Sodium Dihydridobis(2-methoxyethoxo)aluminate as a suitable reducing agent in the cooligomerization of propadiene with propyne from MAAF catalyzed by a nickel based three component catalytic system

Sodium dihydridobis(2-methoxyethoxo)aluminate (SDMA) is a suitable reducing agent for in situ generation of zerovalent nickel in a catalytic system nickel(II) 2, 4-pentanedionate/phosphorus(III) ligand/reducing agent. Although generally less polymer is formed in the propadiene/propyne cooligomerization catalyzed by this system when the reducing agent is triethylaluminium, at molar ratios Al/Ni = 3 and P/Ni = 3 no polymer is formed with SDMA and the yield of oligomers is comparable to that obtained with triethylaluminium.     

Geochemistry and mineralogy of platinum-group elements (PGE) in chromites from Centralnoye I, Polar Urals, Russia

The Polar Urals region of northern Russia is well known for large chromium(Cr)-bearing massifs with major chromite orebodies,including the Centralnoye I deposit in the Ray-lz ultramafic massif of the Ural ophiolite belt.New data on platinum(Pt)-group elements(PGE),geochemistry and mineralogy of the host dunite shows that the deposit has anomalous iridium(It)values.These values indicate the predom-inance of ruthenium-osmium-iridium(Ru-Os-lr)-bearing phases among the platinum-group mineral(PGM)assemblage that is typical of mantle-hosted chromite ores.Low Pt values in chromites and increased Pt values in host dunites might reflect the presence of cumulus PGM grains.The most abundant PGM tbund in the chromite is erlichmanite(up to 15 μm).Less common are cuproiridsite(up to 5 μm),irarsite(up to4-5 μm),and laurite(up to 4 μm).The predominant sulfide is heazlewoodite,in intergrowth with Ni--Fe alloys,sporadically with pentlandite,and rarely with pure nickel.Based on the average PGE values and esti-mated Cr-ore resources,the Centralnoye I deposit can be considered as an important resource of PGE.     

Widely tunable continuous-wave mid-infrared radiation (5.5-11 microm) by difference-frequency generation in LiInS2 crystal

The first demonstration, to the best of our knowledge, of continuous-wave (cw) difference-frequency generation (DFG) in LiInS2 crystal is reported. Wide spectral coverage (5.5-11.3 microm) has been obtained with angle and wavelength tuning for type II (eoe) critically phase-matched parametric interaction. The phase-matching conditions in cw DFG have been investigated, which allowed us to improve the Sellmeier parameters by use of a two-pole dispersion equation. An effective nonlinear coefficient deff = 6.9 +/- 0.8 pm/V has been determined at approximately 7 microm relative to the well-known nonlinear coefficient d36 of AgGaS2, which yields a power-conversion efficiency of approximately 12.4 microW/(W2 cm). We evaluated the high-resolution spectral characteristics of the DFG source by recording C2H2 and SO2 spectra.     

RESPIRATORY DEFICIENT MUTANTS OF BOTTOM BREWER'S YEAST. I. FREQUENCIES AND TYPES OF MUTANT IN VARIOUS STRAINS

Four strains of bottom brewer's yeast used in Czech breweries did not differ substantially from one another in their frequencies of spontaneous respiratory-deficient (RD) mutants as tested by the triphenyl tetrazolium chloride (TTC) overlay technique. These frequencies amounted to 1.1–1.4% of the total viable cell number after cultivation in bottom layers of wort. The strain which had the highest rate of aerobic growth gave a spontaneous mutation frequency of 0.5% in shaken cultures. In comparison with the TTC overlay technique, WL-Difco-agar with brom cresol green gave lower estimations of the frequency of production of spontaneous RD mutants. The RD mutants isolated can be divided into II groups on the basis of their cytochrome content (particularly cytochromes b and c) after aerobic growth. Of the 34 RD isolates tested, only 3 produced considerable numbers of revertants to respiratory sufficiency. These 3 mutants were derived from the same original strain, had the same cytochrome type, and had very slow growth rates. All RD mutants isolated had slower growth rates under aerobic conditions and reduced fermentation rates in static cultures in comparison with the parent types.     

METABOLIC QUOTIENTS OF RESPIRATION-DEFICIENT MUTANTS OF BREWER'S YEAST AND THE APPEARANCE OF A NEGATIVE PASTEUR EFFECT

Four industrial strains of bottom brewer's yeast and a group of their spontaneous respiration deficient (RD) mutants were tested for rates of metabolism of glucose and maltose under aerobic and anaerobic conditions. Q_o2 of all the RD mutants tested (26 isolates) ranged from 1·9 to 6·8 μl/mg yeast dry weight on glucose and was lowered to about one-half on maltose although the original strains had the same Q_o2 values on both sugars. No isolate showed any increase in glucose fermentation in aerobic conditions as compared with the original strains and the decrease of Pasteur effect found in certain isolates was always accompanied by a strong decrease of glycolysis in both aerobic and anaerobic conditions. Two mutants showed a strongly negative Pasteur effect, for their fermentation rates were higher in aerobic conditions than in anaerobic ones. Two other mutants showed a strong negative Pasteur effect only on maltose. The ratio of Q^N_2CO2 on glucose in most mutants was significantly lower than in their parental strains.     

A unified benchmarking and model-based framework for building QoS-aware streaming media services

A number of technology and workload trends motivate us to consider the appropriate resource allocation mechanisms and policies for streaming media services in shared cluster environments. We present MediaGuard – a model-based infrastructure for building streaming media services – that can efficiently determine the fraction of server resources required to support a particular client request over its expected lifetime. The proposed solution is based on a unified cost function that uses a single value to reflect overall resource requirements such as the CPU, disk, memory, and bandwidth necessary to support a particular media stream based on its bit rate and whether it is likely to be served from memory or disk. We design a novel, time-segment-based memory model of a media server to efficiently determine in linear time whether a request will incur memory or disk access when given the history of previous accesses and the behavior of the server's main memory file buffer cache. Using the MediaGuard framework, we design two media services: (1) an efficient and accurate admission control service for streaming media servers that accounts for the impact of the server's main memory file buffer cache, and (2) a shared streaming media hosting service that can efficiently allocate the predefined shares of server resources to the hosted media services, while providing performance isolation and QoS guarantees among the hosted services. Our evaluation shows that, relative to a pessimistic admission control policy that assumes that all content must be served from disk, MediaGuard (as well as services that are built using it) deliver a factor of two improvement in server throughput.     

Improvement of Mechanical Properties of Automotive Components Using Hot Stamping With Integrated Q-P Process

Cold forming of high strength materials is accompanied by an undesirable spring-back effect and therefore the automotive industry prefers to produce components from high strength steels by hot stamping.Hot deformation and cooling in a die are applied to obtain shaped components with martensitic microstructure and high yield strength and ultimate tensile strength.This article presents new applications of this forming technology by incorporating another innovative heat treatment by the Q-P process,which improves both strength and ductility of obtained structures at the same time.Ultimate strengths over 2000 MPa with ductility above 10% can be achieved by this processing.To test microstructure development,thin sheet was hot formed and a corresponding FEM simulation was created.This processing was applied to low alloyed AHS steel with 0.42% of carbon and with an alloying strategy based on Mn,Si and Cr.Martensitic microstructure with retained austenite was obtained by this processing with a strength of around 2000 MPa and ductility of 10%.