279 research outputs found
Ionic and electronic properties of the topological insulator BiTeSe investigated using -detected nuclear magnetic relaxation and resonance of Li
We report measurements on the high temperature ionic and low temperature
electronic properties of the 3D topological insulator BiTeSe using
ion-implanted Li -detected nuclear magnetic relaxation and
resonance. With implantation energies in the range 5-28 keV, the probes
penetrate beyond the expected range of the topological surface state, but are
still within 250 nm of the surface. At temperatures above ~150 K, spin-lattice
relaxation measurements reveal isolated Li diffusion with an
activation energy eV and attempt frequency s for atomic site-to-site hopping. At lower
temperature, we find a linear Korringa-like relaxation mechanism with a field
dependent slope and intercept, which is accompanied by an anomalous field
dependence to the resonance shift. We suggest that these may be related to a
strong contribution from orbital currents or the magnetic freezeout of charge
carriers in this heavily compensated semiconductor, but that conventional
theories are unable to account for the extent of the field dependence.
Conventional NMR of the stable host nuclei may help elucidate their origin.Comment: 17 pages, 12 figures, submitted to Phys. Rev.
War and Money in Ngram Viewer
The second and fourth authors have been inviting Intro to Applied Analytics and Statistics 1 students to use the Ngram Database to explore historical topics of their choosing. This is the first article derived from this exercise. The first author examined the historical relationship between war and money from 1775 to 2005 in the American English corpus. This is followed by an examination of the 3-gram “cost of war” in the American English and British English corpora. Specific to the analyses presented here several military and economic events are discussed. More specifically, both economies and wars are somewhat unpredictable, with wars being more so. Through this exercise, more experience with statistics and a greater appreciation of history are achieved
Depth-resolved measurement of the Meissner screening profile in a niobium thin film from spin-lattice relaxation of the implanted -emitter Li
We report measurements of the Meissner screening profile in a Nb(300
nm)/AlO thin film using Li -detected nuclear magnetic
resonance (-NMR). The NMR probe Li was ion-implanted into the Nb
film at energies 20 keV, corresponding to mean stopping depths
comparable to Nb's magnetic penetration depth . Li's strong
dipole-dipole coupling with the host Nb nuclei provided a
"cross-relaxation" channel that dominated in low magnetic fields, which
conferred indirect sensitivity to the local magnetic field via the spin-lattice
relaxation (SLR) rate . From a fit of the data to a model
accounting for its dependence on temperature, magnetic field, and
Li implantation energy, we obtained a magnetic penetration depth
= 51.5(22) nm, consistent with a relatively short carrier
mean-free-path = 18.7(29) nm typical of similarly prepared Nb films. The
results presented here constitute an important step towards using Li
-NMR to characterize bulk Nb samples with engineered surfaces, which are
often used in the fabrication of particle accelerators.Comment: 16 pages, 4 figure
Magnesium(II)‐ATP Complexes in 1‐Ethyl‐3‐Methylimidazolium Acetate Solutions Characterized by 31Mg β‐Radiation‐Detected NMR Spectroscopy
Mendelian randomization study of B-type natriuretic peptide and type 2 diabetes: evidence of causal association from population studies
<p>Background: Genetic and epidemiological evidence suggests an inverse association between B-type natriuretic peptide (BNP) levels in blood and risk of type 2 diabetes (T2D), but the prospective association of BNP with T2D is uncertain, and it is unclear whether the association is confounded.</p>
<p>Methods and Findings: We analysed the association between levels of the N-terminal fragment of pro-BNP (NT-pro-BNP) in blood and risk of incident T2D in a prospective case-cohort study and genotyped the variant rs198389 within the BNP locus in three T2D case-control studies. We combined our results with existing data in a meta-analysis of 11 case-control studies. Using a Mendelian randomization approach, we compared the observed association between rs198389 and T2D to that expected from the NT-pro-BNP level to T2D association and the NT-pro-BNP difference per C allele of rs198389. In participants of our case-cohort study who were free of T2D and cardiovascular disease at baseline, we observed a 21% (95% CI 3%-36%) decreased risk of incident T2D per one standard deviation (SD) higher log-transformed NT-pro-BNP levels in analysis adjusted for age, sex, body mass index, systolic blood pressure, smoking, family history of T2D, history of hypertension, and levels of triglycerides, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol. The association between rs198389 and T2D observed in case-control studies (odds ratio = 0.94 per C allele, 95% CI 0.91-0.97) was similar to that expected (0.96, 0.93-0.98) based on the pooled estimate for the log-NT-pro-BNP level to T2D association derived from a meta-analysis of our study and published data (hazard ratio = 0.82 per SD, 0.74-0.90) and the difference in NT-pro-BNP levels (0.22 SD, 0.15-0.29) per C allele of rs198389. No significant associations were observed between the rs198389 genotype and potential confounders.</p>
<p>Conclusions: Our results provide evidence for a potential causal role of the BNP system in the aetiology of T2D. Further studies are needed to investigate the mechanisms underlying this association and possibilities for preventive interventions.</p>
Global Solar Magnetic Field Evolution Over 4 Solar Cycles: Use of the McIntosh Archive
The McIntosh Archive consists of a set of hand-drawn solar Carrington maps created by Patrick McIntosh from 1964 to 2009. McIntosh used mainly Hα, He-I 10830 Å and photospheric magnetic measurements from both ground-based and NASA satellite observations. With these he traced polarity inversion lines (PILs), filaments, sunspots and plage and, later, coronal holes over a ~45-year period. This yielded a unique record of synoptic maps of features associated with the large-scale solar magnetic field over four complete solar cycles. We first discuss how these and similar maps have been used in the past to investigate long-term solar variability. Then we describe our work in preserving and digitizing this archive, developing a digital, searchable format, and creating a website and an archival repository at NOAA's National Centers for Environmental Information (NCEI). Next we show examples of how the data base can be utilized for scientific applications. Finally, we present some preliminary results on the solar-cycle evolution of the solar magnetic field, including the polar field reversal process, the evolution of active longitudes, and the role of differential solar rotation
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