Time filter

Source Type

Chicago, IL, United States

</blockquote>A Ziegler–Natta catalyst, named after Karl Ziegler and Giulio Natta, is a catalyst used in the synthesis of polymers of 1-alkenes . Two broad classes of Ziegler–Natta catalysts are employed, distinguished by their solubility: Heterogeneous supported catalysts based on titanium compounds are used in polymerization reactions in combination with cocatalysts, organoaluminum compounds such as triethylaluminium, Al3. This class of catalyst dominates the industry. Homogeneous catalysts usually based on complexes of Ti, Zr or Hf. They are usually used in combination with a different organoaluminum cocatalyst, methylaluminoxane . These catalysts traditionally include metallocenes but also feature multidentate oxygen- and nitrogen-based ligands.Ziegler–Natta catalysts are used to polymerize terminal 1-alkenes :n CH2=CHR → −n−↑ Wikipedia.

Stings by insects of the order Hymenoptera cause systemic, sometimes life threatening allergic reactions in 1 -5% of the population in Europe and North America. Responsible for these reactions is an IgE mediated sensitization to proteins of the venoms injected during the stings of social Hymenoptera species, mainly the honey bee (Apis mellifera), vespids like Vespula sp, Polistes sp. and ants, in southern US and central America Solenopsis invicta and in Australia Myrmecia pilosula. The venoms of these insects are composed of low molecular weight substances like biogenic amines, cytotoxic and neurotoxic peptides like melittin, apamin, MCD-peptide and mastoparan, and proteins, mostly enzymes like phospholipase A and hyaluronidase, which are major venom allergens. 000Immunotherapy with Hymenoptera venoms has been shown to protect 80 to over 95% of patients with a history of systemic allergic sting reaction from further systemic reactions after re-stings. The procedure, safety and efficacy of this treatment and the immune mechanisms involved are discussed. Since ancient times honey bee venom has been used for the treatment of chronic inflammatory disease, especially arthritis. Anti-inflammatory effects of bee venom have been documented in animal experiments. Most clinical studies suggest an antiinflammatory effect as well, but are uncontrolled. The only few controlled studies could not confirm efficacy of treatment with bee venom so far. © 2011 Bentham Science Publishers. Source

For nearly a century, biologists have emphasized the profound importance of spatial scale for ecology, evolution and conservation. Nonetheless, objectively identifying critical scales has proven incredibly challenging. Here we extend new techniques from physics and social sciences that estimate modularity on networks to identify critical scales for movement and gene flow in animals. Using four species that vary widely in dispersal ability and include both mark-recapture and population genetic data, we identify significant modularity in three species, two of which cannot be explained by geographic distance alone. Importantly, the inclusion of modularity in connectivity and population viability assessments alters conclusions regarding patch importance to connectivity and suggests higher metapopulation viability than when ignoring this hidden spatial scale. We argue that network modularity reveals critical meso-scales that are probably common in populations, providing a powerful means of identifying fundamental scales for biology and for conservation strategies aimed at recovering imperilled species. Source

Muller U.R.,Ziegler
Chemical Immunology and Allergy

Insect venoms applied by stings of social Hymenoptera, like honey bees, vespids or ants are -together with foods and drugs - the most frequent elicitors of anaphylaxis in humans. Besides taxonomy, the biology of the responsible social Hymenoptera is important: guidelines based upon its knowledge allow to reduce the risk of further stings in patients with a history of venom anaphylaxis. Epidemiology of venom anaphylaxis has special aspects with regard to prevalence, fatality and natural history. An estimated 200 individuals die every year in Europe from anaphylaxis following Hymenoptera stings. Most of the relevant venom protein allergens have been identified and many of them have been expressed in recombinant form. Proof of venom sensitization is based on skin tests with venoms and serum venom-specific IgE antibodies as standard diagnostic tests. Allergen-specific immunotherapy with Hymenoptera venoms is highly effective and therefore recommended for all patients with a history of Hymenoptera sting anaphylaxis and positive diagnostic tests with the respective venom. Frequent cross-reactions to venoms of different Hymenoptera species may cause difficulties in identifying the responsible species and the selection of the respective venom for immunotherapy. Copyright © 2010 S. Karger AG, Basel. Source

Schroeder V.,University of Bern | Kohler H.P.,University of Bern | Kohler H.P.,Ziegler
Journal of Thrombosis and Haemostasis

To cite this article: Schroeder V, Kohler HP. New developments in the area of factor XIII. J Thromb Haemost 2013; 11: 234-44. Summary. Coagulation factor (F)XIII is best known for its role in fibrin stabilization and cross-linking of antifibrinolytic proteins to the fibrin clot. From patients with congenital FXIII deficiency, it is known that FXIII also has important functions in wound healing and maintaining pregnancy. Over the last decade more and more research groups with different backgrounds have studied FXIII and have unveiled putative novel functions for FXIII. FXIII, with its unique role as a transglutaminase among the other serine protease coagulation factors, is now recognized as a multifunctional protein involved in regulatory mechanisms and construction and repair processes beyond hemostasis with possible implications in many areas of medicine. The aim of this review was to give an overview of exciting novel findings and to highlight the remarkable diversity of functions attributed to FXIII. Of course, more research into the underlying mechanisms and (patho-)physiological relevance of the many described functions of FXIII is needed. It will be exciting to observe future developments in this area and to see if and how these interesting findings may be translated into clinical practice in the future. © 2012 International Society on Thrombosis and Haemostasis. Source

Predation risk is widely hypothesized as an important force structuring communities, but this potential force is rarely tested experimentally, particularly in terrestrial vertebrate communities. How animals respond to predation risk is generally considered predictable from species life-history and natural-history traits, but rigorous tests of these predictions remain scarce. We report on a large-scale playback experiment with a forest bird community that addresses two questions: (i) does perceived predation risk shape the richness and composition of a breeding bird community? And (ii) can species life-history and natural-history traits predict prey community responses to different types of predation risk? On 9 ha plots, we manipulated cues of three avian predators that preferentially prey on either adult birds or offspring, or both, throughout the breeding season. We found that increased perception of predation risk led to generally negative responses in the abundance, occurrence and/or detection probability of most prey species, which in turn reduced the species richness and shifted the composition of the breeding bird community. Species-level responses were largely predicted from the key natural-history trait of body size, but we did not find support for the life-history theory prediction of the relationship between species' slow/fast life-history strategy and their response to predation risk. Source

Discover hidden collaborations