bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hospitalization for Infection and Risk of Acute Ischemic Stroke
Authors: Elkind Mitchell S.V. , Carty Cara L. , O'Meara Ellen S. , Lumley Thomas , Lefkowitz David , Kronmal Richard A. , Longstreth W.T. 
Published: May 2011

Background and Purpose—
Little is known about the acute precipitants of ischemic stroke, although evidence suggests infections contribute to risk. We hypothesized that acute hospitalization for infection is associated with the short-term risk of stroke.

Methods—
The case-crossover design was used to compare hospitalization for infection during case periods (90, 30, or 14 days before an incident ischemic stroke) and control periods (equivalent time periods exactly 1 or 2 years before stroke) in the Cardiovascular Health Study, a population-based cohort of 5888 elderly participants from 4 US sites. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated by conditional logistic regression. Confirmatory analyses assessed hazard ratios of stroke from Cox regression models, with hospitalization for infection as a time-varying exposure.

Results—
During a median follow-up of 12.2 years, 669 incident ischemic strokes were observed in participants without a baseline history of stroke. Hospitalization for infection was more likely during case than control time periods; for 90 days before stroke, OR=3.4 (95% CI, 1.8 to 6.5). The point estimates of risks were higher when we examined shorter intervals: for 30 days, OR=7.3 (95% CI, 1.9 to 40.9), and for 14 days, OR=8.0 (95% CI, 1.7 to 77.3). In survival analyses, risk of stroke was associated with hospitalization for infection in the preceding 90 days, adjusted hazard ratio=2.4 (95% CI, 1.6 to 3.4).

Conclusions—
Hospitalization for infection is associated with a short-term increased risk of stroke, with higher risks observed for shorter intervals preceding stroke.
CT Cerebral Blood Flow Maps Optimally Correlate With Admission Diffusion-Weighted Imaging in Acute Stroke but Thresholds Vary by Postprocessing Platform
Authors: Kamalian Shahmir , Kamalian Shervin , Maas Matthew B. , Goldmacher Greg V. , Payabvash Seyedmehdi , Akbar Adnan , Schaefer Pamela W. , Furie Karen L. , Gonzalez R. Gilberto , Lev Michael H. 
Published: May 2011

Background and Purpose—
Admission infarct core lesion size is an important determinant of management and outcome in acute (<9 hours) stroke. Our purposes were to: (1) determine the optimal CT perfusion parameter to define infarct core using various postprocessing platforms; and (2) establish the degree of variability in threshold values between these different platforms.

Methods—
We evaluated 48 consecutive cases with vessel occlusion and admission CT perfusion and diffusion-weighted imaging within 3 hours of each other. CT perfusion was acquired with a “second-generation” 66-second biphasic cine protocol and postprocessed using “standard” (from 2 vendors, “A-std” and “B-std”) and “delay-corrected” (from 1 vendor, “A-dc”) commercial software. Receiver operating characteristic curve analysis was performed comparing each CT perfusion parameter—both absolute and normalized to the contralateral uninvolved hemisphere—between infarcted and noninfarcted regions as defined by coregistered diffusion-weighted imaging.

Results—

Cerebral blood flow had the highest accuracy (receiver operating characteristic area under the curve) for all 3 platforms (
P
<0.01). The maximal areas under the curve for each parameter were: absolute cerebral blood flow 0.88, cerebral blood volume 0.81, and mean transit time 0.82 and relative Cerebral blood flow 0.88, cerebral blood volume 0.83, and mean transit time 0.82. Optimal receiver operating characteristic operating point thresholds varied significantly between different platforms (Friedman test,
P
<0.01).

Conclusions—
Admission absolute and normalized “second-generation” cine acquired CT cerebral blood flow lesion volumes correlate more closely with diffusion-weighted imaging-defined infarct core than do those of CT cerebral blood volume or mean transit time. Although limited availability of diffusion-weighted imaging for some patients creates impetus to develop alternative methods of estimating core, the marked variability in quantification among different postprocessing software limits generalizability of parameter map thresholds between platforms.
The Albumin in Acute Stroke Part 1 Trial
Authors: Hill Michael D. , Martin Renee H. , Palesch Yuko Y. , Tamariz Diego , Waldman Bonnie D. , Ryckborst Karla J. , Moy Claudia S. , Barsan William G. , Ginsberg Myron D. 
Published: May 2011

Background and Purpose—
The Albumin in Acute Stroke (ALIAS) Part 2 Trial is directly testing whether 2 g/kg of 25% human albumin (ALB) administered intravenously within 5 hours of ischemic stroke onset results in improved clinical outcome. Recruitment into Part 1 of the ALIAS Trial was halted for safety reasons. ALIAS Part 2 is a new, reformulated trial with more-stringent exclusion criteria. Our aim was to explore the efficacy of ALB in the ALIAS Part 1 data and to assess the statistical assumptions underlying the ALIAS Part 2 Trial.

Methods—
ALIAS is a multicenter, blinded, randomized controlled trial. Data on 434 subjects, comprising the ALIAS Part 1 subjects, were analyzed. We examined both the thrombolysis and nonthrombolysis cohorts combined and separately in a “target population” by excluding subjects who would not have been eligible for the ALIAS Part 2 Trial; the latter comprised patients >83 years of age, those with elevated baseline troponin values, and those with in-hospital stroke. We examined the differences in the primary composite outcome, defined as a modified Rankin Scale score of 0 to 1 and/or a National Institutes of Health Stroke Scale score of 0 to 1 at 90 days after randomization.

Results—
In the combined thrombolysis plus nonthrombolysis cohorts of the target population, 44.7% of subjects in the ALB group had a favorable outcome compared with 36.0% in the saline group (absolute effect size=8.7%; 95% CI, −2.2% to 19.5%). Among thrombolyzed subjects of the target population, 46.7% had a favorable outcome in the ALB group compared with 36.6% in the saline group (absolute effect size=10.1%; 95% CI, −2.0% to 20.0%).

Conclusions—
Preliminary results from the ALIAS Part 1 suggest a trend toward a favorable primary outcome in subjects treated with ALB and support the validity of the statistical assumptions that underlie the ALIAS Part 2 Trial. The ALIAS Part 2 Trial will confirm or refute these results.

Clinical Trial Registration—

URL:
http://www.clinicaltrials.gov/ALIAS
. Unique identifier: NCT00235495.
Analyzing the Sensitivity of WRF’s Single-Layer Urban Canopy Model to Parameter Uncertainty Using Advanced Monte Carlo Simulation
Authors: Wang Zhi-Hua , Bou-Zeid Elie , Au Siu Kui , Smith James A. 
Published: May 2011

AbstractSingle-layer physically based urban canopy models (UCM) have gained popularity for modeling urban–atmosphere interactions, especially the energy transport component. For a UCM to capture the physics of conductive, radiative, and turbulent advective transport of energy, it is important to provide it with an accurate parameter space, including both mesoscale meteorological forcing and microscale surface inputs. While field measurement of all input parameters to a UCM is rarely possible, understanding the model sensitivity to individual parameters is essential to determine the relative importance of parameter uncertainty for model performance. In this paper, an advanced Monte Carlo approach—namely, subset simulation—is used to quantify the impact of the uncertainty of surface input parameters on the output of an offline modified version of the Weather Research and Forecasting (WRF)-UCM. On the basis of the conditional sampling technique, the importance of surface parameters is determined in terms of their impact on critical model responses. It is found that model outputs (both critical energy fluxes and surface temperatures) are highly sensitive to uncertainties in urban geometry, whereas variations in emissivities and building interior temperatures are relatively insignificant. In addition, the sensitivity of the model to input surface parameters is also shown to be very weakly dependent on meteorological parameters. The statistical quantification of the model’s sensitivity to input parameters has practical implications, such as surface parameter calibrations in UCM and guidance for urban heat island mitigation strategies.
A Transilient Matrix for Moist Convection
Authors: Romps David M. , Kuang Zhiming 
Published: May 2011

Abstract
A method is introduced for diagnosing a transilient matrix for moist convection. This transilient matrix quantifies the nonlocal transport of air by convective eddies: for every height z, it gives the distribution of starting heights z′ for the eddies that arrive at z. In a cloud-resolving simulation of deep convection, the transilient matrix shows that two-thirds of the subcloud air convecting into the free troposphere originates from within 100 m of the surface. This finding clarifies which initial height to use when calculating convective available potential energy from soundings of the tropical troposphere.
The Summer North Atlantic Oscillation Influence on the Eastern Mediterranean
Authors: Chronis Themis , Raitsos Dionysios E. , Kassis Dimitris , Sarantopoulos Athanassios 
Published: May 2011

AbstractThis study highlights an important and previously overlooked summer North Atlantic Oscillation (NAO) influence over the eastern Mediterranean. The featured analysis is based on a synergistic use of reanalysis data, satellite retrievals, and coastal and buoy meteorological observations. The physical mechanisms at play reveal a strong summer NAO involvement on the pressure fields over northern Europe and the Anatolian plateau. Especially during August, the summer NAO modulates the Anatolian low, together with the air temperature, meridional atmospheric circulation, and cloudiness over the eastern Mediterranean. Including the dominant action centers over Greenland and the Arctic, the identified modulations rank among the strongest summer NAO-related signals over the entire Northern Hemisphere.
Persistent Atmospheric and Oceanic Anomalies in the North Atlantic from Summer 2009 to Summer 2010
Authors: Hu Zeng-Zhen , Kumar Arun , Huang Bohua , Xue Yan , Wang Wanqiu , Jha Bhaskar 
Published: May 2011

AbstractIn this work, the authors analyze the air–sea interaction processes associated with the persistent atmospheric and oceanic anomalies in the North Atlantic Ocean during summer 2009–summer 2010 with a record-breaking positive sea surface temperature anomaly (SSTA) in the hurricane Main Development Region (MDR) in the spring and summer of 2010. Contributions to the anomalies from the El Niño–Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), and a long-term trend are identified. The warming in the tropical North Atlantic during summer 2009–summer 2010 represented a typical response to ENSO, preconditioned and amplified by the influence of a strong and persistent negative phase of the NAO. The long-term trends enhanced the warming in the high and low latitudes and weakened the cooling in the midlatitudes. The persistent negative phase of the NAO was associated with active thermodynamic air–sea interaction in the North Atlantic basin. Surface wind anomalies associated with the NAO altered the ocean surface heat flux and changed the SSTA, which was likely further enhanced by the positive wind speed–evaporation–SST feedback. The total heat flux was dominated by the latent and sensible heat fluxes, while the shortwave radiation contributed to the tropical SSTA to a lesser degree. Sensitivity experiments with an atmospheric general circulation model forced by observed SST in the Atlantic Ocean alone suggested that the Atlantic SSTA, which was partly forced by the NAO, had some positive contribution to the persistence of the negative phase of the NAO. Therefore, the persistent NAO condition is partly an outcome of the global climate anomalies and the ocean–atmosphere feedback within the Atlantic basin. The combination of the ENSO, NAO, and long-term trend resulted in the record-breaking positive SSTA in the MDR in the boreal spring and summer of 2010. On the basis of the statistical relationship, the SSTA pattern in the North Atlantic was reasonably well predicted by using the preceding ENSO and NAO as predictors.
A Consistent Hybrid Variational-Smoothing Data Assimilation Method: Application to a Simple Shallow-Water Model of the Turbulent Midlatitude Ocean
Authors: Krysta Monika , Blayo Eric , Cosme Emmanuel , Verron Jacques 
Published: May 2011

Abstract
In the standard four-dimensional variational data assimilation (4D-Var) algorithm the background error covariance matrix remains static over time. It may therefore be unable to correctly take into account the information accumulated by a system into which data are gradually being assimilated.
A possible method for remedying this flaw is presented and tested in this paper. A hybrid variational-smoothing algorithm is based on a reduced-rank incremental 4D-Var. Its consistent coupling to a singular evolutive extended Kalman (SEEK) smoother ensures the evolution of the matrix. In the analysis step, a low-dimensional error covariance matrix is updated so as to take into account the increased confidence level in the state vector it describes, once the observations have been introduced into the system. In the forecast step, the basis spanning the corresponding control subspace is propagated via the tangent linear model.
The hybrid method is implemented and tested in twin experiments employing a shallow-water model. The background error covariance matrix is initialized using an EOF decomposition of a sample of model states. The quality of the analyses and the information content in the bases spanning control subspaces are also assessed. Several numerical experiments are conducted that differ with regard to the initialization of the matrix. The feasibility of the method is illustrated. Since improvement due to the hybrid method is not universal, configurations that benefit from employing it instead of the standard 4D-Var are described and an explanation of the possible reasons for this is proposed.
Evaluations of Upper-Level Turbulence Diagnostics Performance Using the Graphical Turbulence Guidance (GTG) System and Pilot Reports (PIREPs) over East Asia
Authors: Kim Jung-Hoon , Chun Hye-Yeong , Sharman Robert D. , Keller Teddie L. 
Published: May 2011

AbstractThe forecast skill of upper-level turbulence diagnostics is evaluated using available turbulence observations [viz., pilot reports (PIREPs)] over East Asia. The six years (2003–08) of PIREPs used in this study include null, light, and moderate-or-greater intensity categories. The turbulence diagnostics used are a subset of indices in the Graphical Turbulence Guidance (GTG) system. To investigate the optimal performance of the component GTG diagnostics and GTG combinations over East Asia, various statistical evaluations and sensitivity tests are performed. To examine the dependency of the GTG system on the operational numerical weather prediction (NWP) model, the GTG system is applied to both the Regional Data Assimilation and Prediction System (RDAPS) analysis data and Global Forecasting System (GFS) analysis and forecast data with 30-km and 0.3125° (T382) horizontal grid spacings. The dependency of the temporal variation in the PIREP and GFS data and the forecast lead time of the GFS-based GTG combination are also investigated. It is found that the forecasting performance of the GTG system varies with year and season according to the annual and seasonal variations in the large-scale atmospheric conditions over the East Asia region. The wintertime GTG skill is the highest, because most GTG component diagnostics are related to jet streams and upper-level fronts. The GTG skill improves as the number of PIREP samples and the vertical resolution of the underlying NWP analysis data increase, and the GTG performance decreases as the forecast lead time increases from 0 to 12 h.
Short-Time-Scale Processes in a Mature Hurricane as a Response to Sea Surface Fluctuations
Authors: Ito Kosuke , Ishikawa Yoichi , Miyamoto Yoshiaki , Awaji Toshiyuki 
Published: May 2011

Abstract
To clarify the effect of fluctuations in surface stress and heat fluxes on the intensity of a mature-state hurricane, a sensitivity analysis is performed by using a cloud-permitting nonhydrostatic axisymmetric adjoint model. The response function of our experiment is tangential velocity at the top of the boundary layer in the eyewall.
As a result of an integration backward to 4 min prior to the specified time, a dipole pattern appears in the sensitivity fields with respect to the vertical velocity, the potential temperature, and the mixing ratio of water vapor. A positive (negative) sensitivity is found in the hurricane interior (exterior) relative to the verification region. It exhibits an increase of tangential velocity 4 min after the introduction of positive (negative) perturbations in potential temperature or in the mixing ratio of water vapor in the interior (exterior). These sensitivities are not related to the changes in the central pressure field. With further backward integration, the sensitivity signals reach down to the surface and are located in the exterior region of the hurricane. While the sensitivity with respect to surface friction (heat flux) is strongly negative (positive) within a certain radius, the sensitivity can be positive (negative) beyond that radius. This means that both stronger friction and a reduction in moist air supply in the exterior region of the hurricane can serve to strengthen the maximum tangential velocity. To the authors’ knowledge, this effect has not been explained in previous studies.
The Contributions of Precipitation and Soil Moisture Observations to the Skill of Soil Moisture Estimates in a Land Data Assimilation System
Authors: Liu Qing , Reichle Rolf H. , Bindlish Rajat , Cosh Michael H. , Crow Wade T. , de Jeu Richard , De Lannoy Gabrielle J. M. , Huffman George J. , Jackson Thomas J. 
Published: May 2011

AbstractThe contributions of precipitation and soil moisture observations to soil moisture skill in a land data assimilation system are assessed. Relative to baseline estimates from the Modern Era Retrospective-analysis for Research and Applications (MERRA), the study investigates soil moisture skill derived from (i) model forcing corrections based on large-scale, gauge- and satellite-based precipitation observations and (ii) assimilation of surface soil moisture retrievals from the Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E). Soil moisture skill (defined as the anomaly time series correlation coefficient R) is assessed using in situ observations in the continental United States at 37 single-profile sites within the Soil Climate Analysis Network (SCAN) for which skillful AMSR-E retrievals are available and at 4 USDA Agricultural Research Service (“CalVal”) watersheds with high-quality distributed sensor networks that measure soil moisture at the scale of land model and satellite estimates. The average skill of AMSR-E retrievals is R = 0.42 versus SCAN and R = 0.55 versus CalVal measurements. The skill of MERRA surface and root-zone soil moisture is R = 0.43 and R = 0.47, respectively, versus SCAN measurements. MERRA surface moisture skill is R = 0.56 versus CalVal measurements. Adding information from precipitation observations increases (surface and root zone) soil moisture skills by ΔR ~ 0.06. Assimilating AMSR-E retrievals increases soil moisture skills by ΔR ~ 0.08. Adding information from both sources increases soil moisture skills by ΔR ~ 0.13, which demonstrates that precipitation corrections and assimilation of satellite soil moisture retrievals contribute important and largely independent amounts of information.
Response of Streamflow to Climate Changes in the Yellow River Basin, China
Authors: Yang Zhifeng , Liu Qiang 
Published: May 2011

AbstractClimate changes impact hydrological processes and control streamflow at the basin scale. The present study was conducted to investigate the impact of climate change on streamflow in the Yellow River basin (YRB), China. The temporal trends of streamflow were explored by the Mann–Kendall method and a linear fit model, and the relationships between streamflow, precipitation, and potential evapotranspiration (ETp) were investigated. Furthermore, the contribution of climate changes to streamflow was revealed by Budyko’s method and a simple water balance model. The following results were obtained: (i) decreasing abruptness in streamflow occurred in 1990, and this date was used to divide the streamflow into two periods (baseline period and period of change); (ii) 67 of 80 stations showed decreasing trends with an average reduction of 10.37% of annual precipitation changes, while most of the stations displayed increasing trends with a 3.71% increase in annual ETp; (iii) the precipitation and ETp elasticity of streamflow, as expected, revealed that streamflow increases with increasing precipitation, whereas it decreases with increasing ETp; and (iv) the changes of precipitation and ETp reflected complementary effects on the reduction of streamflow from the baseline period to the period of change, the decreasing trend in precipitation being the main cause for the reduction of streamflow, but the declining rates of ETp causing a slight increase in streamflow.
A History and Review of the Global Soil Wetness Project (GSWP)
Authors: Dirmeyer Paul A. 
Published: May 2011

AbstractThe Global Soil Wetness Project (GSWP) is an international land surface modeling research effort involving dataset production, validation, model comparison, and scientific investigation in the areas of land surface hydrology and climatology. GSWP is characterized by the integration of multiple land surface models on a latitude–longitude grid in a stand-alone uncoupled mode, driven by meteorological forcing data constructed by combining atmospheric analyses and gridded observed data products. The models produce time series of gridded estimates of land surface fluxes and state variables that are then studied and compared. Defining characteristics that have distinguished GSWP include its global scale, application of land surface models in the same gridded structure as they are used in weather and climate models, and the multimodel approach, which included production of a multimodel analysis in its second phase. This paper gives an overview of the history of GSWP beginning with its inception within the International Satellite Land Surface Climatology Project. Various phases of the project are described, and a review of scientific results stemming from the project is presented. Musings on future directions of research are also discussed.
On the Vanishing of the Interfacial Ekman Layer
Authors: Wirth Achim 
Published: May 2011

Abstract
It is shown that an interfacial Ekman layer between two water masses of different density vanishes in time for all Prandtl number 0 &lt; Pr &lt; ∞, demonstrating that an interfacial Ekman layer is a transient phenomena and the interface broadens in a way approaching geostrophy. For Pr = 0, undamped inertial oscillations spread away from the interface, and the case Pr = ∞ represents the classical Ekman layer.