bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of an Analytical Model for the Maximum Intensity of Tropical Cyclones
Authors: Bryan George H. , Rotunno Richard 
Published: May 2009

Abstract
Several studies have shown that the intensity of numerically simulated tropical cyclones can exceed (by 50%) a theoretical upper limit. To investigate the cause, this study evaluates the underlying components of Emanuel’s commonly cited analytic theory for potential intensity (herein referred to as E-PI). A review of the derivation of E-PI highlights three primary components: a dynamical component (gradient-wind and hydrostatic balance); a thermodynamical component (reversible or pseudoadiabatic thermodynamics, although the pseudoadiabatic assumption yields greater intensity); and a planetary boundary layer (PBL) closure (which relates the horizontal gradients of entropy and angular momentum at the top of the PBL to fluxes and stresses at the ocean surface). These three components are evaluated using output from an axisymmetric numerical model. The present analysis finds the thermodynamical component and the PBL closure to be sufficiently accurate for several different simulations. In contrast, the dynamical component is clearly violated. Although the balanced portion of the flow (υg, to which E-PI applies) appears to also exceed E-PI, it is shown that this difference is attributable to the method used to calculate υg from the model output. Evidence is shown that υg for a truly balanced cyclone does not exceed E-PI. To clearly quantify the impact of unbalanced flow, a more complete analytic model is presented. The model is not expressed in terms of external conditions and thus cannot be used to predict maximum intensity for a given environment; however, it does allow for evaluation of the relative contributions to maximum intensity from balanced and unbalanced (i.e., inertial) terms in the governing equations. Using numerical model output, this more complete model is shown to accurately model maximum intensity. Analysis against observations further confirms that the effects of unbalanced flow on maximum intensity are not always negligible. The contribution to intensity from unbalanced flow can become negligible in axisymmetric models as radial turbulence (i.e., viscosity) increases, and this explains why some previous studies concluded that E-PI was an accurate upper bound for their simulations. Conclusions of this study are also compared and contrasted to those from previous studies.
A Theoretical Framework for Energy and Momentum Consistency in Subgrid-Scale Parameterization for Climate Models
Authors: Shaw Tiffany A. , Shepherd Theodore G. 
Published: May 2009

Abstract
A theoretical framework for the joint conservation of energy and momentum in the parameterization of subgrid-scale processes in climate models is presented. The framework couples a hydrostatic resolved (planetary scale) flow to a nonhydrostatic subgrid-scale (mesoscale) flow. The temporal and horizontal spatial scale separation between the planetary scale and mesoscale is imposed using multiple-scale asymptotics. Energy and momentum are exchanged through subgrid-scale flux convergences of heat, pressure, and momentum. The generation and dissipation of subgrid-scale energy and momentum is understood using wave-activity conservation laws that are derived by exploiting the (mesoscale) temporal and horizontal spatial homogeneities in the planetary-scale flow. The relations between these conservation laws and the planetary-scale dynamics represent generalized nonacceleration theorems. A derived relationship between the wave-activity fluxes—which represents a generalization of the second Eliassen–Palm theorem—is key to ensuring consistency between energy and momentum conservation. The framework includes a consistent formulation of heating and entropy production due to kinetic energy dissipation.
Nonlinear Baroclinic Dynamics of Surface Cyclones Crossing a Zonal Jet
Authors: Gilet Jean-Baptiste , Plu Matthieu , Rivière Gwendal 
Published: May 2009

Abstract
Mechanisms leading a synoptic surface cyclone to cross an upper-level zonal jet and its subsequent deepening are investigated using a two-layer model on a β plane. The baroclinic interaction of a low-level circular cyclonic perturbation with an upper-level one is first studied in vertical and horizontal cyclonic or anticyclonic uniform shears. A first nonlinear effect acting on the shape and energetics of the perturbations is analyzed. If the background shear is anticyclonic, the perturbations are stretched horizontally; they lose energy barotropically but gain it baroclinically by a well-maintained westward tilt with height. Conversely, if the shear is cyclonic, perturbations remain quite isotropic, but they do not keep a favorable vertical tilt with time and the baroclinic interaction is thus only transient. The latitudinal motion of the perturbations also results from a nonlinear effect. It is found to depend strongly on the background potential vorticity (PV) gradient. This effect is a baroclinic equivalent of the so-called nonlinear barotropic “β drift” and combines the nonlinear advection and vertical stretching terms.
These results are confirmed when the anomalies are initially located south of a confined westerly jet. The poleward shift of the lower cyclonic anomaly occurs faster when the vertically averaged PV gradient is strongly positive, which happens when the jet has a large barotropic component. The lower anomaly crosses the jet from the warm to the cold side and deepens afterward. After a detailed description of this regeneration process with the help of an energy budget, it is shown that linear dynamics are not able to reproduce such behavior.
Attribution of Seasonal and Regional Changes in Arctic Moisture Convergence
Authors: Skific Natasa , Francis Jennifer A. , Cassano John J. 
Published: May 2009

Abstract
Spatial and temporal changes in high-latitude moisture convergence simulated by the National Center for Atmospheric Research Community Climate System Model, version 3 (CCSM3) are investigated. Moisture convergence is calculated using the aerological method with model fields of specific humidity and winds spanning the periods from 1960 to 1999 and 2070 to 2089. The twenty-first century incorporates the A2 scenario from the Special Report on Emissions Scenarios. The model’s realism in reproducing the twentieth-century moisture convergence is evaluated by comparison with values derived from the 40-yr ECMWF Re-Analysis (ERA-40). In the area north of 75°N, the simulated moisture convergence is similar to observations during summer, but it is larger in winter, spring, and autumn. The model also underestimates (overestimates) the mean annual moisture convergence in the eastern (western) Arctic. Late twenty-first century annual, seasonal, and regional changes are determined by applying a self-organizing map technique to the model’s sea level pressure fields to identify dominant atmospheric circulation regimes and their corresponding moisture convergence fields. Changes in moisture convergence from the twentieth to the twenty-first century result primarily from thermodynamic effects (∼70%), albeit shifts in the frequency of dominant circulation patterns exert a relatively large influence on future changes in the eastern Arctic. Increased moisture convergence in the central Arctic (North Atlantic) stems mainly from thermodynamic changes in summer (winter). Changes in the strength and location of poleward moisture gradients are most likely responsible for projected variations in moisture transport, which are in turn a consequence of increasing anthropogenic greenhouse gas emissions as prescribed by the A2 scenario.
The Interannual Stability of Cumulative Frequency Distributions for Convective System Size and Intensity
Authors: Mohr Karen I. , Molinari John , Thorncroft Chris D. 
Published: May 2009

Abstract
The characteristics of convective system populations in West Africa and the western Pacific tropical cyclone basin were analyzed to investigate whether interannual variability in convective activity in tropical continental and oceanic environments is driven by variations in the number of events during the wet season or by favoring large and/or intense convective systems. Convective systems were defined from Tropical Rainfall Measuring Mission (TRMM) data as a cluster of pixels with an 85-GHz polarization-corrected brightness temperature below 255 K and with an area of at least 64 km2. The study database consisted of convective systems in West Africa from May to September 1998–2007, and in the western Pacific from May to November 1998–2007. Annual cumulative frequency distributions for system minimum brightness temperature and system area were constructed for both regions. For both regions, there were no statistically significant differences between the annual curves for system minimum brightness temperature. There were two groups of system area curves, split by the TRMM altitude boost in 2001. Within each set, there was no statistically significant interannual variability. Subsetting the database revealed some sensitivity in distribution shape to the size of the sampling area, the length of the sample period, and the climate zone. From a regional perspective, the stability of the cumulative frequency distributions implied that the probability that a convective system would attain a particular size or intensity does not change interannually. Variability in the number of convective events appeared to be more important in determining whether a year is either wetter or drier than normal.
Toward the Use of Integral Radar Volume Descriptors for Quantitative Areal Precipitation Estimation: Results from Pseudoradar Observations
Authors: Trömel Silke , Simmer Clemens , Braun Jürgen , Gerstner Thomas , Griebel Michael 
Published: May 2009

Abstract
The central objective of this analysis is to significantly enhance the quality of radar-derived precipitation estimates by as fully as possible exploiting the information contained in the spatial and temporal variability of 3D radar volume data. The results presented are based on pseudoradar data and rain rates of a regional weather forecasting model and 12 true radiosoundings as well. Two approaches are pursued: the first approach estimates total rainfall from an individual storm over its lifetime, whereas the second approach assesses the areawide instantaneous rainfall from a multiplicity of such storms by the use of measurements of the areal coverage of the storms exceeding a threshold radar reflectivity. The concept is extended by adding more predictors to significantly enhance the rainfall estimates. The horizontal expected value and the horizontal standard deviation of enclosed reflectivities at the ground, the mean brightband fraction and its trend, the fractional area with reflectivities exceeding a threshold τ, and an orographic rainfall amplifier provide relative errors smaller than 10% in approximately 75% of the considered rain events in the first approach. In the second approach, a relative error is achieved that is below 10% in approximately 63% elements of the test set.
Parameterization of an Iceberg Drift Model in the Barents Sea
Authors: Keghouche Intissar , Bertino Laurent , Lisæter Knut Arild 
Published: May 2009

Abstract
The problem of parameter estimation is examined for an iceberg drift model of the Barents Sea. The model is forced by atmospheric reanalysis data from ECMWF and ocean and sea ice variables from the Hybrid Coordinate Ocean Model (HYCOM). The model is compared with four observed iceberg trajectories from April to July 1990. The first part of the study focuses on the forces that have the strongest impact on the iceberg trajectories, namely, the oceanic, atmospheric, and Coriolis forces. The oceanic and atmospheric form drag coefficients are optimized for three different iceberg geometries. As the iceberg mass increases, the optimal form drag coefficients increase linearly. A simple balance between the drag forces and the Coriolis force explains this behavior. The ratio between the oceanic and atmospheric form drag coefficients is similar in all experiments, although there are large uncertainties on the iceberg geometries. Two iceberg trajectory simulations have precisions better than 20 km during two months of drift. The trajectory error for the two other simulations is less than 25 km during the first month of drift but increases rapidly to over 70 km afterward. The second part of the study focuses on the sea ice parameterization. The sea ice conditions east of Svalbard in winter 1990 were too mild to exhibit any sensitivity to the sea ice parameters.
Long-Term Trend and Decadal Variability of Persistence of Daily 500-mb Geopotential Height Anomalies during Boreal Winter
Authors: Ding Ruiqiang , Li Jianping 
Published: May 2009

Abstract
An analysis has been made of the trend and decadal variability of persistence of daily 500-mb (hPa) geopotential height anomalies for the winter season. The persistence is measured based on autocorrelations at 1- and 5-day lags (denoted r1 and r5, respectively) and the effective time between independent samples T0. The results from linear trend analysis show that there exist significant trends of persistence of daily 500-mb geopotential height anomalies in some regions of the world. The regions with a significant decreasing trend are found to be mainly located at mid–high latitudes of the Northern and Southern Hemispheres, while the regions with a significant increasing trend are mainly located in the tropical Pacific Ocean. For other variables including sea level pressure (SLP), 1000-mb height, and 200-mb height, the persistence of daily anomalies also exhibits similar trends in these regions. It is speculated that the enhanced baroclinicity and advection are possibly responsible for the significant downward trend of persistence mainly occurring in the southern and northern mid–high latitudes, while the increased coupling between the atmospheric circulation and sea surface temperature (SST) could contribute to the increase of persistence in the tropical Pacific. An empirical orthogonal function (EOF) analysis based on the 7-yr Gaussian low-pass-filtered series of winter season r1 and r5 of 500-mb height (linear trend removed before the low-pass filtering) is presented. The results suggest that there is prominent decadal variability of persistence in some regions of the Northern and Southern Hemispheres and tropics. When compared with r1, r5 has decadal variations with larger magnitude and larger spatial scale. It is found that the decadal variability of persistence is closely related to decadal fluctuations of large-scale atmospheric circulation patterns.
Programmed death 1 signaling on chronic myeloid leukemia–specific T cells results in T-cell exhaustion and disease progression
Authors: Mumprecht Sabine , Schürch Christian , Schwaller Juerg , Solenthaler Max , Ochsenbein Adrian F. 
Published: May 2009

AbstractChronic myeloid leukemia (CML) is a malignant myeloproliferative disease with a characteristic chronic phase (cp) of several years before progression to blast crisis (bc). The immune system may contribute to disease control in CML. We analyzed leukemia-specific immune responses in cpCML and bcCML in a retroviral-induced murine CML model. In the presence of cpCML and bcCML expressing the glycoprotein of lymphocytic choriomeningitis virus as a model leukemia antigen, leukemia-specific cytotoxic T lymphocytes (CTLs) became exhausted. They maintained only limited cytotoxic activity, and did not produce interferon-γ or tumor necrosis factor-α or expand after restimulation. CML-specific CTLs were characterized by high expression of programmed death 1 (PD-1), whereas CML cells expressed PD-ligand 1 (PD-L1). Blocking the PD-1/PD-L1 interaction by generating bcCML in PD-1–deficient mice or by repetitive administration of αPD-L1 antibody prolonged survival. In addition, we found that PD-1 is up-regulated on CD8+ T cells from CML patients. Taken together, our results suggest that blocking the PD-1/PD-L1 interaction may restore the function of CML-specific CTLs and may represent a novel therapeutic approach for CML.
The prototype endothelial marker PAL-E is a leukocyte trafficking molecule
Authors: Keuschnigg Johannes , Henttinen Tiina , Auvinen Kaisa , Karikoski Marika , Salmi Marko , Jalkanen Sirpa 
Published: May 2009

AbstractPathologische Anatomie Leiden-endothelium antibody has been used for more than 20 years as a marker for vascular endothelium. Despite its widespread use, the target of this antibody was only recently identified as plasmalemma vesicle–associated protein-1 (PV-1). However, no function has been identified for this molecule. Here we report that activation of human umbilical vein endothelial cells with tumor necrosis factor-α resulted in a remarkable redistribution of PV-1 toward the peripheral areas of the cells. Furthermore, in vitro endpoint transmigration experiments showed that transcellularly migrating lymphocytes are surrounded by rings containing PV-1 and caveolin-1. Moreover, PV-1 associates physically with vimentin. In addition, administration of anti–PV-1 antibody during capillary flow assays resulted in a significant inhibition of lymphocyte transmigration through the endothelial cell layer, whereas rolling and adhesion were unaffected. In vivo blockage of PV-1 by an antibody in acute peritonitis and air pouch model resulted in a significant decrease in the number of migrating leukocytes. Here we thus define leukocyte transendothelial migration as the first known function for PV-1.
C/EBPα initiates primitive myelopoiesis in pluripotent embryonic cells
Authors: Chen Yaoyao , Costa Ricardo M. B. , Love Nick R. , Soto Ximena , Roth Martin , Paredes Roberto , Amaya Enrique 
Published: May 2009

AbstractThe molecular mechanisms that underlie the development of primitive myeloid cells in vertebrate embryos are not well understood. Here we characterize the role of cebpa during primitive myeloid cell development in Xenopus. We show that cebpa is one of the first known hematopoietic genes expressed in the embryo. Loss- and gain-of-function studies show that it is both necessary and sufficient for the development of functional myeloid cells. In addition, we show that cebpa misexpression leads to the precocious induction of myeloid cell markers in pluripotent prospective ectodermal cells, without the cells transitioning through a general mesodermal state. Finally, we use live imaging to show that cebpa-expressing cells exhibit many attributes of terminally differentiated myeloid cells, such as highly active migratory behavior, the ability to quickly and efficiently migrate toward wounds and phagocytose bacteria, and the ability to enter the circulation. Thus, C/EPBα is the first known single factor capable of initiating an entire myelopoiesis pathway in pluripotent cells in the embryo.
Integration of tomato reproductive developmental landmarks and expression profiles, and the effect of SUN on fruit shape
Authors: Xiao Han , Radovich Cheryll , Welty Nicholas , Hsu Jason , Li Dongmei , Meulia Tea , van der Knaap Esther 
Published: May 2009

Abstract

Background
Universally accepted landmark stages are necessary to highlight key events in plant reproductive development and to facilitate comparisons among species. Domestication and selection of tomato resulted in many varieties that differ in fruit shape and size. This diversity is useful to unravel underlying molecular and developmental mechanisms that control organ morphology and patterning. The tomato fruit shape gene SUN controls fruit elongation. The most dramatic effect of SUN on fruit shape occurs after pollination and fertilization although a detailed investigation into the timing of the fruit shape change as well as gene expression profiles during critical developmental stages has not been conducted.

Results
We provide a description of floral and fruit development in a red-fruited closely related wild relative of tomato, Solanum pimpinellifolium accession LA1589. We use established and propose new floral and fruit landmarks to present a framework for tomato developmental studies. In addition, gene expression profiles of three key stages in floral and fruit development are presented, namely floral buds 10 days before anthesis (floral landmark 7), anthesis-stage flowers (floral landmark 10 and fruit landmark 1), and 5 days post anthesis fruit (fruit landmark 3). To demonstrate the utility of the landmarks, we characterize the tomato shape gene SUN in fruit development. SUN controls fruit shape predominantly after fertilization and its effect reaches a maximum at 8 days post-anthesis coinciding with fruit landmark 4 representing the globular embryo stage of seed development. The expression profiles of the NILs that differ at sun show that only 34 genes were differentially expressed and most of them at a less than 2-fold difference.

Conclusion
The landmarks for flower and fruit development in tomato were outlined and integrated with the effect of SUN on fruit shape. Although we did not identify many genes differentially expressed in the NILs that differ at the sun locus, higher or lower transcript levels for many genes involved in phytohormone biosynthesis or signaling as well as organ identity and patterning of tomato fruit were found between developmental time points.
Head CT is of limited diagnostic value in critically ill patients who remain unresponsive after discontinuation of sedation
Authors: Balachandran Jay S , Jaleel Mairaj , Jain Manu , Mahajan Niraj , Kalhan Ravi , Balagani Rajesh , Donnelly Helen K , Greenstein Eugene , Mutlu Gökhan M 
Published: May 2009

Abstract

Background
Prolonged sedation is common in mechanically ventilated patients and is associated with increased morbidity and mortality. We sought to determine the diagnostic value of head computed tomography (CT) in mechanically ventilated patients who remain unresponsive after discontinuation of sedation.

Methods
A retrospective review of adult (age >18 years of age) patients consecutively admitted to the medical intensive care unit of a tertiary care medical center. Patients requiring mechanical ventilation for management of respiratory failure for longer than 72 hours were included in the study group. A group that did not have difficulty with awakening was included as a control.

Results
The median time after sedation was discontinued until a head CT was performed was 2 days (interquartile range 1.375–2 days). Majority (80%) of patients underwent head CT evaluation within the first 48 hours after discontinuation of sedation. Head CT was non-diagnostic in all but one patient who had a small subarachnoid hemorrhage. Twenty-five patients (60%) had a normal head CT. Head CT findings did not alter the management of any of the patients. The control group was similar to the experimental group with respect to demographics, etiology of respiratory failure and type of sedation used. However, while 37% of subjects in the control group had daily interruption of sedation, only 19% in the patient group had daily interruption of sedation (p < 0.05).

Conclusion
In patients on mechanical ventilation for at least 72 hours and who remain unresponsive after sedative discontinuation and with a non-focal neurologic examination, head CT is performed early and is of very limited diagnostic utility. Routine use of daily interruption of sedation is used in a minority of patients outside of a clinical trial setting though it may decrease the frequency of unresponsiveness from prolonged sedation and the need for head CT in patients mechanically ventilated for a prolonged period.