Effect of hydrogen on the properties and fracture characteristics of TRIP 800 steels

The paper describes effect of hydrogen on the properties and fracture characteristics of two variants of TRIP 800 C–Mn–Si steels. The effect of hydrogen was studied by means of tensile tests on specimens previously charged by hydrogen. Hydrogen provoked embrittlement in both variants but only for very high hydrogen content. Hydrogen embrittlement manifested itself mainly by a loss of plasticity. Both steel variants were able to absorb a large amount of hydrogen, up to 50 ppm. Concerning fractographic characteristics, steels containing higher hydrogen content displayed transgranular cleavage fracture. In exceptional cases, an irreversible embrittlement was revealed initiating on non-metallic inclusions.     

On using the Viterbi path along with HMM likelihood information for online signature verification.

This paper describes a system using two complementary sorts of information issuing from a hidden Markov model (HMM) for online signature verification. At each point of the signature, 25 features are extracted. These features are normalized before training and testing in order to improve the performance of the system. This normalization is writer-dependent; it exploits only five genuine signatures used to train the writer HMM. A claimed identity is confirmed when the arithmetic mean of two similarity scores, obtained on an input signature, is higher than a threshold. The first score is related to the likelihood given by the HMM of the claimed identity; the second score is related to the segmentation given by such an HMM on the input signature. A personalized score normalization is also proposed before fusion. Our approach is evaluated on several online signature databases, such as BIOMET, PHILIPS, MCYT, and SVC2004, which were captured under different acquisition conditions. For the first time in signature verification, we show that the fusion of segmentation-based information generated by the HMM with likelihood-based information considerably improves the quality of the verification system. Finally, owing to our two-stage normalization (at the feature and score levels), we show that our system results in more stable client-score distributions across databases and in a better separation between the distributions of client and impostor scores.     

An Overgrowth-Free Design for InGaAlAs Spot-Size-Converted Ridge Waveguide Lasers

A great deal of work has been done over the past several years toward the development of lasers with integrated spot-size converters, for better coupling directly to flat cleaved fiber or better alignment tolerance in lensed systems. Many of the techniques, such as butt-coupling or lateral-taper-vertical-shift, require etch-and-regrowth over the active region and as such are not applicable directly to Al-containing lasers. In this letter, we demonstrate a simple method to achieve narrow (15deg times 15deg) far fields in Al-containing devices with a moderate degradation of dc, dynamic and thermal characteristics. At room temperature, uncoated 300-mum-long devices have thresholds of about 18 mA and slope efficiencies of about 0.24 W/A, with 27% power coupled directly into flat cleaved fiber compared to ~10% for a conventional (>30deg far field) device. Comparison between calculated and measured far fields versus ridge width and number of quantum wells gives design curve information for optimizing far field performance.     

Determination of biological toxins using capillary electrokinetic chromatography with multiphoton-excited fluorescence

We report a highly sensitive and rapid strategy for characterizing biological toxins based on capillary electrokinetic chromatography with multiphoton-excited fluorescence. In this approach, aflatoxins B1, B2, and G1 and the cholera toxin A-subunit are fractionated in approximately 80 s in a narrow-bore electrophoretic channel using the negatively charged pseudostationary phase, carboxymethyl-beta-cyclodextrin. The aflatoxins--highly mutagenic multiple-ringed heterocycles produced by Aspergillus fungi--are excited at the capillary outlet through the simultaneous absorption of two to three 750-nm photons to yield characteristic blue fluorescence; cholera toxin A-subunit, the catalytic domain of the bacterial protein toxin from Vibrio cholera, is excited through an unidentified multiphoton pathway that apparently includes photochemical transformation of an aromatic residue in the polypeptide. The anionic carboxymethyl-beta-cyclodextrin, used to chromatographically resolve the uncharged aflatoxins, enhances emission from these compounds without contributing substantially to the background. Detection limits for these toxins separated in 2.1-micron-i.d. capillaries range from 4.4 zmol (approximately 2700 molecules) for aflatoxin B2 to 3.4 amol for the cholera toxin A-subunit. Larger (16-micron-i.d.) separation capillaries provide concentration detection limits for aflatoxins in the 0.2-0.4 nM range, severalfold lower than achieved in 2.1-micron capillaries. These results represent an improvement of > 10(4) in mass detectability compared to previously published capillary separations of aflatoxins and demonstrate new possibilities for the analysis of proteins and peptides.     

Exact computation of the infimum inH∞-optimization via output feedback

The authors present a simple and noniterative procedure for the computation of the exact value of the infimum in the standard H_∞-optimal control with output feedback. The problem formulation is general and does not place any restrictions on the direct feedthrough terms between the control input and the controlled output variables, and between the disturbance input and the measurement output variables. The method is applicable to systems that satisfy the following conditions: (1) the transfer function from the control input to the controlled output is right-invertible and has no invariant zeros on the jω axis, and (2) the transfer function from the disturbance to the measurement output is left-invertible and has no invariant zeros on the jω axis     

N-terminal DNA-binding domains contribute to differential DNA-binding specificities of NF-kappa B p50 and p65

We previously reported that either oxidation or alkylation of NF-kappa B in vitro abrogates DNA binding. We used this phenomenon to help elucidate structural determinants of NF-kappa B binding. We now demonstrate that Cys-62 of NF-kappa B p50 mediates the redox effect and lies within an N-terminal region required for DNA binding but not for dimerization. Several point mutations in this region confer a transdominant negative binding phenotype to p50. The region is highly conserved in all Rel family proteins, and we have determined that it is also critical for DNA binding of NF-kappa B p65. Replacement of the N-terminal region of p65 with the corresponding region from p50 changes its DNA-binding specificity towards that of p50. These data suggest that the N-terminal regions of p50 and p65 are critical for DNA binding and help determine the DNA-binding specificities of p50 and p65. We have defined within the N-terminal region a sequence motif, R(F/G)(R/K)YXCE, which is present in Rel family proteins and also in zinc finger proteins capable of binding to kappa B sites. The potential significance of this finding is discussed.     

A hand-held decision-aid system designed for rural health workers

A great part of the world's population is cared for by rural health workers who are also collecting data for epidemiological studies. These workers have a low level of medical training and are working in a poor technical environment. At the request of an international humanitarian and medical organization (Médecins Sans Frontières), we have developed an integrated (hardware and software) system, TROPICAID, based on a hand-held computer and designed to increase rural health workers' efficiency. The software is easy to use and enables users to get information from an internal data base on 60 drugs. The decision-making module analyzes the patient's parameters (460 different symptoms are recognized) and indicates possible diagnoses (the system knows 210) and relevant treatments. In addition, the system facilitates the collection of medical data for elementary statistical analysis. The computer, which is lightweight (1.5 kg) and compact, runs on battery power for up to a week in normal use. The program which is written in Pascal and data are stored in high-capacity EPROMs. An early trial in Chad with Médecins sans Frontières has shown the value of such a project as well as a few weaknesses to be overcome.     

Morphological characterization of reaction injection moulded (RIM) polyester-based polyurethanes

Characterization studies of reaction injection moulded (RIM) processed (in-situ polymerized) polyester-based segmented thermoplastic polyurethane have been performed utilizing various morphological techniques. The fast and exothermic urethane polymerization results in large temperature gradients in the mould which influence molecular weight and morphological structures. The present work is conducted to draw relationships between sample morphology and the processing conditions utilized to form the polymer.