A least mean square error synthesis with pattern constraints atmultiple frequencies

The pattern synthesis techinque described allows the power pattern to be optimized in a very useful sense over the desired operating band of the antenna array. This is an improvement over previous techniques involving constraints on such artificial parameters as source norm and superdirectivity ratio, which do not, in fact, ensure a useful pattern bandwidth. The procedure described provides minimum mean square error over an arbitrary number of discrete frequencies     

Determination of the epitope of an inhibitory antibody to proliferating cell nuclear antigen

We identified an expansion of the CAG trinucleotide repeat in the coding region of the Machado-Joseph disease gene in 7 of 24 American families diagnosed with autosomal dominant ataxia. All affected individuals were heterozygous for an expanded allele that ranged from 67 to more than 200 CAG repeats, whereas the normal allele had 14 to 33 repeats. In contrast to the Azorean-Portuguese origins of Machado-Joseph disease, the two largest American families were of German and Dutch-African descent. Clinical, pathologic, and genetic evaluations suggest that American families with spinocerebellar ataxia type 3 differ from those with Machado-Joseph disease by their ethnic origins, predominant spinopontine atrophy, lack of dystonic features, and larger CAG repeat expansion.     

Application of polymerase chain reaction for the correlation of Salmonella serovars recovered from greyhound feces with their diet

The polymerase chain reaction was employed to correlate Salmonella serovars isolated from fecal material of greyhounds suffering from gastroenteritis with those isolated from the diet fed to the greyhounds prior to onset of diarrhea. Kennels around the Abilene, Kansas, area were contacted and supplied with materials needed to collect a portion of the diet each day. With the onset of diarrhea, the kennels were instructed to ship the fecal material and diet from the previous 10 days to the laboratory for testing. Forty-one fecal samples and corresponding diets were screened for Salmonella, Clostridium perfringens, Campylobacter jejuni, Staphylococcus aureus, Staphylococcus intermedius, and pathogenic (piliated) Escherichia coli by direct culture using standard procedures. The fecal material was also screened for coronavirus and parvovirus using electron microscopy. Thirty-five "normal" fecal samples were screened for all of the above mentioned microorganisms as a control. In addition, the fecal material was screened for E. coli verotoxins I and II and clostridial enterotoxins. A total of 61 Salmonella isolates were recovered from the 41 samples of feces and diet submitted for testing; 31 were recovered from the feces and 30 from the diet. Four Salmonella isolates were recovered from the normal fecal samples. Results obtained by PCR, plasmid profiles, antigenic analysis, and antibiogram profiles indicated that 16 of the 31 isolates recovered from the fecal material were the same strain as that recovered from the diet.     

Circular cross-polarization measurements on earth-space paths at 11,7 GHz

Rain and icecrystal depolarization measurements were made on earthspace paths at four locations across Canada using the circularlypolarized 11.7 GHz beacon transmission from the cts satellite. Results show that when rain is the dominant depolarization mechanism, crosspolarization discrimination (xpd)is statistically related to copolar attenuation (cpa)according to xpd =U?20 log cpa with U showing improvement with increasing elevation angle. Icecrystal depolarization events, with accompanying differential phase shifts as large as 20°, were also observed. An analysis separating these events from the data demonstrates that at 11.7 GHz icecrystal depolarization degrades xpd statistics by less than 1 dB at the small percentages of time.     

Symbol synchronization using signal samples and interpolation

A method for symbol synchronization using two unsynchronized signal samples per symbol is presented. Signal values between the sample points are calculated by interpolation and then processed digitally to find a suitable strobe point. The interpolated value at the strobe point is used for data detection or input to an equalizer. Simulations show that low variance timing estimates can be made for pulses with raised-cosine spectra degraded by quadratic delay distortion     

Diode-loaded dipole antenna modeling and design

A circuit model for a diode-loaded dipole electric field measurement probe which is valid for frequencies below 10 GHz is presented. Assumptions are made to allow linear analysis based on the Laplace transform method. Optimized design criteria for the probe are then developed, with the major considerations being large bandwidth, independence of temperature, and maximum output. Experimental measurements on a probe designed for operation between 1 and 1000 MHz and comparison with the theoretical results are presented     

Wavelet transforms for detecting microcalcifications in mammograms

Clusters of fine, granular microcalcifications in mammograms may be an early sign of disease. Individual grains are difficult to detect and segment due to size and shape variability and because the background mammogram texture is typically inhomogeneous. The authors develop a 2-stage method based on wavelet transforms for detecting and segmenting calcifications. The first stage is based on an undecimated wavelet transform, which is simply the conventional filter bank implementation without downsampling, so that the low-low (LL), low-high (LH), high-low (HL), and high-high (HH) sub-bands remain at full size. Detection takes place in HH and the combination LH+HL. Four octaves are computed with 2 inter-octave voices for finer scale resolution. By appropriate selection of the wavelet basis the detection of microcalcifications in the relevant size range can be nearly optimized. In fact, the filters which transform the input image into HH and LH+HL are closely related to prewhitening matched filters for detecting Gaussian objects (idealized microcalcifications) in 2 common forms of Markov (background) noise. The second stage is designed to overcome the limitations of the simplistic Gaussian assumption and provides an accurate segmentation of calcification boundaries. Detected pixel sites in HH and LH+HL are dilated then weighted before computing the inverse wavelet transform. Individual microcalcifications are greatly enhanced in the output image, to the point where straightforward thresholding can be applied to segment them. FROG curves are computed from tests using a freely distributed database of digitized mammograms.     

Statistics of differential rain attenuation on adjacent earth-space propagation paths

Forty hours of observations of the three-dimensional radar reflectivity structure of rain in the Montreal area were used to simulate the centimetre-wavelength attenuations occurring simultaneously over a multitude of earth-space propagation paths. The same data base had been used in a previous study which confirmed that the radar estimates of attenuation statistics are in good agreement with attenuation distributions measured independently by passive radiometers. Differences between the attenuations occurring simultaneously over pairs of paths to a common point at the ground were tabulated as a function of angular path separation, viewing direction, radio frequency, and system margin. These data are required for evaluating the possibility of interference at an earth station caused by a signal from an adjacent satellite. In this study, values of angular separation from 2 to 9 degrees, radio frequencies from 11 to 30 GHz, elevation angles from 5 to 30 degrees, and system margins from 2 to 10 dB were considered. It was found that the cumulative distributions of differential attenuation could be characterized effectively by the attenuation difference occurring during 1 % of the time that the carrier signal suffered some attenuation, but not an attenuation exceeding the system margin. It was also found that this characteristic differential attenuation could be expressed to good approximation as a simple analytical function of the system parameters.     

Copper‐Based Nanostructured Coatings on Natural Cellulose: Nanocomposites Exhibiting Rapid and Efficient Inhibition of a Multi‐Drug Resistant Wound Pathogen,A. baumannii,and Mammalian Cell Biocompatibility In Vitro

This paper describes a layer‐by‐layer (LBL) electrostatic self‐assembly process for fabricating highly efficient antimicrobial nanocoatings on a natural cellulose substrate. The composite materials comprise a chemically modified cotton substrate and a layer of sub‐5 nm copper‐based nanoparticles. The LBL process involves a chemical preconditioning step to impart high negative surface charge on the cotton substrate for chelation controlled binding of cupric ions (Cu²⁺), followed by chemical reduction to yield nanostructured coatings on cotton fibers. These model wound dressings exhibit rapid and efficient killing of a multidrug resistant bacterial wound pathogen, A. baumannii, where an 8‐log reduction in bacterial growth can be achieved in as little as 10 min of contact. Comparative silver‐based nanocoated wound dressings–a more conventional antimicrobial composite material–exhibit much lower antimicrobial efficiencies; a 5‐log reduction in A. baumannii growth is possible after 24 h exposure times to silver nanoparticle‐coated cotton substrates. The copper nanoparticle–cotton composites described herein also resist leaching of copper species in the presence of buffer, and exhibit an order of magnitude higher killing efficiency using 20 times less total metal when compared to tests using soluble Cu²⁺. Together these data suggest that copper‐based nanoparticle‐coated cotton materials have facile antimicrobial properties in the presence of A. baumannii through a process that may be associated with contact killing, and not simply due to enhanced release of metal ion. The biocompatibility of these copper‐cotton composites toward embryonic fibroblast stem cells in vitro suggests their potential as a new paradigm in metal‐based wound care and combating pathogenic bacterial infections.