Towards ensemble asteroseismology of the young open clusters Chi Persei and NGC 6910

As a result of the variability survey in Chi Persei and NGC6910, the number of Beta Cep stars that are members of these two open clusters is increased to twenty stars, nine in NGC6910 and eleven in Chi Persei. We compare pulsational properties, in particular the frequency spectra, of Beta Cep stars in both clusters and explain the differences in terms of the global parameters of the clusters. We also indicate that the more complicated pattern of the variability among B type stars in Chi Persei is very likely caused by higher rotational velocities of stars in this cluster. We conclude that the sample of pulsating stars in the two open clusters constitutes a very good starting point for the ensemble asteroseismology of Beta Cep-type stars and maybe also for other B-type pulsators.Comment: 4 pages, Astronomische Nachrichten, HELAS IV Conference, Arecife, Lanzarote, Feb 2010, submitte

HF-EPR, Raman, UV/VIS Light Spectroscopic, and DFT Studies of the Ribonucleotide Reductase R2 Tyrosyl Radical from Epstein-Barr Virus

Epstein-Barr virus (EBV) belongs to the gamma subfamily of herpes viruses, among the most common pathogenic viruses in humans worldwide. The viral ribonucleotide reductase small subunit (RNR R2) is involved in the biosynthesis of nucleotides, the DNA precursors necessary for viral replication, and is an important drug target for EBV. RNR R2 generates a stable tyrosyl radical required for enzymatic turnover. Here, the electronic and magnetic properties of the tyrosyl radical in EBV R2 have been determined by X-band and high-field/high-frequency electron paramagnetic resonance (EPR) spectroscopy recorded at cryogenic temperatures. The radical exhibits an unusually low g1-tensor component at 2.0080, indicative of a positive charge in the vicinity of the radical. Consistent with these EPR results a relatively high C-O stretching frequency associated with the phenoxyl radical (at 1508 cm−1) is observed with resonance Raman spectroscopy. In contrast to mouse R2, EBV R2 does not show a deuterium shift in the resonance Raman spectra. Thus, the presence of a water molecule as a hydrogen bond donor moiety could not be identified unequivocally. Theoretical simulations showed that a water molecule placed at a distance of 2.6 Å from the tyrosyl-oxygen does not result in a detectable deuterium shift in the calculated Raman spectra. UV/VIS light spectroscopic studies with metal chelators and tyrosyl radical scavengers are consistent with a more accessible dimetal binding/radical site and a lower affinity for Fe2+ in EBV R2 than in Escherichia coli R2. Comparison with previous studies of RNR R2s from mouse, bacteria, and herpes viruses, demonstrates that finely tuned electronic properties of the radical exist within the same RNR R2 Ia class

Evolution of pathogenicity and sexual reproduction in eight Candida genomes

Candida species are the most common cause of opportunistic fungal infection worldwide. Here we report the genome sequences of six Candida species and compare these and related pathogens and non-pathogens. There are significant expansions of cell wall, secreted and transporter gene families in pathogenic species, suggesting adaptations associated with virulence. Large genomic tracts are homozygous in three diploid species, possibly resulting from recent recombination events. Surprisingly, key components of the mating and meiosis pathways are missing from several species. These include major differences at the mating-type loci (MTL); Lodderomyces elongisporus lacks MTL, and components of the a1/2 cell identity determinant were lost in other species, raising questions about how mating and cell types are controlled. Analysis of the CUG leucine-to-serine genetic-code change reveals that 99% of ancestral CUG codons were erased and new ones arose elsewhere. Lastly, we revise the Candida albicans gene catalogue, identifying many new genes.publishe

Photometric multi-site campaign on the open cluster NGC 884 I. Detection of the variable stars

CONTEXT: Recent progress in the seismic interpretation of field beta Cep stars has resulted in improvements of the physics in the stellar structure and evolution models of massive stars. Further asteroseismic constraints can be obtained from studying ensembles of stars in a young open cluster, which all have similar age, distance and chemical composition. AIMS: To improve our comprehension of the beta Cep stars, we studied the young open cluster NGC 884 to discover new B-type pulsators, besides the two known beta Cep stars, and other variable stars. METHODS: An extensive multi-site campaign was set up to gather accurate CCD photometry time series in four filters (U, B, V, I) of a field of NGC884. Fifteen different instruments collected almost 77500 CCD images in 1286 hours. The images were calibrated and reduced to transform the CCD frames into interpretable differential light curves. Various variability indicators and frequency analyses were applied to detect variable stars in the field. Absolute photometry was taken to deduce some general cluster and stellar properties. RESULTS: We achieved an accuracy for the brightest stars of 5.7 mmag in V, 6.9 mmag in B, 5.0 mmag in I and 5.3 mmag in U. The noise level in the amplitude spectra is 50 micromag in the V band. Our campaign confirms the previously known pulsators, and we report more than one hundred new multi- and mono-periodic B-, A- and F-type stars. Their interpretation in terms of classical instability domains is not straightforward, pointing to imperfections in theoretical instability computations. In addition, we have discovered six new eclipsing binaries and four candidates as well as other irregular variable stars in the observed field.Comment: Accepted for publication in Astronomy and Astrophysics, 21 pages, 14 figures, 4 tables. The full appendix is available at http://www.ster.kuleuven.be/~sophies/Appendix.pdf (74 MB, 169 pages, 343 figures, 1 table

European agricultural landscapes, common agricultural policy and ecosystem services: a review

Since the 1950s, intensification and scale enlargement of agriculture have changed agricultural landscapes across Europe. The intensification and scale enlargement of farming was initially driven by the large-scale application of synthetic fertilizers, mechanization and subsidies of the European Common Agricultural Policy (CAP). Then, after the 1990s, a further intensification and scale enlargement, and land abandonment in less favored areas was caused by globalization of commodity markets and CAP reforms. The landscape changes during the past six decades have changed the flows and values of ecosystem services. Here, we have reviewed the literature on agricultural policies and management, landscape structure and composition, and the contribution of ecosystem services to regional competitiveness. The objective was to define an analytical framework to determine and assess ecosystem services at the landscape scale. In contrast to natural ecosystems, ecosystem service flows and values in agricultural landscapes are often a result of interactions between agricultural management and ecological structures. We describe how land management by farmers and other land managers relates to landscape structure and composition. We also examine the influence of commodity markets and policies on the behavior of land managers. Additionally, we studied the influence of consumer demand on flows and values of the ecosystem services that originate from the agricultural landscape

Comparative analyses of the Escherichia coli ketapantoate hydroxymethyltransferase crystal structure confims that it is a member of the (betaalpha)(8) phosphoenolpyruvate/pyruvate superfamily.

Escherichia coli ketopantoate hydroxymethyltransferase (KPHMT) catalyzes the first step in the biosynthesis pathway of pantothenate (vitamin B(5)), the transfer of a hydroxymethyl group onto α-ketoisovalerate. Here we describe a detailed comparative analysis of the KPHMT crystal structure and the identification of structural homologues, some of which have remarkable similarities in their active sites, modes of binding to substrates, and mechanisms. We show that KPHMT forms a family within the phosphoenolpyruvate/pyruvate superfamily. Based on the analysis, we propose that in this superfamily there should be a subdivision into two groups. This paper completes our structural analysis of the E. coli enzymes in the pantothenate pathway

Die wissenschaftliche Hausarbeit an der Charité: ein Projektbericht zu Konzept, Umsetzung, Studierendenevaluation und Lernerfolg

Aim: Better training in scientific skills, such as the ability to conduct research independently, has been one of the main drivers of reform in medical education. The aim of this article is to report on the scientific term paper module in the modular curriculum of medicine (MCM) at the Charité. This module is an established example of undergraduate medical students conducting their own scientific investigations.Project outline: A faculty-wide, outcome-oriented process resulted in a four-week module for writing a scientific term paper in the 6th semester of the MCM as part of a longitudinal science curriculum. Acquired competencies were assessed through a written term paper and an oral presentation. Two student cohorts (winter terms 2013 and 2014) were surveyed on how they rated the module concept, organizational aspects and the quality of support. We further analysed the chosen topics of the papers as well as student assessment results.Results: The student evaluation (return rates of 193 and 197, 71% and 77%) showed high overall satisfaction with the module. This result was evident in the high rating of the module concept and organizational aspects, a positive attitude towards scientific research, and strong motivation to pursue further scientific research. There was a wide spectrum of term paper topics with a focus on literature reviews. Most of the student work was assessed as good or very good.Conclusion: The scientific term paper module has proven itself as a curricular concept for students to perform own scientific research in the MCM, with strong acceptance and good performance by students. This project report can serve as basis and guidance for development and further improvements to promote scientific competencies in undergraduate medical education in other faculties.Zielsetzung: Die bessere Vermittlung wissenschaftlicher Kompetenzen, darunter die Fähigkeit zur eigenständigen wissenschaftlichen Arbeit, bildet eine der Haupttriebfedern für die Reform des Medizinstudiums. Ziel dieses Projektberichtes ist es, die wissenschaftliche Hausarbeit im Modellstudiengang Medizin (MSM) der Charité vorzustellen. Sie ist ein etabliertes Praxisbeispiel von eigener wissenschaftlicher Arbeit im Medizinstudium.Projektbeschreibung: In einem fakultätsweiten, outcome-orientierten Prozess wurde ein 4-wöchiges Modul zur Erstellung einer wissenschaftlichen Hausarbeit im 6. Semester des MSM als Teil eines longitudinalen Wissenschaftscurriculums entwickelt und implementiert. Der Kompetenzerwerb wird auf Basis einer schriftlichen Hausarbeit und einer mündlichen Präsentation geprüft. In zwei Studierendenkohorten im Wintersemester 2013 und 2014 wurden Fragen zum Konzept des Moduls, zu organisatorischen Aspekten und zur Betreuungsqualität evaluiert. Außerdem wurden Statistiken zu den bearbeiteten Themen erhoben und die Ergebnisse der Leistungsbewertungen ausgewertet.Ergebnisse: Die Studierendenevaluation (Rücklaufquote 193 bzw. 197 Studierende; 71% bzw. 77%) zeigte eine hohe Gesamtzufriedenheit auf. Diese manifestierte sich in einer guten Bewertung des Modulkonzeptes und der organisatorischen Aspekte sowie einer sehr positiven Einstellung zum Thema wissenschaftliches Arbeiten und einer hohen Motivation für eine weitere wissenschaftliche Arbeit. Die Themen der Hausarbeit waren weit gestreut mit Schwerpunkt auf Literaturarbeiten. Die Leistungen der Studierenden wurden zum Großteil als gut oder sehr gut bewertet.Schlussfolgerung: Die wissenschaftliche Hausarbeit hat sich als curriculares Konzept für die Umsetzung von eigener wissenschaftlicher Arbeit im MSM mit hoher Akzeptanz und guter Leistung seitens der Studierenden bewährt. Dieser Projektbericht kann anderen Fakultäten als Grundlage und Orientierung für Entwicklung bzw. Weiterentwicklung eigener Programme zur Förderung von Wissenschaftskompetenz im Medizinstudium dienen

Molecular basis for inner kinetochore configuration through RWD domain-peptide interactions

Kinetochores are dynamic cellular structures that connect chromosomes to microtubules. They form from multi-protein assemblies that are evolutionarily conserved between yeasts and humans. One of these assemblies-COMA-consists of subunits Ame1 CENP-U , Ctf19 CENP-P , Mcm21 CENP-O and Okp1 CENP-Q . A description of COMA molecular organization has so far been missing. We defined the subunit topology of COMA, bound with inner kinetochore proteins Nkp1 and Nkp2, from the yeast Kluyveromyces lactis, with nanoflow electrospray ionization mass spectrometry, and mapped intermolecular contacts with hydrogen-deuterium exchange coupled to mass spectrometry. Our data suggest that the essential Okp1 subunit is a multi-segmented nexus with distinct binding sites for Ame1, Nkp1-Nkp2 and Ctf19-Mcm21. Our crystal structure of the Ctf19-Mcm21 RWD domains bound with Okp1 shows the molecular contacts of this important inner kinetochore joint. The Ctf19-Mcm21 binding motif in Okp1 configures a branch of mitotic inner kinetochores, by tethering Ctf19-Mcm21 and Chl4 CENP-N -Iml3 CENP-L . Absence of this motif results in dependence on the mitotic checkpoint for viability