bluuebunny/crossref_metadata_2025_split huggingface dataset:
Energy‐level position of bistable (CiCs)0 defect in the B configuration in the forbidden band of n‐Si
Authors: Dolgolenko A. , Varentsov M. , Gaidar G. 
Published: September 2004

AbstractPhosphorus‐doped silicon samples grown by various methods after irradiation by fast neutrons of a WWR‐M reactor and subsequent annealing at room temperature were investigated. The calculation of the temperature dependence of effective carrier concentration was carried out in the framework of Gossick's model, taking into account the recharges of defects both in the conducting matrix of n‐Si and in the space charge region of defect clusters. The distribution function of electrons in the acceptor level of bistable defect (CiCs)0 was determined in the case when the concentration of this defect is a function of the Fermi level in the conducting matrix of n‐Si. The concentration of bistable CiCs defect and its energy level at (Ec – 0.123 eV) in the forbidden band of silicon were calculated. The absence of reconciliation between the introduction rate of A‐centers in n‐Si, irradiated by fast neutrons of the reactor, and the concentration of oxygen in 1016–1018 cm–3 limits was determined. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stimulated emission from GaN nanocolumns
Authors: Kikuchi Akihiko , Yamano Kouji , Tada Makoto , Kishino Katsumi 
Published: September 2004

AbstractStimulated emission with very low threshold excitation power density was observed for GaN nanocolumns grown on (0001) sapphire substrate by RF‐plasma assisted molecular beam epitaxy. The photopump measurements were carried out under 355 nm Nd:YAG laser excitation with the surface emission configuration. The threshold excitation power density was 198 kW/cm2 at room temperature. The peak wavelength shifted from 370.2 to 370.9 nm when increasing the excitation power from 130 to 440 kW/cm2. The peak intensity increased nonlinearly with excitation power. For the lower excitation condition using a 325 nm He–Cd laser, the spontaneous emission peak was observed at 363.2 nm and the intensity was 20∼30 times stronger than for a 3.7 μm‐thick MOCVD‐grown GaN film with a dislocation density of 3∼5 × 109 cm–2. With this configuration the peak intensity was increased propotionally with excitation power. These results indicate that GaN nanocolumns have high potential to realize high performance optical devices. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
2D Self‐Assembly of Oligo(p‐phenylene vinylene) Derivatives: From Dimers to Chiral Rosettes
Authors: Miura Atsushi , Jonkheijm Pascal , De Feyter Steven , Schenning Albertus P. H. J. , Meijer E. W. , De Schryver Frans C. 
Published: September 2004

AbstractEnantiomerically pure oligo(p‐phenylene vinylene) diaminotriazine derivatives and a short structurally related achiral diaminotriazine derivative, all having a rigid backbone in common, are studied to self‐assemble at the solution–graphite interface by scanning tunneling microscopy. As a function of the length of the backbone, different two‐dimensional motifs are formed (dimers and rosettes) that are rationalized in terms of the balance between different intermolecular interactions, in this case, intermolecular hydrogen bonding and the packing requirements of the alkyl chains on a graphite surface. In addition, the effect of molecular chirality on monolayer chirality is investigated, revealing molecular size‐dependent expressions of the monolayer chirality.
Suspended Carbon Nanotube Quantum Wires with Two Gates
Authors: Cao Jien , Wang Qian , Wang Dunwei , Dai Hongjie 
Published: September 2004

AbstractSuspended single‐walled carbon nanotube devices comprised of high‐quality electrical contacts and two electrostatic gates per device have been prepared. Compared to nanotubes pinned on substrates, the suspended devices exhibit little hysteresis related to environmental factors and act as cleaner Fabry–Perot interferometers or single‐electron transistors. The high‐field saturation currents in the suspended nanotubes related to optical phonon or zone‐boundary phonon scattering are significantly lower due to the lack of efficient heat sinking. The multiple‐gate design may also facilitate future investigations into the electromechanical properties of nanotube quantum systems.
Distribution and abundance of West Greenland humpback whales (Megaptera novaeangliae)
Authors: Larsen Finn , Hammond Philip S. 
Published: September 2004

AbstractPhoto‐identification surveys of humpback whales Megaptera novaeangliae were conducted at West Greenland during 1988–93, the last 2 years of which were part of the internationally coordinated humpback whale research programme YoNAH, with the primary aim of estimating abundance for the West Greenland feeding aggregation. The area studied stretched from the coast out to the offshore margin of the banks, determined approximately by the 200 m depth contours, between c. 61°70′N and c. 66°N. The surveys were conducted between early July and mid‐August and 993 h were expended on searching effort. A total of 670 groups of humpback whales was encountered leading to the identification of 348 individual animals. Three areas of concentration were identified: an area off Nuuk; an area at c. 63°30′N; and an area off Frederikshåb. Sequential Petersen capture–recapture estimates of abundance were calculated for five pairs of years at 357 (1988–89), 355 (1989–90), 566 (1990–91), 376 (1991–92), and 348 (1992–93). Excluding the anomalously high estimate in 1990–91, the simple mean is 359 (se= 27.3, CV = 0.076) and the inverse CV‐squared weighted mean is 356 animals (se= 24.9, CV = 0.070). These calculations lead us to conclude that between 1988 and 1993 there were 360 humpbacks (CV = 0.07) in the West Greenland feeding aggregation. Using the Cormack–Jolly–Seber model framework non‐calf survival rate was estimated at 0.957 (se= 0.028). Our data have low power (P < 0.3) to detect a trend of 3.1%, assuming the probability of a type I error was 0.05.
Microclimatic stability in burrows of an Afrotropical solitary bathyergid rodent, the silvery mole‐rat (Heliophobius argenteocinereus)
Authors: Šumbera Radim , Chitaukali W. N. , Elichová M. , Kubová J. , Burda H. 
Published: September 2004

AbstractMean depth and mean size of burrow system components, burrow‐soil temperatures and actual diurnal temperatures, humidity and oxygen concentration in burrows of silvery mole‐rats Heliophobius argenteocinereus were measured in two mesic areas in Malawi. Mesic tropic climate, together with soil and plant cover contribute to a diurnally and seasonally stable microclimate even in shallow burrows. Daily and seasonal changes of burrow temperatures were lower compared to those in bathyergids from temperate areas where ambient and burrow temperatures undergo larger fluctuations. Silvery mole‐rats in Malawi are thus probably not distressed by these environmental factors.
Differences in Tachyarrhythmia Detection and Implantable Cardioverter Defibrillator Therapy by Primary or Secondary Prevention Indication in Cardiac Resynchronization Therapy Patients
Authors: WILKOFF BRUCE L. , HESS MIKE , YOUNG JAMES , ABRAHAM WILLIAM T. 
Published: September 2004

Introduction: Although numerous trials have shown benefit of implantable cardioverter defibrillators (ICDs) for either primary or secondary prevention, no trial has prospectively enrolled patients from both indications and analyzed ICD utilization between groups. Methods and Results: We performed a retrospective review of MIRACLE ICD, a randomized, prospective double‐blind trial of cardiac resynchronization therapy (CRT) in the ICD population. Both secondary prevention (N = 563) and primary prevention patients (N = 415) were enrolled. Subgroup analysis for frequency of ventricular tachycardia (VT) and ventricular fibrillation (VF) episodes and detection accuracy revealed that primary prevention patients had a significantly lower frequency of appropriate episodes (0.09 vs 0.43 episodes/month) at significantly faster cycle lengths (303 ± 54 ms vs 366 ± 71 ms, P < 0.0001). These episodes were more likely to be classified as VF by the device and thus receive shock therapy (42% by device classification vs 19% in secondary prevention, P < 0.0001). The absolute rate of inappropriate detections in the primary prevention group per month of follow‐up was lower but constituted a much higher proportion of all episodes (30% vs 14%, P < 0.0001). Most inappropriate detections in the secondary prevention group were due to rapidly conducted atrial fibrillation; most in the primary prevention patients were due to sinus tachycardia. Conclusion: Patients receiving an ICD for CRT therapy with primary prevention indications have a different clinical arrhythmia course than patients with a history of spontaneous VT/VF. This has implications for the optimal programming of ICDs. Longer‐term, prospective evaluation of these differences is warranted and should be investigated in the broader ICD patient population.
Comparison of Conventional and Biventricular Antitachycardia Pacing in a Geometrically Realistic Model of the Rabbit Ventricle
Authors: BYRD ISRAEL A. , ROGERS JACK M. , SMITH WILLIAM M. , POLLARD ANDREW E. 
Published: September 2004

Introduction: ICDs often are programmed with antitachycardia pacing (ATP) as the first response to ventricular tachycardia (VT). Many ICDs have an additional lead available for ventricular pacing. We hypothesized that using the additional lead for ATP would improve therapy by advancing the orthodromic wavefront, thereby reducing the size of the excitable gap and inducing block of all reentrant activity. Methods and Results: Monomorphic VT was initiated in a thin‐walled model of rabbit ventricular myocardium that included an apical infarct and anatomically realistic dimensions. ATP with up to eight pulses was delivered at 90% of VT cycle length to one (conventional) or two (biventricular) stimulation areas. Stimulation areas were adjusted from 0.017 cm2 to 0.169 cm2 to modulate interactions between the antidromic and VT wavefronts, and between the orthodromic wavefront and the VT's refractory region. During conventional ATP, we found that larger stimulation areas terminated the VT in three pulses. Continued pacing after termination caused VT reinitiation in the reversed direction in some instances. With smaller stimulation areas, conventional ATP simply reset the circuit. During biventricular ATP, larger stimulation areas terminated VT in one pulse. There were no instances of reinitiation with reversal. However, with smaller stimulation areas, prolongation of refractoriness near the additional stimulation area facilitated induction of functional reentry with pathways modified by continued pacing. Conclusion: Our modeling suggests that biventricular ATP is superior to conventional ATP under conditions where the additional ventricular lead effectively advances the orthodromic wavefront. Failure to achieve this advancement poses a risk of VT acceleration.
Clustering of RR Intervals Predicts Effective Electrical Cardioversion for Atrial Fibrillation
Authors: VAN DEN BERG MAARTEN P. , VAN NOORD TRUDEKE , BROUWER JAN , HAAKSMA JAAP , VAN VELDHUISEN DIRK J. , CRIJNS HARRY J.G.M. , VAN GELDER ISABELLE C. 
Published: September 2004

Introduction: Atrial fibrillation (AF) is characterized by an irregularly irregular (“random”) heart beat. However, controversy exists whether the ventricular rhythm in AF is truly random. We investigated randomness by constructing three‐dimensional RR interval plots (3D plots), allowing identification of “clustering” of RR intervals. It was hypothesized that electrical cardioversion (ECV) would be more effective in AF patients with clustering, because clustering might reflect a higher degree of organization of atrial fibrillatory activity. Methods and Results: The study group consisted of 66 patients (44 men and 22 women; mean age 68 ± 11 years,) who were referred for ECV because of persistent AF. Twenty‐four‐hour Holter recordings were used to construct 3D plots by plotting each RR interval (x axis) against the previous RR interval (y axis) and the number of occurrences of each of these x,y combinations (z axis). A clustering index was calculated as the percentage of beats within the peaks in the 3D plot. Based on the 3D plots, clustering of RR intervals was present in 31 (47%) of the 66 patients. ECV was effective in restoring sinus rhythm in 29 (94%) of these 31 patients, whereas sinus rhythm was restored in only 25 (71%) of the remaining 35 patients without clustering (P = 0.020). The clustering index ranged from <2% in the 12 patients with failed ECV to >8% in the 32 patients with sinus rhythm at the end of the study (4 weeks after the ECV); the clustering index in the 22 patients with a relapse of AF after effective ECV was intermediate (P = 0.034 and P = 0.042, respectively). Conclusion: This study indicates that ECV is more effective in restoring sinus rhythm in AF patients with clustering compared to patients in whom no clustering is apparent on 3D plots. In addition, the degree of clustering appears to be predictive of the overall outcome of ECV; the higher the degree of clustering, the higher the likelihood of sinus rhythm at follow‐up.
Automatic Recognition of Abnormal Respiratory Events During Sleep by a Pacemaker Transthoracic Impedance Sensor
Authors: DEFAYE PASCAL , PÉPIN JEAN‐LOUIS , POEZEVARA YANN , MABO PHILIPPE , MURGATROYD FRANCIS , LÉVY PATRICK , GARRIGUE STÉPHANE 
Published: September 2004

Introduction: A number of pacemakers use transthoracic impedance to derive minute ventilation as a sensor for rate adaptation. Transthoracic impedance is also able to track fluctuations in tidal volume occurring in sleep apnea/hypopnea syndromes (SAS). We evaluated the feasibility of a transthoracic impedance‐derived pacemaker algorithm for monitoring sleep respiratory disturbances. Methods and Results: Forty‐two patients who presented with a conventional indication for DDD pacing or cardiac resynchronization underwent conventional polysomnography 1 month after implantation of a Talent™ 3 pacemaker (ELA Medical). The respiratory disturbance index (RDI) stored in the pacemaker memory was compared to the apnea/hypopnea index (AHI) derived from polysomnography. The ability of the pacemaker to identify severe SAS patients (AHI ≥ 30) was assessed. A minimal systematic error was observed from a Bland and Altman plot (bias = 0.9 events/hour). The ability of the pacemaker RDI to identify severe SAS patients was determined by analysis of the receiver operator characteristic. A cutoff RDI value of 30.6/hour of recording was found to yield 75% sensitivity, 94% specificity, 75% positive predictive value, and 94% negative predictive value. Conclusion: The RDI monitoring function appears to be of value in screening pacemaker patients for SAS. Its performance is comparable to existing simple screening techniques. The ability to permanently monitor respiration, in combination with other diagnostic capabilities (such as Holter functions), presents a unique opportunity to monitor the association between arrhythmias and disturbances of breathing during sleep.
“Dormant” Pulmonary Vein Conduction Revealed by Adenosine after Ostial Radiofrequency Catheter Ablation
Authors: ARENTZ THOMAS , MACLE LAURENT , KALUSCHE DIETRICH , HOCINI MÉLÈZE , JAIS PIERRE , SHAH DIPEN , HAISSAGUERRE MICHEL 
Published: September 2004

Introduction: The endogenous nucleoside adenosine is an important intermediate in cellular metabolism, a regulator of function in many organ systems, and a pharmacologic agent with potent electrophysiologic effects. We studied the effects of adenosine on the activation of the pulmonary veins (PVs) after successful ostial isolation in patients with atrial fibrillation (AF). Methods and Results: Twenty‐nine patients (21 male; mean age 54 ± 10 years) with refractory highly symptomatic persistent (n = 9) or paroxysmal (n = 20) AF were included in the study. PV isolation was performed using radiofrequency catheter ablation guided by a multipolar basket catheter (Constellation, Boston Scientific). After successful PV isolation, we studied the effects of intravenous adenosine (12–18 mg) on activation of the upper PVs. A total of 83 PVs were successfully isolated. After adenosine, PV activity was recorded in 10 (34%) of 29 left upper PVs studied and in 3 (13%) of 24 right upper PVs, coupled to atrial activity for 20 ± 7 seconds (adenosine positive). In 8 (62%) of 13 cases, PV potentials were recorded in the distal electrodes of the basket catheter only. Dissociated PV rhythms (N = 8) present after PV isolation disappeared after adenosine for 18 ± 7 seconds, even if reconduction was missing. In 14 patients (48%), a second EP study was performed for recurrence of AF. Adenosine‐positive PVs had a nonsignificant higher rate of recovery of conduction than adenosine‐negative veins (71% vs 35%, P = 0.095). Conclusion: Adenosine induces transient conduction in 25% of PVs following successful isolation. Further studies are necessary to determine the physiologic or pathophysiologic role of adenosine‐induced reconduction in human hearts or other organ systems.
Surface Atrial Frequency Analysis in Patients with Atrial Fibrillation:
Authors: RAINE DAN , LANGLEY PHILIP , MURRAY ALAN , DUNUWILLE ASUNGA , BOURKE JOHN P. 
Published: September 2004

Introduction: The aims of this study were to evaluate (1) principal component analysis as a technique for extracting the atrial signal waveform from the standard 12‐lead ECG and (2) its ability to distinguish changes in atrial fibrillation (AF) frequency parameters over time and in response to pharmacologic manipulation using drugs with different effects on atrial electrophysiology. Methods and Results: Twenty patients with persistent AF were studied. Continuous 12‐lead Holter ECGs were recorded for 60 minutes, first, in the drug‐free state. Mean and variability of atrial waveform frequency were measured using an automated computer technique. This extracted the atrial signal by principal component analysis and identified the main frequency component using Fourier analysis. Patients were then allotted sequentially to receive 1 of 4 drugs intravenously (amiodarone, flecainide, sotalol, or metoprolol), and changes induced in mean and variability of atrial waveform frequency measured. Mean and variability of atrial waveform frequency did not differ within patients between the two 30‐minute sections of the drug‐free state. As hypothesized, significant changes in mean and variability of atrial waveform frequency were detected after manipulation with amiodarone (mean: 5.77 vs 4.86 Hz; variability: 0.55 vs 0.31 Hz), flecainide (mean: 5.33 vs 4.72 Hz; variability: 0.71 vs 0.31 Hz), and sotalol (mean: 5.94 vs 4.90 Hz; variability: 0.73 vs 0.40 Hz) but not with metoprolol (mean: 5.41 vs 5.17 Hz; variability: 0.81 vs 0.82 Hz). Conclusion: A technique for continuously analyzing atrial frequency characteristics of AF from the surface ECG has been developed and validated.
Influence of Gender on Arrhythmia Characteristics and Outcome in the Multicenter UnSustained Tachycardia Trial
Authors: RUSSO ANDREA M. , STAMATO NICHOLAS J. , LEHMANN MICHAEL H. , HAFLEY GAIL E. , LEE KERRY L. , PIEPER KAREN , BUXTON ALFRED E. ,   MUSTT Investigators
Published: September 2004

Introduction: Previous studies have demonstrated gender differences in risk of sudden death in patients with ischemic heart disease. The Multicenter UnSustained Tachycardia Trial (MUSTT) evaluated the ability of therapy guided by electrophysiologic (EP) testing to reduce mortality in patients with coronary disease, ejection fraction ≤40%, and spontaneous nonsustained ventricular tachycardia. Methods and Results: We analyzed the influence of gender on results of EP testing and outcome of patients enrolled in MUSTT. Women made up 14% of the overall MUSTT population and were less likely than men to have inducible sustained randomizable ventricular arrhythmias (24% vs 36%, P < 0.001). Baseline characteristics differed between men and women. In randomized patients, women were older, more likely to have had an infarction within 6 months, more likely to have a history of heart failure, and more likely to have recent angina prior to enrollment than men (P < 0.05). In the EP‐guided therapy group, there was no difference in implantable cardioverter defibrillator implantation rate in men and women (45% vs 53%, P = 0.38). There also were no significant gender influences on risk of arrhythmic death or cardiac arrest (2‐year event rate 9% in women and 12% in men, adjusted hazard ratio 0.88) or overall mortality (2‐year event rate 32% in women vs 21% in men, adjusted hazard ratio 1.51). Conclusion: The outcome and benefit of EP‐guided therapy in this trial did not appear to be influenced by gender. However, due to the small numbers of women in the trial, small differences in outcome may not be apparent. Plans for future primary prevention trials should include careful risk stratification of women who less often have inducible sustained ventricular arrhythmias and better left ventricular function despite more frequent heart failure.
Efficacy of Repeat Pulmonary Vein Isolation Procedures in Patients with Recurrent Atrial Fibrillation
Authors: CALLANS DAVID J. , GERSTENFELD EDWARD P. , DIXIT SANJAY , ZADO ERICA , VANDERHOFF MARK , REN JIAN‐FANG , MARCHLINSKI FRANCIS E. 
Published: September 2004

Introduction: Pulmonary vein (PV) isolation is effective in the treatment of most patients with atrial fibrillation (AF). Some advocate the addition of linear ablation techniques to improve efficacy; however, previous studies suggest recurrent PV conduction is responsible for AF recurrence. The aim of this study was to determine the effectiveness of repeat PV isolation in patients with recurrent AF after an initial ablation procedure and to determine if any patient characteristics predict failure of repeat PV isolation procedures. Methods and Results: Seventy‐four patients with two or more AF ablation procedures using selective PV isolation were included. PV isolation was guided with multielectrode ring catheter recordings, electroanatomic mapping, and intracardiac electrocardiography. Radiofrequency energy was delivered using a 4‐mm‐tip catheter (maximum 40 W, 52°C); cooled‐tip ablation was performed in 10 patients. Linear ablation was not performed. Antiarrhythmic drugs were continued for at least 6 weeks after ablation; AF episodes during this period were censored. Reconnection of one or more segments of previously ablated PVs was observed in 97% of patients; reconnected PVs served as the trigger for AF in 77%. Repeat PV isolation resulted in AF control (cure or 90% reduction in AF episodes) in 64 patients (86%) over a follow‐up period of 9.1 ± 6.7 months. “High‐risk” characteristics such as left atrial enlargement, persistent AF, or mitral regurgitation did not predict failure of repeat PV isolation procedures. Conclusion: Recurrent AF following selective PV isolation is overwhelmingly associated with PV electrical reconnection. Repeat PV isolation without linear ablation provides effective treatment for recurrent AF in patients in whom an initial PV isolation procedure failed, independent of clinical characteristics.