951 resultados para force field analysis


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El tema de estudio de esta tesis es el análisis morfológico y cronológico de diez ejemplares emblemáticos de la arquitectura doméstica señorial de la Granada del siglo XVI, analizados en comparación con otros casos de referencia construidos en el mismo período en la propia ciudad, conservados y desaparecidos. También se han tenido en cuenta las principales manifestaciones arquitectónicas de los mayores focos urbanos contemporáneos en el reino de Castilla. El trabajo se ha desarrollado partiendo de la realización de una planimetría precisa y completa de las diez casas documentadas, uniendo al trabajo in situ sobre los datos materiales el estudio de las fuentes de archivo y de la bibliografía especializada existente sobre la materia. El análisis formal de las unidades domésticas ha sido enfocado al estudio tipológico de lo construido, haciendo especial hincapié en las pervivencias andalusíes sobre las cuales los nuevos moradores edificaron o adaptaron sus casas solariegas. En apoyo a las hipótesis presentadas se aporta la documentación arqueológica derivada de las excavaciones realizadas en los solares de las viviendas objeto de análisis, además de los planos de los estados previos a las recientes reformas sufridas por muchos de estos edificios. El análisis comparativo con algunos edificios contemporáneos en los que se ha documentado y estudiado cronológicamente su evolución histórica, ha permitido afianzar las hipótesis de datación y de reconstrucción de la distribución espacial de las fábricas originarias de la época tratada. Los objetivos de la investigación han sido orientados a poner de manifiesto la delicada y compleja transición de la medina nazarí a la ciudad cristiana, tratando también ciertas características multiculturales propias de las técnicas constructivas y de sociedad de la época. Los resultados de este estudio multidisciplinar se han registrado en un mapa de datos creado con el Sistema de Información Geográfico, en el que se han incluido tanto los datos cronológicos como formales, individualizando los ambientes que constituyen las pervivencias medievales y los que se han construido después, aportando sus distintas dataciones. Se ha querido dar respuesta a varios interrogativos: ¿Cómo se adapta la arquitectura castellana al tejido urbano andalusí? ¿Reaprovecha las preexistencias o las elimina en cada momento? ¿De qué modo la ciudad ha ido modificándose hasta configurarse como una ciudad moderna? ¿Cuánto se ha mantenido este patrimonio de casas? ¿Cómo se debería conservar? Se ha tratado de resolver estas cuestiones formulando síntesis gráficas en las que se puede comprender la evolución histórica de las viviendas acontecida a lo largo del siglo XVI, junto con sus transformaciones recientes provocadas por las intervenciones contemporáneas. Asimismo se aporta el estudio de las principales características de las intervenciones acometidas sobre este patrimonio único de viviendas, que por su propia naturaleza es altamente perecedero y necesita que se formulen criterios eficaces y correctos para su mayor conservación. El punto de partida de este trabajo no ha sido solamente el análisis de campo sino también la recopilación y ordenación de los datos procedentes de la bibliografía existente para formular discursos coherentes y precisos sobre la evolución de este tipo de viviendas históricas, cuyos valores son tan expuestos a graves deterioros que su catalogación, documentación y valoración se hacen imprescindibles. Pese a que las diez viviendas incluidas en los capítulos de estudio detallado estén catalogadas en los Planes Especiales de Protección (Albaicín, 1990 y Centro, 2002), sus caracteres formales y sus elementos estructurales y decorativos de valor histórico han sufrido un evidente proceso de expolio o destrucción, hecho grave que esta Tesis quiere reflejar de cara a la deseable futura puesta en valor real de estos edificios así como, indirectamente, de sus ámbitos urbanísticos de pertenencia. ABSTRACT The purpose of this thesis is to study the morphological and chronological characteristics of ten emblematic mansions belonging to the architectural period of the 16th Century in Granada, Spain. These houses are compared with other similar outstanding constructions of the same period that are located in the city, which have either been preserved or disappeared. Also, this study has taken into account the main architectural expressions of greater contemporary urban areas of the Kingdom of Castile. The work carried out began, first of all, by drawing a precise and thorough planimetry of the ten surveyed houses, together with in situ tasks based on physical data, a study of archival data, and the specialized existing bibliography on the subject. The formal analysis of the home units is focused as a typological study of erected buildings, with a special attention on Al Andalus remains over which the new householders constructed or adapted their mansions. The hypotheses brought forward have been supported by the archaeological documentation that had been elaborated during the excavation works of the houses concerned in this study. Moreover, the drawings of the states of the sites, previously to the most recent renovation works many of these buildings have undergone, have been presented. The comparative analysis made with some contemporary buildings, which have been chronologically documented and studied in their historical evolution, has confirmed the dating hypotheses, and that of the reconstruction of the spatial distribution of the original factories the period discussed. The aims of this research have been oriented to bring to light the delicate and complex transition of the town, from the Nasrid period to Christian times. The research has also dealt with some special multicultural characteristics of the constructive techniques, as well as of the society of that period. The results of this multidisciplinary study have been registered on a data map created with the Geographical Information System, which includes both the chronological and formal data. The Medieval settings, and those of later constructions, have been individualised and dated. Several questions have been answered: how the Castilian architecture adapts to the Al Andalus urban design? Have the pre-existing structures been reused or eliminated at each stage? How has the town evolved until becoming a modern city? To which degree this heritage of houses has remained? How should it been preserved? These questions have been approached by means of graphical syntheses in an attempt to bring an understanding of the historical evolution of the houses throughout the 16th Century. But also, this work shows the more recent transformations these structures suffered over the contemporary period. Moreover, there is a study of the main characteristics of interventions over this unique patrimony of housing which by nature is perishable and needs a formulation of correct and efficient criteria for better conservation. The starting point of this work has not only been that of field analysis, but also the gathering and ordering of the existing bibliographical data, in order to formulate coherent and precise statements on the evolution of this type of historical housing. Its treasures are so exposed to severe deterioration that their cataloguing, documentation and appreciation are becoming crucial. Despite the fact that the ten houses considered in the chapters of this detailed study are listed in the special protection plans (Planes Especiales de Protección, Albaicín plan of 1990 and the town centre plan of 2002) their formal characteristics, as well as structural and decorative historical value, have suffered gradual plunders or destruction. This thesis tries to reflect how serious is that matter and the need in the future to give this heritage and the surrounding urban environment, a real value.

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Tumor induced angiogenesis processes including the effect of stochastic motion and branching of blood vessels can be described coupling a (nonlocal in time) integrodifferential kinetic equation of Fokker–Planck type with a diffusion equation for the tumor induced ingiogenic factor. The chemotactic force field depends on the flux of blood vessels through the angiogenic factor. We develop an existence and uniqueness theory for this system under natural assumptions on the initial data. The proof combines the construction of fundamental solutions for associated linearized problems with comparison principles, sharp estimates of the velocity integrals and compactness results for this type of kinetic and parabolic operators

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We have measured experimental adsorption isotherms of water in zeolite LTA4A, and studied the regeneration process by performing subsequent adsorption cycles after degassing at different temperatures. We observed incomplete desorption at low temperatures, and cation rearrangement at successive adsorption cycles. We also developed a new molecular simulation force field able to reproduce experimental adsorption isotherms in the range of temperatures between 273 K and 374 K. Small deviations observed at high pressures are attributed to the change in the water dipole moment at high loadings. The force field correctly describes the preferential adsorption sites of water at different pressures. We tested the influence of the zeolite structure, framework flexibility, and cation mobility when considering adsorption and diffusion of water. Finally, we performed checks on force field transferability between different hydrophilic zeolite types, concluding that classical, non-polarizable water force fields are not transferable.

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Isothermal-isobaric (NPT) molecular dynamics simulation has been performed to investigate the layering behavior and structure of nanoconfined quaternary alkylammoniums in organoclays. This work is focused on systems consisting of two clay layers and a number of alkylammoniums, and involves the use of modified Dreiding force field. The simulated basal spacings of organoclays agree satisfactorily with the experimental results in the literature. The atomic density profiles in the direction normal to the clay surface indicate that the alkyl chains within the interlayer space of montmorillonite exhibit an obvious layering behavior. The headgroups of long alkyl chains are distributed within two layers close to the clay surface, whereas the distributions of methyl and methylene groups are strongly dependent on the alkyl chain length and clay layer charge. Monolayer, bilayer, and pseudo-trilayer structures are found in organoclays modified with single long alkyl chains, which are identical to the structural models based on the measured basal spacings. A pseudo-quadrilayer structure, for the first time to our knowledge, is also identified in organoclays with double long alkyl chains. In the mixture structure of paraffin-type and multilayer, alkyl chains do not lie flat within a single layer but interlace, and also jump to the next layer in pseudo-trilayer as well as next nearest layer in pseudo-quadrilayer.

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To investigate the control mechanisms used in adapting to position-dependent forces, subjects performed 150 horizontal reaching movements over 25 cm in the presence of a position-dependent parabolic force field (PF). The PF acted only over the first 10 cm of the movement. On every fifth trial, a virtual mechanical guide (double wall) constrained subjects to move along a straight-line path between the start and target positions. Its purpose was to register lateral force to track formation of an internal model of the force field, and to look for evidence of possible alternative adaptive strategies. The force field produced a force to the right, which initially caused subjects to deviate in that direction. They reacted by producing deviations to the left, into the force field, as early as the second trial. Further adaptation resulted in rapid exponential reduction of kinematic error in the latter portion of the movement, where the greatest perturbation to the handpath was initially observed, whereas there was little modification of the handpath in the region where the PF was active. Significant force directed to counteract the PF was measured on the first guided trial, and was modified during the first half of the learning set. The total force impulse in the region of the PF increased throughout the learning trials, but it always remained less than that produced by the PF. The force profile did not resemble a mirror image of the PF in that it tended to be more trapezoidal than parabolic in shape. As in previous studies of force-field adaptation, we found that changes in muscle activation involved a general increase in the activity of all muscles, which increased arm stiffness, and selectively-greater increases in the activation of muscles which counteracted the PF. With training, activation was exponentially reduced, albeit more slowly than kinematic error. Progressive changes in kinematics and EMG occurred predominantly in the region of the workspace beyond the force field. We suggest that constraints on muscle mechanics limit the ability of the central nervous system to employ an inverse dynamics model to nullify impulse-like forces by generating mirror-image forces. Consequently, subjects adopted a strategy of slightly overcompensating for the first half of the force field, then allowing the force field to push them in the opposite direction. Muscle activity patterns in the region beyond the boundary of the force field were subsequently adjusted because of the relatively-slow response of the second-order mechanics of muscle impedance to the force impulse.

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Acetohydroxyacid synthase (AHAS; EC 2.2.1.6) catalyzes the first common step in branched-chain amino acid biosynthesis. The enzyme is inhibited by several chemical classes of compounds and this inhibition is the basis of action of the sulfonylurea and imidazolinone herbicides. The commercial sulfonylureas contain a pyrimidine or a triazine ring that is substituted at both meta positions, thus obeying the initial rules proposed by Levitt. Here we assess the activity of 69 monosubstituted sulfonylurea analogs and related compounds as inhibitors of pure recombinant Arabidopsis thaliana AHAS and show that disubstitution is not absolutely essential as exemplified by our novel herbicide, monosulfuron (2-nitro-N-(4'-methyl-pyrimidin-2'-yl) phenyl-sulfonylurea), which has a pyrimidine ring with a single meta substituent. A subset of these compounds was tested for herbicidal activity and it was shown that their effect in vivo correlates well with their potency in vitro as AHAS inhibitors. Three-dimensional quantitative structure-activity relationships were developed using comparative molecular field analysis and comparative molecular similarity indices analysis. For the latter, the best result was obtained when steric, electrostatic, hydrophobic and H-bond acceptor factors were taken into consideration. The resulting fields were mapped on to the published crystal structure of the yeast enzyme and it was shown that the steric and hydrophobic fields are in good agreement with sulfonylurea-AHAS interaction geometry.

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Hydrophobins are small (similar to 100 aa) proteins that have an important role in the growth and development of mycelial fungi. They are surface active and, after secretion by the fungi, self-assemble into amphipathic membranes at hydrophobic/hydrophilic interfaces, reversing the hydrophobicity of the surface. In this study, molecular dynamics simulation techniques have been used to model the process by which a specific class I hydrophobin, SC3, binds to a range of hydrophobic/ hydrophilic interfaces. The structure of SC3 used in this investigation was modeled based on the crystal structure of the class II hydrophobin HFBII using the assumption that the disulfide pairings of the eight conserved cysteine residues are maintained. The proposed model for SC3 in aqueous solution is compact and globular containing primarily P-strand and coil structures. The behavior of this model of SC3 was investigated at an air/water, an oil/water, and a hydrophobic solid/water interface. It was found that SC3 preferentially binds to the interfaces via the loop region between the third and fourth cysteine residues and that binding is associated with an increase in a-helix formation in qualitative agreement with experiment. Based on a combination of the available experiment data and the current simulation studies, we propose a possible model for SC3 self-assembly on a hydrophobic solid/water interface.

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This thesis presents an effective methodology for the generation of a simulation which can be used to increase the understanding of viscous fluid processing equipment and aid in their development, design and optimisation. The Hampden RAPRA Torque Rheometer internal batch twin rotor mixer has been simulated with a view to establishing model accuracies, limitations, practicalities and uses. As this research progressed, via the analyses several 'snap-shot' analysis of several rotor configurations using the commercial code Polyflow, it was evident that the model was of some worth and its predictions are in good agreement with the validation experiments, however, several major restrictions were identified. These included poor element form, high man-hour requirements for the construction of each geometry and the absence of the transient term in these models. All, or at least some, of these limitations apply to the numerous attempts to model internal mixes by other researchers and it was clear that there was no generally accepted methodology to provide a practical three-dimensional model which has been adequately validated. This research, unlike others, presents a full complex three-dimensional, transient, non-isothermal, generalised non-Newtonian simulation with wall slip which overcomes these limitations using unmatched ridding and sliding mesh technology adapted from CFX codes. This method yields good element form and, since only one geometry has to be constructed to represent the entire rotor cycle, is extremely beneficial for detailed flow field analysis when used in conjunction with user defined programmes and automatic geometry parameterisation (AGP), and improves accuracy for investigating equipment design and operation conditions. Model validation has been identified as an area which has been neglected by other researchers in this field, especially for time dependent geometries, and has been rigorously pursued in terms of qualitative and quantitative velocity vector analysis of the isothermal, full fill mixing of generalised non-Newtonian fluids, as well as torque comparison, with a relatively high degree of success. This indicates that CFD models of this type can be accurate and perhaps have not been validated to this extent previously because of the inherent difficulties arising from most real processes.

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Using molecular dynamics (MD) simulations, we explore the structural and dynamical properties of siRNA within the intercalated environment of a Mg:Al 2:1 Layered Double Hydroxide (LDH) nanoparticle. An ab initio force field (Condensed-phase Optimized Molecular Potentials for Atomistic Simulation Studies: COMPASS) is used for the MD simulations of the hybrid organic-inorganic systems. The structure, arrangement, mobility, close contacts and hydrogen bonds associated with the intercalated RNA are examined and contrasted with those of the isolated RNA. Computed powder X-ray diffraction patterns are also compared with related LDH-DNA experiments. As a method of probing whether the intercalated environment approximates the crystalline or rather the aqueous state, we explore the stability of the principle parameters (e.g., the major groove width) that differentiate both A- and A'- crystalline forms of siRNA and contrast this with recent findings for the same siRNA simulated in water. We find the crystalline forms remain structurally distinct when intercalated, whereas this is not the case in water. Implications for the stability of hybrid LDH-RNA systems are discussed.

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This thesis presents an approach to cutting dynamics during turning based upon the mechanism of deformation of work material around the tool nose known as "ploughing". Starting from the shearing process in the cutting zone and accounting for "ploughing", new mathematical models relating turning force components to cutting conditions, tool geometry and tool vibration are developed. These models are developed separately for steady state and for oscillatory turning with new and worn tools. Experimental results are used to determine mathematical functions expressing the parameters introduced by the steady state model in the case of a new tool. The form of these functions are of general validity though their coefficients are dependent on work and tool materials. Good agreement is achieved between experimental and predicted forces. The model is extended on one hand to include different work material by introducing a hardness factor. The model provides good predictions when predicted forces are compared to present and published experimental results. On the other hand, the extension of the ploughing model to taming with a worn edge showed the ability of the model in predicting machining forces during steady state turning with the worn flank of the tool. In the development of the dynamic models, the dynamic turning force equations define the cutting process as being a system for which vibration of the tool tip in the feed direction is the input and measured forces are the output The model takes into account the shear plane oscillation and the cutting configuration variation in response to tool motion. Theoretical expressions of the turning forces are obtained for new and worn cutting edges. The dynamic analysis revealed the interaction between the cutting mechanism and the machine tool structure. The effect of the machine tool and tool post is accounted for by using experimental data of the transfer function of the tool post system. Steady state coefficients are corrected to include the changes in the cutting configuration with tool vibration and are used in the dynamic model. A series of oscillatory cutting tests at various conditions and various tool flank wear levels are carried out and experimental results are compared with model—predicted forces. Good agreement between predictions and experiments were achieved over a wide range of cutting conditions. This research bridges the gap between the analysis of vibration and turning forces in turning. It offers an explicit expression of the dynamic turning force generated during machining and highlights the relationships between tool wear, tool vibration and turning force. Spectral analysis of tool acceleration and turning force components led to define an "Inertance Power Ratio" as a flank wear monitoring factor. A formulation of an on—line flank wear monitoring methodology is presented and shows how the results of the present model can be applied to practical in—process tool wear monitoring in • turning operations.

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Reported accidents involving the poisoning scorpions are still frequent in Brazil, mainly caused by Tityus serrulatus, known as yellow scorpion. Although antivenom sera are produced routinely by various government laboratories, the effectiveness of its use depends on how quickly treatment is initiated and efficiency in the production of antibodies by the immunized animals. In this study, the development of cationic polymeric nanoparticles of poly(lactic acid) aimed to create a modified delivery system for peptides and proteins of T. serrulatus venom, able to enhance the production of serum antibodies against the scorpion toxins. The cationic nanoparticles were obtained by a low energy nanoprecipitation, after study of the parameters’ variations effects over the physicochemical properties of the particles. The surface functionalization of the nanoparticles with the hyperbranched polyethyleneimine was proved by zeta potential analysis and enabled the adsorption by electrostatic interaction of different types of proteins. The protein loading efficiency of 40-80 % to bovine serum albumin (BSA) and 100 % to scorpion venom peptides evaluated by spectrophotometry and polyacrylamide gel electrophoresis confirmed the success of the selected parameters established for obtainment of nanoparticles, produced with size between 100 to 250 nm. The atomic force microscopy analysis and in vitro release showed that the spherical nanoparticles provided a sustained release profile of proteins by diffusion mechanism, demonstrating the potential for application of the nanoparticles in vivo.

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Reported accidents involving the poisoning scorpions are still frequent in Brazil, mainly caused by Tityus serrulatus, known as yellow scorpion. Although antivenom sera are produced routinely by various government laboratories, the effectiveness of its use depends on how quickly treatment is initiated and efficiency in the production of antibodies by the immunized animals. In this study, the development of cationic polymeric nanoparticles of poly(lactic acid) aimed to create a modified delivery system for peptides and proteins of T. serrulatus venom, able to enhance the production of serum antibodies against the scorpion toxins. The cationic nanoparticles were obtained by a low energy nanoprecipitation, after study of the parameters’ variations effects over the physicochemical properties of the particles. The surface functionalization of the nanoparticles with the hyperbranched polyethyleneimine was proved by zeta potential analysis and enabled the adsorption by electrostatic interaction of different types of proteins. The protein loading efficiency of 40-80 % to bovine serum albumin (BSA) and 100 % to scorpion venom peptides evaluated by spectrophotometry and polyacrylamide gel electrophoresis confirmed the success of the selected parameters established for obtainment of nanoparticles, produced with size between 100 to 250 nm. The atomic force microscopy analysis and in vitro release showed that the spherical nanoparticles provided a sustained release profile of proteins by diffusion mechanism, demonstrating the potential for application of the nanoparticles in vivo.

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Objective Primary open angle glaucoma (POAG) is the most common type of glaucoma in Africa. We carried out a study to determine the clinical presentation pattern of patients with primary open angle glaucoma (POAG) at a tertiary hospital in Malawi. Design A cross-sectional study Setting Lions Sight First Eye Hospital—a major referral and teaching state eye hospital in Blantyre, Malawi Subjects Study participants were newly diagnosed POAG patients at specialist eye clinic during study period. Results A total of 60 POAG patients were recruited into the study. The mean age was 58.7 years (SD= 16.6, range 18 - 86). There were more male (44, 73.3%) than female (16, 27.7%) patients. The majority of patients (73%) presented one year after onset of visual symptoms. Twenty-six patients (43%) had unilateral blindness (visual acuity < 3/60; WHO classification), while nine patients (15%) presented with bilateral blindness. A vertical cup-to-disc ratio (CDR) of 0.8 or worse was seen in 92 eyes (79%). The mean intraocular pressure (IOP) reading was 35.5 mmHg (SD 13.30). Of the thirty-three eyes that successfully underwent visual field analysis, very advanced defects were recorded in 12 eyes (36%). Conclusion This study demonstrates delayed presentation and male predominance among POAG patients at a tertiary eye hospital in Malawi. Glaucoma intervention programmes should aim at identifying patients with treatable glaucoma with particular attention to women.

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The solvation of cyano- (CN-) based ionic liquids (ILs) and their capacity to establish hydrogen bonds (H-bonds) with water was studied by means of experimental and computational approaches. Experimentally, water activity data were measured for aqueous solutions of ILs based on 1-butyl-3-methylimidazolium ([BMIM](+)) cation combined with one of the following anions: thiocyanate ([SCN](-)), dicyanamide ([DCA](-)), or tricyanomethanide ([TCM](-)), and of 1-ethyl-3-methylimidazolium tetracyanoborate ([EMIM][TCB]). From the latter data, water activity coefficients were estimated showing that [BMIM][SCN] and [BMIM][DCA], unlike [BMIM][TCM] and [EMIM][TCB], are able to establish favorable interactions with water. Computationally, the conductor like screening model for real solvents (COSMO-RS) was used to estimate the water activity coefficients which compare well with the experimental ones. From the COSMO-RS results, it is suggested that the polarity of each ion composing the ILs has a strong effect on the solvation phenomena. Furthermore, classical molecular dynamics (MD) simulations were performed for obtaining an atomic level picture of the local molecular neighborhood of the different species. From the experimental and computational data it is showed that increasing the number of CN groups in the ILs' anions does not enhance their ability to establish H-bonds with water but decreases their polarities, being [BMIM][DCA] and [BMIM][SCN] the ones presenting higher propensity to interact.