413 research outputs found
Probing the cosmographic parameters to distinguish between dark energy and modified gravity models
In this paper we investigate the deceleration, jerk and snap parameters to
distinguish between the dark energy and modified gravity models by using high
redshift gamma-ray bursts (GRBs) and supernovae (SNe). We first derive the
expressions of deceleration, jerk and snap parameters in dark energy and
modified gravity models. In order to constrain the cosmographic parameters, we
calibrate the GRB luminosity relations without assuming any cosmological models
using SNe Ia. Then we constrain the models (including dark energy and modified
gravity models) parameters using type Ia supernovae and gamma-ray bursts.
Finally we calculate the cosmographic parameters. GRBs can extend the redshift
- distance relation up to high redshifts, because they can be detected to high
redshifts.We find that the statefinder pair (r,s) could not be used to
distinguish between some dark energy and modified gravity models, but these
models could be differentiated by the snap parameter. Using the
model-independent constraints on cosmographic parameters, we conclude that the
\LambdaCDM model is consistent with the current data.Comment: 9 pages, 7 figures, 1 table, published in Astronomy & Astrophysics,
two references adde
Gauge Unification in Highly Anisotropic String Compactifications
It is well-known that heterotic string compactifications have, in spite of
their conceptual simplicity and aesthetic appeal, a serious problem with
precision gauge coupling unification in the perturbative regime of string
theory. Using both a duality-based and a field-theoretic definition of the
boundary of the perturbative regime, we reevaluate the situation in a
quantitative manner. We conclude that the simplest and most promising
situations are those where some of the compactification radii are exceptionally
large, corresponding to highly anisotropic orbifold models. Thus, one is led to
consider constructions which are known to the effective field-theorist as
higher-dimensional or orbifold grand unified theories (orbifold GUTs). In
particular, if the discrete symmetry used to break the GUT group acts freely, a
non-local breaking in the larger compact dimensions can be realized, leading to
a precise gauge coupling unification as expected on the basis of the MSSM
particle spectrum. Furthermore, a somewhat more model dependent but
nevertheless very promising scenario arises if the GUT breaking is restricted
to certain singular points within the manifold spanned by the larger
compactification radii.Comment: 34 pages, 4 figures, more references adde
Oink: an Implementation and Evaluation of Modern Parity Game Solvers
Parity games have important practical applications in formal verification and
synthesis, especially to solve the model-checking problem of the modal
mu-calculus. They are also interesting from the theory perspective, as they are
widely believed to admit a polynomial solution, but so far no such algorithm is
known. In recent years, a number of new algorithms and improvements to existing
algorithms have been proposed. We implement a new and easy to extend tool Oink,
which is a high-performance implementation of modern parity game algorithms. We
further present a comprehensive empirical evaluation of modern parity game
algorithms and solvers, both on real world benchmarks and randomly generated
games. Our experiments show that our new tool Oink outperforms the current
state-of-the-art.Comment: Accepted at TACAS 201
Persistent kallikrein 5 activation induces atopic dermatitis-like skin architecture independent of PAR2 activity.
BACKGROUND: Upregulation of kallikreins (KLKs) including KLK5 has been reported in atopic dermatitis (AD). KLK5 has biological functions that include degrading desmosomal proteins and inducing proinflammatory cytokine secretion through protease-activated receptor 2 (PAR2). However, due to the complex interactions between various cells in AD inflamed skin, it is difficult to dissect the precise and multiple roles of upregulated KLK5 in AD skin. OBJECTIVE: We investigated the effect of upregulated KLK5 on the expression of epidermal-related proteins and cytokines in keratinocytes and on skin architecture. METHODS: Lesional and nonlesional AD skin biopsies were collected for analysis of morphology and protein expression. The relationship between KLK5 and barrier-related molecules was investigated using an ex vivo dermatitis skin model with transient KLK5 expression and a cell model with persistent KLK5 expression. The influence of upregulated KLK5 on epidermal morphology was investigated using an in vivo skin graft model. RESULTS: Upregulation of KLK5 and abnormal expression of desmoglein 1 (DSG1) and filaggrin, but not PAR2 were identified in AD skin. PAR2 was increased in response to transient upregulation of KLK5, whereas persistently upregulated KLK5 did not show this effect. Persistently upregulated KLK5 degraded DSG1 and stimulated secretion of IL-8, IL-10, and thymic stromal lymphopoietin independent of PAR2 activity. With control of higher KLK5 activity by the inhibitor sunflower trypsin inhibitor G, restoration of DSG1 expression and a reduction in AD-related cytokine IL-8, thymic stromal lymphopoietin, and IL-10 secretion were observed. Furthermore, persistently elevated KLK5 could induce AD-like skin architecture in an in vivo skin graft model. CONCLUSIONS: Persistently upregulated KLK5 resulted in AD-like skin architecture and secretion of AD-related cytokines from keratinocytes in a PAR2 independent manner. Inhibition of KLK5-mediated effects may offer potential as a therapeutic approach in AD.Supported by Sparks and the Livingstone Fund (Great Ormond Street Hospital Children's Charity) and Biotechnology and Biological Sciences Research Council
Is there just one dyslexic reader? Evidence for the existence of distinct dyslexic sub-groups.
Purpose of Review. It is generally agreed that there are individual differences in the severity of the reading deficit in dyslexia. The purpose of this review is to discuss whether recent research strengthens claims that there are also qualitative differences in the type of reading impairment that individual dyslexic children experience.
Recent Findings. Recent research suggests that surface dyslexia exists in larger numbers than has previously been assumed and that different subtypes of surface dyslexia exist in English as well as in Hebrew. Bilinguals with surface dyslexia in English also show the hallmarks of surface dyslexia when reading a more transparent orthography. The developmental reading impairments that have been observed in children with phonological dyslexia and in children with letter position dyslexia can also be found in several different orthographies and are quite distinct from those seen in surface dyslexia.
Summary. Surface dyslexia, phonological dyslexia and letter position dyslexia represent qualitatively different types of developmental reading impairments and can all be seen in both opaque and more transparent alphabetic orthographies
Developmental surface and phonological dyslexia in both Greek and English.
The hallmark of developmental surface dyslexia in English and French is inaccurate reading of words with atypical spelling-sound correspondences. According to Douklias, Masterson and Hanley (2009), surface dyslexia can also be observed in Greek (a transparent orthography for reading that does not contain words of this kind). Their findings suggested that surface dyslexia in Greek can be characterized by slow reading of familiar words, and by inaccurate spelling of words with atypical sound-spelling correspondences (Greek is less transparent for spelling than for reading). In this study, we report seven adult cases whose slow reading and impaired spelling accuracy satisfied these criteria for Greek surface dyslexia. When asked to read words with atypical grapheme-phoneme correspondences in English (their second language), their accuracy was severely impaired. A co-occurrence was also observed between impaired spelling of words with atypical phoneme-grapheme correspondences in English and Greek. These co-occurrences provide strong evidence that surface dyslexia genuinely exists in Greek and that slow reading of real words in Greek reflects the same underlying impairment as that which produces inaccurate reading of atypical words in English. Two further individuals were observed with impaired reading and spelling of nonwords in both languages, consistent with developmental phonological dyslexia. Neither of the phonological dyslexics read words slowly. In terms of computational models of reading aloud, these findings suggest that slow reading by dyslexics in transparent orthographies is the consequence of a developmental impairment of the lexical (Coltheart, Rastle, Perry, Langdon, & Zeigler, 2001; Perry, Ziegler, & Zorzi, 2010) or semantic reading route (Plaut, McClelland, Seidenberg, & Patterson, 1996). This outcome provides evidence that the neurophysiological substrate(s) that support the lexical/semantic and the phonological pathways that are involved in reading and spelling are the same in both Greek and English
Angular diameter estimation of interferometric calibrators - Example of lambda Gruis, calibrator for VLTI-AMBER
Context. Accurate long-baseline interferometric measurements require careful
calibration with reference stars. Small calibrators with high angular diameter
accuracy ensure the true visibility uncertainty to be dominated by the
measurement errors. Aims. We review some indirect methods for estimating
angular diameter, using various types of input data. Each diameter estimate,
obtained for the test-case calibrator star lambda Gru, is compared with the
value 2.71 mas found in the Bord\'e calibrator catalogue published in 2002.
Methods. Angular size estimations from spectral type, spectral index, in-band
magnitude, broadband photometry, and spectrophotometry give close estimates of
the angular diameter, with slightly variable uncertainties. Fits on photometry
and spectrophotometry need physical atmosphere models with "plausible" stellar
parameters. Angular diameter uncertainties were estimated by means of residual
bootstrapping confidence intervals. All numerical results and graphical outputs
presented in this paper were obtained using the routines developed under
PV-WAVE, which compose the modular software suite SPIDAST, created to calibrate
and interprete spectroscopic and interferometric measurements, particularly
those obtained with VLTI-AMBER. Results. The final angular diameter estimate
2.70 mas of lambda Gru, with 68% confidence interval 2.65-2.81 mas, is obtained
by fit of the MARCS model on the ISO-SWS 2.38-27.5 mum spectrum, with the
stellar parameters T_eff = 4 250 K, log(g) = 2.0, z = 0.0 dex, M = 1.0 M_sun,
and xi_turb = 2.0 km/s.Comment: to be published in A&A, Main Journal (Astronomical Instrumentation
A review of elliptical and disc galaxy structure, and modern scaling laws
A century ago, in 1911 and 1913, Plummer and then Reynolds introduced their
models to describe the radial distribution of stars in `nebulae'. This article
reviews the progress since then, providing both an historical perspective and a
contemporary review of the stellar structure of bulges, discs and elliptical
galaxies. The quantification of galaxy nuclei, such as central mass deficits
and excess nuclear light, plus the structure of dark matter halos and cD galaxy
envelopes, are discussed. Issues pertaining to spiral galaxies including dust,
bulge-to-disc ratios, bulgeless galaxies, bars and the identification of
pseudobulges are also reviewed. An array of modern scaling relations involving
sizes, luminosities, surface brightnesses and stellar concentrations are
presented, many of which are shown to be curved. These 'redshift zero'
relations not only quantify the behavior and nature of galaxies in the Universe
today, but are the modern benchmark for evolutionary studies of galaxies,
whether based on observations, N-body-simulations or semi-analytical modelling.
For example, it is shown that some of the recently discovered compact
elliptical galaxies at 1.5 < z < 2.5 may be the bulges of modern disc galaxies.Comment: Condensed version (due to Contract) of an invited review article to
appear in "Planets, Stars and Stellar
Systems"(www.springer.com/astronomy/book/978-90-481-8818-5). 500+ references
incl. many somewhat forgotten, pioneer papers. Original submission to
Springer: 07-June-201
HMGA1 Induces Intestinal Polyposis in Transgenic Mice and Drives Tumor Progression and Stem Cell Properties in Colon Cancer Cells
Although metastatic colon cancer is a leading cause of cancer death worldwide, the molecular mechanisms that enable colon cancer cells to metastasize remain unclear. Emerging evidence suggests that metastatic cells develop by usurping transcriptional networks from embryonic stem (ES) cells to facilitate an epithelial-mesenchymal transition (EMT), invasion, and metastatic progression. Previous studies identified HMGA1 as a key transcription factor enriched in ES cells, colon cancer, and other aggressive tumors, although its role in these settings is poorly understood.To determine how HMGA1 functions in metastatic colon cancer, we manipulated HMGA1 expression in transgenic mice and colon cancer cells. We discovered that HMGA1 drives proliferative changes, aberrant crypt formation, and intestinal polyposis in transgenic mice. In colon cancer cell lines from poorly differentiated, metastatic tumors, knock-down of HMGA1 blocks anchorage-independent cell growth, migration, invasion, xenograft tumorigenesis and three-dimensional colonosphere formation. Inhibiting HMGA1 expression blocks tumorigenesis at limiting dilutions, consistent with depletion of tumor-initiator cells in the knock-down cells. Knock-down of HMGA1 also inhibits metastatic progression to the liver in vivo. In metastatic colon cancer cells, HMGA1 induces expression of Twist1, a gene involved in embryogenesis, EMT, and tumor progression, while HMGA1 represses E-cadherin, a gene that is down-regulated during EMT and metastatic progression. In addition, HMGA1 is among the most enriched genes in colon cancer compared to normal mucosa.Our findings demonstrate for the first time that HMGA1 drives proliferative changes and polyp formation in the intestines of transgenic mice and induces metastatic progression and stem-like properties in colon cancer cells. These findings indicate that HMGA1 is a key regulator, both in metastatic progression and in the maintenance of a stem-like state. Our results also suggest that HMGA1 or downstream pathways could be rational therapeutic targets in metastatic, poorly differentiated colon cancer
Eurocity London: a qualitative comparison of graduate migration from Germany, Italy and Latvia
This paper compares the motivations and characteristics of the recent migration to London of young-adult graduates from Germany, Italy and Latvia. Conceptually the paper links three domains: the theory of coreâperiphery structures within Europe; the notion of London as both a global city and a âEurocityâ; and the trope of âcrisisâ. The dataset analysed consists of 95 in-depth biographical interviews and the paperâs main objective is to tease out the narrative similarities and differences between the three groups interviewed. Each of the three nationalities represents a different geo-economic positioning within Europe. German graduates move from one economically prosperous country to another; they traverse shallow economic and cultural boundaries. Italian graduates migrate from a relatively peripheral Southern European country where, especially in Southern Italy, employment and career prospects have long been difficult, and have become more so in the wake of the financial crisis. They find employment opportunities in London which are unavailable to them in Italy. Latvian graduates are from a different European periphery, the Eastern one, post-socialist and post-Soviet. Like the Italians, their moves are economically driven whereas, for the Germans, migration is more related to lifestyle and life-stage. For all three groups, the chance to live in a large, multicultural, cosmopolitan city is a great attraction. And for all groups, thoughts about the future are marked by uncertainty and ambiguity
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