3,480 research outputs found
Influence of Vertical Ground Motions on the Seismic Fragility Modeling of a Bridge-Soil-Foundation System
This paper explores the effects of vertical ground motions (VGMs) on the
component fragility of a coupled bridged-soil-foundation (CBSF) system with
liquefaction potential, and highlights the unique considerations on the demand
and capacity model required for fragility analysis under VGMs. Optimal intensity
measures (IMs) that account for VGMs are identified. Moreover, fragility curves
that consider capacity change with fluctuating axial force are derived. Results
show that the presence of VGMs has a minor effect on the failure probabilities
of piles and expansion bearings, while it has a great influence on fixed bearings.
Whether VGMs have an impact on column fragilities depends on the design axial
load ratio. Finally, more accurate fragility surfaces are derived, which are compared
with results of conventional fragility curves. This study highlights the
important role that VGMs play in the selection of optimal IMs, and the capacity
and fragility representation of certain components of CBSF systems
A 2dF spectroscopic study of globular clusters in NGC 5128: Probing the formation history of the nearest giant Elliptical
We have performed a spectroscopic study of globular clusters (GCs) in the
giant elliptical NGC 5128 using the 2dF facility at the Anglo-Australian
telescope. We obtained integrated optical spectra for a total of 254 GCs, 79 of
which are newly confirmed on the basis of their radial velocities and spectra.
In addition, we obtained an integrated spectrum of the galaxy starlight along
the southern major axis. We derive an empirical metallicity distribution
function (MDF) for 207 GCs (~14 of the estimated total GC system) based upon
Milky Way GCs. This MDF is multimodal at high statistical significance with
peaks at [Z/H]~-1.3 and -0.5. A comparison between the GC MDF and that of the
stellar halo at 20 kpc (~4 Reff) reveals close coincidence at the metal-rich
ends of the distributions. However, an inner 8 kpc stellar MDF shows a clear
excess of metal-rich stars when compared to the GCs. We compare a higher S/N
subsample (147 GCs) with two stellar population models which include non-solar
abundance ratio corrections. The vast majority of our sample (~90%) appears
old, with ages similar to the Milky Way GC system. There is evidence for a
population of intermediate-age (~4-8 Gy) GCs (<15% of the sample) which are on
average more metal-rich than the old GCs. We also identify at least one younger
cluster (~1-2 Gy) in the central regions of the galaxy. Our observations are
consistent with a picture where NGC 5128 has undergone at least two mergers
and/or interactions involving star formation and limited GC formation since
z=1, however the effect of non-canonical hot stellar populations on the
integrated spectra of GCs remains an outstanding uncertainty in our GC age
estimates.Comment: 17 figures, some long table
Seasonal changes of ice surface characteristics and productivity in the ablation zone of the Greenland Ice Sheet
Field and remote sensing observations in the ablation zone of the Greenland
Ice Sheet have revealed a diverse range of ice surface characteristics,
primarily reflecting the variable distribution of fine debris (cryoconite).
This debris reduces the surface albedo and is therefore an important control
on melt rates and ice sheet mass balance. Meanwhile, studies of ice sheet
surface biological processes have found active microbial communities
associated with the cryoconite debris, which may themselves modify the
cryoconite distribution. Due to the considerable difficulties involved with
collecting ground-based observations of the ice surface, our knowledge of
the physical and biological surface processes, and their links, remains very
limited. Here we present data collected at a field camp established in the
ice sheet ablation zone at 67° N, occupied for almost the entire
melt season (26 May–10 August 2012), with the aim of gaining a much more
detailed understanding of the physical and biological processes occurring on
the ice surface. These data sets include quadrat surveys of surface type,
measurements of ice surface ablation, and in situ biological oxygen demand
incubations to quantify microbial activity. In addition, albedo at the site
was retrieved from AVHRR (Advanced Very High Resolution Radiometer) remote sensing data. Observations of the areal
coverage of different surface types revealed a rapid change from complete
snow cover to the "summer" (summer study period) ice surface of patchy debris ("dirty ice") and
cryoconite holes. There was significant correlation between surface albedo,
cryoconite hole coverage and surface productivity during the melt season,
but microbial activity in "dirty ice" was not correlated with albedo and
varied widely throughout the season. While this link suggests the potential
for a remote-sensing approach to monitoring cryoconite hole biological
processes, very wide seasonal and spatial variability in net surface
productivity demonstrates the need for caution when extrapolating point
measurements of biological processes to larger temporal or spatial scales
Bisphosphonates regulate cell growth and gene expression in the UMR 106-01 clonal rat osteosarcoma cell line
Local growth of osteosarcoma involves destruction of host bone by proteolytic mechanisms and/or host osteoclast activation. Osteoclast formation and activity are regulated by osteoblast-derived factors such as the osteoclast differentiating factor, receptor activator of NF-κB ligand (RANKL) and the inhibitor osteoprotegerin (OPG). We have investigated the in vitro effects of bisphosphonates on a clonal rat osteosarcoma cell line. The aminobisphosphonate pamidronate was added to UMR 106-01 cell cultures (10−8M to 10−4M up to 5 days). The non-aminobisphosphonate clodronate was administered for the same time periods (10−6M to 10−2M). Cell proliferation, apoptosis and mRNA expression was assessed. Both agents inhibited cell proliferation in a time- and dose-dependent manner. ELISA analysis demonstrated an increase in DNA fragmentation although there was no significant dose-related difference between the doses studied. Bisphosphonate-treated cultures had a greater subpopulation of cells exhibiting morphological changes of apoptosis. Expression of mRNA for osteopontin and RANKL was down-regulated by both agents, while the expression of mRNA for alkaline phosphatase, pro-α1(I) collagen and OPG was not altered. Out in vitro work suggests the bisphosphonates not only have direct effects on osteosarcoma cell growth and apoptosis, but also, by altering the relative expression of osteoclast-regulating factors, they may inhibit the activity of osteoclasts and their recruitment. © 2001 Cancer Research Campaignhttp://www.bjcancer.co
Feshbach resonances and collapsing Bose-Einstein condensates
We investigate the quantum state of burst atoms seen in the recent Rb-85
experiments at JILA. We show that the presence of a resonance scattering state
can lead to a pairing instability generating an outflow of atoms with energy
comparable to that observed. A resonance effective field theory is used to
study this dynamical process in an inhomogeneous system with spherical
symmetry
Association of FCGR3A and FCGR3B haplotypes with rheumatoid arthritis and primary Sjögren's syndrome [POSTER PRESENTATION]
Background
Rheumatoid arthritis (RA) is an autoimmune disease that is thought to arise from a complex interaction between multiple genetic factors and environmental triggers. We have previously demonstrated an association between a Fc gamma receptor (FcγR) haplotype and RA in a cross-sectional cohort of RA patients. We have sought to confirm this association in an inception cohort of RA patients and matched controls. We also extended our study to investigate a second autoanti-body associated rheumatic disease, primary Sjögren's syndrome (PSS).
Methods
The FCGR3A-158F/V and FCGR3B-NA1/NA2 functional polymorphisms were examined for association in an inception cohort of RA patients (n = 448), and a well-characterised PSS cohort (n = 83) from the United Kingdom. Pairwise disequilibrium coefficients (D') were calculated in 267 Blood Service healthy controls. The EHPlus program was used to estimate haplotype frequencies for patients and controls and to determine whether significant linkage disequilibrium was present. A likelihood ratio test is performed to test for differences between the haplotype frequencies in cases and controls. A permutation procedure implemented in this program enabled 1000 permutations to be performed on all haplotype associations to assess significance.
Results
There was significant linkage disequilibrium between FCGR3A and FCGR3B (D' = -0.445, P = 0.001). There was no significant difference in the FCGR3A or FCGR3B allele or genotype frequencies in the RA or PSS patients compared with controls. However, there was a significant difference in the FCGR3A-FCGR3B haplotype distributions with increased homozygosity for the FCGR3A-FCGR3B 158V-NA2 haplotype in both our inception RA cohort (odds ratio = 2.15, 95% confidence interval = 1.1–4.2 P = 0.027) and PSS (odds ratio = 2.83, 95% confidence interval = 1.0–8.2, P = 0.047) compared with controls. The reference group for these analyses comprised individuals who did not possess a copy of the FCGR3A-FCGR3B 158V-NA2 haplotype.
Conclusions
We have confirmed our original findings of association between the FCGR3A-FCGR3B 158V-NA2 haplotype and RA in a new inception cohort of RA patients. This suggests that there may be an RA-susceptibility gene at this locus. The significant increased frequency of an identical haplotype in PSS suggests the FcγR genetic locus may contribute to the pathogenesis of diverse autoantibody-mediated rheumatic diseases
Dissipative Particle Dynamics with Energy Conservation
The stochastic differential equations for a model of dissipative particle
dynamics with both total energy and total momentum conservation in the
particle-particle interactions are presented. The corresponding Fokker-Planck
equation for the evolution of the probability distribution for the system is
deduced together with the corresponding fluctuation-dissipation theorems
ensuring that the ab initio chosen equilibrium probability distribution for the
relevant variables is a stationary solution. When energy conservation is
included, the system can sustain temperature gradients and heat flow can be
modeled.Comment: 7 pages, submitted to Europhys. Let
Interventions to Promote Cancer Awareness and Early Presentation: Systematic Review
Low cancer awareness contributes to delay in presentation for cancer symptoms and may lead to delay in cancer diagnosis. The aim of this study was to review the evidence for the effectiveness of interventions to raise cancer awareness and promote early presentation in cancer to inform policy and future research. We searched bibliographic databases and reference lists for randomised controlled trials of interventions delivered to individuals, and controlled or uncontrolled studies of interventions delivered to communities. We found some evidence that interventions delivered to individuals modestly increase cancer awareness in the short term and insufficient evidence that they promote early presentation. We found limited evidence that public education campaigns reduce stage at presentation of breast cancer, malignant melanoma and retinoblastoma
Lessons on Ethical Decision Making from the Bioscience Industry
Mackie and colleagues performed over 100 interviews with managers and executives at 13 bioscience companies to learn about bioindustry ethics from their perspective
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