Rotational Excitation of HD by Hydrogen Revisited.

The HD molecules are key species for the cooling of pristine gas at temperatures below 100 K. They are also known to be key tracers of H2 in protoplanetary disks and thus, they can be used as a measure of protoplanetary disks mass. Accurate modeling of the cooling mechanism and of HD abundance in astrophysical media requires a proper modeling for its excitation by both radiative and collisional processes. Here, we report quantum time-independent calculations of collisional rate coefficients for the rotational excitation of HD by H for temperatures ranging from 10 to 1000 K. The reactive and hydrogen exchange channels are taken into account in the scattering calculations. New exact quantum results are compared to previous calculations performed neglecting reactive and exchange channels. We found that for temperatures higher than ∼300 K, the impact of these channels on the rate coefficients cannot be neglected. Such results suggest that the new HD-H collisional data have to be used for properly modeling HD cooling function and HD abundance in all the astrophysical environments where HD plays a role, e.g. in photon-dominated regions, protoplanetary disks, early Universe chemistry, and primordial star forming regions.

Sarcopenia in Elderly Diabetic Patients: Role of Dipeptidyl Peptidase 4 Inhibitors.

BACKGROUND: Our study aimed to investigate the effect of dipeptidyl peptidase 4 inhibitors (DPP4-I) on sarcopenic parameters in elderly type 2 diabetic patients. DESIGN: All elderly diabetic patients were invited to present themselves at our outpatient Geriatric Centre to undergo to evaluation of glycemic, inflammatory, and sarcopenic parameters and to perform a meal test for glucagon-like peptide-1 analogue (GLP-1) activity evaluation. SETTING: According to European Working Group on Sarcopenia in Older People (EWGSOP) criteria, sarcopenic parameters were assessed by bioelectrical impedance analysis (BIA) and Kern dynamometer and 4-m gait speed tests. All patients received standardized meals for the assessment of postprandial levels of GLP-1 activity. PARTICIPANTS, MEASUREMENTS: Data of 80 elderly diabetic patients treated with oral glucose-lowering drugs (DPP4-I or Sulfonylureas Group) for at least 24 months before enrollment were analyzed. RESULTS: The DPP4-I Group showed appropriate glycemic control, lower levels of inflammatory parameters, a significant and greater increase, during interprandial periods, of GLP-1 activity, and better sarcopenic parameters (fat-free mass, skeletal muscle mass, and related indices, muscle strength, and gait speed) compared with the Sulfonylureas Group. Univariate analysis showed that sarcopenic parameters correlated with glycemic control and with GLP-1 area under the curve values. Multivariate analysis confirms these relationships. CONCLUSION: The results are consistent with the hypothesis that DPP4-I use might have a positive effect on the loss of muscle mass and its function.

Complementarity between Quantum and Classical Mechanics in Chemical Modeling. The H + HeH+ → H2 + + He Reaction: A Rigourous Test for Reaction Dynamics Methods.

In this work we present a dynamical study of the H + HeH+ → H2+ + He reaction in a collision energy range from 0.1 meV to 10 eV, suitable to be used in applicative models. The paper extends and complements a recent work [ Phys. Chem. Chem. Phys. 2014, 16, 11662] devoted to the characterization of the reactivity from the ultracold regime up to the three-body dissociation breakup. In particular, the accuracy of the quasi-classical trajectory method below the three-body dissociation threshold has been assessed by a detailed comparison with previous calculations performed with different reaction dynamics methods, whereas the reliability of the results in the high energy range has been checked by a direct comparison with the available experimental data. Integral cross sections for several HeH+ roto-vibrational states have been analyzed and used to understand the extent of quantum effects in the reaction dynamics. By using the quasi-classical trajectory method and quantum mechanical close coupling data, respectively, in the high and low collision energy ranges, we obtain highly accurate thermal rate costants until 15 000 K including all (178) the roto-vibrational bound and quasi-bound states of HeH+. The role of the collision-induced dissociation is also discussed and explicitly calculated for the ground roto-vibrational state of HeH+.