Cloning and characterization of ERG25, the Saccharomyces cerevisiae gene encoding C-4 sterol methyl oxidase

We have cloned the Saccharomyces cerevisiae C-4 sterol methyl oxidase ERG25 gene. The sterol methyl oxidase performs the first of three enzymic steps required to remove the two C-4 methyl groups leading to cholesterol (animal), ergosterol (fungal), and stigmasterol (plant) biosynthesis. An ergosterol auxotroph, erg25, which fails to demethylate and concomitantly accumulates 4,4-dimethylzy-mosterol, was isolated after mutagenesis. A complementing clone consisting of a 1.35-kb Dra I fragment encoded a 309-amino acid polypeptide (calculated molecular mass, 36.48 kDa). The amino acid sequence shows a C-terminal endoplasmic reticulum retrieval signal KKXX and three histidine-rich clusters found in eukaryotic membrane desaturases and in a bacterial alkane hydroxylase and xylene monooxygenase. The sterol profile of an ERG25 disruptant was consistent with the erg25 allele obtained by mutagenesis.     

Test of a high resolution drift chamber prototype

The performance of a drift chamber prototype for a colliding beam vertex detector in a test beam at DESY is described. At one (two) atmosphere gas pressure a spatial resolution of 40 μm (30 μm) per wire for one cm drift length was achieved with a 100 MHz Flash-ADC system. An excellent double track resolution of better than 300 μm over the full drift length of 5 cm can be estimated.     

MODELING WORKPIECE DYNAMICS USING SETS OF DECOUPLED OSCILLATOR MODELS

During the machining of thin-walled components, the dynamic behavior of the workpiece has a significant influence on the machining process and on the quality of the machined surfaces. In this article, a hybrid simulation concept for modeling regenerative workpiece vibrations is presented, which couples a geometric workpiece model with sets of decoupled harmonic oscillators to take the workpiece dynamics into account.     

Vorkommen bitterer Hydroxyfettsäuren in Hafer und Weizen

Occurrence of Bitter Hydroxy Fatty Acids in Oat and Wheat Water suspensions of oat, soft wheat, and durum wheat flours were incubated for 4.5 h at 38° C. Only the oat flour became intensely bitter. Freeze-dried samples of the incubated flours were analyzed for free hydroxy fatty acids with bitter taste. 750 μg/g L-OH (mixture of 9-hydroxy-trans, cis-10,12-octadecadienoic acid and 13-hydroxy-cis, trans-9,11-octadecadienoic acid) and 62 μg/g Tri-OH (mixture of 9,12,13-trihydroxy-trans-10-octadecenoic acid and 9,10,13-trihydroxy-trans-11-octadecenoic acid) were found in oat flour. Soft wheat flour contained the same amount of Tri-OH as oat flour but only 60 μg/g LOH were detected. Considerable less amounts of both L-OH and Tri-OH (20 μg/g and 15 μg/g respectively) were found in durum wheat flour. The bitter taste of oat flour which has been debittered by extraction of the lipids could be restored by addition of a mixture of 750 μg/g L-OH and 62 μg/g Tri-OH.     

Lewis Acid Induced Additions to Unsaturated Fatty Compounds

Unsaturated fatty compounds such as oleic acid, which are of interest as renewable raw materials, can be functionalized at the C,C-double bond by Lewis acid induced addition reactions. The products are branched and highly functionalized fatty compounds which may have interesting properties. SnCl₄-induced additions of nitriles to methyl oleate and ethyl 10-undecenoate give the corresponding esters of the N-acylamino fatty acids. Alkylaluminium halide induced ene additions of formaldehyde to unsaturated fatty compounds yield primary homoallylic alcohols. β,γ-Unsaturated ketones are obtained in ethylaluminium dichloride induced Friedel-Crafts acylations of unsaturated fatty compounds with acyl chlorides and cyclic anhydrides.     

Zur Hydrocarboxymethylierung von ungesättigten Fettsäureestern

On the Hydrocarboxymethylation of Unsaturated Fatty Acid Esters The hydrocarboxymethylation of technical oleic acid and eruca acid methyl ester was tested in the presence of the catalyst system cobalt/4-picoline. It was known for non terminal olefins that the formation of unbranched carboxylic acid derivatives is facilitated with the cobalt/picoline system. So up to 75% of the unbranched product is obtained during the hydrocarboxymethylation of μ-olefins. It was shown in the case of the unsaturated fatty acid methyl esters that here, too, by precise control of the reaction temperature, promoter/catalyst ratio and CO pressure the hydrocarboxymethylation can be carried out in such a way that up to 60% of the α, ω-dicarboxylic acid dimethyl esters are obtained.     

Preliminary investigation of the tribological characteristics of composite coatings sliding against ultrahigh molecular weight polyethylene

The performance of several composite coatings sliding against ultrahigh molecular weight polyethylene was evaluated in 3 h screening tests. The most promising coatings were then selected to run in 48 h wear tests, both dry and in the presence of distilled water. Composite coatings containing particles of Al₂O₃ and Cu and of 18-8 stainless steel and Al₂O₃ in epoxy matrices exhibited thermal, frictional and surface wear characteristics similar to those seen when 316 stainless steel was run against ultrahigh molecular weight polyethylene.     

CoMP clustering and backhaul limitations in cooperative cellular mobile access networks

Coordinated Multi-Point (CoMP) transmission and reception is a promising solution for managing interference and increasing performance in future wireless cellular systems. Due to its strict requirements in terms of capacity, latency, and synchronization among cooperating Base Stations (BSs), its successful deployment depends on the capability of the mobile backhaul network infrastructure.We deal with the feasibility of CoMP transmission/reception, in particular of Joint Transmission (JT). For this, we first evaluate which cluster sizes are reasonable from the wireless point-of-view to achieve the desired performance gains. Thereafter, we analyze how different backhaul topologies (e.g., mesh and tree structures) and backhaul network technologies (e.g., layer-2 switching and single-copy multicast capabilities) can support these desired clusters. We study for different traffic scenarios and backhaul connectivity levels, which part of the desired BS clusters are actually feasible according to the backhaul characteristics. We found out that a significant mismatch exists between the desired and feasible clusters. Neglecting this mismatch causes overheads in real JT implementations, which complicates or even prevents their deployment.Based on our findings, we propose a clustering system architecture that not only includes wireless information, as done in the state of the art, but also combines wireless and backhaul network feasibility information in a smart way. This avoids unnecessary signaling and User Equipment (UE) data exchange among BSs which are not eligible to take part in the cooperative cluster. Evaluations show that our scheme reduces the signaling and UE data exchange overhead by up to 85% compared to conventional clustering approaches, which do not take into account the backhaul network’s status.