Search results for "force"
showing 10 items of 3423 documents
Competing factors on the frequency separation between the OH stretching modes in water
2015
Abstract Recent simulations demonstrated that the inhomogeneous broadening as observed in the vibrational spectra of liquid water at ambient conditions can be viewed as a large vibrational splitting of symmetric and asymmetric OH stretching modes, due to the asymmetry of the local hydrogen-bonding network [J. Phys. Chem. Lett., 2013, 4(19), pp 3245–3250]. In this work, we show that the finite temperature and the liquid phase do not only modulate the local hydrogen-bonding asymmetry of water molecules, but also the intramolecular coupling strength. These two factors compete together in the determination of the overall magnitude of the frequency separation between the two OH stretching modes …
Iron’s Wake: The Performance of Quantum Mechanical-Derived Versus General-Purpose Force Fields Tested on a Luminescent Iron Complex
2020
Recently synthetized iron complexes have achieved long-lived excited states and stabilities which are comparable, or even superior, to their ruthenium analogues, thus representing an eco-friendly and cheaper alternative to those materials based on rare metals. Most of computational tools which could help unravel the origin of this large efficiency rely on ab-initio methods which are not able, however, to capture the nanosecond time scale underlying these photophysical processes and the influence of their realistic environment. Therefore, it exists an urgent need of developing new low-cost, but still accurate enough, computational methodologies capable to deal with the steady-state and trans…
Grand Canonical Monte Carlo Simulations to Determine the Optimal Interlayer Distance of a Graphene Slit-Shaped Pore for Adsorption of Methane, Hydrog…
2021
The adsorption—for separation, storage and transportation—of methane, hydrogen and their mixture is important for a sustainable energy consumption in present-day society. Graphene derivatives have proven to be very promising for such an application, yet for a good design a better understanding of the optimal pore size is needed. In this work, grand canonical Monte Carlo simulations, employing Improved Lennard–Jones potentials, are performed to determine the ideal interlayer distance for a slit-shaped graphene pore in a large pressure range. A detailed study of the adsorption behavior of methane, hydrogen and their equimolar mixture in different sizes of graphene pores is obtained through ca…
Investigations on the linear friction welding process through numerical simulations and experiments
2012
Abstract Linear Friction Welding (LFW) is a solid-state joining process applied to non-axisymmetric components. LFW involves joining of materials through the relative motion of two components undergoing an axial force. In such process the heat source is given by the frictional forces work decaying into heat determining a local softening of the material and eventually bonding conditions. In the paper the authors present a designed and assembled laboratory fixture for LFW operations and the results of an experimental and numerical campaign aimed to weld steel parts. The dedicated fixture permitted to highlight the effect of the most important process parameters. Process conditions allowing ef…
Interaction of Charged Amino-Acid Side Chains with Ions: An Optimization Strategy for Classical Force Fields
2014
Many well-established classical biomolecular force fields, fitted on the solvation properties of single ions, do not necessarily describe all the details of ion pairing accurately, especially for complex polyatomic ions. Depending on the target application, it might not be sufficient to reproduce the thermodynamics of ion pairing, but it may also be necessary to correctly capture structural details, such as the coordination mode. In this work, we analyzed how classical force fields can be optimized to yield a realistic description of these different aspects of ion pairing. Given the prominent role of the interactions of negatively charged amino-acid side chains and divalent cations in many …
Early stages of beta2-microglobulin aggregation and the inhibiting action of alphaB-crystallin
2008
The interest of nucleation of protein crystals and aggregates (including oligomerization) spans from basic physics theory all the way to biophysics, nanophysics, clinical sciences, biotechnologies, food technologies and polymer-solvent interactions. Understanding nucleation within a theoretical framework capable of providing quantitative predictions and control of nucleation rates, or even the very occurrence of crystallization, is a long-sought goal of remarkable relevance to each of the above fields. A large amount of work has been aimed at such goal, but success has been so far rather limited. Work at our laboratory has more recently highlighted a direct link between nucleation rates and…
Factors Contributing to Different Agency in Work and Study
2013
Most young adults today are following longer educational tracks and postpone entrance into the workforce. This 2-year study aimed to determine factors contributing to occupational self-efficacy in a representative sample of n = 1,891 young adults ( M = 23.92, SD = 2.17 years) with different work statuses (studying, in an apprenticeship, employed, or unemployed). Occupational identity, perceived work quality, the ability to cope with work stress, and symptomatology were assessed. Path analyses revealed that work status was the most important predictor of later occupational self-efficacy, with employment showing the strongest prediction of later agency in the professional domain. Ruminative e…
A Public Barrier Tracker to Support the Web Accessibility Directive
2018
In this paper we propose the Public Barrier Tracker (PBT) – a comprehensive solution that supports both filing and handling of user feedback on web accessibility. We give an overview of some existing approaches for gathering user feedback on accessibility barriers and outline the PBT functionality. The PBT can also offer further support for the implementation of the WAD: The collected data could be useful for monitoring and reporting as well as the enforcement mechanism.
The Use of X-ray Absorption Spectra for Validation of Classical Force-Field Models
2015
Abstract Extended X-ray absorption fine structure (EXAFS) spectroscopy and molecular dynamics (MD) simulations are two complementary techniques widely used to study the atomic structure of materials. Their combined use, known as the MD-EXAFS approach, allows one to access the structural information, encoded in EXAFS, far beyond the nearest coordination shells and to validate the accuracy of the interaction potential models. In this study we demonstrate the use of the MD-EXAFS method for a validation of several force-field models on an example of the cubic-perovskite SrTiO3 and hexagonal wurtzite-type ZnO crystals.
Methyl 3,3,6,6-tetramethyl-1,8-dioxo-4,5,7,9-tetrahydro-2H-xanthene-9-carboxylate
2020
The title molecule, C19H24O5, is built by annulation of a half-chair cyclohexenone and a twist-cyclohexenone to a flat 4-H-pyrane boat. In the crystal, molecules are connected via van der Waals interactions and C—H...O hydrogen bonds.