Doping Effects on the Performance of Paired Metal Catalysts for the Hydrogen Evolution Reaction

Metal heteroatoms dispersed in nitrogen-doped graphene display promising catalytic activity for fuel cell reactions such as the hydrogen evolution reaction (HER). Here we explore the effects of dopant concentration on the synergistic catalytic behaviour of a paired metal atom active site comprised of Co and Pt atoms. The metals are coordinated to six atoms in a vacancy of N-doped graphene. We find that HER activity is enhanced with increasing N concentration, where the free energy of hydrogen atom adsorption ranges from 0.23 to -0.42 eV as the doping changes from a single N atom doped in the pore, to fully doped coordination sites. The results indicated that the effect of N is to make the Co atom more active towards H adsorption and presents a means through which transition metals can be modified to make more effective and sustainable fuel cell catalysts

Immunosuppressants and risk of Parkinson disease

We performed a population-based case-control study of United States Medicare beneficiaries age 60-90 in 2009 with prescription data (48,295 incident Parkinson disease cases and 52,324 controls) to examine the risk of Parkinson disease in relation to use of immunosuppressants. Inosine monophosphate dehydrogenase inhibitors (relative risk = 0.64; 95% confidence interval 0.51-0.79) and corticosteroids (relative risk = 0.80; 95% confidence interval 0.77-0.83) were both associated with a lower risk of Parkinson disease. Inverse associations for both remained after applying a 12-month exposure lag. Overall, this study provides evidence that use of corticosteroids and inosine monophosphate dehydrogenase inhibitors might lower the risk of Parkinson disease

The Steady State Fluctuation Relation for the Dissipation Function

We give a proof of transient fluctuation relations for the entropy production (dissipation function) in nonequilibrium systems, which is valid for most time reversible dynamics. We then consider the conditions under which a transient fluctuation relation yields a steady state fluctuation relation for driven nonequilibrium systems whose transients relax, producing a unique nonequilibrium steady state. Although the necessary and sufficient conditions for the production of a unique nonequilibrium steady state are unknown, if such a steady state exists, the generation of the steady state fluctuation relation from the transient relation is shown to be very general. It is essentially a consequence of time reversibility and of a form of decay of correlations in the dissipation, which is needed also for, e.g., the existence of transport coefficients. Because of this generality the resulting steady state fluctuation relation has the same degree of robustness as do equilibrium thermodynamic equalities. The steady state fluctuation relation for the dissipation stands in contrast with the one for the phase space compression factor, whose convergence is problematic, for systems close to equilibrium. We examine some model dynamics that have been considered previously, and show how they are described in the context of this work.Comment: 30 pages, 1 figur

Large Magnetic Susceptibility Anisotropy of Metallic Carbon Nanotubes

Through magnetic linear dichroism spectroscopy, the magnetic susceptibility anisotropy of metallic single-walled carbon nanotubes has been extracted and found to be 2-4 times greater than values for semiconducting single-walled carbon nanotubes. This large anisotropy is consistent with our calculations and can be understood in terms of large orbital paramagnetism of electrons in metallic nanotubes arising from the Aharonov-Bohm-phase-induced gap opening in a parallel field. We also compare our values with previous work for semiconducting nanotubes, which confirm a break from the prediction that the magnetic susceptibility anisotropy increases linearly with the diameter.Comment: 4 pages, 4 figure

Validation of a Parkinson disease predictive model in a population-based study

Parkinson disease (PD) has a relatively long prodromal period that may permit early identification to reduce diagnostic testing for other conditions when patients are simply presenting with early PD symptoms, as well as to reduce morbidity from fall-related trauma. Earlier identification also could prove critical to the development of neuroprotective therapies. We previously developed a PD predictive model using demographic and Medicare claims data in a population-based case-control study. The area under the receiver-operating characteristic curve (AUC) indicated good performance. We sought to further validate this PD predictive model. In a randomly selected, population-based cohort of 115,492 Medicare beneficiaries aged 66–90 and without PD in 2009, we applied the predictive model to claims data from the prior five years to estimate the probability of future PD diagnosis. During five years of follow-up, we used 2010–2014 Medicare data to determine PD and vital status and then Cox regression to investigate whether PD probability at baseline was associated with time to PD diagnosis. Within a nested case-control sample, we calculated the AUC, sensitivity, and specificity. A total of 2,326 beneficiaries developed PD. Probability of PD was associated with time to PD diagnosis (p<0.001, hazard ratio = 13.5, 95% confidence interval (CI) 10.6–17.3 for the highest vs. lowest decile of probability). The AUC was 83.3% (95% CI 82.5%–84.1%). At the cut point that balanced sensitivity and specificity, sensitivity was 76.7% and specificity was 76.2%. In an independent sample of additional Medicare beneficiaries, we again applied the model and observed good performance (AUC = 82.2%, 95% CI 81.1%–83.3%). Administrative claims data can facilitate PD identification within Medicare and Medicare-aged samples

The Ursinus Weekly, September 26, 1974

Fall Forum season opens • Editorial: Dear freshmen • A Guide to better living in Collegeville, Pa. 19426 • Bears 1974 football preview • Harriers upset by Delaware Valleyhttps://digitalcommons.ursinus.edu/weekly/1019/thumbnail.jp

Optical Spectroscopy of Single-Walled Carbon Nanotubes Under Extreme Conditions

Single-walled carbon nanotubes (SWNTs) are one of the leading candidate materials to realize novel nanoscale photonic devices. In order to assess their performance characteristics as optoelectronic materials, it is crucial to examine their optical properties in highly non-equilibrium situations such as high magnetic fields, low temperatures, and under high photoexcitation. Therefore, we present our latest result on the magnetic susceptibility anisotropy of metallic carbon nanotubes due to the Aharonov-Bohm effect. Here, we performed magnetic linear dichroism on a metallic-enriched HiPco SWNT sample utilizing a 35 T Hybrid Magnet to measure absorption with light polarization both perpendicular and parallel to the magnetic field. By relating these values with the nematic order parameter for alignment, we found that the metallic carbon nanotubes do not follow a strict diameter dependence across the 7 chiralities present in our sample. In addition to the studying the absorption properties exhibited at high magnetic field, we performed temperature-dependent (300 K to 11 K) photoluminescence (PL) on HiPco SWNTs embedded in an ι -carrageenan matrix utilizing intense fs pulses from a wavelength-tunable optical parametric amplifier. We found that for each temperature the PL intensity saturates as a function of pump fluence and the saturation intensity increases from 300 K to a moderate temperature around 100-150 K. Within the framework of diffusion-limited exciton-exciton annihilation (EEA), we successfully estimated the density of 1D excitons in SWNTs as a function of temperature and chirality. These results coupled with our results of magnetic brightening, or an increase in PL intensity as a function of magnetic flux through each SWNT due to the Aharonov-Bohm effect, yield great promise that in the presence of a high magnetic field the density of excitons can be further increased

Magneto-optical spectroscopy of metallic carbon nanotubes

Through polarization-dependent magneto-optical absorption spectroscopy, the magnetic susceptibility anisotropy for metallic single-walled carbon nanotubes has been extracted and found to be up to 4x greater than values for semiconducting single-walled carbon nanotubes. Consistent with theoretical predictions, this is the first experimental evidence of the paramagnetic nature arising from the Aharonov-Bohm-phase-induced gap opening in metallic nanotubes. We also compare our values with previous work for semiconducting nanotubes, which confirm a break from the prediction that the magnetic susceptibility anisotropy increases linearly with the diameter