Consequences of Postnatally Elevated Insulin-Like Growth Factor-II in Transgenic Mice: Endocrine Changes and Effects on Body and Organ Growth.

Insulin-like growth factor-II (IGF-II) is an important regulator of embryonic growth and differentiation, but its function in postnatal life is unclear. To address this point, we generated transgenic mice harboring fusion genes in which a human IGF-II complementary DNA is placed under the transcriptional control of the rat phosphoenolpyruvate carboxykinase promoter. Transgene-specific messenger RNA was detected in liver, kidney, and several parts of the gut. Serum IGF-II levels in transgenic mice were 2-3 times higher than those in controls and increased after starvation. Circulating IGF-I correlated negatively and IGF-binding protein-2 (IGFBP-2) positively with IGF-II levels, suggesting that IGF-I is displaced from IGFBPs by IGF-II and that IGFII is a major regulator of IGFBP-2. Serum levels of IGFBP-3 and IGFBP-4 tended to be higher in phosphoenolpyruvate carboxykinase- IGF-II transgenic mice than in controls, as evaluated by ligand blot analysis. Starvation reduced serum IGF-I, but increased IGFBP-2 in transgenic mice more markedly than in controls. Fasting insulin levels were significantly reduced in transgenic mice, whereas glucose levels were not influenced by elevated IGF-II. The body growth of 4- and 12- week-old mice was not significantly influenced by elevated IGF-II, but transgenic mice displayed increased kidney and testis weight at the age of 4 weeks, and increased adrenal weight at the age of 12 weeks. Our results demonstrate that elevated IGF-II in postnatal life has multiple endocrine consequences and subtle time-specific effects on organ growth

Selektion und Übergänge im Bildungssystem. Einleitung in den Thementeil

Im Zuge der wieder erwachten Aufmerksamkeit für den Zusammenhang von Bildung und sozialer Ungleichheit richtet sich ein Schwerpunkt der empirischen Bildungsforschung vor allem auch auf die Übergänge und Statuspassagen im Bildungssystem: Bereits der Verlauf der Elementarbildung, die Einmündung in die Grundschule, insbesondere der Übergang von der Grundschule in die Sekundarstufe, Schulformwechsel und Klassenwiederholungen im Verlauf der gesamten Schulkarriere sowie der Übergang nach der Sekundarstufe I sind dabei die wichtigsten Zäsuren und Markierer. Das deutsche Bildungssystem scheint somit – im internationalen Vergleich besonders deutlich – wie ein Hindernisparcours strukturiert, mit vielen und besonders frühen Schaltstellen der Selektion. (DIPF/Orig.

Crossover between different regimes of inhomogeneous superconductivity in planar superconductor-ferromagnet hybrids

We studied experimentally the effect of a stripe-like domain structure in a ferromagnetic BaFe_{12}O_{19} substrate on the magnetoresistance of a superconducting Pb microbridge. The system was designed in such a way that the bridge is oriented perpendicular to the domain walls. It is demonstrated that depending on the ratio between the amplitude of the nonuniform magnetic field B_0, induced by the ferromagnet, and the upper critical field H_{c2} of the superconducting material, the regions of the reverse-domain superconductivity in the H-T plane can be isolated or can overlap (H is the external magnetic field, T is temperature). The latter case corresponds to the condition B_0/H_{c2}<1 and results in the formation of superconductivity above the magnetic domains of both polarities. We discovered the regime of edge-assisted reverse-domain superconductivity, corresponding to localized superconductivity near the edges of the bridge above the compensated magnetic domains. Direct verification of the formation of inhomogeneous superconducting states and external-field-controlled switching between normal state and inhomogeneous superconductivity were obtained by low-temperature scanning laser microscopy.Comment: 11 pages, 12 figure

Der individuelle Orientierungsrahmen von Kindern und der Übergang in die Sekundarstufe. Erste Ergebnisse eines qualitativen Längsschnitts

Der Beitrag führt in die Perspektive einer qualitativen Längsschnittstudie zur biographischen Verarbeitung schulischer Selektionsereignisse ein. Ausgehend von der Bedeutsamkeit schulischer Übergänge für die Schullaufbahn und der forschungspragmatisch vernachlässigten Schülerperspektive wird anhand exemplarischer Schülerinterviews zum Ende der 4. und zu Beginn der 5. Klasse nach dem Zusammenhang der kindlichen Orientierungsrahmen und dem vollzogenen Übergang gefragt. Abschließend wird mit ersten theoretischen und typologischen Ableitungen der Ertrag eines solchen Forschungszugangs angedeutet. (DIPF/Orig.)This contribution inducts into the perspective of a qualitative longitudinal section concerning the biographical coping of selection processes at school. Starting point is the assumption of the significance of academic transitions for the school career as well as the neglect of the pupil\u27s perspective. On the basis of exemplarily interviews with pupils at the end of the fourth and at the beginning of the fifth form, the relation between the infantile frame of orientation and the fulfilled transition is compiled here. As conclusion first typological and theoretical deductions are made, which indicate the output of this research access. (DIPF/Orig.

Low-mass lepton pair production at large transverse momentum

We study the transverse momentum distribution of low-mass lepton pairs produced in hadronic scattering, using the perturbative QCD factorization approach. We argue that the distribution at large transverse momentum, $Q_T \gg Q$, with the pair's invariant mass $Q$ as low as $Q \sim \Lambda_{\mathrm{QCD}}$, can be systematically factorized into universal parton-to-lepton pair fragmentation functions, parton distributions, and perturbatively calculable partonic hard parts evaluated at a short distance scale $\sim {\cal O}(1/Q_T)$. We introduce a model for the input lepton pair fragmentation functions at a scale $\mu_0\sim 1$ GeV, which are then evolved perturbatively to scales relevant at RHIC. Using the evolved fragmentation functions, we calculate the transverse momentum distributions in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions at RHIC. We also discuss the sensitivity of the transverse momentum distribution of low-mass lepton pairs to the gluon distribution.Comment: 16 pages, 11 figures, revised version to appear in Phys. Rev.

A multiwavlength study of PSR B0628-28: The first overluminous rotation-powered pulsar?

The ROSAT source RX J0630.8-2834 was suggested by positional coincidence to be the X-ray counterpart of the old field pulsar PSR B0628-28. This association, however, was regarded to be unlikely based on the computed energetics of the putative X-ray counterpart. In this paper we report on multiwavelength observations of PSR B0628-28 made with the ESO/NTT observatory in La Silla, the Jodrell Bank radio observatory and XMM-Newton. Although the optical observations do not detect any counterpart of RX J0630.8-2834 down to a limiting magnitude of V=26.1 mag and B=26.3 mag, XMM-Newton observations finally confirmed it to be the pulsar's X-ray counterpart by detecting X-ray pulses with the radio pulsar's spin-period. The X-ray pulse profile is characterized by a single broad peak with a second smaller peak leading the main pulse component by ~144 degree. The fraction of pulsed photons is (38 +- 7)% with no strong energy dependence in the XMM-Newton bandpass. The pulsar's X-ray spectrum is well described by a single component power law with photon index 2.63^{+0.23}_{-0.15}, indicating that the pulsar's X radiation is dominated by non-thermal emission processes. A low level contribution of thermal emission from residual cooling or from heated polar caps, cannot be excluded. The pulsar's spin-down to X-ray energy conversion efficiency is obtained to be ~16% for the radio dispersion measure inferred pulsar distance. If confirmed, PSR B0628-28 would be the first X-ray overluminous rotation-powered pulsar identified among all ~1400 radio pulsars known today.Comment: Accepted for publication in ApJ. Find a paper copy with higher resolution images at ftp://ftp.xray.mpe.mpg.de/people/web/astro-ph-0505488_rev2.pd