The COBE Diffuse Infrared Background Experiment Search for the Cosmic Infrared Background: I. Limits and Detections

The DIRBE on the COBE spacecraft was designed primarily to conduct systematic search for an isotropic CIB in ten photometric bands from 1.25 to 240 microns. The results of that search are presented here. Conservative limits on the CIB are obtained from the minimum observed brightness in all-sky maps at each wavelength, with the faintest limits in the DIRBE spectral range being at 3.5 microns (\nu I_\nu < 64 nW/m^2/sr, 95% CL) and at 240 microns (\nu I_\nu < 28 nW/m^2/sr, 95% CL). The bright foregrounds from interplanetary dust scattering and emission, stars, and interstellar dust emission are the principal impediments to the DIRBE measurements of the CIB. These foregrounds have been modeled and removed from the sky maps. Assessment of the random and systematic uncertainties in the residuals and tests for isotropy show that only the 140 and 240 microns data provide candidate detections of the CIB. The residuals and their uncertainties provide CIB upper limits more restrictive than the dark sky limits at wavelengths from 1.25 to 100 microns. No plausible solar system or Galactic source of the observed 140 and 240 microns residuals can be identified, leading to the conclusion that the CIB has been detected at levels of \nu I_\nu = 25+-7 and 14+-3 nW/m^2/sr at 140 and 240 microns respectively. The integrated energy from 140 to 240 microns, 10.3 nW/m^2/sr, is about twice the integrated optical light from the galaxies in the Hubble Deep Field, suggesting that star formation might have been heavily enshrouded by dust at high redshift. The detections and upper limits reported here provide new constraints on models of the history of energy-releasing processes and dust production since the decoupling of the cosmic microwave background from matter.Comment: 26 pages and 5 figures, accepted for publication in the Astrophyical Journa

Nuclear fission: The "onset of dissipation" from a microscopic point of view

Semi-analytical expressions are suggested for the temperature dependence of those combinations of transport coefficients which govern the fission process. This is based on experience with numerical calculations within the linear response approach and the locally harmonic approximation. A reduced version of the latter is seen to comply with Kramers' simplified picture of fission. It is argued that for variable inertia his formula has to be generalized, as already required by the need that for overdamped motion the inertia must not appear at all. This situation may already occur above T=2 MeV, where the rate is determined by the Smoluchowski equation. Consequently, comparison with experimental results do not give information on the effective damping rate, as often claimed, but on a special combination of local stiffnesses and the friction coefficient calculated at the barrier.Comment: 31 pages, LaTex, 9 postscript figures; final, more concise version, accepted for publication in PRC, with new arguments about the T-dependence of the inertia; e-mail: [email protected]

Hormonal Signal Amplification Mediates Environmental Conditions during Development and Controls an Irreversible Commitment to Adulthood

Many animals can choose between different developmental fates to maximize fitness. Despite the complexity of environmental cues and life history, different developmental fates are executed in a robust fashion. The nematode Caenorhabditis elegans serves as a powerful model to examine this phenomenon because it can adopt one of two developmental fates (adulthood or diapause) depending on environmental conditions. The steroid hormone dafachronic acid (DA) directs development to adulthood by regulating the transcriptional activity of the nuclear hormone receptor DAF-12. The known role of DA suggests that it may be the molecular mediator of environmental condition effects on the developmental fate decision, although the mechanism is yet unknown. We used a combination of physiological and molecular biology techniques to demonstrate that commitment to reproductive adult development occurs when DA levels, produced in the neuroendocrine XXX cells, exceed a threshold. Furthermore, imaging and cell ablation experiments demonstrate that the XXX cells act as a source of DA, which, upon commitment to adult development, is amplified and propagated in the epidermis in a DAF-12 dependent manner. This positive feedback loop increases DA levels and drives adult programs in the gonad and epidermis, thus conferring the irreversibility of the decision. We show that the positive feedback loop canalizes development by ensuring that sufficient amounts of DA are dispersed throughout the body and serves as a robust fate-locking mechanism to enforce an organism-wide binary decision, despite noisy and complex environmental cues. These mechanisms are not only relevant to C. elegans but may be extended to other hormonal-based decision-making mechanisms in insects and mammals

Vascular presentation of cystathionine beta-synthase deficiency in adulthood

Several recent studies describing a solely vascular presentation of cystathionine beta-synthase (CBS) deficiency in adulthood prompted us to analyze the frequency of patients manifesting with vascular complications in the Czech Republic. Between 1980 and 2009, a total of 20 Czech patients with CBS deficiency have been diagnosed yielding an incidence of 1:311,000. These patients were divided into three groups based on symptoms leading to diagnosis: those with vascular complications, with connective tissue manifestation and with neurological presentation. A vascular event such as a clinical feature leading to diagnosis of homocystinuria was present in five patients, while two of them had no other symptoms typical for CBS deficiency at the time of diagnosis. All patients with the vascular manifestation were diagnosed only during the past decade. The median age of diagnosis was 29 years in the vascular, 11.5 years in the connective tissue and 4.5 years in the neurological group. The ratio of pyridoxine responsive to nonresponsive patients was higher in the vascular (4 of 5 patients) and connective tissue groups (6 of 7 patients) than in the neurological group (2 of 8 patients). Mutation c.833T>C (p.I278T) was frequent in patients with vascular (6/10 alleles) and connective tissue presentation (8/14 alleles), while it was not present in patients with neurological involvement (0/16 alleles). During the last decade, we have observed patients with homocystinuria diagnosed solely due to vascular events; this milder form of homocystinuria usually manifests at greater ages, has a high ratio of pyridoxine responsiveness/nonresponsiveness, and the mutation c.833T>C (p.I278T) is often present

Semiclassical description of shell effects in finite fermion systems

A short survey of the semiclassical periodic orbit theory, initiated by M. Gutzwiller and generalized by many other authors, is given. Via so-called semiclassical trace formmulae, gross-shell effects in bound fermion systems can be interpreted in terms of a few periodic orbits of the corresponding classical systems. In integrable systems, these are usually the shortest members of the most degenerate families or orbits, but in some systems also less degenerate orbits can determine the gross-shell structure. Applications to nuclei, metal clusters, semiconductor nanostructures, and trapped dilute atom gases are discussed.Comment: LaTeX (revteX4) 6 pages; invited talk at Int. Conference "Finite Fermionic Systems: Nilsson Model 50 Years", Lund, Sweden, June 14-18, 200

Electrochemistry of nanozeolite-immobilized cytochrome c in aqueous and nonaqueous solutions

peer-reviewedThe electrochemical properties of cytochrome c (cyt c) immobilized on multilayer nanozeolite-modified electrodes have been examined in aqueous and nonaqueous solutions. Layers of Linde type-L zeolites were assembled on indium tin oxide (ITO) glass electrodes followed by the adsorption of cyt c, primarily via electrostatic interactions, onto modified ITO electrodes. The heme protein displayed a quasi-reversible response in aqueous solution with a redox potential of +324 mV (vs NHE), and the surface coverage (Gamma*) increased linearly for the first four layers and then gave a nearly constant value of 200 pmol cm(-2). On immersion of the modified electrodes in 95% (v/v) nonaqueous solutions, the redox potential decreased significantly, a decrease that originated from changes in both the enthalpy and entropy of reduction. On reimmersion of the modified electrode in buffer, the faradic response immediately returned to its original value. These results demonstrate that nanozeolites are potential stable supports for redox proteins and enzymes.ACCEPTEDpeer-reviewe

The histone deacetylase inhibitor Trichostatin A modulates CD4+ T cell responses

BACKGROUND: Histone deacetylase inhibitors (HDACIs) induce hyperacetylation of core histones modulating chromatin structure and affecting gene expression. These compounds are also able to induce growth arrest, cell differentiation, and apoptotic cell death of tumor cells in vitro as well as in vivo. Even though several genes modulated by HDAC inhibition have been identified, those genes clearly responsible for the biological effects of these drugs have remained elusive. We investigated the pharmacological effect of the HDACI and potential anti-cancer agent Trichostatin A (TSA) on primary T cells. METHODS: To ascertain the effect of TSA on resting and activated T cells we used a model system where an enriched cell population consisting of primary T-cells was stimulated in vitro with immobilized anti-CD3/anti-CD28 antibodies whilst exposed to pharmacological concentrations of Trichostatin A. RESULTS: We found that this drug causes a rapid decline in cytokine expression, accumulation of cells in the G(1 )phase of the cell cycle, and induces apoptotic cell death. The mitochondrial respiratory chain (MRC) plays a critical role in the apoptotic response to TSA, as dissipation of mitochondrial membrane potential and reactive oxygen species (ROS) scavengers block TSA-induced T-cell death. Treatment of T cells with TSA results in the altered expression of a subset of genes involved in T cell responses, as assessed by microarray gene expression profiling. We also observed up- as well as down-regulation of various costimulatory/adhesion molecules, such as CD28 and CD154, important for T-cell function. CONCLUSIONS: Taken together, our findings indicate that HDAC inhibitors have an immunomodulatory potential that may contribute to the potency and specificity of these antineoplastic compounds and might be useful in the treatment of autoimmune disorders

A Novel 3-Hydroxysteroid Dehydrogenase That Regulates Reproductive Development and Longevity

A multidisciplinary approach identifies novel biochemical activities involved in the synthesisof C. elegans bile acid-like steroids, which act as hormones that regulate sterol metabolism and longevity