bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficacy of a Negative Conversion Trial and Subsequent Living Donor Kidney Transplant Outcome in Recipients with a Positive Lymphocyte Crossmatch
Authors: Huh Kyu Ha , Kim Soon Il , Joo Dong Jin , Ju Man Ki , Chang Hye Kyung , Kim Hae Jin , Kim Yu Seun , Kim Myoung Soo
Published: December 2008

Background: Patients with a positive lymphocyte crossmatch (LCX) do not undergo kidney transplantation. In such patients, a negative conversion protocol consisting of intravenous immunoglobulin (IVIG), plasmapheresis, and potent immunosuppressant is one of the options for transplantation. Methods: 14 patients who showed a positive LCX with living donors underwent a trial of negative conversion between January 2002 and July 2007. Plasmapheresis was performed every other day, up to 6 times maximum. IVIG was infused after plasmapheresis, with a total dose of 500 mg/kg divided over 6 days. Kidney transplantation was performed immediately after negative conversion. Anti-thymocyte globulin (ATG) or OKT3 induction therapy was used with the combination of tacrolimus, mycophenolate mofetil, and prednisone in the perioperative period. Results: Negative conversion of LCX was achieved in 13 of 14 patients (92.9%). Transplantations were performed successfully in these 13 patients without hyperacute rejection. Four recipients developed acute rejection, which was well controlled by steroid pulse therapy. During the follow-up periods of 45.4 ± 22.0 months, all recipients except 1 showed excellent graft function. Conclusion: Selected patients with a positive LCX can undergo successful transplantation using plasmapheresis, IVIG, and potent immunosuppressants. Recipients with negative conversion of LCX showed acceptable posttransplant results.
hsCRP, sICAM-1 and TAFI in Hemodialysis Patients: Linking Inflammation and Hypofibrinolysis to Cardiovascular Events
Authors: Gad Mohamed Z. , El-Mesallamy Hala O. , Sanad Eman F.
Published: December 2008

Background/Aims: Growing evidence suggests that inflammation, oxidative stress and hypofibrinolysis may have a pivotal role in the high prevalence of cardiovascular disease (CVD) in chronic kidney disease (CKD) patients. This study aims to investigate the association of these processes with the incidence of CVD in hemodialysis (HD) patients and to examine the modulating effect of oral L-arginine in HD patients having CVD. Methods: Blood malondialdehyde (MDA), highly sensitive C-reactive protein (hsCRP), soluble intracellular adhesion molecule-1 (sICAM-1) and thrombin-activatable fibrinolysis inhibitor (TAFI) levels were measured in 12 healthy controls and in 62 CKD patients divided into 15 renal impairment, 21 HD, and 26 HD+CVD. Of the latter, 15 patients received oral L-arginine (15 g/day, 5 g t.i.d.) for 1 month. Results: MDA, hsCRP, sICAM-1 and TAFI were significantly elevated in renal impairment patients. HD and HD+CVD experienced higher levels, but only MDA and TAFI were significantly higher in HD+CVD than HD patients. Only MDA was significantly reduced by 41% after L-arginine intake. Conclusion: This study demonstrates the association of inflammation and hypofibrinolysis with hemodialysis especially in patients with CVD. We found no added therapeutic value for L-arginine at the used dose and duration to ameliorate these cascades of events.
Chronic Atrial Fibrillation Is a Biatrial Arrhythmia
Authors: Rostock Thomas , Steven Daniel , Hoffmann Boris , Servatius Helge , Drewitz Imke , Sydow Karsten , Müllerleile Kai , Ventura Rodolfo , Wegscheider Karl , Meinertz Thomas , Willems Stephan
Published: December 2008

Background—

Termination of chronic atrial fibrillation (CAF) can be achieved by catheter ablation using a stepwise approach. However, there are limited data on the contribution of the right atrium to the CAF process. Furthermore, the prognostic value of CAF termination remains unclear.

Methods and Results—

Eighty-eight patients (61�10 years of age) underwent de novo ablation of CAF in 2006 at our institution. The ablation procedure was performed sequentially in the following order: pulmonary vein isolation, defragmentation of the left atrium, coronary sinus, and right atrium. Attempted procedural end point was termination of CAF. Consecutive arrhythmias occurring after AF termination were mapped, and ablation was attempted. AF termination was achieved in 68 (77%) patients: in 37 (55%) patients it occurred in the left atrium, in 18 (26%) patients in the right atrium, and in 13 (19%) patients in the coronary sinus. In 54 patients, at least one redo was performed (total number of procedures: 154). After the first redo, another 30 patients were in sinus rhythm (total 63), 8 patients were in atrial tachycardia (AT), and 17 patients were in AF. Another 11 patients underwent a second redo. After a mean follow-up of 20�4 months, 71 (81%) patients were in sinus rhythm, 1 (1%) patient was in AT, and 16 (18%) patients were in AF. Patients with CAF termination had predominantly ATs as recurrent arrhythmias (83%), whereas those without mainly presented with recurrent CAF (85%). The overall success rate in patients with CAF termination was 95% compared with 5% of patients without CAF termination in 2 procedures (n=12). In almost all redo procedures attributable to AT, at least 1 AT during redo was documented previously.

Conclusions—

AF termination is a prognostic important end point of catheter ablation for CAF. Termination of AF was achieved in both atria and the coronary sinus, suggesting a biatrial substrate of CAF. Subsequent arrhythmias often recur during follow-up and, therefore, should be targeted for ablation.
Slow and Discontinuous Conduction Conspire in Brugada Syndrome
Authors: Postema Pieter G. , van Dessel Pascal F.H.M. , de Bakker Jacques M.T. , Dekker Lukas R.C. , Linnenbank Andre C. , Hoogendijk Mark G. , Coronel Ruben , Tijssen Jan G.P. , Wilde Arthur A.M. , Tan Hanno L.
Published: December 2008

Background—

Brugada syndrome (BrS) is associated with lethal arrhythmias, which are linked to specific ST-segment changes (type-1 BrS-ECG) and the right ventricle (RV). The pathophysiological basis of the arrhythmias and type-1 BrS-ECG is unresolved. We studied the electrophysiological characteristics of the RV endocardium in BrS.

Methods and Results—

RV endocardial electroanatomical mapping and stimulation studies were performed in controls (n=12) and BrS patients with a type-1 (BrS-1, n=10) or type-2 BrS-ECG (BrS-2, n=12) during the studies. BrS-1 patients had prominent impairment of RV endocardial impulse propagation when compared with controls, as represented by: (1) prolonged activation-duration during sinus rhythm (86�4 versus 65�3 ms), (2) increased electrogram fractionation (1.36�0.04 versus 1.15�0.01 deflections per electrogram), (3) longer electrogram duration (83�3 versus 63�2 ms), (4) activation delays on premature stimulation (longitudinal: 160�26 versus 86�9 ms; transversal: 112�5 versus 58�6 ms), and (5) abnormal transversal conduction velocity restitution (42�8 versus 18�2 ms increase in delay at shortest coupling intervals). Wider and more fractionated electrograms were also found in BrS-2 patients. Repolarization was not different between groups.

Conclusions—

BrS-1 and BrS-2 patients are characterized by wide and fractionated electrograms at the RV endocardium. BrS-1 patients display additional conduction slowing during sinus rhythm and premature stimulation along with abnormal transversal conduction velocity restitution. These patients may thus exhibit a substrate for slow and discontinuous conduction caused by abnormal active membrane processes and electric coupling. Our findings support the emerging notion that BrS is not solely attributable to abnormal electrophysiological properties but requires the conspiring effects of conduction slowing and tissue discontinuities.
Predictive Value of Myocardial Perfusion Single-Photon Emission Computed Tomography and the Impact of Renal Function on Cardiac Death
Authors: Hakeem Abdul , Bhatti Sabha , Dillie Kathryn Sullivan , Cook Jeffrey R. , Samad Zainab , Roth-Cline Michelle D. , Chang Su Min
Published: December 2008

Background—

Patients with chronic kidney disease (CKD) have worse cardiovascular outcomes than those without CKD. The prognostic utility of myocardial perfusion single-photon emission CT (MPS) in patients with varying degrees of renal dysfunction and the impact of CKD on cardiac death prediction in patients undergoing MPS have not been investigated.

Methods and Results—

We followed up 1652 consecutive patients who underwent stress MPS (32% exercise, 95% gated) for cardiac death for a mean of 2.15±0.8 years. MPS defects were defined with a summed stress score (normal summed stress score <4, abnormal summed stress score≥4). Ischemia was defined as a summed stress score ≥4 plus a summed difference score ≥2, and scar was defined as a summed difference score <2 plus a summed stress score ≥4. Renal function was calculated with the Modified Diet in Renal Disease equation. CKD (estimated glomerular filtration rate <60 mL · min
−1
· 1.73 m
−2
) was present in 36%. Cardiac death increased with worsening levels of perfusion defects across the entire spectrum of renal function. Presence of ischemia was independently predictive of cardiac death, all-cause mortality, and nonfatal myocardial infarction. Patients with normal MPS and CKD had higher unadjusted cardiac death event rates than those with no CKD and normal MPS (2.7% versus 0.8%,
P
=0.001). Multivariate Cox proportional hazards models revealed that both perfusion defects (hazard ratio 1.90, 95% CI 1.47 to 2.46) and CKD (hazard ratio 1.96, 95% CI 1.29 to 2.95) were independent predictors of cardiac death after accounting for risk factors, left ventricular dysfunction, pharmacological stress, and symptom status. Both MPS and CKD had incremental power for cardiac death prediction over baseline risk factors and left ventricular dysfunction (global χ
2
207.5 versus 169.3,
P
<0.0001).

Conclusions—

MPS provides effective risk stratification across the entire spectrum of renal function. Renal dysfunction is also an important independent predictor of cardiac death in patients undergoing MPS. Renal function and MPS have additive value in risk stratisfying patients with suspected coronary artery disease. Patients with CKD appear to have a relatively less benign prognosis than those without CKD, even in the presence of a normal scan.
Nocturnal Blood Pressure Dipping in the Hypertension of Autonomic Failure
Authors: Okamoto Luis E. , Gamboa Alfredo , Shibao Cyndya , Black Bonnie K. , Diedrich André , Raj Satish R. , Robertson David , Biaggioni Italo
Published: December 2008

Blood pressure (BP) normally decreases during the night. Absence of this phenomenon (nondipping) is associated with increased cardiovascular risk. Altered autonomic and endocrine circadian rhythms are suspected to play a role. Patients with peripheral autonomic failure offer a unique opportunity to study this phenomenon, because ≈50% develop supine hypertension despite very low autonomic function. The purpose of this study was to define the prevalence of dipping in these patients and to determine whether dipping is associated with less severe autonomic impairment or exaggerated nocturnal sodium excretion. We collected BP and urine from 8:00
pm
to 8:00
am
in 41 peripheral autonomic failure patients with supine hypertension. Dipping (systolic BP fall ≥10% during 12
am
to 6
am
from baseline [8
pm
to 10
pm
]) occurred in 34% of patients, with an average decrease of −44±4 mm Hg at 4
am
. Systolic BP, averaged from 12
am
to 6
am
, decreased to normotensive levels in 50% (n=7) of dippers and 15% (n=7) of nondippers. There were no significant differences in the severity of autonomic failure, nocturnal diuresis, or natriuresis (0.18±0.01 in dippers versus 0.18±0.01 mEq/mg of creatinine in nondippers;
P
=0.522) between groups. At 8:00
am
, orthostatic hypotension was similar between groups (−84/−35±9/4 mm Hg in dippers versus −93/−39±6/3 mm Hg in nondippers;
P
=0.356 for systolic BP). In conclusion, dipping was observed in one third of patients with peripheral autonomic failure, so that a significant percentage of patients would not require treatment for supine hypertension. Dipping was not associated with increased nocturnal urinary sodium or volume excretion or less severe autonomic failure. Thus, mechanisms independent of autonomic pathways contribute to BP dipping in these patients.
Human Body Pose Estimation with Particle Swarm Optimisation
Authors: Ivekovič Špela , Trucco Emanuele , Petillot Yvan R.
Published: December 2008

In this paper we address the problem of human body pose estimation from still images. A multi-view set of images of a person sitting at a table is acquired and the pose estimated. Reliable and efficient pose estimation from still images represents an important part of more complex algorithms, such as tracking human body pose in a video sequence, where it can be used to automatically initialise the tracker on the first frame. The quality of the initialisation influences the performance of the tracker in the subsequent frames. We formulate the body pose estimation as an analysis-by-synthesis optimisation algorithm, where a generic 3D human body model is used to illustrate the pose and the silhouettes extracted from the images are used as constraints. A simple test with gradient descent optimisation run from randomly selected initial positions in the search space shows that a more powerful optimisation method is required. We investigate the suitability of the Particle Swarm Optimisation (PSO) for solving this problem and compare its performance with an equivalent algorithm using Simulated Annealing (SA). Our tests show that the PSO outperforms the SA in terms of accuracy and consistency of the results, as well as speed of convergence.
Effect of Turbulence Models and Spatial Resolution on Resolved Velocity Structure and Momentum Fluxes in Large-Eddy Simulations of Neutral Boundary Layer Flow
Authors: Ludwig Francis L. , Chow Fotini Katopodes , Street Robert L.
Published: December 2008

This paper demonstrates the importance of high-quality subfilter-scale turbulence models in large-eddy simulations by evaluating the resolved-scale flow features that result from various closure models. The Advanced Regional Prediction System (ARPS) model was used to simulate neutral flow over a 1.2-km square, flat, rough surface with seven subfilter turbulence models [Smagorinsky, turbulent kinetic energy (TKE)-1.5, and five dynamic reconstruction combinations]. These turbulence models were previously compared with similarity theory. Here, the differences are evaluated using mean velocity statistics and the spatial structure of the flow field. Streamwise velocity averages generally differ among models by less than 0.5 m s−1, but those differences are often significant at a 95% confidence level. Flow features vary considerably among models. As measured by spatial correlation, resolved flow features grow larger and less elongated with height for a given model and resolution. The largest differences are between dynamic models that allow energy backscatter from small to large scales and the simple eddy-viscosity closures. At low altitudes, the linear extent of Smagorinsky and TKE-1.5 structures exceeds those of dynamic models, but the relationship reverses at higher altitudes. Ejection, sweep, and upward momentum flux features differ among models and from observed neutral atmospheric flows, especially for Smagorinsky and TKE-1.5 coarse-grid simulations. Near-surface isopleths separating upward fluxes from downward are shortest for the Smagorinsky and TKE-1.5 coarse-grid simulations, indicating less convoluted turbulent interfaces; at higher altitudes they are longest. Large-eddy simulation (LES) is a powerful simulation tool, but choices of grid resolution and subfilter model can affect results significantly. Physically realistic dynamic mixed models, such as those presented here, are essential when using LES to study atmospheric processes such as transport and dispersion—in particular at coarse resolutions.
Assessing the Relative Performance of Microwave-Based Satellite Rain-Rate Retrievals Using TRMM Ground Validation Data
Authors: Wolff David B. , Fisher Brad L.
Published: December 2008

Spaceborne microwave sensors provide critical rain information used in several global multisatellite rain products, which in turn are used for a variety of important studies, including landslide forecasting, flash flood warning, data assimilation, climate studies, and validation of model forecasts of precipitation. This study employs 4 yr (2003–06) of satellite data to assess the relative performance and skill of the Special Sensor Microwave Imager [SSM/I (F13, F14, and F15], Advanced Microwave Sounding Unit [AMSU-B (N15, N16, and N17)], Advanced Microwave Scanning Radiometer for Earth Observing System [AMSR-E (Aqua)], and the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) in estimating surface rainfall based on direct instantaneous comparisons with ground-based rain estimates from the TRMM Ground Validation (GV) sites at Kwajalein, Republic of the Marshall Islands (KWAJ), and Melbourne, Florida (MELB). The relative performance of each of these satellite estimates is examined via comparisons with space- and time-coincident GV radar-based rain-rate estimates. Because underlying surface terrain is known to affect the relative performance of the satellite algorithms, the data for MELB were further stratified into ocean, land, and coast categories using a 0.25° terrain mask. Of all the satellite estimates compared in this study, TMI and AMSR-E exhibited considerably higher correlations and skills in estimating–observing surface precipitation. While SSM/I and AMSU-B exhibited lower correlations and skills for each of the different terrain categories, the SSM/I absolute biases trended slightly lower than AMSR-E over ocean, where the observations from both emission and scattering channels were used in the retrievals. AMSU-B exhibited the least skill relative to GV in all of the relevant statistical categories, and an anomalous spike was observed in the probability distribution functions near 1.0 mm h−1. This statistical artifact appears to be related to attempts by algorithm developers to include some lighter rain rates, not easily detectable by its scatter-only frequencies. AMSU-B, however, agreed well with GV when the matching data were analyzed on monthly scales. These results signal to developers of global rainfall products, such as the TRMM Multisatellite Precipitation Analysis (TMPA) and the Climate Data Center’s Morphing (CMORPH) technique, that care must be taken when incorporating data from these input satellite estimates to provide the highest-quality estimates in their products.
Mechanisms for Quasi-Stationary Behavior in Simulated Heavy-Rain-Producing Convective Systems
Authors: Schumacher Russ S.
Published: December 2008

In this study, idealized numerical simulations are used to identify the processes responsible for initiating, organizing, and maintaining quasi-stationary convective systems that produce locally extreme rainfall amounts. Of particular interest are those convective systems that have been observed to occur near mesoscale convective vortices (MCVs) and other midlevel circulations. To simulate the lifting associated with such circulations, a low-level momentum forcing is applied to an initial state that is representative of observed extreme rain events. The initial vertical wind profile includes a sharp reversal of the vertical wind shear with height, indicative of observed low-level jets.

Deep moist convection initiates within the region of mesoscale lifting, and the resulting convective system replicates many of the features of observed systems. The low-level thermodynamic environment is nearly saturated, which is not conducive to the production of a strong surface cold pool; yet the convection quickly organizes into a back-building line. It is shown that a nearly stationary convectively generated low-level gravity wave is responsible for the linear organization, which continues for several hours. New convective cells repeatedly form on the southwest end of the line and move to the northeast, resulting in large local rainfall amounts. In the later stages of the simulated convective system, a cold pool does develop, but its interaction with the strong reverse shear at low levels is not optimized for the maintenance of deep convection along its edge. A series of sensitivity experiments shows some of the effects of hydrometeor evaporation and melting, planetary rotation, and the imposed mesoscale forcing.
Attribution of the Seasonality and Regionality in Climate Trends over the United States during 1950–2000
Authors: Wang Hailan , Schubert Siegfried , Suarez Max , Chen Junye , Hoerling Martin , Kumar Arun , Pegion Philip
Published: December 2008

The observed climate trends over the United States during 1950–2000 exhibit distinct seasonality and regionality. The surface air temperature exhibits a warming trend during winter, spring, and early summer and a modest countrywide cooling trend in late summer and fall, with the strongest warming occurring over the northern United States in spring. Precipitation trends are positive in all seasons, with the largest trend occurring over the central and southern United States in fall. This study investigates the causes of the seasonality and regionality of those trends, with a focus on the cooling and wetting trends in the central United States during late summer and fall. In particular, the authors examine the link between the seasonality and regionality of the climate trends over the United States and the leading patterns of sea surface temperature (SST) variability, including a global warming (GW) pattern and a Pacific decadal variability (PDV) pattern.

A series of idealized atmospheric general circulation model (AGCM) experiments were performed forced by SST trends associated with these leading SST patterns, as well as the residual trend pattern (obtained by removing the GW and PDV contributions). The results show that the observed seasonal and spatial variations of the climate trends over the United States are to a large extent explained by changes in SST. Among the leading patterns of SST variability, the PDV pattern plays a prominent role in producing both the seasonality and regionality of the climate trends over the United States. In particular, it is the main contributor to the apparent cooling and wetting trends over the central United States. The residual SST trend, a manifestation of phase changes of the Atlantic multidecadal SST variation during 1950–2000, also exerts influences that show strong seasonality with important contributions to the central U.S. temperature and precipitation during the summer and fall seasons. In contrast, the response over the United States to the GW SST pattern is an overall warming with little seasonality or regional variation. These results highlight the important contributions of decadal and multidecadal variability in the Pacific and Atlantic in explaining the observed seasonality and regionality of the climate trends over the United States during the period of 1950–2000.
Understanding Recent Stratospheric Climate Change
Authors: Thompson David W. J. , Solomon Susan
Published: December 2008

The long-term, global-mean cooling of the lower stratosphere stems from two downward steps in temperature, both of which are coincident with the cessation of transient warming after the volcanic eruptions of El Chichón and Mount Pinatubo. Previous attribution studies reveal that the long-term cooling is linked to ozone trends, and modeling studies driven by a range of known forcings suggest that the steps reflect the superposition of the long-term cooling with transient variability in upwelling longwave radiation from the troposphere. However, the long-term cooling of the lower stratosphere is evident at all latitudes despite the fact that chemical ozone losses are thought to be greatest at middle and polar latitudes. Further, the ozone concentrations used in such studies are based on either 1) smooth mathematical functions fit to sparsely sampled observations that are unavailable during postvolcanic periods or 2) calculations by a coupled chemistry–climate model.

Here the authors provide observational analyses that yield new insight into three key aspects of recent stratospheric climate change. First, evidence is provided that shows the unusual steplike behavior of global-mean stratospheric temperatures is dependent not only upon the trend but also on the temporal variability in global-mean ozone immediately following volcanic eruptions. Second, the authors argue that the warming/cooling pattern in global-mean temperatures following major volcanic eruptions is consistent with the competing radiative and chemical effects of volcanic eruptions on stratospheric temperature and ozone. Third, it is revealed that the contrasting latitudinal structures of recent stratospheric temperature and ozone trends are consistent with large-scale increases in the stratospheric overturning Brewer–Dobson circulation.
“Modes of Variability” and Climate Change
Authors: Branstator Grant , Selten Frank
Published: December 2008

A 62-member ensemble of coupled general circulation model (GCM) simulations of the years 1940–2080, including the effects of projected greenhouse gas increases, is examined. The focus is on the interplay between the trend in the Northern Hemisphere December–February (DJF) mean state and the intrinsic modes of variability of the model atmosphere as given by the upper-tropospheric meridional wind. The structure of the leading modes and the trend are similar. Two commonly proposed explanations for this similarity are considered.

Several results suggest that this similarity in most respects is consistent with an explanation involving patterns that result from the model dynamics being well approximated by a linear system. Specifically, the leading intrinsic modes are similar to the leading modes of a stochastic model linearized about the mean state of the GCM atmosphere, trends in GCM tropical precipitation appear to excite the leading linear pattern, and the probability density functions (PDFs) of prominent circulation patterns are quasi-Gaussian.

There are, on the other hand, some subtle indications that an explanation for the similarity involving preferred states (which necessarily result from nonlinear influences) has some relevance. For example, though unimodal, PDFs of prominent patterns have departures from Gaussianity that are suggestive of a mixture of two Gaussian components. And there is some evidence of a shift in probability between the two components as the climate changes. Interestingly, contrary to the most prominent theory of the influence of nonlinearly produced preferred states on climate change, the centroids of the components also change as the climate changes. This modification of the system’s preferred states corresponds to a change in the structure of its dominant patterns. The change in pattern structure is reproduced by the linear stochastic model when its basic state is modified to correspond to the trend in the general circulation model’s mean atmospheric state. Thus, there is a two-way interaction between the trend and the modes of variability.
Impact of Resolution on the Tropical Pacific Circulation in a Matrix of Coupled Models
Authors: Roberts Malcolm J. , Clayton A. , Demory M.-E. , Donners J. , Vidale P. L. , Norton W. , Shaffrey L. , Stevens D. P. , Stevens I. , Wood R. A. , Slingo J.
Published: December 2008

Results are presented from a matrix of coupled model integrations, using atmosphere resolutions of 135 and 90 km, and ocean resolutions of 1° and 1/3°, to study the impact of resolution on simulated climate. The mean state of the tropical Pacific is found to be improved in the models with a higher ocean resolution. Such an improved mean state arises from the development of tropical instability waves, which are poorly resolved at low resolution; these waves reduce the equatorial cold tongue bias. The improved ocean state also allows for a better simulation of the atmospheric Walker circulation.

Several sensitivity studies have been performed to further understand the processes involved in the different component models. Significantly decreasing the horizontal momentum dissipation in the coupled model with the lower-resolution ocean has benefits for the mean tropical Pacific climate, but decreases model stability. Increasing the momentum dissipation in the coupled model with the higher-resolution ocean degrades the simulation toward that of the lower-resolution ocean.

These results suggest that enhanced ocean model resolution can have important benefits for the climatology of both the atmosphere and ocean components of the coupled model, and that some of these benefits may be achievable at lower ocean resolution, if the model formulation allows.
Equilibrium Climate Sensitivity: Is It Accurate to Use a Slab Ocean Model?
Authors: Danabasoglu Gokhan , Gent Peter R.
Published: December 2008

The equilibrium climate sensitivity of a climate model is usually defined as the globally averaged equilibrium surface temperature response to a doubling of carbon dioxide. This is virtually always estimated in a version with a slab model for the upper ocean. The question is whether this estimate is accurate for the full climate model version, which includes a full-depth ocean component. This question has been answered for the low-resolution version of the Community Climate System Model, version 3 (CCSM3). The answer is that the equilibrium climate sensitivity using the full-depth ocean model is 0.14°C higher than that using the slab ocean model, which is a small increase. In addition, these sensitivity estimates have a standard deviation of nearly 0.1°C because of interannual variability. These results indicate that the standard practice of using a slab ocean model does give a good estimate of the equilibrium climate sensitivity of the full CCSM3. Another question addressed is whether the effective climate sensitivity is an accurate estimate of the equilibrium climate sensitivity. Again the answer is yes, provided that at least 150 yr of data from the doubled carbon dioxide run are used.
Assessing the Impacts of Global Warming on Snowpack in the Washington Cascades*
Authors: Casola Joseph H. , Cuo Lan , Livneh Ben , Lettenmaier Dennis P. , Stoelinga Mark T. , Mote Philip W. , Wallace John M.
Published: December 2008

The decrease in mountain snowpack associated with global warming is difficult to estimate in the presence of the large year-to-year natural variability in observations of snow-water equivalent (SWE). A more robust approach for inferring the impacts of global warming is to estimate the temperature sensitivity (λ) of spring snowpack and multiply it by putative past and future temperature rises observed across the Northern Hemisphere.

Estimates of λ can be obtained from (i) simple geometric considerations based on the notion that as the seasonal-mean temperature rises by the amount δT, the freezing level and the entire snowpack should rise by the increment δT/Γ, where Γ is the mean lapse rate; (ii) the regression of 1 April SWE measurements upon mean winter temperatures; (iii) a hydrological model forced by daily temperature and precipitation observations; and (iv) the use of inferred accumulated snowfall derived from daily temperature and precipitation data as a proxy for SWE. All four methods yield an estimated sensitivity of 20% of spring snowpack lost per degree Celsius temperature rise. The increase of precipitation accompanying a 1°C warming can be expected to decrease the sensitivity to 16%.

Considering observations of temperature rise over the Northern Hemisphere, it is estimated that spring snow-water equivalent in the Cascades portion of the Puget Sound drainage basin should have declined by 8%–16% over the past 30 yr resulting from global warming, and it can be expected to decline by another 11%–21% by 2050. These losses would be statistically undetectable from a trend analysis of the region’s snowpack over the past 30 yr.
Scattering of Internal Waves with Frequency Change over Rough Topography
Authors: Nakamura Tomohiro , Awaji Toshiyuki
Published: December 2008

The frequency change in internal gravity waves upon scattering from a rough topography is investigated analytically. For this, sets of appropriate and tractable governing equations for various parameter regimes are derived using the method of multiple scales under the assumption that the amplitude of the bottom topography is small. A solution is shown for a simple case in which an incident internal wave is approximately linear and monochromatic. The solution has the following features: the intrinsic frequencies of the scattered waves are given as the sum and difference of the incident-wave frequency and the Doppler shift (or lee-wave frequency). This Doppler shift causes the change in the frequency. Hence, the assumption of frequency conservation is not valid if the Doppler shift is significant, that is, when the horizontal scale of the bottom roughness (or the length scale in the plane of the slope) is on the order of or much less than that of the incident-wave flow excursion. This condition can be satisfied in a realistic parameter range.

The occurrence of such a frequency change has the following implications: first, it affects the estimate of the boundary mixing induced by the scattering because the energy redistribution in the vertical wavenumber space on scattering differs from that estimated using the assumption of frequency conservation. This effect happens because for a given horizontal wavenumber, the change in the frequency alters the vertical wavenumber of the scattered waves through the dispersion relation. Furthermore, if the incident waves are not monochromatic, even the leading-order scattered waves cannot be obtained by the superposition of the solutions for all the Fourier components of the incident waves because of the difference in the Doppler shift. Second, the effects of the background flow associated with the incident and primary reflected waves are significant when the frequency change occurs such that the background flow can create a critical level and/or advect scattered waves. The former causes mixing and background-flow acceleration, and the latter is favorable for the amplification of the scattered waves through superposition. Third, the resulting energy redistribution in frequency space could modify the spectrum shape of the oceanic internal waves, which is considered to affect both interior and boundary mixing.
Interannual and Decadal Variations in Cross-Shelf Transport in the Gulf of Alaska
Authors: Combes Vincent , Di Lorenzo Emanuele , Curchitser Enrique
Published: December 2008

The marine ecosystem of the Gulf of Alaska (GOA) is one of the richest on the planet. The center of the GOA is characterized by high-nutrient and low-chlorophyll-a concentration. Recent observational studies suggest that advection of iron-rich coastal water is the primary mechanism controlling open ocean productivity. Specifically, there is evidence that mesoscale eddies along the coastal GOA entrain iron-rich coastal waters into the ocean interior. This study investigates the cross-shelf transport statistics in the GOA using a free-surface, hydrostatic, eddy-resolving primitive equation model over the period 1965–2004. The statistics of coastal water transport are computed using a model passive tracer, which is continuously released at the coast. The passive tracer can thus be considered a proxy for coastal biogeochemical quantities such as silicate, nitrate, iron, or oxygen, which are critical for explaining the GOA ecosystem dynamics. On average along the Alaska Current, it has been shown that at the surface while the advection of tracers by the average flow is directed toward the coast consistent with the dominant downwelling regime of the GOA, it is the mean eddy fluxes that contribute to offshore advection into the gyre interior. South of the Alaskan Peninsula, both the advection of tracers by the average flow and the mean eddy fluxes contribute to the mean offshore advection. On interannual and longer time scales, the offshore transport of the passive tracer in the Alaskan Stream does not correlate with large-scale atmospheric forcing, nor with local winds. In contrast in the Alaska Current region, stronger offshore transport of the passive tracer coincides with periods of stronger downwelling (in particular during positive phases of the Pacific decadal oscillation), which trigger the development of stronger eddies.
Water Vapor Profiling Using a Widely Tunable, Amplified Diode-Laser-Based Differential Absorption Lidar (DIAL)
Authors: Nehrir Amin R. , Repasky Kevin S. , Carlsten John L. , Obland Michael D. , Shaw Joseph A.
Published: December 2008

A differential absorption lidar (DIAL) instrument for automated profiling of water vapor in the lower troposphere has been designed, tested, and is in routine operation at Montana State University. The laser transmitter for the DIAL instrument uses a widely tunable external cavity diode laser (ECDL) to injection seed two cascaded semiconductor optical amplifiers (SOAs) to produce a laser transmitter that accesses the 824–841-nm spectral range. The DIAL receiver utilizes a 28-cm-diameter Schmidt–Cassegrain telescope; an avalanche photodiode (APD) detector; and a narrowband optical filter to collect, discriminate, and measure the scattered light. A technique of correcting for the wavelength-dependent incident angle upon the narrowband optical filter as a function of range has been developed to allow accurate water vapor profiles to be measured down to 225 m above the surface. Data comparisons using the DIAL instrument and collocated radiosonde measurements are presented demonstrating the capabilities of the DIAL instrument.
A Multicase Comparative Assessment of the Ensemble Kalman Filter for Assimilation of Radar Observations. Part I: Storm-Scale Analyses
Authors: Aksoy Altuğ , Dowell David C. , Snyder Chris
Published: December 2008

The effectiveness of the ensemble Kalman filter (EnKF) for assimilating radar observations at convective scales is investigated for cases whose behaviors span supercellular, linear, and multicellular organization. The parallel EnKF algorithm of the Data Assimilation Research Testbed (DART) is used for data assimilation, while the Weather Research and Forecasting (WRF) Model is employed as a simplified cloud model at 2-km horizontal grid spacing. In each case, reflectivity and radial velocity measurements are utilized from a single Weather Surveillance Radar-1988 Doppler (WSR-88D) within the U.S. operational network. Observations are assimilated every 2 min for a duration of 60 min and correction of folded radial velocities occurs within the EnKF. Initial ensemble uncertainty includes random perturbations to the horizontal wind components of the initial environmental sounding. The EnKF performs effectively and with robust results across all the cases. Over the first 18–30 min of assimilation, the rms and domain-averaged prior fits to observations in each case improve significantly from their initial levels, reaching comparable values of 3–6 m s−1 and 7–10 dBZ. Representation of mesoscale uncertainty, albeit in the simplest form of initial sounding perturbations, is a critical part of the assimilation system, as it increases ensemble spread and improves filter performance. In addition, assimilation of “no precipitation” observations (i.e., reflectivity observations with values small enough to indicate the absence of precipitation) serves to suppress spurious convection in ensemble members. At the same time, it is clear that the assimilation is far from optimal, as the ensemble spread is consistently smaller than what would be expected from the innovation statistics and the assumed observation-error variance.
Medium Lead-Time Predictability of Intraseasonal Variability of Rainfall in West Africa
Authors: Sultan Benjamin , Janicot Serge , Correia Cyrille
Published: December 2008

The variability of the West African monsoon on the intraseasonal time scale is a major issue for agricultural strategy, as the occurrence of dry spells can strongly impact yields of rain-fed crops. This study investigates this intraseasonal variability of rainfall over West Africa and gives a first overview of its predictability at a medium lead time.

A statistical method, the singular spectrum analysis, is applied to a ground-based rainfall index in West Africa to describe first temporal patterns of the main leading modes of intraseasonal variability. The results point out the existence of one oscillatory mode of 34 days, one of 20 days, and one of 14 days. The same methodology is applied to rainfall from two reanalysis datasets and to deep convection from satellite data in order to assess the accuracy of the representation of intraseasonal variability in these datasets. It is shown that although the day-to-day variability of rainfall is not well captured in these datasets, intraseasonal features and, in particular, the low-frequency mode are very well reproduced.

The medium lead-time predictability (5–10 days) of the intraseasonal modes is investigated using both the dynamical forecast scheme of the ECMWF and a statistical method, the maximum entropy method. For the latter method, an operational application using unfiltered input data is also considered. The performance of these prediction schemes is compared using a simple reference technique in which forecasts are based entirely on persistence. It is found that statistical predictions are much more promising than the dynamical ones, though they encounter problems when applied operationally. In an operational application, the forecast skill for the 10–90-day intraseasonal band is low but the predictability of individual intraseasonal modes is higher. The stability of the forecast skill levels is influenced by the characteristics of the intraseasonal mode. When the characteristics (i.e., amplitude and period) of the considered intraseasonal mode are well defined, skillful forecasts can be obtained. However, when the characteristics change rapidly, the forecast fails.
Association between Carotid and Coronary Artery Disease in Patients with Aortic Valve Stenosis: An Angiographic Study
Authors: Antonini-Canterin Francesco , Leiballi Elisa , Capanna Michele , Burelli Claudio , Cassin Matteo , Macor Franco , Grandis Umberto , Nicolosi Gian Luigi
Published: December 2008

Background

Patients with aortic stenosis have a high prevalence of coronary artery disease, but there is little information about the association of coronary artery disease and carotid artery disease.

Methods

The study includes 317 consecutive patients with aortic stenosis, who underwent carotid and coronary angiography during the same catheterization before aortic valve replacement.

Results

At univariate analysis, the prevalence of coronary artery disease was associated with (1) presence of carotid artery disease ( P < .001); (2) angina pectoris as presentation symptom ( P < .001); (3) age more than 65 years ( P < .05); and (4) hypertension ( P < .05). At multivariate analysis, only carotid artery disease, angina, and age emerged as independent predictors of coronary artery disease. The combination of 2 variables (carotid artery disease, angina) allowed the identification of 4 groups, with decreasing prevalence of coronary artery disease: (1) angina+/carotid artery disease+: 85%; (2) angina—/ carotid artery disease+: 50%; (3) angina+/carotid artery disease—: 41%; (4) angina—/carotid artery disease—: 21% ( P < .001).

Conclusion

In patients with symptomatic aortic stenosis, the presence of significant carotid artery disease is a strong marker of significant coronary artery disease.
From Pulp to Fiction?
Authors: Pakkasvirta Jussi
Published: December 2008

The pulp mill conflict between Argentina and Uruguay is a topical environmental local—global dispute including various time—space levels (local—regional—national—global). It is also a politico-economic battle among business, civil society and governments in the two South American countries. This article highlights the widely analysed Argentine and Uruguayan perspectives, but it also brings to the fore the Finnish case (of mass media, the global Finnish paper industry, Finnish NGOs and the government). The article seeks to come to an understanding of the characteristics of the conflict as portrayed by the media in Finland and, critically, to examine the effects of the stereotypical Finnish image — `iconic model' — on Argentina and Uruguay. The article is a study of the discussions in the Finnish mass media, mainly in Helsingin Sanomat ( HS), the key national newspaper, and in the television coverage of the Finnish Broadcasting Company, YLE. The analysis shows that the Finnish media, too, have created stereotypes that harden attitudes and make conflict resolution more difficult. What is virtually absent in the Finnish media is a democratic multicultural learning culture that fosters and itself is fostered through a more transnational and interdisciplinary perspective. The global and national media have an increasingly important task in such situations of cultural conflict resolution, situations which are also attached to the recent discussions of corporate social responsibility.
Toward the Economy of Pedestrian Movement in Czech and Slovak Shopping Malls
Authors: Spilková Jana , Hochel Matěj
Published: December 2008

This article examines changes in shopping behavior in two postcommunist countries, the Czech Republic and Slovakia, by replicating Bitgood and Dukes's study of pedestrian choice point behavior. It also extends the former study by applying the methodology to a different type of intersection and subjecting the results to a random resampling statistical test. A survey conducted via naturalistic observation in selected Czech and Slovak shopping malls is presented. Is the movement of shoppers disorganized and unplanned, or is there a tendency to use the principles of the economy of movement, which suggests that pedestrians tend to move in a way involving the least number of steps? A randomization resampling test with 100,000 samples was performed on the data obtained in shopping malls. It can be concluded that pedestrians tend to avoid unnecessary steps by economizing their trajectories ( t = 11.34, p = .00013). The results, thus, show that a qualitative change occurred in the shopping behavior of Czech and Slovak shoppers (as compared with year 2002), and there is an obvious tendency to minimize the total distance in correspondence with the principles of the economy of movement.
African Americans and Physical Health
Authors: Christie-Mizell C. André , Kimura Ida Aya , Keith Verna M.
Published: December 2008

This research adds to the literature seeking to clarify the social psychological mechanism through which self-esteem is related to physical health for African Americans. Specifically, this study investigates the relationships among self-esteem, happiness, and physical health limitations for a representative sample of African Americans. Utilizing the Broaden-and-Build Theory of Positive Emotions, these results indicate that the impact of self-esteem on physical health outcomes is mediated by happiness. Interestingly, the positive influence that happiness exerts on physical health is suppressed by age. This study suggests that positive emotions such as happiness are beneficial to outcomes such as physical health by transforming traits such as self-esteem into adaptive capability and personal resources that individuals can use to improve health outcomes.