952 resultados para Constraint stabilization
Resumo:
In the framework of multibody dynamics, the path motion constraint enforces that a body follows a predefined curve being its rotations with respect to the curve moving frame also prescribed. The kinematic constraint formulation requires the evaluation of the fourth derivative of the curve with respect to its arc length. Regardless of the fact that higher order polynomials lead to unwanted curve oscillations, at least a fifth order polynomials is required to formulate this constraint. From the point of view of geometric control lower order polynomials are preferred. This work shows that for multibody dynamic formulations with dependent coordinates the use of cubic polynomials is possible, being the dynamic response similar to that obtained with higher order polynomials. The stabilization of the equations of motion, always required to control the constraint violations during long analysis periods due to the inherent numerical errors of the integration process, is enough to correct the error introduced by using a lower order polynomial interpolation and thus forfeiting the analytical requirement for higher order polynomials.
Resumo:
A költségvetési korlát megkeményítése nem egyforma mértékben ment végbe minden posztszocialista gazdaságban. Egyes országokban messzire jutottak ebben a tekintetben, másokban viszont alig változott az indulóállapot. A tanulmány áttekinti a költségvetési korlát puhaságának különböző megnyilvánulásait: az állami támogatásokat, a puha adózást, a nem teljesítő bankkölcsönöket, a vállalatközi tartozások felgyülemlését és a kifizetetlen béreket. A jelenséget sokféle tényező okozza, amelyek többnyire együttesen jelentkeznek. Az állami tulajdon fenntartása kedvez a puha költségvetési szindróma megrögződésének, a privatizálás elősegíti a keményítést, de nem elégséges feltétele a kemény korlát érvényesítésének. Ehhez megfelelő politikai, jogi és gazdasági környezetet kell céltudatosan kialakítani. A posztszocialista átmenet kezdetén sokan azt hitték, hogy a hatékony piacgazdaság létrehozásához elegendő lesz megvalósítani a liberalizáció, privatizáció és stabilizáció "szentháromságát". Mára már kiderült, hogy a költségvetési korlát megkeményítése az említett három feladattal egyenrangúan fontos. Ahol ez nem valósul meg (például Oroszország), ott a privatizáció nem hozza meg a várt eredményt. ___________________ The budget constraint has not hardened to equal degrees in the various post-socialist countries. In some of them, a great deal has been done in this respect, while in others there has been hardly any change from the initial state. This study surveys the typical manifestations of softness of the budget constraint, such as state subsidies, soft taxation, non-performing loans, the accumulation of trade arrears between firms, and the build-up of wage arrears. Softness of the budget constraint is caused by several factors that tend to act in combination. Thus retention of state ownership helps to preserve the soft budget-constraint syndrome, while privatization encourages the budget constraint to harden, although it does not form a sufficient condition for it to happen. Purposeful development of the requisite political, legal and economic conditions is also required. It was widely maintained at the outset of the post-socialist transition that the 'Holy Trinity' of liberalization, privatization and stabilization would suffice to produce an efficient market economy. Since then, it has become clear that hardening the budget constraint needs to be given equal priority with these. Otherwise, the effects of privatization will fall short of expectations, as they have in Russia, for example.
Resumo:
Hsp90 is a molecular chaperone essential for cell viability in eukaryotes that is associated with the maturation of proteins involved in important cell functions and implicated in the stabilization of the tumor phenotype of various cancers, making this chaperone a notably interesting therapeutic target. Celastrol is a plant-derived pentacyclic triterpenoid compound with potent antioxidant, anti-inflammatory and anticancer activities; however, celastrol's action mode is still elusive. In this work, we investigated the effect of celastrol on the conformational and functional aspects of Hsp90α. Interestingly, celastrol appeared to target Hsp90α directly as the compound induced the oligomerization of the chaperone via the C-terminal domain as demonstrated by experiments using a deletion mutant. The nature of the oligomers was investigated by biophysical tools demonstrating that a two-fold excess of celastrol induced the formation of a decameric Hsp90α bound throughout the C-terminal domain. When bound, celastrol destabilized the C-terminal domain. Surprisingly, standard chaperone functional investigations demonstrated that neither the in vitro chaperone activity of protecting against aggregation nor the ability to bind a TPR co-chaperone, which binds to the C-terminus of Hsp90α, were affected by celastrol. Celastrol interferes with specific biological functions of Hsp90α. Our results suggest a model in which celastrol binds directly to the C-terminal domain of Hsp90α causing oligomerization. However, the ability to protect against protein aggregation (supported by our results) and to bind to TPR co-chaperones are not affected by celastrol. Therefore celastrol may act primarily by inducing specific oligomerization that affects some, but not all, of the functions of Hsp90α. To the best of our knowledge, this study is the first work to use multiple probes to investigate the effect that celastrol has on the stability and oligomerization of Hsp90α and on the binding of this chaperone to Tom70. This work provides a novel mechanism by which celastrol binds Hsp90α.
Resumo:
The androgynophore column, a distinctive floral feature in passion flowers, is strongly crooked or bent in many Passiflora species pollinated by bats. This is a floral feature that facilitates the adaptation to bat pollination. Crooking or bending of plant organs are generally caused by environmental stimulus (e.g. mechanical barriers) and might involve the differential distribution of auxin. Our aim was to study the role of the perianth organs and the effect of auxin in bending of the androgynophore of the bat-pollinated species Passiflora mucronata. Morpho-anatomical characterisation of the androgynophore, including measurements of curvature angles and cell sizes both at the dorsal (convex) and ventral (concave) sides of the androgynophore, was performed on control flowers, flowers from which perianth organs were partially removed and flowers treated either with auxin (2,4-dichlorophenoxyacetic acid; 2,4-D) or with an inhibitor of auxin polar transport (naphthylphthalamic acid; NPA). Asymmetric growth of the androgynophore column, leading to bending, occurs at a late stage of flower development. Removing the physical constraint exerted by perianth organs or treatment with NPA significantly reduced androgynophore bending. Additionally, the androgynophores of plants treated with 2,4-D were more curved when compared to controls. There was a larger cellular expansion at the dorsal side of the androgynophores of plants treated with 2,4-D and in both sides of the androgynophores of plants treated with NPA. This study suggests that the physical constraint exerted by perianth and auxin redistribution promotes androgynophore bending in P. mucronata and might be related to the evolution of chiropterophily in the genus Passiflora.
Resumo:
This study assessed the effects of haptic information on the postural control systems of individuals with intellectual disabilities (ID), through the use of a nonrigid tool that we call the ""anchor system"" (e.g., ropes attached to graduated weights that rest on the floor). Eleven participants with ID were asked to stand, blindfolded, on a balance beam placed at two heights (10 and 20 cm), for 30 s, while using the anchor system at two weights. The lighter anchor weight appeared to improve the individuals' balance in contrast to a control task condition; therefore, we concluded that haptic sensitivity was more significant in helping to orient the body than was the anchor's mechanical support alone.
Resumo:
Based on high-resolution spectra obtained with the MIKE spectrograph on the Magellan telescopes, we present detailed elemental abundances for 20 red giant stars in the outer Galactic disk, located at Galactocentric distances between 9 and 13 kpc. The outer disk sample is complemented with samples of red giants from the inner Galactic disk and the solar neighborhood, analyzed using identical methods. For Galactocentric distances beyond 10 kpc, we only find chemical patterns associated with the local thin disk, even for stars far above the Galactic plane. Our results show that the relative densities of the thick and thin disks are dramatically different from the solar neighborhood, and we therefore suggest that the radial scale length of the thick disk is much shorter than that of the thin disk. We make a first estimate of the thick disk scale length of L(thick) = 2.0 kpc, assuming L(thin) = 3.8 kpc for the thin disk. We suggest that radial migration may explain the lack of radial age, metallicity, and abundance gradients in the thick disk, possibly also explaining the link between the thick disk and the metal-poor bulge.
Resumo:
The electrochemical polymerization of aniline in a hydrophobic room-temperature ionic liquid and the spectroelectrochemical characterization of the formed film are presented. The polymerization occurs without the presence of acid in 1-butyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide (BMMITFSI), leading to a very stable electroactive material where no degradation was observed even at high applied potentials. Both in situ UV-Vis and Raman spectroscopic studies provided evidence for the stabilization of pernigraniline salt at high oxidation potentials and that this polyaniline state is the conducting form, as was corroborated by in situ resistance measurements. These data are indicative that low conductivity is not an intrinsic property of pernigraniline salt and this point must be reconsidered.
Resumo:
In order to evaluate the effects of uncertainty about direction of mechanical perturbation and supra-postural task constraint on postural control young adults had their upright stance perturbed while holding a tray in a horizontal position Stance was perturbed by moving forward or backward a supporting platform contrasting situations of certainty versus uncertainty of direction of displacement Increased constraint on postural stability was Imposed by a supra-postural task of equilibrating a cylinder on the tray Performance was assessed through EMG of anterior leg muscles angular displacement of the main Joints involved in the postural reactions and displacement of the tray Results showed that both certainty on the direction of perturbation and Increased supra-postural task constraint led to decreased angular displacement of the knee and the hip Furthermore combination of certainty and high supra-postural task constraint produced shorter latency of muscular activation Such postural responses were paralleled by decreased displacement of the tray Thesi results suggest a functional integration between the tasks with central set priming reactive postural responses from contextual cues and Increased stability demand (C) 2010 Elsevier B V All rights reserved
Resumo:
Microbial lipase preparations from Thermomyces lanuginosus (TLL) and Pseudomonas fluorescens (PFL) were immobilized by multipoint covalent attachment on Toyopearl AF-amino-650M resin and the most active and thermal stable derivatives used to catalyze the transesterificanon reaction of babassu and palm oils with ethanol in solvent-free media For this different activating agents mainly glutaraldehyde glycidol and epichlorohydrin were used and immobilization parameters were estimated based on the hydrolysis of olive oil emulsion and butyl butyrate synthesis ILL immobilized on glyoxyl-resin allowed obtaining derivatives with the highest hydrolytic activity (HA(der)) and thermal stability between 27 and 31 times more stable than the soluble lipase Although PFL derivatives were found to be less active and thermally stables similar formation of butyl butyrate concentrations were found for both ILL and PFL derivatives The highest conversion into biodiesel was found in the transesterification of palm oil catalyzed by both ILL and PFL glyoxyl-derivatives (c) 2010 Elsevier B V All rights reserved
Resumo:
This paper analyses the presence of financial constraint in the investment decisions of 367 Brazilian firms from 1997 to 2004, using a Bayesian econometric model with group-varying parameters. The motivation for this paper is the use of clustering techniques to group firms in a totally endogenous form. In order to classify the firms we used a hybrid clustering method, that is, hierarchical and non-hierarchical clustering techniques jointly. To estimate the parameters a Bayesian approach was considered. Prior distributions were assumed for the parameters, classifying the model in random or fixed effects. Ordinate predictive density criterion was used to select the model providing a better prediction. We tested thirty models and the better prediction considers the presence of 2 groups in the sample, assuming the fixed effect model with a Student t distribution with 20 degrees of freedom for the error. The results indicate robustness in the identification of financial constraint when the firms are classified by the clustering techniques. (C) 2010 Elsevier B.V. All rights reserved.
Resumo:
The cyanobacterial population in the Cajati waste stabilization pond system (WSP) from Sao Paulo State, Brazil was assessed by cell isolation and direct microscope counting techniques. Ten strains, belonging to five genera (Synechococcus, Merismopedia, Leptolyngbya, Limnothrix, and Nostoc), were isolated and identified by morphological and molecular analyses. Morphological identification of the isolated strains was congruent with their phylogenetic analyses based on 16S rDNA gene sequences. Six cyanobacterial genera (Synechocystis, Aphanocapsa, Merismopedia, Lyngbya, Phormidium, and Pseudanabaena) were identified by direct microscope inspection. Both techniques were complementary, since, of the six genera identified by direct microscopic inspection, only Merismopedia was isolated, and the four other isolated genera were not detected by direct inspection. Direct microscope counting of preserved cells showed that cyanobacteria were the dominant members (> 90%) of the phytoplankton community during both periods evaluated (summer and autumn). ELISA tests specific for hepatotoxicmicrocystins gave positive results for six strains (Synechococcus CENA108, Merismopedia CENA106, Leptolyngbya CENA103, Leptolyngbya CENA112, Limnothrix CENA109, and Limnothrix CENA110), and for wastewater samples collected from raw influent (3.70 mu g microcystins/l) and treated effluent (3.74 mu g microcystins/l) in summer. Our findings indicate that toxic cyanobacteria in WSP systems are of concern, since the treated effluent containing cyanotoxins will be discharged into rivers, irrigation channels, estuaries, or reservoirs, and can affect human and animal health.
Resumo:
Urban rainfall-runoff residuals contain metals such as Cr, Zn, Cu, As, Pb and Cd and are thus reasonable candidates for treatment using Portland cement-based solidification-stabilization (S/S). This research is a study of S/S of urban storm water runoff solid residuals in Portland cement with quicklime and sodium bentonite additives. The solidified residuals were analyzed after 28 days of hydration time using X-ray powder diffraction (XRD) and solid-state Si-29 nuclear magnetic resonance (NMR) spectroscopy. X-ray diffraction (XRD) results indicate that the main cement hydration products are ettringite, calcium hydroxide and hydrated calcium silicates. Zinc hydroxide and lead and zinc silicates are also present due to the reactions of the waste compounds with the cement and its hydration products. Si-29 NMR analysis shows that the coarse fraction of the waste apparently does not interfere with cement hydration, but the fine fraction retards silica polymerization.
Resumo:
Diminished balance ability poses a serious health risk due to the increased likelihood of falling, and impaired postural stability is significantly associated with blindness and poor vision. Noise stimulation (by improving the detection of sub-threshold somatosensory information) and tactile supplementation (i.e. additional haptic information provided by an external contact surface) have been shown to improve the performance of the postural control system. Moreover, vibratory noise added to the source of tactile supplementation (e.g. applied to a surface that the fingertip touches) has been shown to enhance balance stability more effectively than tactile supplementation alone. In view of the above findings, in addition to the well established consensus that blind subjects show superior abilities in the use of tactile information, we hypothesized that blind subjects may take extra benefits from the vibratory noise added to the tactile supplementation and hence show greater improvements in postural stability than those observed for sighted subjects. If confirmed, this hypothesis may lay the foundation for the development of noise-based assistive devices (e.g. canes, walking sticks) for improving somatosensation and hence prevent falls in blind individuals. (C) 2011 Elsevier Ltd. All rights reserved.
Resumo:
The amylase from Neurospora crassa is an interesting enzyme, having higher stability than amylase from Aspergillus oryzea under a broad range of pH values. Moreover, the N. crassa enzyme may be immobilized on different supports with good retention of enzyme activity. The best stabilizations were achieved using Eupergit C 250 L or glyoxyl agarose, with which the enzyme remained fully active at 60C for 24 h while the soluble enzyme remained about 17%. The glyoxyl agarose immobilized enzyme had high thermostability, high optimal temperature (65C) and broad pH/activity profile, suggesting that this enzyme has potential for food and industrial applications for starch modification.
Resumo:
In this study the effects of spray-drying conditions on the retention of enzyme activity of lipase produced by the endophytic fungus Cercospora kikuchii have been investigated. Drying runs were carried out in a bench-top spray dryer with a concurrent flow regime. The influence of the variables inlet temperature of drying gas, Tgi (86.4 to 153.6 degrees C); mass flow rate of the enzymatic extract fed to the dryer, Ws (2.63 to 9.36g/min); and concentration of the drying adjuvant added to the extract, ADJ (1.95 to 12.05%), on the spray-drying performance and on product quality was evaluated through experimental planning and regression analysis. The use of maltodextrin, as a stabilizing agent, slightly improved the retention of enzyme activity compared to -cyclodextrin. Statistical optimization of the experimental results allowed the determination of the processing conditions that maximized the retention of the enzymatic activity (RAE), namely, concentration of drying adjuvants of 12.05%, inlet temperature of the drying gas of 153.6 degrees C, and flow rate of the enzymatic extract fed to the dryer of 9.36g/min for the both drying adjuvants investigated.