Performance Tests of HX340 Microalloyed Steel Sheets Joined Using Clinch-Rivet Technology.

This paper presents the possibility of forming a pressed joint between two 1.5 mm thick sheets made of HX340 steel. The joint was formed using an additional deformable steel rivet with a hardness of 400HV1. Different distances of rivet pressing below the initial surface of the upper sheet were chosen: 0, 0.15, 0.30, 0.45 and 0.60 (in mm). For the mentioned rivet-pressing distances, forming tests were performed using an "SKB" die with three die depths: 1.45, 1.60 and 1.75 (in mm). Observations and measurements of the characteristic geometric dimensions of the interlock were made. Furthermore, the strength of the clinch-riveted joints was analysed. Changing the depth of the die by 20%, i.e., from hd = 1.45 mm to hd = 1.75 mm for the same rivet press-in depth (of = 0%), resulted in a 12% reduction in the forming-force value. The maximum load capacity of the joint in the shear test decreased by 3.5% for the mentioned joint variant. The greater the rivet press-in depth used in the joint (of), the greater the value of the interlock size (tu). Increasing the value of rivet-pressing depth below the initial surface of the upper sheet from 0 mm to 0.6 mm resulted in an increase in the size of the interlock (tu) by 136% (for hd = 1.45 mm), by 128% (for hd = 1.60 mm) and by 85% (for hd = 1.75 mm).

Efficacy of oral amantadine among patients hospitalised with COVID-19: A randomised, double-blind, placebo-controlled, multicentre study.

BACKGROUND: Amantadine has been proposed as a treatment for COVID-19 because it shows anti-SARS-CoV-2 activity in vitro. However, to date, no controlled study has assessed the safety and efficacy of amantadine in COVID-19. RESEARCH QUESTION: Whether amantadine is effective and safe among patients with different COVID-19 severity classifications. STUDY DESIGN: and Methods: This was multi-centre, randomised, placebo-controlled study.Patients with oxygen saturation ≤94% and no need for high-flow oxygen or ventilatory support were randomly allocated to receive oral amantadine or placebo (1:1) for 10 days in addition to standard care. The primary endpoint was time to recovery assessed over 28 days since randomisation, defined as discharge from hospital or no need for supplemental oxygen. RESULTS: The study was terminated early due to a lack of efficacy after an interim analysis. Final data from 95 patients who received amantadine (mean age, 60.2 years; 65% male; 66% with comorbidities) and 91 patients who received placebo (mean age, 55.8 years; 60% male; 68% with comorbidities) were obtained. The median (95% CI) time to recovery was 10 days both in the amantadine (9-11) and placebo arms (8-11; subhazard ratio = 0.94 [95%CI 0.7-1.3]). The percentage of deaths and percentage of patients who required intensive care at 14 and 28 days did not significantly differ between the amantadine and placebo groups. INTERPRETATION: Adding amantadine to standard care in patients hospitalised with COVID-19 did not increase the likelihood of recovery. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov; No.: NCT04952519; www. CLINICALTRIALS: gov.

Theoretical Study of Proton Tunneling in the Imidazole-Imidazolium Complex.

Proton tunneling in the hydrogen-bonded imidazole-imidazolium complex ion has been studied theoretically. Ab initio CASSCF/6-311++G(d,p) calculations concerning geometry optimization and vibrational frequencies have been carried out for equilibrium and transition state structures of the system. Two-dimensional double-well model potentials were constructed on the basis of ab initio results and used to analyze the proton dynamics in the hydrogen bond and the influence of the excitation of low-frequency hydrogen-bond vibrations on the proton tunneling splittings. The energy of tunneling-split vibrational sublevels of the high-frequency tunneling mode have been calculated for its ground and first excited vibrational state for the series of excitations of the coupled low-frequency intramolecular hydrogen-bond modes. The promoting and suppressing effect of the low-frequency modes on the proton splittings was shown in the ground and first excited vibrational state of the tunneling mode. The vibrational sublevels form the two separate semicontinuous bands between which the absorption transitions may occur. This mechanism explains the experimentally observed splitting and doublet-component broadening of the high-frequency N-H stretching infrared (IR) absorption band.

Infrared Spectroscopy and Born-Oppenheimer Molecular Dynamics Simulation Study on Deuterium Substitution in the Crystalline Benzoic Acid.

In this study we present complementary computational and experimental studies of hydrogen bond interaction in crystalline benzoic acid and its deuterated and partially deuterated derivatives. The experimental part of the presented work includes preparation of partially deuterated samples and measurement of attenuated total reflection (ATR)-FTIR spectra. Analysis of the geometrical parameters and time course of dipole moment of crystalline benzoic acid and its deuterated and partially deuterated derivatives by Born-Oppenheimer molecular dynamics (BOMD) enabled us to deeply analyze the IR spectra. Presented simulations based on BOMD gave us opportunity to investigate individual motion and its contribution to the IR spectra. The band contours calculated using Fourier transform of autocorrelation function are in quantitative agreement with the experimental spectra. Characterization of single bands was carried out by "normal coordinate analysis". The salient point of our study is a comparison of the spectra of the deuterated and partially deuterated crystalline benzoic acid with that of the nondeuterated one. Furthermore, we have applied the principal component analysis for analysis of the number of components in partially deuterated systems. In this study, we reveal that the arrangements of hydrogen and deuterium atoms in partially deuterated samples are random.

Quantum-mechanical study of energies, structures, and vibrational spectra of the H(D)Cl complexed with dimethyl ether.

Interaction energies, molecular structure and vibrational frequencies of the binary complex formed between H(D)Cl and dimethyl ether have been obtained using quantum-chemical methods. Equilibrium and vibrationally averaged structures, harmonic and anharmonic wavenumbers of the complex and its deuterated isotopomer were calculated using harmonic and anharmonic second-order perturbation theory procedures with Density Functional Theory B3LYP and B2PLYP-D and ab initio Møller-Plesset second-order methods, and a 6-311++G(3d,3p) basis set. A phenomenological model describing anharmonic-type vibrational couplings within hydrogen bonds was developed to explain the unique broadening and fine structure, as well as the isotope effect of the Cl-H and Cl-D stretching IR absorption bands in the gaseous complexes with dimethyl ether, as an effect of hydrogen bond formation. Simulations of the rovibrational structure of the Cl-H and Cl-D stretching bands were performed and the results were compared with experimental spectra.

Theoretical study of proton tunneling in the excited state of tropolone.

Ab initio CIS/6-311++G(d,p) calculations of geometry and vibrational frequencies have been carried out in the A state of tropolone. The grids of potential energy surfaces along the coordinates of high frequency tunneling vibration and the low-frequency coupled vibration have been calculated. Two-dimensional model potentials, formed from symmetric mode coupling potential and squeezed double well potential, have been fitted to the calculated potential energy surfaces and used to analyze proton dynamics. The tunneling splittings for different vibrationally excited states have been calculated and compared with the available experimental data. The model potential energy surfaces, based on the CIS/6-311++G(d,p) calculations, give good estimation of the tunneling energy splittings in the vibrationally ground and excited states of tropolone and explain monotonic decrease in tunneling splittings with the excitation of low-frequency out-of-plane modes and increase in the tunneling splittings with the excitation of low-frequency planar modes.

Theoretical modeling of the O-H stretching IR bands of hydrogen-bonded dimers of benzoic acid in S(0) and S(1) electronic states.

Theoretical model for vibrational interactions in the hydrogen-bonded dimer of benzoic acid is presented. The model takes into account anharmonic-type couplings between the high-frequency O-H and the low-frequency O[cdots, three dots, centered]O stretching vibrations in two hydrogen bonds, resonance interactions (Davydov coupling) between two hydrogen bonds in the dimer, and Fermi resonance between the O-H stretching fundamental and the first overtone of the O-H in-plane bending vibrations. The vibrational Hamiltonians and selection rules for the C(2h) geometry in the S(0) state and for the C(s) in-plane bent geometry in the S(1) state of the dimer are derived. The model is used for theoretical simulation of the O-H stretching IR absorption bands of benzoic acid dimers in the gas phase in the electronic ground and first excited singlet states. Ab initio CIS and CIS(D)6-311++G(d,p) calculations have been performed to determine geometry, frequencies, and excited state energies of benzoic acid dimer in the S(1) state.

Theoretical model of infrared spectra of hydrogen bonds in molecular crystals and its application to interpretation of infrared spectra of 1-methylthymine.

A theoretical model for vibrational interactions in the hydrogen bonds in molecular crystals with four molecules forming two centrosymmetric dimers in the unit cell is presented. The model takes into account anharmonic-type couplings between the high-frequency N-H(D) and the low-frequency N...O stretching vibrations in each hydrogen bond, resonance interactions (Davydov coupling) between equivalent hydrogen bonds in each dimer, resonance interdimer interactions within a unit cell, and Fermi resonance between the N-H(D) stretching fundamental and the first overtone of the N-H(D) in-plane bending vibrations. The vibrational Hamiltonian, selection rules, and expressions for the integral properties of an absorption spectrum are derived. The model is used for theoretical simulation of the NH stretching bands of 1-methylthymine and its ND derivative at 300 K. The effect of deuteration is successfully reproduced by our model. Infrared, far-infrared, Raman, and low-frequency Raman spectra of 1-methylthymine and its deuterated derivative have been measured. Experimental geometry and frequencies are compared with the results of density functional theory calculations performed at the B3LYP6-311++G**, B3LYP/cc-pVTZ, B3PW916-311++G**, and B3PW91/cc-pVTZ levels.

Theoretical model for a tetrad of hydrogen bonds and its application to interpretation of infrared spectra of salicylic acid.

Theoretical model of vibrational interactions in hydrogen-bonded salicylic acid dimer is presented which takes into account the adiabatic couplings between high- and low-frequency O-H and O...O stretching vibrations, resonance interactions between both intermolecular hydrogen bonds and between inter- and intramolecular hydrogen bonds, and Fermi resonance between the O-H stretching fundamental and the first overtone of the O-H in-plane bending vibrations. The model is used for theoretical simulation of the nu(s) stretching bands of salicylic acid and its OD derivative at 300 K. The effect of deuteration is successfully reproduced by our model. Infrared, far infrared, Raman, and low-frequency Raman spectra of the polycrystalline salicylic acid and its deuterated derivative have been measured. The geometry and experimental frequencies are compared with the results of density-functional theory calculations performed at the B3LYP6-31 ++ G**, B3LYP/cc-pVTZ, B3PW916-31 ++ G**, and B3PW91/cc-pVTZ levels. O-H, O-D, and O...O stretching frequencies are used in theoretical simulation of the nu(s) stretching bands.

Theoretical modeling of infrared spectra of hydrogen-bonded crystals of salicylic acid.

A theoretical model for the infrared spectra in the O-H stretching region of hydrogen-bonded salicylic acid is presented. Based on the model, infrared spectrum in the O-H stretching region is calculated for salicylic acid and compared with the experimental one. The experimental and theoretical spectra are in good agreement.