University of Amsterdam

About: University of Amsterdam is a education organization based out in Amsterdam, Noord-Holland, Netherlands. It is known for research contribution in the topics: Population & Context (language use). The organization has 59309 authors who have published 140894 publications receiving 5984137 citations. The organization is also known as: UvA & Universiteit van Amsterdam.

National differences in gender–science stereotypes predict national sex differences in science and math achievement

Abstract: About 70% of more than half a million Implicit Association Tests completed by citizens of 34 countries revealed expected implicit stereotypes associating science with males more than with females. We discovered that nation-level implicit stereotypes predicted nation-level sex differences in 8th-grade science and mathematics achievement. Self-reported stereotypes did not provide additional predictive validity of the achievement gap. We suggest that implicit stereotypes and sex differences in science participation and performance are mutually reinforcing, contributing to the persistent gender gap in science engagement.

Ligand Bite Angle Effects in Metal-catalyzed C−C Bond Formation

Abstract: phinoethane) seemed mainly to stabilize intermediates, and often the catalytic reactions were slower when dppe was used instead of the most common monodentate triphenylphosphine. We will briefly review the history of “ligand effects” in catalysis before discussing a range of reactions for which a notable effect has been observed. It has taken quite some time before the positive effect that bidentates can have on selectivities and rates of catalytic reactions was fully recognized. Most of the established examples of bite angle effects involve diphosphine ligands. Therefore, many important catalysts containing a chelate ligand such as bipyridine and diimine will fall outside the scope of this review. The connecting bridge in these bidentates does play a dominant role in the performance of these catalysts, but systematic studies have not been published. The effects of phosphine ligands in catalysis have been known for quite some time. One of the first reports involves the use of triphenylphosphine in the “Reppe” chemistry, the reactions of alkynes, alcohols, and carbon monoxide.1 It was found that formation of acrylic esters was much more efficient using NiBr2(PPh3)2 than NiBr2 without ligand. In the commercial system, though, a phosphine-free catalyst is used. While the reaction was not yet understood mechanistically, the use of phosphines in catalysis attracted the attention of the petrochemical industry worldwide. An early example of a phosphine ligand modified catalytic process is the Shell process for alkene hydroformylation using a cobalt catalyst containing a trialkylphoshine.2 The reaction requires higher temperatures, but it leads to more linear product as compared to the unmodified catalyst. The general mechanism of the hydroformylation reaction has been known for a long time.3 Hydrocyanation as used by Du Pont is another early example of an industrially applied catalytic reaction employing ligands.4 It is a nickel-catalyzed reaction in which aryl phosphite ligands are used for the production of adiponitrile. The development of this process has played a key role in the introduction of the now very common study of “ligand effects” in the field of homogeneous catalysis by organometallic complexes.5 While several industries were working on new homogeneous catalysts, important contributions to the new field were made in academia in the early 1960s with the appearance of the first phosphinemodified hydrogenation catalysts. An early example of a phosphine-free ruthenium catalyst was published by Halpern.6 Triphenylphosphine-modified platinumtin catalysts for the hydrogenation of alkenes were reported by Cramer from Du Pont in 1963.7 In the same year Breslow (Hercules) included a few phosFigure 1. Bite angle: The ligand-metal-ligand angle of bidentate ligands. 2741 Chem. Rev. 2000, 100, 2741−2769

Molecular subgroups of medulloblastoma: an international meta-analysis of transcriptome, genetic aberrations, and clinical data of WNT, SHH, Group 3, and Group 4 medulloblastomas

Abstract: Medulloblastoma is the most common malignant brain tumor in childhood. Molecular studies from several groups around the world demonstrated that medulloblastoma is not one disease but comprises a collection of distinct molecular subgroups. However, all these studies reported on different numbers of subgroups. The current consensus is that there are only four core subgroups, which should be termed WNT, SHH, Group 3 and Group 4. Based on this, we performed a meta-analysis of all molecular and clinical data of 550 medulloblastomas brought together from seven independent studies. All cases were analyzed by gene expression profiling and for most cases SNP or array-CGH data were available. Data are presented for all medulloblastomas together and for each subgroup separately. For validation purposes, we compared the results of this meta-analysis with another large medulloblastoma cohort (n = 402) for which subgroup information was obtained by immunohistochemistry. Results from both cohorts are highly similar and show how distinct the molecular subtypes are with respect to their transcriptome, DNA copy-number aberrations, demographics, and survival. Results from these analyses will form the basis for prospective multi-center studies and will have an impact on how the different subgroups of medulloblastoma will be treated in the future.

Rotating massive main-sequence stars - I. Grids of evolutionary models and isochrones

Abstract: We present a dense grid of evolutionary tracks and isochrones of rotating massive main-sequence stars. We provide three grids with different initial compositions tailored to compare with early OB stars in the Small and Large Magellanic Clouds and in the Galaxy. Each grid covers masses ranging from 5 to 60 M ⊙ and initial rotation rates between 0 and about 600 km s-1 . To calibrate our models we used the results of the VLT-FLAMES Survey of Massive Stars. We determine the amount of convective overshooting by using the observed drop in rotation rates for stars with surface gravities log g < 3.2 to determine the width of the main sequence. We calibrate the efficiency of rotationally induced mixing using the nitrogen abundance determinations for B stars in the Large Magellanic cloud. We describe and provide evolutionary tracks and the evolution of the central and surface abundances. In particular, we discuss the occurrence of quasi-chemically homogeneous evolution, i.e. the severe effects of efficient mixing of the stellar interior found for the most massive fast rotators. We provide a detailed set of isochrones for rotating stars. Rotation as an initial parameter leads to a degeneracy between the age and the mass of massive main sequence stars if determined from its observed location in the Hertzsprung-Russell diagram. We show that the consideration of surface abundances can resolve this degeneracy.

Anaphylaxis: guidelines from the European Academy of Allergy and Clinical Immunology

Abstract: Anaphylaxis is a clinical emergency, and all healthcare professionals should be familiar with its recognition and acute and ongoing management. These guidelines have been prepared by the European Academy of Allergy and Clinical Immunology (EAACI) Taskforce on Anaphylaxis. They aim to provide evidence-based recommendations for the recognition, risk factor assessment, and the management of patients who are at risk of, are experiencing, or have experienced anaphylaxis. While the primary audience is allergists, these guidelines are also relevant to all other healthcare professionals. The development of these guidelines has been underpinned by two systematic reviews of the literature, both on the epidemiology and on clinical management of anaphylaxis. Anaphylaxis is a potentially life-threatening condition whose clinical diagnosis is based on recognition of a constellation of presenting features. First-line treatment for anaphylaxis is intramuscular adrenaline. Useful second-line interventions may include removing the trigger where possible, calling for help, correct positioning of the patient, high-flow oxygen, intravenous fluids, inhaled short-acting bronchodilators, and nebulized adrenaline. Discharge arrangements should involve an assessment of the risk of further reactions, a management plan with an anaphylaxis emergency action plan, and, where appropriate, prescribing an adrenaline auto-injector. If an adrenaline auto-injector is prescribed, education on when and how to use the device should be provided. Specialist follow-up is essential to investigate possible triggers, to perform a comprehensive risk assessment, and to prevent future episodes by developing personalized risk reduction strategies including, where possible, commencing allergen immunotherapy. Training for the patient and all caregivers is essential. There are still many gaps in the evidence base for anaphylaxis.