Search results for "Application"

From Molecules to Systems: Sol-Gel Microencapsulation in Silica-Based Materials

2010

Improving the QM/MM Description of Chemical Processes:  A Dual Level Strategy To Explore the Potential Energy Surface in Very Large Systems.

2005

Potential energy surfaces are fundamental tools for the analysis of reaction mechanisms. The accuracy of these surfaces for reactions in very large systems is often limited by the size of the system even if hybrid quantum mechanics/molecular mechanics (QM/MM) strategies are employed. The large number of degrees of freedom of the system requires hundreds or even thousands of optimization steps to reach convergence. Reactions in condensed media (such as enzymes or solutions) are thus usually restricted to be analyzed using low level quantum mechanical methods, thus introducing a source of error in the description of the QM region. In this paper, an alternative method is proposed, coupled to t…

Adsorbed CO on group 10 metal fragments: A DFT study

2009

DFT calculations on the helicopter and cartwheel rotations of one CO molecule adsorbed at the bridge site on metal-surface fragments, characterized by two (M(8)) or three (M(14)) metal-atom layers (M = Ni, Pd, Pt) were performed by the B3LYP[LANL2DZ+6-31 g(d,p)] method, to rationalize the adsorption energetics and the steric hindrance characteristics of surface CO molecules. Potential Energy Surfaces were obtained, either fixing the C-O bond-length or allowing it to change. The behavior of the three metals, as obtained from the study of the configurational space characterizing the CO adsorption on the fragments was explained on the basis of the interaction energies involved in the different…

The Nature of Transannular Interactions in E4N4 and E82+ (E = S, Se)

2015

The electronic structures of tetrachalcogen tetranitrides, E4N4, and octachalcogen dications, E8(2+), and the nature of their intramolecular E···E interactions (E = S, Se) was studied with high-level theoretical methods. The results reveal that the singlet ground states of both systems have a surprisingly large correlation contribution which functions to weaken and therefore lengthen the cross-ring E-E bond. The observed correlation effects are primarily static in E4N4, whereas in E8(2+) the dynamic part largely governs the total correlation contribution. The presented description of bonding is the first that gives an all-inclusive picture of the origin of cross-ring interactions in E4N4 an…

Computational Study on Cesium Azide Trapped in a Cyclopeptidic Tubular Structure

2008

The structures and the electronic properties of host-guest complexes formed by a cyclopeptidic tubular aggregate and the species CsN3, CS2(N-3)(2), and CS2N6 have been investigated by means of density functional theory. Taking advantage of the azide property to act as a bridge ligand between two or more metal cations, it may be possible to trap N-3(-) ions inside a confined space. This could be important for the preparation of polynitrogen molecules N-n. Results show that there are significant attractive interactions between the azide ion and the cavity walls, which make the ion stay inside the inner empty space of the cyclopeptidic aggregate. The confinement of the species CS2(N-3)(2) forc…

Relaxation Mechanisms of 5-Azacytosine.

2015

The photophysics and deactivation pathways of the noncanonical 5-azacytosine nucleobase were studied using the CASPT2//CASSCF protocol. One of the most significant differences with respect to the parent molecule cytosine is the presence of a dark (1)(nNπ*) excited state placed energetically below the bright excited state (1)(ππ*) at the Franck-Condon region. The main photoresponse of the system is a presumably efficient radiationless decay back to the original ground state, mediated by two accessible conical intersections involving a population transfer from the (1)(ππ*) and the (1)(nNπ*) states to the ground state. Therefore, a minor contribution of the triplet states in the photophysics o…

The e-ASTROGAM gamma-ray space observatory for the multimessenger astronomy of the 2030s

2018

e-ASTROGAM is a concept for a breakthrough observatory space mission carrying a gamma-ray telescope dedicated to the study of the non-thermal Universe in the photon energy range from 0.15 MeV to 3 GeV. The lower energy limit can be pushed down to energies as low as 30 keV for gamma-ray burst detection with the calorimeter. The mission is based on an advanced space-proven detector technology, with unprecedented sensitivity, angular and energy resolution, combined with remarkable polarimetric capability. Thanks to its performance in the MeV-GeV domain, substantially improving its predecessors, e-ASTROGAM will open a new window on the non-thermal Universe, making pioneering observations of the…

Dynamics and risk assessment of pesticides in cucumber through field experiments and model simulation

2020

Abstract Pesticides are often applied multiple times during cucumber cultivation in China. In order to obtain the residue concentrations and subsequently human health risk assessment after pesticide multiple applications, plenty of field trials have been conducted, consuming a lot of labor force and funds. The application of kinetic models can address this problem to some extent by predicting the residue values of pesticides in cucumber. In this study, a dynamic model (dynamiCROP) was applied in combination with field experiments to investigate the distribution, translocation, and dissipation after the one-time application of seven pesticides in a cucumber-soil environment. Moreover, the re…

Linking chlorophyll a fluorescence to photosynthesis for remote sensing applications: mechanisms and challenges

2014

Chlorophyll a fluorescence (ChlF) has been used for decades to study the organization, functioning, and physiology of photosynthesis at the leaf and subcellular levels. ChlF is now measurable from remote sensing platforms. This provides a new optical means to track photosynthesis and gross primary productivity of terrestrial ecosystems. Importantly, the spatiotemporal and methodological context of the new applications is dramatically different compared with most of the available ChlF literature, which raises a number of important considerations. Although we have a good mechanistic understanding of the processes that control the ChlF signal over the short term, the seasonal link between ChlF…

RIP-Chip analysis supports different roles for AGO2 and GW182 proteins in recruiting and processing microRNA targets.

2019

Background MicroRNAs (miRNAs) are small non-coding RNA molecules mediating the translational repression and degradation of target mRNAs in the cell. Mature miRNAs are used as a template by the RNA-induced silencing complex (RISC) to recognize the complementary mRNAs to be regulated. To discern further RISC functions, we analyzed the activities of two RISC proteins, AGO2 and GW182, in the MCF-7 human breast cancer cell line. Methods We performed three RIP-Chip experiments using either anti-AGO2 or anti-GW182 antibodies and compiled a data set made up of the miRNA and mRNA expression profiles of three samples for each experiment. Specifically, we analyzed the input sample, the immunoprecipita…