Mid-infrared w quantum-well lasers for noncryogenic continuous-wave operation.

We review the recent progress of electrically injected and optically pumped mid-IR lasers based on antimonide quantum wells with the type II W configuration. W quantum-well diodes have achieved cw operation up to 195 K at lambda = 3.25 mum. Optically pumped devices that employ the diamond pressure bond heat sink have reached 290 K at 3 mum and 210 K at 6 mum. Pulsed power conversion efficiencies of up to 7% at 220 K have been attained by use of an optical pumping injection cavity approach, in which an etalon cavity for the pump beam significantly enhances its absorptance. The angled-grating distributed-feedback configuration has been used to obtain near-diffraction-limited output for an optical pumping stripe width of 50 mum.

In situ combustion measurements of CO with diode-laser absorption near 2.3 microm.

In situ measurements of CO concentration were recorded with tunable diode-laser absorption spectroscopy techniques in both the exhaust and the immediate post-flame regions of an atmospheric-pressure flat-flame burner operating on ethylene air. Two room-temperature cw single-mode InGaAsSb/AlGaAsSb diode lasers operating near 2.3 microm were tuned over individual transitions in the CO first overtone band (v' = 2 <-- v" = 0) to record high-resolution absorption line shapes in the exhaust duct [79 cm above the burner, approximately 470 K; R(15) transition at 4311.96 cm(-1)] and the immediate postflame zone [1.5 cm above the burner, 1820-1975 K; R(30) transition at 4343.81 cm(-1)]. The CO concentration was determined from the measured absorption and the gas temperature, which was monitored with type-S thermocouples. For measurements in the exhaust duct, the noise-equivalent absorbance was approximately 3 x 10(-5) (50-kHz detection bandwidth, 50-sweep average, 0.1-s total measurement time), which corresponds to a CO detection limit of 1.5 ppm m at 470 K. Wavelength modulation spectroscopy techniques were used to improve the detection limit in the exhaust to approximately 0.1 ppm m (approximately 500-Hz detection bandwidth, 20-sweep average, 0.4-s total measurement time). For measurements in the immediate postflame zone, the measured CO concentrations in the fuel-rich flames were in good agreement with chemical equilibrium predictions. These experiments demonstrate the utility of diode-laser absorption sensors operating near 2.3 microm for in situ combustion emission monitoring and combustion diagnostics.

The polypropylene pubovaginal sling for the treatment of recurrent stress urinary incontinence.

PURPOSE: The significance of a 2-team approach to the problems of recurrent incontinence in patients with extensive pelvic scarring from previous surgery is emphasized. MATERIALS AND METHODS: We reviewed 88 consecutive patients who presented between January 1986 and November 1992. The demonstration of a scarred, wide open, proximal urethra or drain pipe urethra was the important selection criterion. Two teams, 1 operating abdominally and 1 vaginally, released the bladder neck from its bed of scar under direct vision and set the sling in place with minimal tension at the bladder neck. RESULTS: Of the women 75 (85.2%) were cured of the stress urinary incontinence and 8 (9.1%) had improvement with mainly urge incontinence, while 5 (5.7%) operations failed. There was a significant association between chronic chest disease and failure. CONCLUSIONS: The 2-team polypropylene (Marlex) mesh approach continues to be an effective treatment for women with complicated stress urinary incontinence.

Optical bistability in asymmetric Fabry-Perot laser-diode amplifiers.

We present what is to our knowledge the first study of optical bistability in Fabry-Perot laser-diode amplifiers that have asymmetric facet reflectivities. When operated in reflection, the light input-light output characteristics exhibit a transition from counterclockwise to clockwise hysteresis by way of an X-shaped or butterfly hysteresis. This transition can be achieved by a change in either the device bias or the phase detuning of the incident light. Our results are in good agreement with calculation.

Generation of subpicosecond high-power optical pulses from a hybrid mode-locked semiconductor laser.

Ultrashort optical pulses 0.46 psec in duration with over 70 W of peak power are generated from an all-semiconductor laser-diode system. These results represent to our knowledge both the shortest and most-intense optical pulses generated from an all-semiconductor laser system.

The effect of capsular polysaccharide and lipopolysaccharide of Bacteroides fragilis on polymorph function and serum killing.

The determinant responsible for the ability of Bacteroides spp. to inhibit polymorph phagocytic killing of aerobic organisms has not yet been identified. Therefore, the roles of lipopolysaccharide and capsular polysaccharide of B. fragilis were investigated. Serum-resistant and serum-sensitive strains of Proteus mirabilis were used to indicate inhibition of phagocytic killing and serum killing of aerobes. Whole organisms of B. fragilis, purified lipopolysaccharide and capsular polysaccharide were added to an in-vitro phagocytosis system. Results showed that greater than 10(7) bacteroides/ml inhibited both serum and phagocytic killing. Concentrations below 10(7)/ml had little effect on either process. Purified capsular polysaccharide (10 or 100 micrograms/ml), either alone in the system or in combination with sub-inhibitory concentrations of B. fragilis also markedly inhibited serum and phagocytic killing. Lipopolysaccharide (9 micrograms/ml) appeared relatively inert. B. ovatus, reputedly non-capsulated, produced identical results to those obtained with B. fragilis, but an encapsulated strain of Streptococcus pneumoniae did not inhibit serum or phagocytic killing.

The effect of faecal loading on colonic anastomotic healing.

The effect of faecal loading of the colon on the healing of rat colonic anastomoses has been investigated in a prospective randomized and controlled study. Anastomotic dehiscence occurred significantly more often when the bowel was loaded with faeces at the time of operation than when it was empty. Suture line cultures bore no relationship to the outcome of the anastomosis. This result emphasizes the importance of an empty colon as a contributory factor in successful colonic healing in the rat.

The effect of surgical drainage materials on colonic healing.

The effect of surgical drainage materials on rat colonic healing has been investigated in a prospective randomized and controlled study. Latex, silicone rubber (Silastic), polyvinylchloride (PVC) and polytetrafluoroethylene (Teflon) tubes were implanted alongside a colonic anastomosis and compared with a 'no drain' group using mechanical and histological assessments. There was a significant increase in anastomotic leakage in the latex group in which there appears to be a local inhibition of healing. Silastic, PVC and Teflon were not found to interfere with healing. The continued use of latex drains in colonic surgery is therefore questioned.

Surgical audit: Comparison of the work load and results of two hospitals in the same district.

Surgical audit is being undertaken to monitor and compare (by computer) the type of patient, work load, and results of two similar surgical units. Both units are in the City and Hackney District of London, one at St Bartholomew's Hospital and the other at Hackney Hospital. During 1978, 736 patients were admitted by the unit at St Bartholomew's Hospital and 902 by the unit at Hackney. At St Bartholomew's 70% of admissions were elective compared with 49% at Hackney, where 86% of patients lived within the district compared with only 36% at St Bartholomew's. The wound was the commonest site for complications, infection affecting 9% of those at Hackney and 6% at St Bartholomew's, despite identical antibiotic policies. There were six post-operative deaths at St Bartholomew's and 32 at Hackney. In both hospitals the length of stay was similar, 50% of patients being discharged within one week and 80% within two weeks. As a result of the audit a vigorous venous thrombosis prophylactic regimen has been instituted, and at Hackney the anaesthetic department has been strengthened and a new intensive care unit opened.

A study of the effect of povidone-iodine on polymorphonuclear leucocyte chemotaxis.

Studies were made of the effect of povidone-iodine on polymorphonuclear leucocyte chemotaxis. Polymorphonuclear leucocytes were incubated with various concentrations of povidone-iodine and allowed to migrate across a membrane towards a chemotactic agent. Chemotactic movement was found to decrease as the concentration of povidone-iodine rose, 75 micrograms/ml completely inhibiting all movement. A concentration of 10 micrograms/ml of povidone-iodine was found actively to repel the white cells. In vivo studies in mice showed a reduction in polymorphonuclear leucocytes at wound surfaces in the presence of povidone-iodine dry powder spray.

Acceptance and transfer of R-factor RP1 by members of the "herbicola" group of the genus Erwinia.

The R-factor RP1 was transferred by conjugation from Pseudomonas aeruginosa PAO12r(RPI) to various strains of Erwinia herbicola and to one strain of Erwinia stewartii. The exconjugate strains had minimum inhibitory concentration values for carbenicillin, kanamycin, neomycin, and tetracycline somewhat lower than the corresponding values for the pseudomonad RP1 donor strain. The biochemical characteristics of the exconjugant strains displayed minor variation in some instances from those of the corresponding R- strains. Sensitivity of the RP1+ strains to the RP1-specific bacteriophages PRD1 and PRR1 varied from an efficiency of plating [compared with P. aeruginosa PA067(RP1)] of 0 [E. herbicola Y46(RP1)] to 133 [E. herbicola Y190(RP1)] and 148 [E. stewartii SS104R(RP1)] for PRD1, and from 0 [E. herbicola Y46(RP1)] to 0.0002 [E. herbicola Y185(RP1)] and 18.4 [E. stewartii SS104R(RP1)] for PRR1. The phage-resistant strain E. herbicola Y46(RP1), would donate, by conjugation, the R-factor to E. herbicola Y46rifr, P, aeruginosa PAT900, or Escherichia coli UB1005 only at extremely low frequencies, if at all. Transformation of E. coli JC7620 by covalently closed circular DNA from E. herbicola Y46(RP1) gave and E. coli R+ strain exhibiting the expected antibiotic resistance pattern and having the ability to donate RP1 by conjugation. It is suggested (i) that some strains of E. herbicola RP1 either do not produce RP1 pili or produce defective pili, and (ii) that sensitivity to the bacteriophages PRD1 and PRR1 is not a suitable means of diagnosing the presence RP1 in E. herbicola strains.

Nurse therapists in behavioural psychotherapy.

Five registered mental nurses (R.M.N.s) were trained over two years to become behavioural psychotherapists for adult neurotic disorders. They achieved results comparable to those obtained with similar patients and methods by psychologists and psychiatrists. Similar results were maintained when over a third year the therapists were seconded to work in four hospitals and a general practice. Patients were satisfied at being treated by nurses. After initial teething difficulties nurse therapists became valuable members of treatment teams during both training and secondment, becoming accepted by most nurses, psychologists, and psychiatrists with whom they came into contact. The training of further nurse therapists would facilitate treatment of many disabled neurotics who would otherwise go without effective treatment. Training nurse therapists takes less time and money than training psychologists and psychiatrists because less of their education is redundant to the skills involved. The pool of R.M.N.s suitable for training is much larger than that of psychiatrists and psychologists. The nurse therapists can be integrated relatively easily into treatment teams. The present nursing structure imposes restrictions on the advancement of clinical nurse specialists and a clinical tree is badly needed parallel with present administrative and teaching hierarchies. An 18-month course in adult behavioural psychotherapy has been recognized by the Joint Board of Clinical Nursing Studies for England and Wales so that nurse therapists seem destined to be a lasting feature of future treatment teams.

Detection of a protein, similar to the sex pilus subunit, in the outer membrane of Escherichia coli cells carrying a derepressed F-like R factor.

The outer membranes of Escherichia coli K-12 cells carrying a derepressed F-like R factor contain about 7 times 10-4 molecules per cell of a protein similar to the subunit of the sex pili specified by the R factor. This protein pool is absent in cells carrying the repressed variant of the R factor. The size of the pool is about one-half of the amount of protein incorporated into mature sex pili at the peak of production and is independent of the phase of growth of the culture. The molecular weight of the protein in the pool and of the subunit of the sex pili specified by the cells is 12,500 plus or minus 600.