Gas phase polymerization of ethylene with a silica-supported metallocene catalyst: influence of temperature on deactivation

Ethylene was polymerized at 5 bar in a stirred powder bed reactor with silica supported rac-Me2Si[Ind]2ZrCl2/methylaluminoxane (MAO) at temperatures between 40°C and 80°C using NaCl as support bed and triethylaluminium (TEA) as a scavenger for impurities. For this fixed recipe and a given charge of catalyst. the average catalyst activity is reproducible within 10% for low temperatures. The polymerization rate and the rate of deactivation increase with increasing temperature. The deactivation could be modeled using a first order dependence with respect to the polymerization rate

Pseudogap in high-temperature superconductors from realistic Fr\"ohlich and Coulomb interactions

It has been recently shown that the competition between unscreened Coulomb and Fr\"{o}hlich electron-phonon interactions can be described in terms of a short-range spin exchange $J_p$ and an effective on-site interaction $\tilde{U}$ in the framework of the polaronic $t$-$J_p$-$\tilde{U}$ model. This model, that provides an explanation for high temperature superconductivity in terms of Bose-Einstein condensation (BEC) of small and light bipolarons, is now studied as a charged Bose-Fermi mixture. Within this approximation, we show that a gap between bipolaron and unpaired polaron bands results in a strong suppression of low-temperature spin susceptibility, specific heat and tunneling conductance, signaling the presence of normal state pseudogap without any assumptions on preexisting orders or broken symmetries in the normal state of the model.Comment: 5 pages, 5 figure

Total photoionization cross sections of atomic oxygen from threshold to 44.3A

The relative cross section of atomic oxygen for the production of singly charged ions has been remeasured in more detail and extended to cover the wavelength range 44.3 to 910.5 A by the use of synchrotron radiation. In addition, the contribution of multiple ionization to the cross sections has been measured allowing total photoionization cross sections to be obtained below 250 A. The results have been made absolute by normalization to previously measured data. The use of synchrotron radiation has enabled measurements of the continuum cross section to be made between the numerous autoionizing resonances that occur near the ionization thresholds. This in turn has allowed a more critical comparison of the various theoretical estimates of the cross section to be made. The series of autoionizing resonances leading to the 4-P state of the oxygen ion have been observed for the first time in an ionization type experiment and their positions compared with both theory and previous photographic recordings

Incidence of anthelmintic resistance in cattle farms in Northern Germany – first results

Anthelmintic resistance (AR) is an increasing problem worldwide especially for small ruminants and it is also rising in cattle. To maintain the efficacy of anthelmintics is an important objective. The current project aims at the investigation of the current efficacy of macrocyclic lactone anthelmintics for strongylid nematodes in first season grazing (FSG) calves in Northern Germany. On 8 participating farms in Northern Germany faecal egg count reduction tests (FECRT) with ivermectin (IVM) were performed. On 3 farms the efficacy of IVM was found to be ≤90% and on only 4 farms it was > 95% at 14 days post treatment (d.p.t.). Only 2 farms showed a reduction ≥ 95% at 21 d.p.t.. This survey reveals a rising problem of AR. The problem of drug resistance places the welfare of animals at risk. In organic farming, without a preventive treatment, livestock may harbour high worm counts. Therefore it is necessary to maintain powerful anthelmintic drugs to guarantee the welfare of animals that need salvage treatment. To investigate the AR problem in cattle more surveys with different anthelmintic drug classes are urgently needed

Topographic Influences on Trends and Cycles in Nutrient Export from Forested Catchments on the Precambrian Shield

This dissertation explored topographic controls on spatial and temporal patterns in water yield and nutrient (carbon, nitrogen and phosphorus) export from forested headwater catchments in the Turkey Lakes Watershed in central Ontario, where other factors contributing to differences in water yield and nutrient export, including climate, geology, forest, and soils, are relatively constant. Topographic characteristics, including (a) hydrological flushing potential (expansion of water table into nitrate-N producing areas); (b) hydrological storage potential (area of wetlands, which can alternatively allow water and nutrients to bypass wetlands when storage capacity is filled with water or to trap them when not filled); and (c) hydrological loading potential (differences in precipitation caused by elevation), were considered in deconstructing non-stationary (linear trends) and stationary (oscillating cycles) patterns in water yield and nutrient export data. Topography explained the majority of differences in water yield and nutrient export. For spatial variation, topographic metrics representing hydrologic flushing potential predicted the majority of the spatial variation in nitrate-N export. In contrast, topographic metrics representing hydrologic storage potential explained the majority of the observed spatial variation in dissolved organic carbon, dissolved organic nitrogen and total dissolved phosphorus export. For temporal variation, catchments with low hydrologic loading potential were generally more sensitive to trends and cycles for water and nutrient export. Among these catchments, hydrological storage potential had no significant effect on water export trends, but had a significant effect on water export cycles; namely, the water export range was larger in the catchments with higher hydrological storage potential, even though the water export average was the same as catchments with lower hydrological storage potential. For nutrient export, the non-stationary signals were not consistent among the nutrients, but the amplitude of stationary signals in nutrient export in catchments with high hydrological storage potential compared to those with low hydrological storage potential was higher for organic nutrients and lower for nitrate-nitrogen. Despite many similarities in these headwater catchments, topography influenced the absolute and relative magnitude of hydrological and biogeochemical export from these catchments, which will have implications on the productivity and biodiversity of downstream aquatic systems

Kinetic energies of fragment ions produced by dissociative photoionization of NO

The kinetic energies of ions produced by dissociative photoionization of NO have been measured at the discrete resonance lines of He (584A) and Ne (736A), and with undispersed synchrotron radiation. O sup + ions were identified with energies from 0 to approximately 0.5 eV and two groups of N sup + ions one with energy of 0.36 eV and another with energies between 0.9 and 1.5 eV, apparently produced by predissociation of the C sup 3 P 1 and B'1 sigma states respectively

Investigation on the influence of nematophagous fungi as feed additive on nematode infection risk of sheep and goats on pasture

Gastrointestinal nematodes in small ruminants cause high economic losses. Thus on most farms anthelmintic treatment is required. In response to increasing problems with anthelmintic resistance, biological control, for example the use of nematophagous fungi, has received significant attention. The aim of this study was to investigate the effect of Duddingtonia flagrans orally applied to small ruminants on natural infection with gastrointestinal nematodes in a field study in Northern Germany. 20 goats and 20 sheep were fed daily for 3 months with 5x105 spores of D. flagrans per kg bodyweight. Differences in body weight, faecal egg count and larval development in faeces and on pasture in comparison with same-sized control groups were analysed. After 3 months the control goats showed significantly higher mean faecal egg count than the fungus-fed group. No significant difference was found between the two sheep groups. The maximum in larval reduction in faeces was 81.3 % in the sheep groups and 67.9 % in the goat groups (not significant). At the end of the study the body weight gain in the fungus-treated groups was 1.7 kg higher in goats and 0.7 kg higher in sheep than in the control groups (not significant). Regarding the first-year-grazing goats only, the bodyweights revealed significant differences (p<0.05). No statistically significant differences were observed in pasture larval counts. In the study presented here, no clear effect of fungus could be observed. A modified feeding regimen, perhaps with permanent release boluses or feed blocks, may improve the efficacy. Furthermore, it seems that climatic conditions during the study period could have influenced the results and displayed how sensitive the fungus application may be on such parameters

Remotely controlled mirror of variable geometry for small angle x-ray diffraction with synchrotron radiation

A total-reflecting mirror of 120-cm length was designed and built to focus synchrotron radiation emanating from the electron-positron storage ring at the Stanford Linear Accelerator Center (SPEAR). The reflecting surface is of unpolished float glass. The bending and tilt mechanism allows very fine control of the curvature and selectability of the critical angle for wavelengths ranging from 0.5 to 3.0 Å. Elliptical curvature is used to minimize aberrations. The mirror is placed asymmetrically onto the ellipse so as to achieve a tenfold demagnification of the source. The bending mechanism reduces nonelastic deformation (flow) and minimizes strains and stresses in the glass despite its length. Special design features assure stability of the focused image. The mirror reduces the intensity of shorter wavelength harmonics by a factor of approximately 100

Emergency purchasing situations: implications for consumer decision-making

This article introduces the Emergency Purchasing Situation (EPS) as a distinct buying context. EPSs stem from an unexpected event (unanticipated need or timing of a need), as well as high product importance, which are associated with a short time frame for consumer decision-making. Our conceptual review integrates largely disconnected strands of research and theories relevant to EPSs and offers a series of independent propositions to understand how these situations might affect consumer decision-making, specifically heuristic versus reflective information processing in product evaluation. We discuss changes induced by the buying context in terms of regulatory focus, perceived time pressure, and stress. Our propositions further account for purchase involvement in the form of product importance, purchase risk, and product substitutability. Finally, we consider how individual differences (expertise and trust) may affect evaluation processes. Our discussion reflects on the implications of our model, avenues for future research, and how an understanding of EPSs can be used to improve managerial practice

Comparative study on current trading system and online trading: the case of Ethiopia commodity exchange

The Ethiopia Commodity Exchange [ECX] is an organized market place that brings buyers and sellers to trade standardized contracts using its floor based trading system. The fundamental factors to establish successful commodity exchange includes having an efficient and robust trading platform. The focus of this research is to analyze the economic significance and limitations of the current trading system and assess the prospects and challenges of online trading and factors affecting its feasibility of implementation in ECX. The study used a mix of quantitative and qualitative research method to collect and analyze data relevant for the study. Questionnaire and in-depth interview were used to gather relevant data for the study. The study collected data from 375 members and clients out of which 279 are found to be good for analysis. In-depth interview was conducted with experts. Descriptive statistics was used to analyze the data. The study found that there is significant capacity problem with major skills gap with traders. The current system has its own significance in balancing the power of negotiation of traders by disseminating reliable data, and limitations in lack of market integrity, poor price discovery mechanisms and limitations in session and ticket writing times. It also found that there is good perception towards online trading system. Moreover, the exchange expects transparency, greater market oversight, market integrity and more commodities by deploying online trading system and challenges mainly infrastructural problems, and capacity of traders. Based on the findings, the paper recommends deploying an integrated surveillance system, reasonable allocation of session time, awareness on rules, in-depth training of staff and traders and building a redundant system were recommended for both trading systems accordingly.Keywords: Ethiopia Commodity Exchange [ECX], Floor Based Trading, Online Tradin