77 research outputs found
Analysis of Deformation Data at Parkfield, California: Detection of a Long-Term Strain Transient
Analysis of more than a decade of high-quality data, particularly those from the two-color electronic distance meter (EDM), in the Parkfield, California, area reveals a significant transient in slip rate along the San Andreas Fault. This transient consists of an increase in fault slip rate of 3.3 ± 0.9 mm/yr during 1993.0 to 1998.0. The most reliable fault creep instruments show a comparable increase in slip rate, suggesting that the deformation is localized to the fault which breaks the surface. There was also an increase in precipitation around 1993. It is unlikely, however, that this anomaly is due directly to hydrology, as its spatial distribution is what would be expected for increased slip on the San Andreas Fault. The increase in slip rate corresponds temporally to a dramatic increase in seismicity, including the four largest earthquakes in the period 1984-1999 that occurred along a 6-km segment of the fault just to the north of the EDM network. There was also a previously reported anomaly in borehole shear strain [Gwyther et al., 1996] that closely corresponds temporally to the transient in EDM data. Solely on the basis of EDM data the transient can be modeled as a slip event on a 10-km-long segment of the fault. The calculated shear strains from this model, however, are not consistent with the observed ones. A compatible model can be found if there is increased aseismic slip to the northwest in conjunction with the four earthquakes. Support for this northwestern slip is provided by a recent study of slip rate based on microearthquake activity. We speculate that this northwestern event served to load the fault to the southeast, with the stress being partially released by the observed slip
Instantons and unitarity in quantum cosmology with fixed four-volume
We find a number of complex solutions of the Einstein equations in the
so-called unimodular version of general relativity, and we interpret them as
saddle points yielding estimates of a gravitational path integral over a space
of almost everywhere Lorentzian metrics on a spacetime manifold with topology
of the "no-boundary" type. In this setting, the compatibility of the
no-boundary initial condition with the definability of the quantum measure
reduces reduces to the normalizability and unitary evolution of the no-boundary
wave function \psi. We consider the spacetime topologies R^4 and RP^4 # R^4
within a Taub minisuperspace model with spatial topology S^3, and the spacetime
topology R^2 x T^2 within a Bianchi type I minisuperspace model with spatial
topology T^3. In each case there exists exactly one complex saddle point (or
combination of saddle points) that yields a wave function compatible with
normalizability and unitary evolution. The existence of such saddle points
tends to bear out the suggestion that the unimodular theory is less divergent
than traditional Einstein gravity. In the Bianchi type I case, the
distinguished complex solution is approximately real and Lorentzian at late
times, and appears to describe an explosive expansion from zero size at T=0.
(In the Taub cases, in contrast, the only complex solution with nearly
Lorentzian late-time behavior yields a wave function that is normalizable but
evolves nonunitarily, with the total probability increasing exponentially in
the unimodular "time" in a manner that suggests a continuous creation of new
universes at zero volume.) The issue of the stability of these results upon the
inclusion of more degrees of freedom is raised.Comment: 32 pages, REVTeX v3.1 with amsfonts. (v2: minor typos etc corrected.
Multiwaveband Observations of Quasars with Flat Radio Spectra and Strong Millimeter Emission
We present multiwaveband observations of a well selected sample of 28 quasars
and two radio galaxies with flat radio spectra and strong millimeter wave
emission (referred to here as FSRQ's). The observations include multifrequency
VLBI measurements, X-ray observations with ROSAT and submillimeter observations
with the JCMT. Particularly interesting among many findings is a correlation
between the X-ray to millimeter spectral index and fraction of flux density
contained in the VLBI core. This tendency toward higher X-ray fluxes from
sources with stronger jet emission implies that the knots in the jet are the
prominent source of X-rays.Comment: 38 pages, 17 figures, 12 tables, accepted for publication in Ap J
Suppl, May 199
Accelerated cosmological expansion due to a scalar field whose potential has a positive lower bound
In many cases a nonlinear scalar field with potential can lead to
accelerated expansion in cosmological models. This paper contains mathematical
results on this subject for homogeneous spacetimes. It is shown that, under the
assumption that has a strictly positive minimum, Wald's theorem on
spacetimes with positive cosmological constant can be generalized to a wide
class of potentials. In some cases detailed information on late-time
asymptotics is obtained. Results on the behaviour in the past time direction
are also presented.Comment: 16 page
Strain field analysis on Montserrat (W.I.) as tool for assessing permeable flow paths in the magmatic system of Soufrière Hills Volcano
Strain dilatometers have been operated on the volcanic island of Montserrat (West Indies) for more than a decade and have proven to be a powerful technique to approach short-term dynamics in the deformational field in response to pressure changes in the magmatic system of the andesitic dome-building Soufrière Hills Volcano (SHV). We here demonstrate that magmatic activity in each of the different segments of the SHV magmatic system (shallow dyke-conduit, upper and lower magma chambers) generates a characteristic strain pattern that allows the identification of operating sources in the plumbing system based on a simple scheme of amplitude ratios. We use this method to evaluate strain data from selected Vulcanian explosions and gas emission events that occurred at SHV between 2003 and 2012. Our results show that the events were initiated by a short phase of contraction of either one or both magma chambers and a simultaneous inflation of the shallow feeder system. The initial phase of the events usually lasted only tens to hundreds of seconds before the explosion/gas emission started and the system recovered. The short duration of this process points at rapid transport of fluids rather than magma ascent to generate the pressure changes. We suggest the propagation of tensile hydraulic fractures as viable mechanism to provide a pathway for fluid migration in the magmatic system at the observed time scale. Fluid mobilization was initiated by a sudden destabilization of large pockets of already segregated fluid in the magma chambers. Our study demonstrates that geodetic observables can provide unprecedented insights into complex dynamic processes within a magmatic system commonly assessed by theoretical modeling and petrologic observations. Key Points Strain data analysis from explosions/degassing events at Soufriere Hills Volcano Pressure release deep within the magmatic system sec-min prior to events Rapid gas rise from magma reservoir to surface via tensile hydraulic fractures © 2014. American Geophysical Union. All Rights Reserved
Variation in population levels of sedentary time in European adults according to cross European studies: a systematic literature review within DEDIPAC
peer-reviewedBackground: Sedentary behaviour is increasingly recognized as a public health risk that needs to be monitored at
the population level. Across Europe, there is increasing interest in assessing population levels of sedentary time. This
systematic literature review aims to provide an overview of all existing cross-European studies that measure
sedentary time in adults, to describe the variation in population levels across these studies and to discuss the
impact of assessment methods.
Methods: Six literature databases (PubMed, EMBASE, CINAHL, PsycINFO, SportDiscus and OpenGrey) were searched,
supplemented with backward- and forward tracking and searching authors’ and experts’ literature databases.
Articles were included if they reported on observational studies measuring any form of sedentary time in the
general population in two or more European countries. Each record was reviewed, extracted and assessed by two
independent researchers, and disagreements were resolved by a third researcher. The review protocol of this review
is registered in the PROSPERO database under registration number CRD42014010335.
Results: Of the 9,756 unique articles that were identified in the search, twelve articles were eligible for inclusion in
this review, reporting on six individual studies and three Eurobarometer surveys. These studies represented 2 to 29
countries, and 321 to 65,790 participants. Eleven studies focused on total sedentary time, while one studied screen
time. The majority of studies used questionnaires to assess sedentary time, while two studies used accelerometers.
Total sedentary time was reported most frequently and varied from 150 (median) to 620 (mean) minutes per day
aConclusions: One third of European countries were not included in any of the studies. Objective measures of
European adults are currently limited, and most studies used single-item self-reported questions without assessing
sedentary behaviour types or domains. Findings varied substantially between studies, meaning that population
levels of sedentary time in European adults are currently unknown. In general, people living in northern Europe
countries appear to report more sedentary time than southern Europeans. The findings of this review highlight the
need for standardisation of the measurement methods and the added value of cross-European surveillance of
sedentary behaviour.cross studies and countries
Transcriptome analysis of embryonic mammary cells reveals insights into mammary lineage establishment
Introduction: The mammary primordium forms during embryogenesis as a result of inductive interactions between its constitutive tissues, the mesenchyme and epithelium, and represents the earliest evidence of commitment to the mammary lineage. Previous studies of embryonic mouse mammary epithelium indicated that, by mid-gestation, these cells are determined to a mammary cell fate and that a stem cell population has been delimited. Mammary mesenchyme can induce mammary development from simple epithelium even across species and classes, and can partially restore features of differentiated tissue to mouse mammary tumours in co-culture experiments. Despite these exciting properties, the molecular identity of embryonic mammary cells remains to be fully characterised.
Methods: Here, we define the transcriptome of the mammary primordium and the two distinct cellular compartments that comprise it, the mammary primordial bud epithelium and mammary mesenchyme. Pathway and network analysis was performed and comparisons of embryonic mammary gene expression profiles to those of both postnatal mouse and human mammary epithelial cell sub-populations and stroma were made.
Results: Several of the genes we have detected in our embryonic mammary cell signatures were previously shown to regulate mammary cell fate and development, but we also identified a large number of novel candidates. Additionally, we determined genes that were expressed by both embryonic and postnatal mammary cells, which represent candidate regulators of mammary cell fate, differentiation and progenitor cell function that could signal from mammary lineage inception during embryogenesis through postnatal development. Comparison of embryonic mammary cell signatures with those of human breast cells identified potential regulators of mammary progenitor cell functions conserved across species.
Conclusions: These results provide new insights into genetic regulatory mechanisms of mammary development, particularly identification of novel potential regulators of mammary fate and mesenchymal-epithelial cross-talk. Since cancers may represent diseases of mesenchymal-epithelial communications, we anticipate these results will provide foundations for further studies into the fundamental links between developmental, stem cell and breast cancer biology
Variability of systemic and oro-dental phenotype in two families with non-lethal Raine syndrome with FAM20C mutations
Background: Raine syndrome (RS) is a rare autosomal recessive bone dysplasia typified by osteosclerosis and dysmorphic facies due to FAM20C mutations. Initially reported as lethal in infancy, survival is possible into adulthood. We describe the molecular analysis and clinical phenotypes of five individuals from two consanguineous Brazilian families with attenuated Raine Syndrome with previously unreported features. Methods: The medical and dental clinical records were reviewed. Extracted deciduous and permanent teeth as well as oral soft tissues were analysed. Whole exome sequencing was undertaken and FAM20C cDNA sequenced in family 1. Results: Family 1 included 3 siblings with hypoplastic Amelogenesis Imperfecta (AI) (inherited abnormal dental enamel formation). Mild facial dysmorphism was noted in the absence of other obvious skeletal or growth abnormalities. A mild hypophosphataemia and soft tissue ectopic mineralization were present. A homozygous FAM20C donor splice site mutation (c.784 + 5 g > c) was identified which led to abnormal cDNA sequence. Family 2 included 2 siblings with hypoplastic AI and tooth dentine abnormalities as part of a more obvious syndrome with facial dysmorphism. There was hypophosphataemia, soft tissue ectopic mineralization, but no osteosclerosis. A homozygous missense mutation in FAM20C (c.1487C > T; p.P496L) was identified. Conclusions: The clinical phenotype of non-lethal Raine Syndrome is more variable, including between affected siblings, than previously described and an adverse impact on bone growth and health may not be a prominent feature. By contrast, a profound failure of dental enamel formation leading to a distinctive hypoplastic AI in all teeth should alert clinicians to the possibility of FAM20C mutations
Whole exome sequencing coupled with unbiased functional analysis reveals new Hirschsprung disease genes
Background: Hirschsprung disease (HSCR), which is congenital obstruction of the bowel, results from a failure of enteric nervous system (ENS) progenitors to migrate, proliferate, differentiate, or survive within the distal intestine. Previous studies that have searched for genes underlying HSCR have focused on ENS-related pathways and genes not fitting the current knowledge have thus often been ignored. We identify and validate novel HSCR genes using whole exome sequencing (WES), burden tests, in silico prediction, unbiased in vivo analyses of the mutated genes in zebrafish, and expression analyses in zebrafish, mouse, and human. Results: We performed de novo mutation (DNM) screening on 24 HSCR trios. We identify 28 DNMs in 21 different genes. Eight of the DNMs we identified occur in RET, the main HSCR gene, and the remaining 20 DNMs reside in genes not reported in the ENS. Knockdown of all 12 genes with missense or loss-of-function DNMs showed that the orthologs of four genes (DENND3, NCLN, NUP98, and TBATA) are indispensable for ENS development in zebrafish, and these results were confirmed by CRISPR knockout. These genes are also expressed in human and mouse gut and/or ENS progenitors. Importantly, the encoded proteins are linked to neuronal processes shared by the central nervous system and the ENS. Conclusions: Our data open new fields of investigation into HSCR pathology and provide novel insights into the development of the ENS. Moreover, the study demonstrates that functional analyses of genes carrying DNMs are warranted to delineate the full genetic architecture of rare complex diseases
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