Fast detection of instability in sigma-delta modulators based on unstable embedded limit cycles

As a sequel to a previous study (Wong and Ng) on the nonlinear dynamical behavior of low-pass, high-order (order > 2), single-bit /spl Sigma//spl Delta/ modulators with distinct unit-circle noise transfer function zeros, this paper proposes a novel scheme for the fast detection of unstable operation in these modulators under general time-varying input. The scheme is based on the variation of unstable embedded limit-cycle fixed points (which form the bounds beyond which the modulator becomes unstable) versus modulator input amplitude. Deployment of the detection scheme requires simple analog components with possible simplification. The effectiveness of the scheme is demonstrated with numerical examples.     

Hydroxyzine inhibits neurogenic bladder mast cell activation

OBJECTIVES: Increased numbers of activated mast cells have been documented close to substance P (SP) containing nerve endings in the bladders of patients with interstitial cystitis (IC), a painful, sterile bladder disorder occurring primarily in females. Many of these patients also suffer from allergies, but common antihistamines do not help. In line with the fact that IC symptoms worsen under stress, we recently showed that bladder mast cells could be activated by the stable acetylcholine (Ach) analogue carbachol and by immobilization stress. Preliminary data from open label studies indicated that the heterocyclic histamine-1 receptor antagonist (H-1r alpha) hydroxyzine reduces IC symptoms. We, therefore, investigated whether hydroxyzine could inhibit carbachol-induced bladder mast cell activation. METHODS: Bladder pieces from male Sprague-Dawley rats were perfused with 10(-5) M carbachol, 10(-5) M SP, or 100 microg/ml compound 48/80 (C48/80), with or without preincubation with the designated concentrations of the H-1r alpha. Mast cell activation was assessed by release of exogenous 3H-serotonin and morphological evidence of secretion by light microscopy. RESULTS: Carbachol at 10(-5) M triggered rat bladder mast cell serotonin release which represented a 65% increase over control. Equimolar concentrations of SP caused a 32% increase, while C48/80 had no effect. The heterocyclic piperazine H-1r alpha hydroxyzine reduced carbachol-induced serotonin release by 25% at 10(-6) M and 34% at 10(-5) M, both of which were statistically significant (P < 0.05). On the contrary, the well known H-1r alpha diphenhydramine had no inhibitory effect, while the mixed H-1r alpha and 5-hydroxytryptamine-receptor antagonist (5-HTr alpha) azatadine actually caused an 11% increase. CONCLUSION: Hydroxyzine reduced carbachol-induced serotonin release from rat bladder in vitro through a mechanism which was unrelated to its H-1 receptor antagonistic properties. The ability of hydroxyzine to inhibit bladder mast cell activation by neurogenic stimuli along with its anticholinergic, anxiolytic and analgesic properties, may explain the clinical efficacy of this drug in reducing IC symptoms. Other, nonsedating, hydroxyzine analogues able to inhibit bladder mast cell activation may provide potentially new therapeutic approaches for IC.     

Accuracy of the conductance catheter for measurement of ventricular volumes seen clinically: effects of electric field homogeneity and parallel conductance

Ultrasound returns from tissue display variations in amplitude on several spatial scales. Although large-scale variations result from factors such as attenuation, variations on smaller scales are caused by tissue characteristics such as variations in scatterer spacing and reflectance. These small scale variations cause a corresponding variation in the amplitude of the ultrasound return. A simple and direct method for detecting and quantifying periodicity in these variations in the presence of attenuation is described. The radiofrequency ultrasound return is first demodulated by full-wave rectification. The normalized power spectrum of the demodulated return then yields an index that we call the relative Fourier energy. Both computer simulations and in vitro experiments were performed in order to study how relative Fourier energy performed in discriminating between periodic and random scatterer distributions. Computer simulations demonstrated significant differences between the returns from periodic and random scatterer distributions. Ultrasound returns from aortic tissue yielded a relative Fourier energy index that was significantly different between normal vs. atherosclerotic tissue (normal: 0.868 +/- 0.076, mean +/- s.d., fibrofatty plaque: 0.705 +/- 0.109, p < 0.01 vs. normal, calcified plaque: 0.753 +/- 0.078, p < 0.01 vs. normal). In contrast, no difference was found in comparisons of overall reflectance.     

Preferential dissemination of B-cell gastric mucosa-associated lymphoid tissue (MALT) lymphoma to the splenic marginal zone

The tendency for gastric mucosa-associated lymphoid tissue (MALT) lymphoma cells preferentially to localize around reactive B-cell follicles, both in the mucosa and regional lymph nodes, coupled with their immunophenotype, has led to the proposal that the normal cell counterpart of this lymphoma is the marginal zone B cell. In keeping with this proposition, lymphocytes expressing the lymphoma idiotype have been detected in the splenic marginal zone in a single case of gastric MALT lymphoma. To confirm that this truly represented preferential homing of MALT lymphoma to the splenic marginal zone, we have now re-examined this case, together with 17 other cases, using both immunohistochemical and molecular methods in an attempt to establish clonal identity between the gastric lymphoma and cells in the splenic marginal zone. In three cases, the spleen was characterized by marked expansion of marginal zones by cells showing the same pattern of Ig light chain restriction as the gastric lymphoma. None of the remaining 15 cases showed histologic evidence of lymphomatous infiltration. Analysis of the Ig genes by polymerase chain reaction (PCR), cloning, and sequencing confirmed clonal identity between the splenic marginal zone infiltrates and the gastric lymphoma in the histologically involved cases. Amplifiable DNA could be extracted from only 5 of the remaining 15 cases. In 3 of these cases, including the case previously studied using an anti-idiotype, involvement of the splenic marginal zone could be confirmed using microdissection and clone-specific PCR. No involvement could be detected in the remaining 2 cases. In addition, we have shown that mucosal addressin cell adhesion molecule-1 (MAdCAM-1), the primary homing receptor of gut-mucosa for lymphocytes, was strongly expressed by the sinus lining cells of the splenic marginal zone. These results provide strong evidence for preferential involvement of the marginal zone when gastric MALT lymphomas disseminate to the spleen, which is in keeping with the notion that the marginal zone B cells are the normal counterparts of MALT lymphoma cells.     

A self-steered array system for microwave communications

The paper presents a self-steered algorithm that can be used to correct pointing errors in microwave communications. The algorithm is based on the fact that the output power of an optimized beamformer achieves a local maximum if the steering vector coincides with that of the desired signal, as long as the interferences are outside the mainbeam. By approximating the steering vector by its first-order Taylor series expansion in terms of the steering angles, the maximization process reduces to a two-dimensional optimization problem. Numerical results are presented to illustrate the performance achievable     

A novel hot carrier reliability monitor for LDD p-MOSFETs

The gate-edge shape of an LDD p-MOSFET exhibits large influences upon the hot carrier induced degradation and its performances. It is observed that the gate-to-drain tunneling current is strongly correlated to the reentrant gate oxide thickness and to the device degradation. A simple model is then constructed to provide an explanation for the observation. Under the tunneling current measurement conditions, a thicker oxide at the gate-edge leads to a weaker peak electric field in the p-LDD and to a lower gate-to-drain current. On the other hand, under the hot carrier stressing conditions, the thicker oxide decreases the oxide electric field and thus suppresses the hot electron injection. The observed correlation can be employed to monitor the process induced gate-edge (overlap) variation.     

Irrelevant information in probabilistic categorization.

Using a probabilistic category learning paradigm, 6 experiments explored irrelevant information and 4 current models. Utilization of relevant configural information was lowered by the presence of an irrelevant dimension, both if that was the only relevant information and if a dimension was also relevant. An irrelevant cue value lowered the utilization of relevant cue values. An additional relevant dimension had a larger degrading effect on the utilization of a relevant dimension than an additional irrelevant dimension, thereby suggesting that the effect of irrelevant information is due to the complexity of the environment rather than to factors particular to the irrelevant nature of the information. The current models failed to fit the findings. However, results showing that memory errors account for salience effects provide a direction for revising one of the models. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Release of interleukin-12 in experimental Escherichia coli septic shock in baboons: relation to plasma levels of interleukin-10 and interferon-gamma

Interleukin (IL)-12 is thought to be a key factor for the induction of interferon gamma (IFN-gamma), a cytokine essential for the lethal effects of endotoxin. We report here on the release of the nonfunctional subunit of IL-12, p40, as well as biologically active heterodimeric IL-12, p70, after administration of a lethal (n = 5) or sublethal (n = 8) dose of live Escherichia coli to baboons. Remarkably, on lethal challenge, peak levels of p40 were observed at 3 hours that were about twofold lower than those elicited after sublethal challenge (2,813 +/- 515 pg/mL v 4,972 +/- 732 pg/mL, P < .05). This disparity was also observed, although to a lesser extent, for IL-12 p70 antigen, of which maximum levels of 91 +/- 47 pg/mL and 151 +/- 41 pg/mL were measured 6 hours after a lethal or sublethal dose of E coli, respectively. Circulating p70 antigen correlated with IL-12 biologic activity (r = 0.869; P < .001). When comparing lethal to sublethal conditions, lower peak levels of IL-12 on lethal E coli sharply contrasted with higher levels of other proinflammatory cytokines, such as tumor necrosis factor (TNF)-alpha, IL-1beta, IL-6, and IL-8 observed in these animals. Lower IL-12 concentrations in the lethal group may have resulted in part from the enhanced production of IL-10, a known inhibitor of IL-12 synthesis in vitro, as peak levels of this cytokine 3 hours postchallenge inversely correlated with peak levels of IL-12, in particular p40 (r = -0.802; P < .01). Contrary to what might be expected if IFN-gamma were solely induced by IL-12, lethally challenged baboons generated threefold more IFN-gamma at 6 hours than those receiving a sublethal dose (P < .05). Moreover, higher levels of IFN-gamma were associated with lower p40/p70 ratios, suggesting that, in agreement with observations in vitro, IFN-gamma may have preferentially upregulated the release of p70 over p40. These data show that IL-12 is released in experimental septic shock in nonhuman primates and suggest that IL-10 and IFN-gamma are involved in the regulation of this release. Furthermore, this study indicates that the systemic release of IL-12 might be essential, but is not likely sufficient, to promote lethal production of IFN-gamma in sepsis.