The use of niobia in oxidation catalysis

This paper summarises the background to work carried out at the University of Twente on the use of niobia as a catalyst for the oxidative dehydrogenation of propane to propylene and discusses the development of promoted niobia catalysts for this reaction. Results are also presented which illustrate the use of niobia in catalysts for other reactions such as the oxidative coupling of methane, the oxidative dehydrogenation of ethane and the oxidative dehydrogenation of methanol. It appears that niobia and niobia-modified catalysts, when used in high-temperature oxidation processes, can exhibit relatively high selectivities compared with more conventional catalysts

How to Collect and Preserve Insects

Ope

Suppression of natural killer cell activity in harbour seals (Phoca vitulina) fed Baltic Sea herring

Mass mortalities among marine mammal populations in recent years have raised questions about a possible contributory role of contaminants accumulated through the marine food chain. While viruses were shown to be the primary cause of the outbreaks, an immunotoxic action by organochlorine chemicals in affected animals could not be ruled out. We carried out a 2 1/2 -year immunotoxicological experiment in which two groups of 11 harbour seals each were fed herring from either the relatively contaminated Baltic Sea or the relatively uncontaminated Atlantic Ocean. Seals in the Baltic Sea group accumulated 3-4 times higher levels of Ah-receptor-mediated 2,3,7,8-TCDD Toxic Equivalents in blubber than did their Atlantic counterparts following 2 years on the respective diets. Blood was sampled a total of 17 times during the course of the experiment for immunological evaluation, during which time the natural cytotoxic activity of peripheral blood mononuclear cells isolated from seals fed Baltic Sea herring declined to a level approximately 2

Impairment of Immune Function in Harbor Seals (Phoca vitulina) Feeding on Fish from Polluted Waters

Disease outbreaks with high mortality rates among seals and dolphins have recently attracted considerable public and scientific interest. Allhouyh in most cases morbillivirus infections were shown to be the primary cause of the disease outbreaks, it was speculated that pollution-induced immunosuppression had playat:! a contributory role. Here we present results of a prospective study under semifield conditions, in which two groups of harbor seals (Phoca vitulina) were fed herring from marine regions with different contamination levels; the hig

Short term fasting does not aggravate immunosuppression in harbour seals (Phoca vitulina) with high body burdens of organochlorines

Two groups of 11 harbour seals (Phoca vitulina) with different body burdens of organochlorines were subjected to an experimental 15-day fasting period, during which they lost an average 16.5% of their body weights. Blood levels of the most persistent organochlorines showed an approximate twofold increase, while levels of aryl hydrocarbon receptor-binding organochlorines remained largely unaffected. Few differences in immunological parameters were observed between the two dietary groups. Numbers of circulating lymphocytes dropped to about 65% of the initial values and NK cell activity showed a slight increase in both groups. Mitogen- and antigen-induced lymphoproliferative responses of the Baltic group of seals remained within normal ranges. These results suggest that relatively short-term fasting periods do not present an additional immunotoxicological risk to seals with high body burdens of organochlorines

Host resistance to rat cytomegalovirus (RCMV) and immune function in adult PVG rats fed herring from the contaminated Baltic Sea

The immunotoxic potential of many classes of environmental contaminants has been well established in laboratory studies, with much attention being focussed on aryl hydrocarbon (Ah)-receptor binding polychlorinated biphenyl (PCB), polychlorinated dibenzo-p-dioxin (PCDD), and polychlorinated dibenzofuran (PCDF) congeners. In a semi-field study, we previously showed that harbour seals (Phoca vitulina) fed herring from the contaminated Baltic Sea had lower natural killer cell activity, T-lymphocyte functionality and delayed-type hypersensitivity responses than seals fed herring from the relatively uncontaminated Atlantic Ocean. While ethical and practical constraints preclude in-depth studies in seals, specific reagents and a wider array of immune function tests allow such studies in laboratory rats. We therefore carried out a feeding study in rats aimed at extending our observations of contaminant-induced immunosuppression in harbour seals. The same two herring batches used in the seal study were freeze-dried, supplemented and fed. to female adult PVG rats for a period of 4 1/4 months. Daily contaminant intakes of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxic equivalents (TEQ) were estimated to be 0.3 ng/kg body weight and 1.6 ng/kg in the Atlantic and Baltic groups, respectively. At the end of the feeding experiment, no contaminant-related changes in spleen CD4+/CD8+cellularity, natural killer cell activity, or mitogen-induced proliferative responses of thymus or spleen cells could be detected. However, total thymocyte numbers and thymus CD4+/CD8+ratios were reduced in the Baltic group. A novel model was established to assess the specific T-cell response to rat cytomegalovirus (RCMV). When applied to the feeding study, no differences between the Atlantic and Baltic groups in the RCMV-induced proliferative T-lymphocyte responses could be detected, but virus titres in salivary glands of infected rats of the Baltic Sea group were higher. These elevated RCMV titres and changes in thymus cellularity suggest that the dietary exposure to low levels of contaminants may have been immunotoxic at a level which our immune function test could not otherwise detect. While the herring diet per se appeared to have an effect on several immune function parameters, lower plasma thyroid hormone levels in the Baltic Sea group of rats confirmed that exposure to the environmental mixture of contaminants led to adverse PHAH-related health effects

Scalar Levin-Type Sequence Transformations

Sequence transformations are important tools for the convergence acceleration of slowly convergent scalar sequences or series and for the summation of divergent series. Transformations that depend not only on the sequence elements or partial sums $s_n$ but also on an auxiliary sequence of so-called remainder estimates $\omega_n$ are of Levin-type if they are linear in the $s_n$, and nonlinear in the $\omega_n$. Known Levin-type sequence transformations are reviewed and put into a common theoretical framework. It is discussed how such transformations may be constructed by either a model sequence approach or by iteration of simple transformations. As illustration, two new sequence transformations are derived. Common properties and results on convergence acceleration and stability are given. For important special cases, extensions of the general results are presented. Also, guidelines for the application of Levin-type sequence transformations are discussed, and a few numerical examples are given.Comment: 59 pages, LaTeX, invited review for J. Comput. Applied Math., abstract shortene

The ASSURE study: HIV-1 suppression is maintained with bone and renal biomarker improvement 48 weeks after ritonavir discontinuation and randomized switch to abacavir/lamivudine+atazanavir

Objectives: HIV treatment guidelines endorse switching or simplification of antiretroviral therapy in therapy-experienced patients with suppressed viraemia; ritonavir discontinuation may also enhance tolerability and reduce long-term adverse events (AEs). This open-label, multicentre, noninferiority study enrolled HIV-1-infected, treatment-experienced adults with confirmed HIV-1 RNA≤75 HIV-1 RNA copies/mL currently receiving tenofovir/emtricitabine+atazanavir/ritonavir (TDF/FTC+ATV/r) for ≥6 months with no reported history of virological failure. Methods: Participants were randomized 1:2 to continue current treatment or switch to abacavir/lamivudine + atazanavir (ABC/3TC+ATV). Endpoints included the proportion of participants with HIV-1 RNA<50 copies/mL by time to loss of virological response (TLOVR), AEs, fasting lipids, and inflammatory, coagulation, bone and renal biomarkers. Results: After 48 weeks, 76% (152 of 199) of ABC/3TC+ATV-treated and 79% (77 of 97) of TDF/FTC+ATV/r-treated participants had HIV-1 RNA<50 copies/mL (TLOVR; P=0.564). Other efficacy analyses yielded similar results. Rates of new grade 2-4 AEs were 45% in both groups, but an excess of hyperbilirubinaemia made the rate of treatment-emergent grade 3-4 laboratory abnormalities higher with TDF/FTC+ATV/r (36%) compared with ABC/3TC+ATV (19%). Most fasting lipid levels remained stable over time; high-density lipoprotein (HDL) cholesterol increased modestly in ABC/3TC+ATV-treated participants. Bone and renal biomarkers improved significantly between baseline and week 48 in participants taking ABC/3TC+ATV and were stable in participants taking TDF/FTC+ATV/r. No significant changes occurred in any inflammatory or coagulation biomarker within or between treatment groups. Conclusions: The ABC/3TC+ATV treatment-switch group had similar viral suppression rates up to 48 weeks to the TDF/FTC+ATV/r comparator group, with lower rates of moderate- to high-grade hyperbilirubinaemia and improvements in bone and renal biomarkers