1,573 research outputs found
Stochastic thermodynamics of hidden pumps
We show that a reversible pumping mechanism operating between two states of a
kinetic network can give rise to Poisson transitions between these two states.
An external observer, for whom the pumping mechanism is not accessible, will
observe a Markov chain satisfying local detailed balance with an emerging
effective force induced by the hidden pump. Due to the reversibility of the
pump, the actual entropy production turns out to be lower than the coarse
grained entropy production estimated from the flows and affinities of the
resulting Markov chain. Moreover, in presence of a large time scale separation
between the fast pumping dynamics and the slow network dynamics, a finite
current with zero dissipation may be produced. We make use of these general
results to build a synthetase-like kinetic scheme able to reversibly produce
high free energy molecules at a finite rate and a rotatory motor achieving
100\% efficiency at finite speed.Comment: 8 pages, 3 figures, v1: First version, v2: Major changes, new
applications and new results (pumping can always be performed reversibly), v3
version accepted in Phys. Rev.
TGF-beta(2)- and H2O2-Induced Biological Changes in Optic Nerve Head Astrocytes Are Reduced by the Antioxidant Alpha-Lipoic Acid
Background/Aims: The goal of the present study was to determine whether transforming growth factor-beta(2) (TGF-beta(2))- and oxidative stress-induced cellular changes in cultured human optic nerve head (ONH) astrocytes could be reduced by pretreatment with the antioxidant alpha-lipoic acid (LA). Methods: Cultured ONH astrocytes were treated with 1.0 ng/ml TGF-beta(2) for 24 h or 200 mu M hydrogen peroxide (H2O2) for 1 h. Lipid peroxidation was measured by a decrease in cis-pari-naric acid fluorescence. Additionally, cells were pretreated with different concentrations of LA before TGF-beta 2 or H2O2 exposure. Expressions of the heat shock protein (Hsp) alpha B-crystallin and Hsp27, the extracellular matrix (ECM) component fibronectin and the ECM-modulating protein connective tissue growth factor (CTGF) were examined with immunohistochemistry and real-time PCR analysis. Results: Both TGF-beta(2) and H2O2 increased lipid peroxidation. Treatment of astrocytes with TGF-beta(2) and H2O2 upregulated the expression of alpha B-crystallin, Hsp27, fibronectin and CTGF. Pretreatment with different concentrations of LA reduced the TGF-beta(2)- and H2O2-stimulated gene expressions. Conclusion: We showed that TGF-beta(2)- and H2O2-stimulated gene expressions could be prevented by pretreatment with the antioxidant LA in cultured human ONH astrocytes. Therefore, it is tempting to speculate that the use of antioxidants could have protective effects in glaucomatous optic neuropathy. Copyright (C) 2012 S. Karger AG, Base
The Hyperphagia Questionnaire: Insights From a Multicentric Validation Study in Individuals With Prader Willi Syndrome
Background/objectives: The present study aimed to validate the Italian version of the Hyperphagia Questionnaire (HQ), a 11-items questionnaire developed to assess hyperphagia in individuals with Prader-Willi syndrome (PWS). This is a complex neurodevelopmental disorder characterized by endocrine dysfunction, hypotonia, intellectual disability, psychiatric disorders and obesity.
Methods: Parents of 219 individuals with PWS (age range 3-54 years; Mage = 17.90; 108 Males), recruited in 12 hospitals in Italy responded to HQ during routine visits. In function of the level of analyses the sample was divided into two subgroups (<18> years) or into four age-subgroups (2.5-4.5; 4.5-8; 8-18; >18 years) corresponding to different clinical stages.
Results: Confirmatory factor analysis (CFA) confirmed the three hyperphagic subdimensions of the original structure (behavior, drive, and severity), but one item was dropped out, reducing the final version to 10 items. Using multi-group CFA, HQ showed satisfactory indexes of measurement invariance by age. Good indexes of internal consistency (Cronbach's alpha and McDonald's Omega coefficients) were found for each subdimension. The three hyperphagia subdimensions positively converged with other food-related measures: emotional overeating, food enjoyment, food responsiveness, and satiety responsiveness. A significant increase of all hyperphagic subdimensions was found across age groups. Higher hyperphagic levels were found in participants with higher body mass index. Hyperphagic drive differently increased in function of the interaction between age and underlying genetic mechanisms.
Conclusion: The Italian version of the HQ is a psychometrically valid and reliable instrument for assessing hyperphagia in individuals with PWS. This tool may prove useful to evaluate the efficacy of pharmacologic and rehabilitative treatments
Rings in the Solar System: a short review
Rings are ubiquitous around giant planets in our Solar System. They evolve
jointly with the nearby satellite system. They could form either during the
giant planet formation process or much later, as a result of large scale
dynamical instabilities either in the local satellite system, or at the
planetary scale. We review here the main characteristics of rings in our solar
system, and discuss their main evolution processes and possible origin. We also
discuss the recent discovery of rings around small bodies.Comment: Accepted for the Handbook of Exoplanet
Development of antiviral fusion inhibitors: short modified peptides derived from the transmembrane glycoprotein of feline immunodeficiency virus.
Discovery of the Onset of Rapid Accretion by a Dormant Massive Black Hole
Massive black holes are believed to reside at the centres of most galaxies.
They can be- come detectable by accretion of matter, either continuously from a
large gas reservoir or impulsively from the tidal disruption of a passing star,
and conversion of the gravitational energy of the infalling matter to light.
Continuous accretion drives Active Galactic Nuclei (AGN), which are known to be
variable but have never been observed to turn on or off. Tidal disruption of
stars by dormant massive black holes has been inferred indirectly but the on-
set of a tidal disruption event has never been observed. Here we report the
first discovery of the onset of a relativistic accretion-powered jet in the new
extragalactic transient, Swift J164449.3+573451. The behaviour of this new
source differs from both theoretical models of tidal disruption events and
observations of the jet-dominated AGN known as blazars. These differences may
stem from transient effects associated with the onset of a powerful jet. Such
an event in the massive black hole at the centre of our Milky Way galaxy could
strongly ionize the upper atmosphere of the Earth, if beamed towards us.Comment: Submitted to Nature. 4 pages, 3 figures (main paper). 26 pages, 13
figures (supplementary information
Melt Inclusion Vapour Bubbles: The Hidden Reservoir for Major and Volatile Elements
Olivine-hosted melt inclusions (MIs) provide samples of magmatic liquids and their dissolved volatiles from deep within the plumbing system. Inevitable post-entrapment modifications can lead to significant compositional changes in the glass and/or any contained bubbles. Re-heating is a common technique to reverse MI crystallisation; however, its effect on volatile contents has been assumed to be minor. We test this assumption using crystallised and glassy basaltic MIs, combined with Raman spectroscopy and 3D imaging, to investigate the changes in fluid and solid phases in the bubbles before and after re-heating. Before re-heating, the bubble contains CO2 gas and anhydrite (CaSO4) crystallites. The rapid diffusion of major and volatile elements from the melt during re-heating creates new phases within the bubble: SO2, gypsum, Fe-sulphides. Vapour bubbles hosted in naturally glassy MIs similarly contain a plethora of solid phases (carbonates, sulphates, and sulphides) that account for up to 84% of the total MI sulphur, 80% of CO2, and 14% of FeO. In both re-heated and naturally glassy MIs, bubbles sequester major and volatile elements that are components of the total magmatic budget and represent a “loss” from the glass. Analyses of the glass alone significantly underestimates the original magma composition and storage parameters
Missense mutations in the ABVB6 transporter cause dominat familial pseudohyperkaliemia
Familial Pseudohyperkalemia (FP) is a dominant red cell trait characterized by increased serum [K1] inwhole blood stored at or below room temperature, without additional hematological abnormalities. Functionalgene mapping and sequencing analysis of the candidate genes within the 2q35–q36 critical intervalidentified—in 20 affected individuals among three multigenerational FP families—two novel heterozygousmissense mutations in the ABCB6 gene that cosegregated with disease phenotype. The two genomic substitutionsaltered two adjacent nucleotides within codon 375 of ABCB6, a porphyrin transporter that, inerythrocyte membranes, bears the Langereis blood group antigen system. The ABCB6 R375Q mutation didnot alter the levels of mRNA or protein, or protein localization in mature erythrocytes or erythroid precursorcells, but it is predicted to modestly alter protein structure. ABCB6 mRNA and protein levels increase duringin vitro erythroid differentiation of CD341 erythroid precursors and the erythroleukemia cell lines HELand K562. These data suggest that the two missense mutations in residue 375 of the ABCB6 polypeptidefound in affected individuals of families with chromosome 2-linked FP could contribute to the red cell K1leak characteristic of this condition
Public Narratives and the Construction of Memory Among European Muslims
This chapter draws on group and individual interviews with 735 European Muslims in 5 European countries and explores some key aspects of the politics of memory that form an inextricable component of European Muslim self-definitions, discourses and narratives deployed in the attempt to negotiate their inclusion in European societies
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