Light-Cone Distribution Amplitudes for Heavy-Quark Hadrons

We construct parametrizations of light-cone distribution amplitudes (LCDAs) for B-mesons and Lambda_b-baryons that obey various theoretical constraints, and which are simple to use in factorization theorems relevant for phenomenological applications in heavy-flavour physics. In particular, we find the eigenfunctions of the Lange-Neubert renormalization kernel, which allow for a systematic implementation of renormalization-group evolution effects for both B-meson and \Lambda_b-baryon decays. We also present a new strategy to construct LCDA models from momentum-space projectors, which can be used to implement Wandzura-Wilczek--like relations, and which allow for a comparison with theoretical approaches that go beyond the collinear limit for the light-quark momenta in energetic heavy-hadron decays.Comment: 39 pages, 11 figure

Muon-electron backward scattering: a prime example for endpoint singularities in SCET

We argue that energetic muon-electron scattering in the backward direction can be viewed as a template case to study the resummation of large logarithms related to endpoint divergences appearing in the effective-theory formulation of hard-exclusive processes. While it is known since the mid sixties that the leading double logarithms from QED corrections resum to a modified Bessel function on the amplitude level, the modern formulation in Soft-Collinear Effective Theory (SCET) shows a surprisingly complicated and iterative pattern of endpoint-divergent convolution integrals. In contrast to the bottom-quark induced $h \to \gamma\gamma$ decay, for which a renormalized factorization theorem has been proposed recently, we find that rapidity logarithms generate an infinite tower of collinear-anomaly exponents. This can be understood as a generic consequence of the underlying $2\to 2$ kinematics. Using endpoint refactorization conditions for the collinear matrix elements, we show how the Bessel function is reproduced in the effective theory from consistency relations between quantities in a "bare" factorization theorem.Comment: v2: Discussions in Sections 2.3 and 3.2 slightly modified. Conclusions unchanged. Matches published versio

Valproate-associated reversible encephalopathy in a 3-year-old girl with Pallister-Killian syndrome

Valproic acid (VPA) is considered to be a drug of first choice for the therapy of generalized and focal epilepsies, including special epileptic syndromes. The drug is usually well tolerated, rare serious complications may occur in some patients, including hemorrhagic pancreatitis, coagulapathies, bone marrow suppression, VPA-induced hepatotoxicity and encephalopathy. We report a case of VPA-associated encephalopathy without hyperammonemia in a 3-year-old girl with Pallister-Killian-Syndrom, combined with a mild hepatopathy and thrombopathy. After withdrawal of VPA, the clinical symptoms and the electroencephalography-alterations vanished rapidly

Collaborative inquiry learning: models, tools, and challenges

Collaborative inquiry learning is one of the most challenging and exciting ventures for today’s schools. It aims at bringing a new and promising culture of teaching and learning into the classroom where students in groups engage in self-regulated learning activities supported by the teacher. It is expected that this way of learning fosters students’ motivation and interest in science, that they learn to perform steps of inquiry similar to scientists and that they gain knowledge on scientific processes. Starting from general pedagogical reflections and science standards the article reviews some prominent models of inquiry learning. This comparison results in a set of inquiry processes being the basis for cooperation in the scientific network NetCoIL. Inquiry learning is conceived in several ways with emphasis on different processes. For an illustration of the spectrum, some main conceptions of inquiry and their focuses are described. In the next step, the article describes exemplary computer tools and environments from within and outside the NetCoIL network that were designed to support processes of collaborative inquiry learning. These tools are analysed by describing their functionalities as well as effects on student learning known from the literature. The article closes with challenges for further developments elaborated by the NetCoIL network

CIRCE Version 1.0: Beam Spectra for Linear Collider Physics

I describe parameterizations of realistic $e^\pm$- and $\gamma$-beam spectra at future linear $e^+e^-$-colliders. Emphasis is put on simplicity and reproducibility of the parameterizations, supporting reproducible physics simulations. The parameterizations are implemented in a library of distribution functions and event generators.Comment: 26 pages, LaTeX (using amsmath.sty), PostScript figures included, paper saving version formatted for A4 available from ftp://crunch.ikp.physik.th-darmstadt.de/pub/preprints/IKDA-96-13.ps.g

Diversity of DNA replication in the archaea

DNA replication is arguably the most fundamental biological process. On account of their shared evolutionary ancestry, the replication machinery found in archaea is similar to that found in eukaryotes. DNA replication is initiated at origins and is highly conserved in eukaryotes, but our limited understanding of archaea has uncovered a wide diversity of replication initiation mechanisms. Archaeal origins are sequence‐based, as in bacteria, but are bound by initiator proteins that share homology with the eukaryotic origin recognition complex subunit Orc1 and helicase loader Cdc6). Unlike bacteria, archaea may have multiple origins per chromosome and multiple Orc1/Cdc6 initiator proteins. There is no consensus on how these archaeal origins are recognised— some are bound by a single Orc1/Cdc6 protein while others require a multi‐ Orc1/Cdc6 complex. Many archaeal genomes consist of multiple parts—the main chromosome plus several megaplasmids—and in polyploid species these parts are present in multiple copies. This poses a challenge to the regulation of DNA replication. However, one archaeal species (Haloferax volcanii) can survive without replication origins; instead, it uses homologous recombination as an alternative mechanism of initiation. This diversity in DNA replication initiation is all the more remarkable for having been discovered in only three groups of archaea where in vivo studies are possible

Schüler modellieren den Treibhauseffekt: Unterrichtskonzept und Ergebnisse einer Erprobung in der Sek II

Dieser Beitrag stellt ein Unterrichtskonzept für die Oberstufe vor, das im Rahmen des EU-Projekts Co-Lab (Collaborative Laboratories for Europe) am IPN entwickelt worden ist und berichtet über ausgewählte Ergebnisse einer Piloterprobung. Die Unterrichtseinheit behandelt physikalische Grundzüge des Treibhauseffekts, die die Schülerinnen und Schüler durch selbstständige grafische Modellierung („Stock and Flow“; System Dynamics) am PC entdecken bzw. konstruieren sollen. Dabei forschen die Lernenden kollaborativ in kleinen Gruppen à 3-4. Neben einigen obligatorischen Teilen bietet das Konzept optionale Module an, so dass die Einheit einen Umfang zwischen 10 und 30 Stunden haben kann. Die Einheit ist in sieben Oberstufen-Kursen der Fächer Physik und Biologie erprobt worden. In einer Pilotuntersuchung wurden vor und nach dem Co-Lab-Unterricht Schülerfragebögen eingesetzt, um u.a. Lernzuwächse beim Modellieren zu ermitteln. Je nach Item liegen von 22 bis 65 Schülerinnen und Schülern Vor- und Nachtestdaten vor. Es zeigt sich, dass nach Modellierung des Treibhauseffekts im Co-Lab-Unterricht deutlich mehr Schülerinnen und Schüler als vorher in der Lage waren, im Test bei einer Thermostat-regulierten Raumheizung eine Prozesswiederholung sowie die Strukturen des Energiedurchflusses und der regulierenden Rückkopplung zu entdecken und zu modellieren

The role of the teacher in computer-supported collaborative inquiry learning

The article presents an analysis of practices in teaching with computer-supported collaborative inquiry learning environments. We describe the role of the teacher in computer-supported collaborative inquiry learning by five principles which span the whole instructional process, from the preparation of the lesson up to the assessment of learning achievement. For successful implementation of computer-supported projects the teacher has to (1) envision the lesson, (2) enable collaboration, (3) encourage students, (4) ensure learning, and (5) evaluate achievement. We analyse classroom scenarios provided by eight teachers or mentors who implemented one of four different approaches developed by multimedia researchers: WISE, Modeling Across the Curriculum, Co-Lab, or ReCoIL. Teachers or mentors responded to a semistructured questionnaire about their experiences in implementing the inquiry lesson. A comparison of different classroom scenarios according to the mentioned five principles informed our analysis of teacher activities that contribute to the success of student inquiry while using such technology-enhanced approaches. We conclude with a discussion of the often neglected role of the teacher in computer-supported learning

Schüler modellieren den Treibhauseffekt: Unterrichtskonzept und Ergebnisse einer Erprobung in der Sek II

Dieser Beitrag stellt ein Unterrichtskonzept für die Oberstufe vor, das im Rahmen des EU-Projekts Co-Lab (Collaborative Laboratories for Europe) am IPN entwickelt worden ist und berichtet über ausgewählte Ergebnisse einer Piloterprobung. Die Unterrichtseinheit behandelt physikalische Grundzüge des Treibhauseffekts, die die Schülerinnen und Schüler durch selbstständige grafische Modellierung („Stock and Flow“; System Dynamics) am PC entdecken bzw. konstruieren sollen. Dabei forschen die Lernenden kollaborativ in kleinen Gruppen à 3-4. Neben einigen obligatorischen Teilen bietet das Konzept optionale Module an, so dass die Einheit einen Umfang zwischen 10 und 30 Stunden haben kann. Die Einheit ist in sieben Oberstufen-Kursen der Fächer Physik und Biologie erprobt worden. In einer Pilotuntersuchung wurden vor und nach dem Co-Lab-Unterricht Schülerfragebögen eingesetzt, um u.a. Lernzuwächse beim Modellieren zu ermitteln. Je nach Item liegen von 22 bis 65 Schülerinnen und Schülern Vor- und Nachtestdaten vor. Es zeigt sich, dass nach Modellierung des Treibhauseffekts im Co-Lab-Unterricht deutlich mehr Schülerinnen und Schüler als vorher in der Lage waren, im Test bei einer Thermostat-regulierten Raumheizung eine Prozesswiederholung sowie die Strukturen des Energiedurchflusses und der regulierenden Rückkopplung zu entdecken und zu modellieren

Capillary microscopy and hemorheology in children during antiepileptic monotherapy with carbamazepine and valproate

SummaryThe interactions of epilepsy and antiepileptic therapy an one hand and cardiovascular system on the other hand are multiple and complex. Antiepileptic drugs (AEDs) cause alterations of serum lipids and of the fatty acid composition of the membranes. Homocystein, known to induce vascular endothelial damage was found to be elevated in patients on valproate (VPA) and carbamazepine (CBZ) therapy. Marked coronary artherosclerosis and myocardial infarction may already occur in children treated with CBZ. Community based studies corroborated a higher incidence of myocardial infarction, peripheral vascular diseases hypercholesterinemia, left ventricle hypertrophy and stroke in patients with epilepsy. In this context, we wanted to elevate changes of microcirculation related to AEDs commonly prescribed such as VPA and CBZ.Capillary microscopy is a non-invasive technique for measuring the velocity of red blood cells and for determining nutritional blood flow in the capillaries of the skin. It can easily be performed in children.The aim of this study was to look for possible effects an antiepileptic monotherapy with carbamazepine or valproate has on the peripheral microcirculation in epileptic children.We were able to examine 14 children with CBZ and 24 children with VPA, recruited in our neuropediatric Unit. The results were compared to normative values, determined in former analyses of 207 healthy children. We found significant differences in capillary density, tortuous index of the capillaries, capillary diameter and flow rate of erythrocytes for both antiepileptic drugs. Additionally, there were changes in plasma viscosity and the aggregation of erythrocytes.These microcapillary effects could be of special interest in the relationship of a long-term antiepileptic therapy and the development of vascular diseases.We suggest that the influence of AEDs on microcirculation should also be considered in further studies on cardiovascular changes in patients with antiepileptic long-term medication