Analysis of conjugated bile acids by high performance liquid chromatography and mass spectrometry

Because of the known advantages of coupling high performance liquid chromatography with mass spectrometry (HPLC-MS) in biological fluids, studies on the reversed-phase HPLC-MS system for direct analysis of conjugated bile acids in human bile samples are described. Ten samples of gallbladder bile of apparently healthy subjects were examined. The amounts of each tauro- and glycoconjugated bile acid as trifluoracetate were determined by mass fragmentography. Quantitation of at least 1 ng of each bile acid was possible.     

The lung in AIDS]

The aim of this study was to underline the important role played by respiratory tract pathologies in HIV-infected subjects and to evaluate the incidence of respiratory pathologies in HIV-positive subjects in the province of Cosenza. After examining recently reported data, the authors analyse the patients studied by the Infectious Disease and Pneumology Divisions of the United Hospitals of Cosenza with the collaboration of the Virology Unit over the two-year period 1992-1994. As well as the lower incidence of HIV infection in this area compared to the rest of Italy, the paper highlights the reduced percentage of concomitant respiratory pathologies. The authors attempt to interpret the significance of these results.     

Lyme disease in outdoor workers on Assateague Island: high tick-exposure but low disease risk

Endothelin-1 (ET-1)-converting enzyme (ECE) activity in the human serum lipoprotein fraction was studied using a sensitive enzyme immunoassay and reverse-phase high performance liquid chromatography. The ECE activity of cleaving synthetic human big ET-1 into ET-1 by the serum lipoprotein fraction was about 14-times greater than that by whole serum, and the activity was closely associated with lipoprotein itself. The lipoprotein ECE activity, which was optimal at pH 7.0, was inhibited by EDTA, o-phenanthroline, phosphoramidon, thiorphan, phenylmethanesulfonyl fluoride and chymostatin, but not by cysteine or aspartic proteinase inhibitors, suggesting metalloproteinase- and chymotrypsin-like properties. These results suggest that the serum lipoprotein ECE may be involved in the processing of big ET-1 to ET-1 in the circulatory system.     

Polyolefin blends

Morphology observations, differential scanning calorimetry investigations and mechanical tensile tests have been performed on blends based on isotactic polypropylene and high-density polyethylene, containing ethylene-propylene (EP) copolymers of different composition. The blends after melting have been crystallized at low undercoolings (T _c=126 and 110° C, respectively). All the properties strongly depend on the EP composition, indicating a marked interaction between the C₂ or C₃ sequences in the copolymers and the two matrices. These features are compared with those observed in previous work for the same blends crystallized at high undercoolings (quenched in water). Some relevant differences with respect to the crystallization procedures used and to the resulting structures in the blends are discussed.     

Vibration analysis of coupled fluid-structure systems: A convenient computational approach

The mathematical model implemented in the ZERO code for dynamic analysis of thin axi-symmetric structures coupled with fluid, is briefly described. The numerical experimentation presented is aimed at evaluating the efficiency of the method applied for computation of vibration characteristics of the coupled system.     

I. Segregation of Active Constituents from Tablet Formulations During Grinding: Theoretical Considerations

The preparatory step in the analysis of active drugs in tablet dosage forms has generally consisted of the grinding or milling of a given number of the tablets into a uniformly composited powder. Since the advent of content uniformity testing (individual tablet analysis) where the compositing step is bypassed, numerous reports have cited the large percentage difference in results observed between the average composited assay value and the average assay value for the individual tablets.

This paper describes some of the factors responsible for these observed differences, as well as some of the causative events that develop during tablet grinding. Certain active constituents become separated from other tablet components during grinding because of differences in the size, shape, density, surface roughness, and resilience of their particles. At particle sizes of less than approximately 400 µm additional forces and mechanisms, namely Van der Waals forces, electrostatic forces, adsorption, and valency forces, become significant.     

Detection of Salmonella in dry foods using refrigerated pre-enrichment and enrichment broth cultures: summary of collaborative study

A collaborative study was conducted to compare the productivity of refrigerated pre-enrichment and enrichment broth cultures with the U.S. Food and Drug Administration culture methods for detection of Salmonella. The refrigerated pre-enrichment and selective enrichment broth culture methods for detection of Salmonella in dry foods have been adopted first action by AOAC INTERNATIONAL.     

Robust optimum design of tuned mass dampers for high‐rise buildings under moderate earthquakes

In the present study the optimum design of tuned‐mass‐damper (TMD) devices used for the vibration control of high‐rise buildings subject to moderate earthquakes is developed. For these structures a large acceleration demand can produce damage in equipment and contents: therefore, the performance of TMD will be based on the capacity of reducing this structural response. In order to maximize the performance and the efficiency of the TMD strategy, the ratio between the absolute accelerations of the protected and of the unprotected systems is assumed as objective function in the optimum design. The method is carried out in a stochastic way and a stationary‐filtered stochastic process is assumed to model the seismic action. Since the main disadvantage of using a single TMD is the mistuning related to errors in the evaluation of the natural frequency of the main structure, an uncertainty is introduced for this structural parameter, which is modelled as a random variable. Uncertainties in other structural mechanical properties and in TMD are neglected. Copyright © 2008 John Wiley & Sons, Ltd.