Effects of cavities on monopole antenna current distribution and decoupling from mounting structure

The effects of cavities located near the base of a ground plane-mounted coax-driven monopole antenna are investigated. The cavities are either embedded in the tubular antenna itself or in the region below the conducting surface. Coupled integral equations are formulated and solved to determine the distribution of current on the structure. Two primary functions of the cavities are discussed. 1) At certain frequencies the input impedance of the cavity is infinite and the current at the base of the antenna is forced to zero. A single structure may contain several cavities, each cavity having unique resonant frequencies. It is demonstrated that superposition of these cavities may provide multiple resonant frequencies within a large frequency band. The utility of base cavities in the design of an antenna that is decoupled from the ground plane on which it is mounted is discussed. 2) Regardless of frequency, the cavities affect the distribution of current on the structure and, concomitantly, the standing wave ratio and gain of the antenna. The cavities are shown to be efficient and physically-rigid tools for current-shaping and tuning coax-fed antennas. Results computed from solutions of the coupled integral equations are compared with those from physical measurements.     

Radiation loss of grating-assisted directional couplers using the Floquet-Bloch theory

The Floquet-Bloch theory (FBT) is used to determine the radiation loss of a grating-assisted directional coupler. Improper waves obtained by FBT represent leakage and produce radiation loss along the transverse direction. By summing the fields of all leaky harmonics, the power flow radiated into the superstrate and substrate can be calculated from Poynting's theorem. However, the locations at which these summations occur impact the accuracy. An analytic formula for radiation loss is also derived. Results from both the FBT and the analytic formula are compared with results obtained using the coupled-mode theory.     

Predicting Addiction Severity Index (ASI) interviewer severity ratings for a computer-administered ASI.

The Addiction Severity Index (ASI) is a reliable and valid measure of problem severity among addicted patients. Concerns have been raised about the reliability of the Interviewer Severity Rating (ISR), a summary score for each of 7 domains. As part of an effort to build a computer-administered ASI, regression equations were developed to predict the ISR. Repeated resampling of a large dataset, consisting of 1,124 ASIs conducted by trained interviewers, permitted derivation of stable regression equations predicting the ISR for each ASI domain from patients' answers to preselected interview items. The resulting 7 Predicted Severity Ratings (PSRs) were tested on 8, standardized vignettes, with "gold standard," expert-generated ISRs. Reliabilities compared well with those of intensively trained interviewers. The PSRs could provide an alternative to potentially unreliable interviewer ratings, enhancing the ASI's role in treatment planning and treatment matching and make possible a computer-administered version of the ASI. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age- and gender-related elastin distribution changes in human vocal folds

To elucidate the mechanism of gut hypertrophy observed in rats artificially reared (AR) on milk formulas, the effects of four refined formulas with different ratios of casein (C) and whey protein (W), CW 2:8, CW 4:6, CW 6:4 and CW 8:2, on the gut growth of AR rats were examined. Four groups of pups were infused with each formula through an intragastric cannula from age 5 to 15 days. Each of the four milk formulas showed a different character in the stomach, such as no curd, very soft curd, soft curd and hard curd, in response to an increasing ratio of C:W. There were no significant differences in body weight gain among the AR groups and mother-reared (MR) controls. The stomach growth, in weight, of AR rats increased in response to the increasing ratios of C:W. In comparison with MR controls, hypertrophy of the stomach of AR rats appeared within the formulas with higher proportions of casein than whey protein (CW 6:4 and CW 8:2), but not those with lower proportions (CW 2:8 and CW 4:6). The growth of the small intestine was also related to the increasing ratio of C:W in the formulas. A similar pattern of hypertrophy in the hindgut was seen in AR rats. There was no association between hypertrophy of the gut in AR rats and plasma triiodothyronine. The present results clearly demonstrated that the gut growth of AR rat pups was directly influenced by the diet but not by AR per se, and that hard casein-curd in the stomach might be one cause of gut hypertrophy.     

Rolandic type cerebral palsy in children as a pattern of hypoxic-ischemic injury in the full-term neonate

Magnetic resonance images (MRIs) of the brains of 11 patients aged from 1 week to 12 years with a distinctive type of cerebral palsy were selected based on distribution of cerebral lesions, which were restricted to bilateral perirolandic cortical and subcortical regions, including frequent symmetric involvement of basal ganglia and ventrolateral nucleus of thalami. Retrospectively, the perinatal history and clinical features were reviewed to correlate clinical data with this distinctive pattern of brain injury. Clinically affected neonates had an encephalopathy associated with a severe perinatal asphyxial event. Older children with cerebral palsy survived a similar perinatal course and demonstrated spastic quadriparesis with bulbar or pseudobulbar involvement, lack of verbal speech and variable delays in cognitive development. The distribution of hypoxic-ischemic lesions involving bilateral perirolandic regions, basal ganglia, and thalami, appears to correlate with increased metabolic areas of primary myelination in full-term neonates, but not with arterial border zones nor a single cerebral artery distribution. Myelination is a critical process in maturing brain associated with marked increase in tissue respiration and thus greater susceptibility to oxygen deprivation. It is believed that the extent of hypoxic-ischemic brain injury is determined principally by brain maturity and regional metabolic rates at time of insult and this correlates with active myelination in full-term neonates. This study confirms previous data from neuropathologic literature and recent reports of neuroimaging studies of asphyxiated neonates. In addition, retrospective analysis of the clinical data enables recognition of a type of cerebral palsy that might be the hallmark of hypoxic-ischemic injury in term neonates.     

Antithrombins Wibble and Wobble (T85M/K): archetypal conformational diseases with in vivo latent-transition, thrombosis, and heparin activation

The inherent variability of conformational diseases is demonstrated by two families with different mutations of the same conserved aminoacid in antithrombin. Threonine 85 underlies the opening of the main beta-sheet of the molecule and its replacement, by the polar lysine, in antithrombin Wobble, resulted in a plasma deficiency of antithrombin with an uncharacteristically severe onset of thrombosis at 10 years of age, whereas the replacement of the same residue by a nonpolar methionine, antithrombin Wibble, gave near-normal levels of plasma antithrombin and more typical adult thromboembolic disease. Isolated antithrombin Wibble had a decreased thermal stability (Tm 56.2, normal 57.6 degreesC) but was fully stabilized by the heparin pentasaccharide (Tm 71.8, normal 71.0 degreesC), indicating that the prime abnormality is a laxity in the transition of the main sheet of the molecule from the 5- to 6-stranded form, as was confirmed by the ready conversion of antithrombin Wibble to the 6-stranded latent form on incubation. That this transition can occur in vivo was shown by the finding of nearly 10% of the proband's plasma antithrombin in the latent form and also, surprisingly, of small but definitive amounts of latent antithrombin in normal plasma. The latent transition will be predictably accelerated not only by gross mutations, as with antithrombin Wobble, to give severe episodic thrombosis, but also by milder mutations, as with antithrombin Wibble, to trigger thrombosis in the presence of other predisposing factors, including the conformational stress imposed by the raised body temperatures of fevers. Both antithrombin variants had an exceptional (25-fold) increase in heparin affinity and this, together with an increased inhibitory activity against factor Xa, provides evidence of the direct linkage of A-sheet opening to the conformational basis of heparin binding and activation.     

The infeasibility of quantifying the reliability of life-criticalreal-time software

This work affirms that the quantification of life-critical software reliability is infeasible using statistical methods, whether these methods are applied to standard software or fault-tolerant software. The classical methods of estimating reliability are shown to lead to exorbitant amounts of testing when applied to life-critical software. Reliability growth models are examined and also shown to be incapable of overcoming the need for excessive amounts of testing. The key assumption of software fault tolerance-separately programmed versions fail independently-is shown to be problematic. This assumption cannot be justified by experimentation in the ultrareliability region, and subjective arguments in its favor are not sufficiently strong to justify it as an axiom. Also, the implications of the recent multiversion software experiments support this affirmation