Homogenization of magneto-electro-elastic multilaminated materials

In this work, based on the periodic unfolding homogenizationtechnique, the limiting equations modelling the behaviour ofthree-dimensional magneto-electro-elastic periodic structuresare rigorously established. The local problems and the correspondinghomogenized coefficients of the elastic, dielectric, magneticpermittivity, piezoelectric, piezomagnetic and magneto-electric(ME) tensors are explicitly described. The homogenization modelis exemplified for laminated composites and a unified generalformula for all effective properties of periodic multilaminatedmagneto-electro-elastic composites is obtained. This formulais applied to investigate the global behaviour for the importantcase of transversely isotropic constituents and any finite numberof layers in each periodic cell. Examples that provide theoreticalevidence of the presence of both a product property and theME effect are given.     

Close-loop three-laser scheme for chaos-encrypted message transmission

In this paper, we numerically evaluate private data transmission using a three-laser scheme, consisting of a pair of twin semiconductor lasers, driven to chaos by delayed optical feedback in a short cavity, and optically injected by a third chaotic laser which forces them to synchronize. This laser is selected with different internal parameters with respect to the twin pair, so that the emissions of the synchronized, matched lasers, are highly correlated, whereas their correlation with the driver is low. The digital message modulates the emission of the transmitter, as in a standard Chaos Modulation scheme. Message recovery is then obtained by subtracting, from the transmitted chaos-masked message, the chaos, locally generated by the synchronized receiver laser. Simulations have been performed with the Lang-Kobayashi model, and, in view of application to private transmission, we have investigated the effect of the parameter mismatch, between transmitter and receiver, on message recovery. A preliminary experimental evaluation has been also performed using specially designed InP integrated modules.     

A fast gas chromatography/mass spectrometry method for the determination of stimulants and narcotics in urine

A fast method has been developed for the simultaneous determination of 52 stimulants and narcotics excreted unconjugated in urine by gas chromatography/mass spectrometry (GC/MS). The procedure involves the liquid/liquid extraction of the analytes from urine at strong alkaline pH and the injection of the extract into a GC/MS instrument with a fast GC column (10 m × 0.18 mm i.d.); the short column allows the complete separation of the 52 analytes in a chromatographic run of 8 min. The method has been fully validated giving lower limits of detection (LLODs) satisfactory for its application to antidoping analysis as well as to forensic toxicology. The repeatability of the concentrations and the retention times are good both for intra‐ and for inter‐day experiments (%CV of concentrations always lower than 15 and %CV of retention times lower than 0.6). In addition, the analytical bias is satisfactory (A% always >15%). The method proposed here would be particularly useful whenever there are time constraints and the analyses have to be completed in the shortest possible time. Copyright © 2010 John Wiley & Sons, Ltd.     

Multiplex bioanalytical methods for food and environmental monitoring

Recent advances in miniaturization of analytical systems and newly emerging technologies offer platforms with greater automation and multiplexing capabilities than traditional biological binding assays. Multiplexed bioanalytical techniques provide control agencies and food industries with new possibilities for improved, more efficient monitoring of food and environmental contaminants. This review deals with recent developments in planar-array and suspension-array technologies, and their applications in detecting pathogens, food allergens and adulterants, toxins, antibiotics and environmental contaminants.     

A gas chromatography/mass spectrometry method for the determination of sildenafil,vardenafil and tadalafil and their metabolites in human urine

Sildenafil (SDF), vardenafil (VDF) and tadalafil (TDF) are phosphodiesterase type 5 enzyme inhibitors (PDE5Is), used in the treatment of erectile disorders and to improve breathing efficiency in pulmonary hypertension. The increasing incidence of their use among young athletes has drawn the attention of the anti‐doping authorities to the possible abuse of PDE5Is by athletes due to their pharmacological activities. This paper describes a method for the determination in urine of PDE5Is and their metabolites by gas chromatography/mass spectrometry (GC/MS) after liquid/liquid extraction of the analytes from urine and derivatisation to obtain trimethylsilyl derivatives. The metabolic profile was studied on real samples collected from subjects taking PDE5Is (Viagra®, Levitra® or Cialis®); the main urinary metabolites were identified and their MS fragmentation characterized. The sample pre‐treatment and GC/MS conditions for the detection of the metabolites have been optimised. A method for their preliminary screening and subsequent confirmation is described that takes into account the general requirements of a routine doping analysis to be used for the screening of large numbers of samples. The main metabolites identified can be included in a general purpose screening method and all the metabolites in a more specific confirmation method. The method developed has been applied for the screening of PDE5Is in 5000 urine samples. Based on the obtained results, the proposed method appears to be of practical use in analytical and forensic toxicology, including doping analysis. Copyright © 2010 John Wiley & Sons, Ltd.     

π‐Expanded α,β‐Unsaturated Ketones: Synthesis,Optical Properties,and Two‐Photon‐Induced Polymerization

A library of π‐expanded α,β‐unsaturated ketones was designed and synthesized. They were prepared by a combination of Wittig reaction, Sonogashira reaction, and aldol condensation. It was further demonstrated that the double aldol condensation can be performed effectively for highly polarized styrene‐ and diphenylacetylene‐derived aldehydes. The strategic placement of two dialkylamino groups at the periphery of D ‐π‐A‐π‐D molecules resulted in dyes with excellent solubility. These ketones absorb light in the region 400–550 nm. Many of them display strong solvatochromism so that the emission ranges from 530–580 nm in toluene to the near‐IR region in benzonitrile. Ketones based on cyclobutanone as central moieties display very high fluorescence quantum yields in nonpolar solvents, which decrease drastically in polar media. Photophysical studies of these new functional dyes revealed that they possess an enhanced two‐photon absorption cross section when compared with simpler ketone derivatives. Due to strong polarization of the resulting dyes, values of two‐photon absorption cross sections on the level of 200–300 GM at 800 nm were achieved, and thanks to that as well as the presence of the keto group, these new two‐photon initiators display excellent performance so that the operating region is 5–75 mW in some cases.     

Effects of interface contacts on the magneto electro-elastic coupling for fiber reinforced composites

Imperfect bonding between constituents is studied where displacements, electric and magnetic static potentials are considered to have a jump proportional to the normal component of the mechanical traction, electric displacement and magnetic flux. This condition may model various interface damages or the thin glue layer between two adjacent phases. They are termed as the mechanically compliant, dielectrically weakly capacitance and magnetically weakly inductance at the interface. It is shown that while the more imperfect the interface is, the overall properties become weaker, such as longitudinal shear stiffness, out-of-plane piezoelectric coupling, and magnetoelectric coupling. Out-of-plane piezomagnetic coupling, transverse dielectric permittivity and transverse dielectric permeability exhibit no influence by imperfect bonding. The imperfect interface proposed is mimicked by the springs, capacitors and inductances for the mechanical, electric and magnetic interaction between the phases and are highly sensitive to the interphase properties. The results are compared mainly with the self consistent model reported in the literature and good agreements are shown.     

argE-encoded N-acetyl-L-ornithine deacetylase from Escherichia coli contains a dinuclear metalloactive site

The catalytic and structural properties of the argE-encoded N-acetyl-L-ornithine deacetylase (ArgE) from Escherichia coli were investigated. On the basis of kinetic and ITC (isothermal titration calorimetry) data, Zn(II) binds to ArgE with Kd values that differ by approximately 20 times. Moreover, ArgE exhibits approximately 90% of its full catalytic activity upon addition of one metal ion. Therefore, ArgE behaves similarly to the aminopeptidase from Aeromonas proteolytica (AAP) in that one metal ion is the catalytic metal ion while the second likely plays a structural role. The N-acetyl-L-ornithine (NAO) deacetylase activity of ArgE showed a linear temperature dependence from 20 to 45 degrees C, indicating that the rate-limiting step does not change over this temperature range. The activation energy for NAO hydrolysis by ArgE was 25.6 kJ/mol when loaded with Zn(II) and 34.3 kJ/mol when loaded with Co(II). Electronic absorption and EPR (electron paramagnetic resonance) spectra of [Co x (ArgE)] and [CoCo(ArgE)] indicate that both divalent metal binding sites are five coordinate. In addition, EPR data show clear evidence of spin-spin coupling between the Co(II) ions in the active site but only after addition of a second equivalent of Co(II). Combination of these data provides the first physical evidence that the ArgE from E. coli contains a dinuclear Zn(II) active site, similar to AAP and the carboxypeptidase G2 from Pseudomonas sp. strain RS-16 (CPG2).