Yb:YAG and Nd:YAG edge-pumped slab lasers.

Experimental demonstrations of two edge-pumped zigzag slab lasers are presented. The Nd:YAG slab laser generated 127 W of multimode output power with 300W of pump power. Preliminary results with a Yb:YAG slab produced 46 W of output power with 315W of pump power. The edge-pumped slab design permits symmetric conduction cooling and efficient pump absorption and accepts large-numerical-aperture pump sources.

Quantum noise in a continuous-wave laser-diode-pumped Nd:YAG linear optical amplifier.

We present measurements of the power noise that is due to optical amplification in a laser-diode-pumped Nd:YAG free-space traveling-wave linear amplifier in a master-oscillator-power-amplifier configuration. The quantum noise behavior of the optical amplifier was demonstrated by use of InGaAs photodetectors in a balanced detection configuration, at a total photocurrent of 100 mA and in a frequency band from 6.25 to 15.625 MHz. The experimental results are in good agreement with predictions.

Modeling of quasi-three-level lasers and operation of cw Yb:YAG lasers.

We present modeling studies of quasi-three-level laser oscillators, the validity of which was revealed by Ti:Al(2)O(3)-pumped Yb:YAG laser experiments, and these results are shown to be in excellent agreement with the theory. As much as 75% slope efficiency was obtained with a hemispherical laser cavity. Previous modeling calculations of laser performance have been valid only for certain special cases, restricting application to TEM(00) Gaussian beam pumping and lasing profiles. This analysis may be applied to other longitudinally pumped quasi-three-level laser media in which the modes are not only TEM(00) Gaussian beams but also other higher-order transverse modes, including the top-hat pumping profile that can be used to model transverse pumping schemes.

42%-efficient single-pass cw second-harmonic generation in periodically poled lithium niobate.

We present a full-wafer fabrication process for periodically poled lithium niobate with a 6.5-mum domain period. Samples that were 53 mm long and 0.5 mm thick were obtained with this process for single-pass cw 1064-nm Nd:YAG second-harmonic generation. These samples exhibited 78% of the ideal nonlinear coefficient, had a measured conversion efficiency of 8.5% /W in the low-power limit, and produced 2.7 W of cw 532-nm output with 6.5 W of cw input, which corresponds to 42% power conversion efficiency.

An outbreak of waterborne cryptosporidiosis caused by post-treatment contamination.

An outbreak of waterborne cryptosporidiosis affecting 27 persons, diagnosed stool positive, occurred in Ayrshire in April 1988. Twenty-one in 27 confirmed cases required some form of fluid replacement therapy. Local general practitioners indicated a two- to fivefold increase in diarrhoeal disease during the outbreak, and following enquiries made by Environmental Health Officers it became apparent that many hundreds of people had suffered a diarrhoeal illness at that time. Cryptosporidium spp. oocysts were detected in the treated chlorinated water supply system, in the absence of faecal bacterial indicators. Oocyst contamination of a break-pressure tank containing final water for distribution was the cause of this waterborne outbreak. An irregular seepage of oocyst-containing water, which increased during heavy rains, was the cause of the break-pressure tank contamination, rather than a failure of the water-treatment processes. The waterborne route should be considered when clusters of cryptosporidiosis-associated with potable water occur. Waterborne cryptosporidiosis can occur in the absence of other faecal indicators of contamination.

Recent observations on the ultrastructure of human urothelium. 1. Normal bladder of elderly subjects.

An electron microscopic study of normal bladder urothelium of elderly patients ranging in age from 61 to 82 years has shown the occurrence of unusually thin regions consisting of either one or two layers of undifferentiated cells interspersed between 3--4 cell layers thick regions. A morphometric study has confirmed the existence of a pattern of cytodifferentiation in cells of the thick region. The generally microvillous nature of the luminal surface is attributed to incompletely differentiated cells that have come to occupy the superficial layer. The lack of thickened and/or asymmetric membrane plaques in luminal plasma as well as the dearth of characteristic precursor vesicles in the cytoplasm are also explicable in terms of a failure of normal cell differentiation. It is suggested that the unusual features noted are consequences of tissue ageing rather than prognostic of cancer. There are indications that the aged urothelium may be prone to increased leakiness and the bladder tissues may therefore be at greater risk from urine-borne chemicals and carcinogens.

Herpes zoster with dysfunction of bladder and anus.

Herpes zoster may give rise to dysfunction of bladder and anus. Mucosal lesions have been reported, and 7 cases are described with retention, loss of sensation, or incontinence. Sacral shingles is associated with sensory loss and flaccid detrusor paralysis. Lumbar shingles may cause retention, and zoster at higher levels can also damage the spinal cord. Recovery is usually complete. The implication for schemes of bladder innervation is discussed.

Conservative management of renal tuberculosis.

The conservative management of 60 patients suffering from renal tuberculosis is reported. Following chemotherapy, bacteriological conversion to negative was obtained in all patients. 2 patients (3-3%) relapsed due to failure to take adequate treatment. Evidence of ureteric obstruction was obtained in 30 patients (50%)--23 at the time of diagnosis, 6 during treatment and 1 at the time of relapse. Following corticosteroid treatment relief of obstruction was obtained in 72%. Nephrectomy was carried out in 4 patients (6-7%) but in only 1 of these was the operation carried out for reasons which we now consider valid.

Hyperthermic perfusion of the distended urinary bladder in the management of recurrent transitional cell carcinoma.

The clinical and histological changes following hyperthermic perfusion of the distended urinary bladder have been studied in 13 patients with transitional cell carcinoma, persistent after radical radiotherapy. Continuous epidural anaesthesia was necessary to achieve a constant state of bladder relaxation during irrigation of the distended bladder. This form of hyperthermic perfusion of the bladder was effective in arresting uncontrollable haemorrhage from bladder tumours and may be of value in the treatment of this complication. Perfusion at an outflow temperature of 44 degrees C for 4 hours caused tumour necrosis. It was, however, associated with damage to the vasculature of the bladder and frequency of micturition which persisted after mucosal recovery. Perfusion at 43 degrees C also caused tumour necrosis and the after effects were less severe.