Search results for "Computer Graphics"
showing 10 items of 530 documents
Form defect influence on the shrinkage fit characteristics
1998
Abstract Today, manufacturing products must meet more and more severe specifications. The different parts composing the product often necessitate high dimensional precision, which increases the difficulties for a large series production. Then it it necessary to optimize dimensioning of the different components in an economic context. In the case of small dimensional fits, there is an influence of the micro-geometry (form of defect, roughness) and time of the process on the geometrical characteristics of the assembly. At the time of conception, it is necessary to obtain a good specification that relates the product functionalities with the best cost. The objective study of this is to simulat…
A voice-activated key for the Apple Macintosh computer
1989
An interface circuit to connect a microphone to an Apple Macintosh computer is described. The Apple Macintosh mouse port is used as the input port, and the microphone activation simulates a mouse press.
Theoretical prediction of structural, vibrational and NMR parameters of plastic optical fiber (POF) material precursors. Cis and trans perhydro- and …
2014
Abstract Density functional theory (DFT) prediction of cis and trans perhydro- and perfluoro-2-methylene-4,5-dimethyl-1,3-dioxolanes structure, supported by vibrational analysis and calculation of multinuclear isotropic nuclear magnetic resonance (NMR) shieldings and indirect spin–spin couplings (SSCCs) was performed. The performance of the used methodology was verified on 1,3-dioxolane selected as model compound. The structures of hydrogenated and fluorinated monomers of POF materials were calculated using B3LYP and BLYP density functionals combined with 6-311 ++ G(3df,2pd) basis set. The BLYP/6-311++G(3df,2pd) level of theory was suggested for vibrational analysis. Gauge independent atomi…
An enantioselective synthesis of the C(33)–C(37) fragment of Amphotericin B
2003
An enantioselective synthesis of the C(33)–C(37) tripropionate fragment of Amphotericin B has been developed in only 6 steps. Peer reviewed
Density functional study of Cu2+-phenylalanine complex under micro-solvation environment
2013
Abstract We present an atomistic study carried out using density functional calculations including structural relaxations and Car–Parrinello Molecular Dynamics (CPMD) simulations, aiming to investigate the structures of phenylalanine-copper (II) ([Phe-Cu] 2+ ) complexes and their micro-solvation processes. The structures of the [Phe-Cu] 2+ complex with up to four water molecules are optimized using the B3LYP/6-311++G** model in gas phase to identify the lowest energy structures at each degree of solvation ( n = 0–4). It is found that the phenylalanine appears to be in the neutral form in isolated and mono-hydrated complexes, but in the zwitterionic form in other hydrated complexes (with n …
The mechanism of binding staphylococcal protein A to immunoglobin G does not involve helix unwinding.
1996
Structural changes in staphylococcal protein A (SpA) upon its binding to the constant region (Fc) of immunoglobulin G (IgG) have been studied by nuclear magnetic resonance and circular dichroism (CD) spectroscopy. The NMR solution structure of the engineered IgG-binding domain of SpA, the Z domain (an analogue of the B domain of SpA), has been determined by simulated annealing with molecular dynamics, using 599 distance and dihedral angle constraints. Domain Z contains three alpha-helices in the polypeptide segments Lys7 to His18 (helix 1), Glu25 to Asp36 (helix 2), and Ser41 to Ala54 (helix 3). The overall chain fold is an antiparallel three-helical bundle. This is in contrast to the previ…
Characterizing cavities in model inclusion molecules: a comparative study
1998
We have selected fullerene-60 and -70 cavities as model systems in order to test several methods for characterizing inclusion molecules. The methods are based on different technical foundations such as a square and triangular tessellation of the molecule taken as a unitary sphere, spherical tessellation of the molecular surface, numerical integration of the atomic volumes and surfaces, triangular tessellation of the molecular surface, and a cubic lattice approach to a molecular space. Accurate measures of the molecular volume and surface area have been performed with the pseudo-random Monte Carlo (MCVS) and uniform Monte Carlo (UMCVS) methods. These calculations serve as a reference for the…
On novel magnetic probe for fullerene characterization: Theoretical studies on NMR parameters of free and confined in fullerenes HD and H2 molecules
2015
Chemical characterization and separation of individual fullerenes from a raw reaction mixture need new and efficient tools, including rapid spectroscopic techniques. Recent "molecular surgery" synthesis of endohedral complexes of fullerenes with selected atoms and small molecules has opened a new path for experimental and theoretical studies on structural and spectroscopic properties of these molecular systems. Among them are fullerenes with molecular hydrogen confined within a nanoscale cavity. In this work we report on quantum-chemical prediction of nuclear magnetic shielding (and chemical shift) and indirect spin-spin coupling constant in free HD and H2 molecules, as well as models of co…
DFT study of zigzag (n, 0) single-walled carbon nanotubes: 13C NMR chemical shifts
2016
Abstract 13 C NMR chemical shifts of selected finite-size models of pristine zigzag single walled carbon nanotubes (SWCNTs) with a diameter of ∼0.4–0.8 nm and length up to 2.2 nm were studied theoretically. Results for finite SWCNTs models containing 1, 4 and 10 adjacent bamboo-type units were compared with data obtained for infinite tubes in order to estimate the reliability of small finite models in predicting magnetic properties of real-size nanotubes and to assess their tube-length dependence. SWCNTs were fully optimized using unrestricted density functional theory (DFT-UB3LYP/6-31G*). Cyclacenes, as the shortest models of open-ended zigzag SWCNTs, with systematically varying diameter w…
DFT studies on armchair (5, 5) SWCNT functionalization. Modification of selected structural and spectroscopic parameters upon two-atom molecule attac…
2015
Abstract Density functional theory (DFT) studies on adsorption of several gaseous homo- and hetero-diatomic molecules (AB) including H2, O2, N2, NO and CO on external surface of H-capped pristine armchair (5, 5) single-walled carbon nanotube (SWCNT) were conducted. Structures of C70H10 and the corresponding C70H10–AB adducts were fully optimized at the B3LYP/6-311G* level of theory. Calculated HOMO/LUMO energy gaps (Eg), 13C NMR chemical shifts and IR/Raman parameters were analyzed and critically compared with available experimental data. Significant changes of carbon NMR atom chemical shifts (up to −100 ppm) and shielding anisotropies (up to −180 ppm) at sites of addition were observed. Fu…