Cluster algebras in algebraic Lie theory

We survey some recent constructions of cluster algebra structures on coordinate rings of unipotent subgroups and unipotent cells of Kac-Moody groups. We also review a quantized version of these results.Comment: Invited survey; to appear in Transformation Group

Fractional smoothness and applications in finance

This overview article concerns the notion of fractional smoothness of random variables of the form $g(X_T)$, where $X=(X_t)_{t\in [0,T]}$ is a certain diffusion process. We review the connection to the real interpolation theory, give examples and applications of this concept. The applications in stochastic finance mainly concern the analysis of discrete time hedging errors. We close the review by indicating some further developments.Comment: Chapter of AMAMEF book. 20 pages

Charmonium Suppression with cc~ Dissociation by Strings

We study the production of cc~ pairs in nuclear reactions at SPS energies within the covariant transport approach HSD. The production of cc~ is treated perturbatively employing experimental cross sections while the interactions of cc~ pairs with baryons are included by conventional cascade-type two-body collisions. Adopting 6 mb for the cc~-baryon cross sections the data on J/\Psi suppression in p+A reactions are reproduced in line with calculations based on the Glauber model. Additionally the dissociation of the cc~ pairs by strings is included in a purely geometrical way. We find good agreement with experimental data from the NA38 and NA50 collaboration with an estimate for the string radius of ~0.2-0.3 fm.Comment: 9 pages (LaTeX), 5 PS figure

How Abundant is Pedogenic Magnetite? Abundance and Grain Size Estimates for Loessic Soils Based on Rock Magnetic Analyses

The upper soil horizons of many modern and ancient soils are enriched in fine-grained pedogenic ferrimagnetic minerals. We use three grain-size- and concentration-dependent proxies (anhysteretic remanent magnetization/isothermal remanent magnetization ratios, coercivity spectra derived from alternating field demagnetization of saturation isothermal remanent magnetization and hysteresis properties) to quantify the abundance and grain size of the pedogenic magnetic component. Our analyses of modern loessic soils from the midwestern United States show that relatively small additions (2–10 vol % of the total ferrimagnetic component) of fine-grained (coarse superparamagnetic to fine pseudosingle domain) magnetite or maghemite are sufficient to explain the changes in concentration and grain-size-dependent properties observed in the upper soil horizons. Furthermore, the pedogenic components of all studied sites display a narrow range of magnetic properties, which argues for a common origin of these particles over a wide range of climatic conditions

Actin assembly ruptures the nuclear envelope by prying the lamina away from nuclear pores and nuclear membranes in starfish oocytes.

The nucleus of oocytes (germinal vesicle) is unusually large and its nuclear envelope (NE) is densely packed with nuclear pore complexes (NPCs) stockpiled for embryonic development. We showed that breakdown of this specialized NE is mediated by an Arp2/3-nucleated F-actin 'shell' in starfish oocytes, in contrast to microtubule-driven tearing in mammalian fibroblasts. Here, we address the mechanism of F-actin-driven NE rupture by correlated live-cell, super-resolution and electron microscopy. We show that actin is nucleated within the lamina sprouting filopodia-like spikes towards the nuclear membranes. These F-actin spikes protrude pore-free nuclear membranes, whereas the adjoining membrane stretches accumulate NPCs associated with the still-intact lamina. Packed NPCs sort into a distinct membrane network, while breaks appear in ER-like, pore-free regions. Thereby, we reveal a new function for actin-mediated membrane shaping in nuclear rupture that is likely to have implications in other contexts such as nuclear rupture observed in cancer cells

Can Galactic Cosmic Rays Account for Solar 6Li Without Overproducing Gamma Rays?

Cosmic-ray interactions with interstellar gas produces both 6Li, which accumulates in the interstellar medium (ISM), and $\pi^0$ mesons, which decay to gamma-rays which propagate throughout the cosmos. Local 6Li abundances and extragalactic gamma-rays thus have a common origin which tightly links them. We exploit this connection to use gamma-ray observations to infer the contribution to 6Li nucleosynthesis by standard Galactic cosmic-ray (GCR) interactions with the ISM. Our calculation uses a carefully propagated cosmic-ray spectrum and accounts for 6Li production from both fusion reactions ($\alpha \alpha \to ^6Li$) as well as from spallation channels ({p,\alpha+CNO \to ^6Li). We find that although extreme assumptions yield a consistent picture, more realistic ones indicate that solar 6Li cannot be produced by standard GCRs alone without overproducing the hadronic gamma rays. Implications for the primordial 6Li production by decaying dark matter and cosmic rays from cosmological structure formation are discussed. Upcoming gamma-ray observations by GLAST will be crucial for determining the resolution of this problem.Comment: 4 pages, 1 figure To be published in ApJ

B704: Costs and Returns on Maine Apple Farms

The purpose of this study was to collect data relative to the costs of growing, harvesting, storing, and packing apples in Maine, to analyze the factors affecting costs and returns, and to provide Maine apple producers with current information for adjusting farm resources to achieve optimum efficiency in production under rapidly changing economic conditions. This study was undertaken to determine the profitability of Maine apple farms, and to determine the current size and scope of the Maine apple industry. The results and implications of this study should be useful to all concerned with the apple industry in Maine and New England.https://digitalcommons.library.umaine.edu/aes_bulletin/1133/thumbnail.jp

Big-Bang Nucleosynthesis with Unstable Gravitino and Upper Bound on the Reheating Temperature

We study the effects of the unstable gravitino on the big-bang nucleosynthesis. If the gravitino mass is smaller than \sim 10 TeV, primordial gravitinos produced after the inflation are likely to decay after the big-bang nucleosynthesis starts, and the light element abundances may be significantly affected by the hadro- and photo-dissociation processes as well as by the p n conversion process. We calculate the light element abundances and derived upper bound on the reheating temperature after the inflation. In our analysis, we calculate the decay parameters of the gravitino (i.e., lifetime and branching ratios) in detail. In addition, we performed a systematic study of the hadron spectrum produced by the gravitino decay, taking account of all the hadrons produced by the decay products of the gravitino (including the daughter superparticles). We discuss the model-dependence of the upper bound on the reheating temperature.Comment: 32 pages, 11 figure

Grass fires—an unlikely process to explain the magnetic properties of prairie soils

It has been proposed that grass fires affect the magnetic properties of soils by combining generally reducing soil conditions with elevated temperatures. To explore this supposition, we analysed surface and subsurface samples from loessic soils and compared their differences in magnetic properties as a function of fire intensity. Fire intensity was established based on types of burnt vegetation, which ranged from low-intensity fires in short-grass areas to high-intensity fires in tall-grass and forested areas. We measured low-field magnetic susceptibility (χ), a common proxy for the abundance of magnetic minerals, frequency-dependent susceptibility (χFD), a proxy for the presence of ultrafine-grained superparamagnetic minerals, and susceptibility of anhysteretic remanent magnetization (χARM), a magnetic parameter highly dependent on the presence of fine, single-domain magnetic particles. Although intense fires led to an increase in frequency-dependent susceptibility and low-field magnetic susceptibility, moderately intense fires did not produce significant changes in magnetic properties. Observed magnetic changes are limited to sites that were very heavily burnt in forest areas. Grass fires are therefore an unlikely mechanism to explain a measurable component of the magnetic enhancement in prairie soils