263 research outputs found
Causality violation and singularities
We show that singularities necessarily occur when a boundary of causality
violating set exists in a space-time under the physically suitable assumptions
except the global causality condition in the Hawking-Penrose singularity
theorems. Instead of the global causality condition, we impose some
restrictions on the causality violating sets to show the occurrence of
singularities.Comment: 11 pages, latex, 2 eps figure
Contribution of citizen science towards international biodiversity monitoring
To meet collective obligations towards biodiversity conservation and monitoring, it is essential that the world's governments and non-governmental organisations as well as the research community tap all possible sources of data and information, including new, fast-growing sources such as citizen science (CS), in which volunteers participate in some or all aspects of environmental assessments. Through compilation of a database on CS and community-based monitoring (CBM, a subset of CS) programs, we assess where contributions from CS and CBM are significant and where opportunities for growth exist. We use the Essential Biodiversity Variable framework to describe the range of biodiversity data needed to track progress towards global biodiversity targets, and we assess strengths and gaps in geographical and taxonomic coverage. Our results show that existing CS and CBM data particularly provide large-scale data on species distribution and population abundance, species traits such as phenology, and ecosystem function variables such as primary and secondary productivity. Only birds, Lepidoptera and plants are monitored at scale. Most CS schemes are found in Europe, North America, South Africa, India, and Australia. We then explore what can be learned from successful CS/CBM programs that would facilitate the scaling up of current efforts, how existing strengths in data coverage can be better exploited, and the strategies that could maximise the synergies between CS/CBM and other approaches for monitoring biodiversity, in particular from remote sensing. More and better targeted funding will be needed, if CS/CBM programs are to contribute further to international biodiversity monitoring
The European Approach to Privacy
This paper critically assesses the character of European (Union’s) privacy law and policy in the field of online media and electronic communications. Contrary to current understanding, this field of law is more fragmented and ill-developed than is often assumed, in particular by those discussing privacy law and policy in an international and transatlantic context. In fact, some of the most challenging regulatory issues in the field of online media and electronic communications still lack a well-developed common European approach and remain the subject of regulation at the level of the different member states of the European Union. Drawing on historic insights, the paper shows how EU policy making in the field of privacy and data protection is and remains strongly influenced by the EU institutional setting. In particular, the paper shows that the specific substantive outcome of European privacy law and policy is strongly influenced by and can only be understood properly through the lens of the ongoing project of European integration more generally. The paper will develop its main thesis by focusing on three important and current privacy issues and their treatment by EU lawmakers and the EU legal system. These are: (I.) the question of retention of communications meta-data (e.g. traffic and location data) in the field of electronic communications; (II.) the legal framework for liability of search engines for privacy and reputational harms in the online environment, including a 'right to be forgotten', and (III.) the question of the security of and the potential lawful access by foreign governments to data in the cloud. After discussing these substantive privacy policy issues and the legal frameworks that have developed (and are developing) to address them at the EU level, the paper will analyze these frameworks in view of the apparent interplay of the substance of privacy law and policy at the EU level on the one hand and the broader constitutional and institutional dynamics related to EU competency and integration. The paper starts with a discussion of the basic underlying motivations, rationales and competences for addressing privacy issues at the European level, which until recently were predominantly economic in nature. The implication of this is that some of the most pressing data privacy issues which are primarily non-economic in character, have been addressed at the fringes of what could be called the European approach to data privacy, in which the establishment of a functioning European internal market and the free flow of personal data under sufficient safeguards relating to data privacy are the dominant concerns. More recently, the adoption of the Lisbon treaty, the establishment of a binding right to data protection and privacy in the EU Charter and a new legal basis for the establishment of data protection rules at the EU level, EU privacy law and policy has become increasingly connected to the furtherance of the protection of privacy and data protection as fundamental rights more generally. Through the case studies in the paper, this dynamic of how policy rationales end up playing out at the EU level and inform the substance of privacy policies adopted, is illustrated in detail. In particular, the analysis shows how EU policy making tends to strive towards a common and comprehensive European approach, but typically fails to take account of some of the leading concerns, and is often simply not equipped or even allowed to include them in the process. For instance, there is significant disagreement about the weight that should be attributed to freedom of expression concerns in the online environment and the role of the EU with respect to media and the proper balancing of freedom and privacy in the media remains limited. With respect to national security concerns there are no European harmonization of national approaches at all. The result is that important policy concerns from the perspective of privacy in electronic communications end up being addressed indirectly, inefficiently and incompletely, through the European data privacy frameworks that may aspire to be comprehensive but would need significant reforms to achieve this aim. The article will discuss possible reforms but will warn against aspirations of further harmonization and unification of European Privacy Law. In the absence of fundamental institutional reform of the EU, further harmonization could end up being detrimental to other important policy goals currently addressed largely outside of the EU legal framework, including the issues of media freedom, criminal procedural justice and the protection of privacy and information security in relation to foreign intelligence agencies specifically discussed in this paper
Prospective risk of stillbirth and neonatal complications in twin pregnancies: systematic review and meta-analysis.
OBJECTIVE: To determine the risks of stillbirth and neonatal complications by gestational age in uncomplicated monochorionic and dichorionic twin pregnancies. DESIGN: Systematic review and meta-analysis. DATA SOURCES: Medline, Embase, and Cochrane databases (until December 2015). REVIEW METHODS: Databases were searched without language restrictions for studies of women with uncomplicated twin pregnancies that reported rates of stillbirth and neonatal outcomes at various gestational ages. Pregnancies with unclear chorionicity, monoamnionicity, and twin to twin transfusion syndrome were excluded. Meta-analyses of observational studies and cohorts nested within randomised studies were undertaken. Prospective risk of stillbirth was computed for each study at a given week of gestation and compared with the risk of neonatal death among deliveries in the same week. Gestational age specific differences in risk were estimated for stillbirths and neonatal deaths in monochorionic and dichorionic twin pregnancies after 34 weeks' gestation. RESULTS: 32 studies (29 685 dichorionic, 5486 monochorionic pregnancies) were included. In dichorionic twin pregnancies beyond 34 weeks (15 studies, 17 830 pregnancies), the prospective weekly risk of stillbirths from expectant management and the risk of neonatal death from delivery were balanced at 37 weeks' gestation (risk difference 1.2/1000, 95% confidence interval -1.3 to 3.6; I(2)=0%). Delay in delivery by a week (to 38 weeks) led to an additional 8.8 perinatal deaths per 1000 pregnancies (95% confidence interval 3.6 to 14.0/1000; I(2)=0%) compared with the previous week. In monochorionic pregnancies beyond 34 weeks (13 studies, 2149 pregnancies), there was a trend towards an increase in stillbirths compared with neonatal deaths after 36 weeks, with an additional 2.5 per 1000 perinatal deaths, which was not significant (-12.4 to 17.4/1000; I(2)=0%). The rates of neonatal morbidity showed a consistent reduction with increasing gestational age in monochorionic and dichorionic pregnancies, and admission to the neonatal intensive care unit was the commonest neonatal complication. The actual risk of stillbirth near term might be higher than reported estimates because of the policy of planned delivery in twin pregnancies. CONCLUSIONS: To minimise perinatal deaths, in uncomplicated dichorionic twin pregnancies delivery should be considered at 37 weeks' gestation; in monochorionic pregnancies delivery should be considered at 36 weeks. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42014007538
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Los Angeles megacity: a high-resolution land-atmosphere modelling system for urban CO2 emissions
Megacities are major sources of anthropogenic fossil fuel CO2 (FFCO2) emissions. The spatial extents of these large urban systems cover areas of 10 000 km2 or more with complex topography and changing landscapes. We present a high-resolution land–atmosphere modelling system for urban CO2 emissions over the Los Angeles (LA) megacity area. The Weather Research and Forecasting (WRF)-Chem model was coupled to a very high-resolution FFCO2 emission product, Hestia-LA, to simulate atmospheric CO2 concentrations across the LA megacity at spatial resolutions as fine as ∼ 1 km. We evaluated multiple WRF configurations, selecting one that minimized errors in wind speed, wind direction, and boundary layer height as evaluated by its performance against meteorological data collected during the CalNex-LA campaign (May–June 2010). Our results show no significant difference between moderate-resolution (4 km) and high-resolution (1.3 km) simulations when evaluated against surface meteorological data, but the high-resolution configurations better resolved planetary boundary layer heights and vertical gradients in the horizontal mean winds. We coupled our WRF configuration with the Vulcan 2.2 (10 km resolution) and Hestia-LA (1.3 km resolution) fossil fuel CO2 emission products to evaluate the impact of the spatial resolution of the CO2 emission products and the meteorological transport model on the representation of spatiotemporal variability in simulated atmospheric CO2 concentrations. We find that high spatial resolution in the fossil fuel CO2 emissions is more important than in the atmospheric model to capture CO2 concentration variability across the LA megacity. Finally, we present a novel approach that employs simultaneous correlations of the simulated atmospheric CO2 fields to qualitatively evaluate the greenhouse gas measurement network over the LA megacity. Spatial correlations in the atmospheric CO2 fields reflect the coverage of individual measurement sites when a statistically significant number of sites observe emissions from a specific source or location. We conclude that elevated atmospheric CO2 concentrations over the LA megacity are composed of multiple fine-scale plumes rather than a single homogenous urban dome. Furthermore, we conclude that FFCO2 emissions monitoring in the LA megacity requires FFCO2 emissions modelling with ∼ 1 km resolution because coarser-resolution emissions modelling tends to overestimate the observational constraints on the emissions estimates
Cosmological Spacetimes from Negative Tension Brane Backgrounds
We identify a time-dependent class of metrics with potential applications to
cosmology, which emerge from negative-tension branes. The cosmology is based on
a general class of solutions to Einstein-dilaton-Maxwell theory, presented in
{hep-th/0106120}. We argue that solutions with hyperbolic or planar symmetry
describe the gravitational interactions of a pair of negative-tension
-branes. These spacetimes are static near each brane, but become
time-dependent and expanding at late epoch -- in some cases asymptotically
approaching flat space. We interpret this expansion as being the spacetime's
response to the branes' presence. The time-dependent regions provide explicit
examples of cosmological spacetimes with past horizons and no past naked
singularities. The past horizons can be interpreted as S-branes. We prove that
the singularities in the static regions are repulsive to time-like geodesics,
extract a cosmological `bounce' interpretation, compute the explicit charge and
tension of the branes, analyse the classical stability of the solution (in
particular of the horizons) and study particle production, deriving a general
expression for Hawking's temperature as well as the associated entropy.Comment: 43 pages, 8 figures. Published versio
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