Broadband, unpolarized repumping and clearout light sources for Sr+^+ single-ion clocks

Future transportable optical clocks require compact and reliable light sources. Here, broadband, unpolarized repumper and state clearout sources for Sr+ single-ion optical clocks are reported. These turn-key devices require no frequency stabilization nor external modulators. They are fiber based, inexpensive, and compact. Key characteristics for clock operation are presented, including optical spectra, induced light shifts and required extinction ratios. Tests with an operating single-ion standard show a clearout efficiency of 100%. Compared to a laser-based repumper, the achievable fluorescence rates for ion detection are a few tens of per cent lower. The resulting ion kinetic temperature is 1--1.5 mK, near the Doppler limit of the ion system. Similar repumper light sources could be made for Ca+ (866 nm) and Ba+ (650 nm) using semiconductor gain media.Comment: 4 pages, 6 figure

Letter from E. A. Wallin

Letter concerning a copy of the catalogue for Utah Agricultural College

Following one's heart: cardiac rhythms gate central initiation of sympathetic reflexes

Central nervous processing of environmental stimuli requires integration of sensory information with ongoing autonomic control of cardiovascular function. Rhythmic feedback of cardiac and baroreceptor activity contributes dynamically to homeostatic autonomic control. We examined how the processing of brief somatosensory stimuli is altered across the cardiac cycle to evoke differential changes in bodily state. Using functional magnetic resonance imaging of brain and noninvasive beat-to-beat cardiovascular monitoring, we show that stimuli presented before and during early cardiac systole elicited differential changes in neural activity within amygdala, anterior insula and pons, and engendered different effects on blood pressure. Stimulation delivered during early systole inhibited blood pressure increases. Individual differences in heart rate variability predicted magnitude of differential cardiac timing responses within periaqueductal gray, amygdala and insula. Our findings highlight integration of somatosensory and phasic baroreceptor information at cortical, limbic and brainstem levels, with relevance to mechanisms underlying pain control, hypertension and anxiety

The Effect of Columnar Disorder on the Superconducting Transition of a Type-II Superconductor in Zero Applied Magnetic Field

We investigate the effect of random columnar disorder on the superconducting phase transition of a type-II superconductor in zero applied magnetic field using numerical simulations of three dimensional XY and vortex loop models. We consider both an unscreened model, in which the bare magnetic penetration length is approximated as infinite, and a strongly screened model, in which the magnetic penetration length is of order the vortex core radius. We consider both equilibrium and dynamic critical exponents. We show that, as in the disorder free case, the equilibrium transitions of the unscreened and strongly screened models lie in the same universality class, however scaling is now anisotropic. We find for the correlation length exponent $\nu=1.2\pm 0.1$, and for the anisotropy exponent $\zeta=1.3\pm 0.1$. We find different dynamic critical exponents for the unscreened and strongly screened models.Comment: 30 pages 12 ps figure

Theory of Magneto-resistance of Disordered Superconducting Films

Recent experimental studies of magneto-resistance in disordered superconducting thin films reveal a huge peak (about 5 orders of magnitude). While it may be expected that magnetic field destroys superconductivity, leading to an enhanced resistance, attenuation of the resistance at higher magnetic fields is surprising. We propose a model which accounts for the experimental results in the entire range of magnetic fields, based on the formation of superconducting islands due to fluctuations in the superconducting order parameter amplitude. At strong magnetic fields Coulomb blockade in these islands gives rise to negative magneto-resistance. As the magnetic field is reduced the effect of Coulomb blockade diminishes and eventually the magneto-resistance changes sign. Numerical calculations show good qualitative agreement with experimental data.Comment: 4 pages, 4 figure

Fish consumption in relation to myocardial infarction, stroke and mortality among women and men with type 2 diabetes: A prospective cohort study

\textit{Background & aims:} The accumulated evidence supports an inverse association of fish consumption with cardiovascular disease and mortality, but data among patients with type 2 diabetes are sparse. We aimed to assess fish consumption in relation to myocardial infarction (MI), stroke and mortality among individuals with type 2 diabetes. $\textit{Methods:}$ Women and men with diagnosed type 2 diabetes (n = 2225; aged 45-84 years) within two population-based cohorts (the Swedish Mammography Cohort and the Cohort of Swedish Men) were followed from 1998 through 2012. Cox proportional hazards models were used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs). $\textit{Results:}$ We identified 333 incident MI events, 321 incident stroke events and 771 deaths (154 with coronary heart disease [CHD] as underlying cause) during follow-up of up to 15 years. The multivariable HRs comparing >3 servings/week with $\leq$3 servings/month were 0.60 (95% CI, 0.39-0.92) for MI and 1.04 (95% CI, 0.66-1.64) for stroke. HRs for total mortality were lowest for moderate fish consumption of 1-<2 servings/week (0.82; 95% CI, 0.64-1.04) and 2-3 servings/week (0.79; 95% CI, 0.61-1.01) compared with $\leq$3 servings/month. The corresponding HRs for CHD-related mortality were 0.53; 95% CI, 0.32-0.90 and 0.75; 95% CI, 0.45-1.27. $\textit{Conclusions:}$ Fish consumption was associated with lower MI incidence among individuals with type 2 diabetes, whereas no association was observed with stroke. Our data further indicated an association with lower mortality, particularly for CHD-related deaths. These findings support the current general advice on regular fish consumption also in the high risk group of type 2 diabetes patients.This work was supported by research grants from the Swedish Research Council/Committee for Research Infrastructure, from the Karolinska Institutet's Award for PhD students (KID-funding). NGF is supported by MRC support from MC_UU_12015/5

Localized Flux Lines and the Bose Glass

Columnar defects provide effective pinning centers for magnetic flux lines in high--$T_{\rm c}$ superconductors. Utilizing a mapping of the statistical mechanics of directed lines to the quantum mechanics of two--dimensional bosons, one expects an entangled flux liquid phase at high temperatures, separated by a second--order localization transition from a low--temperature ``Bose glass'' phase with infinite tilt modulus. Recent decoration experiments have demonstrated that below the matching field the repulsive forces between the vortices may be sufficiently large to produce strong spatial correlations in the Bose glass. This is confirmed by numerical simulations, and a remarkably wide soft ``Coulomb gap'' at the chemical potential is found in the distribution of pinning energies. At low currents, the dominant transport mechanism in the Bose glass phase proceeds via the formation of double kinks between not necessarily adjacent columnar pins, similar to variable--range hopping in disordered semiconductors. The strong correlation effects originating in the long--range vortex interactions drastically reduce variable--range hopping transport.Comment: 10 pages, latex ("lamuphys.sty" file included), 6 figures can be obtained from the author ([email protected]); to appear in Proc. XIV Sitges conference on "Complex Behaviour of Glassy Systems" (Springer--Verlag