Effects of passive tilt and submaximal exercise on spectral heart rate variability in ventricular fibrillation patients without significant structural heart disease

It has been shown that tilt and exercise elicit significant changes in autonomic activity in normal subjects and that submaximal exercise causes a greater reduction in heart rate variability (HRV) in animals susceptible to ventricular fibrillation (VF). Whether there is an abnormal HRV response to tilt and exercise in patients at risk of sudden cardiac death (SCD) remains unknown. Short-term HRV before and during passive tilt and exercise was studied in 12 survivors of out-of-hospital cardiac arrest with documented VF and compared with 12 age- and sex-matched normal controls. No patient had significant structural heart disease or left ventricular dysfunction. HRV was computed as total-frequency (TF, 0.01 to 1.00 Hz), low-frequency (LF, 0.04 to 0.15 Hz) and high-frequency (HF, 0.15 to 0.40 Hz) components. There was no significant difference between normal controls and SCD survivors in HRV before or during tilt or submaximal exercise testing. The HF component was significantly decreased during tilt compared with that in the supine position in both normal controls (5.85 +/- 0.61 vs 5.08 +/- 0.95 In(msec2), p = 0.005) and patients (5.58 +/- 1.49 versus 4.74 +/- 1.18 In(msec2), p = 0.003). There was again no significant change in the TF or LF components during tilt in either patients or controls. All frequency components were significantly decreased during submaximal exercise testing in both patients and controls. However, there was no significant difference in any of these tilt- and exercise-induced changes in HRV between normal controls and SCD survivors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nitrone spin-traps block calcium channels and induce pulmonary artery relaxation independent of free radicals

Free radicals react with nitrones to form stable nitroxides which can be identified by ESR spectroscopy. Unfortunately, little is known regarding the pharmacological properties of these compounds. In this study, three commonly used nitrones, 5,5-dimethylpyrroline-N-oxide (DMPO), alpha-phenyl-tert-butylnitrone (PBN), and alpha-(4-pyridyl 1-oxide)-N-tert-butylnitrone (POBN), were found to induce relaxation of preconstricted isolated rat pulmonary artery rings. Additional experiments with PBN indicated that vasorelaxation could not be attributed to production of endothelial derived factors, prostaglandins, or free radicals. Patch-clamp techniques revealed reversible calcium channel blockade with PBN at a concentration below that needed to detect free radicals. Calcium channel blockade probably accounts for the vasorelaxation observed in the isolated ring preparations described here, and should be considered when using nitrone spin-traps both in in vivo and clinical studies.     

A patient's perspective on the management of peptic esophageal stricture: experience and results in 113 consecutive cases

A retrospective analysis of 113 consecutive cases of benign esophageal stricture, all secondary to gastroesophageal reflux, 100 treated conservatively, 13 treated surgically, has been carried out in conjunction with a postal questionnaire of patients. Patients were requested to grade both their swallowing ability and the acceptability of their treatment. Of those responding to questionnaire, 88% of patients treated conservatively found their treatment acceptable or better, and 72% were left with either no or minimal restriction of diet. There was no correlation between either the total number or frequency of dilatations and the result achieved. Similarly, patient satisfaction appears largely independent of these variables. Doctors should be wary of taking recurrence of a stricture after initial dilatation as indicating a poor eventual outcome or a dissatisfied patient. There was no difference in terms of either the result or patient satisfaction between conservatively treated and surgically treated patients.     

Radar detection of low-altitude targets in a maritime environment

Results from a unique analytical and experimental effort to assess low-altitude, short-range, radar detection capabilities in an evaporation ducting environment are presented. Within the horizon, the duct may shift the location of the last interference null several kilometers in range, which may cause nondetection at ranges where detection is expected and detection at ranges where detection is not expected. In addition, the evaporation duct may reduce the signal strength at ranges near the last interference peak so that detection of low-altitude, small-size, targets may not be possible until the target is much closer. At ranges near and beyond the horizon, radar signal strength depends both on the surface layer and on the mixed layer. To accurately model propagation in this region, knowledge of both surface layer and upper air meteorology Is required. An empirical model to merge the surface layer with the mixed layer has been developed. Comparisons of measured to calculated detection range indicate that the assumption of a standard atmosphere minimizes the variance of the difference between the detection ranges whereas ranges calculated using the measured surface meteorological conditions and a modified surface layer model minimizes the median of the difference     

Determination of the short-range order structure of Au-25 At. Pct Fe using wide-angle diffuse synchrotron X-Ray scattering

The short-range order (SRO) structure of a Au-25 at. pct Fe single crystal was studied using wide-angle diffuse synchrotron X-radiation scattering at room temperature. Two heat treatments were investigated: a 400 °C aging treatment for 2 days and a 440 °C treatment for 5 days, both preceded by solution treatment in the single-phase field and water-quenched to room temperature. Evolution of the SRO structure with aging was determined by fitting the two sets of Cowley-Warren (C-W) SRO parameters to a pair of 140,608-atom models. The microstructures, although quite disordered, showed a trend with aging for an increasing volume fraction of an Fe-enriched and an Fe-depleted environment. The Fe-enriched environment displayed a preference for Fe segregation to the {110} and {100} face-centered cubic (fcc) matrix planes. A major portion of the Fe-depleted environment was found to contain elements (and variations of these elements) of the Dl_a ordered superstructure. The SRO contained in the Fe-depleted environment may be best described in terms of the standing concentration wave packet (SCWP) model. This study provides, for the first time, a quantitative real-space view of the atomic arrangements, which make up both environments in the SRO structure of Au-25 at. pct Fe. Formerly Graduate Research Assistant, University of Illinois, Urbana, IL.     

A new method for approximation of physiological signals

A new robust method for the approximation of physiological signals is proposed. The noise must satisfy only one condition: that the probabilities for positive and negative values are equal. The authors' results illustrate that the proposed method provides a more accurate approximation of signals than either the least square error or the least absolute deviation method in cases that include unknown noise density     

Stereological estimation of the total volume of MR visible brain lesions in patients with multiple sclerosis

Point counting represents a convenient and efficient technique for estimating the area of transects through multiple sclerosis (MS) lesions on magnetic resonance (MR) images obtained for sections through the brain. When sectioning has been performed according to the Cavalieri method, unbiased estimates of the total volume of MR-visible MS plaques can be obtained with a precision of 3–5% in 5–10 min.     

Photoelectrocatalytic humic acid degradation kinetics and effect of pH,applied potential and inorganic ions

This study addresses the removal of humic acid (HA) dissolved in an aqueous medium by a photoelectrocatalytic process. UV₂₅₄ removal and the degradation of color (Vis₄₀₀) followed pseudo‐first order kinetics. Rate constants were 1.1 × 10^?1 min^?1, 8.3 × 10^?2 min^?1 and 2.49 × 10^?2 min^?1 (R² > 0.97) for UV₂₅₄ degradation and 1.7 × 10^?1 min^?1, 6.5 × 10^?2 min^?1 and 2.0 × 10^?2 min^?1 for color removal from 5 mg dm^?3, 10 mg dm^?3 and 25 mg dm^?3 HA respectively. Following a 2 h irradiation time, 96% of the color, 98% of the humic acid and 85% of the total organic carbon (TOC) was removed from an initial 25 mg dm^?3 HA solution in the photoanode cell. Photocatalytic removal on the same photoanode was also studied in order to compare the two methods of degradation. Results showed that the photoelectrocatalytic method was much more effective than the photocatalytic method especially at high pH values and with respect to UV₂₅₄ removal. The effect of other important reaction variables, eg pH, external potential and electrolyte concentration, on the photoelectrocatalytic HA degradation was also studied. Copyright © 2003 Society of Chemical Industry