274 research outputs found
Comparison between seismic vulnerability models and experimental dynamic properties of existing buildings in France
Elastic fundamental frequency is a key-parameter of simplified seismic design and vulnerability assessment methods. Empirical relationships exist in codes to estimate this frequency but they miss experimental data to validate them accounting for national feature of building design and, above all, corresponding uncertainties. Even if resonance frequency extracted from ambient vibrations may be larger than the elastic frequency (at yield) generally used in earthquake engineering, ambient vibration recordings may provide a large set of data for statistical analysis of periods versus building characteristics relationships. We recorded ambient vibrations and estimated the fundamental frequency of about 60 buildings of various types (RC and masonry) in Grenoble City (France). These data complete the set existing yet, made of 26 RC-buildings of Grenoble (Farsi and Bard 2004) and 28 buildings in Nice (France) (Dunand 2005). Statistical analysis of these experimental data was performed for fundamental frequencies of RC shear wall structures and the results are compared with existing relationships. Only building height or number of stories has a statistical relevancy to estimate the resonance frequency but the variability associated to the proposed relationships is large. Moreover, we compared the elastic part of capacity curves of RC and masonry buildings used in the European Risk-UE method for vulnerability assessment with the experimental frequencies. The variability is also large and the curves may not be consistent with French existing building
Influence of thermal and mechanical cracks on permeability and elastic wave velocities in a basalt from Mt. Etna volcano subjected to elevated pressure
We report simultaneous laboratory measurements of seismic velocities and fluid permeability on lava flow
basalt from Etna (Italy). Results were obtained for dry and saturated samples deformed under triaxial
compression. During each test, the effective pressure was first increased up to 190 MPa to investigate the
effect of pre-existing crack closure on seismic properties. Then, the effective pressure was unloaded down to
20 MPa, a pressure which mirrors the stress field acting under a lava pile of approximately 1.5â2 km thick, and
deviatoric stress was increased until failure of the specimens.
Using an effective medium model, the measured elastic wave velocities were inverted in terms of two crack
densities: Ïi the crack density of the pre-existing thermal cracks and Ïv the crack density of the stress-induced
cracks. In addition a link was established between elastic properties (elastic wave velocities Vp and Vs) and
permeability using a statistical permeability model.
Our results show that the velocities increase with increasing hydrostatic pressure up to 190 MPa, due to the
closure of the pre-existing thermal cracks. This is interpreted by a decrease of the crack density Ïi from ~1 to
0.2. The effect of pre-existing cracks closure is also highlighted by the permeability evolution which decreases
of more than two orders of magnitude.
Under deviatoric loading, the velocities signature is interpreted, in the first stage of the loading, by the closure
of the pre-existing thermal cracks. However, with increasing deviatoric loading newly-formed vertical cracks
nucleate and propagate. This is clearly seen from the velocity signature and its interpretation in term of crack
density, the location of the acoustic emission sources, and from microstructural observations. This
competition between pre-existing cracks closure and propagation of vertical cracks is also seen from the
permeability evolution, and our study shows that mechanically-induced cracks has lesser influence on
permeability change than pre-existing thermal cracks
Laboratory micro-seismic signature of shear faulting and fault slip in shale
This article reports the results of a triaxial deformation experiment conducted on a transversely isotropic shale specimen. This specimen was instrumented with ultrasonic transducers to monitor the evolution of the micro-seismic activity induced by shear faulting (triaxial failure) and subsequent fault slip at two different rates. The strain data demonstrate the anisotropy of the mechanical (quasi-static) compliance of the shale; the P-wave velocity data demonstrate the anisotropy of the elastic (dynamic) compliance of the shale. The spatio-temporal evolution of the micro-seismic activity suggests the development of two distinct but overlapping shear faults, a feature similar to relay ramps observed in large-scale structural geology. The shear faulting of the shale specimen appears quasi-aseismic, at least in the 0.5 MHz range of sensitivity of the ultrasonic transducers used in the experiment. Concomitantly, the rate of micro-seismic activity is strongly correlated with the imposed slip rate and the evolution of the axial stress. The moment tensor inversion of the focal mechanism of the high quality micro-seismic events recorded suggests a transition from a non-shear dominated to a shear dominated micro-seismic activity when the rock evolves from initial failure to larger and faster slip along the fault. The frictional behaviour of the shear faults highlights the possible interactions between small asperities and slow slip of a velocity-strengthening fault, which could be considered as a realistic experimental analogue of natural observations of non-volcanic tremors and (very) low-frequency earthquakes triggered by slow slip events
A Broadband Laboratory Study of the Seismic Properties of Cracked and Fluid-Saturated Synthetic Glass Media
For better understanding of frequency dependence (dispersion) of seismic wave velocities caused by stressâinduced fluid flow, broadband laboratory measurements were performed on a suite of synthetic glass media containing both equant pores and thermal cracks. Complementary forced oscillation, resonant bar, and ultrasonic techniques provided access to millihertzâhertz frequencies, ~1 kHz frequency, and ~1 MHz frequency, respectively. The wave speeds or effective elastic moduli and associated dissipation were measured on samples under dry, argonâ or nitrogenâsaturated, and waterâsaturated conditions in sequence. The elastic moduli, in situ permeability, and crack porosity inferred from in situ Xâray computed tomography all attest to strong pressureâinduced crack closure for differential (confiningâminusâpore) pressures <30 MPa, consistent with zeroâpressure crack aspect ratios <4 Ă 10â4. The low permeabilities of these materials allow access to undrained conditions, even at subhertz frequencies. The ultrasonically measured elastic moduli reveal consistently higher shear and bulk moduli upon fluid saturationâdiagnostic of the saturatedâisolated regime. For a glass rod specimen, containing cracks but no pores, saturatedâisolated conditions apparently persist to subhertz frequenciesârequiring in situ aspect ratios (minimum/maximum dimension) <10â5. In marked contrast, the shear modulus measured at subhertz frequencies on a cracked glass bead specimen of 5% porosity, is insensitive to fluid saturation, consistent with the BiotâGassmann model for the saturatedâisobaric regime. The measured dispersion of the shear modulus approaches 10% over the millihertzâmegahertz frequency range for the cracked and fluidâsaturated mediaâimplying that laboratory ultrasonic data should be used with care in the interpretation of field data
Work-related risk factors for incidence of lateral epicondylitis in a large working population
Objectives This study aims to estimate the association between repeated measures of occupational risk factors and the incidence of lateral epicondylitis in a large working population.
Methods A total of 3710 workers in a French region were included in 2002â2005, and among them 1046 had a complete follow-up in 2007â2010. At both stages, occupational health physicians assessed the presence of lateral epicondylitis and workers self-reported their occupational exposures. Poisson models were performed to assess the incidence rate ratios (IRR) separately by sex using multiple imputed data.
Results The annual incidence rate of lateral epicondylitis was estimated as 1.0 [95% confidence interval (95% CI) 0.7â1.3] per 100 workers among men and 0.9 (95% CI 0.6â1.3) among women. Workers aged >45 years had higher incidence than those aged <30 years (significant at 10%). Among men, high physical exertion combined with elbow flexion/extension or extreme wrist bending (>2 hours/day) was a risk factor, with an age-adjusted IRR of 3.2 (95% CI 1.5â6.4) for workers exposed at both questionnaires [3.3 (95% CI 1.4â7.6) among women].
Conclusions This study highlights the importance of temporal dimensions for occupational risk factors on the incidence of lateral epicondylitis. Further research should evaluate the risk associated with the duration and repetition of occupational exposure on the incidence of lateral epicondylitis
Analysis of SNP-SNP interactions and bone quantitative ultrasound parameter in early adulthood
Background: Osteoporosis individual susceptibility is determined by the interaction of multiple genetic variants
and environmental factors. The aim of this study was to conduct SNP-SNP interaction analyses in candidate genes
influencing heel quantitative ultrasound (QUS) parameter in early adulthood to identify novel insights into the
mechanism of disease.
Methods: The study population included 575 healthy subjects (mean age 20.41; SD 2.36). To assess bone mass QUS
was performed to determine Broadband ultrasound attenuation (BUA, dB/MHz). A total of 32 SNPs mapping to loci
that have been characterized as genetic markers for QUS and/or BMD parameters were selected as genetic markers
in this study. The association of all possible SNP pairs with QUS was assessed by linear regression and a SNP-SNP
interaction was defined as a significant departure from additive effects.
Results: The pairwise SNP-SNP analysis showed multiple interactions. The interaction comprising SNPs rs9340799
and rs3736228 that map in the ESR1 and LRP5 genes respectively, revealed the lowest p value after adjusting for
confounding factors (p-value = 0.001, ÎČ (95% CI) = 14.289 (5.548, 23.029). In addition, our model reported others
such as TMEM135-WNT16 (p = 0.007, ÎČ(95%CI) = 9.101 (2.498, 15.704), ESR1-DKK1 (p = 0.012, ÎČ(95%CI) = 13.641 (2.
959, 24.322) or OPG-LRP5 (p = 0.012, ÎČ(95%CI) = 8.724 (1.936, 15.512). However, none of the detected interactions
remain significant considering the Bonferroni significance threshold for multiple testing (p<0.0001).
Conclusion: Our analysis of SNP-SNP interaction in candidate genes of QUS in Caucasian young adults reveal several
interactions, especially between ESR1 and LRP5 genes, that did not reach statistical significance. Although our results do
not support a relevant genetic contribution of SNP-SNP epistatic interactions to QUS in young adults, further studies in
larger independent populations would be necessary to support these preliminary findings.This study was supported by a grant PI-0414-2014 from ConsejerĂa de Salud
(Junta de AndalucĂa, Spain). Correa-RodrĂguez M is a predoctoral fellow (FPU13/
00143) from the Ministerio de EducaciĂłn, Cultura y Deporte (Programa de
FormaciĂłn del Profesorado Universitario)
Erratum: The solar orbiter radio and plasma waves (RPW) instrument (Astronomy and Astrophysics (2020) 642 (A12) DOI: 10.1051/0004-6361/201936214)
The erratum concerns Fig. 9 entitled "Antenna radio-electrical properties" for which some of the parameters are not correct. The new figure with new parameters is provided in Fig. 1 of this corrigendum. Fig. 1. Corrected Antenna radio-electrical properties. (Figure Presented)
Single nucleotide polymorphisms in bone turnover-related genes in Koreans: ethnic differences in linkage disequilibrium and haplotype
<p>Abstract</p> <p>Background</p> <p>Osteoporosis is defined as the loss of bone mineral density that leads to bone fragility with aging. Population-based case-control studies have identified polymorphisms in many candidate genes that have been associated with bone mass maintenance or osteoporotic fracture. To investigate single nucleotide polymorphisms (SNPs) that are associated with osteoporosis, we examined the genetic variation among Koreans by analyzing 81 genes according to their function in bone formation and resorption during bone remodeling.</p> <p>Methods</p> <p>We resequenced all the exons, splice junctions and promoter regions of candidate osteoporosis genes using 24 unrelated Korean individuals. Using the common SNPs from our study and the HapMap database, a statistical analysis of deviation in heterozygosity depicted.</p> <p>Results</p> <p>We identified 942 variants, including 888 SNPs, 43 insertion/deletion polymorphisms, and 11 microsatellite markers. Of the SNPs, 557 (63%) had been previously identified and 331 (37%) were newly discovered in the Korean population. When compared SNPs in the Korean population with those in HapMap database, 1% (or less) of SNPs in the Japanese and Chinese subpopulations and 20% of those in Caucasian and African subpopulations were significantly differentiated from the Hardy-Weinberg expectations. In addition, an analysis of the genetic diversity showed that there were no significant differences among Korean, Han Chinese and Japanese populations, but African and Caucasian populations were significantly differentiated in selected genes. Nevertheless, in the detailed analysis of genetic properties, the LD and Haplotype block patterns among the five sub-populations were substantially different from one another.</p> <p>Conclusion</p> <p>Through the resequencing of 81 osteoporosis candidate genes, 118 unknown SNPs with a minor allele frequency (MAF) > 0.05 were discovered in the Korean population. In addition, using the common SNPs between our study and HapMap, an analysis of genetic diversity and deviation in heterozygosity was performed and the polymorphisms of the above genes among the five populations were substantially differentiated from one another. Further studies of osteoporosis could utilize the polymorphisms identified in our data since they may have important implications for the selection of highly informative SNPs for future association studies.</p
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