6,330 research outputs found
Gibbs entropy and irreversible thermodynamics
Recently a number of approaches has been developed to connect the microscopic
dynamics of particle systems to the macroscopic properties of systems in
nonequilibrium stationary states, via the theory of dynamical systems. This way
a direct connection between dynamics and Irreversible Thermodynamics has been
claimed to have been found. However, the main quantity used in these studies is
a (coarse-grained) Gibbs entropy, which to us does not seem suitable, in its
present form, to characterize nonequilibrium states. Various simplified models
have also been devised to give explicit examples of how the coarse-grained
approach may succeed in giving a full description of the Irreversible
Thermodynamics. We analyze some of these models pointing out a number of
difficulties which, in our opinion, need to be overcome in order to establish a
physically relevant connection between these models and Irreversible
Thermodynamics.Comment: 19 pages, 4 eps figures, LaTeX2
Parent population of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies
Flat-spectrum radio-loud Narrow-Line Seyfert 1 galaxies (NLS1s) are a
recently discovered class of -ray emitting Active Galactic Nuclei
(AGN), that exhibit some blazar-like properties which are explained with the
presence of a relativistic jet viewed at small angles. When blazars are
observed at larger angles they appear as radio-galaxies, and we expect to
observe an analogue parent population for beamed NLS1s. However, the number of
known NLS1s with the jet viewed at large angles is not enough. Therefore, we
tried to understand the origin of this deficit. Current hypotheses about the
nature of parent sources are steep-spectrum radio-loud NLS1s, radio-quiet NLS1s
and disk-hosted radio-galaxies. To test these hypotheses we built three samples
of candidate sources plus a control sample, and calculated their black hole
mass and Eddington ratio using their optical spectra. We then performed a
Kolmogorov-Smirnov statistical test to investigate the compatibility of our
different samples with a beamed population. Our results indicate that, when the
inclination angle increases, a beamed source appears as a steep-spectrum
radio-loud NLS1, or possibly even as a disk-hosted radio-galaxy with low black
hole mass and high Eddington ratio. Further investigations, involving larger
complete samples and observations at radio frequency, are needed to understand
the incidence of disk-hosted radio-galaxies in the parent population, and to
assess whether radio-quiet NLS1s can play a role, as well.Comment: 12 pages, 6 figures, accepted for publication by Astronomy and
Astrophysic
Compact steep-spectrum sources as the parent population of flat-spectrum radio-loud NLS1s
Narrow-line Seyfert 1 galaxies (NLS1s) are an interesting subclass of active
galactic nuclei (AGN), which tipically does not exhibit any strong radio
emission. Seven percent of them, though, are radio-loud and often show a flat
radio-spectrum (F-NLS1s). This, along to the detection of -ray emission
coming from them, is usually interpreted as a sign of a relativistic beamed jet
oriented along the line of sight. An important aspect of these AGN that must be
understood is the nature of their parent population, in other words how do they
appear when observed under different angles. In the recent literature it has
been proposed that a specific class of radio-galaxies, compact-steep sources
(CSS) classified as high excitation radio galaxies (HERG), can represent the
parent population of F-NLS1s. To test this hypothesis in a quantitative way,in
this paper we analyzed the only two statistically complete samples of CSS/HERGs
and F-NLS1s available in the literature. We derived the black hole mass and
Eddington ratio distributions, and we built for the first time the radio
luminosity function of F-NLS1s. Finally, we applied a relativistic beaming
model to the luminosity function of CSS/HERGs, and compared the result with the
observed function of F-NLS1s. We found that compact steep-spectrum sources are
valid parent candidates and that F-NLS1s, when observed with a different
inclination, might actually appear as CSS/HERGs.Comment: 9 pages, 5 figures, 4 tables. Accepted for publication in Astronomy &
Astrophysic
A cohort study of the associations between udder conformation, milk somatic cell count, and lamb weight in suckler ewes
A cohort study of 67 suckler ewes from 1 farm was carried out from January to May 2010 to investigate associations between udder conformation, udder half milk somatic cell count (SCC), and lamb weight. Ewes and lambs were observed at lambing. Ewe health and teat condition and lamb health and weight were recorded on 4 to 5 further occasions at 14-d intervals. At each observation, a milk sample was collected from each udder half for somatic cell counting. Two weeks after lambing, ewe udder conformation and teat placement were scored. Low lamb weight was associated with ewe SCC >400,000 cells/mL (−0.73kg), a new teat lesion 14 d previously (−0.91kg), suboptimal teat position (−1.38kg), rearing in a multiple litter (−1.45kg), presence of diarrhea at the examination (−1.19kg), and rearing by a 9-yr-old ewe compared with a 6-yr-old ewe (−2.36kg). High lamb weight was associated with increasing lamb age (0.21kg/d), increasing birth weight (1.65kg/kg at birth), and increasing number of days the ewe was given supplementary feed before lambing (0.06kg/d). High udder half SCC was associated with pendulous udders (9.6% increase in SCC/cm of drop) and greater total cross-sectional area of the teats (7.2% increase of SCC/cm2). Low SCC were associated with a heavier mean litter weight (6.7% decrease in SCC/kg). Linear, quadratic, and cubic terms for days in lactation were also significant. We conclude that poor udder and teat conformation are associated with high levels of intramammary infection, as indicated by increased SCC and that both physical attributes of the udder and SCC are linked to lamb growth, suggesting that selection of suckler ewes with better udder and teat conformation would reduce intramammary infection and increase lamb growth rate
Disentangling PTEN-cooperating tumor suppressor gene networks in cancer.
We have recently performed a whole-body, genome-wide screen in mice using a single-copy inactivating transposon for the identification of Pten (phosphatase and tensin homolog)-cooperating tumor suppressor genes (TSGs). We identified known and putative TSGs in multiple cancer types and validated the functional and clinical relevance of several promising candidates for human prostate cancer
Ada User Guide for LEGO MINDSTORMS NXT
The purpose of this guide is to introduce the robotics kit LEGO MINDSTORMS NXT to the Ada community. All the steps required to complete a working Ada application running under the LEGO MINDSTORMS NXT are covered.
The effects of uterine artery embolisation and surgical treatment on ovarian function in women with uterine fibroids
Objective The aim of this study was to evaluate and compare both ovarian function and menstrual characteristics following uterine artery embolisation (UAE) and surgery. Design Subgroup of women from a randomised controlled trial. Setting Gynaecology and radiology units in Scotland, UK. Population Ninety-six women from the randomised controlled trial comparing embolisation with surgery as a treatment for fibroids (REST), which recruited 157 patients (106 UAE; 51 surgery). Methods Seventy-three women undergoing UAE and 23 women undergoing surgery (with ovarian conservation) had serum follicle-stimulating hormone (FSH) measurements taken on day 3 of the menstrual cycle prior to treatment, and at 6 and 12 months post-treatment. Data on menstrual cycle characteristics was also collected. Main outcome measures Ovarian failure, as defined by an FSH level of > 40 iu/l, and change in duration of menses and length of menstrual cycle. Results There was no significant difference in the rate of ovarian failure at 12 months between UAE (11%) and surgical patients (18%) (P = 0.44). This finding was not influenced by age. The mean duration of menstrual flow decreased significantly, from baseline to 12 months, by 1.7 days (SD 3.8), (95% CI 0.8-2.6). There was no statistically significant change in mean cycle length at 12 months (0.7 days [SD 4.9]; 95% CI [-0.5, 1.9]). Conclusions There is no evidence for UAE accelerating a deterioration in ovarian function at 1 year, when compared with surgery. UAE is associated with a decrease in the duration of menstrual flow at 1 yea
Morphological characterisation of unstained and intact tissue microarchitecture by x-ray computed micro- and nano-tomography
Characterisation and quantification of tissue structures is limited by sectioning-induced artefacts and by the difficulties of visualising and segmenting 3D volumes. Here we demonstrate that, even in the absence of X-ray contrast agents, X-ray computed microtomography (microCT) and nanotomography (nanoCT) can circumvent these problems by rapidly resolving compositionally discrete 3D tissue regions (such as the collagen-rich adventitia and elastin-rich lamellae in intact rat arteries) which in turn can be segmented due to their different X-ray opacities and morphologies. We then establish, using X-ray tomograms of both unpressurised and pressurised arteries that intra-luminal pressure not only increases lumen cross-sectional area and straightens medial elastic lamellae but also induces profound remodelling of the adventitial layer. Finally we apply microCT to another human organ (skin) to visualise the cell-rich epidermis and extracellular matrix-rich dermis and to show that conventional histological and immunohistochemical staining protocols are compatible with prior X-ray exposure. As a consequence we suggest that microCT could be combined with optical microscopy to characterise the 3D structure and composition of archival paraffin embedded biological materials and of mechanically stressed dynamic tissues such as the heart, lungs and tendons
Repeated-sprint sequences during female soccer matches using fixed and individual speed thresholds.
The main objective of this study was to characterize the occurrence of single sprint and repeated-sprint sequences (RSS) during elite female soccer matches, using fixed (20 kmh) and individually based speed thresholds (>90% of the mean speed from a 20 m sprint test). Eleven elite female soccer players from the same team participated in the study. All players performed a 20 m linear sprint test, and were assessed in up to 10 official matches using Global Positioning System (GPS) technology. Magnitude-based inferences were used to test for meaningful differences. Results revealed that irrespective of adopting fixed or individual speed thresholds, female players produced only a few RSS during matches (2.3 ± 2.4 sequences using the fixed threshold and 3.3 ± 3.0 sequences using the individually based threshold), with most sequences composing of just two sprints. Additionally, central defenders performed fewer sprints (10.2 ± 4.1) than other positions (full backs: 28.1 ± 5.5; midfielders: 21.9 ± 10.5; forwards: 31.9 ± 11.1; with likely to almost certainly differences associated with effect sizes ranging from 1.65 to 2.72) and sprinting ability declined in the second half. The data do not support the notion that RSS occurs frequently during soccer matches in female players, irrespective of using fixed or individual speed thresholds to define sprint occurrence. However, repeated sprint ability development cannot be ruled out from soccer training programs due to its association with match-related performance
A platform for real-time control education with LEGO MINDSTORMS.
A set of software development tools for building real-time control systems on a simple robotics platform is described in the paper. The tools are being used in a real-time systems course as a basis for student projects. The development platform is a low-cost PC running GNU/Linux, and the target system is LEGO MINDSTORMS NXT, thus keeping the cost of the laboratory low. Real-time control software is developed using a mixed paradigm. Functional code for control algorithms is automatically generated in C from Simulink models. This code is then integrated into a concurrent, real-time software architecture based on a set of components written in Ada. This approach enables the students to take advantage of the high-level, model-oriented features that Simulink oers for designing control algorithms, and the comprehensive support for concurrency and real-time constructs provided by Ada
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