Floating-patch MEMS antennas on HRS substrate for millimetre-wave applications

Novel floating-patch micro-electro-mechanical system (MEMS) antennas are proposed for millimetre-wave applications. The floating-patch MEMS antennas are fabricated on a high resistivity silicon (HRS) substrate using surface micromachining technology. Simulation and experimental results for reflection coefficients and radiation patterns are presented.     

Effects of reducing and oxidizing atmospheres on the PTCR characteristics of porous n-BaTiO3 ceramics by adding polyethylene glycol

Donor doped BaTiO₃ (n-BaTiO₃) ceramics were fabricated by adding polyethylene glycol (PEG) at 20 wt %. The effects of reducing and oxidizing atmospheres on the PTCR characteristics of the porous n-BaTiO₃ ceramics were investigated. The PTCR characteristics of the porous n-BaTiO₃ ceramics is strongly affected by chemisorbed oxygen at the grain boundaries and are recovered as the atmosphere is changed from the reducing gas to oxidizing gas. The low room-temperature resistivity of the porous n-BaTiO₃ ceramics in reducing atmospheres may be caused by the decrease in potential barrier height, which originates from an increase in the number of electrons owing to the desorption of chemisorbed oxygen atoms at the grain boundaries. In addition, the high room-temperature resistivity of the porous n-BaTiO₃ ceramics in oxidizing atmospheres may be caused by the increase in potential barrier height, which results from the adsorption of chemisorbed oxygen atoms at the grain boundaries.     

Lysis of human monocytic leukemia cells by extracellular adenosine triphosphate: mechanism and characterization of the adenosine triphosphate receptor

The present study shows that extracellular adenosine triphosphate (ATP) has the capacity to mediate dose-dependent lysis of the monocytic leukemia cell line THP-1. The lysis, assessed by 51Cr release, was found to be selective for ATP, because adenosine diphosphate (ADP) or other nucleotides were less effective in their ability to lyse the cells. The amount of 51Cr released was particularly enhanced by the stimulation of the cells with 1,000 U/mL of interferon gamma (IFN-gamma) for 3 days, and the sensitivity was time and dose dependent. Analysis of the mechanism of lysis indicated that the fully ionized form, ATP4-, mediated the lysis, because the addition of cation chelators or the absence of the divalent cations, Ca2+ and Mg2+, in the culture medium of a 6-hour 51Cr release assay increased the percent specific lysis. Therefore, the ATP receptors on THP-1 cells were classified as P2Z purinoceptors. Moreover, it is shown here that the Ca2+/calmodulin complex plays a role in the regulation of the lysis by extracellular ATP of THP-1 cells, because antagonists of this complex, such as trifluoperazine or KN-62, were found to inhibit the ATP-mediated cell lysis.     

Acidity near eroding polylactide-polyglycolide in vitro and in vivo in rabbit tibial bone chambers

Eroding poly(DL-lactide-co-glycolide)(PDLLG) washers were observed chronically in vitro and in vivo following loading in a bone chamber tibial implant (BCI). Images were recorded using intravital microscopy of the implanted rabbit and direct pH measurements were obtained of the tissue in the bone chamber using a combination probe-reference microelectrode. While statistically significant pH differences were found between the control (unloaded) and experimental (PDLLG-bearing) BCIs, they were only of the order of 0.2 pH units. This value proved to be physiologically insignificant as no statistically significant difference in bone defect healing, as indicated by angiogenesis, was detected. It was shown that the measured small pH changes during PDLLG washers erosion would result whether the buffer was phosphate-buffered saline replaced weekly or interstitial fluid subject to vascular exchanges.     

Reaching the global minimum in docking simulations: a Monte Carlo energy minimization approach using Bezier splines

The docking problem faces two major challenges: the global optimization of a multivariable function, such as the energy, and the ability to discriminate between true and false positive results, i.e., native from nonnative structures based on the input energy function. Among all energy evaluation tools, only a local energy-minimization method using an accurate enough potential function is able to discriminate between native and nonnative structures. To meet these requirements, a Monte Carlo with energy-minimization method has been incorporated into a new ECEPP/3 docking program. The efficiency of the simulation results from the use of an energy-grid technique based on Bezier splines and from a simplification of the receptor by switching on the energy of only important residues of the active site. Simulations of a thrombin-inhibitor complex show that the global minimum of the energy function was reached in every independent run within less than 3 min of time on an IBM RX 6000 computer. For comparison, 10 standard independent Monte Carlo simulations with 10(6) steps in each were carried out. Only three of them led to a conformation close to the x-ray structure. The latter simulations required an average of 24 min and about 10 hr with and without the grid, respectively. Another important result is that the Bezier spline technique not only speeds up the calculation by reducing the number of operations during the energy evaluation but also helps in reaching the global minimum by smoothing out the potential energy surface.     

Physiologic correlates to running performance in pre-pubertal distance runners

In adults, four major variables have been shown to be associated with success in distance running performance: submaximal oxygen consumption (running economy), peak oxygen consumption (Peak VO2), ventilatory threshold (VT) and fractional utilisation (FU). The primary aim of this study was to describe the relationship between the 3000 m race times of run-trained prepubertal boys to these four variables. Thirteen male run-trained pre-pubertal boys (age 11.7 +/- 1.1 yrs, mean +/- SD), volunteered to take part in a 3000 m time trial and laboratory assessment, consisting of treadmill running at four submaximal speeds (8, 9.6, 11.2 and 12.8 km.h-1) as well as a peak VO2 test. The group demonstrated a heterogeneous array of peak VO2 data. A high level of association (p < 0.05) was found between mass-relative peak VO2 and 3000 m time trial results (r = -0.83). In addition ventilatory threshold expressed as %peak VO2, VO2 at VT and estimated velocity at VT was also highly related to 3000 m time trial (r = -0.78, -0.77 and -0.77) respectively. Fractional utilisation (%peak VO2) was significantly (p < 0.05) associated with race time at the final two submaximal running speeds only (11.2 and 12.8 km.h-1) (r = 0.61 and 0.67, respectively). Respiratory Exchange Ratio (RER) was also found to be significantly (p < 0.05) associated with 3000 m race time at 11.2 and 12.8 km.h-1. Overall peak VO2 appeared to be the single most important factor associated with success at 3000 m.     

Still image coding based on vector quantization and fractalapproximation

In this paper, we propose a coding algorithm for still images using vector quantization (VQ) and fractal approximation, in which low-frequency components of an input image are approximated by VQ, and its residual is coded by fractal mapping. The conventional fractal coding algorithms indirectly used the gray patterns of an original image with contraction mapping, whereas the proposed fractal coding method employs an approximated and then decimated image as a domain pool and uses its gray patterns. Thus, the proposed algorithm utilizes fractal approximation without the constraint of contraction mapping. For approximation of an original image, we employ the discrete cosine transform (DCT) rather than conventional polynomial-based transforms. In addition, for variable blocksize segmentation, we use the fractal dimension of a block that represents the roughness of the gray surface of a region. Computer simulations with several test images show that the proposed method shows better performance than the conventional fractal coding methods for encoding still pictures.     

A 44-GHz monolithic waveguide plane-wave amplifier with improvedunit cell design [using pHEMTs]

A 44-GHz monolithic waveguide plane-wave amplifier (PWA) with improved unit cell design is presented in this paper. The unit cell is a two-stage direct-coupled design and satisfies size, bistability, and stability requirements of the waveguide PWA. The ultra-compact unit cell had a cell size of 0.8 mm², and showed a small-signal gain of 8 dB and an output power of 15 dBm at 44 GHz with a corresponding dc-to-RF efficiency of 10%. A monolithic waveguide PWA using these unit cells showed a “flange-to-flange” gain of 5 dB, an output power of 0.3 W, and an efficiency of 2% at 44 GHz