324 research outputs found

    A Longitudinal Examination of the Hopelessness Theory of Depression in People Who Have Multiple Sclerosis.

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    PURPOSE: Hopelessness theory predicts that negative attributional style will interact with negative life events over time to predict depression. The intention of this study was to test this in a population who are at greater risk of negative life events, people with Multiple Sclerosis (MS). METHOD: Data, including measures of attributional style, negative life events, and depressive symptoms, were collected via postal survey in 3 phases, each one a year apart. RESULTS: Responses were received from over 380 participants at each study phase. Negative attributional style was consistently able to predict future depressive symptoms at low to moderate levels of association; however, this ability was not sustained when depressive symptoms at Phase 1 were controlled for. No substantial evidence to support the hypothesised interaction of negative attributional style and negative life events was found. CONCLUSIONS: Findings were not supportive of the causal interaction proposed by the hopelessness theory of depression. Further work considering other time frames, using methods to prime attributional style before assessment and specifically assessing the hopelessness subtype of depression, may prove to be more fruitful. Intervention directly to address attributional style should also be considered

    A Longitudinal Examination of the Hopelessness Theory of Depression in People Who Have Multiple Sclerosis.

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    PURPOSE: Hopelessness theory predicts that negative attributional style will interact with negative life events over time to predict depression. The intention of this study was to test this in a population who are at greater risk of negative life events, people with Multiple Sclerosis (MS). METHOD: Data, including measures of attributional style, negative life events, and depressive symptoms, were collected via postal survey in 3 phases, each one a year apart. RESULTS: Responses were received from over 380 participants at each study phase. Negative attributional style was consistently able to predict future depressive symptoms at low to moderate levels of association; however, this ability was not sustained when depressive symptoms at Phase 1 were controlled for. No substantial evidence to support the hypothesised interaction of negative attributional style and negative life events was found. CONCLUSIONS: Findings were not supportive of the causal interaction proposed by the hopelessness theory of depression. Further work considering other time frames, using methods to prime attributional style before assessment and specifically assessing the hopelessness subtype of depression, may prove to be more fruitful. Intervention directly to address attributional style should also be considered

    Study of wavelength-shifting chemicals for use in large-scale water Cherenkov detectors

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    Cherenkov detectors employ various methods to maximize light collection at the photomultiplier tubes (PMTs). These generally involve the use of highly reflective materials lining the interior of the detector, reflective materials around the PMTs, or wavelength-shifting sheets around the PMTs. Recently, the use of water-soluble wavelength-shifters has been explored to increase the measurable light yield of Cherenkov radiation in water. These wave-shifting chemicals are capable of absorbing light in the ultravoilet and re-emitting the light in a range detectable by PMTs. Using a 250 L water Cherenkov detector, we have characterized the increase in light yield from three compounds in water: 4-Methylumbelliferone, Carbostyril-124, and Amino-G Salt. We report the gain in PMT response at a concentration of 1 ppm as: 1.88 ±\pm 0.02 for 4-Methylumbelliferone, stable to within 0.5% over 50 days, 1.37 ±\pm 0.03 for Carbostyril-124, and 1.20 ±\pm 0.02 for Amino-G Salt. The response of 4-Methylumbelliferone was modeled, resulting in a simulated gain within 9% of the experimental gain at 1 ppm concentration. Finally, we report an increase in neutron detection performance of a large-scale (3.5 kL) gadolinium-doped water Cherenkov detector at a 4-Methylumbelliferone concentration of 1 ppm.Comment: 7 pages, 9 figures, Submitted to Nuclear Instruments and Methods

    The optical response of Ba_{1-x}K_xBiO_3: Evidence for an unusual coupling mechanism of superconductivity?

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    We have analysed optical reflectivity data for Ba_{1-x}K_xBiO_3 in the far-infrared region using Migdal-Eliashberg theory and found it inconsistent with standard electron-phonon coupling: Whereas the superconducting state data could be explained using moderate coupling, \lambda=0.7, the normal state properties indicate \lambda \le 0.2. We have found that such behaviour could be understood using a simple model consisting of weak standard electron-phonon coupling plus weak coupling to an unspecified high energy excitation near 0.4 eV. This model is found to be in general agreement with the reflectivity data, except for the predicted superconducting gap size. The additional high energy excitation suggests that the dominant coupling mechanism in Ba_{1-x}K_xBiO_3 is not standard electron-phonon.Comment: 5 pages REVTex, 5 figures, 32 refs, accepted for publication in Phys. Rev.

    Evidence that Differences in Fructosamine-3-Kinase Activity May be Associated with the Glycation Gap in Human Diabetes

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    The phenomenon of a discrepancy between glycated haemoglobin levels and other indicators of average glycaemia may be due to many factors but can be measured as the glycation gap (GGap). This GGap is associated with differences in complications in patients with diabetes and may possibly be explained by dissimilarities in deglycation in turn leading to altered production of Advanced Glycation End (AGE) products. We hypothesised that variations in the level of the deglycating enzyme Fructosamine-3-kinase (FN3K) might be associated with the GGap. We measured erythrocyte FN3K concentrations and enzyme activity in a population dichotomised for a large positive or negative GGap. FN3K protein was higher and we found a striking 3-fold greater activity (323%) at any given FN3K protein level in the erythrocytes of the negative compared with positive GGap groups. This was associated with lower AGE levels in the negative GGap group (79%), lower pro-inflammatory adipokines (Leptin/Adiponectin ratio) (73%) and much lower pro-thrombotic PAI-1 levels (19%). We conclude that FN3K may play a key role in the GGap and thus diabetes complications such that FN3K may be potential predictor of the risk of diabetes complications. Pharmacological modifications of its activity may provide a novel approach to their prevention

    Search for Matter-Dependent Atmospheric Neutrino Oscillations in Super-Kamiokande

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    We consider muon neutrino to tau neutrino oscillations in the context of the Mass Varying Neutrino (MaVaN) model, where the neutrino mass can vary depending on the electron density along the flight path of the neutrino. Our analysis assumes a mechanism with dependence only upon the electron density, hence ordinary matter density, of the medium through which the neutrino travels. Fully-contained, partially-contained and upward-going muon atmospheric neutrino data from the Super--Kamiokande detector, taken from the entire SK--I period of 1489 live days, are compared to MaVaN model predictions. We find that, for the case of 2-flavor oscillations, and for the specific models tested, oscillation independent of electron density is favored over density dependence. Assuming maximal mixing, the best-fit case and the density-independent case do not differ significantly.Comment: 6 pages, 1 figur

    Far-infrared transmission studies of c-axis oriented superconducting MgB2 thin film

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    We reported far-infrared transmission measurements on a c-axis oriented superconducting MgB2_{2} thin film in the frequency range of 30 \sim 250 cm1^{-1}. We found that these measurements were sensitive to values of scattering rate 1/τ1/\tau and superconducting gap 2Δ2\Delta. By fitting the experimental transmission spectra at 40 K and below, we obtained 1/τ=1/\tau = (700 \sim 1000) cm1^{-1} and 2Δ(0)2\Delta (0)\cong 42 cm1^{-1}. These two quantities suggested that MgB2_{2} belong to the dirty limit.Comment: submitted at May

    Technical note: Use of an atmospheric simulation chamber to investigate the effect of different engine conditions on unregulated VOC-IVOC diesel exhaust emissions

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    Diesel exhaust emissions were introduced into an atmospheric simulation chamber and measured using thermal desorption (TD) comprehensive two-dimensional gas chromatography coupled to a flame ionisation detector (GC × GC-FID). An extensive set of measurements were performed to investigate the effect of different engine conditions (i.e. load, speed, driving scenarios) and emission control devices (with or without diesel oxidative catalyst, DOC) on the composition and abundance of unregulated exhaust gas emissions from a light-duty diesel engine, fuelled with ultra-low sulfur diesel (ULSD). A range of exhaust dilution ratios were investigated (range = 1:60 to 1:1158), simulating the chemical and physical transformations of the exhaust gas from near to downwind of an emission source. In total, 16 individual and 8 groups of compounds (aliphatics and single-ring aromatics) were measured in the exhaust gas ranging from volatile to intermediate volatility (VOC-IVOC), providing both detailed chemical speciation and groupings of compounds based on their structure and functionality. Measured VOC-IVOC emission rates displayed excellent reproducibility from replicate experiments using similar exhaust dilution ratios. However, at the extremes of the investigated exhaust dilution ratios (comparison of 1:60 and 1:1158), measured VOC-IVOC emission rates displayed some disagreement owing to poor reproducibility and highlighted the importance of replicate sample measurements. The investigated DOC was found to remove 43±10% (arithmetic mean±experimental uncertainty) of the total speciated VOC-IVOC ( ∑ SpVOC-IVOC) emissions. The compound class-dependant removal efficiencies for the investigated DOC were 39±12% and 83±3% for the aliphatics and single-ring aromatics, respectively. The DOC aliphatic removal efficiency generally decreased with increasing carbon chain length. The  ∑ SpVOC-IVOC emission rates varied significantly with different engine conditions, ranging from 70 to 9268mgkg−1 (milligrams of mass emitted per kilogram of fuel burnt).  ∑ SpVOC-IVOC emission rates generally decreased with increasing engine load and temperature, and to a lesser degree, engine speed. The exhaust gas composition changed considerably as a result of two influencing factors: engine combustion and DOC hydrocarbon (HC) removal efficiency. Increased engine combustion efficiency resulted in a greater percentage contribution of the C7 to C12 n-alkanes to the  ∑ SpVOC-IVOC emission rate. Conversely, increased DOC HC removal efficiency resulted in a greater percentage contribution of the C7 to C12 branched aliphatics to the  ∑ SpVOC-IVOC emission rate. At low engine temperatures ( < 150°C, below the working temperature of the DOC), the contribution of n-alkanes in the exhaust gas increased with increasing combustion efficiency and may be important in urban environments, as n-alkanes are more efficient at producing secondary organic aerosol (SOA) than their branched counterparts. At very high engine temperatures (maximum applied engine speed and load, engine temperature = 700°C), the n-alkane contribution increased by a factor of 1.6 times greater than that observed in the cold-start experiment (most similar to unburnt fuel) and may suggest liquid-fuel-based estimates of SOA yields may be inconsistent with exhaust SOA yields, particularly at high engine speeds and loads (i.e. high engine temperatures). Emission rates were found to be 65 times greater from a cold-start experiment than at maximum applied engine speed and load. To our knowledge, this is the first study which uses an atmospheric simulation chamber to separate the effects of the DOC and combustion efficiency on the exhaust gas composition

    Solar neutrino measurements in Super-Kamiokande-II

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    The results of the second phase of the Super-Kamiokande solar neutrino measurement are presented and compared to the first phase. The solar neutrino flux spectrum and time-variation as well as oscillation results are statistically consistent with the first phase and do not show spectral distortion. The time-dependent flux measurement of the combined first and second phases coincides with the full period of solar cycle 23 and shows no correlation with solar activity. The measured boron 8 total flux is 2.38 +/-0.05(stat.) +0.16-0.15(sys.) X 10^6 cm^-2 sec^-1 and the day-night difference is found to be -6.3 +/-4.2(stat.) +/-3.7(sys.) %. There is no evidence of systematic tendencies between the first and second phases
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