Flatness defects after bridle rolls: a numerical analysis of leveling

Leveling is a forming process used in the aluminum industry in order to correct flatness defects and minimize residual stresses in strips thanks to bending under tension. This paper introduces a 3D finite element model to simulate the sheet threading in an elementary part of a leveler called bridle rolls. It can compute plastic strains and residual stresses through width and thickness, but predict the deformed strip after springback and potential buckling phenomena as well. The influence of geometric and mechanical parameters (like friction or rolls profile) on final flatness are also investigated. Finally initial defects are taken into account and the model shows how they are modified.     

Functionalization of single- and multi-walled carbon nanotubes with cationic amphiphiles for plasmid DNA complexation and transfection

The possibility of delivering DNA efficiently to cells represents a crucial issue for the treatment of both genetic and acquired diseases. However, even although the efficiency of non-viral transfection systems has improved in the last decade, none have yet proven to be sufficiently effective in vivo. We report herein our results on the functionalization of single-walled carbon nanotubes (SWNT) and multi-walled carbon nanotubes (MWNT) by two cationic amphiphiles (lipid RPR120535 and pyrenyl polyamine), their use for the complexation of plasmid DNA, and their efficiency in transfecting cells in vitro. The experiments have shown that the efficiency of transfection is higher when using SWNT instead of MWNT, and that transfection efficiency is similar or slightly higher when using nanoplexes (SWNT/lipid RPR120535/DNA) instead of lipoplexes (lipid RPR120535/DNA) and several orders of magnitude higher than that of naked DNA. This study therefore shows both that the transfection is better when using SWNTs and that it is dependent on the nature of the amphiphilic molecules adsorbed on the nanotubes.      

Simple and effective method for the analytic description of important optical beams when truncated by finite apertures

In this paper we present a simple and effective method, based on appropriate superpositions of Bessel-Gauss beams, which in the Fresnel regime is able to describe in analytic form the three-dimensional evolution of important waves as Bessel beams, plane waves, gaussian beams, and Bessel-Gauss beams when truncated by finite apertures. One of the by-products of our mathematical method is that one can get in a few seconds, or minutes, high-precision results, which normally require quite lengthy numerical simulations. The method works in electromagnetism (optics, microwaves) as well as in acoustics.     

Survey of structural and electronic properties of C60 on close-packed metal surfaces

The adsorption of buckminsterfullerene (C₆₀) on metal surfaces has been investigated extensively for its unique geometric and electronic properties. The two-dimensional systems formed on surfaces allow studying in detail the interplay between bonding and electronic structures. Recent studies reveal that C₆₀ adsorption induces reconstruction of even the less-reactive close-packed metal surfaces. First-principles computations enable access to this important issue by providing not only detailed atomic structure but also electronic properties of the substrate–adsorbate interaction, which can be compared with various experimental techniques to determine and understand the interface structures. This review discusses in detail the ordered phases of C₆₀ monolayers on metal surfaces and the surface reconstruction induced by C₆₀ adsorption, with an emphasis on the different types of reconstruction resulting on close-packed metal surfaces. We show that the symmetry matching between C₆₀ molecules and metal surfaces determines the local adsorption configurations, while the size matching between C₆₀ molecules and the metal surface lattice determines the supercell sizes and shapes; importantly and uniquely for C₆₀, the number of surface metal atoms within one supercell determines the different types of reconstruction that can occur. The atomic structure at the molecule–metal interface is of crucial importance for the monolayer’s electronic and transport properties: these will also be discussed for the well-defined adsorption structures, especially from the perspective of tuning the electronic structure via C₆₀–metal interface reconstruction and via relative inter-C₆₀ orientations.     

Frequency dispersion of electro-optical properties over a wide range by means of time-response analysis

We show that a Z-transform-based time-response analysis of the electro-optical response of a crystal to a step voltage with a short rise time allows one to obtain the dispersion of the electro-optical coefficients over a wide frequency range. We describe the method employed and present the results obtained for the main electroptic coefficients (r22, r61, and rc) of a standard LiNbO3 crystal. We also show that this method is able to provide even small values of the electro-optic coefficient as well as the dispersion within a wide frequency range, which is limited only by the rise time of the step voltage.     

The local spatial autocorrelation and the kernel method for identifying black zones. A comparative approach

This article aims to determine the location and the length of road sections characterized by a concentration of accidents (black zones). Two methods are compared: one based on a local decomposition of a global autocorrelation index, the other on kernel estimation. After explanation, both methods are applied and compared in terms of operational results, respective advantages and shortcomings, as well as underlying conceptual elements. The operationality of both methods is illustrated by an application to one Belgian road.     

The local spatial autocorrelation and the kernel method for identifying black zones: A comparative approach

This article aims to determine the location and the length of road sections characterized by a concentration of accidents (black zones). Two methods are compared: one based on a local decomposition of a global autocorrelation index, the other on kernel estimation. After explanation, both methods are applied and compared in terms of operational results, respective advantages and shortcomings, as well as underlying conceptual elements. The operationality of both methods is illustrated by an application to one Belgian road.     

Urine testing for designer steroids by liquid chromatography with androgen bioassay detection and electrospray quadrupole time-of-flight mass spectrometry identification

New anabolic steroids show up occasionally in sports doping and in veterinary control. The discovery of these designer steroids is facilitated by findings of illicit preparations, thus allowing bioactivity testing, structure elucidation using NMR and mass spectrometry, and final incorporation in urine testing. However, as long as these preparations remain undiscovered, new designer steroids are not screened for in routine sports doping or veterinary control urine tests since the established GC/MS and LC/MS/MS methods are set up for the monitoring of a few selected ions or MS/MS transitions of known substances only. In this study, the feasibility of androgen bioactivity testing and mass spectrometric identification is being investigated for trace analysis of designer steroids in urine. Following enzymatic deconjugation and a generic solid-phase extraction, the samples are analyzed by gradient LC with effluent splitting toward two identical 96-well fraction collectors. One well plate is used for androgen bioactivity detection using a novel robust yeast reporter gene bioassay yielding a biogram featuring a 20-s time resolution. The bioactive wells direct the identification efforts to the corresponding well numbers in the duplicate plate. These are subjected to high-resolution LC using a short column packed with 1.7-microm C18 material and coupled with electrospray quadrupole time-of-flight mass spectrometry (LC/QTOFMS) with accurate mass measurement. Element compositions are calculated and used to interrogate electronic substance databases. The feasibility of this approach for doping control is demonstrated via the screening of human urine samples spiked with the designer anabolic steroid tetrahydrogestrinone. Application of the proposed methodology, complementary to the established targeted urine screening for known anabolics, will increase the chance of finding unknown emerging designer steroids, rather then being solely dependent on findings of the illicit preparations themselves.     

Characterization of high refractive index semiconductor films by surface plasmon resonance

Si-based surface plasmon resonance (SPR) in the Kretschmann-Raether geometry is considered as a platform for the optical measurement of high refractive index films. The implementation of the SPR effect becomes possible due to the relatively high index of refraction of Si compared to most materials. As examples we study the SPR responses for some important semiconductor-based films, including laser-ablated porous silicon and thin germanium films. Using SPR data, we determine the refractive indices of these films for different parameters (thickness and porosity) and ambiences. We also discuss novel SPR biosensor architectures with the use of these solid films.     

Achieving targets for bone and mineral metabolism: the impact of cinacalcet HCl in clinical practice

Achieving the K/DOQI targets for bone and mineral metabolism has proven difficult with the use of vitamin D analogues and phosphate binders. The introduction of cinacalcet HCl provided a new tool with a novel therapeutic mechanism of action. The purpose of this study was to evaluate the effect of the introduction of combination algorithm for managing secondary hyperparathyroidism (SHPT) on phosphorus, calcium, and biointact parathyroid hormone (PTH). The 61 patients who dialyzed in the facility from January 2004 (baseline) and who remained in the facility as of April 2005 (follow-up) were included in the study. In the baseline period, 37 (61%) of the patients received paricalcitol at some time during the 3-month observation period. In the follow-up period, 19% or 31% of the patients received cinacalcet HCl. Of those not receiving cinacalcet HCl, 67% had PTH at or below target, 17% were felt to be noncompliant with oral meds, 7% had low calcium, and 10% either could not get the medication or were not switched to the combination pathway. Compared with the baseline period, the percent of patients who met the PTH target increased from 19.7% to 37.7%, p<0.05. The percent of patients meeting all 4 targets increased from 14.8% to 24.6%, although this did not reach statistical significance. The introduction of cinacalcet HCl into a treatment algorithm for management of SHPT resulted in a significant increase in the percentage of patients achieving the PTH target while maintaining the other mineral metabolism targets.