On the production of novel zirconia-reinforced bioactive glass porous structures for bone repair

Journal of Materials Science - The objective of this study was to develop a replica method for producing zirconia-reinforced bioactive glass (ZRBG) porous structures for bone...     

Radiometers, autocorrelators, and matched-filter receivers by means of acousto-optic spectrum analysis

Acousto-optic spectrum analyzers provide a convenient means of separating wide-bandwidth signals into their frequency components. By a change in the rf input signal into the spectrum analyzer and by the provision of additional digital postprocessing, it is possible to perform radiometry, signal autocorrelation, and matched-filter reception. Although the acousto-optic device has a space-integrating architecture, the matched-filter receiver can be implemented for signals having time durations much longer than the acousto-optic cell. The resulting signal-to-noise ratio improvements from the receiver are consistent with the time-bandwidth product of the waveform, rather than the time-bandwidth product of the acousto-optic device. A mathematical foundation of the processor is presented along with specific receiver implementations. Computer-simulation and experimental results demonstrate key findings. In one experimental example, a linear-frequency-modulated waveform is matched-filter processed to recover a signal that is -24 dB with respect to the input noise floor.     

Electrochemical characterization and in vivo biocompatibility of a thick-film printed sensor for continuous in vivo monitoring

This paper assessed the material biocompatibility and investigated the temporal modulation in electrochemical performance of printed thick-film electrochemical sensing devices (ESDs) that can serve as the basis of various enzymatic sensor in detecting an electrochemically potent species. The sensors were placed in phosphate buffered saline (PBS), human serum, or implanted subcutaneously in rats, free or in stainless steel cages. The exudate collection allowed the evaluation of inflammatory cell populations, up to 21 days. The ferrous/ferric redox electrode reactions were used to assess the electrode elements performance for up to 49 days. Following testing, scanning electron microscopy (SEM) evaluated cell surface adhesion, while fibrous capsules were examined by histology. It was determined that the exudates leukocyte concentration due to the presence of sensors was comparable to the empty cage controls. For the length of the study, the sensors functionality appeared not to be influenced by the in vivo environment, when tested ex vivo, without the surrounding fibrous capsule. Surface imaging (SEM) indicated temporal focal dissolution of the Ag/AgCl electrodes with no apparent local toxicity. We concluded that the ESDs were biocompatible and their ex vivo functionality was not lost when maintained in vivo for up to 49 days.     

Adherence to antiretroviral therapy and its impact on clinical outcome in HIV-infected patients.

We analyse data on patient adherence to prescribed regimens and surrogate markers of clinical outcome for 168 human immunodeficiency virus infected patients treated with antiretroviral therapy. Data on patient adherence consisted of dose-timing measurements collected for an average of 12 months per patient via electronic monitoring of bottle opening events. We first discuss how such data can be presented to highlight suboptimal adherence patterns and between-patient differences, before introducing two novel methods by which such data can be statistically modelled. Correlations between adherence and subsequent measures of viral load and CD4+T-cell counts are then evaluated. We show that summary measures of short-term adherence, which incorporate pharmacokinetic and pharmacodynamic data on the monitored regimen, predict suboptimal trends in viral load and CD4+T-cell counts better than measures based on adherence data alone.     

Impact and penetration by L/D ≤ 1 projectiles

Calculations of steel target penetration by L/D ≤ 1 tungsten and tungsten alloy projectiles have been extended to L/D = 1/32 over the velocity range 1.5 to 5 km/s. The ratio of crater to projectile diameter tends to 1 as L/D decreases over this entire velocity range. For impact velocities of 1.5 and 3 km/s, penetration depth normalized by projectile length, P/L, increases with decreasing projectile L/D up to a maximum value and then decreases for still lower L/D. Experiments at impact velocities of 2 and 3 km/s confirm these results. For 5 km/s impact velocity, the calculations show P/L increasing with decreasing projectile L/D over the entire range 1/32 ≤ L/D ≤ 1. The projectile L/D for which the maximum P/L occurs appears to depend on the impact velocity. P/L generally scales with impact velocity as P/L v^f(L/D) where f(L/D) ranges from 0 for a long rod to, we believe, 2 in the limit as projectile L/D approaches zero. The calculations show for 1/8 ≤ L/D ≤ 1/2, P/L v^0.9; for L/D = 1/16, P/L v^1.5; and for L/D = 1/32, the new results give P/L v^1.9.     

Low temperature thermal conductivity of twinned and untwinned indium-thallium alloys

The low-temperature lattice thermal conductivity of twinned and untwinned, martensitic and non-martensitic, indium-thallium alloys has been measured to probe the effect of twin boundaries on phonon thermal transport. The phonon scattering by electrons, sample surfaces, dislocations, and thallium impurities is accounted for adequately by existing theoretical models. The reduced lattice thermal conductivity seen in twinned samples is attributed to additional phonon scattering by twin boundaries and, for the polycrystalline samples, by grain boundaries. Phonon scattering by twin boundaries is much weaker than that generally reported for grain boundaries, and is well represented by an acoustic-mismatch model.     

A new approach to defining a multidisciplinary field of science: The case of cardiovascular biology

This paper describes a new and objective method for tackling the problem of defining a multidisciplinary research area for bibliometric analysis. The test field was cardiovascular biology. A three stage process was adopted in setting a boundary around this research field:

1. Appropriate sections of a hierarchical subject classification scheme, Medical Subject Headings (MeSH), were developed into a “MeSH filter” through which papers indexed in MEDLINE were screened.
2. A panel of cardiovascular experts reviewed the core set of classification terms, identifying irrelevant and missing areas, facilitating the development of a more sophisticated “filter”.
3. The definition was validated using publication lists from research departments with a known interest in cardiovascular research.

This iterative process resulted in a definition of the field which captured basic and clinical research papers from the international biomedical research community and which was recognisable to experts in the field of cardiovascular research. Importantly, the field boundary also excluded publications which were not relevant to cardiovascular research. The process of involving experts in shaping the field definition also yielded two intangible, but key benefits: (a) it lent credibility to subsequent analyses, the results of which were to be presented to policy-makers in cardiovascular biology, and (b) it served to shape consensus among the cardiovascular experts on the full range of scientific disciplines that are relevant to their field. Analysis of international publishing in cardiovascular research revealed that whilst the UK and US dominate in total numbers of papers, the relative emphasis on cardiovascular research in these countries (as a proportion ofall biomedical publishing) is actually quite low, and declining. Japan and Germany in contrast appear to give greater emphasis to cardiovascular research in their national portfolios of biomedical science, and between 1988–1991 Japan established a marked increase in activity.     

Fast restoration of ATM networks

Asynchronous transfer mode (ATM) is now well recognized as the fundamental switching and multiplexing technique for future broadband ISDN. As these networks will be increasingly relied upon for providing a multitude of integrated voice, data, and video services, network reliability is a key concern. There are several intrinsic features of ATM networks that could potentially be exploited to provide improved restoration techniques, beyond those established for synchronous transfer mode (STM) networks, such as digital cross-connect restoration or self-healing rings. These features include ATM cell level error detection, inherent rate adaptation and nonhierarchical multiplexing. The authors explore the use of these features in developing fast restoration strategies for ATM networks. In particular, they address: (1) ATM error detection capabilities for enhanced failure detection, (2) network rerouting strategies, (3) spare capacity allocation, and (4) network control architecture and related implementation aspects. Their findings suggest that fast network span failure detection and bandwidth-efficient rerouting capabilities can be combined to develop restoration strategies for ATM networks with significantly greater performance-cost ratios when compared to existing STM network restoration strategies