A novel ceramic matrix composite based on YNbO4–TiO2 for microwave applications

This work presents the dielectric properties of YNbO₄ (YNO)–TiO₂ composites in the microwave range. X-ray diffraction analysis demonstrates that the addition of TiO₂ to YNO results in the formation of a Y(Nb_0.5Ti_0.5)₂O₆ phase. In the microwave range, the values of permittivity and dielectric loss did not present major changes with the increment of TiO₂. Moreover, the addition of TiO₂ results in an improvement in the thermal stability of YNO, with YNO63 demonstrating a resonant frequency of ?8.96 ppm.°C^?1. We utilised numerical simulations to evaluate the behaviour of these materials as dielectric resonator antennae and it is found that they exhibit a reflection coefficient below ?10 dB at the resonant frequency, with a realised gain of 4.94 – 5.76 dBi, a bandwidth of 665–1050 MHz and a radiation efficiency above 84%. Our results indicate that YNO–TiO₂ composites are interesting candidates for microwave operating devices.     

Chitosan Microspheres as Carriers for pH‐Indicating Species in Corrosion Sensing

Chitosan microspheres containing bromocresol green, cresol red, and phenolphthalein for corrosion detection, through pH change, are synthesized in order to be used in protective coatings for aluminium alloys. Microspheres containing corrosion detection species are characterized morphologically (SEM) and physico‐chemically (FTIR, TGA). Release studies (UV–vis) are performed in corrosion‐promoting conditions (pH, NaCl), and detection studies by immersion in media associated with corrosion activity while microspheres' sensing activity is evaluated visually. Electrochemical characterization of AA2024 substrates in the presence of chitosan spheres is performed to understand material performance, and a color change is observed as a result of local pH increase in cathodic areas when corrosion takes place. These findings can be correlated with the results from release studies and seem a promising approach for corrosion sensing purposes, not only because pH increase is possible to detect due to corrosion, but also because chitosan is considered an environmentally friendly material.     

A New Hand-Held Microsystem Architecture for Biological Analysis

This paper presents a hand-held microsystem based on new fully integrated magnetoresistive biochips for biomolecular recognition (DNA hybridization, antibody antigen interaction, etc.). Magnetoresistive chip surfaces are chemically treated, enabling the immobilization of probe biomolecules such as DNA or antibodies. Fluid handling is also integrated in the biochip. The proposed microsystem not only integrates the biochip, which is an array of 16times16 magnetoresistive sensors, but it also provides all the electronic circuitry for addressing and reading out each transducer. The proposed architecture and circuits were specifically designed for achieving a compact, programmable and portable microsystem. The microsystem also integrates a hand-held analyzer connected through a wireless channel. A prototype of the system was already developed and detection of magnetic nanoparticles was obtained. This indicates that the system may be used for magnetic label based bioassays     

Academic faculty practices: issues for viability in competitive managed care markets

This study compares the perspectives of eighteen managed care executives and twenty-four faculty practice executives on critical policy issues related to the managed care marketplace. Market sites studied in 1994 included four major metropolitan areas: Minneapolis-St. Paul, Los Angeles, Philadelphia, and Atlanta. These markets were selected as being representative of communities with descending degrees of managed care involvement, but with significant market activity. Study participants from both managed care systems and faculty practices examined five policy issues: (1) the importance of including academic medical centers in current and future health care plans for marketing purposes; (2) the provision of clinical services that are unique to the academic medical center, that is, unavailable elsewhere in the community; (3) the degree of financial supplement that employers might pay for including an academic medical center; (4) future restructuring of organizations to sustain the educational mission of academic faculty within a viable delivery system; (5) satisfaction of managed care providers with graduates of academic medical centers, as measured by the clinical skills of graduate physicians. The study findings showed little support among managed care plans for paying supplements to include faculty practices in a health care network. Most study participants from managed care systems and academic faculty practices identified limited competencies that are unique to academic centers. Moreover, managed care organizations were only willing to undertake limited restructuring at best to include faculty practices within their networks. General concern about the preparation of resident physicians (especially those in primary care disciplines) for practice within contemporary managed care organizations existed among managed care informants. The results of the study indicate that as traditional funding sources for medical education are reduced, schools require greater integration with managed care plans to enable academic medical centers and their faculties to continue promoting clinical enterprise.     

The CD40-CD154 system in anti-infective host defense

Research in the past few years has documented significant advances in our understanding of the CD40-CD40 ligand (CD154) system in diverse immune functions. This system influences many T cell mediated inflammatory immune responses and effector functions, unmasking a previously unexpected role for CD40-CD154 in cell mediated immunity. Manipulation of CD154 in animal models of infection by the use of CD154-deficient mice or anti-CD154 antibodies has shown the importance of this system in the initiation of the inflammatory response, in the activation of antigen-presenting cells and in resistance to infections.     

Tuning of MST neurons to spiral motions

Cells in the dorsal division of the medial superior temporal area (MSTd) have large receptive fields and respond to expansion/contraction, rotation, and translation motions. These same motions are generated as we move through the environment, leading investigators to suggest that area MSTd analyzes the optical flow. One influential idea suggests that navigation is achieved by decomposing the optical flow into the separate and discrete channels mentioned above, that is, expansion/contraction, rotation, and translation. We directly tested whether MSTd neurons perform such a decomposition by examining whether there are cells that are preferentially tuned to intermediate spiral motions, which combine both expansion/contraction and rotation components. The finding that many cells in MSTd are preferentially selective for spiral motions indicates that this simple three-channel decomposition hypothesis for MSTd does not appear to be correct. Instead, there is a continuum of patterns to which MSTd cells are selective. In addition, we find that MSTd cells maintain their selectivity when stimuli are moved to different locations in their large receptive fields. This position invariance indicates that MSTd cells selective for expansion cannot give precise information about the retinal location of the focus of expansion. Thus, individual MSTd neurons cannot code, in a precise fashion, the direction of heading by using the location of the focus of expansion. The only way this navigational information could be accurately derived from MSTd is through the use of a coarse, population encoding. Positional invariance and selectivity for a wide array of stimuli suggest that MSTd neurons encode patterns of motion per se, regardless of whether these motions are generated by moving objects or by motion induced by observer locomotion.     

Cost-Efficient SHA Hardware Accelerators

This paper presents a new set of techniques for hardware implementations of Secure Hash Algorithm (SHA) hash functions. These techniques consist mostly in operation rescheduling and hardware reutilization, therefore, significantly decreasing the critical path and required area. Throughputs from 1.3 Gbit/s to 1.8 Gbit/s were obtained for the SHA implementations on a Xilinx VIRTEX II Pro. Compared to commercial cores and previously published research, these figures correspond to an improvement in throughput/slice in the range of 29% to 59% for SHA-1 and 54% to 100% for SHA-2. Experimental results on hybrid hardware/software implementations of the SHA cores, have shown speedups up to 150 times for the proposed cores, compared to pure software implementations.