Search results for "Computer Science Applications"
showing 10 items of 3993 documents
Structural modelling and mechanical tests supporting the design of the ATHENA X-IFU thermal filters and WFI optical blocking filter
2018
Copyright 2018 Society of Photo-Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. ATHENA is a Large high energy astrophysics space mission selected by ESA in the Cosmic Vision 2015-2025 Science Program. It will be equipped with two interchangeable focal plane detectors: the X-Ray Integral Field Unit (X-IFU) and the Wide Field Imager (WFI). Both detectors require x-ray transparent filters to fully exploit their sensitivity. In order to maximize the X-ray tra…
Cost analysis of a vaccination strategy for respiratory syncytial virus (RSV) in a network model
2010
[EN] In this paper an age-structured mathematical model for respiratory syncytial virus (RSV) is proposed where children younger than one year old, who are the most affected by this illness, are specially considered. Real data of hospitalized children in the Spanish region of Valencia are used in order to determine some seasonal parameters of the model. Once the parameters are determined, we propose a complete stochastic network model to study the seasonal evolution of the respiratory syncytial virus (RSV) epidemics. In this model every susceptible individual can acquire the disease after a random encounter with any infected individual in the social network. The edges of a complete graph co…
Importance of Triples Contributions to NMR Spin–Spin Coupling Constants Computed at the CC3 and CCSDT Levels
2016
We present the first analytical implementation of CC3 second derivatives using the spin-unrestricted approach. This allows, for the first time, the calculation of nuclear spin–spin coupling constants (SSCC) relevant to NMR spectroscopy at the CC3 level of theory in a fully analytical manner. CC3 results for the SSCCs of a number of small molecules and their fluorine substituted derivatives are compared with the corresponding coupled cluster singles and doubles (CCSD) results obtained using specialized basis sets. For one-bond couplings the change when going from CCSD to CC3 is typically 1–3%, but much higher corrections were found for 1JCN in FCN, 15.7%, and 1JOF in OF2, 6.4%. The changes v…
The tensor of interaction of a two-level system with an arbitrary strain field
2007
The interaction between two-level systems (TLS) and strain fields in a solid is contained in the diagonal matrix element of the interaction hamiltonian, $\delta$, which, in general, has the expression $\delta=2[\gamma]:[S]$, with the tensor $[\gamma]$ describing the TLS ``deformability'' and $[S]$ being the symmetric strain tensor. We construct $[\gamma]$ on very general grounds, by associating to the TLS two objects: a direction, $\hat\bt$, and a forth rank tensor of coupling constants, $[[R]]$. Based on the method of construction and on the invariance of the expression of $\delta$ with respect to the symmetry transformation of the solid, we conclude that $[[R]]$ has the same structure as …
Relativistic DFT Calculation of (119)Sn Chemical Shifts and Coupling Constants in Tin Compounds.
2006
The nuclear shielding and spin-spin coupling constants of (119)Sn in stannane, tetramethylstannane, methyltin halides Me4-nSnXn (X = Cl, Br, I; n = 1-3), tin halides, and some stannyl cations have been investigated computationally by DFT methods and Slater all-electron basis sets, including relativistic effects by means of the zeroth order regular approximation (ZORA) method up to spin-orbit coupling. Calculated (119)Sn chemical shifts generally correlate well with experimental values, except when several heavy halogen atoms, especially iodine, are bound to tin. In such cases, calculated chemical shifts are almost constant at the scalar (spin-free) ZORA level; only at the spin-orbit level i…
Coupling Mechanics of Antikythera Gearwheels
2012
This paper discusses the gear coupling mechanics of the ancient Antikythera mechanism, among whose distinctive characteristics was the triangular shaping of the teeth. The engagement of the tooth pairs is analyzed in detail, estimating the temporal variation of the speed ratio due to the back and forth shifting of the relative instant center. The admissibility of the theoretical contact points is carefully checked, and the magnitude of the successive tooth collisions is calculated together with the energy losses arising from the particular nature of the coupling. Some interesting results are that only one tooth pair turns out to be active at each time instant and the real path may belong on…
A fast BEM for the analysis of damaged structures with bonded piezoelectric sensors
2010
A fast boundary element method for the analysis of three-dimensional solids with cracks and adhesively bonded piezoelectric patches, used as strain sensors, is presented. The piezoelectric sensors, as well as the adhesive layer, are modeled using a 3D state-space finite element approach. The piezoelectric patch model is formulated taking into account the full electro-mechanical coupling and embodying the suitable boundary conditions and it is eventually expressed in terms of the interface variables, to allow a straightforward coupling with the underlying host structure, which is modeled through a 3D dual boundary element method, for accurate analysis of cracks. The technique is computationa…
HIGH-PRECISION MONTE CARLO DETERMINATION OF α/ν IN THE 3D CLASSICAL HEISENBERG MODEL
1994
To study the role of topological defects in the three-dimensional classical Heisenberg model we have simulated this model on simple cubic lattices of size up to 803, using the single-cluster Monte Carlo update. Analysing the specific-heat data of these simulations, we obtain a very accurate estimate for the ratio of the specific-heat exponent with the correlation-length exponent, α/ν, from a usual finite-size scaling analysis at the critical coupling Kc. Moreover, by fitting the energy at Kc, we reduce the error estimates by another factor of two, and get a value of α/ν, which is comparable in accuracy to best field theoretic estimates.
Reconfigurable waveguides defined by selective fluid filling in two-dimensional phononic metaplates
2022
Abstract We investigate two-dimensional phononic metaplates consisting of a periodic array of cups on a thin epoxy plate that is perforated with periodic cross holes. The cups are individually filled with water or remain empty, in view of creating reconfigurable phononic waveguides. Phononic band gaps exist for empty or filled epoxy cups, leading to waveguides defined with either positive or negative contrast. Straight and 90° bent waveguides are considered experimentally. Lamb waves are excited by a piezoelectric patch glued onto the metaplate and are imaged using a scanning laser vibrometer. Experimental results are compared to a three-dimensional finite element model of fluid–structure i…
Exploiting Cryo-EM Structural Information and All-Atom Simulations To Decrypt the Molecular Mechanism of Splicing Modulators.
2019
Splicing modulators (SMs) pladienolides, herboxidienes, and spliceostatins exert their antitumor activity by altering the ability of SF3B1 and PHF5A proteins, components of SF3b splicing factor, to recognize distinct intron branching point sequences, thus finely calibrating constitutive/alternative/aberrant splicing of pre-mRNA. Here, by exploiting structural information obtained from cryo-EM data, and by performing multiple μs-long all-atom simulations of SF3b in apo form and in complex with selected SMs, we disclose how these latter seep into the narrow slit at the SF3B1/PHF5A protein interface. This locks the intrinsic open/closed conformational transitions of SFB1's solenoidal structure…