Simulació de processos de combustió de sòlids prims

L'objecte del projecte consisteix en investigar les capacitats del programari dedinàmica de fluids computacional FLUENT per simular processos transitoris de combustióquan es cremen sòlids. Com el programari FLUENT no incorpora cap mòdul de combustióde sòlids prims, s'hauran de realitzar les funcions d'usuari adients per tal d'incorporar lesequacions i les condicions de contorns que són rellevants en aquests tipus de problemes. Elmodel resultant es validarà amb dades experimentals per a la combustió de fulls decel•lulosa en flames bidimensionals. També es durà a terme una anàlisi de sensibilitat de lasolució variant els paràmetres del model. En funció dels resultats de la validació es durà aterme una extensió del model per a situacions tridimensionals

Modelització i simulació del motor d'inducció en règim transitori amb PSIM

El present treball pretén modelitzar i simular el motor d’inducció trifàsic en règim transitori amb PSIM 6.0 Demo(la versió del programa que s’utilitza actualment a l’Escola Politècnica Superior de la UdG), però també s’estudia el model en règim permanent, per tal de comparar a nivell teòric els resultats dels dos règims. Primer cal entendre i implementar el model del motor d’inducció, i així obtenir l'esquema equivalent en règim transitori, per després poder-lo simular. Abans de dur a terme la simulació, cal obtenir els paràmetres del circuit equivalent del motor real per introduir-los al programa informàtic, amb la finalitat de tenir precisió en les respostes. Aquests valors s’obtindran mitjançant assajos necessaris al laboratori. Posteriorment, es fan simulacions i pràctiques reals amb el motor treballen en diferents condicions per veure el seu comportament, i així poder comparar els resultats de la simulació amb els valors reals. També s’implementa un estudi de la influencia dels paràmetres interns en el funcionament del motor. Així es podrà visualitzar i comparar les respostes de diferents variables en cadascunes de les simulacions que es duguin a terme. Finalment, seria interessant la introducció de la màquina d’inducció trifàsica actuant com a generador en la simulació.Aquest és un estudi en el qual se simula la màquina d'inducció trifàsic en règim transitori i en règim permanent mitjançant l'ús del PSIM, que és el programa informàtic de simulació

Dimensionat de la instal·lació de climatització d'un edifici de vivendes mitjançant el programa de simulació HvacCad : estudi comparatiu amb els mètodes tradicionals de càlcul

L’objecte d’aquest treball és fer una posta a punt d’un programa de simulació. En el nostre cas el programa s’anomena HvacCad. A partir d’aquest programa trobarem les càrregues tèrmiques d’un edifici de vivendes exemple tant per a l’ hivern com a l’estiu. Paral•lelament a aquests càlculs farem els mateixos però amb un full de càlcul convencional, anomenat Aguilar, així podrem comparar els resultats obtinguts. No realitzarem el càlcul de la instal•lació de climatització, només trobarem la potència màxima dels aparells

Ab initio absorption spectrum of NiO combining molecular dynamics with the embedded cluster approach in a discrete reaction field

We developed a procedure that combines three complementary computational methodologies to improve the theoretical description of the electronic structure of nickel oxide. The starting point is a Car-Parrinello molecular dynamics simulation to incorporate vibrorotational degrees of freedom into the material model. By means ofcomplete active space self-consistent field second-order perturbation theory (CASPT2) calculations on embedded clusters extracted from the resulting trajectory, we describe localized spectroscopic phenomena on NiO with an efficient treatment of electron correlation. The inclusion of thermal motion into the theoretical description allowsus to study electronic transitions that, otherwise, would be dipole forbidden in the ideal structure and results in a natural reproduction of the band broadening. Moreover, we improved the embedded cluster model by incorporating self-consistently at the complete active space self-consistent field (CASSCF) level a discrete (or direct) reaction field (DRF) in the cluster surroundings. The DRF approach offers an efficient treatment ofelectric response effects of the crystalline embedding to the electronic transitions localized in the cluster. We offer accurate theoretical estimates of the absorption spectrum and the density of states around the Fermi level of NiO, and a comprehensive explanation of the source of the broadening and the relaxation of the charge transferstates due to the adaptation of the environment

A variational approach for calculating Franck-Condon factors including mode-mode anharmonic coupling

We have implemented our new procedure for computing Franck-Condon factors utilizing vibrational configuration interaction based on a vibrational self-consistent field reference. Both Duschinsky rotations and anharmonic three-mode coupling are taken into account. Simulations of the first ionization band of Cl O2 and C4 H4 O (furan) using up to quadruple excitations in treating anharmonicity are reported and analyzed. A developer version of the MIDASCPP code was employed to obtain the required anharmonic vibrational integrals and transition frequencies

Fronts from complex two-dimensional dispersal kernels: theory and application to Reid's paradox

Bimodal dispersal probability distributions with characteristic distances differing by several orders of magnitude have been derived and favorably compared to observations by Nathan [Nature (London) 418, 409 (2002)]. For such bimodal kernels, we show that two-dimensional molecular dynamics computer simulations are unable to yield accurate front speeds. Analytically, the usual continuous-space random walks (CSRWs) are applied to two dimensions. We also introduce discrete-space random walks and use them to check the CSRW results (because of the inefficiency of the numerical simulations). The physical results reported are shown to predict front speeds high enough to possibly explain Reid's paradox of rapid tree migration. We also show that, for a time-ordered evolution equation, fronts are always slower in two dimensions than in one dimension and that this difference is important both for unimodal and for bimodal kernels

Spread spectrum magnetic resonance imaging.

We propose a novel compressed sensing technique to accelerate the magnetic resonance imaging (MRI) acquisition process. The method, coined spread spectrum MRI or simply s(2)MRI, consists of premodulating the signal of interest by a linear chirp before random k-space under-sampling, and then reconstructing the signal with nonlinear algorithms that promote sparsity. The effectiveness of the procedure is theoretically underpinned by the optimization of the coherence between the sparsity and sensing bases. The proposed technique is thoroughly studied by means of numerical simulations, as well as phantom and in vivo experiments on a 7T scanner. Our results suggest that s(2)MRI performs better than state-of-the-art variable density k-space under-sampling approaches.

Expanding molecular modeling and design tools to non-natural sidechains.

Protein-protein interactions encode the wiring diagram of cellular signaling pathways and their deregulations underlie a variety of diseases, such as cancer. Inhibiting protein-protein interactions with peptide derivatives is a promising way to develop new biological and therapeutic tools. Here, we develop a general framework to computationally handle hundreds of non-natural amino acid sidechains and predict the effect of inserting them into peptides or proteins. We first generate all structural files (pdb and mol2), as well as parameters and topologies for standard molecular mechanics software (CHARMM and Gromacs). Accurate predictions of rotamer probabilities are provided using a novel combined knowledge and physics based strategy. Non-natural sidechains are useful to increase peptide ligand binding affinity. Our results obtained on non-natural mutants of a BCL9 peptide targeting beta-catenin show very good correlation between predicted and experimental binding free-energies, indicating that such predictions can be used to design new inhibitors. Data generated in this work, as well as PyMOL and UCSF Chimera plug-ins for user-friendly visualization of non-natural sidechains, are all available at http://www.swisssidechain.ch. Our results enable researchers to rapidly and efficiently work with hundreds of non-natural sidechains.

The population genetics of clonal and partially clonal diploids.

The consequences of variable rates of clonal reproduction on the population genetics of neutral markers are explored in diploid organisms within a subdivided population (island model). We use both analytical and stochastic simulation approaches. High rates of clonal reproduction will positively affect heterozygosity. As a consequence, nearly twice as many alleles per locus can be maintained and population differentiation estimated as F(ST) value is strongly decreased in purely clonal populations as compared to purely sexual ones. With increasing clonal reproduction, effective population size first slowly increases and then points toward extreme values when the reproductive system tends toward strict clonality. This reflects the fact that polymorphism is protected within individuals due to fixed heterozygosity. Contrarily, genotypic diversity smoothly decreases with increasing rates of clonal reproduction. Asexual populations thus maintain higher genetic diversity at each single locus but a lower number of different genotypes. Mixed clonal/sexual reproduction is nearly indistinguishable from strict sexual reproduction as long as the proportion of clonal reproduction is not strongly predominant for all quantities investigated, except for genotypic diversities (both at individual loci and over multiple loci).

SIMULIT : manuel de l'utilisateur

SIMULIT est un programme permettant la simulation de l'occupation des lits des hôpitaux de soins aigus. La mise en oeuvre de SIMULIT et des programmes annexes requiert de l'utilisateur qu'il sache créer et modifier un fichier à l'aide d'un éditeur, et lancer l'exécution d'un programme sur la machine dont il dispose. Le schéma général de la mise en oeuvre se trouve à l'annexe 1 de ce cahier.

Groupes diagnostiques utilisés sur SIMULIT 13

La nomenclature des diagnostics est celle de la Classification internationale des maladies (9e révision), utilisée par la Statistique médicale VESKA depuis 1980. Les trois premiers chiffres du code ont été utilisés; seul le premier diagnostic a été retenu.

Quantification of brain glycogen concentration and turnover through localized 13C NMR of both the C1 and C6 resonances.

We have recently shown that at isotopic steady state (13)C NMR can provide a direct measurement of glycogen concentration changes, but that the turnover of glycogen was not accessible with this protocol. The aim of the present study was to design, implement and apply a novel dual-tracer infusion protocol to simultaneously measure glycogen concentration and turnover. After reaching isotopic steady state for glycogen C1 using [1-(13)C] glucose administration, [1,6-(13)C(2)] glucose was infused such that isotopic steady state was maintained at the C1 position, but the C6 position reflected (13)C label incorporation. To overcome the large chemical shift displacement error between the C1 and C6 resonances of glycogen, we implemented 2D gradient based localization using the Fourier series window approach, in conjunction with time-domain analysis of the resulting FIDs using jMRUI. The glycogen concentration of 5.1 +/- 1.6 mM measured from the C1 position was in excellent agreement with concomitant biochemical determinations. Glycogen turnover measured from the rate of label incorporation into the C6 position of glycogen in the alpha-chloralose anesthetized rat was 0.7 micromol/g/h.

The activation process of the alpha1B-adrenergic receptor: potential role of protonation and hydrophobicity of a highly conserved aspartate.

In this study, a quantitative approach was used to investigate the role of D142, which belongs to the highly conserved E/DRY sequence, in the activation process of the alpha1B-adrenergic receptor (alpha1B-AR). Experimental and computer-simulated mutagenesis were performed by substituting all possible natural amino acids at the D142 site. The resulting congeneric set of proteins together with the finding that all the receptor mutants show various levels of constitutive (agonist-independent) activity enabled us to quantitatively analyze the relationships between structural/dynamic features and the extent of constitutive activity. Our results suggest that the hydrophobic/hydrophilic character of D142, which could be regulated by protonation/deprotonation of this residue, is an important modulator of the transition between the inactive (R) and active (R*) state of the alpha1B-AR. Our study represents an example of quantitative structure-activity relationship analysis of the activation process of a G protein-coupled receptor.

Relaxation times of non-Markovian processes

We consider a general class of non-Markovian processes defined by stochastic differential equations with Ornstein-Uhlenbeck noise. We present a general formalism to evaluate relaxation times associated with correlation functions in the steady state. This formalism is a generalization of a previous approach for Markovian processes. The theoretical results are shown to be in satisfactory agreement both with experimental data for a cubic bistable system and also with a computer simulation of the Stratonovich model. We comment on the dynamical role of the non-Markovianicity in different situations.

Numerical algorithm for Ginzburg-Landau equations with multiplicative noise: Application to domain growth

We consider stochastic partial differential equations with multiplicative noise. We derive an algorithm for the computer simulation of these equations. The algorithm is applied to study domain growth of a model with a conserved order parameter. The numerical results corroborate previous analytical predictions obtained by linear analysis.