Increasing the throughput of HomePNA

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.     

Modeling nand Flash Memories for IC Design

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.     

Wavelength dispersive X‐ray fluorescence (WDXRF) and chemometric investigation of human hair after cosmetic treatment

Variations in the chemical composition of 63 different human and 6 different synthetic hair samples were investigated using wavelength dispersive X‐ray fluorescence (WDXRF) spectra profiles. To evaluate the effect of cosmetic treatment on the strands, the human hair samples were bleached, but the synthetic ones were not. To better investigate the data, exploratory analyses were calculated using principal component analysis for the WDXRF spectra. Eight normalizations/standardizations were applied in the WDXRF to verify the clustering tendency. Bleaching was tested, because it is one way in which people mask their real hair color. After the data were standardized, an enhancement of the data discrimination was verified. Furthermore, the explained variance was higher in the first principal components. The WDXRF spectra were able to distinguish samples with distinct features, including synthetic, dyed, and straightened hair. The findings of this study hold promise for forensics due to desirable aspects such as nondestructivity and the possibility of a large hair sample database.     

High-Tc superconductivity in superhard diamondlike BC5

Using density functional theory calculations we show that the recently synthesized superhard diamondlike BC5 is superconducting with a critical temperature of the same order as that of MgB2. The average electron-phonon coupling is lambda=0.89, the phonon-frequency logarithmic average is log=67.4 meV, and the isotope coefficients are alpha(C)=0.3 and alpha(B)=0.2. In BC5, superconductivity is mostly sustained by concerted vibrations of the B atom and its C neighbors.     

Analysis for the optimal location of cable damping systems on stayed bridges

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.     

Virtual Computational Chemistry Laboratory – Design and Description

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.     

Predictive (un)distortion model and 3-D reconstruction by biplane snakes

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.     

Silica-based powders and monoliths with bimodal pore systems

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.     

Geometry and halogen regiochemistry determination of vicinal vinyl dihalides by 1H and 13C NMR. Application to the structure elucidation of prefuroplocamioid,an unusual marine monoterpene

Empirical rules based on 13C and 1H NMR spectroscopy to determine the regiochemistry and geometry of the 1,2-bromochloro vinyl portion of naturally occurring or synthetic compounds containing this functionality are proposed. The key feature of the method comes from the comparison of the spectral data of the new monoterpene metabolite, prefuroplocamioid, isolated from Plocamium cartilagineum, with those of other marine monoterpenes, as well as with some model compounds found in the literature.     

Analysis and purification of DNA restriction fragments by high-performance liquid chromatography.

The purification and analysis of restriction fragments play a very important role in molecular biology but the traditional assay methods of DNA fragments, based on gel electrophoresis and caesium chloride gradient centrifugation, are time-consuming and difficult to quantify. High-performance liquid chromatography provides an alternative method which allows the direct quantitation of picogram amounts of eluents in short time. In the present work we report the separation of different restriction fragments, the purification of some fragments and the relationship between the length of double-stranded DNA fragments and peak areas.