Nonlinear optical susceptibility of the thiogallate CdGa2S4

The nonlinear optical coefficient d36of CdGa2S4was measured to be 5 times larger than d31(LiNbO3). This large non-linearity is in good agreement with theory.     

Selecting informative data for developing peptide-MHC binding predictors using a query by committee approach

Strategies for selecting informative data points for training prediction algorithms are important, particularly when data points are difficult and costly to obtain. A Query by Committee (QBC) training strategy for selecting new data points uses the disagreement between a committee of different algorithms to suggest new data points, which most rationally complement existing data, that is, they are the most informative data points. In order to evaluate this QBC approach on a real-world problem, we compared strategies for selecting new data points. We trained neural network algorithms to obtain methods to predict the binding affinity of peptides binding to the MHC class I molecule, HLA-A2. We show that the QBC strategy leads to a higher performance than a baseline strategy where new data points are selected at random from a pool of available data. Most peptides bind HLA-A2 with a low affinity, and as expected using a strategy of selecting peptides that are predicted to have high binding affinities also lead to more accurate predictors than the base line strategy. The QBC value is shown to correlate with the measured binding affinity. This demonstrates that the different predictors can easily learn if a peptide will fail to bind, but often conflict in predicting if a peptide binds. Using a carefully constructed computational setup, we demonstrate that selecting peptides with a high QBC performs better than low QBC peptides independently from binding affinity. When predictors are trained on a very limited set of data they cannot be expected to disagree in a meaningful way and we find a data limit below which the QBC strategy fails. Finally, it should be noted that data selection strategies similar to those used here might be of use in other settings in which generation of more data is a costly process.     

Applications of X-Ray Characterization for Advanced Materials in the Electronics Industry

Nanometer thick films, quantum dots, and quantum wires are the basis of the modern electronic industry. X-ray diffraction techniques play an increasingly important role as basic characterization tools for determining detailed structural information of ultrathin film such as the evolution of strain relaxation, defect formation, film/substrate interfacial properties, and the effects of the reduced dimensionality and structural correlations to electrical properties. Materials of technological interest are SiGe and strained Si; artificial substrates such as silicon on insulator; high- and low-κ dielectric materials, which will substitute SiO₂; materials for interconnects; new materials for memory storage; micro-electro-mechanical systems (MEMS); and photovaltaics. An overview of the major X-ray scattering applications of interest to this industry will be presented in this article.     

Implementation of consequent stabilization method for simulation of multibodies described in absolute coordinates

In this article, we propose methods that increase numerical efficiency of dynamic simulation of spatial multibody systems described in absolute coordinates. The successive coordinate projection method efficiently stabilizes the system constraints in the case when a non-minimal set of orientation coordinates is used to describe the orientation of bodies in space. The new procedure of generation of Newton–Euler equations is shown in detail for systems with the most popular types of joints (prismatic joint, revolute joint, etc.). The proposed algorithms were tested with models of a governor mechanism and Yamaha YZF-R1 motorcycle engine. The simulation results show that the successive coordinate projection method is stable and can be implemented for complex mechanical systems.     

Optical phaselock receiver with multigigahertz signal bandwidth

Describes a balanced pinFET receiver which employs two signal amplification paths for homodyne detection of multigigabit-per-second, pilot-carrier PSK optical signals. Using narrow-line 1.51 mu m semiconductor lasers, the authors have employed this receiver to phaselock a local oscillator to a 295 pW pilot carrier with 8 degrees RMS phase error.<>     

Preparation and Reinforcement of Dual‐Porous Biocompatible Cellulose Scaffolds for Tissue Engineering

Biocompatible cellulose‐based aerogels composed of nanoporous struts, which embed interconnected voids of controlled micron‐size, have been prepared employing temporary templates of fused porogens, reinforcement by interpenetrating PMMA networks and supercritical carbon dioxide drying. Different combinations of cellulose solvent (Ca(SCN)₂/H₂O/LiCl or [EMIm][OAc]/DMSO) and anti‐solvent (EtOH), porogen type (paraffin wax or PMMA spheres) and porogen size (various fractions in the range of 100–500 μm) as well as intensity of PMMA reinforcement have been investigated to tailor the materials for cell scaffolding applications. All aerogels exhibited an open and dual porosity (micronporosity >100 μm and nanoporosity extending to the low micrometer range). Mechanical properties of the dual‐porous aerogels under compressive stress were considerably improved by introduction of interpenetrating PMMA networks. The effect of the reinforcing polymer on attachment, spreading, and proliferation of NIH 3T3 fibroblast cells, cultivated on selected dual‐porous aerogels to pre‐evaluate their biocompatibility was similarly positive.     

Polyurethane tri‐block copolymers—Synthesis,mechanical, elastic,and rheological properties

A series of polyurethane tri‐block copolymers were synthesized by reacting a 4,4′‐methylenebis(phenyl isocyanate) (MDI)‐endcapped poly(tetramethylene oxide) (PTMO, M_n = 2,000 g/mol) with a monoamine‐diamide (6T6m) hard segment (HS). The concentration of the HS in the copolymer was varied between 9 and 33 wt % by changing the length of the soft mid‐block segment. The structure of the copolymers was analyzed by nuclear magnetic resonance, the amide crystallinity was investigated by Fourier transform infra‐red and the thermal properties were studied by differential scanning calorimetry. The mechanical and elastic properties of the tri‐block copolymer were subsequently explored by dynamic mechanical analysis, compression set and tensile experiments, and the melt rheological behavior was studied by a parallel plate method. The amide end groups displayed a high crystallinity and the modulus of the tri‐block copolymers was relatively high. The fracture strain increased strongly with the molecular weight and the copolymers demonstrated a ductile fracture behavior for molecular weights above 6000 g/mol. Good compression set values were obtained for the tri‐block copolymers despite their low molecular weight. In the molten state, the tri‐block polymers displayed a gelling effect at low frequencies, which was believed to be a result of a clustering of the end‐segments. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Seitenkanalanalyse kontaktloser SmartCards

Berührungslose RFID-Technologie wird weltweit für verschiedenste sicherheitsrelevante Anwendungen wie den Identit?tsnachweis oder Bezahlvorg?nge eingesetzt. Nach der Aufdeckung von Schwachstellen im kryptografischen Schutz der „ersten Generation“ kontaktloser SmartCards hoffte man auf die mit sicheren Chiffren versehenen Nachfolger. Der Beitrag zeigt die Anf?lligkeit kontaktloser SmartCards für Seitenkanalangriffe am Beispiel der Mifare DESFire MF3ICD40.