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Notes: We demonstrate a detection mechanism for 2–5 THz radiation using intersubband transitions between anticrossing electron levels in a GaAs/AlGaAs coupled-quantum-well photodiode. The THz radiation is detected as a modulation in the photocurrent generated by a visible laser. This modulation is caused by carrier heating effects due to absorption of energy by intersubband transitions. Since the frequency of the intersubband transitions varies with the electric-field strength, the device can function as a voltage-tunable THz detector. © 2000 American Institute of Physics.

Notes: We report the observation of self-sustained photocurrent oscillations in a weakly coupled spatially direct intrinsic GaAs/Al0.3Ga0.7As superlattice. The oscillations are attributed to the dynamics of unstable electric field domains related to the Γ−Γ e1-e2 tunneling resonance. The observed oscillation period is much longer than the carrier recombination time and the interwell tunneling time. The nonlinear behavior shows a complex dependence on the optical power and the external bias. © 1999 American Institute of Physics.

Notes: Objective To test the hypothesis that intravenous antibiotics given intra-operatively reduce the failure rate of vesico-vaginal fistula repair.Design A single blind, randomised controlled trial.Setting A district hospital in Benin, West Africa.Population Seventy-nine women undergoing repair of an obstetric vesico-vaginal fistula by a single surgeon at Hopital Evangelique; two women had repeat operations.Methods Participants in the treatment group (n = 41) received ampicillin 500 mg intra-operatively. Controls (n = 40) received no prophylactic antibiotics.Main outcome measures Failure of fistula closure and objective incontinence (a positive pad test) at hospital discharge. Secondary outcomes included febrile morbidity, other antibiotic use and urinary infection.Results Antibiotic prophylaxis did not reduce the odds of failed repair (OR 2.1 95% CI 0.75–6.1) or of objective incontinence (OR 1.9; 95% CI 0.72–5.1). The women in the antibiotic prophylaxis group received less post-operative antibiotics and had less urinary infections at day 10.Conclusions Prophylactic antibiotics should not be used in vesico-vaginal fistulae repair in the developing world outside randomised controlled trials.

Notes: A postal questionnaire was sent to all UK consultant members of the Neuroanaesthesia Society to ascertain whether there was any consensus on indications for use and route of insertion of central venous cannulae in elective neuroanaesthetic practice. Five brief clinical scenarios were presented. Of 179 respondents, 98% indicated that they would insert a central venous cannula into patients requiring excision of an acoustic neuroma in the sitting position, 76% for clipping of an intracranial aneurysm and 75% for resection of an arteriovenous malformation. The antecubital fossa was the preferred route of insertion for 43.5% of respondents with 36.5% preferring the internal jugular approach. The subclavian (17%) and femoral (3%) routes were unpopular first-choice approaches. A significant proportion of respondents (43.5%) do not routinely order a chest X-ray at any stage following pre-operative central venous cannulation. The indications for use and advantages and disadvantages of each route of insertion, with reference to neuro-anaesthetic practice, are discussed.

Notes: Objective  This study was conducted to compare the performance of liquid-based cytology (LBC) and conventional cytology (CS) in the high prevalence setting of colposcopy clinic.Design  A split sample of matched ThinPrep (TP) and conventional smear from 563 patients were evaluated blindly. The performance of both techniques was compared with the gold standard of biopsy results or normal colposcopy examination in 441 cases.Setting  Colposcopy clinic of an inner city hospital for women and children.Sample  Five hundred and sixty-three women referred to colposcopy clinic over 14-month period.Methods  Cervical smears were taken from 563 women referred for colposcopy. Using the split-sample technique, the material was spread on a conventional (CS) slide and the remaining material rinsed in a PreservCyt solution. A T2000 processor was used to prepare LBC preparations. All women underwent colposcopy/biopsy according to local protocol. Four hundred and forty-one women met the diagnostic standard criteria of the study, which was either a normal colposcopy or histopathology result. Sensitivity, specificity and positive and negative predictive values were calculated for both methods of cytology preparations.Main outcome measures  Matched TP and conventional smears, detection of abnormality, matched biopsies, sensitivity, specificity, and positive and negative predictive values.Results  Inadequate rates for CS and LBC (TP) were 4.3% and 0.68%, respectively. In 73% of cases, the CS and the LBC preparations showed exact agreement, whereas 77% agreement was seen when comparison was made for amalgamated low grade and high grade abnormalities. Low grade cytological abnormalities accounted for 44% of LBC slides versus 37% in CS slides. High grade cytological abnormalities accounted for 22% of LBC versus 17% seen in CS cases (P 〈 0.001). LBC showed increased sensitivity in the detection of CIN2 or worse than CS (92% and 83%, respectively) and CS showed greater specificity than LBC (82% and 76%, respectively).Conclusions  In high prevalence setting, LBC performed at least as well as CS. The inadequate rate was significantly lower with LBC. The numbers are too small, however, to make confident comments about increased sensitivity and negative predictive value with LBC. Larger studies are required to verify these findings.