393 research outputs found
Fluidâdriven tensile fracture and fracture toughness in Nash Point shale at elevated pressure
A number of key processes, both natural and anthropogenic, involve the fracture of rocks subjected to tensile stress, including vein growth and mineralization, and the extraction of hydrocarbons through hydraulic fracturing. In each case, the fundamental material property of modeâI fracture toughness must be overcome in order for a tensile fracture to propagate. While measuring this parameter is relatively straightforward at ambient pressure, estimating fracture toughness of rocks at depth, where they experience confining pressure, is technically challenging. Here we report a new analysis that combines results from thickâwalled cylinder burst tests with quantitative acoustic emission to estimate the modeâI fracture toughness (K_{Ic}) of Nash Point Shale at confining pressure simulating in situ conditions to approximately 1âkm depth. In the most favorable orientation, the pressure required to fracture the rock shell (injection pressure, P_{inj}) increases from 6.1 MPa at 2.2âMPa confining pressure (P_{c}), to 34 MPa at 20âMPa confining pressure. When fractures are forced to cross the shale bedding, the required injection pressures are 30.3 MPa (at P_{c} = 4.5MPa) and 58 MPa (P_{c} = 20 MPa), respectively. Applying the model of AbouâSayed et al. (1978, https://doi.org/10.1029/JB083iB06p02851) to estimate the initial flaw size, we calculate that this pressure increase equates to an increase in K_{Ic} from 0.36 to 4.05 MPa·m^{1/2} as differential fluid pressure (P_{inj} - P_{c}) increases from 3.2 to 22.0 MPa. We conclude that the increasing pressure due to depth in the Earth will have a significant influence on fracture toughness, which is also a function of the inherent anisotropy
Mobile phone use and glioma risk: comparison of epidemiological study results with incidence trends in the United States
Objective In view of mobile phone exposure being classified as a possible human carcinogen by the International Agency for Research on Cancer (IARC), we determined the compatibility of two recent reports of glioma risk (forming the basis of the IARCâs classification) with observed incidence trends in the United States
Compact radio sources and jet-driven AGN feedback in the early Universe: Constraints from integral-field spectroscopy
To investigate the impact of radio jets during the formation epoch of their
massive host galaxies, we present an analysis of two massive, log(M_stel/
M_sun)~10.6 and 11.3, compact radio galaxies at z=3.5, TNJ0205+2242 and
TNJ0121+1320. Their small radio sizes (R<= 10 kpc) are most likely a sign of
youth. We compare their radio properties and gas dynamics with those in well
extended radio galaxies at high redshift, which show strong evidence for
powerful, jet-driven outflows of significant gas masses (M 10^9-10 M_sun). Our
analysis combines rest-frame optical integral-field spectroscopy with existing
radio imaging, CO emission line spectra, and rest-frame UV spectroscopy.
[OIII]5007 line emission is compact in both galaxies and lies within the region
defined by the radio lobes. For TNJ0205+2242, the Ly-alpha profile narrows
significantly outside the jet radius, indicating the presence of a quiescent
halo. TNJ0121+1320 has two components separated by ~10 kpc and a velocity
offset of ~300 km s^-1. If motions are gravitational, this implies a dynamical
mass of 2x10^11 M_sun for the more massive, radio-loud component. The dynamical
mass, molecular gas mass measured from the CO line emission, and radio
luminosity of these two compact radio galaxies imply that compact radio sources
may well develop large-scale, energetic outflows as observed in extended radio
galaxies, with the potential of removing significant fractions of the ISM from
the host galaxy. The absence of luminous emission line gas extending beyond the
radio emission in these sources agrees with the observed timescales and outflow
rates in extended radio galaxies, and adds further evidence that the energetic,
large-scale outflows observed in extended radio sources (Nesvadba et al. 2006)
are indeed the result of influence of the radio jet.Comment: A&A accepte
The heating mechanism for the warm/cool dust in powerful, radio-loud AGN
The uncertainty surrounding the nature of the heating mechanism for the dust
that emits at mid- to far-IR (MFIR) wavelengths in active galaxies limits our
understanding of the links between active galactic nuclei (AGN) and galaxy
evolution, as well as our ability to interpret the prodigious infrared and
sub-mm emission of some of the most distant galaxies in the Universe. Here we
report deep Spitzer observations of a complete sample of powerful, intermediate
redshift (0.05 < z < 0.7) radio galaxies and quasars. We show that AGN power,
as traced by [OIII]5007 emission, is strongly correlated with both the mid-IR
(24 micron) and the far-IR (70 micron) luminosities, however, with increased
scatter in the 70 micron correlation. A major cause of this increased scatter
is a group of objects that falls above the main correlation and displays
evidence for prodigious recent star formation activity at optical wavelengths,
along with relatively cool MFIR colours. These results provide evidence that
illumination by the AGN is the primary heating mechanism for the dust emitting
at both 24 and 70 microns, with starbursts dominating the heating of the cool
dust in only 20 -- 30% of objects. This implies that powerful AGN are not
always accompanied by the type of luminous starbursts that are characteristic
of the peak of activity in major gas-rich mergers.Comment: 13 pages, 3 figures. Accepted for publication in astrophysical
journal letter
How do women prepare for pregnancy? Preconception experiences of women attending antenatal services and views of health professionals
Copyright: © 2014 Stephenson et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Main objective - To determine the extent to which women plan and prepare for pregnancy.
Methods - Cross-sectional questionnaire survey of pregnant women attending three maternity services in London about knowledge and uptake of preconception care; including a robust measure of pregnancy planning, and phone interviews with a range of health care professionals.
Main results - We recruited 1173/1288 (90%) women, median age of 32 years. 73% had clearly planned their pregnancy, 24% were ambivalent and only 3% of pregnancies were unplanned. 51% of all women and 63% of those with a planned pregnancy took folic acid before pregnancy. 21% of all women reported smoking and 61% reported drinking alcohol in the 3 months before pregnancy; 48% of smokers and 41% of drinkers reduced or stopped before pregnancy. The 51% of all women who reported advice from a health professional before becoming pregnant were more likely to adopt healthier behaviours before pregnancy [adjusted odds ratios for greatest health professional input compared with none were 2.34 (95% confidence interval 1.54â3.54) for taking folic acid and 2.18 (95% CI 1.42â3.36) for adopting a healthier diet before pregnancy]. Interviews with 20 health professionals indicated low awareness of preconception health issues, missed opportunities and confusion about responsibility for delivery of preconception care.
Significance of the findings - Despite a high level of pregnancy planning, awareness of preconception health among women and health professionals is low, and responsibility for providing preconception care is unclear. However, many women are motivated to adopt healthier behaviours in the preconception period, as indicated by halving of reported smoking rates in this study. The link between health professional input and healthy behaviour change before pregnancy is a new finding that should invigorate strategies to improve awareness and uptake of pre-pregnancy health care, and bring wider benefits for public health.Department of Healt
PKS2250-41: a case study for triggering
We present the results of a multiwavelength study of the z = 0.31 radio
source PKS2250-41. Integral field unit and long-slit spectroscopy obtained
using VIMOS and FORS1 on the VLT, and archival HST optical imaging observations
are used to study the morphology, kinematics and ionisation state of the
extended emission line region (EELR) surrounding this source, and also a
companion galaxy at a similar redshift. Near-infrared imaging observations
obtained using the NTT are used to analyse the underlying galaxy morphologies.
The EELR displays a complex variety of different gas kinematics and ionization
states, consistent with a mixture of radio source shocks and AGN
photoionization. The radio galaxy is likely to lie within a group environment,
and is plausibly undergoing interactions with one or more other objects. The
disk-like galaxy to the northeast of the radio source lies at a similar
redshift to the radio galaxy itself, and has its major axis position angle
aligned with the filamentary continuum and line emission extending outwards
from the radio galaxy. This filamentary structure is most plausibly interpreted
as a tidal structure associated with an interaction involving the radio source
host galaxy and the aligned companion galaxy to the north-east; this encounter
may have potentially triggered the current epoch of radio source activity.
Overall, PKS2250-41 displays some of the best evidence that radio source
activity can be triggered in this manner. [abridged]Comment: 16 pages, 13 figures (some colour). Accepted for publication in
MNRAS. Abstract abridge
Toward Human-Carnivore Coexistence: Understanding Tolerance for Tigers in Bangladesh
Fostering local community tolerance for endangered carnivores, such as tigers (Panthera tigris), is a core component of many conservation strategies. Identification of antecedents of tolerance will facilitate the development of effective tolerance-building conservation action and secure local community support for, and involvement in, conservation initiatives. We use a stated preference approach for measuring tolerance, based on the âWildlife Stakeholder Acceptance Capacityâ concept, to explore villagersâ tolerance levels for tigers in the Bangladesh Sundarbans, an area where, at the time of the research, human-tiger conflict was severe. We apply structural equation modeling to test an a priori defined theoretical model of tolerance and identify the experiential and psychological basis of tolerance in this community. Our results indicate that beliefs about tigers and about the perceived current tiger population trend are predictors of tolerance for tigers. Positive beliefs about tigers and a belief that the tiger population is not currently increasing are both associated with greater stated tolerance for the species. Contrary to commonly-held notions, negative experiences with tigers do not directly affect tolerance levels; instead, their effect is mediated by villagersâ beliefs about tigers and risk perceptions concerning human-tiger conflict incidents. These findings highlight a need to explore and understand the socio-psychological factors that encourage tolerance towards endangered species. Our research also demonstrates the applicability of this approach to tolerance research to a wide range of socio-economic and cultural contexts and reveals its capacity to enhance carnivore conservation efforts worldwide
Exploring the conformational dynamics of alanine dipeptide in solution subjected to an external electric field: A nonequilibrium molecular dynamics simulation
In this paper, we investigate the conformational dynamics of alanine
dipeptide under an external electric field by nonequilibrium molecular dynamics
simulation. We consider the case of a constant and of an oscillatory field. In
this context we propose a procedure to implement the temperature control, which
removes the irrelevant thermal effects of the field. For the constant field
different time-scales are identified in the conformational, dipole moment, and
orientational dynamics. Moreover, we prove that the solvent structure only
marginally changes when the external field is switched on. In the case of
oscillatory field, the conformational changes are shown to be as strong as in
the previous case, and non-trivial nonequilibrium circular paths in the
conformation space are revealed by calculating the integrated net probability
fluxes.Comment: 23 pages, 12 figure
Ancient Yersinia pestis genomes from across Western Europe reveal early diversification during the First Pandemic (541â750)
The first historically documented pandemic caused by Yersinia pestis began as the Justinianic Plague in 541 within the Roman Empire and continued as the so-called First Pandemic until 750. Although paleogenomic studies have previously identified the causative agent as Y. pestis, little is known about the bacteriumâs spread, diversity, and genetic history over the course of the pandemic. To elucidate the microevolution of the bacterium during this time period, we screened human remains from 21 sites in Austria, Britain, Germany, France, and Spain for Y. pestis DNA and reconstructed eight genomes. We present a methodological approach assessing single-nucleotide polymorphisms (SNPs) in ancient bacterial genomes, facilitating qualitative analyses of low coverage genomes from a metagenomic background. Phylogenetic analysis on the eight reconstructed genomes reveals the existence of previously undocumented Y. pestis diversity during the sixth to eighth centuries, and provides evidence for the presence of multiple distinct Y. pestis strains in Europe. We offer genetic evidence for the presence of the Justinianic Plague in the British Isles, previously only hypothesized from ambiguous documentary accounts, as well as the parallel occurrence of multiple derived strains in central and southern France, Spain, and southern Germany. Four of the reported strains form a polytomy similar to others seen across the Y. pestis phylogeny, associated with the Second and Third Pandemics. We identified a deletion of a 45-kb genomic region in the most recent First Pandemic strains affecting two virulence factors, intriguingly overlapping with a deletion found in 17th- to 18th-century genomes of the Second Pandemic. © 2019 National Academy of Sciences. All rights reserved
Epidemiological survey of antimicrobial-resistant of Salmonella in market-age swine
We conducted a survey of antibiotic resistance in Salmonella isolaled from market-age swine at five different farms. These farms, which were sampled between October 1997 and June 1998, were part of a completely integrated Texas swine operation. Four of the farms sampled were farrow-to-finish farms and were sampled three times each. The fifth farm provided replacement gilts for the other farms in the operation and was sampled once. Samples were taken from the lymph nodes and cecal contents at the time of slaughter. Of the 559 Salmonella isolates recovered, 420 were sent to the National Veterinary Services Laboratory for serotyping. Resistance patterns were determined by disk diffusion using thitteen antibiotics, and 320 isolates were analyzed. Resistance was observed to ampicillin, chloramphenicol, chlortetracycline, nitrofurantoin, penicillin G, streptomycin and sulfisoxazole. Only 21 isolates (6.9%) demonstrated no resistance to any of the antibiotics tested. Multidrug resistance (resistance to two or more antibiotics) was observed in 183 isolates (57.2%) with 34 of these isolates 18.6%) resistant to three antibiotics and 26 (8.1 %) resistant to four antibiotics. The most common three drug resistance pattern consisted of chlortetracycline, penicillin G and streptomycin (37 .3% ). All four drug resistance patterns consisted of chlortetracycline, penicillin G, streptomycin and sulfisoxazole ( 100% ). A significant difference was observed between serotypes and between somatic serogroups in their antibiotic resistance patterns. Variation also was observed between farms. As a step in understanding the connection between antibiotic use in agriculture and medicine and emergence of antibiotic resistant bacteria, programs that monitor the levels of antibiotic resistance must be continued. In animal production, where subtherapeutic administration of antibiotics can be common, continued surveillance is especially important
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