PubMed Health⌕ Search

Biomedical subjects

A A Naqvi

Publications and source records attributed to A A Naqvi.

9 recordsLinked to original sources
PubMed2006

Performance improvement of keV Neutrons-based PGNAA setups.

The performance of keV neutrons based Prompt Gamma Ray Neutron Activation Analysis (PGNAA) setups have been observed to improve by enclosing its neutron source inside the moderator. The keV neutrons were produced via (7)Li(p,n) reaction and (3)H(p,n) reactions. For the two PGNAA setups, the maximum intensity of the prompt gamma-ray yield was observed for a 5cm long moderator with the neutron source positioned at a distance of 0.5cm from the moderator-end facing the sample. Due to enclosing the source inside the moderator, the prompt gamma-ray yield from the (7)Li(p,n) reaction and (3)H(p,n) reaction based PGNAA setups have increased by a factor of three as compared to that achieved from these setups with the source outside the moderator. This study provides a theoretical basis for the measurement of performance of (7)Li(p,n) reaction and the (3)H(p,n) reaction based PGNAA setups.

Journal Article↗
PubMed2005

Prompt gamma analysis of chlorine in concrete for corrosion study.

Measurement of chlorine in concrete is very important for studying of corrosion of reinforcing steel in concrete. Corrosion of reinforcing steel is primarily ascribed to the penetration of chloride ions to the steel surface. Preventive measures for avoiding concrete structure reinforcement corrosion requires monitoring the chloride ion concentration in concrete so that its concentration does not exceed a threshold limit to initiate reinforcement concrete corrosion. An accelerator based prompt gamma neutron activation analysis (PGNAA) setup has been developed for non-destructive analysis of elemental composition of concrete samples. The setup has been used to measure chlorine concentration in concrete samples over a 1-3 wt% concentration range. Although a strong interference has been observed between the chlorine gamma-rays and calcium gamma-rays from concrete, the chlorine concentration in concrete samples has been successfully measured using the 1.164 and 7.643 MeV chlorine gamma-rays. The experimental data were compared with the results of the Monte Carlo simulations. An excellent agreement has been achieved between the experimental data and results of Monte Carlo simulations. The study has demonstrated the successful use of the accelerator-based PGNAA setup in non-destructive analysis of chlorine in concrete samples.

Journal Article↗
PubMed2005

Use of 7Li(p,n) reaction as a neutron source in a PGNAA setup.

The performance of a 7Li(p,n) reaction-based Prompt Gamma Ray Neutron Activation Analysis (PGNAA) setup has been determined for analysis of Portland cement samples using Monte Carlo study. The calculations were carried out for a 7Li(p,n) reaction-based PGNAA setup with an external moderator similar to the one used in a previous 2.8 MeV neutrons-based PGNAA setup. The optimum values of geometry parameters of the 7Li(p,n) reaction-based setup are different from those of the 2.8 MeV neutrons-based setup resulting in better performance of the 7Li(p,n) reaction-based setup. The prompt gamma-ray yield from the 7Li(p,n) reaction-based setup is 60-70% higher than that from the 2.8 MeV neutrons-based setup. Although the performances of the 7Li(p,n) reaction-based setup is comparable with that of a previously studied 3H(p,n) reaction-based setup, yet performance of the 7Li(p,n) reaction-based setup is superior to that of the 3H(p,n) reaction-based setup because it has less radiation hazard due to utilization of non-radioactive neutron producing target. This study has provided a theoretical base for experimental test of a 7Li(p,n) reaction-based PGNAA setup.

Journal Article↗
PubMed2003

Performance tests of external moderators of a PGNAA setup.

Performance tests of external cylindrical moderators of an accelerator-based prompt gamma ray neutron activation analysis (PGNAA) setup have been carried out through thermal neutrons and prompt gamma-ray yield measurements. The PGNAA setup is to be used for analysis of cement samples. This study was conducted to investigate the effects of geometry of cylindrical moderator on yield of thermal neutrons and prompt gamma-rays for two different types of moderator assemblies. One of the moderators was to be used with a small sample and the other to be used with a large sample. Fast and thermal neutron yield was measured inside the sample volume as a function of the front moderator thickness as well as sample length. Neutron yield measurement was carried out at the King Fahd University of Petroleum and Minerals 350 keV pulsed beam accelerator using nuclear track detectors. The pulsed 200 keV deuteron beam with 5 ns pulse width and 31.25 kHz frequency was used to produce 2.8 MeV neutrons via D(d,n) reaction. Neutron yield measurements showed that the large sample moderator has a smaller yield of thermal neutrons as compared to the small sample moderator, which is in complete agreement with the results of Monte Carlo yield calculations of the thermal and fast neutrons from both the moderators. Finally, the prompt gamma-ray yield from a Portland cement sample was measured using the two moderators and was compared with each other. As predicted by Monte Carlo simulations, in spite of a smaller yield of thermal neutrons, the large sample moderator has a higher yield of prompt gamma-rays.

Journal Article↗
PubMed1995

Analysis of known risk factors for bladder cancer in Pakistani population.

The association of aetiological agents incriminated for bladder cancer are well recognised. They are divided into two groups, occupational and non-occupational. The commonest occupational agents are 2-naphthylamine, benzidine, aminobiphenyl, dichlorobenzidine, orthodianisidine and orthotolidine. Recognised non-occupational agents include tobacco, recurrent chronic bladder infection/infestation, coffee and drugs. This study was conducted to evaluate these factors in patients with bladder cancer in our population. Of 250 cases studied, 203 were males and 47 females with a male to female ratio of 4.3:1. In 13.6% cases occupational factors were established with an average duration of exposure of 12 years. Majority (68%) of patients had smoking as the predominant non-occupational factor. In this group average cigarettes smoked per day was 23 with a range of 15 to 90. The duration of smoking ranged between 5 to 55 years with an average of 26 years. Sixty patients (24%) were neither smokers nor had any associated high risk occupation.

Adolescent↗
PubMed1995

Pneumatic lithotripsy: a new modality for treatment of ureteric stones.

Two hundred and twenty ureteric stones in 214 patients were fragmented intracorporeally by pneumatic lithotripsy under general/regional anaesthesia in a day care set-up. Patients were followed-up weekly and retreatment was done at 4 weeks where necessary. Majority (77%) of patients were in the age group 21-40 years with a male to female ratio of 2:1. Stone location was 86% in the lower third, 11% in the middle and 3% in the upper third ureter. Size of stones was less than 6 mm in 14%, 7-12 mm in 67% and more than 20 mm in 4% cases. All 81% stones of < 12 mm were fragmented in one treatment session while single treatment rate for stones 13-18 mm was 85% and 44% for more than 20 mm size. Overall non-fragmentation rate was 0.9%. Stone free state at four weeks was 95%. Complications were observed in 8.6% cases which included urosepsis, haematuria and perforations. Infrared spectroscopy (IR) in 45 stones showed majority (64%) to be composed of calcium oxalate. Our experience shows that PL is a safe and effective means of performing intracorporeal lithotripsy for both large and hard ureteric stones.

Adult↗
PubMed1986

Schinus molle: a new source of natural fungitoxicant.

The oil of Schinus molle exhibited the maximum fungitoxic activity during the screening of some essential oils against some common storage and animal pathogenic fungi. It showed absolute toxicity against animal pathogens and mild activity against storage fungi. The effective concentrations of the oil varied from 200 to 900 ppm. The toxicity of the oil persisted up to 80 degrees C and 90 days of storage but declined when autoclaved. It withstood heavy inoculum density. The oil exhibited a narrow range of activity and was found to be more effective than Multifungin, an antifungal drug. The oil was characterized by its various physicochemical properties. It was found to comprise 50 constituents. It appeared that some changes in the oil constituents during storage affected its fungitoxic potency.

Antifungal Agents↗