Prediction of fatigue behaviour in stress-concentrators of arbitrary geometry

A new method is outlined which aims to predict high-cycle fatigue behavior of components which fail from stress-concentrators. This involves examination of the stress field in the vicinity of the stress-concentrator, and comparison with stress fields for cracks at known stress intensities. Methods which are currently used for simple notch geometries can thus be generalised, making the approach applicable to stress concentrators of any geometry. The method of prediction is shown to be stable, providing a solution of good accuracy when compared to analytical methods for standard specimen geometries. Favourable comparisons with experimental data have been achieved both for standard notches and for a corner geometry which represents a typical component case.     

795 nm and 1064 nm dual pump thulium-doped tellurite fibre for S-band amplification

Gain measurement in thulium-doped tellurite fibre is demonstrated with a maximum internal gain of 7 dB at 1480 nm. An improvement in gain by a factor of 2 is achieved using a 795 nm and 1064 nm dual pump scheme. Gain in tellurite fibres extends to longer wavelength than in fluorides, showing improved overlap with the C-band EDFA.     

On the possible role of positive end-expiratory pressure ventilation in the treatment of chylothorax caused by blunt chest trauma

Recent reports on the treatment of chylothorax postulate a benefit to ventilator therapy, especially using positive end-expiratory pressure (PEEP). This report describes the use of mechanical ventilation with PEEP in the management of a 24-year-old male motorcyclist who sustained a ligamentous Chance fracture of the thoracic spine at the T6-7 level with bilateral traumatic chylothorax. Treatment of the chylothorax consisted of high PEEP ventilation, bilateral chest tube thoracostomies, and total parenteral nutrition. The chylothoraces resolved within 4 days of treatment and mechanical ventilation was stopped. Ventilator therapy of traumatic chylothorax and the physiologic grounds for its use are discussed. A review of the literature and experimental evidence seem to suggest that ventilator treatment of traumatic chylothoraces is effective.     

Effects of antipsychotic treatment on polysomnographic measures in schizophrenia: a replication and extension

OBJECTIVE: The authors sought to replicate and extend previous observations of improvement in some EEG sleep measures during the course of antipsychotic treatment in schizophrenia patients. METHOD: Fourteen medication-free patients with schizophrenia underwent 2 nights of sleep EEG monitoring before and after 3-4 weeks of treatment with clinically determined doses of haloperidol or thiothixene. RESULTS: Measures of sleep continuity improved consistently. REM latency increased, although five of 14 patients continued to exhibit short REM latencies (less than 60 minutes). Stage 3 sleep increased during neuroleptic treatment, while stage 4 sleep did not change. CONCLUSIONS: These data demonstrate partial improvement of some but not all EEG sleep measures in schizophrenic patients through the course of neuroleptic treatment. They suggest that shortened REM latency and disturbed sleep continuity might represent reversible state abnormalities, while reduced slow-wave sleep may represent a more persistent trait abnormality in schizophrenia.     

Autonomic control of cardiovascular function: clinical evaluation in health and disease

The high- and low-pressure baroreceptor reflexes are integral to the control of blood pressure by the autonomic nervous system. Tests of the integrity of these baroreflexes make it possible to identify the site of autonomic dysfunction in patients with orthostatic hypotension. Clinical characteristics and typical results of autonomic testing in patients with autonomic failure, with carotid sinus hypersensitivity, and with hyperadrenergic autonomic dysfunction are described in this review.     

High-performance liquid chromatography determination of mycophenolic acid and its glucuronide metabolite in human plasma

Two HPLC-UV assays are reported here: one is a rapid assay for mycophenolic acid (MPA) and the other is a simultaneous assay for MPA and its metabolite mycophenolic acid glucuronide (MPAG). For both methods, plasma samples (500 microl) with added internal standard were acidified and extracted using C18 solid-phase extraction cartridges. Chromatographic separation was achieved on a C18 Novapak column using a mobile phase consisting of methanol-0.05% orthophosphoric acid (40:60, v/v) for the rapid MPA assay and 30:70 for the simultaneous MPA and MPAG assay. The assays were linear over the ranges 0.1 to 50.0 mg/l for MPA and 2.8 to 225.8 mg/l for MPAG. Mean absolute recovery for all analytes was >99%. These methods are suitable for therapeutic drug monitoring and pharmacokinetic studies.     

The influence of stereoisomerism on the pharmacokinetics of Tc radiopharmaceuticals

The influence of stereoisomerism on the pharmacokinetics of Tc mono-oxo complexes is reviewed. Tc(V) monooxo complexes formed with N/S ligands have four donor groups from the ligands in an equatorial plane; the oxo ligand coordinates in an axial position. Stereoisomerism in Tc (V) mono-oxo complexes can be centered within the ligand (carbon atom in the chelate ring or ligating nitrogen of amine donors) or at the Tc. The metal center becomes chiral when an equatorial ligand has a head and a tail (i.e., the two ends of the ligand differ). All types of stereocenters can produce significantly different pharmacokinetic profiles for individual isomers. Thus, biological evaluation of separated stereoisomers is necessary to identify the optimal sterochemical configuration, particularly for radiopharmaceuticals targeted to receptor molecules with low specificity. Because of interspecies variation, there is ultimately no substitute for human testing. Although it is possible that the increase in non-specific binding of agents incorporating L-vs D-amino acids may more than offset any increased receptor binding, much more information is needed. Stereochemical factors can also lead to unpredictable differences in coordination geometry and thermodynamic preference of a single isomer; thus chemical characterization of stereoisomers continues to be an important component of radiopharmaceutical development.     

Comparison of the resistance of C57BL/6 and C3H/He mice to infection with Mycobacterium paratuberculosis

Susceptibility of C57BL/6 (Bcgs) and C3H/HeN (Bcgr) mice to an intraperitoneal infection with Mycobacterium paratuberculosis strain 19698 was compared (by histopathology and the number of mycobacteria isolated from the spleen). Mycobacterial counts from the spleen of Bcgr mice progressively decreased over the course of infection but remained unchanged in Bcgs mice. Granulomatous lesions and acid-fast bacteria were consistently present in the liver and lymph nodes of Bcgs mice, whereas lesions were transient or absent in Bcgr mice. These results indicate that Bcgr mice are inherently resistant to M. paratuberculosis, whereas Bcgs mice are inherently susceptible. These differences may prove useful in elucidating the mechanisms of resistance and susceptibility to paratuberculosis and other mycobacterial infections.