Separation and purification of methadone enantiomers by continuous- and interval-flow electrophoresis

Continuous- or free-flow electrophoresis is based upon a thin film of fluid flowing between two parallel plates. The electrolytes and the sample are continuously admitted at one end of the electrophoresis chamber and are fractionated by an array of outlet tubes at the other. Using the Octopus apparatus in a horizontal position, continuous preparative separation of methadone enantiomers in the presence of (2-hydroxypropyl)-β-cyclodextrin as a chiral selector was investigated under conditions of continuous-flow zone electrophoresis and continuous-flow isotachophoresis. The enantiomeric composition of methadone in the collected fractions was assessed by chiral capillary electrophoresis and circular-dichroism spectroscopy. In both electrophoretic modes, partial separation of the two enantiomers with an enrichment of about 80% and a throughput of 10-20 mg of racemic methadone per hour was obtained. Operating the Octopus apparatus with interrupted buffer flow during electrophoresis, a process termed interval-flow electrophoresis, resulted in complete separation of milligram quantities of the two methadone enantiomers. Furthermore, commencing with racemic methadone, continuous multistage isotachophoretic processing is shown to be suitable to purify (R)-(-)-methadone, the enantiomer with higher pharmacological activity, on a mg/h scale and at a mM concentration in the collected product stream.     

On the impact of TiN film thickness variations on the effective work function of poly-Si/TiN/SiO/sub 2/ and poly-Si/TiN/HfSiON gate stacks

The impact of TiN film thickness variations on the effective work function (WF) of poly-Si/TiN/SiO/sub 2/ and poly-Si/TiN/HfSiON interfaces has been investigated. The electrical signatures of these gate stacks indicate that the concentration of Hf-Ti and Ti-Si bonds at the (poly-Si/TiN)/HfSiON and (poly-Si/TiN)/SiO/sub 2/ interface plays a significant role on the control of the gate stacks' WF. The density of these interfacial bonds and the related work function changes are correlated to the degree of nucleation of the TiN film on the dielectric.     

Bandwidth limitations of two-colour diode lasers for direct terahertz emission

The accessible bandwidth for tunable terahertz (THz) emission directly out of a diode laser is analysed in terms of gain bandwidth and semiconductor nonlinearities.     

Small-dose hyperbaric versus plain bupivacaine during spinal anesthesia for cesarean section

In a double-blind, randomized trial, 98 parturients undergoing cesarean section received either hyperbaric or plain bupivacaine 6.6 mg combined with sufentanil 3.3 microg as part of a combined spinal-epidural procedure. To prevent hypotension, 1000 mL of lactated Ringer's solution, 500 mL of hydroxyethyl starch 6%, and ephedrine 5 mg were administered i.v. The height of the block was equal in both groups, but more patients in the plain group had blocks that were either too high or too low (P < 0.01). The number of patients requiring epidural supplementation was equal in both groups. Strict criteria were used to treat hypotension. The overall incidence of systolic blood pressure (<90 mm Hg) was 13%, whereas it was more pronounced in the plain group (21% vs 6% in the hyperbaric group, P < 0.05), which required more ephedrine (P < 0.05) and in which a greater incidence of nausea was noticed (P < 0.05). We conclude that the use of a small dose of intrathecal bupivacaine combined with sufentanil plus our described preloading regimen resulted in a lower incidence of hypotension. Further, we conclude that the use of hyperbaric bupivacaine in this manner provides a more reliable block and a lower incidence of hypotension than plain bupivacaine. Implications: A small dose of hyperbaric bupivacaine 0.5% combined with sufentanil used intrathecally during cesarean section offered a more reliable cephalad spread of the spinal block than the glucose-free combination, which was reflected in a lower incidence of hypotension and nausea.     

Blood relationship

In every-day medical practice, blood relationship of spouses hardly ever play an important part. Mainly for genetic counselors and pediatricians the question of consanguinity of a child's parents arises when either a rare, often hereditary, disorder is diagnosed for the first time in a family, or potential parents want information on the risk for hereditary diseases. A probability calculus based on the corresponding hereditary factors of the joint ancestors establishes how likely homozygotes for hereditary diseases among the offspring of [blood]-related spouses - often cousins of the first or second degree - is. Furthermore, proof of the parents' consanguinity may explain a child's unexpected hereditary disease [especially autosomal recessive disorders] and, at the same time, it means a higher risk of repetition for the affected child's desired siblings. Incest represents a special form of genetic risk; this question arises either in connection with the adoption of a child, which was conceived by an incestuous couple, or with such a child's own family planning later on. Even the parents' descent from an ethnically, politically, religiously or linguistically isolated background may gave a similar impact on the appearance of hereditary disorders: an accumulation of rare genes has to be taken into account; factors causing disorders have to be expected among these genes, too. In the following, all major aspects of the situations described above will be given in detail.     

Die Bestimmung von Schwefelanteilen im Stahl unter 10 μg/g

Analytische Möglichkeiten einer neuen Gerätegeneration. Weiterentwicklung des Verfahrens mit synthetischer Eichung bis zur Bestimmungsgrenze 2 μg/g.     

Adrenal lesions in calves dying from endotoxin shock, with special reference to the Waterhouse-Friderichsen syndrome

The influence of hypoxemia on the brain content of several organic acids and NH+4, AND ITS RELATIONship to the accompanying hypocapnia was studied in unanesthetized rats subjected to hypoxemia for periods ranging between 2 hours and 7 days. Under acute conditions, 'mild' hypoxemia (FO2 = 6--7%), these increases were greater and accompanied by increased gamma-aminobutyric acid (GABA) and decreased glutamic and aspartic acid levels; glutamine and NH+4 remained normal. When hypocapnia was prevented, 'severe' hypoxemia induced only a rise in GABA and slight elevations in lactic and alpha-ketoglutaric acid. During prolonged severe hypoxemia, the effects on the brain amino acids were maintained throughout, indicating that they are independent from the intracerebral pH which should progressively normalize. The effect on lactic acid gradually disappeared. The results show that during hypocapnic hypoxemia the rise in brain GABA is hypoxemia dependent, the decrease in glutamic and aspartic acid is hypocapnia dependent and the increase in lactic acid is in a large way alkalosis dependent.