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+

Multi-Valley Superconductivity In Ion-Gated MoS2 Layers

Layers of transition metal dichalcogenides (TMDs) combine the enhanced effects of correlations associated with the two-dimensional limit with electrostatic control over their phase transitions by means of an electric field. Several semiconducting TMDs, such as MoS$_2$, develop superconductivity (SC) at their surface when doped with an electrostatic field, but the mechanism is still debated. It is often assumed that Cooper pairs reside only in the two electron pockets at the K/K' points of the Brillouin Zone. However, experimental and theoretical results suggest that a multi-valley Fermi surface (FS) is associated with the SC state, involving 6 electron pockets at the Q/Q' points. Here, we perform low-temperature transport measurements in ion-gated MoS$_2$ flakes. We show that a fully multi-valley FS is associated with the SC onset. The Q/Q' valleys fill for doping$\gtrsim2\cdot10^{13}$cm$^{-2}$, and the SC transition does not appear until the Fermi level crosses both spin-orbit split sub-bands Q$_1$ and Q$_2$. The SC state is associated with the FS connectivity and promoted by a Lifshitz transition due to the simultaneous population of multiple electron pockets. This FS topology will serve as a guideline in the quest for new superconductors.Comment: 12 pages, 7 figure

The He + H2+ → HeH+ + H reaction: Ab initio studies of the potential energy surface, benchmark time-independent quantum dynamics in an extended energy range and comparison with experiments

The following article appeared in Journal of Chemical Physics 137.24 (2012): 244306 and may be found at http://scitation.aip.org/content/aip/journal/jcp/137/24/10.1063/1.4772651In this work we critically revise several aspects of previous ab initio quantum chemistry studies [P. Palmieri, Mol. Phys. 98, 1835 (2000); C. N. Ramachandran, et al., Chem. Phys. Lett. 469, 26 (2009)] of the HeH2+ system. New diatomic curves for the H2+ and HeH+ molecular ions, which provide vibrational frequencies at a near spectroscopic level of accuracy, have been generated to test the quality of the diatomic terms employed in the previous analytical fittings. The reliability of the global potential energy surfaces has also been tested performing benchmark quantum scattering calculations within the time-independent approach in an extended interval of energies. In particular, the total integral cross sections have been calculated in the total collision energy range 0.955-2.400 eV for the scattering of the He atom by the ortho- and para-hydrogen molecular ion. The energy profiles of the total integral cross sections for selected vibro-rotational states of H2+ (v = 0,...,5 and j = 1,... ,7) show a strong rotational enhancement for the lower vibrational states which becomes weaker as the vibrational quantum number increases. Comparison with several available experimental data is presented and discussedThe work has been performed under the HPC-EUROPA2 project (Project No.: 228398) with the support of the European Commission - Capacities Area - Research Infrastructures. D.D.F., V.A., and S.C. thank also the Italian MIUR for PRIN contracts. A.A. acknowledges support by the program CONSOLIDERINGENIO of Ministerio de Economia y Competitividad (Spain) under Grant No. CSD2009-00038, entitled “Molecular Astrophysics: the Herschel and Alma Era,” Grant No. FIS2011-29596-C02-02, and by Comunidad Autonoma de Madrid (CAM) under Grant No. S-2009/MAT/146

Quantum Dynamics and Kinetics of the F + H2 and F + D2 Reactions at Low and Ultra-Low Temperatures

Integral cross sections and rate constants for the prototypical chemical reactions of the fluorine atom with molecular hydrogen and deuterium have been calculated over a wide interval of collision energy and temperature ranging from the sub-thermal (50 K) down to the ultra-cold regimes (0.5 mK). Rigorous close coupling time-independent quantum reactive scattering calculations have been carried out on two potential energy surfaces, differing only at long-range in the reactants' channel. The results show that tunnel, resonance and virtual state effects enhance under-barrier reactivity giving rise to pronounced deviations from the Arrhenius law as temperature is lowered. Within the ultra-cold domain (below 1 mK), the reactivity is governed by virtual state effects and by tunneling through the reaction barrier; in the cold regime (1 mK–1 K), the shape resonances in the entrance channel of the potential energy surface make the quantum tunneling contribution larger so enhancing cross sections and rate constants by about one order of magnitude; at higher temperatures (above 10 K), the tunneling pathway enhanced by the constructive interference between two Feshbach resonances trapped in the reaction exit channel competes with the thermally activated mechanism, as the energy gets closer to the reaction barrier height. The results show that at low temperatures cross sections and rate constants are extremely sensitive to small changes in the long-range intermolecular interaction in the entrance channel of the potential energy surface, as well as to isotopic substitution

Non-adiabatic Quantum Dynamics of the Dissociative Charge Transfer He++H2 → He+H+H+

We present the non-adiabatic, conical-intersection quantum dynamics of the title collision where reactants and products are in the ground electronic states. Initial-state-resolved reaction probabilities, total integral cross sections, and rate constants of two H2 vibrational states, v0 = 0 and 1, in the ground rotational state (j0 = 0) are obtained at collision energies Ecoll ≤ 3 eV. We employ the lowest two excited diabatic electronic states of HeH2+ and their electronic coupling, a coupled-channel time-dependent real wavepacket method, and a flux analysis. Both probabilities and cross sections present a few groups of resonances at low Ecoll, whose amplitudes decrease with the energy, due to an ion-induced dipole interaction in the entrance channel. At higher Ecoll, reaction probabilities and cross sections increase monotonically up to 3 eV, remaining however quite small. When H2 is in the v0 = 1 state, the reactivity increases by ~2 orders of magnitude at the lowest energies and by ~1 order at the highest ones. Initial-state resolved rate constants at room temperature are equal to 1.74 × 10−14 and to 1.98 × 10−12 cm3s−1 at v0 = 0 and 1, respectively. Test calculations for H2 at j0 = 1 show that the probabilities can be enhanced by a factor of ~1/3, that is ortho-H2 seems ~4 times more reactive than para-H2

CFRPs drilling: comparison among holes produced by different drilling strategies

Abstract The drilling process of CFRPs is the most commonly employed machining operation owing to the need for joining these structures. However, these materials are prone to delaminate during the process and the presence of these defects can be a cause of rejection of these components. Therefore, this paper aims on the study of alternative drilling strategies such as: the orbital and a new drilling strategy (called circular drilling) to reduce the delaminations extension. Holes 8 mm in diameter were obtained by using different drilling strategies and cutting conditions and their influence on the cutting forces and delamination factor was studied

Experimental Investigations on Bending Collapse Modes of Innovative Sandwich Panels with Metallic Foam Core

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Impact behaviour of a new Hemp/Carbon sandwich structure

Abstract This paper aims to present a new sandwich structure comprising of a grid hemp core and carbon skins. Two typology of hemp cores (7 and 8 mm in thickness) that mainly differ in the density values (0.36 and 0.63 g/cm3) were produced by an ad hoc manufacturing process and adopted to produce the sandwich structures under investigation. Aiming to extend the use of natural fibre composites (NFCs) for applications where high impact resistance is required and to replace common materials used as cores with more eco-friendly ones like the proposed hemp core, low velocity impact (LVI) tests and non-destructive (ND) tests were carried out

A pilot study employing hepatic intra-arterial irinotecan injection of drug-eluting beads as salvage therapy in liver metastatic colorectal cancer patients without extrahepatic involvement: The first southern Italy experience

Background: The main aim of this prospective study was to evaluate the efficacy of drug-eluting beads with irinotecan (DEBIRI) for liver metastases from colorectal cancer. Secondary aims were to evaluate survival and toxicity. Methods: Twenty-five patients with metastases in <50% of the liver and without extrahepatic involvement were enrolled. Treatment response assessment was performed by multidetector contrast enhancement computed tomography (MDCT) with evaluation of the enhancement pattern of the target lesion and tumor response rates according to modified Response Evaluation Criteria in Solid Tumors (mRECIST, Version 1.1). All adverse events were recorded by the Cancer Therapy Evaluation Program Common Terminology Criteria for Adverse Events, Version 3.0. Associations of tumor response and variables were calculated using the chi-squared test. Overall survival (OS) was calculated using the Kaplan–Meier method. Comparisons were made using the log-rank test. Results: According to mRECIST, complete response (CR) was observed in 21.8% of patients, partial response (PR) in 13%, stable disease (SD) in 52.2% and progressive disease (PD) in 13% of patients. Response rate (RR = CR + PR) was 34.8%. No associations between treatment response and variables such as Dukes’ classification, grading and Kras status were found (P>0.05). The median OS was 37 months (95% CI: 13.881 to 60.119). Cox regression model showed that neither site, Dukes’ classification, grading, Kras status nor number of chemotherapy treatments pre-DEBIRI influenced the OS. The log-rank test showed no statistically significant difference in OS among patients who underwent 1, 2 or 3 DEBIRI treatments (χ2=2.831, P=0.09). In our study, the main toxicities included postembolization syndrome (PES), hypertransaminasemia and fever. Conclusion: The favorable tumor response and the favorable toxicity profile make DEBIRI treatment a potential third-line therapy. Although further larger studies are needed to confirm these data, we can state that DEBIRI is an attractive emerging treatment in these patients

The BLAST Survey of the Vela Molecular Cloud: Physical Properties of the Dense Cores in Vela-D

The Balloon-borne Large-Aperture Submillimeter Telescope (BLAST) carried out a 250, 350 and 500 micron survey of the galactic plane encompassing the Vela Molecular Ridge, with the primary goal of identifying the coldest dense cores possibly associated with the earliest stages of star formation. Here we present the results from observations of the Vela-D region, covering about 4 square degrees, in which we find 141 BLAST cores. We exploit existing data taken with the Spitzer MIPS, IRAC and SEST-SIMBA instruments to constrain their (single-temperature) spectral energy distributions, assuming a dust emissivity index beta = 2.0. This combination of data allows us to determine the temperature, luminosity and mass of each BLAST core, and also enables us to separate starless from proto-stellar sources. We also analyze the effects that the uncertainties on the derived physical parameters of the individual sources have on the overall physical properties of starless and proto-stellar cores, and we find that there appear to be a smooth transition from the pre- to the proto-stellar phase. In particular, for proto-stellar cores we find a correlation between the MIPS24 flux, associated with the central protostar, and the temperature of the dust envelope. We also find that the core mass function of the Vela-D cores has a slope consistent with other similar (sub)millimeter surveys.Comment: Accepted for publication in the Astrophysical Journal. Data and maps are available at http://blastexperiment.info