174 research outputs found
Long-term uncertainty quantification in WRF-modeled offshore wind resource off the US Atlantic coast
Uncertainty quantification of long-term modeled wind speed is essential to ensure stakeholders can best leverage wind resource numerical data sets. Offshore, this need is even stronger given the limited availability of observations of wind speed at heights relevant for wind energy purposes and the resulting heavier relative weight of numerical data sets for wind energy planning and operational projects. In this analysis, we consider the National Renewable Energy Laboratory's 21-year updated numerical offshore data set for the US East Coast and provide a methodological framework to leverage both floating lidar and near-surface buoy observations in the region to quantify uncertainty in the modeled hub-height wind resource. We first show how using a numerical ensemble to quantify the uncertainty in modeled wind speed is insufficient to fully capture the model deviation from real-world observations. Next, we train and validate a random forest to vertically extrapolate near-surface wind speed to hub height using the available short-term lidar data sets in the region. We then apply this model to vertically extrapolate the long-term near-surface buoy wind speed observations to hub height so that they can be directly compared to the long-term numerical data set. We find that the mean 21-year uncertainty in 140 m hourly average wind speed is slightly lower than 3 m s−1 (roughly 30 % of the mean observed wind speed) across the considered region. Atmospheric stability is strictly connected to the modeled wind speed uncertainty, with stable conditions associated with an uncertainty which is, on average, about 20 % larger than the overall mean uncertainty.</p
T2 lesion location really matters: a 10 year follow-up study in primary progressive multiple sclerosis
Objectives: Prediction of long term clinical outcome in patients with primary progressive multiple sclerosis (PPMS) using imaging has important clinical implications, but remains challenging. We aimed to determine whether spatial location of T2 and T1 brain lesions predicts clinical progression during a 10-year follow-up in PPMS.
Methods: Lesion probability maps of the T2 and T1 brain lesions were generated using the baseline scans of 80 patients with PPMS who were clinically assessed at baseline and then after 1, 2, 5 and 10 years. For each patient, the time (in years) taken before bilateral support was required to walk (time to event (TTE)) was used as a measure of progression rate. The probability of each voxel being ‘lesional’ was correlated with TTE, adjusting for age, gender, disease duration, centre and spinal cord cross sectional area, using a multiple linear regression model. To identify the best, independent predictor of progression, a Cox regression model was used.
Results: A significant correlation between a shorter TTE and a higher probability of a voxel being lesional on T2 scans was found in the bilateral corticospinal tract and superior longitudinal fasciculus, and in the right inferior fronto-occipital fasciculus (p<0.05). The best predictor of progression rate was the T2 lesion load measured along the right inferior fronto-occipital fasciculus (p=0.016, hazard ratio 1.00652, 95% CI 1.00121 to 1.01186).
Conclusion: Our results suggest that the location of T2 brain lesions in the motor and associative tracts is an important contributor to the progression of disability in PPMS, and is independent of spinal cord involvement
Threshold production in nucleon-nucleon collisions
We analyze production in nucleon-nucleon collisions near threshold
in the framework of a general model independent formalism, which can be applied
to any reaction , where , , or . Such
reactions show large isotopic effects: a large difference for - and
-collisions, which is due to the different spin structure of the
corresponding matrix elements. The analysis of the spin structure and of the
polarization observables is based on symmetry properties of the strong
interaction. Using existing experimental data on the different decays of
meson, we suggest a model for , based on
channel -exchanges. We predict polarization phenomena for the
-reaction and the ratio of cross sections for and
-collisions. For the processes we apply two
different approaches: vector meson exchange and local four-particle
interaction. In both cases we find larger -production in
-collisions, with respect to -collisions.Comment: 17 pages, 6 figure
Estimation of turbulence dissipation rate and its variability from sonic anemometer and wind Doppler lidar during the XPIA field campaign
Despite turbulence being a fundamental transport process in the boundary
layer, the capability of current numerical models to represent it is
undermined by the limits of the adopted assumptions, notably that of local
equilibrium. Here we leverage the potential of extensive observations in
determining the variability in turbulence dissipation rate (ϵ).
These observations can provide insights towards the understanding of the
scales at which the major assumption of local equilibrium between generation
and dissipation of turbulence is invalid. Typically, observations of
ϵ require time- and labor-intensive measurements from sonic and/or
hot-wire anemometers. We explore the capability of wind Doppler lidars to
provide measurements of ϵ. We refine and extend an existing method
to accommodate different atmospheric stability conditions. To validate our
approach, we estimate ϵ from four wind Doppler lidars during the
3-month XPIA campaign at the Boulder Atmospheric Observatory (Colorado), and
we assess the uncertainty of the proposed method by data intercomparison
with sonic anemometer measurements of ϵ. Our analysis of this
extensive dataset provides understanding of the climatology of turbulence
dissipation over the course of the campaign. Further, the variability in
ϵ with atmospheric stability, height, and wind speed is also
assessed. Finally, we present how ϵ increases as nocturnal
turbulence is generated during low-level jet events.</p
Near-Threshold Production of omega Mesons in the pp -> pp omega Reaction
The total cross section for omega production in the pp -> pp omega reaction
has been measured at five c.m. excess energies from 3.8 to 30 MeV. The energy
dependence is easily understood in terms of a strong proton-proton final state
interaction combined with a smearing over the width of the state. The ratio of
near-threshold phi and omega production is consistent with the predictions of a
one-pion-exchange model and the degree of violation of the OZI rule is similar
to that found in the pi-p -> n omega/phi reactions.Comment: Report in LaTeX2e. 12 pages with 2 eps figure
Optimal management of constipation associated with irritable bowel syndrome.
Irritable bowel syndrome (IBS) is a common chronic functional disorder of the gastrointestinal tract, meanly characterized by recurrent abdominal pain or discomfort and altered bowel habit. It is a complex disorder involving biological, environmental, and psychosocial factors. The diagnosis is achieved according to the Rome III criteria provided that organic causes have been excluded. Although IBS does not constitute a life-threatening condition, it has a remarkable prevalence and profoundly reduces the quality of life with burdening socioeconomic costs. One of the principal concerns about IBS is the lack of effective therapeutic options. Up to 40% of patients are not satisfied with any available medications, especially those suffering from chronic constipation. A correct management of IBS with constipation should evolve through a global approach focused on the patient, starting with careful history taking in order to assess the presence of organic diseases that might trigger the disorder. Therefore, the second step is to examine lifestyle, dietary habits, and psychological status. On these bases, a step-up management of disease is recommended: from fiber and bulking agents, to osmotic laxative drugs, to new molecules like lubiprostone and linaclotide. Although new promising tools for relief of bowel-movement-related symptoms are being discovered, a dedicated doctor\u2013patient relationship still seems to be the key for succes
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Spatial and temporal variability of turbulence dissipation rate in complex terrain
To improve parameterizations of the turbulence dissipation rate (ϵ)
in numerical weather prediction models, the temporal and spatial variability
of ϵ must be assessed. In this study, we explore influences on the
variability of ϵ at various scales in the Columbia River Gorge
during the WFIP2 field experiment between 2015 and 2017. We calculate
ϵ from five sonic anemometers all deployed in a ∼4 km2
area as well as
from two scanning Doppler lidars and four profiling
Doppler lidars, whose locations span a ∼300 km wide region.
We retrieve ϵ from the sonic anemometers using the second-order
structure function method, from the scanning lidars with the azimuth
structure function approach, and from the profiling lidars with a novel
technique using the variance of the line-of-sight velocity. The turbulence
dissipation rate shows large spatial variability, even at the microscale,
especially during nighttime stable conditions. Orographic features have a
strong impact on the variability of ϵ, with the correlation between
ϵ at different stations being highly influenced by terrain.
ϵ shows larger values in sites located downwind of complex
orographic structures or in wind farm wakes. A clear diurnal cycle in
ϵ is found, with daytime convective conditions determining values
over an order of magnitude higher than nighttime stable conditions.
ϵ also shows a distinct seasonal cycle, with differences greater
than an order of magnitude between average ϵ values in summer and
winter.</p
Spatial Guilds in the Serengeti Food Web Revealed by a Bayesian Group Model
Food webs, networks of feeding relationships among organisms, provide
fundamental insights into mechanisms that determine ecosystem stability and
persistence. Despite long-standing interest in the compartmental structure of
food webs, past network analyses of food webs have been constrained by a
standard definition of compartments, or modules, that requires many links
within compartments and few links between them. Empirical analyses have been
further limited by low-resolution data for primary producers. In this paper, we
present a Bayesian computational method for identifying group structure in food
webs using a flexible definition of a group that can describe both functional
roles and standard compartments. The Serengeti ecosystem provides an
opportunity to examine structure in a newly compiled food web that includes
species-level resolution among plants, allowing us to address whether groups in
the food web correspond to tightly-connected compartments or functional groups,
and whether network structure reflects spatial or trophic organization, or a
combination of the two. We have compiled the major mammalian and plant
components of the Serengeti food web from published literature, and we infer
its group structure using our method. We find that network structure
corresponds to spatially distinct plant groups coupled at higher trophic levels
by groups of herbivores, which are in turn coupled by carnivore groups. Thus
the group structure of the Serengeti web represents a mixture of trophic guild
structure and spatial patterns, in contrast to the standard compartments
typically identified in ecological networks. From data consisting only of nodes
and links, the group structure that emerges supports recent ideas on spatial
coupling and energy channels in ecosystems that have been proposed as important
for persistence.Comment: 28 pages, 6 figures (+ 3 supporting), 2 tables (+ 4 supporting
Experimental results on strangeness production in proton-proton collisions at COSY
The production of K+ and K- mesons in elementary proton-proton collision has
been investigated at the Cooler Synchrotron COSY in Juelich. A high quality
proton beam with low emittance and small momentum spread permitted to study the
creation of these mesons very close to the kinematical threshold. The energy
dependence of the total cross section is investigated using internal beam
facilities providing a high accuracy particle momentum determination as well as
an external non-magnetic detection setup with a large geometrical acceptance.
The determination of the four-momentum vectors for all ejectiles of each
registered event gives the complete kinematical information allowing to study
the interaction of the outgoing particles. Results on the performed studies of
the pp --> pp K+ K-, pp --> p Lambda K+ and pp --> p Sigma0 K+ reactions will
be presented and their relevance to the interpretation of heavy ion collisions
will be discussed.Comment: 8 pages, 6 figures, plenary talk at 6th International Conference On
Strange Quarks in Matter: '2001 - A Flavorspace Odyssey' (SQM2001),
Frankfurt, Germany, September 25-29, 2001, to be published in J. Phys. G:
Nucl. Part. Phy
Functional bowel disorders with diarrhoea: Clinical guidelines of the United European Gastroenterology and European Society for Neurogastroenterology and Motility
Irritable bowel syndrome with diarrhoea (IBS-D) and functional diarrhoea (FDr) are the two major functional bowel disorders characterized by diarrhoea. In spite of their high prevalence, IBS-D and FDr are associated with major uncertainties, especially regarding their optimal diagnostic work-up and management. A Delphi consensus was performed with experts from 10 European countries who conducted a literature summary and voting process on 31 statements. Quality of evidence was evaluated using the grading of recommendations, assessment, development, and evaluation criteria. Consensus (defined as >80% agreement) was reached for all the statements. The panel agreed with the potential overlapping of IBS-D and FDr. In terms of diagnosis, the consensus supports a symptom-based approach also with the exclusion of alarm symptoms, recommending the evaluation of full blood count, C-reactive protein, serology for coeliac disease, and faecal calprotectin, and consideration of diagnosing bile acid diarrhoea. Colonoscopy with random biopsies in both the right and left colon is recommended in patients older than 50 years and in presence of alarm features. Regarding treatment, a strong consensus was achieved for the use of a diet low fermentable oligo-, di-, monosaccharides and polyols, gut-directed psychological therapies, rifaximin, loperamide, and eluxadoline. A weak or conditional recommendation was achieved for antispasmodics, probiotics, tryciclic antidepressants, bile acid sequestrants, 5-hydroxytryptamine-3 antagonists (i.e. alosetron, ondansetron, or ramosetron). A multinational group of European experts summarized the current state of consensus on the definition, diagnosis, and management of IBS-D and FDr
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