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411.
Pekka Mattssoin Tlmo Korpela Sari Paavilainen Mauri Mäkelä 《Applied biochemistry and biotechnology》1991,30(1):17-28
Improved formation of cyclodextrins (CDs) from starch in ethanolic solutions byBacillus circulans var alkalophilus cyclomaltodextrin glucanotransferase was studied. The β- and γ-CD yields increased and α-CD yield gradually decreased as
the ethanol concentration was raised. The ethanol concentration required for maximal CD yield depended essentially on starch
concentration. The ethanol's effect was pronounced at high starch concentrations. For example, with 30% (w/v) starch, the
CD yield was 2.4-fold (146.5 g/L) in the presence of 15% (v/v) ethanol. The effect of dimethylsulfoxide on the formation of
CDs was similar to that of ethanol. The disintegration of β- and γ-CDs were narrowly interdependent on the formation of a
α-CD and malto-sugars. The amount of reducing sugars decreased from a dextrose equivalent value of roughly 7.5 to 4.5 in the
presence of ethanol at starch concentrations 1-30% (w/v). The effect of ethanol on starchy materials from various sources
was similar. It was concluded that ethanol retards the decomposition of β-CD by a general mechanism involving a decreased
activity of water. 相似文献
412.
413.
Baldo-Ceolin M. Benetti P. Bitter T. Bobisut F. Calligarich E. Dolfini R. Dubbers D. El-Muzeini P. Genoni M. Gibin D. Gigli Berzolari A. Gobrecht K. Guglielmi A. Last J. Laveder M. Lippert W. Mattioli F. Mauri F. Mezzetto M. Montanari C. Piazzoli A. Puglierin G. Rappoldi A. Raselli G. L. Scannicchio D. Sconza A. Vascon M. Visentin L. 《Zeitschrift fur Physik C Particles and Fields》1994,63(3):409-416
414.
415.
Aurelio Amodei Jr Luís Henrique M. K. Costa Otto Carlos M. B. Duarte 《International Journal of Communication Systems》2008,21(7):695-711
In this paper we propose a new medium access mechanism for HomePNAv2 and HomePNAv3 standards. This mechanism uses a priority aggregation mechanism to avoid collisions, increasing these protocols throughput. Furthermore, this mechanism does not require modifying standards, since it can be implemented over their actual MAC sublayers. Simulation results show that the proposed mechanism is able to increase the throughput up to 44% for HomePNAv2 and 36% for HomePNAv3. Moreover, we also show how this mechanism affects network delay, analyzing average delay and jitter for all protocols presented. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
416.
Larcher L. Padovani A. Pavan P. Fantini P. Calderoni A. Mauri A. Benvenuti A. 《Electron Device Letters, IEEE》2008,29(10):1152-1154
In this letter, we present a compact model of NAND flash memory strings for circuit simulation purposes. This model is modular and easy to be implemented, and its parameters can be extracted through a simple procedure. It allows accurate simulation of NAND flash memories with a limited computational effort, taking into account capacitive coupling effects which will become extremely important in future technology generations. This model is a very valuable tool for IC designers to optimize NVM circuits, particularly in multilevel applications. 相似文献
417.
Roberto Alvarado Cárdenas Francisco Javier Carrión Viramontes Aurelio Domínguez González Gilberto Herrera Ruiz 《Nonlinear dynamics》2008,52(4):347-359
Computational models are increasingly being used for the dynamic analysis of structures with nonlinear or uncertain behavior,
such as cables in stayed bridges, which nowadays are progressively more used as an alternative for long span and slim structures.
In this work, a 3D nonlinear model is described to evaluate the wind dynamic effects on cables for this type of bridges under
different scenarios, but also for health monitoring and structural simulation to guarantee performance, evaluate load capacity
and estimate life prediction. Fatigue is one of the most relevant and complex failure causes in highway bridges, particularly
on the anchorage elements of the cables in stayed bridges; where dampers may be used to minimize the dynamic behavior of the
structure and reduce fatigue damage. With this nonlinear simulation model, different damper locations and configurations are
evaluated to find the optimal position. A feasibility function is used as a weighting function to take into account the damper’s
size and design. Analysis is particularly focused for a real cable stayed bridge in the state of Veracruz in México.
Although the geometry, the forces and the stresses on cable structures are a challenge, even for structural specialists, the
results from this work using the proposed 3D nonlinear model showed to be accurate for the simulation of many different wind
scenarios, and damper’s location and orientations. Finally, the feasibility weighting function enabled the geometrical limitations
to estimate the best location of a damper system to minimize the risk for fatigue failure. 相似文献
418.
Tetko IV Gasteiger J Todeschini R Mauri A Livingstone D Ertl P Palyulin VA Radchenko EV Zefirov NS Makarenko AS Tanchuk VY Prokopenko VV 《Journal of computer-aided molecular design》2005,19(6):453-463
Internet technology offers an excellent opportunity for the development of tools by the cooperative effort of various groups
and institutions. We have developed a multi-platform software system, Virtual Computational Chemistry Laboratory, http://www.vcclab.org,
allowing the computational chemist to perform a comprehensive series of molecular indices/properties calculations and data
analysis. The implemented software is based on a three-tier architecture that is one of the standard technologies to provide
client-server services on the Internet. The developed software includes several popular programs, including the indices generation
program, DRAGON, a 3D structure generator, CORINA, a program to predict lipophilicity and aqueous solubility of chemicals,
ALOGPS and others. All these programs are running at the host institutes located in five countries over Europe. In this article
we review the main features and statistics of the developed system that can be used as a prototype for academic and industry
models. 相似文献
419.
This paper is concerned with the three-dimensional (3-D) reconstruction of coronary vessel centerlines and with how distortion of X-ray angiographic images affects it. Angiographies suffer from pincushion and other geometrical distortions, caused by the peripheral concavity of the image intensifier (II) and the nonlinearity of electronic acquisition devices. In routine clinical practice, where a field-of-view (FOV) of 17-23 cm is commonly used for the acquisition of coronary vessels, this distortion introduces a positional error of up to 7 pixels for an image matrix size of 512 x 512 and an FOV of 17 cm. This error increases with the size of the FOV. Geometrical distortions have a significant effect on the validity of the 3-D reconstruction of vessels from these images. We show how this effect can be reduced by integrating a predictive model of (un)distortion into the biplane snakes formulation for 3-D reconstruction. First, we prove that the distortion can be accurately modeled using a polynomial for each view. Also, we show that the estimated polynomial is independent of focal length, but not of changes in anatomical angles, as the II is influenced by the earth's magnetic field. Thus, we decompose the polynomial into two components: the steady and the orientation-dependent component. We determine the optimal polynomial degree for each component, which is empirically determined to be five for the steady component and three for the orientation-dependent component. This fact simplifies the prediction of the orientation-dependent polynomial, since the number of polynomial coefficients to be predicted is lower. The integration of this model into the biplane snakes formulation enables us to avoid image unwarping, which deteriorates image quality and therefore complicates vessel centerline feature extraction. Moreover, we improve the biplane snake behavior when dealing with wavy vessels, by means of using generalized gradient vector flow. Our experiments show that the proposed methods in this paper decrease up to 88% the reconstruction error obtained when geometrical distortion effects are ignored. Tests on imaged phantoms and real cardiac images are presented as well. 相似文献
420.
el Haskouri J Ortiz de Zárate D Guillem C Latorre J Caldés M Beltrán A Beltrán D Descalzo AB Rodríguez-López G Martínez-Máñez R Marcos MD Amorós P 《Chemical communications (Cambridge, England)》2002,(4):330-331
Porous pure and doped silicas with pore sizes at two length scales (meso/macroporous) have been prepared and shaped both as powders and monoliths through a one-pot surfactant assisted procedure by using a simple template agent and starting from atrane complexes as inorganic precursors. 相似文献