1,100 research outputs found
Adaptively Smoothed Seismicity Earthquake Forecasts for Italy
We present a model for estimating the probabilities of future earthquakes of
magnitudes m > 4.95 in Italy. The model, a slightly modified version of the one
proposed for California by Helmstetter et al. (2007) and Werner et al. (2010),
approximates seismicity by a spatially heterogeneous, temporally homogeneous
Poisson point process. The temporal, spatial and magnitude dimensions are
entirely decoupled. Magnitudes are independently and identically distributed
according to a tapered Gutenberg-Richter magnitude distribution. We estimated
the spatial distribution of future seismicity by smoothing the locations of
past earthquakes listed in two Italian catalogs: a short instrumental catalog
and a longer instrumental and historical catalog. The bandwidth of the adaptive
spatial kernel is estimated by optimizing the predictive power of the kernel
estimate of the spatial earthquake density in retrospective forecasts. When
available and trustworthy, we used small earthquakes m>2.95 to illuminate
active fault structures and likely future epicenters. By calibrating the model
on two catalogs of different duration to create two forecasts, we intend to
quantify the loss (or gain) of predictability incurred when only a short but
recent data record is available. Both forecasts, scaled to five and ten years,
were submitted to the Italian prospective forecasting experiment of the global
Collaboratory for the Study of Earthquake Predictability (CSEP). An earlier
forecast from the model was submitted by Helmstetter et al. (2007) to the
Regional Earthquake Likelihood Model (RELM) experiment in California, and, with
over half of the five-year experiment over, the forecast performs better than
its competitors.Comment: revised manuscript. 22 pages, 3 figures, 2 table
Furosemide Enhances the Release of Endothelial Kinsis, Nitric Oxide and Prostacyclin
Despite a wealth of data, the mechanism of the direct dilator effect of furosemide on the systemic arterial and venous systems is far from being satisfactorily understood. Therefore, we investigated whether furosemide is capable of stimulating the production of the endogenous vasodilators nitric oxide and prostacyclin in primary cultured bovine aortic endothelial cells by an enhanced synthesis and release of endothelium-derived kinins. Nitric oxide production was assessed in terms of intracellular guanosine cyclic-3',5' monophosphate accumulation; kinin and prostacyclin release were determined by specific radioimmunoassays. Furosemide concentration- and time- dependently increased the formation of nitric oxide and prostacyclin. Maximal increases of both autacoids were already obtained after a 5-min incubation with 3 x 10(-7) to 10(-6) mol/l of furosemide. In the same concentration range, furosemide led to an enhanced release of kinins into the supernatant of the cells. This observation was supported by the inhibitory effect of the specific B2 kinin receptor antagonist icatibant (Hoe 140) on the furosemide-induced increase of nitric oxide and prostacyclin. Thus the hemodynamic effects, and in particular the direct early dilator effect, of furosemide may be explained in part by an enhanced endothelial synthesis and release of bradykinin and related kinins, which in turn stimulates endothelial autacoid formation via B2 kinin receptor activation
Balancing reservoir creation and seismic hazard in enhanced geothermal systems
Fracture shear-dilatancy is an essential process for enhancing the permeability of deep geothermal reservoirs, and is usually accompanied by the radiation of seismic waves. However, the hazard and risk perspective of induced seismicity research typically focuses only on the question of how to reduce the occurrence of induced earthquakes. Here we present a quantitative analysis of seismic hazard as a function of the two key factors defining an enhanced geothermal system: The permeability enhancement, and the size of the stimulated reservoir. Our model has two coupled components: (1) a pressure diffusion model and (2) a stochastic seismicity model. Permeability is increased in the source area of each induced earthquake depending on the amount of slip, which is determined by the magnitude. We show that the few largest earthquakes (i.e. 5-10 events with M â„ 1.5) contribute more than half of the total reservoir stimulation. The results further indicate that planning and controlling of reservoir engineering operations may be compromised by the considerable variability of maximum observed magnitude, reservoir size, the Gutenberg-Richter b-value and Shapiro's seismogenic index (i.e. a measure of seismic reactivity of a reservoir) that arises from the intrinsic stochastic nature of induced seismicity. We also find that injection volume has a large impact on both reservoir size and seismic hazard. Injection rate and injection scheme have a negligible effect. The impact of site-specific parameters on seismicity and reservoir properties is greater than that of the injected volume. In particular, conditions that lead to high b-valuesâpossibly a low differential stress levelâhave a high impact on seismic hazard, but also reduce the efficiency of the stimulation in terms of permeability enhancement. Under such conditions, target reservoir permeability can still be achieved without reaching an unacceptable level of seismic hazard, if either the initial reservoir permeability is high or if several fractures are stimulated. The proposed methodology is a first step towards including induced seismic hazard analysis into the design of reservoir stimulation in a quantitative and robust manne
Magnetically Stabilized Nematic Order I: Three-Dimensional Bipartite Optical Lattices
We study magnetically stabilized nematic order for spin-one bosons in optical
lattices. We show that the Zeeman field-driven quantum transitions between
non-nematic Mott states and quantum spin nematic states in the weak hopping
limit are in the universality class of the ferromagnetic XXZ (S=1/2) spin
model. We further discuss these transitions as condensation of interacting
magnons. The development of O(2) nematic order when external fields are applied
corresponds to condensation of magnons, which breaks a U(1) symmetry.
Microscopically, this results from a coherent superposition of two non-nematic
states at each individual site. Nematic order and spin wave excitations around
critical points are studied and critical behaviors are obtained in a dilute gas
approximation. We also find that spin singlet states are unstable with respect
to quadratic Zeeman effects and Ising nematic order appears in the presence of
any finite quadratic Zeeman coupling. All discussions are carried out for
states in three dimensional bipartite lattices.Comment: 16 pages, 3 figure
Diachrony and typology of Slavic aspect: What does morphology tell us?
In this article we consider the Slavic perfective/imperfective opposition, a well-known example of viewpoint aspect which establishes a classificatory grammatical category by means of stem derivation. Although Slavic languages are not unique in having developed a classificatory aspect system, a survey of such systems shows that the Slavic perfective/imperfective opposition is a particularly rare subcase of such systems, first of all because it combines prefixing with suffixing patterns of derivation. We therefore explore the morphology involved, tracing its development from Proto-Indo-European into Early Slavic. The emergence of Slavic aspect is atypical for grammatical categories, and it deviates considerably from mainstream instances of grammaticalization in many respects. We show that there is a strong tendency (i) towards abandonment of highly lexically conditioned and versatile suffix choices in Proto-Indo-European and in Common Slavic, which led to fewer and more transparent suffixes, and (ii) towards concatenation, away from originally non-concatenative (fusional) schemata. Furthermore, we compare Slavic with some other Indo-European languages and inquire as to why in Europe no other Indo-European group beyond Slavic went so far as to productively exploit newly developed prefixes (or verb particles) merely for use as aspectual modifiers of stems and to combine them with a (partially inherited, partially remodelled) stock of suffixes to yield a classificatory aspect system. The Slavic system, thus, appears quite unique not only from a typological point of view, but also in diachronic-genealogical terms. Based on this background, amplified by some inner-Slavic biases in the productivity of patterns of stem derivation, we pose the provocative question as to whether the rise and consolidation of the stem-derivational perfective/imperfective opposition in Slavic was favoured by direct and indirect contacts with Uralic (Finno-Ugric) and Altaic (Turkic) populations at different periods since at least the time of the Great Migrations
A prospective earthquake forecast experiment in the western Pacific
Since the beginning of 2009, the Collaboratory for the Study of Earthquake Predictability (CSEP) has been conducting an earthquake forecast experiment in the western Pacific. This experiment is an extension of the KaganâJackson experiments begun 15 years earlier and is a prototype for future global earthquake predictability experiments. At the beginning of each year, seismicity models make a spatially gridded forecast of the number of Mwâ„ 5.8 earthquakes expected in the next year. For the three participating statistical models, we analyse the first two years of this experiment. We use likelihood-based metrics to evaluate the consistency of the forecasts with the observed target earthquakes and we apply measures based on Student's t-test and the Wilcoxon signed-rank test to compare the forecasts. Overall, a simple smoothed seismicity model (TripleS) performs the best, but there are some exceptions that indicate continued experiments are vital to fully understand the stability of these models, the robustness of model selection and, more generally, earthquake predictability in this region. We also estimate uncertainties in our results that are caused by uncertainties in earthquake location and seismic moment. Our uncertainty estimates are relatively small and suggest that the evaluation metrics are relatively robust. Finally, we consider the implications of our results for a global earthquake forecast experimen
Berry's Phases of Ground States of Interacting Spin-One Bosons: Chains of Monopoles and Monosegments
We study Berry's connection potentials of many-body ground states of spin-one
bosons with antiferromagnetic interactions in adiabatically varying magnetic
fields. We find that Berry's connection potentials are generally determined by,
instead of usual singular monopoles, linearly positioned monosegments each of
which carries one unit of topological charge; in the absence of a magnetic
field gradient this distribution of monosegments becomes a linear chain of
monopoles. Consequently, Berry's phases consist of a series of step functions
of magnetic fields; a magnetic field gradient causes rounding of these
step-functions. We also calculate Berry's connection fields, profiles of
monosegments and show that the total topological charge is conserved in a
parameter space
The frequency-size scaling of non-volcanic tremors beneath the San Andreas Fault at Parkfield: Possible implications for seismic energy release
© 2019 Elsevier B.V. We analyse the frequency-size-distribution of non-volcanic tremors observed along the Parkfield section of the San Andreas Fault. We suggest that these non-volcanic tremors follow a power-law scaling typical of scale-invariant, stick slip tectonic earthquakes, but with an unusually high scaling exponent of more than 2.0 and a systematic depth-dependency. While each individual non-volcanic tremor releases only a minuscule amount of energy and slip, this is more than compensated by their sheer numbers. Consequently, the integrated contribution of this largely âinvisibleâ seismicity (non-volcanic tremors and nano-earthquakes) is non-negligible and could potentially account in selected patches along the San Andreas fault for up to 100% of the plate motion
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