1,309 research outputs found
Seismic Response to Injection Well Stimulation in a High-Temperature, High-Permeability Reservoir
Fluid injection into the Earth's crust can induce seismic events that cause damage to local infrastructure but also offer valuable insight into seismogenesis. The factors that influence the magnitude, location, and number of induced events remain poorly understood but include injection flow rate and pressure as well as reservoir temperature and permeability. The relationship between injection parameters and injection-induced seismicity in high-temperature, high-permeability reservoirs has not been extensively studied. Here we focus on the Ngatamariki geothermal field in the central TaupĆ Volcanic Zone, New Zealand, where three stimulation/injection tests have occurred since 2012. We present a catalog of seismicity from 2012 to 2015 created using a matched-filter detection technique. We analyze the stress state in the reservoir during the injection tests from first motion-derived focal mechanisms, yielding an average direction of maximum horizontal compressive stress (SHmax) consistent with the regional NE-SW trend. However, there is significant variation in the direction of maximum compressive stress (Ï1), which may reflect geological differences between wells. We use the ratio of injection flow rate to overpressure, referred to as injectivity index, as a proxy for near-well permeability and compare changes in injectivity index to spatiotemporal characteristics of seismicity accompanying each test. Observed increases in injectivity index are generally poorly correlated with seismicity, suggesting that the locations of microearthquakes are not coincident with the zone of stimulation (i.e., increased permeability). Our findings augment a growing body of work suggesting that aseismic opening or slip, rather than seismic shear, is the active process driving well stimulation in many environments
Superheavy dark matter and ultrahigh energy cosmic rays
The phase of inflationary expansion in the early universe produces superheavy
relics in a mass window between 10^{12} GeV and 10^{14} GeV. Decay or
annihilation of these superheavy relics can explain the observed ultrahigh
energy cosmic rays beyond the Greisen-Zatsepin-Kuzmin cutoff. We emphasize that
the pattern of cosmic ray arrival directions with energies beyond 20 EeV will
decide between the different proposals for the origin of ultrahigh energy
cosmic rays.Comment: Based on an invited talk given by RD at Theory Canada 1, Vancouver,
June 2-5, 200
Reproducing FSL's fMRI data analysis via Nipype:Relevance, challenges, and solutions
The "replication crisis" in neuroscientific research has led to calls for improving reproducibility. In traditional neuroscience analyses, irreproducibility may occur as a result of issues across various stages of the methodological process. For example, different operating systems, different software packages, and even different versions of the same package can lead to variable results. Nipype, an open-source Python project, integrates different neuroimaging software packages uniformly to improve the reproducibility of neuroimaging analyses. Nipype has the advantage over traditional software packages (e.g., FSL, ANFI, SPM, etc.) by (1) providing comprehensive software development frameworks and usage information, (2) improving computational efficiency, (3) facilitating reproducibility through sufficient details, and (4) easing the steep learning curve. Despite the rich tutorials it has provided, the Nipype community lacks a standard three-level GLM tutorial for FSL. Using the classical Flanker task dataset, we first precisely reproduce a three-level GLM analysis with FSL via Nipype. Next, we point out some undocumented discrepancies between Nipype and FSL functions that led to substantial differences in results. Finally, we provide revised Nipype code in re-executable notebooks that assure result invariability between FSL and Nipype. Our analyses, notebooks, and operating software specifications (e.g., docker build files) are available on the Open Science Framework platform
Outcomes Associated with a Home Care Telehealth Intervention
To determine whether adding telehealth technology to traditional home care services increases health-related quality of life (HRQOL) and home care satisfaction, and decreases resource utilization among home care patients. This trial included 37 home care patients receiving services in a Veterans Affairs medical center, randomized into intervention and control groups. Outcome measures included patient satisfaction and HRQOL at baseline and 6-month follow- up, and the use of inpatient and outpatient services before and during the 6-month study period. Intervention group patients reported greater improvement in the mental health component of HRQOL, (t = 2.27; df = 15; p = 0.04). Satisfaction with the telehealth equipment was high (means exceeded 4.0 on six measures ranging from 1â5). However, no statistically significant differences were observed between intervention and control groups in terms of changes in physical health, inpatient admissions, bed days of care, emergency department visits, or general satisfaction with home care services. Intervention group members did show a trend (p = 0.10) toward fewer overall outpatient visits (mean = 29.1; standard deviation [SD] ± 30.1) compared to those receiving traditional home care services (mean = 38.9; SD ± 28.9) The use of telehealth services as an adjunct to traditional home care is associated with greater improvements in mental health status and a trend toward lower use of inpatient and outpatient healthcare services. Further work, utilizing larger sample sizes, is needed to investigate the relationship between telehealth services, the use of healthcare resources, and other outcomes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63227/1/tmj.2006.12.297.pd
More evidence for an intracluster planetary nebulae population in the Virgo cluster
We surveyed a 50 sq arcmin region in the Virgo cluster core to search for
intergalactic planetary nebulae, and found 11 candidates in the surveyed area.
The measured fluxes of these unresolved sources are consistent with these
objects being planetary nebulae from an intracluster population of stars. We
compute the cumulative luminosity function of these 11 planetary nebula
candidates. If we assume that they belong to the Virgo cluster, their
cumulative luminosity function is in good agreement with planetary nebula
luminosity function simulations. This comparison allows us to estimate the
surface mass density of the intracluster stellar population at the surveyed
field in the cluster core.Comment: ApJ Letters, in press. A .ps file is also available at:
http://www.usm.uni-muenchen.de:8001/people/mendez/preprints/preprints.htm
The FORS Deep Field: Field selection, photometric observations and photometric catalog
The FORS Deep Field project is a multi-colour, multi-object spectroscopic
investigation of an approx. 7 times 7 region near the south galactic pole based
mostly on observations carried out with the FORS instruments attached to the
VLT telescopes. It includes the QSO Q 0103-260 (z = 3.36). The goal of this
study is to improve our understanding of the formation and evolution of
galaxies in the young Universe. In this paper the field selection, the
photometric observations, and the data reduction are described. The source
detection and photometry of objects in the FORS Deep Field is discussed in
detail. A combined B and I selected UBgRIJKs photometric catalog of 8753
objects in the FDF is presented and its properties are briefly discussed. The
formal 50% completeness limits for point sources, derived from the co-added
images, are 25.64, 27.69, 26.86, 26.68, 26.37, 23.60 and 21.57 in U, B, g, R,
I, J and Ks (Vega-system), respectively. A comparison of the number counts in
the FORS Deep Field to those derived in other deep field surveys shows very
good agreement.Comment: 15 pages, 11 figures (included), accepted for publication in A&
Light Curves and Period Changes of Type II Cepheids in the Globular Clusters M3 and M5
Light curves in the B, V, and I_c passbands have been obtained for the type
II Cepheids V154 in M3 and V42 and V84 in M5. Alternating cycle behavior,
similar to that seen among RV Tauri variables, is confirmed for V84. Old and
new observations, spanning more than a century, show that V154 has increased in
period while V42 has decreased in period. V84, on the other hand, has shown
large, erratic changes in period that do not appear to reflect the long term
evolution of V84 through the HR diagram.Comment: 28 pages, 12 figure
The Dwarf Irregular/Wolf-Rayet Galaxy NGC4214: I. A New Distance, Stellar Content, and Global Parameters
We present the results of a detailed optical and near-IR study of the nearby
star-forming dwarf galaxy NGC4214. We discuss the stellar content, drawing
particular attention to the intermediate-age and/or old field stars, which are
used as a distance indicator. On images obtained with the Hubble Space
Telescope WFPC2 and NICMOS instruments in the equivalents of the V, R, I, J and
H bands, the galaxy is well resolved into stars. We achieve limiting magnitudes
of F814W ~27 in the WF chips and F110W ~25 in the NIC2. The optical and
near-infrared color-magnitude diagrams confirm a core-halo galaxy morphology:
an inner high surface-brightness young population within ~1.5' (~1 kpc) from
the center of the galaxy, where the stars are concentrated in bright complexes
along a bar-like structure; and a relatively low-surface-brightness, field-star
population extending out to at least 8' (7 kpc). The color-magnitude diagrams
of the core region show evidence of blue and red supergiants, main-sequence
stars, asymptotic giant branch stars and blue loop stars. We identify some
candidate carbon stars from their extreme near-IR color. The field-star
population is dominated by the "red tangle", which contains the red giant
branch. We use the I-band luminosity function to determine the distance based
on the tip-of-the-red-giant-branch method: 2.7\pm0.3 Mpc. This is much closer
than the values usually assumed in the literature, and we provide revised
distance dependent parameters such as physical size, luminosity, HI mass and
star-formation rate.Comment: 24 pages, 19 figures, accepted for publication in the July 2002 issue
of AJ. Version with high resolution figures is available at
http://www.astro.spbu.ru/staff/dio/preprints.htm
Transgenic Expression of the Anti-parasitic Factor TEP1 in the Malaria Mosquito Anopheles gambiae
Mosquitoes genetically engineered to be resistant to Plasmodium parasites represent a promising novel approach in the fight against malaria. The insect immune system itself is a source of anti-parasitic genes potentially exploitable for transgenic designs. The Anopheles gambiae thioester containing protein 1 (TEP1) is a potent anti-parasitic protein. TEP1 is secreted and circulates in the mosquito hemolymph, where its activated cleaved form binds and eliminates malaria parasites. Here we investigated whether TEP1 can be used to create malaria resistant mosquitoes. Using a GFP reporter transgene, we determined that the fat body is the main site of TEP1 expression. We generated transgenic mosquitoes that express TEP1r, a potent refractory allele of TEP1, in the fat body and examined the activity of the transgenic protein in wild-type or TEP1 mutant genetic backgrounds. Transgenic TEP1r rescued loss-of-function mutations, but did not increase parasite resistance in the presence of a wild-type susceptible allele. Consistent with previous reports, TEP1 protein expressed from the transgene in the fat body was taken up by hemocytes upon a challenge with injected bacteria. Furthermore, although maturation of transgenic TEP1 into the cleaved form was impaired in one of the TEP1 mutant lines, it was still sufficient to reduce parasite numbers and induce parasite melanization. We also report here the first use of Transcription Activator Like Effectors (TALEs) in Anopheles gambiae to stimulate expression of endogenous TEP1. We found that artificial elevation of TEP1 expression remains moderate in vivo and that enhancement of endogenous TEP1 expression did not result in increased resistance to Plasmodium. Taken together, our results reveal the difficulty of artificially influencing TEP1-mediated Plasmodium resistance, and contribute to further our understanding of the molecular mechanisms underlying mosquito resistance to Plasmodium parasites
Modeling Supply Networks and Business Cycles as Unstable Transport Phenomena
Physical concepts developed to describe instabilities in traffic flows can be
generalized in a way that allows one to understand the well-known instability
of supply chains (the so-called ``bullwhip effect''). That is, small variations
in the consumption rate can cause large variations in the production rate of
companies generating the requested product. Interestingly, the resulting
oscillations have characteristic frequencies which are considerably lower than
the variations in the consumption rate. This suggests that instabilities of
supply chains may be the reason for the existence of business cycles. At the
same time, we establish some link to queuing theory and between micro- and
macroeconomics.Comment: For related work see http://www.helbing.or
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