Biomedical subjects

F I Khan

Publications and source records attributed to F I Khan.

9 recordsLinked to original sources

PubMed2002

Effects of subthalamic nucleus stimulation on motor cortex excitability in Parkinson's disease.

BACKGROUND: Transcranial magnetic stimulation (TMS) studies have found abnormalities in several excitatory and inhibitory circuits in the motor cortex in PD. These include motor evoked potential (MEP) recruitment curve, silent period duration (SP), short-interval intracortical inhibition (SICI), intracortical facilitation (ICF), and long-interval intracortical inhibition (LICI). METHODS: The authors studied the effects of subthalamic nucleus (STN) deep brain stimulation (DBS) on these circuits in 12 patients with PD treated with STN DBS. Data from nine patients who completed the study were analyzed. Patients remained on their usual medications. The stimulators were set at the optimal parameters (ON), half the optimal amplitude (HALF), and switched off (OFF) in random order. RESULTS: The Unified PD Rating Scale motor scores were significantly lower in the ON compared to the HALF and OFF conditions. Resting SICI, studied with paired-pulse TMS at interstimulus interval of 2 ms, was reduced in the OFF and HALF conditions compared to normal subjects. STN stimulation restored SICI to normal levels. STN stimulation had no effect on motor threshold, MEP recruitment curve, SP, active SICI, ICF, and LICI. CONCLUSIONS: Although restoration of short-interval intracortical inhibition by STN stimulation is similar to the effects of dopaminergic drugs, it has no effect on silent period duration and long-interval intracortical inhibition, which are also influenced by dopaminergic drugs. A previous study found that internal globus pallidus (GPi) stimulation reduced SP but did not change SICI. Thus, GPi and STN stimulation may affect different circuits in the motor cortex.

Adult↗

PubMed2002

Design of greenbelt for an industrial complex based on mathematical modelling.

Greenbelt is a strip of vegetation for which species of trees and shrubs are scientifically chosen and planted to serve a designated purpose such as control of wind erosion, of dust, of noise etc. In the context of air pollution attenuation, greenbelts must be developed around a source of air pollutant in a manner so as to effectively reduce the pollution caused by that source. Design of effective greenbelts involves consideration of meteorological, physico-chemical, biological, and horticultural aspects relevant to pollutant source and the area where greenbelt has to be established. These authors have recently developed mathematical models for effective design of greenbelts. This paper presents an overview of the methodology based on the models, and describes a case study in which the methodology has been applied to design a greenbelt for a real-life situation.

Air Pollution↗

PubMed2002

Modelling of Buckingham Canal water quality.

The paper presents a case study of the modelling of the water quality of a canal situated in a petrochemical industrial complex, which receives wastewaters from Madras Refineries Limited (MRL), and Madras Fertilizers Limited (MFL). The canal well known Buckingham Canal which passes through Chennai (Madras), India has been modelled using the software QUAL2E-UNCAS. After testing and validation of the model, simulations have been carried out. The exercise enables forecasting the impacts of different seasons, base flows, and waste water inputs on the water quality of the Buckingham Canal. It also enables development of water management strategies.

Chemical Industry↗

PubMed2001

SCAP: a new methodology for safety management based on feedback from credible accident-probabilistic fault tree analysis system.

As it is conventionally done, strategies for incorporating accident--prevention measures in any hazardous chemical process industry are developed on the basis of input from risk assessment. However, the two steps-- risk assessment and hazard reduction (or safety) measures--are not linked interactively in the existing methodologies. This prevents a quantitative assessment of the impacts of safety measures on risk control. We have made an attempt to develop a methodology in which risk assessment steps are interactively linked with implementation of safety measures. The resultant system tells us the extent of reduction of risk by each successive safety measure. It also tells based on sophisticated maximum credible accident analysis (MCAA) and probabilistic fault tree analysis (PFTA) whether a given unit can ever be made 'safe'. The application of the methodology has been illustrated with a case study.

Accident Prevention↗

PubMed2001

Risk-based monitored natural attenuation--a case study.

The term "monitored natural attenuation" (MNA) refers to a reliance on natural attenuation (NA) processes for remediation through the careful monitoring of the behavior of a contaminant source in time and space domains. In recent years, policymakers are shifting to a risk-based approach where site characteristics are measured against the potential risk to human health and the environment, and site management strategies are prioritized to be commensurate with that risk. Risk-based corrective action (RBCA), a concept developed by the American Society for Testing Materials (ASTM), was the first indication of how this approach could be used in the development of remediation strategies. This paper, which links ASTM's RBCA approach with MNA, develops a systematic working methodology for a risk-based site evaluation and remediation through NA. The methodology is comprised of seven steps, with the first five steps intended to evaluate site characteristics and the feasibility of NA. If NA is effective, then the last two steps will guide the development of a long-term monitoring plan and approval for a site closure. This methodology is used to evaluate a site contaminated with oil from a pipeline spill. The case study concluded that the site has the requisite characteristics for NA, but it would take more than 80 years for attenuation of xylene and ethylbenzene, as these chemicals appear in the pure phase. If fast remediation is sought, then efforts should be made to remove the contaminant from the soil. Initially, the site posed a serious risk to both on-site and off-site receptors, but it becomes acceptable after 20 years, as the plume is diluted and drifts from its source of origin.

Decision Making↗

PubMed2001

Effective design of greenbelts using mathematical models.

Trees, shrubs, and other vegetation can absorb and assimilate certain air pollutants if the pollutants are present within tolerable levels. This concept is being increasingly used in developing strips of vegetation, often called 'greenbelts' around sources of pollution. But several intricacies are associated with the exercise of effective and optimal designing of greenbelts. The pattern of dispersion of air pollutants, as effected by the density of the gaseous plume and the meteorology of the area, must be studied with great precision because these aspects would determine the location and the geometry of the greenbelt. The species composition in the greenbelt should confirm to the pollutants to be attenuated as to the geoclimatic conditions of the region. Decisions on the tree heights, and the sequence of plantation of trees and other vegetation also similarly require complex inputs. In this paper, the authors have addressed these issues and have presented a set of mathematical models, which may help in the rational and optimal design of greenbelts.

Air Pollution↗

PubMed2000

Modelling and simulation of heavy gas dispersion on the basis of modifications in plume path theory.

An analytical model for heavy gas dispersion based on the modifications in plume path theory has been developed. The model takes into account the variations in temperature, density, and specific heat during the movement of heavy gas plume. The model has been tested for three hazardous gases - chlorine, natural gas and liquefied petroleum gas. The results have been compared with the recently generated experimental data as also with the outputs of other models. A good agreement is observed qualitatively as well as quantitatively. A study has also been carried out to simulate the effect of the wind speed, density of the gas, and venting speed on dispersion. Based on the simulation study a set of empirical equations has been developed. The equations are validated by theoretical as well as experimental studies.

Air Movements↗

PubMed2000

Analytical simulation and PROFAT II: a new methodology and a computer automated tool for fault tree analysis in chemical process industries.

Fault tree analysis (FTA) is based on constructing a hypothetical tree of base events (initiating events) branching into numerous other sub-events, propagating the fault and eventually leading to the top event (accident). It has been a powerful technique used traditionally in identifying hazards in nuclear installations and power industries. As the systematic articulation of the fault tree is associated with assigning probabilities to each fault, the exercise is also sometimes called probabilistic risk assessment. But powerful as this technique is, it is also very cumbersome and costly, limiting its area of application. We have developed a new algorithm based on analytical simulation (named as AS-II), which makes the application of FTA simpler, quicker, and cheaper; thus opening up the possibility of its wider use in risk assessment in chemical process industries. Based on the methodology we have developed a computer-automated tool. The details are presented in this paper.

Chemical Industry↗

PubMed1993

MMPI-2 profiles of battered women in transition.

Domestic violence is a widespread problem in our society that has not been extensively studied using psychological assessment tools. In this investigation, the psychological functioning of battered women in transition was examined through the use of the Minnesota Multiphasic Personality Inventory-2 (MMPI-2). Thirty-one women (M age = 30 years, M education = 11.5 years) were evaluated as residents in a confidential shelter operated by Women Against Abuse. All subjects were asked to complete the MMPI-2 as well as information on their history of length, severity, and types of abuse (i.e., physical and/or psychological). Results indicated elevated MMPI-2 profiles in 90% of the subjects with the most frequent code type being a combination of Scales F, 4, 6, and 8. Scales 2 and 7, which are often associated with depression, anxiety, and other forms of subjective distress, were not consistently elevated. Supplementary MMPI-2 scales revealed elevations on scales MAC-R, Mt, PK, and PS. Regression analysis indicated significant relationships between length and severity of psychological forms of abuse and overall levels of psychological distress (i.e., F scale and average clinical T-score). Age and physical forms of abuse were not related to MMPI indices of psychological disturbance. Theoretical issues of domestic violence, intervention strategies with battered women, and the dangers of misdiagnosis are discussed.

Adult↗