2,961 research outputs found
Getting that Sinking Feeling: Analysis and Impacts of Sea Level Rise on Three National Parks along the East Coast, USA
Due to global climate change, sea level rise (SLR) has become a threat for future generations, but the extent of this danger is unknown. To help understand the possible effects of SLR on the east coast of the United States, we studied three national parks: Acadia National Park (ACAD), Assateague Island National Seashore (ASIS) and Everglades National Park (EVER). We predicted that ACAD would be less affected by SLR than ASIS and EVER due to the construction of its beach profile. By measuring the beach profile, we found that Sand Beach in ACAD was reflective with an average slope of 3.2 cm/m while South Ocean Beach in ASIS had an intermediate morphology with an average slope of 1.57 cm/m. The Snake Bight Channel beach in EVER was dissipative and had no slope. Using historical Landsat imagery from 1984 to 2016, we estimated that ACAD’s water area increased by 1.61%, that ASIS’s water area increased by 2.47%, and that the EVER’s water area decreased by 0.22% between 1992 and 2011. Using RCP scenarios from the latest IPCC report, we estimated future inundation levels in each park along with the percent change between the best and worst-case scenarios. Under the RCP8.5 scenario, ACAD had 1.36 km2 of inundation, ASIS had 37.11 km2, and EVER had 366.47 km2. ACAD had the highest percent change between the worst and best RCP scenario at 15.70%. ASIS had a slightly smaller percent change at 14.25% and EVER had even less at 10.42%. This study suggests that continued SLR will cause national parks billions of dollars in property damage and the loss of their inherent ecological value
Wormholes as Black Hole Foils
We study to what extent wormholes can mimic the observational features of
black holes. It is surprisingly found that many features that could be thought
of as ``characteristic'' of a black hole (endowed with an event horizon) can be
closely mimicked by a globally static wormhole, having no event horizon. This
is the case for: the apparently irreversible accretion of matter down a hole,
no-hair properties, quasi-normal-mode ringing, and even the dissipative
properties of black hole horizons, such as a finite surface resistivity equal
to 377 Ohms. The only way to distinguish the two geometries on an
observationally reasonable time scale would be through the detection of
Hawking's radiation, which is, however, too weak to be of practical relevance
for astrophysical black holes. We point out the existence of an interesting
spectrum of quantum microstates trapped in the throat of a wormhole which could
be relevant for storing the information ``lost'' during a gravitational
collapse.Comment: 13 pages, no figures, Late
Accuracy and effectualness of closed-form, frequency-domain waveforms for non-spinning black hole binaries
The coalescences of binary black hole (BBH) systems, here taken to be
non-spinning, are among the most promising sources for gravitational wave (GW)
ground-based detectors, such as LIGO and Virgo. To detect the GW signals
emitted by BBHs, and measure the parameters of the source, one needs to have in
hand a bank of GW templates that are both effectual (for detection), and
accurate (for measurement). We study the effectualness and the accuracy of the
two types of parametrized banks of templates that are directly defined in the
frequency-domain by means of closed-form expressions, namely 'post-Newtonian'
(PN) and 'phenomenological' models. In absence of knowledge of the exact
waveforms, our study assumes as fiducial, target waveforms the ones generated
by the most accurate version of the effective one body (EOB) formalism. We find
that, for initial GW detectors the use, at each point of parameter space, of
the best closed-form template (among PN and phenomenological models) leads to
an effectualness >97% over the entire mass range and >99% in an important
fraction of parameter space; however, when considering advanced detectors, both
of the closed-form frequency-domain models fail to be effectual enough in
significant domains of the two-dimensional [total mass and mass ratio]
parameter space. Moreover, we find that, both for initial and advanced
detectors, the two closed-form frequency-domain models fail to satisfy the
minimal required accuracy standard in a very large domain of the
two-dimensional parameter space. In addition, a side result of our study is the
determination, as a function of the mass ratio, of the maximum frequency at
which a frequency-domain PN waveform can be 'joined' onto a NR-calibrated EOB
waveform without undue loss of accuracy.Comment: 29 pages, 8 figures, 1 table. Accepted for publication in Phys. Rev.
Active Jamming at Criticality
Jamming is ubiquitous in disordered systems, but the critical behavior of
jammed solids subjected to active forces or thermal fluctuations remains
elusive. In particular, while passive athermal jamming remains mean-field-like
in two and three dimensions, diverse active matter systems exhibit anomalous
scaling behavior in all physical dimensions. It is therefore natural to ask
whether activity leads to anomalous scaling in jammed systems. Here, we use
numerical and analytical methods to study systems of active, soft, frictionless
spheres in two dimensions, and elucidate the universal scaling behavior that
relates the excess coordination, active forces or temperature, and pressure
close to the athermal jammed point. We show that active forces and thermal
effects around the critical jammed state can again be captured by a mean-field
picture, thus highlighting the distinct and crucial role of amorphous structure
in active matter systems.Comment: 8 pages (4 figures) of main text + 5 pages (6 figures) of
supplementary informatio
Guide to the Identification of Poplar Cultivars on the Prairies
This paper provides those who work with poplars in the prairies region of Canada with an easy-to-use leaf and twig key and detailed morphological descriptions of the more commonly planted cultivars. Recommendations for their use, notes on growth, natural pruning, susceptibility to insects and diseases, and tolerance to climatic extremes are also provided
Tradeoffs in Community Properties Through Time in a Desert Rodent Community
Resource limitation represents an important constraint on ecological communities, which restricts the total abundance, biomass, and community energy flux a given community can support. However, the exact relationship among these three measures of biological activity remains unclear. Here we use a simple framework that links abundance and biomass with an energetic constraint. Under constant energetic availability, it is expected that changes in abundance and biomass can result from shifts in the distribution of individual masses. We test these predictions using long-term data from a desert rodent community. Total energy use for the community has not changed directionally for 25 years, but species composition has. As a result, the average body size has decreased by almost 50% and average abundance has doubled. These results lend support to the idea of resource limitation on desert rodent communities and demonstrate that systems are able to maintain community energy flux in the face of environmental change, through changes in composition and structure
Cerebrospinal Venous Obstruction: Anatomy, Clinical Presentation, Diagnosis, and Treatment of Chronic Infective Cerebrospinal Venulitis
This review chapter describes the normal anatomy and function of the cerebrospinal venous system, ultrasound diagnosis of obstructions in the system, and the clinical implications and treatment of chronic cerebrospinal venous obstruction (CCSVO) associated with chronic persistent Chlamydophila pneumoniae (Cpn) infection. The normal patterns of flow in the cerebrospinal venous system are described and guidelines for the interpretation of the extracranial duplex ultrasound (ECDU) examination of the neck veins are presented. An infective cause of CCSVO is proposed and relevant pathology tests necessary for a diagnosis of chronic persistent Cpn venulitis are discussed. A treatment protocol for Cpn chronic venulitis is described and recommended. The progress of the patient with CCSVO can then be followed and monitored by using the ECDU and relevant pathology tests after 3 and 6Â months. CCSVO is a relatively common condition encountered in chronic diseases of unknown etiology and is often neglected by medical practitioners when managing patients with symptoms of brain fog, chronic headaches, and fatigue. Objective diagnostic and treatment protocols are required to make further progress with these conditions
Categorization of species as native or nonnative using DNA sequence signatures without a complete reference library.
New genetic diagnostic approaches have greatly aided efforts to document global biodiversity and improve biosecurity. This is especially true for organismal groups in which species diversity has been underestimated historically due to difficulties associated with sampling, the lack of clear morphological characteristics, and/or limited availability of taxonomic expertise. Among these methods, DNA sequence barcoding (also known as "DNA barcoding") and by extension, meta-barcoding for biological communities, has emerged as one of the most frequently utilized methods for DNA-based species identifications. Unfortunately, the use of DNA barcoding is limited by the availability of complete reference libraries (i.e., a collection of DNA sequences from morphologically identified species), and by the fact that the vast majority of species do not have sequences present in reference databases. Such conditions are critical especially in tropical locations that are simultaneously biodiversity rich and suffer from a lack of exploration and DNA characterization by trained taxonomic specialists. To facilitate efforts to document biodiversity in regions lacking complete reference libraries, we developed a novel statistical approach that categorizes unidentified species as being either likely native or likely nonnative based solely on measures of nucleotide diversity. We demonstrate the utility of this approach by categorizing a large sample of specimens of terrestrial insects and spiders (collected as part of the Moorea BioCode project) using a generalized linear mixed model (GLMM). Using a training data set of known endemic (n = 45) and known introduced species (n = 102), we then estimated the likely native/nonnative status for 4,663 specimens representing an estimated 1,288 species (412 identified species), including both those specimens that were either unidentified or whose endemic/introduced status was uncertain. Using this approach, we were able to increase the number of categorized specimens by a factor of 4.4 (from 794 to 3,497), and the number of categorized species by a factor of 4.8 from (147 to 707) at a rate much greater than chance (77.6% accuracy). The study identifies phylogenetic signatures of both native and nonnative species and suggests several practical applications for this approach including monitoring biodiversity and facilitating biosecurity
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