bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for impaired axonal regeneration in PMP22 duplication: studies in nerve xenografts
Authors: Sahenk Zarife , Serrano‐Munuera Carmen , Chen Lei , Kakabadze Inga , Najagara Haikady N.
Published: June 2003

Abstract  Whether axonal regeneration in Charcot‐Marie‐Tooth (CMT) neuropathies is impaired has not been addressed in detail. Our studies in nude mice harboring xenografts from patients with different primary Schwann cell (SC) genetic defects suggested an intimate association between the onset of myelination and impairment in the growth capacity of nude mice axons engulfed by the mutant SCs. To assess the effects of peripheral myelin protein 22 (PMP22) gene duplication on the regeneration process, we conducted morphometric studies to generate temporal growth profiles of myelinated axons within the xenografts obtained from CMT1A patients and from healthy controls. Axon size distribution histograms in controls at different time intervals revealed that size differentiation of myelinated fibers within the grafts is established as early as 2 weeks, and that the temporal pattern of myelination of different sized axons has striking similarities to myelination during development. In PMP22 duplication grafts, the onset of myelination is delayed and the regeneration capacity of all fiber sizes is impaired. This defect, however, is most pronounced for the large diameter axons. In addition, significant large fiber loss occurred after 12 weeks with a concomitant new cycle of regeneration of small size axons. These studies show that the PMP22 duplication in SCs have profound effects on the regeneration process, which might be a contributing factor to preferential distal axonal loss.
Clinical Usefulness of Electrophysiologic Testing in Patients with Ventricular Tachycardia and Chronic Chagasic Cardiomyopathy Treated with Amiodarone or Sotalol
Authors: Leite Luiz R. , Fenelon Guilherme , Simoes Aloyr , Silva Georgia G. , Friedman Paul A. , Paola Angelo A.V. de
Published: June 2003

Introduction: This study assessed the role of electrophysiologic testing to identify therapeutic strategies for the treatment of patients with sustained ventricular tachycardia (VT) and chronic chagasic cardiomyopathy treated with amiodarone or sotalol.

Methods and Results: One hundred fifteen patients [69 men (60%); mean age

52 ± 10

years] with chagasic cardiomyopathy presenting with symptomatic VT were studied after loading with Class III antiarrhythmic drugs; 78 had a history of sustained VT, and 37 with symptomatic nonsustained VT had sustained VT induced at baseline electrophysiologic study. All but 12 patients also underwent baseline electrophysiologic study. Mean left ventricular ejection fraction was

0.49 ± 0.14
. Based on results of electrophysiologic study after loading with Class III drugs, patients were divided into three groups: group 1(n = 23)had no sustained VT induced; group 2(n = 45)had only tolerated sustained VT induced; and group 3(n = 47)had hemodynamically unstable sustained VT induced. After a mean follow‐up of52 ± 32months, total mortality rate was 39.1%; it was significantly higher in group 3 than in groups 2 and 1 [69%, 22.2%, and 26%, respectively, P < 0.0001, hazard ratio (HR) 10.4, 95% confidence interval (CI) 3.8, 21.8]. There was no significant difference in total mortality rate between groups 1 and 2 (P = 0.40, HR 1.5, 95% CI 0.75, 4.58). Cardiac mortality and sudden cardiac death rates also were higher in group 3 patients.

Conclusion: In patients with chagasic cardiomyopathy and sustained VT, electrophysiologic testing can predict long‐term efficacy of Class III antiarrhythmic drugs. This may help in the selection of patients for implantable cardioverter defibrillator therapy. (J Cardiovasc Electrophysiol, Vol. 14, pp. 567‐573, June 2003)
Blockade of the Inward Rectifying Potassium Current Terminates Ventricular Fibrillation in the Guinea Pig Heart
Authors: Warren Mark , Guha Prabal K. , Berenfeld Omer , Zaitsev Alexey , Anumonwo Justus M.B. , Dhamoon Amit S. , Bagwe Suveer , Taffet Steven M. , Jalife José
Published: June 2003

Introduction: Stable high‐frequency rotors sustain ventricular fibrillation (VF) in the guinea pig heart. We surmised that rotor stabilization in the left ventricle (LV) and fibrillatory conduction toward the right ventricle (RV) result from chamber‐specific differences in functional expression of inward rectifier (Kir2.x) channels and unequal IK1 rectification in LV and RV myocytes. Accordingly, selective blockade of IK1 during VF should terminate VF.

Methods and Results: Relative mRNA levels of Kir2.x channels were measured in LV and RV. In addition, LV

(n = 21)

and RV

(n = 20)

myocytes were superfused with BaCl2 (5–50 μmol/L) to study the effects on IK1. Potentiometric dye‐fluorescence movies of VF were obtained in the presence of Ba2+

(0–50 μmol/L)

in 23 Langendorff‐perfused hearts. Dominant frequencies (DFs) were determined by spectral analysis, and singularity points were counted in phase maps to assess VF organization. mRNA levels for Kir2.1 and Kir2.3 were significantly larger in LV than RV. Concurrently, outward IK1 was significantly larger in LV than RV myocytes. Ba2+ decreased IK1 in a dose‐dependent manner (LV change > RV change). In baseline control VF, the fastest DF domain

(28–40 Hz)

was located on the anterior LV wall and a sharp LV‐to‐RV frequency gradient of

21.2 ± 4.3 Hz

was present. Ba2+ significantly decreased both LV frequency and gradient, and it terminated VF in a dose‐dependent manner. At 50 μmol/L, Ba2+ decreased the average number of wavebreaks (

1.7 ± 0.9

to

0.8 ± 0.6 SP/sec · pixel, P < 0.05

) and then terminated VF.

Conclusion: The results strongly support the hypothesis that IK1 plays an important role in rotor stabilization and VF dynamics. (J Cardiovasc Electrophysiol, Vol. 14, pp. 621‐631, June 2003)
LocaLisa Catheter Navigation Reduces Fluoroscopy Time and Dosage in Ablation of Atrial Flutter:
Authors: Schneider Michael A.E. , Ndrepepa Gjin , Dobran Ildiko , Schreieck Jürgen , Weber Stefan , Plewan Andreas , Deisenhofer Isabel , Karch Martin R. , Schömig Albert , Schmitt Claus
Published: June 2003

Introduction: Catheter ablation has become a well‐established therapy for isthmus‐dependent right atrial flutter (AFL). Recently, mapping and ablation of AFL have been performed using sophisticated three‐dimensional mapping systems, such as electroanatomic and noncontact mapping systems. The LocaLisa system enables nonfluoroscopic navigation of intracardiac electrode catheters based on impedance changes related to catheter movements in transthoracic current fields. The aim of this randomized prospective study was to compare the efficacy of the LocaLisa system with the conventional mapping/ablation approach for radiofrequency ablation of AFL.

Methods and Results: Fifty consecutive patients with AFL (39 men and 11 women; age

65 ± 10

years) were studied. The patients were randomly assigned to undergo radiofrequency ablation guided by a conventional fluoroscopy‐based approach (24 patients) or by the LocaLisa system (26 patients). Ablation success rate and documentation of bidirectional isthmus block were 100% in both groups. Compared with fluoroscopy‐guided approaches, LocaLisa‐guided procedures demonstrated a reduction in total fluoroscopy time from

15.9 ± 10.6

minutes to

7.5 ± 6.5 minutes (P < 0.005).

Total fluoroscopy dosage was reduced from

21.0 ± 19.8

to

8.7 ± 9.5 Gycm2 (P < 0.05).

Fluoroscopy time required for ablation was significantly shortened in the LocaLisa group

(2.6 ± 2.6 min)

compared with the conventional approach group

(11 ± 10 min, P < 0.0005).

In 9 (35%) of 26 patients, the ablation could be performed with a fluoroscopy time ≤1 minute. There were no significant differences with regard to the number of radiofrequency applications, fluoroscopy time needed for diagnostic reasons, total procedure time, or other ablation data.

Conclusion: Compared with the conventional approach, the LocaLisa system significantly reduces the fluoroscopy times needed for ablation of typical AFL.
(J Cardiovasc Electrophysiol, Vol. 14, pp. 587‐590, June 2003)
Extracellular Acidosis Modulates Drug Block of Kv4.3 Currents by Flecainide and Quinidine
Authors: Singarayar Suresh , Bursill Jane , Wyse Ken , Bauskin Asne , Wu Wan , Vandenberg Jamie , Breit Samuel , Campbell Terence
Published: June 2003

Introduction: As a molecular model of the effect of ischemia on drug block of the transient outward potassium current, the effect of acidosis on the blocking properties of flecainide and quinidine on Kv4.3 currents was studied.

Methods and Results: Kv4.3 channels were stably expressed in Chinese hamster ovary cells. Whole‐cell, voltage clamp techniques were used to measure the effect of flecainide and quinidine on Kv4.3 currents in solutions of pH 7.4 and 6.0. Extracellular acidosis attenuated flecainide block of Kv4.3 currents, with the IC50 for flecainide (based on current‐time integrals) increasing from

7.8 ± 1.1 μM

at pH 7.4 to

125.1 ± 1.1 μM

at pH 6.0. Similar effects were observed for quinidine (

IC50 5.2 ± 1.1 μM

at pH 7.4 and

22.1 ± 1.3 μM

at pH 6.0). Following block by either drug, Kv4.3 channels showed a hyperpolarizing shift in the voltage sensitivity of inactivation and a slowing in the time to recover from inactivation/block that was unaffected by acidosis. In contrast, acidosis attenuated the effects on the time course of inactivation and the degree of tonic‐ and frequency‐dependent block for both drugs.

Conclusion: Extracellular acidosis significantly decreases the potency of blockade of Kv4.3 by both flecainide and quinidine. This change in potency may be due to allosteric changes in the channel, changes in the proportion of uncharged drug, and/or changes in the kinetics of drug binding or unbinding. These findings are in contrast to the effects of extracellular acidosis on block of the fast sodium channel by these agents and provide a molecular mechanism for divergent modulation of drug block potentially leading to ischemia‐associated proarrhythmia.
(J Cardiovasc Electrophysiol, Vol. 14, pp. 641‐650, June 2003)
The Inferior Vena Cava:
Authors: Scavée Christophe , Jaïs Pierre , Weerasooriya Rukshen , Haïssaguerre Michel
Published: June 2003

Mapping in a patient undergoing radiofrequency ablation for drug‐refractory paroxysmal atrial fibrillation in the setting of repetitive, monomorphic atrial ectopic beats with negative p waves in the inferior leads revealed an arrhythmogenic focus located in the posteromedial inferior vena cava (IVC) 1 cm below the right atrium to IVC junction. The focus was mapped using a Lasso catheter with successful irrigated‐tip catheter ablation at the site of earliest activity. This case demonstrates that, in rare cases, arrhythmogenic muscular sleeves can be found in the IVC and that the IVC can be electrically disconnected from the right atrium using radiofrequency energy.
(J Cardiovasc Electrophysiol, Vol. 14, pp. 659‐662, June 2003)
Mechanism of Discordant T Wave Alternans in the In Vivo Heart
Authors: Chinushi Masaomi , Kozhevnikov Dmitry , Caref Edward B. , Restivo Mark , El‐Sherif Nabil
Published: June 2003

Introduction: Compared to concordant T wave alternans (CA), discordant T wave alternans (DA) may be associated with an increased dispersion of repolarization (DR) and a greater propensity to develop reentrant ventricular tachyarrhythmias. The electrophysiologic mechanisms of DA in the in vivo heart are not well understood.

Methods and Results: The mechanisms of DA were investigated in the canine anthopleurin‐A surrogate model of long QT3 syndrome using tridimensional analysis of activation and repolarization patterns from 256 to 384 unipolar electrograms. Cardiac repolarization was evaluated as the activation‐recovery interval (ARI) of local electrograms. Two mechanisms for the development of DA were observed. (1) Stepwise shortening of cycle length (CL) superimposed on preexisting DR resulted in different diastolic intervals (DI) at midmyocardial sites compared to epicardial and endocardial sites. The dispersion of DI coupled with different restitution kinetics at those sites induced DA. (2) The dependence of conduction velocity on DI as the CL is abruptly shortened could result in differential conduction delays at mid sites. This enhanced the dispersion of DI between sites and, coupled with the different restitution kinetics, induced DA. The critical step for the development of DA in both mechanisms was the occurrence of short ARI in two consecutive beats either at epicardial sites in the first mechanism or at mid sites in the second mechanism. Sites with DA had significantly more DR compared to sites with concordant T wave alternans, and ventricular tachyarrhythmias developed mainly in the presence of DA.

Conclusion: In the in vivo heart, DA developed due to critical interaction between dispersion of DI and differences in restitution kinetics at different myocardial sites. The dispersion of DI could result from preexisting DR or differential conduction delay at a critical short CL. DA is critically linked to the development of malignant tachyarrhythmias.
(J Cardiovasc Electrophysiol, Vol. 14, pp. 632‐638, June 2003)
Radiofrequency Ablation of Accessory Pathways Guided by the Location of the Ligament of Marshall
Authors: Hwang Chun , Peter C. Thomas , Chen Peng‐Sheng
Published: June 2003

Introduction: In humans, complex muscle connections are present near the junction between the coronary sinus (CS) and the ligament of Marshall. We hypothesize that these complex muscle connections participate in accessory pathway conduction.

Methods and Results: Electrophysiologic studies and radiofrequency ablation were performed in four patients with refractory AV reciprocating tachycardia. Case 1 was a 19‐year‐old male. Marshall bundle potentials were recorded by a catheter in the vein of Marshall. Radiofrequency energy application from that catheter resulted in successful ablation. Case 2 was a 43‐year‐old male who had undergone two unsuccessful radiofrequency ablation procedures of a left free‐wall accessory pathway by conventional techniques. Coronary sinus electrography during tachycardia and ventricular pacing showed a long V‐A interval. Radiofrequency energy application directed toward the ligament of Marshall eliminated the pathway conduction. Case 3 was a 17‐year‐old male who had undergone three unsuccessful ablation procedures. Radiofrequency energy application directed toward the stump of the vein of Marshall successfully eliminated the pathway conduction. Case 4 was a 20‐year‐old female who underwent one unsuccessful ablation procedure. Successful ablation was achieved in the left atrial free wall, approximately 1 cm above the AV annulus, at a location near the ligament of Marshall.

Conclusion: We report four patients in whom successful accessory pathway ablation was achieved by targeting the ligament of Marshall. These findings suggest that the complex muscle connections among the coronary sinus, ligament of Marshall, and left atrium is important in accessory pathway conduction and maintenance of circus movement tachycardia in these patients.
(J Cardiovasc Electrophysiol, Vol. 14, pp. 616‐620, June 2003)
Late hepatic artery thrombosis after orthotopic liver transplantation
Authors: Gunsar Fulya , Rolando Nancy , Pastacaldi Sabrina , Patch David , Raimondo Maria L. , Davidson Brian , Rolles Keith , Burroughs Andrew K.
Published: June 2003

Late hepatic artery thrombosis (HAT) is a rare complication after orthotopic liver transplantation (OLT), conventionally described as occurring more than 30 days after surgery. Only a few reports document its course. In a consecutive series of 634 OLTs (704 grafts), 11 patients (1.7%) had late HAT, diagnosed a median of 6 months (range, 1.8 to 79 months) after OLT. Clinical variables were compared with those of 415 patients without HAT who had a complete database and follow-up, including cytomegalovirus (CMV) surveillance. At presentation, 11 patients had fever, 4 patients had jaundice. Hepatic abscesses were present in 6 patients (3 patients with biliary leak), 4 patients had biliary tree necrosis (2 patients with biliary leak), and 1 patient had no biliary complications. Five patients (45%) underwent accessory hepatic artery anastomosis versus 73 patients (17%) without HAT (P < .05). Five patients (45%) with late HAT had CMV infection versus 14% without HAT (P < .05). Two episodes of late HAT (11 and 79 months) occurred in patients who underwent re-OLT for early HAT (3.9%). Re-OLT was performed in 8 patients a median of 11 days (range, 3 to 37 days) after diagnosis (preceded by intravenous antibiotics and percutaneous drainage). The other 3 patients underwent partial hepatectomy (1 patient), external percutaneous drainage as unfit for surgery (1 patient), and antibiotic therapy only (1 patient). Death occurred in 4 patients who underwent re-OLT (50%) because of septicemia at 11, 23, and 60 days after re-OLT and 17 days after a third OLT. There was one late death (30 months) after partial hepatectomy (hepatitis C recurrence) and one death 6 months after long-term biliary drainage because of sepsis. The 5 survivors have good health with normal liver function test results at a median 52 months (range, 6 to 57 months). In conclusion, late HAT presents with fever caused by hepatic abscesses or biliary leak associated with biliary ischemia and necrosis. CMV infection and accessory hepatic artery anastomosis are risk factors for late HAT in our cohort. Early intervention followed by re-OLT can salvage patients
Minimally invasive repair of recurrent strangulated umbilical hernia in cirrhotic patient with refractory ascites
Authors: Sarit Cohen , Eliezer Avinoah , Mizrahi Solly
Published: June 2003

To repair a recurrent strangulated umbilical hernia in a cirrhotic patient with refractory ascites, we used a minimally invasive procedure. The laparoscopic repair included a release of the incarcerated small bowel loop and secure of a dual Gortex mesh onto the fascial rim. Our satisfactory long-term results should encourage surgeons to adapt this surgical approach
Adult living donor liver transplantation: Perspectives from 100 liver transplant surgeons
Authors: Cotler Scott J. , Cotler Sheldon , Gambera Michele , Benedetti Enrico , Jensen Donald M. , Testa Giuliano
Published: June 2003

The involvement of healthy living donors and the degree of technical difficulty make adult living donor liver transplantation (LDLT) different from any other surgical procedure. We surveyed 100 liver transplant surgeons to assess their views on the complex issues raised by LDLT. Data were collected at meetings on LDLT and by electronic mail. The study instrument was divided into general, donor, surgeon, recipient, and donor and recipient issues. Subjects provided the projected 1-year survival threshold that they would require for the recipient before they would perform LDLT. They listed the three topics that they thought were most critical for transplant fellows to know about LDLT. A majority agreed that transplant programs have a duty to their patients to offer LDLT, that the increasing success of the procedure will expand indications for liver transplantation, and that the risk to the donor causes them a moral dilemma. There was more divergence of opinion regarding who should have the final say about a potential donor’s candidacy, whether it is difficult for donors to comprehend the risks of the procedure, and whether repeat cadaveric transplantations should be offered for failed LDLT performed for extended indications. Surgeons’ median recipient survival threshold was a conservative 79%. Priorities for educating trainees focused on understanding complications and risks, technical factors, and ethical concerns such as putting the donor first. In conclusion, the findings of this survey indicate that transplant surgeons are working to balance their moral imperative to provide life-saving therapy for transplantation candidates with the risks posed to living donors.
Severe Carpometacarpal Osteoarthritis in Older Arabian Horses
Authors: Malone Erin D. , Les Cliff M. , Turner Tracy A.
Published: June 2003

Objective—To report a severe form of carpometacarpal osteoarthritis (CMC‐OA) affecting primarily older Arabian horses.

Study Design—Retrospective study.

Animals—Thirty‐one horses with CMC‐OA.

Methods—Carpal radiographs (405 sets) from 3 hospitals were evaluated to identify horses with marked osteoproliferative reaction across the medial aspect of the CMC joint. Owners were contacted to obtain detailed histories and status updates. Necropsy specimens of the CMC joint were evaluated at 2 hospitals to determine the prevalence of 2 variations in the articulation between the proximal second and third metacarpal bones.

Results—Thirty‐one horses were identified as having marked osteoproliferative reaction at the CMC joint. Twenty‐three (74%) were Arabian horses. Of the Arabian horses, the average age at admission was 14.4 years. Eight (34.8%) Arabian horses had a known history of trauma. Most were no longer rideable at presentation. Ten of the horses were subsequently euthanatized because of lameness. The dorsal and palmar articulations between the second and third metacarpal bones were examined in 177 horses. The palmar articulation was absent in 48% of Arabian horses and 12.5% of non‐Arabian horses at 1 center, including 4 horses with CMC‐OA. At the second center, the palmar articulation was present in 8 of 8 Arabian horses but was absent in 22 of 92 (24%) non‐Arabian horses.

Conclusions—An increased frequency of this crippling form of OA was observed in Arabian horses. It may reflect an increased prevalence, in some geographical regions, of an absent palmar articulation between the second and third metacarpal bones.

Clinical Relevance—Carpal trauma in some Arabian horses may result in unexpectedly severe carpometacarpal osteoarthritis.
Hand‐Assisted Laparoscopic Left Nephrectomy in Standing Horses
Authors: Keoughan Curry G. , Rodgerson Dwayne H. , Brown Murray P.
Published: June 2003

Objective— To describe a hand‐assisted, laparoscopic technique to remove the left kidney in standing horses.

Study Design— Prospective evaluation.

Animals— Eight horses.

Methods— Food was withheld for a minimum of 12 hours. Horses were sedated with detomidine hydrochloride (0.01–0.02 mg/kg, intravenously) and restrained in standing stocks. The left paralumbar fossa was prepared for surgery, and the surgical site was infiltrated with 2% mepivacaine. Hand‐assisted, laparoscopic removal of the left kidney was performed through an incision in the center of the paralumbar fossa; the surgeon's hand was used to isolate the left kidney and associated vasculature. The renal artery and vein were isolated and individually ligated. After vessel transection distal to the ligatures, the left kidney was exteriorized, the ureter ligated and transected, and the incision closed.

Results— Laparoscopic removal of the left kidney was successfully performed in all horses. Retroperitoneal infiltration of local anesthesia provided adequate anesthesia. Intraoperative hemorrhage occurred in 3 horses. Surgical duration (initial skin incision to transection of the left kidney) ranged from 20 to 90 minutes. In 2 horses, no signs of pain were noted for 48 hours postoperatively.

Conclusion— Hand‐assisted laparoscopic surgery can be used for removal of the left kidney in horses.

Clinical Relevance— Hand‐assisted laparoscopic nephrectomy can be safely performed in standing horses; however, care should be taken to identify accessory branches of the renal artery to limit potential complications with hemorrhage.
Evaluation of a Nontoxic Rigid Polymer as Connecting Bar in External Skeletal Fixators
Authors: Störk Christoph K. , Canivet Philippe , Baidak Alexandre A. , Balligand Marc H.
Published: June 2003

Objective—To investigate the mechanical characteristics of a nontoxic, low‐cost, rigid polymer (RP) and to compare the structural and mechanical properties of a full‐frame external skeletal fixator (ESF) with either RP connecting bars, polymethylmethacrylate (PMMA) connecting bars, or stainless‐steel (SS) clamps and connecting bars.

Study Design—In vitro mechanical evaluation.

Methods—Mechanical properties were assessed using an in vitro bone fracture model with a bilateral uniplanar ESF (type II). Identical ESF were built with connecting bars using RP (n = 8), PMMA (n = 8), and SS connecting bars and clamps (System Meynard;n = 3). Nondestructive mechanical tests were performed in uniaxial compression (AC) and craniocaudal (CC) 4‐point bending, as well as fatigue AC. Composite stiffness for each specimen and for each loading mode was calculated from 6 replicate measures using the slope of the load displacement curve at small displacements.

Results—RP, PMMA, and SS ESF constructs yielded mean ± SD composite stiffness values of 227 ± 15, 381 ± 30, and 394 ± 9 N/mm in AC and of 35 ± 2, 24 ± 2, and 15 ± 0 N/mm in CC, respectively.

Conclusions—Structural and mechanical properties of RP are satisfactorily rigid and fatigue resistant for its use as a connecting bar in ESF.

Clinical Relevance—RP connecting bars in an ESF are a reliable, versatile, nontoxic and inexpensive option for the veterinary surgeon.
Cylindrical Press‐Fit Osteochondral Allografts for Resurfacing the Equine Metatarsophalangeal Joint
Authors: Pearce Simon G. , Hurtig Mark B. , Boure Ludovic P. , Radcliffe Rolfe M. , Richardson Dean W.
Published: June 2003

Objective— To investigate the feasibility of resurfacing the equine fetlock joint using cylindrical, orthotopic, press‐fit, osteochondral allografts.

Study Design— Experimental study.

Animals— Ten mature, mixed‐breed horses.

Methods— Cylindrical, osteochondral grafts (6.5‐mm diameter) were harvested aseptically from cadaveric equine metatarsophalangeal joints. Allografts were transplanted into 6 horses; 4 horses were sham operated. The surgical approach involved creation of a bone block at the origin of the medial collateral ligament and luxation of the metatarsophalangeal joint. Grafts were placed into the medial and lateral metatarsal condyles. Radiographs were taken at 8 and 25 weeks, and lameness was evaluated at 25 weeks. Horses were killed at 25 weeks. Analyses included gross evaluation, microradiography, paravital staining, light microscopy, and cartilage biochemistry.

Results— No complications occurred that could be attributed to the surgical procedure. Graft congruency with the surrounding articular cartilage was fair to excellent. Two horses were sound at 25 weeks. Most grafts had more than 90% articular cartilage coverage, and histologic and microradiographic analysis revealed good graft incorporation and articular cartilage survival. Sulphated glycosaminoglycan concentration was decreased in grafted tissue.

Conclusions— We attribute the viability of osteochondral allografts in the equine fetlock to adequate congruency, stable graft fixation, and the use of orthotopic tissue. Host response to the allograft bone tissue did not affect cartilage viability.

Clinical Relevance— Before clinical use, improvements to instrumentation are required that would decrease damage to grafts and minimize technique‐associated incongruencies of the articular surface at the time of grafting. Larger grafts would also likely be required to resurface a greater surface area.
Tenoscopic Release of the Equine Carpal Canal
Authors: Textor Jamie A. , Nixon Alan J. , Fortier Lisa A.
Published: June 2003

Objective— To develop a tenoscopic method to divide the carpal flexor retinaculum and decompress the carpal canal.

Study Design— Cadaver specimen study and prospective trial.

Animals— Twelve cadaveric limbs, 4 clinically normal horses, and 2 clinically affected horses.

Methods— A tenoscopic approach to the proximolateral aspect of the carpal sheath was used to identify and facilitate endoscopic division of the inner and outer layers of the carpal flexor retinaculum in cadaver limbs. The technique was further evaluated in 4 normal and 2 clinically affected horses.

Results— Anatomic dissection, intraoperative observation, necropsy, histologic evaluation, and both short‐ and long‐term clinical follow‐up indicate that a tenoscopic approach that divides the inner layer of the carpal retinaculum can successfully decompress the equine carpal canal. No iatrogenic damage to surrounding structures was evident, division of the retinaculum was adequate and permanent, and clinical morbidity was negligible. Resolution of effusion was evident in both clinical cases of carpal canal syndrome and lameness resolved in the 1 horse in which long‐term follow‐up was possible.

Conclusions— Tenoscopic release of the carpal flexor retinaculum could provide a minimally invasive method to quickly, safely, and effectively decompress the carpal canal.

Clinical Relevance— Tensocopic release of the carpal flexor retinaculum is a safe alternative to open division of the retinaculum to decompress the carpal canal in horses with carpal canal syndrome.
Effect of TiOx on the formation of titanium silicide layer
Authors: El Omari H. , Boyeaux J. P. , Errkik A. , Lemiti M. , Laugier A.
Published: June 2003

The Al/TiOx/Si, Ti/TiOx/Si, and Mo/TiOx/Si interfaces are studied, before and after thermal treatment, by secondary ion mass spectrometry (SIMS), Rutherford backscattering spectrometry (RBS), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy. The metal layer is selected with regard to the formation of a titanium silicide layer. The reductive nature of the metal was found to be very significant in the interdiffusion of Si and Ti (from titanium oxide). This interdiffusion has the advantage to form a thin titanium silicide layer, which is known to have low contact resistivity. The SIMS, RBS, XPS, and XRD analyses show that after annealing for 10 min at 850 °C under hydrogen ambient, titanium silicide interfacial layers such as Ti5Si3 and TiSi2 C54 were formed in the case of Al/TiOx/Si and Ti/TiOx/Si structures, respectively. There is no significant reaction between Mo and TiOx and no Ti and Si interfacial reaction in the Mo/TiOx/Si system. With thermodynamic considerations, we confirm all the results found in this study.
Copper in glazes of Renaissance luster pottery: Nanoparticles, ions, and local environment
Authors: Padovani S. , Sada C. , Mazzoldi P. , Brunetti B. , Borgia I. , Sgamellotti A. , Giulivi A. , D’Acapito F. , Battaglin G.
Published: June 2003

Following the recent finding that luster decorations in glazes of historical pottery consist of copper and silver nanoparticles dispersed in a glassy medium, the glaze in-depth composition and distribution of copper nanoparticles, copper ions, and their local environment have been studied in original samples of gold and red luster. The study has been fully carried out by nondestructive techniques such as Rutherford backscattering spectrometry, ultraviolet and visible spectroscopy, x-ray fluorescence, and extended x-ray absorption fine structure (EXAFS). Elemental analyses indicate that gold decorations are characterized by silver and copper, while red decorations by copper only. The color is determined mainly by metal nanoparticles. Specifically, silver nanoparticles determine the gold color, while the red color is determined by nanoparticles of copper. EXAFS measurements, carried out at the Cu K edge, indicate that in both gold and red luster copper is mostly the oxidized form (Cu+ and Cu2+) with a large prevalence of Cu+. States and local environment of copper ions are similar to those found in copper–alkali ion-exchanged silicate glass samples. This strongly supports the view that luster formation is mediated by a copper– and silver–alkali ion exchange as a first step, followed by nucleation and growth of metal nanoparticles.
Emission properties of PbO−Bi2O3−Ga2O3−GeO2 glasses doped with Tm3+ and Ho3+
Authors: Song Jay Hyok , Heo Jong , Park Se Ho
Published: June 2003

Heavy metal oxide glasses containing GeO2 were investigated as potential hosts for 1.48 μm fiber-optic amplifiers because of their low phonon energy. Addition of ⩾10 mol % GeO2 to 0.57PbO−0.25Bi2O3−0.18Ga2O3 (mole fraction) glass provided thermal stability as well as good emission properties. The optimum glass composition for 1.48 μm amplifiers, considering lifetimes and population of the Tm3+:3H4 level, was 0.8 (0.57PbO−0.25Bi2O3−0.18Ga2O3)−0.2GeO2 (mole fraction). As the concentration of codoped Ho3+ exceeded 0.2 mol %, the population density of the Tm3+:3H4 level decreased sharply and the population inversion between the H43 and F43 levels in Tm3+ was achieved.
Relation between the molecular orientation of a liquid crystal monolayer and the underlying polyimide film exposed to linearly polarized ultraviolet light
Authors: Usami Kiyoaki , Sakamoto Kenji , Ushioda Sukekatsu
Published: June 2003

We have determined the relation between the in-plane anisotropy of the molecular orientation of a liquid crystal (LC) monolayer and the underlying polyimide film exposed to linearly polarized ultraviolet light (LPUVL). To evaluate the anisotropy of the LC monolayer and the polyimide film, the sample orientation dependence of the polarized infrared absorption spectrum was measured. The in-plane anisotropy of the LC monolayer was found to be proportional to that of the polyimide film, the proportionality factor being about 75%. This result strongly suggests that the alignment of the LC molecules in contact with the LPUVL-exposed polyimide film is induced by an interaction between the polyimide and LC molecules.
Injection of molecules onto hydrogen-terminated Si(100) surfaces via a pulse valve
Authors: Terada Yasuhiko , Choi Byoung-Ki , Heike Seiji , Fujimori Masaaki , Hashizume Tomihiro
Published: June 2003

Using scanning tunneling microscopy and spectroscopy, we tested a pulse-injection method for placing molecules onto hydrogen-terminated Si(100) surfaces. The target molecules were multiwalled carbon-nanotube and π-conjugated poly(3-hexylthiophene) molecules dispersed or dissolved into a hexane or chloroform solvent. The results suggest that pulse injection can be used for fixing a variety of molecules in organic solvents onto H-terminated Si(100) surfaces while keeping most of the surface intact.
Efficient KTiOPO4 blue-light converter for monochromatic 1.3188-μm emission line of pulsed Nd:YAG laser
Authors: Mu Xiaodong , Shi Wei , Ding Yujie J.
Published: June 2003

A frequency converter is designed for producing efficient blue light at 0.4396 μm from a monochromatic, pulsed, 1.3188-μm Nd-doped emission line by quasi-phase-matched (QPM) second-harmonic generation (SHG), followed by sum-frequency generation, in an integrated, periodically poled KTiOPO4 (KTP) and monodomain KTP crystal. An average 55-mW (peak power of 43.0 W) blue light is achieved by us for an average 2.5-W (peak power of 2.0 kW) pump power; the overall conversion efficiency is thus 2.2%. Through polarization optimization, the same device produces an average 435 mW (peak power of 339.8 W) for the red light through QPM SHG, with a corresponding conversion efficiency of 16%. As a practical blue-light converter, the angle- and temperature-tuning characteristics and period tolerance have been fully investigated.
Photocurrents of 14 μm quantum-well infrared photodetectors
Authors: Fu Y. , Willander M. , Jiang J. , Li Ning , Lu W. , Liu H. C.
Published: June 2003

We study the factors that determine photogenerated carriers and response wavelengths of photocurrents of long wavelength (∼14 μm) quantum well (QW) infrared photodetectors (QWIPs). The material structures of QWIPs are first characterized by the photoluminescence measurements (PL). By calculating the density of photogenerated carriers in the continuum above the energy barriers using the PL calibrated QWIP structures, we have demonstrated that due to the sample quality, the photocarriers can be either in miniband states (Bloch states in the multiple quantum wells), or they transport from one quantum well to the next in the form of running waves. By including possible scattering processes at the QWIP working temperature to link the theoretically calculated photocarrier density with the experimentally measured photocurrent, it is shown that the width of the photocurrent peaks of 14 μm GaAs/AlGaAs QWIPs under investigation is determined by the optical phonon emissions of photocarriers. We have further calculated the densities of photocarriers in the QWIPs reported in the literature. It is shown that the Bloch wave boundary conditions are appropriate for QWIPs with narrow QWs, whereas running wave boundary conditions are appropriate for wide QWs.
Electrostatic actuation of thin-film microelectromechanical structures
Authors: Gaspar J. , Chu V. , Conde J. P.
Published: June 2003

Microbridge and cantilever electrostatic actuators are fabricated using thin film technology and surface micromachining at low temperatures (⩽100 °C) on glass substrates. Electrostatic actuation is accomplished by applying a voltage, combining a dc component to a low frequency ac component, between the microstructure and an underlying gate counterelectrode. The movement is optically detected by focusing a laser beam on the top of the structure and monitoring the deviation of the reflected light, which is proportional to the electrostatically induced deflection. The absolute value of the deflection is obtained using a calibrated piezoelectric actuator sample holder. The response of the structure is measured with a precision better than 5 Å. The deflection of the microstructures is studied as a function of the magnitude of the electrostatic load, and of the type (bridge or cantilever) and geometrical dimensions of the structure. The mechanical movement is analyzed using an electromechanical model and mechanical properties, such as the microstructure boundary conditions and the materials’ Young’s modulus in the microstructures, are extracted. Nonlinear effects characteristic of electrostatic deflection are observed at high magnitude electrostatic loads. In addition, nonlinear effects due to mechanical stiffening of the microstructures are also observed near the pull-in voltage.
Angle effect on the estimation of exchange coupling constant J for antiferromagnetically coupled medium
Authors: Ren H. B. , Wang J. P.
Published: June 2003

Exchange coupling constant (J) is an important magnetic parameter for the design of the antiferromagnetically coupled medium. So far, the relationship between the exchange bias (Hex) and exchange coupling constant, Hex=J/Mst, which is deduced from the ferromagnetic–antiferromagnetic coupled system under some conditions, was commonly used to estimate the exchange coupling constant J for such medium. This article first deduces an accurate equation of the exchange coupling constant (J) and the exchange bias Hex for the antiferromagnetically coupled medium in different applied field directions. After considering the effect of easy axis distribution of the magnetic grains in the recording medium, the equation for the antiferromagnetically coupled medium is further revised as Hex=aJ/Mst. a is a constant and depends on the easy axes distribution of magnetic grains, the exchange coupling constant, and the ratio of magnetic parameters between the two magnetic layers. a is found to range from 0.2 to 0.5 for isotropic media to oriented medium. The J value may have been heavily underestimated before by using the previous equation.
Complex structure of carbon nanotubes and their implications for formation mechanism
Authors: Zhou Dan , Chow Lee
Published: June 2003

Complex structures of carbon nanotubes formed from a conventional carbon arc-discharge method have been revealed by high-resolution transmission electron microscopy (HRTEM). The branching and the droplet growth phenomena observed by HRTEM indicate that the formation and growth of carbon nanotubes from an arc-discharge method cannot be simply processed from one end to another. Based on the observation of the growth phenomena and the amorphous carbon residue inside the hollow core of carbon nanotubes, a two-step growth model of carbon nanotubes has been proposed.
Measurement of built-in electrical potential in III–V solar cells by scanning Kelvin probe microscopy
Authors: Jiang Chun-Sheng , Moutinho H. R. , Friedman D. J. , Geisz J. F. , Al-Jassim M. M.
Published: June 2003

We report on direct measurements of the built-in electrical potential in III–V semiconductor-based solar cell devices by using scanning Kelvin probe microscopy. Potential profiles on cross sections of the devices were measured quantitatively and spatially resolved in open and short circuits, under and without illuminations, with selective photon energies matching band gaps of the junctions. The measurements provide valuable information about the electrical properties of the devices, and are useful for understanding the performance of solar cells. On a GaInP2-single junction cell, two potential features were measured and were assigned to the p-n junction and the potential barrier at the interface between the GaInP2 base layer and the GaAs substrate. The potential on the p-n junction is photoactive, and that on the GaInP2/GaAs interface is photoinactive. On a GaInP2/GaAs tandem cell, two potential features were measured near the top and the bottom p-n junctions. When the sample was illuminated by light with photon energies larger than the band gap of the top junction, in the condition of short circuit, a potential peak appeared on the boundary between the bottom cell and tunnel junction due to charge accumulations on the bottom junction.
Microstructural and macroscopic properties of cold sprayed copper coatings
Authors: Borchers C. , Gärtner F. , Stoltenhoff T. , Assadi H. , Kreye H.
Published: June 2003

Cold spraying is a coating technique in which the formation of dense, tightly bonded coatings occurs only due to the kinetic energy of high velocity particles of the spray powder. These particles are still in the solid state as they impinge on the substrate. This study correlates optimized deposition parameters with the corresponding microstructure as well as mechanical and conductive behavior of cold sprayed copper coatings in order to explain possible bonding mechanisms. In addition, the performance of cold sprayed copper coatings is compared to that of cold rolled copper and to coatings prepared by thermal spray methods.
Domain-wall structure and domain-wall strain
Authors: Lee W. T. , Salje E. K. H. , Bismayer U.
Published: June 2003

Stresses and strains within domain walls are important for understanding the interaction of domain walls with point defects, and the surface structure of the domain walls. Unfortunately, attempts to determine these properties of the domain wall by diffraction or other methods fail because of the low resolution of the technique. We outline a method for estimating local stresses and strains within the domain wall using Landau theories of phase transitions based on elastic data. We apply this method to the materials V3Si, TeO2 (paratellurite), and SiO2 (quartz).
Phase transitions in (Ba0.7Sr0.3)TiO3/(001)MgO thin film studied by Raman scattering
Authors: Yuzyuk Yu. I. , Sauvajol J. L. , Simon P. , Lorman V. L. , Alyoshin V. A. , Zakharchenko I. N. , Sviridov E. V.
Published: June 2003

Polarized Raman spectra of heteroepitaxial (Ba0.7Sr0.3)TiO3 thin film deposited on the (001)MgO substrate have been studied in the broad temperature range from 30 to 1300 K. Our results show that the ferroelectric–paraelectric phase transition is markedly shifted to higher temperatures with respect to the bulk ceramics of the same composition. Because of the two-dimensional compressive stresses imposed on the film by the substrate, the symmetry of the paraelectric phase is found to be tetragonal well above the Curie temperature. Near the deposition temperature (1173 K), the thermoelastic compressive stresses vanish and Raman response suggests nearly cubic symmetry. Raman measurements below room temperature show clearly that the phase transition to the rhombohedral phase is completely suppressed and only one phase transition from the tetragonal to the monoclinic phase is revealed at ∼150 K.
Imaging subwavelength holes using an apertureless near-field scanning optical microscope
Authors: Formanek F. , De Wilde Y. , Aigouy L.
Published: June 2003

We present investigations of the light scattered by subwavelength holes in a chromium film using an apertureless near-field scanning optical microscope, which operates either in the visible (λ=655 nm) or in the infrared (λ=10.6 μm). The near-field optical images exhibit patterns around the holes that seem to coincide with the component of the stray electrical field parallel to the tip axis. A tip–sample dipole coupling model provides a satisfactory description of the experimental data recorded in the infrared with light polarized normally to the sample surface.
Wigner function modeling of quantum well semiconductor lasers using classical electromagnetic field coupling
Authors: Weetman Philip , Wartak Marek S.
Published: June 2003

A model of the quantum well laser is formulated using Wigner functions whose evolution is governed by the quantum Boltzmann equations. This model incorporates the heterostructure potential and electromagnetic interactions using a classical field approximation, scattering processes by simple Boltzmann scattering, and spontaneous emission by quantum Langevin theory. The quantum Boltzmann equations are derived from Heisenberg’s equation of motion and then simplified for practical purposes. Calculations are performed for a simplified test system in the steady state in order to illustrate some numerical techniques as well as results that can be obtained. Results shown are for the electron and hole densities and the self-consistent heterostructure potential with and without electromagnetic coupling, the output power versus energy, and the electron and hole currents versus position for two applied bias potentials.
Dielectric and electromechanical properties of Pb(Mg1/3,Nb2/3)O3–PbTiO3 thin films grown by pulsed laser deposition
Authors: Donnelly N. J. , Catalan G. , Morros C. , Bowman R. M. , Gregg J. M.
Published: June 2003

Pulsed laser deposition was used to grow thin films of several compositions from the Pb(Mg1/3,Nb2/3)O3–PbTiO3 (PMN–PT) solid solution as dielectric layers in thin film capacitor structures. They were found to display functional behavior characteristic of relaxors, with the only significant difference between thin film and bulk being a severely reduced dielectric permittivity. Room temperature polarization loops showed a general increase in both the remanent polarization and absolute magnitude of the polarization for a given field with PT content. The electric field-induced strain was primarily examined by in situ x-ray diffraction and although fields greater than 20 MV m−1 were applied to the films, the maximum observed strain was only ∼0.3%, considerably less than the 1.4% seen in single crystal samples. Piezo-response atomic force microscopy studies were consistent in that the macroscopic effective piezoelectric coefficient d33, was found to differ from single crystal measurements by an order of magnitude. However, electrostrictive coefficients (Q33), were found to be comparable to published values for both PMN–PT single crystals and ceramics, ranging between 1 and 9×10−2 C−4 cm2. Consequently, it seems that the relatively poor strain response in these thin films is intimately linked to the reduced permittivity and not to a fundamental difference in the electrostrictive coefficients between bulk and thin film.
Electron states in modulated nanowires
Authors: Lew Yan Voon L. C. , Willatzen M.
Published: June 2003

A theory of electrons in modulated nanowires is presented. We show that these structures are radically different from plain nanowires and quantum-well structures in their electronic, optical, and transport properties. We find that thermionic emission experiments only measure an effective barrier height. It is shown that the polarization of intersubband transitions can be controlled. We also predict a type of longitudinal localization effect induced by lateral confinement and give a simple criterion for its occurrence. This places a lower limit on the radii of nanowires that might be useful for optoelectronic applications. Furthermore, its impact on resonant tunneling is demonstrated.