of adatoms is negligible and the ridge dynamics is governed by the non-local diffusion field of adatoms on the whole surface. We investigate this limit numerically using a phase-field formulation of the Burton-Cabrera-Frank model, as well as analytically. Quantitative predictions, which differ strikingly from those of the local limit, are made for the selected step spacing as a function of the deposition flux, as well as for the dependence of the relaxation time to steady-state growth on the screw dislocation density.Comment: 9 pages, 3 figures, RevTe

    A tandem approach for collocated measurements of microphysical and radiative cirrus properties

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    Microphysical and radiation measurements were collected with the novel AIRcraft TOwed Sensor Shuttle (AIRTOSS) – Learjet tandem platform. The platform is a combination of an instrumented Learjet 35A research aircraft and an aerodynamic bird, which is detached from and retracted back to the aircraft during flight via a steel wire with a length of 4000 m. Both platforms are equipped with radiative, cloud microphysical, trace gas, and meteorological instruments. The purpose of the development of this tandem set-up is to study the inhomogeneity of cirrus as well as other stratiform clouds. Sophisticated numerical flow simulations were conducted in order to optimally integrate an axially asymmetric Cloud Combination Probe (CCP) inside AIRTOSS. The tandem platform was applied during measurements at altitudes up to 36 000 ft (10 970 m) in the framework of the AIRTOSS – Inhomogeneous Cirrus Experiment (AIRTOSS-ICE). Ten flights were performed above the North Sea and Baltic Sea to probe frontal and in situ formed cirrus, as well as anvil outflow cirrus. For one flight, cirrus microphysical and radiative properties displayed significant inhomogeneities resolved by both measurement platforms. The CCP data show that the maximum of the observed particle number size distributions shifts with decreasing altitude from 30 to 300 µm, which is typical for frontal, midlatitude cirrus. Theoretical considerations imply that cloud particle aggregation inside the studied cirrus is very unlikely. Consequently, diffusional growth was identified to be the dominant microphysical growth process. Measurements of solar downward and upward irradiances at 670 nm wavelength were conducted above, below, and in the cirrus on both the Learjet and AIRTOSS. The observed variability of the downward irradiance below the cirrus reflects the horizontal heterogeneity of the observed thin cirrus. Vertically resolved solar heating rates were derived by either using single-platform measurements at different altitudes or by making use of the collocated irradiance measurements at different altitudes of the tandem platform. Due to unavoidable biases of the measurements between the individual flight legs, the single-platform approach failed to provide a realistic solar heating rate profile, while the uncertainties of the tandem approach are reduced. Here, the solar heating rates range up to 6 K day−1 at top of the cirrus layer

    Subliminal and supraliminal processing of reward-related stimuli in anorexia nervosa

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    Background. Previous studies have highlighted the role of the brain reward and cognitive control systems in the etiology of anorexia nervosa (AN). In an attempt to disentangle the relative contribution of these systems to the disorder, we used functional magnetic resonance imaging (fMRI) to investigate hemodynamic responses to reward-related stimuli presented both subliminally and supraliminally in acutely underweight AN patients and age-matched healthy controls (HC). Methods. fMRI data were collected from a total of 35 AN patients and 35 HC, while they passively viewed subliminally and supraliminally presented streams of food, positive social, and neutral stimuli. Activation patterns of the group × stimulation condition × stimulus type interaction were interrogated to investigate potential group differences in processing different stimulus types under the two stimulation conditions. Moreover, changes in functional connectivity were investigated using generalized psychophysiological interaction analysis. Results. AN patients showed a generally increased response to supraliminally presented stimuli in the inferior frontal junction (IFJ), but no alterations within the reward system. Increased activation during supraliminal stimulation with food stimuli was observed in the AN group in visual regions including superior occipital gyrus and the fusiform gyrus/parahippocampal gyrus. No group difference was found with respect to the subliminal stimulation condition and functional connectivity. Conclusion. Increased IFJ activation in AN during supraliminal stimulation may indicate hyperactive cognitive control, which resonates with clinical presentation of excessive self-control in AN patients. Increased activation to food stimuli in visual regions may be interpreted in light of an attentional food bias in AN
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