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Notes: We present a study of the effect of phosphorus passivation on the surface electric field of undoped GaAs using photoreflectance spectroscopy. Surface electric fields were determined in surface/intrinsic/n-type (s-i-n+) samples prepared with various surface phosphorus treatments. A comparison with H2S passivated films and InGaP capped layers prepared in situ in the same growth equipment is also presented. Phosphorus surface passivation was achieved by (1) exchange reaction of the GaAs surface under tertiarybutylphosphine vapor or (2) direct growth of GaP thin epitaxial layers. The total coverage of phosphorus has been estimated by x-ray diffraction techniques. We observe a maximum reduction of the surface Fermi level using epitaxially grown GaP with an effective coverage of two monolayers. Atomic force microscopy images of all passivation treatments exhibit excellent surface morphology without roughening. The passivation effects decreased somewhat over time but reductions in the Fermi level and density of surface states are still quite large after several months of air exposure. © 2000 American Institute of Physics.

Notes: We describe firm pricing when consumers follow simple reservation price rules. In stark contrast to other models in the literature, this approach yields price dispersion in pure strategies even when firms have the same marginal costs. At the equilibrium, lower price firms earn higher profits. The range of price dispersion increases with the number of firms: the highest price is the monopoly price, while the lowest price tends to marginal cost. The average transaction price remains substantially above marginal cost even with many firms. The equilibrium pricing pattern is the same when prices are chosen sequentially.

Notes: Objective To assess the feasibility and outcome of laparoscopic supracervical hysterectomy with removal of the cervical transformation zone.Design A prospective clinical study.Setting The department of Gynaecology, Royal Surrey County Hospital, Guildford.Subject Eleven consecutive women who were on the waiting list for abdominal hysterectomy and fulfilled the selection criteria.Intervention Laparoscopic supracervical hysterectomy using a modification of the classical abdominal supracervical hysterectomy technique with removal of the cervical transformation zone.Main outcome measures Operating time, blood loss, duration of hospital stay, time to full recovery and complications.Results All 11 procedures were successfully completed laparoscopically. The mean operating time was 111 min, and mean blood loss was 185 ml. The mean duration of hospital stay was three days, and the mean time to full recovery was 20 days. There were no major complications.Conclusions Laparoscopic supracervical hysterectomy appears to result in a shorter hospital stay and more rapid recovery than total abdominal hysterectomy. This shortened convalescence is of benefit to the patient. The operation appears to be safe when carried out by surgeons experienced in laparoscopic surgery. A randomised comparative study with total abdominal hysterectomy is currently being undertaken.

Notes: Early Repeated Cardioversion for AF Recurrence. Introduction: The clinical value of cardioversion (CV) of persistent atrial fibrillation (AF) is limited by the high rate of early AF recurrence, which may be related to the persistence of atrial electrical remodeling. We examined the hypothesis that the likelihood of maintaining sinus rhythm after CV of persistent AF is significantly enhanced by a policy of early repeated CV. Methods and Results: Fifty-nine patients with persistent AF underwent internal CV (CV 1). Those patients cardioverted were monitored with daily transtelephonic ECG. In the event of AF recurrence, these patients were admitted rapidly for repeat CV (CV 2) and, if further recurrence occurred, a third CV (CV 3) was performed. Daily ECG monitoring was continued until 1 month of sinus rhythm was maintained or a total of three CVs were performed. Of the 59 patients undergoing CV 1, 43 were discharged in sinus rhythm and 29 subsequently had AF recurrence during monitoring. Twenty-three of these underwent CV 2 and 11 of these underwent CV 3. Of those having repeated CVs, only 4 patients maintained sinus rhythm for 1 month (3 after CV 2 and 1 after CV 3). The remaining patients had repeated AF recurrence during the monitoring period. Mean time from AF recurrence to CV 2 was 20 ± 13 hours and from AF recurrence to CV 3 was 13 ± 7.2 hours. Atrial effective refractory periods increased from 189 ± 16 msec at CV 1 to 215 ± 18 msec at CV 3 (P 〈 0.05), indicating reversal of atrial electrical remodeling during this period. Conclusion: A policy of early repeated CVs for AF recurrence has very limited clinical value despite evidence of reversal of atrial electrical remodeling. The time between AF recurrence and repeat CV may need to be reduced further if such a policy is to succeed.

Notes: Atrial Arrhythmias After Cardioversion of AF. Introduction: Recent reports have highlighted the importance of focal atrial arrhythmias as a curable cause fur a group of patients with frequently recurrent paroxysmal atrial fibrillation (AF). The importance of this arrhythmia mechanism in the general population of patients with persistent AF is unknown. Methods and Results: After successful internal cardioversion of 50 consecutive patients with persistent AF (mean age 60 years, mean duration of AF 26 months), endocardial activity in the immediate postcardioversion period was analyzed for the presence of focal atria activity. Postcardioversion atrial arrhythmias were considered to be focal if there was evidence of a localized source of repetitive early atrial activation, either in the form of (1) self-terminating monomorphic atrial tachycardia (at least five heats) or (2) recurrences of AF with an initial atrial activation sequence (first five beats) that was both monomorphic and reproducible with repeated recurrences. Evidence for a focal atrial arrhythmia was present in 20 of the total group of 50 patients (40%). Multivariate analysis of clinical characteristics revealed the diagnosis of lone AF as the only independent predictor of a focal source of AF (P = 0.028). Thirty-nine patients were discharged from hospital in sinus rhythm. At 1-month follow-up. 25 (64%) of these 39 patients had suffered AF recurrence. The only significant predictor of AF recurrence was evidence of a focal source of atrial arrhythmia immediately after cardioversion, with a relative risk of 1.73 (range 1.1 to 2.7: P = 0.015). Conclusion: Focal atrial arrhythmias are common in patients presenting with “idiopathic” persistent AF, suggesting a possible causative role in the generation of this common arrhythmia.

Notes: Introduction: Amiodarone is effective in preventing the recurrence of atrial fibrillation (AF) after cardioversion (CV). Dispersion of atrial refractoriness may be relevant to the generation of AF. We designed a study to determine the electrophysiologic effects of amiodarone in patients with previous early recurrence of AF after CV. Methods and Results: Fifteen patients with previous AF recurrence (without antiarrhythmic drugs) after CV (CV1) were selected for amiodarone therapy and repeat CV (CVamio). Prior to CV1, mean AF cycle length (AFCL) had been recorded at four atrial sites (right atrial appendage [RAA], distal coronary sinus [DCS], right atrial lateral wall [LAT], and interatrial septum [IAS]) and dispersion of AFCL had been calculated. These patients were treated with amiodarone and, prior to CVamio, AFCL was recorded at the four atrial sites as for CV1. Between CV1 and CVamio, AFCL increased at all atrial sites: 153 ± 13 msec to 179 ± 14 msec at RAA, 144 ± 12 msec to 174 ± 18 msec at DCS, 158 ± 13 msec to 182 ± 16 msec at LAT, and 161 ± 18 msec to 181 ± 17 msec at IAS. Dispersion of AFCL decreased from 24 ± 10 msec at CV1 to 15 ± 11 msec at CVamio (P = 0.01) . The median time in sinus rhythm increased from 3.12 hours post CV1 to 28 days post CVamio (P 〈 0.02) . Conclusion: Amiodarone causes a reduction in the dispersion of AFCL. This action may be relevant to the beneficial effects of amiodarone in patients with AF. (J Cardiovasc Electrophysiol, Vol. 14, pp. 485-491, May 2003)

Notes: Introduction: Focal atrial fibrillation (AF) may initiate with an irregular rapid burst of atrial ectopic (AE) activity from a pulmonary vein (PV) focus, but how AF is maintained it is not known. The crista terminalis (CT) is an important line of block in atrial flutter (AFL), but its role in AF has not been determined. The aim of this study was to examine the conduction properties of the CT during onset of AF. Methods and Results: In 10 patients (mean age 38 ± 8 years), we analyzed conduction across the CT during onset of focal AF from an arrhythmogenic PV and during pacing from the same PV at cycle lengths of 700 and 300 ms. A 20-pole catheter was positioned on the CT using intracardiac echocardiography. In 10 control patients with no history of AF, we analyzed conduction across the CT during pacing from the distal coronary sinus at 700 and 300 ms. In all 10 AF patients, AF was initiated with 1 to 9 AE beats (median 5) from a PV. During sinus rhythm, there were no split components (SC) recorded on the CT. During PV AE activity, discrete SC were recorded on the CT in all patients over 6.3 ± 0.9 bipoles (3.7 ± 0.3 cm). Maximal splitting of SC was 66 ± 31 ms (37–139). There was an inverse relationship between AE coupling intervals and the degree of splitting between SC in all patients. Degeneration to AF was preceded by progressive decrement across the CT. SC were recorded during PV pacing at 700 and 300 ms (maximal distance between SC of 24 ± 3 ms and 43 ± 5 ms, respectively, P 〈 0.001). Maximum SC at CT in controls was 13 ± 8 ms at 700 ms (P = 0.06 vs AF patients) and 16 ± 9 ms at 300 ms (P 〈 0.01 vs AF patients). Conclusion: (1) These observations provide evidence of anisotropic, decremental conduction across the CT during onset of focal AF and during pacing from the same PV. A line of functional conduction block develops along this anatomic structure (CT). Whether this line of block acts as an initiator of AF or simply contributes passively to nonuniform fibrillatory conduction is unknown. (2) In some patients with focal AF, development of conduction block along the CT may provide a substrate for typical AFL.