522 research outputs found

    Early Canadian Icebreakers

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    Reminisces on icebreaking vessels used in charting the Hudson Bay route prior to World War I. Several were sold to the Russians for war service in arctic waters, and one, the Earl Grey, subsequently became well known as the Fedor Litke

    A5_3 Sliding in Space

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    This paper is based on a thought experiment in which the scenario 'How long would it take a person to go down a slide from the Moon to Earth?' is addressed. After making various assumptions to simplify this experiment, the time taken was calculated to be 74 hours

    A5_1 Super Sonic (the Hedgehog)

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    In the popular game franchise Sonic The Hedgehog Sonic has several powers. For example he can move at the speed of sound, and is able to transform into Super Sonic- a gold version of himself who can move close to the speed of light[1]. In this paper we use the equations of relativity to theorise what would happen if Super Sonic was running towards, and then past a stationary observer. We take into account length contraction and time dilation as well as the velocity Sonic would have to travel at to achieve his golden colour

    Suboptimal blood pressure control in chronic kidney disease stage 3: baseline data from a cohort study in primary care

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    Background: poorly controlled hypertension is independently associated with mortality, cardiovascular risk and disease progression in chronic kidney disease (CKD). In the UK, CKD stage 3 is principally managed in primary care, including blood pressure (BP) management. Controlling BP is key to improving outcomes in CKD. This study aimed to investigate associations of BP control in people with CKD stage 3.Methods: 1,741 patients with CKD 3 recruited from 32 general practices for the Renal Risk in Derby Study underwent medical history, clinical assessment and biochemistry testing. BP control was assessed by three standards: National Institute for Health and Clinical Excellence (NICE), National Kidney Foundation Kidney Disease Outcome Quality Initiative (KDOQI) and Kidney Disease: Improving Global Outcomes (KDIGO) guidelines. Descriptive statistics were used to compare characteristics of people achieving and not achieving BP control. Univariate and multivariate logistic regression was used to identify factors associated with BP control.Results: the prevalence of hypertension was 88%. Among people with hypertension, 829/1426 (58.1%) achieved NICE BP targets, 512/1426 (35.9%) KDOQI targets and 859/1426 (60.2%) KDIGO targets. Smaller proportions of people with diabetes and/or albuminuria achieved hypertension targets. 615/1426 (43.1%) were only taking one antihypertensive agent. On multivariable analysis, BP control (NICE and KDIGO) was negatively associated with age (NICE odds ratio (OR) 0.27; 95% confidence interval (95% CI) 0.17-0.43) 70–79 compared to &lt;60), diabetes (OR 0.32; 95% CI 0.25-0.43)), and albuminuria (OR 0.56; 95% CI 0.42-0.74)). For the KDOQI target, there was also association with males (OR 0.76; 95% CI 0.60-0.96)) but not diabetes (target not diabetes specific). Older people were less likely to achieve systolic targets (NICE target OR 0.17 (95% CI 0.09,0.32) p?&lt;?0.001) and more likely to achieve diastolic targets (OR 2.35 (95% CI 1.11,4.96) p?&lt;?0.001) for people &gt;80 compared to?&lt;?60).Conclusions: suboptimal BP control was common in CKD patients with hypertension in this study, particularly those at highest risk of adverse outcomes due to diabetes and or albuminuria. This study suggests there is scope for improving BP control in people with CKD by using more antihypertensive agents in combination while considering issues of adherence and potential side effects.<br/

    Effect of tensor couplings in a relativistic Hartree approach for finite nuclei

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    The relativistic Hartree approach describing the bound states of both nucleons and anti-nucleons in finite nuclei has been extended to include tensor couplings for the ω\omega- and ρ\rho-meson. After readjusting the parameters of the model to the properties of spherical nuclei, the effect of tensor-coupling terms rises the spin-orbit force by a factor of 2, while a large effective nucleon mass m/MN0.8m^{*}/M_{N} \approx 0.8 sustains. The overall nucleon spectra of shell-model states are improved evidently. The predicted anti-nucleon spectra in the vacuum are deepened about 20 -- 30 MeV.Comment: 31 pages, 4 postscript figures include

    Noncommutative massive Thirring model in three-dimensional spacetime

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    We evaluate the noncommutative Chern-Simons action induced by fermions interacting with an Abelian gauge field in a noncommutative massive Thirring model in (2+1)-dimensional spacetime. This calculation is performed in the Dirac and Majorana representations. We observe that in Majorana representation when θ\theta goes to zero we do not have induced Chern-Simons term in the dimensional regularization scheme.Comment: Accepted to Phys. Rev. D; 9 pages, Revtex4, no figures, references added, minor improvements, Eq.31 correcte

    Self-Averaging, Distribution of Pseudo-Critical Temperatures and Finite Size Scaling in Critical Disordered Systems

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    The distributions P(X)P(X) of singular thermodynamic quantities in an ensemble of quenched random samples of linear size ll at the critical point TcT_c are studied by Monte Carlo in two models. Our results confirm predictions of Aharony and Harris based on Renormalization group considerations. For an Ashkin-Teller model with strong but irrelevant bond randomness we find that the relative squared width, RXR_X, of P(X)P(X) is weakly self averaging. RXlα/νR_X\sim l^{\alpha/\nu}, where α\alpha is the specific heat exponent and ν\nu is the correlation length exponent of the pure model fixed point governing the transition. For the site dilute Ising model on a cubic lattice, known to be governed by a random fixed point, we find that RXR_X tends to a universal constant independent of the amount of dilution (no self averaging). However this constant is different for canonical and grand canonical disorder. We study the distribution of the pseudo-critical temperatures Tc(i,l)T_c(i,l) of the ensemble defined as the temperatures of the maximum susceptibility of each sample. We find that its variance scales as (δTc(l))2l2/ν(\delta T_c(l))^2 \sim l^{-2/\nu} and NOT as ld.Wefindthat\sim l^{-d}. We find that R_\chiisreducedbyafactorof is reduced by a factor of \sim 70withrespectto with respect to R_\chi (T_c)bymeasuring by measuring \chiofeachsampleat of each sample at T_c(i,l).Weanalyzecorrelationsbetweenthemagnetizationatcriticality. We analyze correlations between the magnetization at criticality m_i(T_c,l)andthepseudocriticaltemperature and the pseudo-critical temperature T_c(i,l)intermsofasampleindependentfinitesizescalingfunctionofasampledependentreducedtemperature in terms of a sample independent finite size scaling function of a sample dependent reduced temperature (T-T_c(i,l))/T_c$. This function is found to be universal and to behave similarly to pure systems.Comment: 31 pages, 17 figures, submitted to Phys. Rev.

    Nonequilibrium relaxation in neutral BCS superconductors: Ginzburg-Landau approach with Landau damping in real time

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    We present a field-theoretical method to obtain consistently the equations of motion for small amplitude fluctuations of the order parameter directly in real time for a homogeneous, neutral BCS superconductor. This method allows to study the nonequilibrium relaxation of the order parameter as an initial value problem. We obtain the Ward identities and the effective actions for small phase the amplitude fluctuations to one-loop order. Focusing on the long-wavelength, low-frequency limit near the critical point, we obtain the time-dependent Ginzburg-Landau effective action to one-loop order, which is nonlocal as a consequence of Landau damping. The nonequilibrium relaxation of the phase and amplitude fluctuations is studied directly in real time. The long-wavelength phase fluctuation (Bogoliubov-Anderson-Goldstone mode) is overdamped by Landau damping and the relaxation time scale diverges at the critical point, revealing critical slowing down.Comment: 31 pages 14 figs, revised version, to appear in Phys. Rev.
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