bluuebunny/crossref_metadata_2025 huggingface dataset:
Orthodromic Pacemaker‐Mediated Tachycardia in a Biventricular System Without an Atrial Electrode
Authors: BERRUEZO ANTONIO , MONT LLUIS , SCALISE ANDREA , BRUGADA JOSEP
Published: September 2004

Pacemaker‐mediated tachycardia is a well‐known complication of dual‐chamber devices. In this report, we describe for the first time a case of orthodromic pacemaker‐mediated tachycardia in a patient in whom a biventricular system without an atrial electrode had been implanted. Retrograde atrial activation was directly produced by the dislodged coronary vein electrode in the AV groove, resulting in simultaneous capture of the left atrium and left ventricle. During tachycardia, AV nodal conduction was via the anterograde pathway of the circuit and limited the ventricular response. Subsequently, right ventricular activation was sensed by the right ventricular electrode that triggered biventricular pacing and left atrial capture, perpetuating the tachycardia. Because the left atrial threshold was higher than the left ventricular threshold, the problem could be resolved easily by lowering the output of the coronary vein electrode.
Implantable Cardioverter‐Defibrillator Malfunction due to Mechanical Failure of the Header Connection
Authors: PICKETT R. ANDREW , SAAVEDRA PABLO , ALI MUHAMMED F. , DARBAR DAWOOD , ROTTMAN JEFFREY N.
Published: September 2004

Four cases of ICD system malfunction occurring within the Medtronic Marquis family over a limited time frame are reported. These cases shared a common element of defective connections between the header post and the right ventricular pace/sense terminal pin that required intervention and reconnection. Inappropriate shocks occurred in two cases. The circumstances of these cases provide important information about the potential difficulties with these devices and highlight the deficiencies of the current system in tracking and analyzing device‐related problems.
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.
Electroanatomic Mapping of the Right Ventricle in a Patient with a Giant Epsilon Wave, Ventricular Tachycardia, and Cardiac Sarcoidosis
Authors: SANTUCCI PETER A. , MORTON JOSEPH B. , PICKEN MARIA M. , WILBER DAVID J.
Published: September 2004

A 47‐year‐old man presented with sustained monomorphic ventricular tachycardia of right ventricular origin. Surface ECG recorded during sinus rhythm showed a bizarre “double QRS” pattern. Biventricular cardiomyopathy was found with predominant right ventricular involvement, due to cardiac sarcoidosis. Electroanatomic mapping was used to characterize the right ventricular substrate abnormalities and to decipher the specific activation abnormalities responsible for the ECG findings.
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.
Myocardial Bundles with Slow Conduction Properties are Present on the Left Interventricular Septal Surface of Normal Human Hearts
Authors: KANEKO YOSHIAKI , TANIGUCHI YASUHIRO , NAKAJIMA TADASHI , MANITA MAMORU , ITO TOSHIO , AKIYAMA MASAHIRO , KURABAYASHI MASAHIKO
Published: September 2004

Introduction: The aim of this study was to examine the electrophysiologic characteristics of the normal left interventricular septum (LIVS).

Methods and Results: We explored the LIVS in search of endocardial potentials following ventricular electrograms during sinus rhythm in 28 patients without structural heart disease. In all patients, low‐frequency (mean amplitude: 0.81 ± 0.33 mV) systolic potentials (LA1) were detected in a basal‐to‐apical activation sequence (earliest to latest QRS‐LA1 interval: 93.3 ± 10.8 ms to 127.1 ± 16.6 ms). Programmed stimulation demonstrated decremental conduction properties, and the effective refractory period of the tissue between the ventricular electrogram and LA1 at baseline (376.7 ± 48.8 ms) was significantly prolonged by disopyramide (421.3 ± 54.1 ms, P < 0.05 vs baseline). In 21 patients (75%), diastolic potentials (LA2) morphologically similar to LA1 (mean amplitude: 0.52 ± 0.17 mV) were detected in an apical‐to‐basal activation sequence (earliest to latest QRS‐LA2 interval: 368.9 ± 32.4 ms to 440.7 ± 45.8 ms). Para‐Hisian pacing with capture of the His bundle showed shorter S‐LA1 and S‐LA2 intervals compared to the beats without His‐bundle capture but with ventricular capture (156.3 ± 11.2 ms vs 183.2 ± 12.3 ms, and 385.7 ± 21.6 ms vs 397.4 ± 23.4 ms, respectively, P < 0.0001). At the same rate, the LA1‐LA2 interval was significantly shorter during right ventricular apical than atrial overdrive pacing (220.4 ± 23.1 ms vs 261.4 ± 30.7 ms, P < 0.0001).

Conclusion: Unique myocardial bundles with slow conduction properties and various electrical connections with the specialized conduction system may exist in the LIVS of normal human hearts.
Localizing and Quantifying Ablation Lesions in the Left Ventricle by Myocardial Contrast Echocardiography
Authors: KHOURY DIRAR S. , RAO LIYUN , DING CHUXIONG , SUN HUABIN , YOUKER KEITH A. , PANESCU DORIN , NAGUEH SHERIF F.
Published: September 2004

Introduction: The inability to determine the extent and intramural depth of ablation lesions can hamper the success of catheter ablation. The study tested the feasibility of differentiating radiofrequency ablation lesions from normal myocardium and quantifying their dimensions by myocardial contrast echocardiography (MCE).

Methods and Results: In 11 normal dogs, we created 14 focal and 4 linear lesions at different left ventricular sites. MCE was performed both before and after ablation by using an intracardiac echocardiography catheter (9 MHz) and infusing contrast microbubbles through the left coronary artery. We initially used two‐dimensional MCE to image focal lesions and subsequently three‐dimensional MCE to image linear lesions. An independent observer examined the lesion pathology. We found that intracardiac echocardiography alone could not delineate lesion dimensions. However, after ablation, MCE localized the lesions as well‐defined, low‐contrast areas within the normally opacified myocardium. Lesion dimensions by MCE immediately after ablation and 30 minutes later were similar. In 12 focal lesions, the average maximum depth (5.55 ± 1.38 mm) and average maximum diameter (10.38 ± 2.09 mm) by MCE were in excellent agreement with the pathologic depth (5.20 ± 1.45 mm) and diameter (10.61 ± 1.67 mm). Two focal lesions could not be detected by MCE and later were found to be superficial. Three‐dimensional MCE correctly reconstructed the extent and shape of linear lesions compared to pathology (length: 18.7 ± 5.7 vs 18.5 ± 5.6 mm; maximum longitudinal cross‐sectional area: 81.2 ± 9.6 vs 76.0 ± 10.3 mm2).

Conclusion: MCE accurately localized and quantified radiofrequency ablation lesions in the normal left ventricle. This new application of MCE may advance ablation for managing ventricular arrhythmias that involve intramural or epicardial regions by providing instantaneous anatomic feedback on the effects of ablation during catheterization.
Tribonanolithography of silicon in aqueous solution based on atomic force microscopy
Authors: Park Jeong Woo , Kawasegi Noritaka , Morita Noboru , Lee Deug Woo
Published: September 2004

The tribonanolithography (TNL) of silicon substrate in aqueous solution based on the use of atomic force microscopy is demonstrated. A specially designed cantilever with a diamond tip, which allows the formation of a protruding oxide layer several nanometers high using a simple machining process with a given pitch, was applied to the TNL process in KOH solution instead of a conventional silicon cantilever. The anisotropic wet etching stopped in the modified area because silicon oxide was resistant to corrosion by KOH. The fabrication of a three-dimensional slant nanostructure is possible by taking advantage of the time lag of oxide formation during etching in KOH solution.
Dynamics of a single ion in a perturbed Penning trap: Octupolar perturbation
Authors: Lara Martı́n , Salas J. Pablo
Published: September 2004

Imperfections in the design or implementation of Penning traps may give rise to electrostatic perturbations that introduce nonlinearities in the dynamics. In this paper we investigate, from the point of view of classical mechanics, the dynamics of a single ion trapped in a Penning trap perturbed by an octupolar perturbation. Because of the axial symmetry of the problem, the system has two degrees of freedom. Hence, this model is ideal to be managed by numerical techniques like continuation of families of periodic orbits and Poincaré surfaces of section. We find that, through the variation of the two parameters controlling the dynamics, several periodic orbits emanate from two fundamental periodic orbits. This process produces important changes (bifurcations) in the phase space structure leading to chaotic behavior.
Errors in thermochromic liquid crystal thermometry
Authors: Wiberg Roland , Lior Noam
Published: September 2004

This article experimentally investigates and assesses the errors that may be incurred in the hue-based thermochromic liquid crystal thermochromic liquid crystal (TLC) method, and their causes. The errors include response time, hysteresis, aging, surrounding illumination disturbance, direct illumination and viewing angle, amount of light into the camera, TLC thickness, digital resolution of the image conversion system, and measurement noise. Some of the main conclusions are that: (1) The 3×8 bits digital representation of the red green and blue TLC color values produces a temperature measurement error of typically 1% of the TLC effective temperature range, (2) an eight-fold variation of the light intensity into the camera produced variations, which were not discernable from the digital resolution error, (3) this temperature depends on the TLC film thickness, and (4) thicker films are less susceptible to aging and thickness nonuniformities.
Influence of overlayer thickness on the density of Lomer dislocations in nanoscale Ni–Cu bilayer thin films
Authors: Mitlin D. , Misra A. , Mitchell T. E. , Hoagland R. G. , Hirth J. P.
Published: September 2004

We report on the evolution of the spacing and the character of misfit dislocations with increasing Ni overlayer thickness at an (001) Ni–Cu interface. At low Ni overlayer thicknesses (3 and 5nm), most of the interface dislocations are 60°1∕2⟨110⟩ glide dislocations, while Lomer edge dislocations constitute only about 5% of the total interface dislocation content. At a 13nm Ni overlayer thickness, the fraction of Lomer dislocations increases to approximately 40% of the total content. This dramatic increase in the fraction of Lomer dislocations is likely related to a “rebound mechanism” which initiates at some critical thickness between 5 and 13nm.
Thickness scaling of polycrystalline Pb(Zr,Ti)O3 films downto 35nm prepared by metalorganic chemical vapor depositionhaving good ferroelectric properties
Authors: Oikawa Takahiro , Morioka Hitoshi , Nagai Atsushi , Funakubo Hiroshi , Saito Keisuke
Published: September 2004

Polycrystalline Pb(Zr0.35Ti0.65)O3 [PZT] films were prepared at 540°C by metalorganic chemical vapor deposition (MOCVD). Lower leakage and lower voltage-saturated 50-nm-thick PZT films were deposited on (111)Ir∕TiO2∕SiO2∕Si substrates than those on (111)Pt∕TiO2∕SiO2∕Si substrates. Moreover, low leakage current and good ferroelectricity were obtained for 35-nm-thick PZT films prepared on (111)Ir∕TiO2∕SiO2∕Si substrates by using source-gas-pulse-introduced MOCVD (pulsed-MOCVD) rather than conventional continuous gas supply MOCVD (continuous-MOCVD). As a result, 35-nm-thick PZT films with a Pr value of 47μC∕cm2 at a maximum applied voltage of 1.2V were obtained on (111)Ir∕TiO2∕SiO2∕Si substrates with pulsed-MOCVD. This opens the way for scaling down the film thickness of polycrystalline PZT films further while retaining good ferroelectricity.
Accurate determination of the thickness or mass per unit area of thin foils and single-crystal wafers for x-ray attenuation measurements
Authors: Tran C. Q. , Chantler C. T. , Barnea Z. , de Jonge M. D.
Published: September 2004

The determination of the local mass per unit area m/A=∫ρdt and the thickness of a specimen is an important aspect of its characterization and is often required for material quality control in fabrication. We discuss common methods which have been used to determine the local thickness of thin specimens. We then propose an x-ray technique which is capable of determining the local thickness and the x-ray absorption profile of a foil or wafer to high accuracy. This technique provides an accurate integration of the column density which is not affected by the presence of voids and internal defects in the material. The technique is best suited to specimens with thickness substantially greater than the dimensions of the surface and void structure. We also show that the attenuation of an x-ray beam by a nonuniform specimen is significantly different from that calculated by using a simple linear average of the mass per unit area and quantify this effect. For much thinner specimens or in the presence of a very structured surface profile we propose a complementary technique capable of attaining high accuracy by the use of a secondary standard. The technique is demonstrated by absolute measurements of the x-ray mass attenuation coefficient of copper and silver.
Near-infrared electroluminescence at room temperature from neodymium-doped gallium nitride thin films
Authors: Kim Joo Han , Holloway Paul H.
Published: September 2004

Strong near-infrared (NIR) electroluminescence (EL) at room temperature from neodymium (Nd)-doped gallium nitride (GaN) thin films is reported. The Nd-doped GaN films were grown by radio-frequency planar magnetron cosputtering of separate GaN and metallic Nd targets in a pure nitrogen ambient. X-ray diffraction data did not identify the presence of any secondary phases and revealed that the Nd-doped GaN films had a highly textured wurtzite crystal structure with the c-axis normal to the surface of the film. The EL devices were fabricated with a thin-film multilayered structure of Al∕Nd-doped GaN∕Al2O3–TiO2∕indium-tin oxide and tested at room temperate. Three distinct NIR EL emission peaks were observed from the devices at 905, 1082, and 1364nm, arising from the radiative relaxation of the F3∕24 excited-state energy level to the I9∕24, I11∕24, and I13∕24 levels of the Nd3+ ion, respectively. The threshold voltage for all the three emission peaks was ∼150V. The external power efficiency of the fabricated EL devices was ∼1×10−5 measured at 40V above the threshold voltage.
Multiple-bit storage properties of porphyrin monolayers on SiO2
Authors: Li Qiliang , Surthi Shyam , Mathur Guru , Gowda Srivardhan , Zhao Qian , Sorenson Thomas A. , Tenent Robert C. , Muthukumaran Kannan , Lindsey Jonathan S. , Misra Veena
Published: September 2004

Hybrid molecule-silicon capacitors have been fabricated by the self-assembly of a monolayer of porphyrin molecules on a silicon oxide surface. The porphyrin employed [5-(4-dihydroxyphosphorylphenyl)-10,15,20-trimesitylporphinatozinc(II)] attaches to silicon oxide via a phosphonate linkage. Cyclic voltammetry current and capacitance/conductance measurements have been used to characterize the capacitors. The presence of multiple distinct peaks in current density and capacitance/conductance measurements are associated with oxidation and reduction of the molecular monolayer. The charge-storage states of the capacitor indicate applicability for use in multiple-bit memory devices.
Gate-controlled resonant interband tunneling in silicon
Authors: Sedlmaier S. , Bhuwalka Krishna K. , Ludsteck A. , Schmidt M. , Schulze J. , Hansch W. , Eisele I.
Published: September 2004

We present gate-controlled resonant interband tunneling on silicon ⟨111⟩. The investigated structure principally consists of a vertical, gated p-i-n diode grown by molecular beam epitaxy. We evaluated the surface tunnel current from a gate-induced two-dimensional electron channel into the quantized hole states of a degenerately doped δp+ layer. This current reveals a negative differential resistance due to resonant interband tunneling in the forward biased p-i-n diode at 200K. Even at room temperature the influence of this tunnel mechanism is observed. The experimental results are in good agreement with simulated band diagrams and their dependence on the applied voltages.
Bottom electrode crystallization method for heat treatments on thin films
Authors: Joanni E. , Mardare A. I. , Mardare C. C. , Marques M. B.
Published: September 2004

A simple method for crystallizing amorphous thin films was developed using platinum bottom electrodes as heating elements. A current was applied to tungsten wires in contact with the platinum and the temperature was measured using a type-K thermocouple. A proportional feedback algorithm was used for controlling the process. The performance of different platinum electrodes was studied. Pt films with different thicknesses were alternatively deposited over Ti and Zr at 700°C. Applying currents up to 2 A to the Pt films, the resistance dependence of temperature was studied. The maximum temperature, 675°C, was obtained when using 200 nm Pt films deposited at 700°C over Ti, with a power consumption of 16 W. The method was applied to the crystallization of PbZr0.52Ti0.48O3 thin films using Pt films deposited at 500°C over Ti and at 700°C over Zr. The results obtained for heat treatments at 650°C with 10°C/s heating and cooling rates showed a pure perovskite phase; the ferroelectric properties were comparable with those from films crystallized by rapid thermal annealing.
Millisecond time resolution neutron reflection from a nematic liquid crystal
Authors: Dalgliesh R. M. , Lau Y. G. J. , Richardson R. M. , Riley D. J.
Published: September 2004

The director reorientation of the liquid crystal 4,4’ octyl cyanobiphenyl in the nematic phase under application of bursts of ac field have been observed using time-resolved neutron scattering in reflection geometry. The relaxation of the director has been shown to agree with existing theory, as determined by material and cell parameters. This result shows that it is possible to use neutron reflection measurements from buried interfaces to follow kinetic processes on a time scale comparable with the pulse length of the ISIS neutron source (20 ms).
Optical tweezers and confocal microscopy for simultaneous three-dimensional manipulation and imaging in concentrated colloidal dispersions
Authors: Vossen Dirk L. J. , van der Horst Astrid , Dogterom Marileen , van Blaaderen Alfons
Published: September 2004

A setup is described for simultaneous three-dimensional manipulation and imaging inside a concentrated colloidal dispersion using (time-shared) optical tweezers and confocal microscopy. The use of two microscope objectives, one above and one below the sample, enables imaging to be completely decoupled from trapping. The instrument can be used in different trapping (inverted, upright, and counterpropagating) and imaging modes. Optical tweezers arrays, dynamically changeable and capable of trapping several hundreds of micrometer-sized particles, were created using acousto-optic deflectors. Several schemes are demonstrated to trap three-dimensional colloidal structures with optical tweezers. One combined a Pockels cell and polarizing beam splitters to create two trapping planes at different depths in the sample, in which the optical traps could be manipulated independently. Optical tweezers were used to manipulate collections of particles inside concentrated colloidal dispersions, allowing control over colloidal crystallization and melting. Furthermore, we show that selective trapping and manipulation of individual tracer particles inside a concentrated dispersion of host particles is possible as well. The tracer particles had a core–shell geometry with a high refractive index material core and a lower index material shell. The host particles consisted of the same material as the lower index shells and were fluorescently labeled. The tracer particles could be manipulated without exerting forces on the host particles because the mixture was dispersed in a solvent with the same refractive index as that of the host particles. Using counterpropagating tweezers strongly scattering particles that could not be trapped by conventional single-beam optical tweezers were trapped and manipulated.
Variable-temperature scanning optical and force microscope
Authors: Fodor P. S. , Zhu H. , Patil N. G. , Jevy J.
Published: September 2004

The implementation of a scanning microscope capable of working in confocal, atomic force and apertureless near field configurations is presented. The microscope is designed to operate in the temperature range 4–300 K, using conventional helium flow cryostats. In atomic force microscope (AFM) mode, the distance between the sample and an etched tungsten tip is controlled by a self-sensing piezoelectric tuning fork. The vertical position of both the AFM head and microscope objective can be accurately controlled using piezoelectric coarse approach motors. The scanning is performed using a compact XYZ stage, while the AFM and optical head are kept fixed, allowing scanning probe and optical measurements to be acquired simultaneously and in concert. The free optical axis of the microscope enables both reflection and transmission experiments to be performed.
Projection ablation lithography cathode for high-current, relativistic magnetron
Authors: Jones M. C. , Neculaes V. B. , Gilgenbach R. M. , White W. M. , Lopez M. R. , Lau Y. Y. , Spencer T. A. , Price D.
Published: September 2004

Initial results are presented of an innovative cathode operating in a relativistic magnetron powered by an accelerator with parameters: −0.3 MV, 1–10 kA, and 0.5 μs pulse length. This cathode is fabricated by ablating a pattern on the cathode using a KrF laser. This projection ablation lithography (PAL) cathode has demonstrated fast current turn-on and microwave startup times have decreased from an average of 193 to 118 ns. The pulselength of 1 GHz microwave oscillation has increased from a 144 ns average to 217 ns. With these improvements in microwave startup and pulse length, the microwave power has approximately remained the same compared to the previously used cloth cathodes. A new triple-azimuthal emission region is tested as means of prebunching the electrons (“cathode priming”) into the three spokes desired for pi mode operation in a six-cavity magnetron. The Tri-PAL cathode priming results in the fastest startup and highest efficiency of relativistic magnetron microwave generation.
H
α
detector system for the Helically Symmetric Experiment
Authors: Gerhardt S. P. , Canik J. M. , Anderson D. T. , Owen L.
Published: September 2004

A system of absolutely calibrated Hα detectors for neutral hydrogen monitoring has been designed and implemented for the Helically Symmetric eXperiment. An array of detectors at fixed poloidal angle but many toroidal angles yields a measurement of the toroidal asymmetry in Hα emission and is used for monitoring hydrogen recycling. A multichord array at the toroidal angle of the gas puff allows an accurate determination of neutral gas penetration. Preliminary neutral gas modeling allows for the estimation of the density of atomic and molecular hydrogen from the Hα emission, which are used for particle transport and flow damping studies.
Self-aligned self-assembly process for fabricating organic thin-film transistors
Authors: Ando Masahiko , Kawasaki Masahiro , Imazeki Shuji , Sasaki Hiroshi , Kamata Toshihide
Published: September 2004

A process for fabricating alignment-free, printable, organic thin-film transistors is presented. This process utilizes a self-assembly phenomenon in which soluble nanomaterials such as metallic nanoparticles and organic molecules are self-assembled into a device structure. To demonstrate this process, solution-processed source∕drain electrodes were self-aligned to a gate electrode using a hydrophobic self-assembled monolayer (SAM) optically patterned onto the gate electrode using a backsubstrate exposure technique. An organic semiconductor film deposited on the patterned SAM was selectively ordered and substantially self-aligned to the gate electrode. This process is called self-aligned self-assembly. A field-effect mobility of 0.15cm2∕Vs and potential minimum channel length of 3μm were experimentally demonstrated when pentacene molecules and silver nanoparticles were used as the semiconductor and electrode materials, respectively.
2.9
THz
quantum cascade lasers operating up to 70K in continuous wave
Authors: Barbieri S. , Alton J. , Beere H. E. , Fowler J. , Linfield E. H. , Ritchie D. A.
Published: September 2004

We report the operation of a quantum cascade laser emitting at a 103μm wavelength (2.9THz). The active region is based on a bound-to-continuum design allowing a low parasitic leakage current, and a high upper-to-lower-state lifetime ratio. The latter is demonstrated by a pronounced decrease of the differential resistance at threshold, which is visible up to high temperatures, and by a weak temperature dependence of the slope efficiency. At 4K, we report a threshold current density of only 105A∕cm2 both in pulsed and continuous-wave operation, and an emitted peak power of 15mW independent of the duty cycle. Maximum operating temperatures of 95K and 70K are observed in pulsed and continuous wave modes, respectively.
Transport properties of ordered-GalnP∕GaAs heterostructures
Authors: Ahrenkiel R. K. , Metzger W. , Friedman D. F.
Published: September 2004

We have studied the transport and recombination properties of Ga0.52In0.48P∕GaAs heterostructures by two transient techniques; Time-resolved photoluminescence and resonant coupled photoconductive decay. When the Ga0.52In0.48P is ordered, the two techniques produce radically different excess-carrier decay characteristics. These data can be explained by invoking a charge-separation mechanism at a type-II heterointerface. At higher excess-carrier injection levels, the charge-separation mechanism vanishes, and the type-I interface properties develop. These data are compatible with the polarization field model of ordered Ga0.52In0.48P.
Reduction of the electrostatic coupling in a large-area internal inductively coupled plasma source using a multicusp magnetic field
Authors: Lee Y. J. , Kim K. N. , Yeom G. Y. , Lieberman M. A.
Published: September 2004

A large area (1020mm×830mm) inductively coupled plasma (ICP) source has been developed using an internal-type linear antenna with permanent magnets forming a multicusp magnetic field. The large rf antenna voltages, which cause the electrostatic coupling between the antenna and the plasma in a large area internal-type linear-antenna ICP source, were decreased significantly by applying the magnetic field near and parallel to the antenna. Through the application of the magnetic field, an approximately 20% higher plasma density, with a value of close to 1.0×1011cm−3 at a rf power of 2000W, and about three times higher photoresist etch rates were observed, while maintaining the plasma nonuniformity at less than 9%.
Splitting electronic spins with a Kondo double dot device
Authors: Feinberg Denis , Simon Pascal
Published: September 2004

We present a simple device made of two small capacitively-coupled quantum dots in parallel. This setup can be used as an efficient “Stern–Gerlach” spin filter, able to simultaneously produce, from a normal metallic lead, two oppositely spin-polarized currents when submitted to a local magnetic field. This proposal is based on the realization of a Kondo effect where spin and orbital degrees of freedom are entangled, allowing a spatial separation between the two spin polarized currents. In the low temperature Kondo regime, the efficiency is very high and the device conductance reaches the unitary limit, e2∕h per spin branch.
Nanocrystalline metal electrodes for high-efficiency organic solar cells
Authors: Taima Tetsuya , Chikamatsu Masayuki , Yoshida Yuji , Saito Kazuhiro , Yase Kiyoshi
Published: September 2004

We demonstrate that indium (In) nanocrystals can be used as efficient small-work function electrodes for organic solar cells. A Schottky-barrier solar cell consisting of the In nanoelectrodes, a zinc phthalocyanine (ZnPc) film as a p-type organic semiconductor, and a gold counterelectrode were assembled by vacuum evaporation on an indium-tin-oxide substrate. Nanoscopic Schottky barriers, which are the origins of photovoltaic effects, were formed at the In nanocrystal∕ZnPc molecule interfaces in the cell. Current density under a dark condition was markedly increased by the introduction of the nanoelectrodes. The power conversion efficiency under air mass 1.5 global solar conditions was 200 fold larger than those of the conventional Pc Schottky-barrier solar cells with film electrodes.
Nanoindentation of polycrystalline silicon-carbide thin films studied by acoustic emission
Authors: Ma X.-G. , Komvopoulos K. , Bogy D. B.
Published: September 2004

Nanoindentation experiments and in situ monitoring of acoustic emission (AE) were used to investigate the evolution of deformation in polycrystalline silicon-carbide thin films. An acoustic sensor attached to the holder of the indenter tip was used to continuously record the AE signal during nanoindentation. The amplitudes of the AE wave forms were used to analyze the response of the indented films in the time domain. In addition, a hybrid time-frequency analysis of the AE events was performed in order to determine the dominant frequencies of the deformation events encountered during nanoindentation. The effects of the film thickness and microstructure and the indenter tip radius on the film deformation behavior are interpreted in terms of the AE response and associated deformation mechanisms. The findings of this study demonstrate that in situ AE monitoring provides potentially useful information about microstructure changes associated with nanoscale deformation processes, such as grain boundary cracking, in thin films subjected to normal contact loading.
High-power deep ultraviolet light-emitting diodes basedon a micro-pixel design
Authors: Adivarahan V. , Wu S. , Sun W. H. , Mandavilli V. , Shatalov M. S. , Simin G. , Yang J. W. , Maruska H. P. , Khan M. Asif
Published: September 2004

Using a micro-pixel design, we report the demonstration of high-power deep UV AlGaN-based light-emitting diodes (LEDs) with peak emission wavelength at 280nm. The design comes in response to lateral current crowding problems, which severely limit the maximum possible active area and the overall performance of ordinary square geometry III-nitride LEDs fabricated on insulating substrates. It is shown that the interconnected micro-pixel geometry significantly reduces both the device series resistance and the thermal impedance, thereby improving heat dissipation and increasing the maximum optical power. The design imparts ever-increasing advantages as the operating wavelength decreases (and the aluminum content increases). The optical power of the 10×10pixel array with an effective area of 222×222μm2 only saturates at dc currents higher than 200mA, which is nearly 50% greater than found for a square geometry LED with identical junction area, fabricated from the same wafer. These 280nm LEDs demonstrated a high on-wafer cw power of 145μW with 200mA of pumping current.
Nanoscale modification of electrical and magnetic propertiesof Fe3O4 thin film by atomic force microscopy lithography
Authors: Hirooka Motoyuki , Tanaka Hidekazu , Li Runwei , Kawai Tomoji
Published: September 2004

We present a report on the nanopatterning of an epitaxial ultrathin film of Fe3O4 with room-temperature (ferri)magnetism using atomic force microscopy (AFM). Fe3O4 thin films with atomically flat surfaces were grown using laser molecular-beam epitaxy on a MgAl2O4(111) single-crystal substrate. (Nanowire) were constructed on Fe3O4 thin film by applying an electric field between an AFM conductive tip and the surface of the film. The minimum width and height in the resulting nanowire are 48nm and 2nm, respectively. The patterned region of the Fe3O4 film surface possesses a resistance which is 105 times higher than the unpatterned region. Furthermore, magnetic force microscopy measurements also revealed that magnetization of the patterned region is strongly suppressed.
Cobalt valence in epitaxial Ti0.93Co0.07O2 anatase
Authors: Cui M. L. , Zhu J. , Zhong X. Y. , Zhao Y. G. , Duan X. F.
Published: September 2004

Anatase Ti0.93Co0.07O2 films, synthesized by pulsed-laser deposition, have been investigated in the transmission electron microscope using selected area electron diffraction, energy dispersive x-ray analysis, and electron-energy-loss spectroscopy (EELS), and by x-ray diffraction measurements. It is found that Co ions are soluble in anatase, and that the unit-cell c-axis parameter is shortened, in some areas to even less than that in pure TiO2 anatase films. This observation was ascribed to substitution of the smaller Co3+ ions into the TiO2 anatase lattice. The EELS data confirm that Co is in either a +2 or +3 formal oxidation state in ferromagnetic Ti0.93Co0.07O2 films.
Electron mobility in very low density GaN∕AlGaN∕GaN heterostructures
Authors: Manfra M. J. , Baldwin K. W. , Sergent A. M. , Molnar R. J. , Caissie J.
Published: September 2004

We report on the transport properties of a tunable two-dimensional electron gas (2DEG) confined at the lower interface of a GaN∕Al0.06Ga0.94N∕GaN heterostructure grown by plasma-assisted molecular beam epitaxy on semi-insulating GaN templates prepared by hydride vapor phase epitaxy. Using an insulated gate Hall bar structure, the electron density is continuously tuned from ∼2×1012 down to 1.5×1011cm−2. At T=300mK, the 2DEG displays a maximum mobility of 80 000cm2∕Vs at a sheet density of 1.75×1012cm−2. At low densities, the mobility exhibits a power law dependence on density −μ∼neα, with α∼1.0, over the range of 2×1011–1×1012cm−2. In this density regime, the mobility is no longer limited by alloy scattering and long-range Coulomb scattering dominates. We discuss the dominant scattering mechanisms that presently limit low temperature mobility at electron densities below 1×1012cm−2.
Room temperature sensing of ozone by transparent p-type semiconductor CuAlO2
Authors: Zheng X. G. , Taniguchi K. , Takahashi A. , Liu Y. , Xu C. N.
Published: September 2004

A transparent p-type semiconductor, CuAlO2, shows selective and reversible response to ozone gas at room temperature. All existing commercial semiconductor ozone sensors are of n type. This study demonstrates the feasibility of developing an inexpensive p type and transparent ozone sensor. Types of transparent p–n junction ozone sensors may be fabricated using the p-type semiconductor CuAlO2 and existing n-type transparent materials such as In2O3.
Spectroscopic ellipsometry characterization of HfxSiyOz films using the Cody–Lorentz parameterized model
Authors: Price J. , Hung P. Y. , Rhoad T. , Foran B. , Diebold A. C.
Published: September 2004

A parameterized, Kramers–Kronig consistent, Cody–Lorentz optical model is used to simulate the dielectric response of thin HfxSiyOz films. Optical constants are determined in the range 0.75–8.35eV. The Cody–Lorentz model has three specific differences when compared to the previously employed Tauc–Lorentz model: (1) weak exponential absorption below the band gap, (2) a modified joint density-of-states, and (3) a restriction on the ε1(∞) parameter. These three differences allow the Cody–Lorentz model to have an improved fit to experimental data. As a result of a more accurate optical model for HfxSiyOz, we were able to identify an interfacial layer with thickness in close agreement with transmission electron microscopy measurements. Use of the Tauc–Lorentz model when fitting the same experimental data could not identify an interfacial layer. Results are also discussed in which the Cody–Lorentz model shows sensitivity to varying degrees of silicate composition.