Search results for " effect"
showing 10 items of 7524 documents
Explicit Solvation Matters: Performance of QM/MM Solvation Models in Nucleophilic Addition
2018
Nucleophilic addition onto a carbonyl moiety is strongly affected by solvent, and correctly simulating this solvent effect is often beyond the capability of single-scale quantum mechanical (QM) models. This work explores multiscale approaches for the description of the reversible and highly solvent-sensitive nucleophilic N|···C=O bond formation in an Me2N–(CH2)3–CH=O molecule. In the first stage of this work, we rigorously compare and test four recent quantum mechanical/molecular mechanical (QM/MM) explicit solvation models, employing a QM description of water molecules in spherical regions around both the oxygen and the nitrogen atom of the solute. The accuracy of the models is benchmarked…
Characteristics of the polymer transport in ratchet systems
2010
Molecules with complex internal structure in time-dependent periodic potentials are studied by using short Rubinstein-Duke model polymers as an example. We extend our earlier work on transport in stochastically varying potentials to cover also deterministic potential switching mechanisms, energetic efficiency and non-uniform charge distributions. We also use currents in the non-equilibrium steady state to identify the dominating mechanisms that lead to polymer transportation and analyze the evolution of the macroscopic state (e.g., total and head-to-head lengths) of the polymers. Several numerical methods are used to solve the master equations and nonlinear optimization problems. The domina…
A study of Wigner functions for discrete-time quantum walks
2013
We perform a systematic study of the discrete time Quantum Walk on one dimension using Wigner functions, which are generalized to include the chirality (or coin) degree of freedom. In particular, we analyze the evolution of the negative volume in phase space, as a function of time, for different initial states. This negativity can be used to quantify the degree of departure of the system from a classical state. We also relate this quantity to the entanglement between the coin and walker subspaces.
Potentialities of microfibers for non linear optics
2010
Micro- and nanofibers present attractive optical properties and may be used in a variety of structures and devices. We report in this work the first global study on the non linear properties of these microfibers: an adequate source is built and its characteristics are described, our first results with a silica loop resonator are presented. Third harmonic generation is obtained in these conditions, however, the low intrinsic non linear index prevents the generation of large non linear effects. The use of highly non linear materials, such as soft glasses, is therefore discussed, with their potentialities and the challenges their integration with standard microfibers represent.
COVID-19 Pandemic: Prevention and protection measures to be adopted at the workplace
2020
Introduction: SARS-CoV-2, identified in Wuhan, China, for the first time in December 2019, is a new viral strain, which has not been previously identified in humans; it can be transmitted both by air and via direct and indirect contact; however, the most frequent way it spreads is via droplets. Like the other viruses belonging to the same family of coronaviruses, it can cause from mild flu-like symptoms, such as cold, sore throat, cough and fever, to more severe ones such as pneumonia and breathing difficulties, and it can even lead to death. Since no effective specific drug therapy has been found yet, nor any vaccine capable of limiting the spread of this pathogen, it is important for way…
Carbon nanotube field-effect devices with asymmetric electrode configuration by contact geometry
2014
We have studied experimentally the conductive properties of single walled carbon nanotube (SWNT) based field-effect type devices, with different contact geometries at the connecting electrode. The device designs are asymmetric with one end of the SWNT having the metal electrode deposited on top and immersing it, while at the other end, the SWNT is on top of the electrode. The devices were made with either gold or palladium as electrode materials, of which the latter resulted in different behavior of the different contact types. This is argued to be caused by the existence of a thin insulating layer of surface adsorbents on the palladium, possibly Pd5O4, the effect of which is enhanced by th…
The Importance of Recovery from Work in Intensified Working Life
2021
This chapter focuses on intensified working life via the intensified job demands (IJDs) model from the perspective of recovery from work by paying particular attention to the potentially mediating and buffering roles of recovery in the linkages between IJDs and their consequences. In empirical analyses, we examined the buffering role of psychological detachment from work during off-job time in the relationship between intensified job demands and job performance and meaning of work. We found that high psychological detachment, as a recovery experience, buffered against work intensification over time in relation to job performance and meaning of work. Thus, good detachment from work during of…
A Social-Empowered Platform for Gathering Semantic Information
2013
Social Networks constitute the key ingredient for the huge success of the so called Social Web or Web 2.0. In social networks, a user has the possibility to interact with other users without the need of meeting them. The value of social applications benefit from the network effect, which states that the value of a service to a user arises from the number of people using the service. However, the associated semantics for this kind of applications, delivered through tagging, is generally scarce, thus narrowing the range of permissible operations for exploiting these data. In this paper, we present a semantic-based social platform that incorporates the benefits of semantic Web technologies int…
A high-temperature x-ray absorption spectroscopy study of
1996
We present for the first time a high-temperature x-ray absorption spectroscopy study of at the edge. The analysis both of the XANES and of the EXAFS regions shows that, in , a progressive localization of the 5d states following the temperature rise is accompanied at T > 350 K by a distortion of the octahedra, which increases up to the decomposition temperature . The distortion leads to the lowering of the rhenium site symmetry from and is due to the electron - phonon coupling of the 5d electrons with the and phonons and to the Jahn - Teller effect caused by the rhenium electron which becomes localized at high temperature.
X‐Ray Photoelectron Spectroscopy
2021
X-ray photoelectron spectroscopy (XPS) is a spectroscopic technique in the family of electron spectroscopies, that is, those methods whose probe consists of electrons instead of photons. In the case of XPS, a soft, usually monochromatic X-ray causes the emission of electrons by means of the photoelectric effect. Differences in chemical potential and/or polarizability of the molecules can cause an alteration of the binding energy; in addition to photoelectrons, an ordinary XPS spectrum may also contain Auger electrons. In an XPS system, an electron gun is used to deliver a low-energy electron flux with a low current over the illuminated spot. In an XPS instrument, an ion gun may be used with…