On the ground state of solids with strong electron correlations

We formulate the calculation of the ground-state wavefunction and energy of a system of strongly correlated electrons in terms of scattering matrices. A hierarchy of approximations is introduced which results in an incremental expansion of the energy. The present approach generalizes previous work designed for weakly correlated electronic systems.Comment: 17 pages, Latex(revtex

Electron correlations for ground state properties of group IV semiconductors

Valence energies for crystalline C, Si, Ge, and Sn with diamond structure have been determined using an ab-initio approach based on information from cluster calculations. Correlation contributions, in particular, have been evaluated in the coupled electron pair approximation (CEPA), by means of increments obtained for localized bond orbitals and for pairs and triples of such bonds. Combining these results with corresponding Hartree-Fock (HF) data, we recover about 95 % of the experimental cohesive energies. Lattice constants are overestimated at the HF level by about 1.5 %; correlation effects reduce these deviations to values which are within the error bounds of this method. A similar behavior is found for the bulk modulus: the HF values which are significantly too high are reduced by correlation effects to about 97 % of the experimental values.Comment: 22 pages, latex, 2 figure

Deconstructing maternal sensitivity: Predictive relations to mother-child attachment in home and laboratory settings

Despite the well-documented importance of parental sensitivity for child development, there is a lack of consensus regarding how best to assess it. We investigated the factor structure of maternal caregiving behavior as assessed at 12 months by the Maternal Behavior Q-Sort (Pederson, Moran, & Bento, 1999) with 274 mother-infant dyads. Subsequently, we examined associations between these empirically-derived dimensions and child attachment, assessed in the home and laboratory (final N = 157). Three dimensions of maternal behavior were identified, corresponding fairly closely to Ainsworth’s original scales. They were labeled Cooperation/Attunement, Positivity, and Accessibility/Availability. Only Cooperation/Attunement consistently predicted home-based attachment at 15 months and 2 years, and at comparable strength to the overall sensitivity score, suggesting that this construct may be central to sensitivity. At 18 months, compared to their primarily secure counterparts, different types of laboratory-assessed insecure attachment were associated with different patterns of maternal behavior. Mothers in avoidant relationships (n = 18) were low on Cooperation/Attunement and Accessibility/Availability, but fairly high on Positivity. Mothers of disorganized infants (n = 11) were Cooperative/Attuned but somewhat less Positive toward, and less Accessible/Available to, their infants. A multi-dimensional approach to parental behavior may facilitate the identification of parenting precursors of insecure parent-child relationships

Ergebnisse der NUBBEK-Studie zu Qualitätsdimensionen in der Kindertagesbetreuung: Interpretation aus bindungstheoretischer Sicht

"Ziel dieses Beitrags ist es, die verschiedenen Qualitätsdimensionen in der außerfamiliären Tagesbetreuung von Kindern im Kindergartenalter anhand der Daten der Nationalen Untersuchung zur Bildung, Betreuung und Erziehung in der frühen Kindheit (NUBBEK) näher zu betrachten und daraus Implikationen für Politik und Praxis abzuleiten. Die Bindungstheorie dient dabei als theoretisches Rahmenmodell. Verbesserungsbedarf zeigt sich vor allem im Bereich Betreuung und Pflege der Kinder, aber auch in den Bereichen Lesen, Mathematik, Naturwissenschaften und Diversität. Aus Sicht der Bindungstheorie sollten Verbesserungsmaßnahmen jedoch nicht isoliert auf einzelne Fähigkeitsbereiche abzielen, sondern immer den Beziehungsaspekt als wichtige Grundvoraussetzung für erfolgreiches Lernen mit einbeziehen." (Autorenreferat)"Using data from the national study on education and care in early childhood (NUBBEK), the authors examined different dimensions of center based child care quality. Attachment theory serves as a theoretical framework to formulate recommendations for policymakers and practitioners. The data suggest a need of improvement especially in the area of Personal Care Routines, but also in the domains Literacy, Mathematics, Science/Environment and Diversity. However, based on attachment theory efforts to improve quality should not only focus on single competence domains, but always take into account the studentcaregiver- relationship as a major precondition for successful learning." (author's abstract

Influence of substituents on bond lengths

Pseudopotential SCF calculations for Y3C-X, Y=H, F; X=H, F, Cl, PH2, PF2 and a simple model, simulating the substituents by a homogeneous, electric field, are presented in order to rationalize the substitution effect on the C-X bond

Modulation of the nucleation rate pre-exponential in a low-temperature Ising system

A metastable lattice gas with nearest-neighbor interactions and continuous-time dynamics is studied using a generalized Becker-Doring approach in the multidimensional space of cluster configurations. The pre-exponential of the metastable state lifetime (inverse of nucleation rate) is found to exhibit distinct peaks at integer values of the inverse supersaturation. Peaks are unobservable (infinitely narrow) in the strict limit T->0, but become detectable and eventually dominate at higher temperatures.Comment: 4 pages, 2 Postscript figures, LaTeX, submitted to Phys. Rev. Lett. Changes: updated references, re-written section around eqs.(5),(6), typos, minor wording changes in conclusion and other parts of text (mostly in response to referees' comments). Paper resubmitted to PR

TRPM7 Kinase Controls Calcium Responses in Arterial Thrombosis and Stroke in Mice

Objective: TRPM7 (transient receptor potential cation channel, subfamily M, member 7) is a ubiquitously expressed bifunctional protein comprising a transient receptor potential channel segment linked to a cytosolic alpha-type serine/threonine protein kinase domain. TRPM7 forms a constitutively active Mg2+ and Ca2+ permeable channel, which regulates diverse cellular processes in both healthy and diseased conditions, but the physiological role of TRPM7 kinase remains largely unknown. Approach and Results: Here we show that point mutation in TRPM7 kinase domain deleting the kinase activity in mice (Trpm7(R/R)) causes a marked signaling defect in platelets. Trpm7(R/R) platelets showed an impaired PIP2 (phosphatidylinositol-4,5-bisphosphate) metabolism and consequently reduced Ca2+ mobilization in response to stimulation of the major platelet receptors GPVI (glycoprotein VI), CLEC-2 (C-type lectin-like receptor), and PAR (protease-activated receptor). Altered phosphorylation of Syk (spleen tyrosine kinase) and phospholipase C gamma 2 and beta 3 accounted for these global platelet activation defects. In addition, direct activation of STIM1 (stromal interaction molecule 1) with thapsigargin revealed a defective store-operated Ca2+ entry mechanism in the mutant platelets. These defects translated into an impaired platelet aggregate formation under flow and protection of the mice from arterial thrombosis and ischemic stroke in vivo. Conclusions: Our results identify TRPM7 kinase as a key modulator of phospholipase C signaling and store-operated Ca2+ entry in platelets. The protection of Trpm7(R/R) mice from acute ischemic disease without developing intracranial hemorrhage indicates that TRPM7 kinase might be a promising antithrombotic target

Survey of the Current Activities in the Field of Modeling the Space Debris Environment at TU Braunschweig

The Institute of Space Systems at Technische Universität Braunschweig has long-term experience in the field of space debris modeling. This article reviews the current state of ongoing research in this area. Extensive activities are currently underway to update the European space debris model MASTER. In addition to updating the historical population, the future evolution of the space debris environment is also being investigated. The competencies developed within these activities are used to address current problems with regard to the possibility of an increasing number of catastrophic collisions. Related research areas include, for example, research in the field of orbit determination and the simulation of sensor systems for the acquisition and cataloging of orbital objects. In particular, the ability to provide simulated measurement data for object populations in almost all size ranges is an important prerequisite for these investigations. Some selected results on the distribution of space debris on Earth orbit are presented in terms of spatial density. Furthermore, specific fragmentation events will be discussed

Does OKT3 increase the risk of recurrent hepatitis B in patients transplanted for hepatitis B?

No Abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/35275/1/500060623_ftp.pd