936 resultados para Chance constraints
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We present high resolution transmission spectra of giant planet atmospheres from a coupled 3-D atmospheric dynamics and transmission spectrum model that includes Doppler shifts which arise from winds and planetary motion. We model jovian planets covering more than two orders of magnitude in incident flux, corresponding to planets with 0.9 to 55 day orbital periods around solar-type stars. The results of our 3-D dynamical models reveal certain aspects of high resolution transmission spectra that are not present in simple 1-D models. We find that the hottest planets experience strong substellar to anti-stellar (SSAS) winds, resulting in transmission spectra with net blue shifts of up to 3 km s−1, whereas less irradiated planets show almost no net Doppler shifts. Compared to 1-D models, peak line strengths are significantly reduced for the hottest atmospheres owing to Doppler broadening from a combination of rotation (which is faster for close-in planets under the assumption of tidal locking) and atmospheric winds. Finally, high resolution transmission spectra may be useful in studying the atmospheres of exoplanets with optically thick clouds since line cores for very strong transitions should remain optically thick to very high altitude. High resolution transmission spectra are an excellent observational test for the validity of 3-D atmospheric dynamics models, because they provide a direct probe of wind structures and heat circulation. Ground-based exoplanet spectroscopy is currently on the verge of being able to verify some of our modeling predictions, most notably the dependence of SSAS winds on insolation. We caution that interpretation of high resolution transmission spectra based on 1-D atmospheric models may be inadequate, as 3-D atmospheric motions can produce a noticeable effect on the absorption signatures.
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We develop further the effective fluid theory of stationary branes. This formalism applies to stationary blackfolds as well as to other equilibrium brane systems at finite temperature. The effective theory is described by a Lagrangian containing the information about the elastic dynamics of the brane embedding as well as the hydrodynamics of the effective fluid living on the brane. The Lagrangian is corrected order-by-order in a derivative expansion, where we take into account the dipole moment of the brane which encompasses finite-thickness corrections, including transverse spin. We describe how to extract the thermodynamics from the Lagrangian and we obtain constraints on the higher-derivative terms with one and two derivatives. These constraints follow by comparing the brane thermodynamics with the conserved currents associated with background Killing vector fields. In particular, we fix uniquely the one- and two-derivative terms describing the coupling of the transverse spin to the background space-time. Finally, we apply our formalism to two blackfold examples, the black tori and charged black rings and compare the latter to a numerically generated solution.
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We briefly review some of the lower-energy constraints to the perturbative behaviour of the strong coupling αs, with some emphasis on the determination coming from the energy between two static sources calculated on the lattice.
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We consider an effective field theory for a gauge singlet Dirac dark matter particle interacting with the standard model fields via effective operators suppressed by the scale Λ≳1 TeV. We perform a systematic analysis of the leading loop contributions to spin-independent Dirac dark matter–nucleon scattering using renormalization group evolution between Λ and the low-energy scale probed by direct detection experiments. We find that electroweak interactions induce operator mixings such that operators that are naively velocity suppressed and spin dependent can actually contribute to spin-independent scattering. This allows us to put novel constraints on Wilson coefficients that were so far poorly bounded by direct detection. Constraints from current searches are already significantly stronger than LHC bounds, and will improve in the near future. Interestingly, the loop contribution we find is isospin violating even if the underlying theory is isospin conserving.
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Nitrous oxide (N2O) is an important greenhouse gas and ozone-depleting substance that has anthropogenic as well as natural marine and terrestrial sources. The tropospheric N2O concentrations have varied substantially in the past in concert with changing climate on glacial–interglacial and millennial timescales. It is not well understood, however, how N2O emissions from marine and terrestrial sources change in response to varying environmental conditions. The distinct isotopic compositions of marine and terrestrial N2O sources can help disentangle the relative changes in marine and terrestrial N2O emissions during past climate variations. Here we present N2O concentration and isotopic data for the last deglaciation, from 16,000 to 10,000 years before present, retrieved from air bubbles trapped in polar ice at Taylor Glacier, Antarctica. With the help of our data and a box model of the N2O cycle, we find a 30 per cent increase in total N2O emissions from the late glacial to the interglacial, with terrestrial and marine emissions contributing equally to the overall increase and generally evolving in parallel over the last deglaciation, even though there is no a priori connection between the drivers of the two sources. However, we find that terrestrial emissions dominated on centennial timescales, consistent with a state-of-the-art dynamic global vegetation and land surface process model that suggests that during the last deglaciation emission changes were strongly influenced by temperature and precipitation patterns over land surfaces. The results improve our understanding of the drivers of natural N2O emissions and are consistent with the idea that natural N2O emissions will probably increase in response to anthropogenic warming.
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Mountains are among the regions most affected by climate change. The implications of climate change will reach far beyond mountain areas, as the contributions in the present publication prepared for the Conference of the Parties to the United Nations Framework Convention on Climate Change (COP 20) in Lima 2014 show. Themes discussed are water, glaciers and permafrost, hazards, biodiversity, food security and economy. The case studies included show that concrete adaptive action has been taken in many mountain areas of the world. The publication concludes with a series of recommendations for sustainable mountain development in the face of climate change.
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Chance events are considered important in career development, yet little empirical research is available on their predictors and consequences. The present study investigated socio-demographic (gender, nationality, school-type), personality (openness, locus of control) and career development variables (career decidedness, career planning) in relation to perceived chance events with a retrospective (N = 229, eleventh grade), and 1-year longitudinal prospective study (N = 245, eighth/ninth grade) among Swiss adolescents. The results showed that the majority of both groups reported a significant influence of chance events on their transition from compulsory school to vocational education or high school. Importance of chance events related to socio-demographics and personality but not career preparation. Career preparation and chance events predicted subjective career success in terms of wish correspondence and overall satisfaction with transition outcome among the younger cohort. Implications include the necessity to integrate both thorough career preparation and chance events in theory and counseling practice.
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In a world characterized by increasing pressure from financial and product markets, the question of how exogenous constraints affect internal coordination and control processes has become increasingly important. This experiment investigates how two exogenous constraints that superiors can face in budget negotiation settings, increased opportunity costs and financial pressure to meet unit targets, affect budget negotiations and subordinate effort. The results show that both constraints induce more cooperation, but in different ways. Financial pressure on the superior leads to more cooperative negotiation behavior by superiors and subordinates than increased opportunity costs. Specifically, subordinates do not take advantage of the superior's increased financial pressure to enforce lower budgets. After negotiation, both constraints strongly mitigate the negative effects of superior budget imposition on subordinate effort because exogenous constraints eliminate the effect of procedural fairness considerations on subordinate effort.
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High-precision ice core data on both atmospheric CO2 concentrations and their carbon isotopic composition (δ13Catm) provide improved constraints on the marine and terrestrial processes responsible for carbon cycle changes during the last two interglacials and the preceding glacial/interglacial transitions.
Resumo:
Presidential Address of the 2003 SPR annual meeting with commentary from the author, Former President of the SPR, Franz Caspar.