Trap-assisted tunnelling and Shockley-Read-Hall lifetime of extended defects in In.53Ga.47As p+n junction

Several In.53Ga.47As p+n junctions with various extended defect densities (EDDs) have been grown by metalorganic vapor phase epitaxy (MOVPE), by carefully controlling the growth conditions. After fabrication, T-dependent J-V, C-V and double DLTS (DDLTS) are performed to extract the electrical field dependence of the extended defect levels. From this characterization, it is derived that the extended defects dominate the electrical field enhancement factor Gamma regardless of the value of the EDD and significantly increases the leakage current under reverse bias (i.e., decrease the Shockley-Read-Hall lifetime). These impacts are strongly connected to a "band-like" density of states of extended defects E2 at E-C-0.32 eV by comparing the DDLTS and T-dependent J-V characteristics. On the other hand, the reference sample (without EDs) surprisingly exhibits an even stronger field dependence with lower leakage current. Nevertheless, no straightforward candidate point defects can be found in this sample and the possible explanation are discussed

Deep levels in silicon-oxygen superlattices

This work reports on the deep levels observed in Pt/Al2O3/p-type Si metal-oxide-semiconductor capacitors containing a silicon-oxygen superlattice (SL) by deep-level transient spectroscopy. It is shown that the presence of the SL gives rise to a broad band of hole traps occurring around the silicon mid gap, which is absent in reference samples with a silicon epitaxial layer. In addition, the density of states of the deep layers roughly scales with the number of SL periods for the as- deposited samples. Annealing in a forming gas atmosphere reduces the maximum concentration significantly, while the peak energy position shifts from close-to mid-gap towards the valence band edge. Based on the flat-band voltage shift of the Capacitance-Voltage characteristics it is inferred that positive charge is introduced by the oxygen atomic layers in the SL, indicating the donor nature of the underlying hole traps. In some cases, a minor peak associated with P-b dangling bond centers at the Si/SiO2 interface has been observed as well

Should baseline PSA testing be performed in men aged 40 to detect those aged 50 or less who are at risk of aggressive prostate cancer?

The original publication is available at http://www.samj.org.zaWe aimed to evaluate the presenting features and treatment outcome of prostate cancer in men aged <50 years, in a region where prostate specific antigen (PSA) screening is not readily available and most men present with symptoms. Methods. We analysed the data of 1 571 men with prostatic adenocarcinoma treated between January 1997 and December 2008 at our institution, a tertiary level public sector hospital serving a largely indigent population. Statistical analysis was performed using Student’s, the Mann-Whitney and Fisher’s exact tests where appropriate (p<0.05 accepted as statistically significant). Results. Of 1 571 men, 47 (3%) were aged <50 years. The group aged 50 years, had a significantly greater proportion with poorly differentiated adenocarcinoma (53%), locally advanced (stage T3 - 4) tumours (56%), haematogenous metastases (75%), significantly higher serum PSA at diagnosis (mean 621, median 74 ng/ml) and shorter survival. Conclusions. Men aged <50 years presenting with symptoms owing to prostate cancer had significantly higher-risk disease, higher mean PSA, and poorer prognosis than men aged >50 years. To diagnose prostate cancer at a potentially curable stage in men aged <50 years, it is necessary to initiate baseline PSA testing at age 40 and 45 years, and to select high-risk men for PSA surveillance in order to diagnose potentially curable cancer in those with a life expectancy >20 - 25 years.Publishers' Versio

Vasectomy under local anaesthesia performed free of charge as a family planning service: Complications and results

Objective. To evaluate the safety and efficacy of vasectomy performed under local anaesthesia by junior doctors at a secondary level hospital as part of a free family planning service.Method. Men requesting vasectomy were counselled and given written instructions to use alternative contraception until two semen analyses 3 and 4 months after vasectomy had confirmed azoospermia. Bilateral vasectomy was performed as an outpatient procedure under local anaesthesia by junior urology registrars. Statistical analysis was performed using the Mann-Whitney, Kruskal-Wallis, Fisher’s exact orSpearman’s rank correlation tests as appropriate.Results. Between January 2004 and December 2005, 479 men underwent vasectomy at Karl Bremer Hospital, Western Cape, South Africa; their average age was 36.1 (range 21 - 66) years, they had a median of 2 (range 0 - 10) children, and only 19% had 4 or more children. The average operation time was 15.5 (range 5 - 53) minutes. Complications occurred in 12.9%; these were pain (7.3%), swelling (5.4%), haematoma (1.3%), sepsis (1%), difficulty locating the vas (1%), vasovagal episode (0.6%), bleeding (0.6%), wound rupture (0.4%) and dysuria (0.2%) (some men had more than one complication). Of the men 63.3% returned for one semen analysis and 17.5% for a second. The vasectomy failure rate ranged from 0.4%(sperm persisting >365 days after vasectomy) to 2.3% (sperm seen >180 days after vasectomy and/or in the second semen specimen). No pregnancies were reported. The complication (5.6%) and failure rates (0%) were lowest for the registrar who had performed the smallest number of vasectomies and whose average operation time was longest. Comparing the first one-third of procedures performed by each of the doctors with the last one-third, there was a significant decrease inaverage operating times but not in complication rates.Conclusions. Vasectomy can be performed safely and effectively by junior doctors as an outpatient procedure under local anaesthesia, and should be actively promoted in South Africa as a safe and effective form of male contraception

The effect of sepsis and short-term exposure to nitrous oxide on the bone marrow and the metabolism of vitamin B 12 and folate

It is recognised that prolonged anaesthesia with nitrous oxide (N20) induces megaloblastic anaemia by oxidising vitamin B12 To determine whether sepsis aggravates the effect of H20 on haemopoiesis 5 patients with severe sepsis, who required surgery and were exposed to short-term (45 - 105 minutes) N20 anaesthesia, were studied. Hone had evidence of pre-operative vitamin B12 or folate deficiency. The effect of the combination of N20 anaesthesia and sepsis on DNA synthesis in bone marrow cells was assessed morphologically, and by the deoxyuridine suppression test. In 3 patients exposed to the longest duration (75 - 105 minutes) of N20, addition of folinic acid and vitamin B12 partially improved the utilisation of deoxyuridine in vitro. No patient had evidence of megaloblastic haemopoiesis as judged by bone marrow morphology. It is concluded that prolonged N20 anaesthesia in patients with severe sepsis may adversely affect DNA synthesis. Although this effect did not manifest as overt megaloblastic erythropoiesis, it may be prudent to avoid N20 in such patients

Serum prostate-specific antigen as surrogate for the Histological diagnosis of Prostate cancer

Introduction. To determine whether there is a cut-off value of serum prostate-specific antigen (PSA) which can be used confidently to make the diagnosis of prostate cancer, thereby obviating the need for biopsy.Patients and methods. During the period October 1991 to March 1998 the Department of Chemical Pathology at Tygerberg Hospital performed a total of 6 733 serum PSA assays on 3960 patients. The histopathological and clinical diagnoses of these patients were obtained from records in the departments of Anatomical Pathology, Urological Oncology and Radiation Oncology. The serum PSA levels were correlated with the histopathology reports, using different PSA cut-off values ranging from 5 to 500 ng/ ml, to calculate the sensitivity, specificity, and positive and negative predictive values of each cut-off value of PSA in predicting the presence of prostate cancer.Results. In total, 3 837 (57%) of the 6 733 serum PSA assays were ≤ 4 ng/ ml, 1 045 (15.5%) of the assays were ≥50 ng/ ml, and 798 (11.9%) were~ 100 ng/ ml. Of the total of 3 960 individual patients, 531 (13.4%) had a serum PSA ≥50 ng/ ml and 423 (10.7%) had a PSA ≥ 100 ng/ ml. A serum PSA of ≥ 30 ng/ml had a positive predictive value (PPV) of 90% at a specificity of 87% and sensitivity of 78%, while a PSA ≥ 60 ng/ ml had a PPV of 98% at a specificity of 98% and sensitivity of 65% for the presence of prostate cancer. The PPV reached 99% at a PSA ≥ 100 ng/ ml and 100% at a PSA ≥ 500 ng/ ml, with a specificity of 99% and 100%, but sensitivity of only 53% and 19%, respectively.Conclusions. A serum PSA ≥ 60 ng/ ml has a PPV of 98% for the presence of adenocarcinoma of the prostate, and may be used as a surrogate for histological diagnosis where facilities for obtaining prostatic biopsies are not readily available, thus decreasing costs and patient morbidity

Early diagnosis of prostate cancer in the Western Cape

Background. Early stage prostate cancer does not cause symptoms, and even metastatic disease may exist for years without causing symptoms or signs. Whereas early stage prostate cancer can be cured with radical prostatectomy or radiotherapy, the prognosis of patients with locally advanced or metastatic cancer is significantly poorer.Objectives. ln view of the high incidence of advanced and therefore incurable prostate cancer seen at the oncology clinic of the Department of Urology, Tygerberg Hospital, we started a prostate clinic with the aim of detecting early stage prostate cancer which is potentially curable. A secondary objective was to investigate the question whether there is a higher incidence of prostate cancer among black African men.Patients and methods. Men aged 50 - 70 years were invited by means of media communications (newspaper and radio) to attend our prostate clinic for a free physical examination, including a digital rectal examination (DRE) and serum prostate specific antigen (PSA) assay. If the DRE was clinically suspicious of malignancy and/ or the serum PSA was &gt; 4 ng/ ml, the patient was appropriately counselled and referred for transrectal ultrasound (TRUS)-guided sextant prostate biopsy.Results. In the period June 1997- September 1999 a total of 1056 men attended the prostate clinic. Biopsies were indicated in 160 cases, and were obtained in 114 (71.3%, i.e. 10.8% of the entire cohort). Prostate cancer was detected on first biopsy in 3.5% of the entire group of men (in 35.9% of those with a clinically abnormal DRE, in 41.3% of those with a serum PSA &gt; 4 ng/ ml and in 88.6% of those with an abnormal DRE and serum PSA &gt; 4 ng/ ml. In the 37 men with prostate cancer, the clinical tumour stage was T1 - 2 in 83.8% and T3- 4 in 16.2%. ln the group of patients with clinical stage T1 - 2 tumours, the treatment was watchful waiting in 62.5% of cases, radiotherapy in 20.8% and radical prostatectomy in 16.7%. Analysis of the data according to race showed that in the group of 47 black men there was a higher percentage of clinically abnormal DRE, PSA &gt; 4 .0 ng/ ml and biopsies showing malignancy, and a higher overall prostate cancer detection rate (8.5%).Conclusions. Our prostate cancer detection rate of 3.5% is slightly lower than that reported in larger studies (4.7%), which may be due to the fact that prostate biopsy was performed in only 71% of those who had an indication for biopsy. ln the men diagnosed with clinically localised prostate cancer, potentially curative treatment was given in only 37.5% of cases. This compares unfavourably with the historical cohort of men seen at our oncology clinic, where 53% received potentially curative treatment, and a large European study where potentially curative treatment was given in 89% of cases. Our finding that black men had a higher percentage of clinically abnormal DRE, PSA &gt; 4.0 ng/ ml and biopsies showing malignancy and a higher overall detection rate of prostate cancer should be interpreted with caution, since black men comprised only 4.5% of our overall study cohort.