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Biomedical subjects

W A Gillespie

Publications and source records attributed to W A Gillespie.

At least 19 recordsLinked to original sources
PubMed2006

Temporally resolved electro-optic effect.

The electro-optic effect between an ultrafast optical probe pulse and an ultrashort terahertz pulse is shown to depend on the time derivatives of the product of the probe and terahertz electric fields. Application of this theory to temporally resolved single-shot terahertz detection techniques, where the electro-optic effect is temporally localized within an optical probe pulse, shows that the description presented here differs fundamentally and verifiably from that commonly used in literature.

Journal Article↗
PubMed2004

Electro-optic technique with improved time resolution for real-time, nondestructive, single-shot measurements of femtosecond electron bunch profiles.

Electro-optic detection of the Coulomb field of a relativistic electron bunch combined with single-shot cross correlation of optical pulses is used to enable single-shot measurements of the shape and length of femtosecond electron bunches. This method overcomes a fundamental time-resolution limit of previous single-shot electro-optic measurements, which arises from the inseparability of time and frequency properties of the probing optical pulse. Using this new technique we have made real-time measurements of a 50 MeV electron bunch, observing the profile of 650 fs FWHM ( approximately 275 fs rms) long bunches.

Journal Article↗
PubMed2003

High-temporal-resolution, single-shot characterization of terahertz pulses.

A technique for noncollinear cross correlation of electro-optic modulated optical pulses is presented for the single-shot characterization of terahertz waveforms and is compared to established electro-optic terahertz characterization methods. This technique is free from the limitations on time resolution and faithful reproduction of previously demonstrated single-shot amplitude modulation spectral encoding.

Journal Article↗
PubMed2002

Single-shot electron-beam bunch length measurements.

We report subpicosecond electro-optic measurements of the length of individual relativistic electron bunches. The longitudinal electron-bunch shape is encoded electro-optically on to the spectrum of a chirped laser pulse. The electron-bunch length is determined by analyzing individual laser-pulse spectra obtained with and without the presence of an electron bunch. Since the length of the chirped laser pulse can be easily changed, the electron bunch can be visualized on different time scales. This single-shot imaging technique is a promising method for real-time electron-bunch diagnostics.

Journal Article↗
PubMed1989

Microbiology of the urethral (frequency and dysuria) syndrome. A controlled study with 5-year review.

In a clinical and microbiological study of women with urinary frequency and dysuria (excluding those with bacterial cystitis), 41 patients were compared with 42 control subjects. No difference was found between patients and controls in the incidence of infection by Chlamydia trachomatis or other sexually transmitted organisms. The numbers of lactobacilli and other fastidious organisms in the urine of patients with either mild or severe symptoms were similar and did not differ from the numbers in the urine of control subjects. The numbers of leucocytes in urine were also similar in both patients and controls. Our findings support the view that the urethral syndrome is not caused by bacterial or chlamydial infection.

Adult↗
PubMed1988

Bacteriuria and bacteraemia in patients with long-term indwelling catheters--a domiciliary study.

Men with indwelling catheters and men and women with suprapubic catheters were studied in their homes. Urine and blood were cultured and body temperature recorded after every catheter change. Nearly all patients had infected urine after 4 weeks of catheterisation, and all had bacteriuria after longer periods, usually with a mixture of organisms. Culture on selective media revealed a wider range of organisms than was detected on routine C.L.E.D. and blood agar with antibiotic sensitivity disks, but routine culture gave adequate information for clinical purposes. Bacteraemia was demonstrated after 20 of 197 changes of urethral catheter and after one of 19 changes of suprapubic catheter; but no patient had pyrexia or other symptoms. However, two had rigors on other occasions. When assessing "risk factors" for blood-stream infection in catheterised patients, it is important to record the total incidence of bacteraemia, asymptomatic as well as symptomatic.

Bacteria↗
PubMed1987

Bladder irrigation with chlorhexidine for the prevention of urinary infection after transurethral operations: a prospective controlled study.

The value of postoperative bladder irrigation with the antiseptic agent chlorhexidine was assessed in a randomized prospective controlled study of men after transurethral operations. In patients with sterile preoperative urine the incidence of postoperative bacteriuria was 12.8 per cent, compared to 36.7 per cent in control patients. The difference is significant (chi-square 5.54, p less than 0.02). On the other hand, chlorhexidine irrigation did not eliminate pre-existing infection. Small amounts of chlorhexidine were demonstrated in the blood of some patients. There was no evidence of damage to the bladder and no toxic side effects.

Administration, Intravesical↗
PubMed1984

Bacteraemia during prostatectomy and other transurethral operations: influence of timing of antibiotic administration.

The relation between the timing of prophylactic antibiotic administration and the occurrence of bacteraemia during transurethral operations was studied in 112 patients whose urine was infected before operation. Blood cultures taken during operation were positive in 15 (60%) of 25 patients who did not receive appropriate antibiotics, in 13 (21%) of 63 patients who were given appropriate antibiotics less than 24 h before operation, and in none of 24 patients in whom antibiotic "cover" was started more than 24 h before operation. In all cases the bacteraemia was transient. No patient developed septicaemia. The implications of these findings for the optimum timing of antibiotic administration to patients with preoperative bacteriuria are discussed.

Anti-Bacterial Agents↗
PubMed1983

Does the addition of disinfectant to urine drainage bags prevent infection in catheterised patients?

The value of adding chlorhexidine to urine drainage bags of male patients treated with indwelling catheters after prostatectomy and other transurethral operations was assessed in a randomised, prospective, controlled was assessed in a randomised, prospective, controlled study. Chlorhexidine kept the contents of all drainage bags sterile, but the frequency of urinary infection in the chlordexidine group (51%) did not differ significantly from that in the control group (45%). Most infections were endogenous, caused by organisms which probably came from the patient's own urethra. It was concluded that the method has no value in urology units where standards of catheter care and closed drainage are properly maintained. Controlled studies in other types of catheterised patients are needed, especially when the risks of cross-infection are high.

Catheters, Indwelling↗
PubMed1983

Septicemia after transurethral prostatectomy.

Septicemia occurred in 18 of 1,604 patients subjected to transurethral resection (TUR) of the prostate. Six patients died postoperatively, 4 of septicemia. In 11 patients septicemia was provoked by TUR in the presence of urinary infection and in the absence of appropriate antibiotic cover. Septicemia was provoked by catheter removal in 2 similarly infected patients. In the remaining 5 patients the urine was sterile at operation but became infected prior to catheter removal, and this maneuver precipitated septicemia.

Humans↗
PubMed1983

Antimicrobial agents for the prevention of urinary tract infection in transurethral surgery.

Chemoprophylaxis and disinfection of the operation site for the prevention of bacteriuria after a transurethral operation were assessed in controlled, prospective studies in men with sterile urine preoperatively. The majority of the control patients (65 per cent) suffered postoperative bacteriuria compared to 38.6 per cent after perioperative disinfection with chlorhexidine and 10 per cent or less after each of 2 other regimens (intramuscular cephradine followed by oral nitrofurantoin and chlorhexidine disinfection followed by oral nitrofurantoin). The latter regimen is preferred since it avoids the use of agents with systemic action.

Aged↗