Analysis of multiple-bus synchronous and asynchronous communication systems

We consider a multi-user distributed system in which nodes are connected to multiple-buses using partially duplicated bus interfaces. We study the effects of destination conflicts and bus synchronization on the system performance and show how, for a given system bus duplication can be chosen to provide guaranteed delays while increasing the interconnection system reliability. Alternative system configurations are analyzed and compared using exact and approximate Markovian models. The presented results can be used for design and optimization of high-availability distributed systems, such as loosely coupled cluster systems or backend storage networks.     

Validation of object-induced MR distortion correction for framelessstereotactic neurosurgery

Spatial fidelity is a paramount issue in image guided neurosurgery. Until recently, three-dimensional computed tomography (3D CT) has been the primary modality because it provides fast volume capture with pixel level (1 mm) accuracy. While three-dimensional magnetic resonance (3D MR) images provide superior anatomic information, published image capture protocols are time consuming and result in scanner- and object-induced magnetic field inhomogeneities which raise inaccuracy above pixel size. Using available scanner calibration software, a volumetric algorithm to correct for object-based geometric distortion, and a Fast Low Angle SHot (FLASH) 3D MR-scan protocol, the authors were able to reduce mean CT to MR skin-adhesed fiducial marker registration error from 1.36 to 1.09 mm. After dropping the worst one or two of six fiducial markers, mean registration error dropped to 0.62 mm (subpixel accuracy). Three dimensional object-induced error maps present highest 3D MR spatial infidelity at the tissue interfaces (skin/air, scalp/skull) where frameless stereotactic fiducial markers are commonly applied. The algorithm produced similar results in two patient 3D MR-scans     

Differential scanning microcalorimetry indicates that human defensin, HNP-2, interacts specifically with biomembrane mimetic systems

alpha-Defensins are antimicrobial peptides with 29-35 amino acid residues and cysteine-stabilized amphiphilic, triple-stranded beta-sheet structures. We used high-precision differential scanning microcalorimetry to investigate the effects of a human neutrophil alpha-defensin, HNP-2, on the phase behavior of model membranes mimicking bacterial and erythrocyte cell membranes. In the presence of this positively charged peptide, the phase behavior of liposomes containing negatively charged phosphatidylglycerol was markedly altered even at a high lipid-to-peptide molar ratio of 500:1. Addition of HNP-2 to liposomes mimicking bacterial membranes (mixtures of dipalmitoylphosphatidylglycerol and -ethanolamine) resulted in phase separation owing to some domains being peptide-poor and others peptide-rich. The latter are characterized by an increase of the main transition temperature, most likely arising from electric shielding of the phospholipid headgroups by the peptide. On the other hand, HNP-2 did not affect the phase behavior of membranes mimicking erythrocyte membranes (equimolar mixtures of dipalmitoylphosphatidylcholine and sphingomyelin) as well as the pure single components. This is in contrast to melittin, which significantly affected the phase behavior of choline phospholipids in accordance with its unspecific lytic activity. These results support the hypothesis of preferential interaction of defensins with negatively charged membrane cell surfaces, a common feature of bacterial cell membranes, and demonstrate that HNP-2 discriminates between model membrane systems mimicking prokaryotic and eukaryotic cell membranes.     

Convergence of the SMI and the diagonally loaded SMI algorithmswith weak interference [adaptive array]

Approximations for the power levels at the output of an adaptive array that uses the diagonally loaded sample matrix inversion (SMI) algorithm are derived. Diagonal loading is a technique where the diagonal of the covariance matrix is augmented with a positive or negative constant prior to inversion. The authors examine how the signal-to-interference-plus-noise ratio (SINR) and signal-to-interference ratio (SIR) at the array output vary with the number of samples taken when the input signals are continuous wave. It is shown that positive loading produces more rapid convergence with a reduction in output SIR. Negative loading provides an improved SIR level, but it is shown that positive loading produces more rapid convergence with a reduction in output SIR. Negative loading provides an improved SIR level, but it is shown that the output power levels are erratic and slow to converge. Simulation results which verify the theoretical procedure are given     

Proceedings of the Inter-Society Color Council Technical Conference “Instrumental Colorant Formulation 1976” Williamsburg,Virginia. III Problems of Fluorescence in Colorant Formulation

The presence of fluorescence in samples to be matched and in dyes to be used for matching requires precautions in measurement and in computation. Measurement of conventional reflectance may cause serious errors of formulation. Standard procedures for calculating matches are usually based on the additivity of the K/S values. In contrast, contributions of fluorescence have to be added to the spectral radiance factors. Specifications for a rigorous procedure are presented. Merits and shortcomings of currently used methods are discussed. An approximation making use of negative Kubelka-Munk coefficients is set forth. It is valid only for applications of a single fluorescent colorant which may be shaded slightly by minor additions of other colorants.