Modeling of microwave-induced plasma in argon at atmospheric pressure.

A two-dimensional model of microwave-induced plasma (field frequency 2.45 GHz) in argon at atmospheric pressure is presented. The model describes in a self-consistent manner the gas flow and heat transfer, the in-coupling of the microwave energy into the plasma, and the reaction kinetics relevant to high-pressure argon plasma including the contribution of molecular ion species. The model provides the gas and electron temperature distributions, the electron, ion, and excited state number densities, and the power deposited into the plasma for given gas flow rate and temperature at the inlet, and input power of the incoming TEM microwave. For flow rate and absorbed microwave power typical for analytical applications (200-400 ml/min and 20 W), the plasma is far from thermodynamic equilibrium. The gas temperature reaches values above 2000 K in the plasma region, while the electron temperature is about 1 eV. The electron density reaches a maximum value of about 4 × 10(21) m(-3). The balance of the charged particles is essentially controlled by the kinetics of the molecular ions. For temperatures above 1200 K, quasineutrality of the plasma is provided by the atomic ions, and below 1200 K the molecular ion density exceeds the atomic ion density and a contraction of the discharge is observed. Comparison with experimental data is presented which demonstrates good quantitative and qualitative agreement.

Differential effects of ceramides upon adenylyl cyclase subtypes.

Ceramides are reported to stimulate different effector systems, among them atypical protein kinases C (PKCs). When HEK 293 cells, stably expressing adenylyl cyclase type II (AC II), were treated with various ceramide derivatives, adenylyl cyclase activity was enhanced 8-15-fold. The stimulation by the most potent analog, C18/C24 ceramide, was comparable to that by the phorbolester TPA. The stimulatory effect of ceramide was not restricted to AC II, although the type I and type V enzymes were affected less dramatically. Unexpectedly, the dihydro derivatives of ceramides, generally serving as non-activating controls, exhibited only slightly lower stimulation than ceramides, whereas short-chain ceramides (e.g. C2) were without effect. The action of ceramides was at least partially inhibited by okadaic acid, suggesting involvement of a phosphatase. Furthermore, ceramides and TPA operated synergistically. While the PKC inhibitor staurosporine counteracted the action of phorbol-esters, it significantly (2.5x) enhanced the effect of ceramides.

Phorbol ester-induced sensitisation of adenylyl cyclase type II is related to phosphorylation of threonine 1057.

Following up the results from previous studies on chemical fragmentation of TPA-treated, [32P]phosphate labeled adenylyl cyclase type II (AC II) (Böl, G. F., Hülster, A., and Pfeuffer, T. in press) we have replaced serine 871 or threonine 1057 by alanine using site directed mutagenesis. Both mutants had unimpaired catalytic activity, however enhancement by phorbolester TPA was reduced by 60-80 % in the T1057A mutant, but not in the S871A mutant. The stimulation of adenylyl cyclase type II by betagamma subunits of heterotrimeric G-pro teins and that by PKC have been previously shown to be mutually exclusive (Zimmermann and Taussig (1996), J. Biol. Chem. 271, 27161-27166). This is in line with the present findings that AC II expressed in COS-1 cells was only barely stimulated (10%) by coexpressed betagamma-subunits in presence of TPA. Mutation of threonine 1057 to alanine however caused partial regain of betagamma-stimulation in the presence of TPA by 40%, as compared to that of WT adenylyl cyclase type II which was 70% in the absence of TPA. These data strongly implicate the importance of threonine 1057 as phosphate acceptor following PKC-mediated sensitisation of adenylyl cyclase type II.

[Experience with dynamic hip screw in retrochanteric and subtrochanteric fractures of upper femur.]. / Erfahrungen mit der dynamischen Hüftschraube bei per- und subtrochantären Oberschenkelfrakturen.

From 1st January 1988 to 31st December 1994, 105 patients were given 106 dynamic hip-screws in the Orthopaedic Department of the Public General Hospital, Zwettl. The average age at the time of operation was 77.6 years and the time lapse between the accident occuring and the operation performed was on average 31 hours. In 94.3% of the cases we could perform a closed reduction and in 88.7% we used a 135 degree-DHS. The four-hole plate dominated in 73.6% of the plates used. Internal complications totalled 23.6% out of which 9.5% of the patients died during their hospitalization. Here one must take note that the patients who died were of advanced age and multimorbid. We carried out clinical and radiological postoperative examinations on 54 patients (51.4%) with 55 operations (51.9%). The postoperative examinations took place on an average of 33 months (2 years and 9 months). The clinical postoperative examinations were carried out according to the Merle D'Aubigne system - 29 excellent, 58 good and 13 poor. The radiological postoperative examinations disclosed an ossian consolidation of 100% for 54 patients with 55 operations. Taking into account the classification of fractures according to the AO we find that the DHS is mainly used to treat fractures A 1/1-, A 1/2- and A 2/2-. With the exception of subtrochanteric fractures in which we have lately been using the Gamma-Nail, we have the DHS as a technically relatively simple and inexpensive implant in the treatment of pertrochanteric fractures of the neck of the femur.

[Basket wires--a percutaneous surgical procedure for the treatment of unstable Colles' fractures]. / Körbchendrähte--Ein perkutanes Operationsverfahren zur Behandlung der instabilen Colles-Fraktur.

Colles fractures are usually treated with closed reduction and forearm plaster. Even if reduced perfectly, some of these fractures tend to redislocate dorsally and radially, requiring repeated reduction maneuvers. Since K-wires cannot be firmly anchored in the distal fragment if comminution exists, Kapandji proposed a method whereby the distal fragment is not pinned at all. He introduced the pins through the fracture itself and into the medullary canal of the proximal fragment, anchoring the wires into the opposite cortices of the radius shaft. In order to "pre-stress" the K-wires, Böhler and Zifko modified the technique and the wires themselves. They inserted the wires through small skin incisions into the fracture and into the proximal fragment as medullary pins. The specially bent pins glide smoothly into the medullary cavity and snugly fit along the distal fragment; thereby minimizing the chance of damaging extensor tendons. One pin is inserted proximal to Lister's tubercle and another radially, proximal to the radial styloid. Technique, indication, and possible technical errors are discussed based on the follow-up of forty one patients.