Changes in trabecular bone, hematopoiesis and bone marrow vessels in aplastic anemia, primary osteoporosis, and old age

Retrospective histologic analyses of bone biopsies and of post mortem samples from normal persons of different age groups, and of bone biopsies of age- and sex-matched groups of patients with primary osteoporosis and aplastic anemia show characteristic age dependent as well as pathologic changes including atrophy of osseous trabeculae and of hematopoiesis, and changes in the sinusoidal and arterial capillary compartments. These results indicate the possible role of a microvascular defect in the pathogenesis of osteoporosis and aplastic anemia

Multiscaling in Ising quantum chains with random Hilhorst-van Leeuwen perturbations

We consider the influence on the surface critical behaviour of a quantum Ising chain of quenched random surface perturbations decaying as a power of the distance from the surface (random Hilhorst-van Leeuwen models). We study, analytically and numerically, the multiscaling behaviour of the surface magnetization and the surface energy density in the case of marginal perturbations.Comment: 14 pages, 5 figures, LaTeX2e, epsf, elsar

Fall feeding aggregations of fin whales off Elephant Island (Antarctica)

From 13 March to 09 April 2012 Germany conducted a fisheries survey on board RV Polarstern in the Scotia Sea (Elephant Island - South Shetland Island - Joinville Island area) under the auspices of CCAMLR. During this expedition, ANT-XXVIII/4, an opportunistic marine mammal survey was carried out. Data were collected for 26 days along the externally preset cruise track, resulting in 295 hrs on effort. Within the study area 248 sightings were collected, including three different species of baleen whales (fin whale (Balaenoptera physalus), humpback whale (Megaptera novaeangliae), and Antarctic minke whale (Balaenoptera bonaerensis) and one toothed whale species, killer whale (Orcinus orca). More than 62% of the sightings recorded were fin whales (155 sightings) which were mainly related to the Elephant Island area (116 sightings). Usual group sizes of the total fin whale sightings ranged from one to five individuals, also including young animals associated with adults during some encounters. Larger groups of more than 20 whales, and on two occasions more than 100 indivuduals, were observed as well. These large pods of fin whales were observed feeding in shallow waters (< 300 m) on the north-western shelf off Elephant Island, concordant with large aggregations of Antarctic krill (Euphausia superba). This observation suggests that Elephant Island constitutes an important feeding area for fin whales in early austral fall, with possible implications regarding the regulation of (krill) fisheries in this area

Partial survival and inelastic collapse for a randomly accelerated particle

We present an exact derivation of the survival probability of a randomly accelerated particle subject to partial absorption at the origin. We determine the persistence exponent and the amplitude associated to the decay of the survival probability at large times. For the problem of inelastic reflection at the origin, with coefficient of restitution $r$, we give a new derivation of the condition for inelastic collapse, $r<r_c=e^{-\pi/\sqrt{3}}$, and determine the persistence exponent exactly.Comment: 6 page

First-passage and extreme-value statistics of a particle subject to a constant force plus a random force

We consider a particle which moves on the x axis and is subject to a constant force, such as gravity, plus a random force in the form of Gaussian white noise. We analyze the statistics of first arrival at point $x_1$ of a particle which starts at $x_0$ with velocity $v_0$. The probability that the particle has not yet arrived at $x_1$ after a time $t$, the mean time of first arrival, and the velocity distribution at first arrival are all considered. We also study the statistics of the first return of the particle to its starting point. Finally, we point out that the extreme-value statistics of the particle and the first-passage statistics are closely related, and we derive the distribution of the maximum displacement $m={\rm max}_t[x(t)]$.Comment: Contains an analysis of the extreme-value statistics not included in first versio