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W Fox

Publications and source records attributed to W Fox.

At least 19 recordsLinked to original sources
PubMed2005

Laser-induced fluorescence measurement of the ion-energy-distribution function in a collisionless reconnection experiment.

Observations in space and laboratory plasmas suggest magnetic reconnection as a mechanism for ion heating and formation of non-Maxwellian ion velocity distribution functions (IVDF). Laser-induced fluorescence measurements of the IVDF parallel to the X line of a periodically driven reconnection experiment are presented. A time-resolved analysis yields the evolution of the IVDF within a reconnection cycle. It is shown that reconnection causes a strong increase of the ion temperature, where the strongest increase is found at the maximum reconnection rate. Monte Carlo simulations demonstrate that ion heating is a consequence of the in-plane electric field that forms around the X line in response to reconnection.

Journal Article↗
PubMed2005

In situ discovery of an electrostatic potential, trapping electrons and mediating fast reconnection in the Earth's magnetotail.

Anisotropic electron phase space distributions, f, measured by the Wind spacecraft in a rare crossing of a diffusion region in Earth's far magnetotail (60 Earth radii), are analyzed. We use the measured f to probe the electrostatic and magnetic geometry of the diffusion region. For the first time, the presence of a strong electrostatic potential (1 kV) within the ion diffusion region is revealed. This potential has far reaching implications for the reconnection process; it accounts for the observed acceleration of the unmagnetized ions out of the reconnection region and it causes all thermal electrons be trapped electrostatically. The trapped electron motion implies that the thermal part of the electron distributions are symmetric around v( parallel)=0: f(v( parallel),v( perpendicular)) approximately f(-v( parallel),v( perpendicular)). It follows that the field aligned currents in the diffusion region are limited and fast magnetic reconnection is mediated.

Journal Article↗
PubMed1999

Prostate cancer cell cycle regulators: response to androgen withdrawal and development of androgen independence.

BACKGROUND: Androgen withdrawal is a standard therapy for prostate cancer that results in a decrease in tumor volume and a decline in serum prostate-specific antigen in the majority of patients. To understand the factors associated with regression of prostate cancers after androgen withdrawal, we studied cell cycle regulator changes in the CWR22 human prostate cancer xenograft model. METHODS: Established tumors in nude athymic BALB/c mice were sampled at various times after androgen withdrawal and after the development of androgen independence. Changes in the expression of cell cycle regulators were categorized into early and mid-to-late events. RESULTS AND CONCLUSIONS: Early events included a decrease in androgen receptor expression, followed by a short-term increase in expression of the p53 and p21/WAF1 proteins and a marked decrease in the Ki67 proliferative index. Mid-to-late events included progressive and sustained increases in p27 and p16 protein expression, a decrease in retinoblastoma protein expression, and an increase in the transcription factor E2F1. Changes in apoptosis (programmed cell death) were not observed at any time after androgen withdrawal. These data suggest that androgen withdrawal results in a cell stress response, in which increased p53 protein produces a cell cycle arrest, without activation of p53-mediated apoptosis. The proliferative index is further decreased through the action of the cyclin-dependent kinase inhibitors p27 and p16. Androgen-independent sublines emerged 80-400 days after androgen withdrawal, and these sublines had variable growth phenotypes but were associated with mdm2 protein overexpression and increased expression of cyclin D1. These results indicate that tumor regression in this human prostate cancer model is due to cell cycle arrest rather than to apoptosis and that the emergence of androgen independence is associated with a release from cell cycle arrest.

Androgens↗
PubMed1988

Controlled clinical trial of complete open surgical drainage and of prednisolone in treatment of tuberculous pericardial effusion in Transkei.

240 patients with active tuberculous pericardial effusion received a 4-drug daily antituberculosis regimen for 6 months and have been studied for 24 months or longer. Those willing were randomly allocated to open pericardial biopsy and complete drainage of pericardial fluid on admission or percutaneous pericardiocentesis as required. All patients were randomly allocated to prednisolone or matching placebo for the first 11 weeks, on a double-blind basis. Complete open drainage on admission abolished the need for pericardiocentesis (p less than 0.01) but did not influence the need for pericardiectomy for subsequent constriction or the risk of death. Among patients who did not have open drainage on admission, 2 (3%) of 76 given prednisolone compared with 10 (14%) of 74 given placebo died of pericarditis (p less than 0.05), 6 (8%) and 9 (12%) respectively required pericardiectomy, 7 (9%) and 17 (23%) repeat pericardiocentesis (p less than 0.05), and 3 (4%) and 7 (9%) open surgical drainage. By 24 months, apart from the 16 who died from pericarditis, all but 3 patients (2%) had a favourable status.

Adolescent↗
PubMed1987

Controlled trial of prednisolone as adjuvant in treatment of tuberculous constrictive pericarditis in Transkei.

In Transkei, 143 patients with active tuberculous constrictive pericarditis without significant pericardial effusion all received the same daily 6-month antituberculosis regimen of streptomycin, isoniazid, rifampicin, and pyrazinamide for 14 weeks followed by isoniazid and rifampicin. They were randomly allocated to receive in addition either prednisolone or placebo for the first 11 weeks; the comparison was double-blind throughout treatment and follow-up. In the 114 patients assessable up to 24 months, improvement was significantly more rapid in the prednisolone group, as shown by the rate of fall in the mean pulse rate and the rate at which jugular venous pressure and level of physical activity became normal. During follow-up, 2 (4%) of the 53 prednisolone and 7 (11%) of the 61 placebo patients died from pericarditis, and 11 (21%) and 18 (30%), respectively, required pericardiectomy. By 24 months 50 (94%) prednisolone and 52 (85%) placebo patients had a favourable status. 3 patients (1 prednisolone, 2 placebo) were normally active but were classified as not having achieved a favourable status. It is recommended that, in the absence of a specific contraindication, antituberculosis chemotherapy should be initially supplemented by steroids.

Adolescent↗
PubMed1987

A study of the use of maternity and child welfare clinics in case-finding for pulmonary tuberculosis in Kenya.

This investigation is the seventh in a series of case-finding studies in Kenya. It explores the potential value of questioning mothers attending maternity and child welfare (M & CW) clinics to identify tuberculosis suspects (individuals aged 6 years or more with a cough for 1 month or more or hemoptysis) living in their households. The study was carried out in all the eight M & CW clinics in two divisions (populations 86,000 and 112,000) of two different districts. The mothers were asked to give a standard letter, which explained the possible importance of a chronic cough, to each suspect they identified and invited the suspect to attend the district hospital chest clinic. Each suspect attending the clinic was entered in a special register and two sputum specimens were collected. For those who failed to attend, the specimens were collected at a home visit. Of the total of 342 suspects living in the two study areas who were registered at the M & CW clinics during 1 year, 261 were identified by the mothers but 19 denied having received the standard letter. The remaining 81 had not been identified by mothers but had attended the M & CW clinics on their own initiative. Of the 242 suspects who received the letter, 89 (39%) attended the hospital chest clinic, 74% within a week of the letter being issued from the M & CW clinic. The main reasons given for not attending the hospital chest clinic by the remaining suspects were financial or because their cough had improved or disappeared. Sputum was collected from 238 suspects and examined bacteriologically: in six (2.5%) it was positive for tubercle bacilli on smear and culture and in a further two (0.8%) the sputum was positive on culture only. Of those attending the hospital chest clinic 2.9% were smear- and culture-positive and 4.7% were culture positive. This method of case-finding has yielded disappointing results, for only 4% of the estimated annual incidence of smear-positive cases was detected.

Adult↗
PubMed1986

Changes in annual tuberculosis notification rates between 1978/79 and 1983 for the population of Indian subcontinent ethnic origin resident in England.

In two national surveys of tuberculosis notifications in England conducted in 1978/79 and 1983 the estimated annual notification rates for the Indian subcontinent (Indian, Pakistani, and Bangladeshi) ethnic groups were considerably higher than the rate for the white ethnic group. The mean annual decline in rates between the surveys appeared to be greater for the Indian and the Pakistani and Bangladeshi ethnic groups, 15% and 16% respectively, than for the white ethnic group (7%). Data from two small sample population surveys, the National Dwelling and Housing Survey in 1978 and the Labour Force Survey in 1983, were used to calculate the rates. However, comparison of the estimates for the population of Indian subcontinent ethnic origin in England from these surveys revealed discrepancies between them. Additional information from the Labour Force Survey on the year of first entry to the United Kingdom (UK) permitted the calculation of new estimates for the 1978 population, and based on these estimates the annual notification rates for 1978/79 were 287 per 100,000 for the Indian and 286 per 100,000 for the Pakistani and Bangladeshi ethnic groups. The rates for 1983 were 178 and 169 respectively, and the mean annual decline between the surveys was 11% for the Indian and 12% for the Pakistani and Bangladeshi ethnic groups. There were important changes in the characteristics of the population of Indian subcontinent ethnic origin in England between 1978 and 1983, and therefore the rates for both surveys have been standardised by the method of direct standardisation to a common reference population. Standardizing for year of entry to the UK, place of birth (UK or abroad), age, and sex reduced the mean annual decline in the notification rate to 4% for the Indian and 9% for the Pakistani and Bangladeshi ethnic groups. The much greater reduction in the rate of decline in the Indian ethnic group is due to the substantial decline between the surveys in the proportion of recent immigrants, the group with the highest annual notification rate, in that population. Future trends will continue to be influenced by immigration patterns, but it will also be important to monitor the rates among the increasing proportion of the population born in the UK or resident in England for more than five years.

Bangladesh↗
PubMed1986

[Results of a therapeutic trial comparing a 6-month regimen to a 12-month regimen in the treatment of pulmonary tuberculosis in the Algerian Sahara. Final report: results 3 years after the onset of treatment].

This study has compared a daily 6-month short-course chemotherapy regimen and a daily 12-month standard duration regimen in the treatment of smear positive pulmonary tuberculosis in a rural area of Algeria where the population contains a relatively high proportion of nomads. The 6-month regimen (6M) was isoniazid and rifampicin throughout with ethambutol and pyrazinamide in addition for the first 2 months, and the 12-month regimen (12M) was isoniazid and ethambutol supplemented by streptomycin during the first month. All the 601 patients admitted had one or more sputum smears positive on examination in the local laboratory and 70% had a positive culture in the reference laboratory in Algiers. Most patients were admitted to hospital initially for one or two months where chemotherapy was fully supervised and subsequently it was self-administered. In both nomads and settled residents known to have fully sensitive strains of tubercle bacilli pretreatment the 6-month regimen was highly effective with no failures during chemotherapy and only 3% relapses after stopping chemotherapy in 126 patients compared with a combined failure rate during chemotherapy and relapse rate of 21% in the 152 patients receiving the 12-month regimen (P less than 0.001). The results in patients with isoniazid-resistant strains pretreatment were also significantly better for the 6-month than for the 12-month regimen, one of 15 and 8 of 17 patients respectively being classified as failures or relapses (P = 0.03). To assess the results which might be achieved by these regimens under programme conditions the outcome at 3 years was also assessed in all patients admitted to the study irrespective of whether the disease was confirmed in the reference laboratory or at independent assessment and whether or not the allocated chemotherapy was modified or further courses of chemotherapy were given. At 3 years, 82% of the 6M and 80% of the 299 12M patients had achieved a favourable status and only one 6M patient and 4 12M patients were still known to have active disease with a positive culture. A further 23 6M and 22 12M patients were known to have died, 11 in each series probably or definitely from tuberculosis. The remaining 28 6M and 34 12M patients were lost from follow-up, but 24 and 22 respectively had completed their allocated chemotherapy before defaulting. It was estimated that, overall, 272 (94%) of the 6M and 263 (91%) of the 12M patients had a favourable status at 3 years.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1985

Studies of case-finding for pulmonary tuberculosis in outpatients at 4 district hospitals in Kenya.

This investigation is the sixth in a series of case-finding studies in Kenya. It explores the potential for case-finding by the identification of tuberculosis suspects (individuals with a cough for 1 month or more) through careful screening of general outpatients attending 4 district hospitals for the first time. Of 2299 suspects identified among 87 845 new outpatients attending the hospitals, 4.7% had culture-positive pulmonary tuberculosis, 3.6% having sputum positive on smear as well. In the 3 hospitals with radiographic facilities, 1.3% of suspects (whose sputum was negative on culture) were considered on review of their clinical history and chest radiograph by an independent assessor to have radiographically active tuberculous lesions and a further 2.5% to have inactive lesions. The proportion of bacteriologically positive cases per 1000 of the general population aged 6 years or more decreased as the distance of their homes from the hospital increased (P less than 0.001 for the trend). However, the proportion of cases per 1000 of the suspects identified increased as the distance of their homes from the hospital increased (P less than 0.001 for the trend). History of cough for between 1 and 12 months was the most useful factor for the identification of cases of tuberculosis among the suspects, and would have identified 92% of the smear-positive cases from the examination of 70% of the suspects; a history of weight loss identified 84% of the smear-positive cases from the examination of 64% of the suspects. A history of weight loss and/or a history of cough for between 1 and 12 months would have detected all the smear-positive cases from the examination of 89% of the suspects. The proportion of bacteriologically positive cases in the younger suspects aged 9-32 years (who had been eligible for a mass BCG campaign) was greater among the non-vaccinated than among the vaccinated suspects, 4.9% and 2.3% respectively (P=0.04), implying protection from vaccination of the order of 50%.

Adolescent↗
PubMed1985

Fifteen-year follow-up of all patients in a study of post-operative chemotherapy for bronchial carcinoma.

The 15-year findings are presented of a double-blind, randomised study planned in 1964 in which cytotoxic chemotherapy with either busulphan or cyclophosphamide prescribed to be given daily for 2 years as an adjuvant to surgery was compared with placebo in the treatment of 726 patients with carcinoma of the bronchus. The two cytotoxic agents administered in this way did not influence survival. At 15y, 8% of the 243 patients allocated busulphan, 9% of the 234 cyclophosphamide, and 10% of the 249 placebo were alive, these being 10% of the patients who had had epidermoid cancers, 12% large-cell, 5% small-cell, 5% adenocarcinomas, and 8% other histological types. The study provides data on long-term results in a large group of patients who were, in effect, treated by surgery alone. Survival was significantly shorter in patients with histological involvement of the resected intrathoracic nodes (log-rank test P much less than 0.001). A finding of particular interest is that the histological type of the tumour did not influence survival in the 390 patients whose nodes were not involved, although, as expected, it did in the 336 whose nodes were involved, the 226 with epidermoid cancers surviving longer than the 57 with small cell carcinoma, the 31 with adenocarcinoma and all 110 with non-epidermoid carcinomas (P much less than 0.001 in each comparison).

Aged↗