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  • 1
    Publication Date: 2016-03-24
    Description: Rotary ATPases couple ATP synthesis or hydrolysis to proton translocation across a membrane. However, understanding proton translocation has been hampered by a lack of structural information for the membrane-embedded a subunit. The V/A-ATPase from the eubacterium Thermus thermophilus is similar in structure to the eukaryotic V-ATPase but has a simpler...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 2
    Publication Date: 2015-06-03
    Description: Earthquake activity in parts of the central United States has increased dramatically in recent years. The space-time distribution of the increased seismicity, as well as numerous published case studies, indicates that the increase is of anthropogenic origin, principally driven by injection of wastewater coproduced with oil and gas from tight formations. Enhanced oil recovery and long-term production also contribute to seismicity at a few locations. Preliminary hazard models indicate that areas experiencing the highest rate of earthquakes in 2014 have a short-term (one-year) hazard comparable to or higher than the hazard in the source region of tectonic earthquakes in the New Madrid and Charleston seismic zones.
    Print ISSN: 1070-485X
    Electronic ISSN: 1938-3789
    Topics: Geosciences
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  • 3
    Publication Date: 2016-11-04
    Description: The U.S. Geological Survey (USGS) has produced a one-year (2016) probabilistic seismic-hazard assessment for the central and eastern United States (CEUS) that includes contributions from both induced and natural earthquakes that are constructed with probabilistic methods using alternative data and inputs. This hazard assessment builds on our 2016 final model ( Petersen et al. , 2016 ) by adding sensitivity studies, illustrating hazard in new ways, incorporating new population data, and discussing potential improvements. The model considers short-term seismic activity rates (primarily 2014–2015) and assumes that the activity rates will remain stationary over short time intervals. The final model considers different ways of categorizing induced and natural earthquakes by incorporating two equally weighted earthquake rate submodels that are composed of alternative earthquake inputs for catalog duration, smoothing parameters, maximum magnitudes, and ground-motion models. These alternatives represent uncertainties on how we calculate earthquake occurrence and the diversity of opinion within the science community. In this article, we also test sensitivity to the minimum moment magnitude between M  4 and M  4.7 and the choice of applying a declustered catalog with b =1.0 rather than the full catalog with b =1.3. We incorporate two earthquake rate submodels: in the informed submodel we classify earthquakes as induced or natural, and in the adaptive submodel we do not differentiate. The alternative submodel hazard maps both depict high hazard and these are combined in the final model. Results depict several ground-shaking measures as well as intensity and include maps showing a high-hazard level (1% probability of exceedance in 1 year or greater). Ground motions reach 0.6 g horizontal peak ground acceleration (PGA) in north-central Oklahoma and southern Kansas, and about 0.2 g PGA in the Raton basin of Colorado and New Mexico, in central Arkansas, and in north-central Texas near Dallas–Fort Worth. The chance of having levels of ground motions corresponding to modified Mercalli intensity (MMI) VI or greater earthquake shaking is 2%–12% per year in north-central Oklahoma and southern Kansas and New Madrid similar to the chance of damage at sites in high-hazard portions of California caused by natural earthquakes. Hazard is also significant in the Raton basin of Colorado/New Mexico; north-central Arkansas; Dallas–Fort Worth, Texas; and in a few other areas. Hazard probabilities are much lower (by about half or more) for exceeding MMI VII or VIII. Hazard is 3- to 10-fold higher near some areas of active-induced earthquakes than in the 2014 USGS National Seismic Hazard Model (NSHM), which did not consider induced earthquakes. This study in conjunction with the LandScan TM Database (2013) indicates that about 8 million people live in areas of active injection wells that have a greater than 1% chance of experiencing damaging ground shaking (MMI≥VI) in 2016. The final model has high uncertainty, and engineers, regulators, and industry should use these assessments cautiously to make informed decisions on mitigating the potential effects of induced and natural earthquakes.
    Print ISSN: 0895-0695
    Electronic ISSN: 1938-2057
    Topics: Geosciences
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  • 4
    Publication Date: 2017-04-27
    Description: We produce a one-year 2017 seismic-hazard forecast for the central and eastern United States from induced and natural earthquakes that updates the 2016 one-year forecast; this map is intended to provide information to the public and to facilitate the development of induced seismicity forecasting models, methods, and data. The 2017 hazard model applies the same methodology and input logic tree as the 2016 forecast, but with an updated earthquake catalog. We also evaluate the 2016 seismic-hazard forecast to improve future assessments. The 2016 forecast indicated high seismic hazard (greater than 1% probability of potentially damaging ground shaking in one year) in five focus areas: Oklahoma–Kansas, the Raton basin (Colorado/New Mexico border), north Texas, north Arkansas, and the New Madrid Seismic Zone. During 2016, several damaging induced earthquakes occurred in Oklahoma within the highest hazard region of the 2016 forecast; all of the 21 moment magnitude ( M ) ≥4 and 3 M ≥5 earthquakes occurred within the highest hazard area in the 2016 forecast. Outside the Oklahoma–Kansas focus area, two earthquakes with M ≥4 occurred near Trinidad, Colorado (in the Raton basin focus area), but no earthquakes with M ≥2.7 were observed in the north Texas or north Arkansas focus areas. Several observations of damaging ground-shaking levels were also recorded in the highest hazard region of Oklahoma. The 2017 forecasted seismic rates are lower in regions of induced activity due to lower rates of earthquakes in 2016 compared with 2015, which may be related to decreased wastewater injection caused by regulatory actions or by a decrease in unconventional oil and gas production. Nevertheless, the 2017 forecasted hazard is still significantly elevated in Oklahoma compared to the hazard calculated from seismicity before 2009.
    Print ISSN: 0895-0695
    Electronic ISSN: 1938-2057
    Topics: Geosciences
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  • 5
    Publication Date: 2015-04-15
    Description: Food intake and body weight regulation depend on proper expression of the proopiomelanocortin gene (Pomc) in a group of neurons located in the mediobasal hypothalamus of all vertebrates. These neurons release POMC-encoded melanocortins, which are potent anorexigenic neuropeptides, and their absence from mice or humans leads to hyperphagia and severe...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 6
    Publication Date: 2015-02-24
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McGarr, A -- Bekins, B -- Burkardt, N -- Dewey, J -- Earle, P -- Ellsworth, W -- Ge, S -- Hickman, S -- Holland, A -- Majer, E -- Rubinstein, J -- Sheehan, A -- New York, N.Y. -- Science. 2015 Feb 20;347(6224):830-1. doi: 10.1126/science.aaa0494.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉U.S. Geological Survey (USGS), Earthquake Science Center, Menlo Park, CA 94025, USA. mcgarr@usgs.gov. ; USGS, National Water Quality Assessment Program, Menlo Park, CA 94025, USA. ; USGS, Powell Center, Fort Collins, CO 80526, USA. ; USGS, Geologic Hazards Center, Golden, CO 80225, USA. ; U.S. Geological Survey (USGS), Earthquake Science Center, Menlo Park, CA 94025, USA. ; University of Colorado at Boulder, Boulder, CO 80302, USA. ; Oklahoma Geological Survey, Norman, OK 73069, USA. ; Lawrence Berkeley National Laboratory, Berkeley, CA, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25700505" target="_blank"〉PubMed〈/a〉
    Keywords: Disasters/*prevention & control/*statistics & numerical data ; Earthquakes/*statistics & numerical data ; Proportional Hazards Models ; Safety Management/methods ; United States ; Waste Disposal, Fluid/*methods
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 7
    Publication Date: 2016-09-28
    Description: The Mw 5.1 Fairview, Oklahoma, earthquake on February 13, 2016, and its associated seismicity produced the largest moment release in the central and eastern U.S. since the 2011 Mw 5.6 Prague, Oklahoma, earthquake sequence and is one of the largest earthquakes potentially linked to wastewater injection. This energetic sequence has produced five earthquakes with Mw 4.4 or larger. Almost all of these earthquakes occur in Precambrian basement on a partially unmapped 14-km-long fault. Regional injection into the Arbuckle formation increased approximately 7-fold in the 36 months prior to the start of the sequence (January, 2015). We suggest far-field pressurization from clustered, high-rate wells greater than 12 km from this sequence induced these earthquakes. As compared to the Fairview sequence, seismicity is diffuse near high-rate wells, where pressure changes are expected to be largest. This points to the critical role that pre-existing faults play in the occurrence of large induced earthquakes.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 7118-7125 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Conventional upper and lower bounds on the effective conductivity σe of two-phase composite media diverge from one another in the infinite-contrast limits (α=∞ or 0). We have derived a generally nontrivial upper bound on σe for suspensions of identical spheres when the spheres are superconducting, i.e., the upper bound does not necessarily become infinite in the limit α→∞. Similarly, a generally nontrivial lower bound on σe is derived for the aforementioned suspension when the spheres are perfect insulators, i.e., the lower bound does not necessarily vanish in the limit α→0. The bounds are computed for two models: simple cubic arrays and random arrays of spheres.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Annals of operations research 33 (1991), S. 481-499 
    ISSN: 1572-9338
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract Supposen points are given in the plane. Their coordinates form a 2n-vectorX. To study the question of finding the shortest Steiner networkS connecting these points, we allowX to vary over a configuration space. In particular, the Steiner ratio conjecture is well suited to this approach and short proofs of the casesn=4, 5 are discussed. The variational approach was used by us to solve other cases of the ratio conjecture (n=6, see [11] and for arbitraryn points lying on a circle). Recently, Du and Hwang have given a beautiful complete solution of the ratio conjecture, also using a configuration space approach but with convexity as the major idea. We have also solved Graham's problem to decide when the Steiner network is the same as the minimal spanning tree, for points on a circle and on any convex polygon, again using the variational method.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Algorithmica 7 (1992), S. 193-218 
    ISSN: 1432-0541
    Keywords: Graham's conjecture ; Steiner trees ; Spanning trees ; Variational approach ; Cocircular points
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Suppose a configurationX consists ofn points lying on a circle of radiusr. If at most one of the edges joining neighboring points has length strictly greater thanr, then the Steiner treeS consists of all these edges with a longest edge removed. In order to showS is, in fact, just the minimal spanning treeT, a variational approach is used to show the Steiner ratio for this configuration is at least one and equals one only ifS andT coincide. The variational approach greatly reduces the number of possible Steiner trees that need to be considered.
    Type of Medium: Electronic Resource
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