The As-prepared surfaces of C-axis-oriented Nd1Ba2Cu3Oy thin films characterized using scanning probe microscopes

Recently, superconducting Nd₁Ba₂Cu₃O_y (Ndl23) thin films with high superconducting transition temperature (T _c) have been successfully fabricated at our institute employing the standard laser ablation method. In this paper, we report the results of surface characterization of the Nd123 thin films using an ultrahigh vacuum scanning tunneling microscope/spectroscopy (UHV-STM/STS) and an atomic force microscope (AFM) system operated in air. Clear spiral pattern is observed on the surfaces of Nd123 thin films by STM and AFM, suggesting that films are formed by two-dimensional island growth mode. Contour plots of the spirals show that the step heights of the spirals are not always the integer or half-integer number of thec-axis parameter of the structure. This implies that the surface natural termination layer of the films may not be unique. This result is supported byI-V STS measurements. The surface morphology of the Nd123 thin films is compared with that of thec-axis-oriented Y₁Ba₂Cu₃S_y thin films. Surface atomic images of the as-prepared Nd123 thin films are obtained employing both STM and AFM. STS measurements show that most of the surfaces are semiconductive. The results of STS measurements together with the fact that we are able to see the surface atomic images using scanning probe microscopes suggest that exposure to air does not cause serious degradation to the as-prepared surfaces of Nd123 thin films.     

Characterization of titanium alloy implant surfaces with improved dissolution resistance

The present work sets out to investigate the structure and chemistry of surface treated oxides (either aged in boiling water or air-heated) with improved dissolution resistance compared to conventionally passivated surfaces. X-ray photoelectron spectroscopy (XPS) has demonstrated a significant reduction in oxidized aluminium associated with an ageing-based surface treatment. Angle-dependent XPS has revealed an increase in amphoteric-OH surface sites for the thermal treatments. Atomic force microscopy (AFM) investigation suggests that these sites play a role in the improved proteinadsorption properties of these surfaces. These observations form the basis of a model which describes the influence of surface oxide on the kinetics of metal ion dissolution.     

Reconstitution of CD3 zeta coupling to calcium mobilization via genetic complementation

The integrity of the T cell receptor complex (CD3-TCR) transduction machinery is central to T cell development and to T cell effector function. Molecular dissection of the multimeric CD3-TCR complex revealed that at least two associated polypeptides, CD3 zeta and CD3 epsilon, autonomously couple antigenic recognition event to early and late events of the intracytoplasmic activation cascade. A 18-amino acid motif based on a tandem YXXL stretch, the activation receptor homology sequence 1 (ARH-1) motif, is necessary and sufficient to the transducing properties of both CD3 zeta and CD3 epsilon. Stimulation of chimeric molecules made of ecto- and transmembrane domains of various cell surface proteins and intracytoplasmic domains of CD3 epsilon or CD3 zeta leads to an increase in the intracellular Ca2+ concentration ([Ca2+]i) in Jurkat cells. We describe here that a similar CD25/zeta chimeric molecule was unable to induce a detectable [Ca2+]i rise upon CD25 cross-linking once expressed in the murine thymoma BW-. A Ca2+ influx could, however, be triggered in BW- cells by thapsigargin, i.e. following depletion of Ca2+ stores. Somatic cell hybrids made from BW- and either thymocytes or mature lymph node T cells reconstituted the coupling of CD3 zeta to the Ca2+ signal via an ARH-1 motif-dependent pathway. However, pervanadate-induced Ca2+ mobilization, a phenomenon attributed to tyrosine phosphorylation, was impaired in BW-cells and reconstituted in hybridomas. In contrast to the Ca2+ response, IL-2 production was induced in both BW- and hybrids cells, which questions the functional relevance of [Ca2+]i augmentation in T cell activation. In conclusion, the properties of the BW- thymoma, which define a novel group of CD3 zeta transduction cell mutants, as well as its complementation by somatic cell fusion demonstrate that this cell line represents a useful model to dissect the signaling pathway that couples CD3 zeta to Ca2+ mobilization by genetic reconstitution.     

The rank one mixed μ problem and ‘kharitonov-type’ analysis

The general mixed μ problem has been shown to be NP hard, so that the exact solution of the general problem is computationally intractable, except for small problems. In this paper we consider not the general problem, but a particular special case of this problem, the rank one mixed μ problem. We show that for this case the mixed μ problem is equivalent to its upper bound (which is convex), and it can in fact be computed easily (and exactly). This special case is shown to be equivalent to the so-called ‘affine parameter variation’ problem (for a polynomial with perturbed coefficients) which has been examined in detail in the literature, and for which several celebrated ‘Kharitonov-type’ results have been proven.     

INSTRUMENTATION FOR FLOW PROPERTIES OF GAS-SOLID SUSPENSIONS AND RECENT ADVANCES

Measurements of local velocity, density, and mass flow of phases of a gas-solid suspension are needed in determining transport properties, validating theoretical predictions, and formulating design procedures. Most of the available instruments are based on time averages or fluctuations with time. Primary standard for direct measurement of density of a phase such as solid particles is being developed. A laser phase Doppler device, within certain restrictions, may give local instantaneous density, while other optical methods and neutron beam remain secondary standards based on mass flow calibrations. An overall review including recent results has been made on both intrusive and non-intrusive instruments; their limitations and future possibilities are outlined and discussed. The limitations of the traditional approach utilizing the triangular relation between local averages of mass flow, velocity, and density of particles for the determination of flow properties, and higher order correlations are demonstrated.     

Impaired stereoacuity due to a lesion in the left pulvinar

A right-handed patient with a haematoma in the left pulvinar showed impaired stereoacuity. In contrast with previous reports, he did not show peripheral visual extinction or prolonged reaction times for targets on the side contralateral to the lesion.     

Properties of permease dimer, a fusion protein containing two lactose permease molecules from Escherichia coli

An engineered fusion protein containing two tandem lactose permease molecules (permease dimer) exhibits high transport activity and is used to test the phenomenon of negative dominance. Introduction of the mutation Glu-325-->Cys into either the first or the second half of the dimer results in a 50% decrease in activity, whereas introduction of the mutation into both halves of the dimer abolishes transport. Lactose transport by permease dimer is completely inactivated by N-ethylmaleimide; however, 40-45% activity is retained after N-ethylmaleimide treatment when either the first or the second half of the dimer is replaced with a mutant devoid of cysteine residues. The observations demonstrate that both halves of the fusion protein are equally active and suggest that each half may function independently. To test the possibility that oligomerization between dimers might account for the findings, a permease dimer was constructed that contains two different deletion mutants that complement functionally when expressed as untethered molecules. Because this construct does not catalyze lactose transport to any extent whatsoever, it is unlikely that the two halves of the dimer interact or that there is an oligomeric interaction between dimers. The approach is consistent with the contention that the functional unit of lactose permease is a monomer.     

Advancing controlled release packaging through smart blending

Researchers from Rutgers University and Clemson University have collaborated to develop a concept of using smart blending to generate functional packaging films for the controlled release of active compounds such as antimicrobials, antioxidants and flavour compounds to extend the shelf‐life of food. In this paper, literature results are reviewed to justify the significance of controlled release packaging (CRP) and the research gaps for further development are identified. A major research gap is the lack of packaging materials that can provide the release of active compounds at rates suitable for a wide range of food packaging applications. Smart blending is a promising technology for bridging this research gap. To fully realize the potentials of smart blending, a systematic approach for developing CRP using smart blending is also presented. Copyright © 2005 John Wiley & Sons, Ltd.