bluuebunny/crossref_metadata_2025_split huggingface dataset:
Two Regimes of the Equatorial Warm Pool. Part II: Hybrid Coupled GCM Experiments
Authors: Watanabe Masahiro 
Published: July 2008

Abstract
In this second of a two-part study, the two regimes in a simple tropical climate model identified in Part I are verified using a hybrid coupled general circulation model (HCM) that can reproduce the observed climatology and the interannual variability reasonably well. Defining a ratio of basin width between the Pacific and Indian Oceans, a series of parameter sweep experiments was conducted with idealized tropical land geometry. Consistent with the simple model, the HCM simulates two distinct states: the split warm pool regime with large vacillation between the two ocean basins and the single warm pool regime representing current climate. The former is suddenly switched to the latter as the Pacific becomes wider than the Indian Ocean. Furthermore, the vacillation in the split regime reveals a preferred transition route that the warm phase in the Pacific follows that in the Indian Ocean. This route occurs due to convectively coupled Kelvin waves that accompany precipitation anomalies over land. Additional experiments show that the inclusion of the idealized Eurasian continent stabilizes the split regime by reducing the Bjerknes feedback in the Indian Ocean, suggesting the atmosphere–ocean–land interaction at work in maintaining the observed warm pool. No difference in cloud feedback was found between two regimes; this feature may, however, be model dependent.
Both the simple model and the HCM results suggest that the tropical atmosphere–ocean system inherently involves multiple solutions, which may have an implication on climate modeling as well as on the understanding of the observed mean climate.
Time-Expanded Sampling for Ensemble Kalman Filter: Assimilation Experiments with Simulated Radar Observations
Authors: Xu Qin , Lu Huijuan , Gao Shouting , Xue Ming , Tong Mingjing 
Published: July 2008

Abstract
A time-expanded sampling approach is proposed for the ensemble Kalman filter (EnKF). This approach samples a series of perturbed state vectors from each prediction run not only at the analysis time (as the conventional approach does) but also at other time levels in the vicinity of the analysis time. Since all the sampled state vectors are used to construct the ensemble, the number of required prediction runs can be much smaller than the ensemble size and this can reduce the computational cost. Since the sampling time interval can be adjusted to optimize the ensemble spread and enrich the ensemble structures, the proposed approach can improve the EnKF performance even though the number of prediction runs is greatly reduced. The potential merits of the time-expanded sampling approach are demonstrated by assimilation experiments with simulated radar observations for a supercell storm case.
The Influence of the El Niño–Southern Oscillation on Cloud-to-Ground Lightning Activity along the Gulf Coast. Part I: Lightning Climatology
Authors: LaJoie Mark , Laing Arlene 
Published: July 2008

Abstract
Cloud-to-ground (CG) lightning flashes from the National Lightning Detection Network are analyzed to determine if the El Niño–Southern Oscillation (ENSO) cycle influences lighting activity along the Gulf Coast region. First, an updated climatology of lightning was developed for the region. Flash density maps are constructed from an 8-yr dataset (1995–2002) and compared with past lightning climatologies. Second, lightning variability is compared with the phases of ENSO. Winter lightning distributions are compared with one published study of ENSO and lightning days in the Southeast.
Flash density patterns are, overall, consistent with past U.S. lightning climatology. However, the peak flash density for the annual mean was less than observed in previous climatologies, which could be due to the disproportionately large percentage of cool ENSO periods compared to previous lightning climatologies.
The highest annual lightning counts were observed in 1997, which consisted of mostly warm ENSO seasons; the 1997–98 El Niño was one of the strongest on record. The lowest lightning counts were observed in 2000, which had mostly cool or neutral phases of ENSO including the lowest Niño-3.4 anomaly of the study period. Analysis of winter season lightning flash densities substantiated the role of the ENSO cycle in winter season lightning fluctuations. Winter lightning activity increased dramatically during the 1997–98 El Niño. The lowest winter flash densities are associated with cool ENSO phases. Although 8 yr is inadequate to establish a long-term pattern, results indicate that ENSO influences lightning and that further study is warranted. As more years of lightning data are acquired, a more complete climatology can be developed.
Impact Assessment of Simulated Doppler Wind Lidars with a Multivariate Variational Assimilation in the Tropics
Authors: Žagar Nedjeljka , Stoffelen Ad , Marseille Gert-Jan , Accadia Christophe , Schlüssel Peter 
Published: July 2008

Abstract
This paper deals with the dynamical aspect of variational data assimilation in the tropics and the role of the background-error covariances in the observing system simulation experiments for the tropics. The study uses a model that describes the horizontal structure of the potential temperature and wind fields in regions of deep tropical convection. The assimilation method is three- and four-dimensional variational data assimilation. The background-error covariance model for the assimilation is a multivariate model that includes the mass–wind couplings representative of equatorial inertio-gravity modes and equatorial Kelvin and mixed Rossby–gravity modes in addition to those representative of balanced equatorial Rossby waves. Spectra of the background errors based on these waves are derived from the tropical forecast errors of the European Centre for Medium-Range Weather Forecasts (ECMWF) model.
Tropical mass–wind (im)balances are illustrated by studying the potential impact of the spaceborne Doppler wind lidar (DWL) Atmospheric Dynamic Mission (ADM)-Aeolus, which measures horizontal line-of-sight (LOS) wind components. Several scenarios with two DWLs of ADM-Aeolus type are compared under different flow conditions and using different assumptions about the quality of the background-error covariances.
Results of three-dimensional variational data assimilation (3DVAR) illustrate the inefficiency of multivariate assimilation in the tropics. The consequence for the assimilation of LOS winds is that the missing part of the wind vector can hardly be reconstructed from the mass-field observations and applied balances as in the case of the midlatitudes.
Results of four-dimensional variational data assimilation (4DVAR) show that for large-scale tropical conditions and using reliable background-error statistics, differences among various DWL scenarios are not large. As the background-error covariances becomes less reliable, horizontal scales become smaller and the flow becomes less zonal, the importance of obtaining information about the wind vector increases. The added value of another DWL satellite increases as the quality of the background-error covariances deteriorates and it can be more than twice as large as in the case of reliable covariances.
Probabilistic Forecast Calibration Using ECMWF and GFS Ensemble Reforecasts. Part I: Two-Meter Temperatures
Authors: Hagedorn Renate , Hamill Thomas M. , Whitaker Jeffrey S. 
Published: July 2008

Abstract
Recently, the European Centre for Medium-Range Weather Forecasts (ECMWF) produced a reforecast dataset for a 2005 version of their ensemble forecast system. The dataset consisted of 15-member reforecasts conducted for the 20-yr period 1982–2001, with reforecasts computed once weekly from 1 September to 1 December. This dataset was less robust than the daily reforecast dataset produced for the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS), but it utilized a much higher-resolution, more recent model. This manuscript considers the calibration of 2-m temperature forecasts using these reforecast datasets as well as samples of the last 30 days of training data. Nonhomogeneous Gaussian regression was used to calibrate forecasts at stations distributed across much of North America. Significant observations included the following: (i) although the “raw” GFS forecasts (probabilities estimated from ensemble relative frequency) were commonly unskillful as measured in continuous ranked probability skill score (CRPSS), after calibration with a 20-yr set of weekly reforecasts their skill exceeded that of the raw ECMWF forecasts; (ii) statistical calibration using the 20-yr weekly ECMWF reforecast dataset produced a large improvement relative to the raw ECMWF forecasts, such that the ∼4–5-day calibrated reforecast-based product had a CRPSS as large as a 1-day raw forecast; (iii) a calibrated multimodel GFS/ECMWF forecast trained on 20-yr weekly reforecasts was slightly more skillful than either the individual calibrated GFS or ECMWF reforecast products; (iv) approximately 60%–80% of the improvement from calibration resulted from the simple correction of time-averaged bias; (v) improvements were generally larger at locations where the forecast skill was originally lower, and these locations were commonly found in regions of complex terrain; (vi) the past 30 days of forecasts were adequate as a training dataset for short-lead forecasts, but longer-lead forecasts benefited from more training data; and (vii) a small but consistent improvement was produced by calibrating GFS forecasts using the full 25-yr, daily reforecast training dataset versus the subsampled, 20-yr weekly training dataset.
Inappropriate Shocks Diagnosed by Stored Electrograms of Implantable Cardioverter Defibrillators
Authors: Oto Ali , Yildirir Aylin , Kabakci Giray , Atalar Enver 
Published: July 2008

An implantable cardioverter defibrillator is an important therapeutic option for patients with high risk of life-threatening ventricular arrhythmias. However, their use is also asso ciated with several complications including inappropriate shock. Although the most frequent cause of inappropriate shock is supraventricular tachyarrhythmias, lead fracture can also be associated with inappropriate shock. Diagnosis of lead fracture can be made by chest x-ray radiography, fluoroscopic examination, interrogation of the device, and intracardiac electrograms. In this report, the authors present two cases of inappropriate shock due to lead fractures in the costoclavicular region that could only be diagnosed by the help of stored intracardiac electrograms. Methods for diagnosis of lead fractures and modalities to avoid recurrences are also discussed.
Short- and Long-Term Results of Abciximab Versus Aspirin in Conjunction with Thrombolysis for Patients with Peripheral Occlusive Arterial Disease and Arterial Thrombosis
Authors: Schweizer Johannes , Kirch Wilhelm , Koch Reiner , Müller Axel , Hellner Grit , Forkmann Lutz 
Published: July 2008

Acute peripheral occlusive arterial disease is an important cause of morbidity and mortality, particularly among older persons. Catheter-directed thrombolytic therapy is the treatment of choice but has limitations: long lytic times, occlusions refractory to throm bolysis, and a high rate of restenosis. We conducted a pilot study to evaluate the use of the platelet GP IIb/IIIa receptor antagonist abciximab versus aspirin in conjunction with thrombolysis in patients with acute peripheral occlusive arterial disease associated with arterial thrombosis. A total of 84 patients were randomized into two equal groups to receive 5 mg recom binant tissue plasminogen activator intravenously and 500 IU heparin/hour along with either 500 mg acetylsalicylic acid or a bolus of 0.25 mg/kg abciximab followed by 10 μg/min abciximab over 12 hours (heparin reduced to 250 IU/hour). Primary efficacy criteria included the number of rehospitalizations, reinterventions, and amputations during the following 6 months. Secondary endpoints were the changes in the Fontaine stage, Bollinger index (vessel occlusion), ankle-to-brachial ratios, distance to claudication after 6 months, and the duration of the initial local lysis treatment. Adjunctive use of abciximab reduced the rates of rehospitalization, reinterventions, and amputations versus results with the use of aspirin (10 vs 14 occurrences, respec tively ; 9 vs 11; 3 vs 5; when summed, intergroup difference p < 0.05). Secondary periph eral occlusive arterial disease variables became highly significant versus aspirin (p < 0.001 or greater) at 3 and 6 months after treatment. The duration of lysis was markedly shorter upon addition of abciximab versus aspirin (75 vs 110 min; p < 0.001). No major bleeding complications or embolisms occurred. These preliminary results indicate that abciximab may have a useful role when used adjunctively with a thrombolytic agent in older persons with acute peripheral occlusive arterial disease and arterial thrombosis.
Evaluation of Dysrhythmia in Children with Muscular Dystrophy
Authors: Oguz Deniz , Olguntürk Rana , Tunaoglu Fatma Sedef , Gücüyener Kivilcim , Köse Gülşen , Ünlü Mustafa 
Published: July 2008

Myocardial involvement and dysrhythmia are common findings with muscular dystrophy and are among the leading causes of death. The authors evaluated rhythm and conduc tion abnormalities in children with muscular dystrophy by electrocardiography, signal- averaged electrocardiography, and Holter monitoring. Twenty-nine patients (mean age, 8 years) and 29 healthy control subjects were included in the study. Sixty-two percent of patients had electrocardiographic abnormalities defined as deep Q waves in V 6, tall R waves in V1, and QRS axis deviation. The cardiomyopathy index was significantly greater in the patient group whereas QT and QTc dispersion values showed no significant difference. Holter monitoring revealed premature atrial and ventricular contractions more frequently than normal. However all were classified as Lown I and II. Mean heart rate was significantly higher in the patient group. The elec trocardiograms of 41% of the patients showed late potentials. No relationship with these changes and cardiac function was observed. During the study, one patient died whose cardiomyopathy index was longer and had late potentials detected with signal- averaged electrocardiography. In conclusion, standard electrocardiography, cardiomyopathy index, signal-averaged electrocardiography, and Holter monitoring are valuable and reliable monitoring methods in children with muscular dystrophy.
Pulmonary Hypertension Associated with Liver Cirrhosis: An Echocardiographic Study
Authors: Auletta Maria , Oliviero Ugo , Iasiuolo Luigi , Scherillo Giovanna , Antoniello Salvatore 
Published: July 2008

Conflicting results about the prevalence of pulmonary hypertension, ranging from 0.25% to 20%, in liver patients with portal hypertension, have previously been reported. The aim of this study was to evaluate pulmonary arterial pressure in a consecutive series of cirrhotic patients, using a noninvasive method. A complete clinical, laboratory, ultra sonographic, and endoscopic evaluation were performed in 83 consecutive liver patients assessed according to Child's classification and Pugh's score and according to evidence of ultrasonographic and/or endoscopic signs of portal hypertension. A complete echocar diographic evaluation was also performed and pulmonary arterial systolic pressure (PASP) was estimated by measuring tricuspidal regurgitation, using the modified Bernoulli equation. These same evaluations were performed by the same observers in a group of 60 healthy volunteers. The results showed a surprisingly high prevalence (about 20%) of pulmonary hypertension. Patients with more severe liver damage and portal hypertension showed a high prevalence for pulmonary hypertension. A progression in the frequency of portopulmonary hypertension (PPH) was found in Child's classification A to C, and in patients without to patients with evidence of portal hypertension. However, increased PASP was detected in some patients belonging to Child's class A, without evidence of portal hypertension. (continued on next page) In conclusion, the echocardiographic examination (a noninvasive technique), appears suitable for detecting pulmonary hypertension in patients with compensated liver cirrhosis, and can elucidate some aspects of the clinical course of the so-called PPH syndrome.
QT Dispersion in Single Coronary Artery Disease: Is There a Relation Between QT Dispersion and Diseased Coronary Artery or Lesion Localization?
Authors: Tikiz Hakan , Terzi Tural , Balbay Yücel , Demir Ahmet D. , Soylu Mustafa , Keles Telat , Kutuk Emine 
Published: July 2008

It has been shown that QT dispersion (QTD) increases during episodes of myocardial ischemia or infarction. However, no extensive data on the relation between the diseased coronary artery or the localization of stenosis and the QTD are available. The aim of the study was to examine the relation between QTD and diseased coronary artery and lesion localization during exercise stress test in patients with single coronary artery disease without prior myocardial infarction. One hundred nineteen patients with single coronary artery disease and 53 patients with normal coronary arteries were enrolled in study. All patients underwent exercise stress test with modified Bruce protocol, and QT interval parameters were measured at rest and at minute 2 of the recovery (rec-2) period. QT dispersion at rest was found higher in all single-vessel disease groups compared with that in the control group, and corrected QT dispersion at rec-2 period was also markedly higher in left anterior descending, circumflex, and right coronary artery groups compared with that in the control group. No relation was found between QT dispersion and diseased coronary artery or the lesion localization. In conclusion, no qualitative difference was found between QT dispersion and diseased coronary artery or proximal or distal lesion localization. However, it was observed that patients with single-vessel disease had wider baseline QT dispersion as compared with that in the control group, which further increased significantly with exercise. This finding supports the idea that severity of localized ischemia rather than extent of coronary artery disease would be expected to have a greater effect on inducible QT dispersion.
Microalbuminuria, Pulse Pressure, Left Ventricular Hypertrophy, and Myocardial Ultrasonic Tissue Characterization In Essential Hypertension
Authors: Di Bello Vitantonio , Pedrinelli Roberto , Giorgi Davide , Bertini Alessio , Caputo Maria Teresa , Cioppi Adriano , Talini Enrica , Leonardo Moretti , Dell'Omo Giulia , Paterni Marco , Giusti Costantino 
Published: July 2008

Microalbuminuria (UAE) may be considered a marker of systemic vascular dysfunction, while pulse pressure (PP) is an indicator of the stiffness of vascular conduits. Both these parame ters, together with left ventricular hypertrophy (LVH), are linked to cardiovascular morbidity in hypertensive patients. The aim of this study was the analysis of the possible relationships among UAE, PP, and LVH with ultrasonic myocardial textural parameters, which are altered in hypertensives patients. A group of male (n = 70) essential hypertensive patients (mean age: 58 ±7 yr) was analyzed with a group of age-comparable normotensive healthy subjects as controls (n = 32). Ambulatory blood pressure monitoring (ABPM) was performed with an oscil lometric monitor; UAE was measured by nephelometry. A conventional 2D-Doppler echocar diography (to analyze left ventricular mass: LVM) and a quantitative analysis of the echocar diographic digitized imaging with the use of a calibrated digitization system (to calculate the septum and the posterior wall textural parameters) were performed on all subjects. The myocardial mean gray level was calculated to derive the cyclic variation index (CVI). The CVI was significantly lower in hypertensives both for the septum (-16.3 ±22.8 vs 34.7 ±15.3%; p < 0.001 ) and for the posterior wall (-15.2 ±23.6 vs 38.2 ±15.4%; p < 0.001 ). A signifi cant negative correlation was found between logUAE and the CVI of the septum (r = -0.42; p<0.001), between the PP and the CVI of the septum (r = -0.40; p<0.002) and between the CVI and the LVM (r = -0.38; p<0.001). Multiple regression analysis having as dependent variable the CVI at septum level showed as significantly related independent variables: PP (p<0.01), logUAE (p < 0.001), and LVM (p<0.05) (multiple R: 0.76, squared multiple R: 0.57; p<0.001 ). It was found that LVM, logUAE, and PP are all correlated with textural parameters, and the CVI can be considered a sensitive parameter in the identification of an abnormal myocardial texture in hypertension. A high level of arterial stiffness and the presence of vascular dysfunc tion in essential hypertension could participate in the determination of myocardial alterations and permit the identification of patients with the worst prognosis in terms of morbidity or mortality due to cardiovascular events.
Improvement of Peripheral and Cardiopulmonary Performance After a Short-Term Exercise Program with Additive Prostaglandin E1
Authors: Cachovan Milan , Rogatti Waltraud 
Published: July 2008

In patients with intermittent claudication, the walking distance can be increased, both by means of several months of intensive training and administration of IV prostaglandin E 1 (PGE1) for 4 weeks. The aim of this study was, therefore, to investigate whether the combination of intensive training and PGE 1 infusions during pedalergometry can increase peripheral and cardiopulmonary performance after 2 weeks. Ten patients with intermittent claudication received a once-daily intravenous infusion of 60 μg PGE1 over 2 hours during pedalergometry. In addition, a physical training program was carried out mornings and afternoons, as well as progressive treadmill training. Walking distance (3 km/h, 12%) and cardiopulmonary perfor mance were determined at the beginning and end of the 2-week treatment. Results were compared with those of a historical control group having received a similar training program without PGE1. The initial walking distance increased from 71 to 166 m (134%). At the same time, peak work load increased by 108%, and the physical work capacity by 100%. Cardiopulmonary function improvement was reflected in all the parameters investigated (peak VO2; peak VO2/peak work load ratio; slope of ΔVO2/Δt; RER). Compared with the historical control group, the difference between the two groups with regard to the increase in walking distance was significant in favor of the combined training program with PGE1. The combination of short-term intensive training and PGE1 infusions during pedal ergometry significantly improves both the peripheral as well as the highly restricted functional capacity in patients with intermittent claudication.