Recently, reliability analysis has been advocated as an effective approach to account for uncerta... more Recently, reliability analysis has been advocated as an effective approach to account for uncertainty in the geometric design process and to evaluate the risk associated with a particular design. In this approach, a risk measure (e.g. probability of noncompliance) is calculated to represent the probability that a specific design would not meet standard requirements. The majority of previous applications of reliability analysis in geometric design focused on evaluating the probability of noncompliance for only one mode of noncompliance such as insufficient sight distance. However, in many design situations, more than one mode of noncompliance may be present (e.g. insufficient sight distance and vehicle skidding at horizontal curves). In these situations, utilizing a multi-mode reliability approach that considers more than one failure (noncompliance) mode is required. The main objective of this paper is to demonstrate the application of multi-mode (system) reliability analysis to the design of horizontal curves. The process is demonstrated by a case study of Sea-to-Sky Highway located between Vancouver and Whistler, in southern British Columbia, Canada. Two noncompliance modes were considered: insufficient sight distance and vehicle skidding. The results show the importance of accounting for several noncompliance modes in the reliability model. The system reliability concept could be used in future studies to calibrate the design of various design elements in order to achieve consistent safety levels based on all possible modes of noncompliance.
Several studies have investigated the relationship between field-measured conflicts and the confl... more Several studies have investigated the relationship between field-measured conflicts and the conflicts obtained from micro-simulation models using the Surrogate Safety Assessment Model (SSAM). Results from recent studies have shown that while reasonable correlation between simulated and real traffic conflicts can be obtained especially after proper calibration, more work is still needed to confirm that simulated conflicts provide safety measures beyond what can be expected from exposure. As well, the results have emphasized that using micro-simulation model to evaluate safety without proper model calibration should be avoided. The calibration process adjusts relevant simulation parameters to maximize the correlation between field-measured and simulated conflicts. The main objective of this study is to investigate the transferability of calibrated parameters of the traffic simulation model (VISSIM) for safety analysis between different sites. The main purpose is to examine whether the calibrated parameters, when applied to other sites, give reasonable results in terms of the correlation between the field-measured and the simulated conflicts. Eighty-three hours of video data from two signalized intersections in Surrey, BC were used in this study. Automated video-based computer vision techniques were used to extract vehicle trajectories and identify field-measured rear-end conflicts. Calibrated VISSIM parameters obtained from the first intersection which maximized the correlation between simulated and field-observed conflicts were used to estimate traffic conflicts at the second intersection and to compare the results to parameters optimized specifically for the second intersection. The results show that the VISSIM parameters are generally transferable between the two locations as the transferred parameters provided better correlation between simulated and field-measured conflicts than using the default VISSIM parameters. Of the six VISSIM parameters identified as important for the safety analysis, two parameters were directly transferable, three parameters were transferable to some degree, and one parameter was not transferable.
Middle East Journal of Anaesthesiology, Jun 1, 2005
Thymectomy is an established therapy in the management of generalized myasthenia gravis (MG). How... more Thymectomy is an established therapy in the management of generalized myasthenia gravis (MG). However, the optimal surgical approach to thymectomy has remained controversial. There are advocates for transternal, transcervical approaches for "maximal" thymectomy. Video-assisted thoracoscopic thymectomy (VATT) presents new approach to thymectomy. By minimizing chest wall trauma, VATT not only causes less postoperative pain, shortens hospital stay, gives better cosmetic results but also leads to wider acceptance by patients for earlier surgery. Anesthesia for thymectomy in MG is challenging. Currently we are using non-muscle relaxant technique (NMRT) which we adopted in 1994, for maximal thymectomy. In this paper, we present our limited experience with two cases of VATT using two different NMRTs. Two cases of MG underwent VATT under general anesthesia (GA) and one lung ventilation (OLV) using double lumen tube (DLT). In both cases NMRT was used which encompass, light GA plus thoracic epidural analgesia (TEA) in one case and without TEA in the other case. We believe that the use of NMRT provides good operative and postoperative conditions. In this report we have described two different NMRTs, one with TEA and the other without. Further studies are needed on large number of cases to establish an anesthetic protocol for VATT.
We report two cases of unusual presentation of rib exostosis. The first patient presented acutely... more We report two cases of unusual presentation of rib exostosis. The first patient presented acutely with hemorrhagic shock due to massive hemothorax, and the second patient presented with repetitive chest infection complicated by empyema. In both patients, preoperative computed tomographic (CT) scan of the chest revealed rib exostoses, necessitating thoracotomy and rib resection.
Melatonin, the principle hormone of pineal gland plays an important role in several biological pr... more Melatonin, the principle hormone of pineal gland plays an important role in several biological processes. The effects of melatonin on hepatic marker enzymes [aspartate and alanine transaminases (AST and ALT)], lipid peroxides [thiobarbituric acid reactive substances (TBARS)] and antioxidants [reduced glutathione (GSH), glutathione peroxidase (GPx) and glutathione-S-transferase (GST)] during N-nitrosodiethylamine (NDEA)-induced hepatocarcinogenesis in rats were studied. Male albino Wistar rats of body weight 150-170 g were divided into four groups of six animals each. Group I animals served as control, Group II animals received single intraperitoneal injection of NDEA at a dose of 200 mg/kg body weight followed by weekly subcutaneous injections of CCl4 at a dose of 3 mL/kg body weight. Group III animals were treated as in Group II and melatonin (5 mg/kg body weight) was administered intraperitoneally. Group IV animals received melatonin alone at the same dose as Group III animals. A ...
Thymectomy is an established therapy in the management of generalized myasthenia gravis (MG). How... more Thymectomy is an established therapy in the management of generalized myasthenia gravis (MG). However, the optimal surgical approach to thymectomy has remained controversial. There are advocates for transternal, transcervical approaches for "maximal" thymectomy. Video-assisted thoracoscopic thymectomy (VATT) presents new approach to thymectomy. By minimizing chest wall trauma, VATT not only causes less postoperative pain, shortens hospital stay, gives better cosmetic results but also leads to wider acceptance by patients for earlier surgery. Anesthesia for thymectomy in MG is challenging. Currently we are using non-muscle relaxant technique (NMRT) which we adopted in 1994, for maximal thymectomy. In this paper, we present our limited experience with two cases of VATT using two different NMRTs. Two cases of MG underwent VATT under general anesthesia (GA) and one lung ventilation (OLV) using double lumen tube (DLT). In both cases NMRT was used which encompass, light GA plus ...
The present investigation was designed to study the protective role of Pongamia pinnata (an indig... more The present investigation was designed to study the protective role of Pongamia pinnata (an indigenous plant used in Ayurvedic medicine in India) leaf extract on oxidative stress during ammonium chloride-induced hyperammonemia by measuring the extent of oxidative damage as well as antioxidant status. Ethanolic extract of Pongamia pinnata (PPEt) leaves was administered orally (300 mg/kg body weight) and the effects of PPEt on the levels of thiobarbituric acid reactive substances (TBARS), hydroperoxides (HP), conjugated diene (CD), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and reduced glutathione (GSH) were studied in liver and kidney of ammonium chloride-induced hyperammonemic rats. On treatment with PPEt, a significant reduction in the levels of TBARS, HP, and CD and a significant increase in the levels of SOD, CAT, GPx, and GSH in liver and kidney of ammonium chloride-induced hyperammonemic rats were observed, which clearly shows the antioxidant property of PPEt. The study of induction of the antioxidant status is considered to be a reliable marker for evaluating the antiperoxidative effect of the medicinal plant. Our present findings show the protective role of PPEt against lipid peroxidation and suggest that PPEt possesses antioxidant potential that may be used for therapeutic purposes. The exact mechanism has to be still investigated and the isolation of active constituents is required.
ABSTRACT Tumors and tumor-bearing hosts exhibit markedly altered circadian rhythms, which serve a... more ABSTRACT Tumors and tumor-bearing hosts exhibit markedly altered circadian rhythms, which serve as markers in the early diagnosis and prognosis of cancer. Our study presents the effect of melatonin on circadian rhythms of lipid peroxides and antioxidants in N-nitrosodiethylamine (NDEA)-induced hepatocarcinogenesis. The circadian rhythm characteristics (acrophase, amplitude, and mesor) of thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and reduced glutathione (GSH) were markedly altered in NDEA-treated rats. Melatonin administration caused a significant increase in the amplitude and mesor values of antioxidants and a significant decrease in the mesor values of TBARS. Further delays in acrophase in NDEA-treated rats were reversed by melatonin administration. In conclusion, melatonin may exert its chemopreventive effect by its role as an antioxidant as well as by altering the circadian rhythm characteristics.
The Journal of Thoracic and Cardiovascular Surgery, 2005
This study was a prospective evaluation of surgical indications and outcomes for unilateral and b... more This study was a prospective evaluation of surgical indications and outcomes for unilateral and bilateral bronchiectasis according to hemodynamic (functional and morphologic) classification. Between January 1998 and January 2004, the morphologic features (cystic versus cylindric) by chest computed tomography and the hemodynamic features (perfused versus nonperfused) by lung ventilation/perfusion scan were determined in 66 patients with bronchiectasis (53 unilateral and 13 bilateral). The indication for surgical resection in both groups was the presence of localized areas of cystic, nonperfused bronchiectasis. In the unilateral bronchiectasis group, there were 28 female and 25 male patients with an average age of 37.5 +/- 3.8 years (range 6-40 years). Pneumonectomy was performed in 10 cases (8 left and 2 right), and lobectomy or bilobectomy was performed in 43. In the bilateral group, there were 7 male and 6 female patients with an average age of 42 +/- 5.4 years (range 9-55 years). Pneumonectomy was performed in 2 cases, lobectomy in 5, and bilateral staged lobectomy in 6. There was 1 postoperative death (1.5%), and morbidity was 18% (12 patients). Four patients required reexploration for bleeding, 4 had prolonged air leak develop, 3 acquired pulmonary infections, and 1 had localized empyema develop. During a mean follow-up of 52 months (range 24-82 months), 48 patients were considered cured (73%) and 17 had symptomatic improvement (26%). Pseudomonas infection and underlying chronic obstructive airway disease were poor prognostic factors (P < .05). The hemodynamic (functional and morphologic) classification provides an accurate functional classification for bronchiectasis. Its application in determining the indications and extent of surgical resection is superior to morphologic classification alone. Curative resection can be achieved in both unilateral and bilateral bronchiectasis with acceptable morbidity.
Recently, reliability analysis has been advocated as an effective approach to account for uncerta... more Recently, reliability analysis has been advocated as an effective approach to account for uncertainty in the geometric design process and to evaluate the risk associated with a particular design. In this approach, a risk measure (e.g. probability of noncompliance) is calculated to represent the probability that a specific design would not meet standard requirements. The majority of previous applications of reliability analysis in geometric design focused on evaluating the probability of noncompliance for only one mode of noncompliance such as insufficient sight distance. However, in many design situations, more than one mode of noncompliance may be present (e.g. insufficient sight distance and vehicle skidding at horizontal curves). In these situations, utilizing a multi-mode reliability approach that considers more than one failure (noncompliance) mode is required. The main objective of this paper is to demonstrate the application of multi-mode (system) reliability analysis to the design of horizontal curves. The process is demonstrated by a case study of Sea-to-Sky Highway located between Vancouver and Whistler, in southern British Columbia, Canada. Two noncompliance modes were considered: insufficient sight distance and vehicle skidding. The results show the importance of accounting for several noncompliance modes in the reliability model. The system reliability concept could be used in future studies to calibrate the design of various design elements in order to achieve consistent safety levels based on all possible modes of noncompliance.
Several studies have investigated the relationship between field-measured conflicts and the confl... more Several studies have investigated the relationship between field-measured conflicts and the conflicts obtained from micro-simulation models using the Surrogate Safety Assessment Model (SSAM). Results from recent studies have shown that while reasonable correlation between simulated and real traffic conflicts can be obtained especially after proper calibration, more work is still needed to confirm that simulated conflicts provide safety measures beyond what can be expected from exposure. As well, the results have emphasized that using micro-simulation model to evaluate safety without proper model calibration should be avoided. The calibration process adjusts relevant simulation parameters to maximize the correlation between field-measured and simulated conflicts. The main objective of this study is to investigate the transferability of calibrated parameters of the traffic simulation model (VISSIM) for safety analysis between different sites. The main purpose is to examine whether the calibrated parameters, when applied to other sites, give reasonable results in terms of the correlation between the field-measured and the simulated conflicts. Eighty-three hours of video data from two signalized intersections in Surrey, BC were used in this study. Automated video-based computer vision techniques were used to extract vehicle trajectories and identify field-measured rear-end conflicts. Calibrated VISSIM parameters obtained from the first intersection which maximized the correlation between simulated and field-observed conflicts were used to estimate traffic conflicts at the second intersection and to compare the results to parameters optimized specifically for the second intersection. The results show that the VISSIM parameters are generally transferable between the two locations as the transferred parameters provided better correlation between simulated and field-measured conflicts than using the default VISSIM parameters. Of the six VISSIM parameters identified as important for the safety analysis, two parameters were directly transferable, three parameters were transferable to some degree, and one parameter was not transferable.
Middle East Journal of Anaesthesiology, Jun 1, 2005
Thymectomy is an established therapy in the management of generalized myasthenia gravis (MG). How... more Thymectomy is an established therapy in the management of generalized myasthenia gravis (MG). However, the optimal surgical approach to thymectomy has remained controversial. There are advocates for transternal, transcervical approaches for "maximal" thymectomy. Video-assisted thoracoscopic thymectomy (VATT) presents new approach to thymectomy. By minimizing chest wall trauma, VATT not only causes less postoperative pain, shortens hospital stay, gives better cosmetic results but also leads to wider acceptance by patients for earlier surgery. Anesthesia for thymectomy in MG is challenging. Currently we are using non-muscle relaxant technique (NMRT) which we adopted in 1994, for maximal thymectomy. In this paper, we present our limited experience with two cases of VATT using two different NMRTs. Two cases of MG underwent VATT under general anesthesia (GA) and one lung ventilation (OLV) using double lumen tube (DLT). In both cases NMRT was used which encompass, light GA plus thoracic epidural analgesia (TEA) in one case and without TEA in the other case. We believe that the use of NMRT provides good operative and postoperative conditions. In this report we have described two different NMRTs, one with TEA and the other without. Further studies are needed on large number of cases to establish an anesthetic protocol for VATT.
We report two cases of unusual presentation of rib exostosis. The first patient presented acutely... more We report two cases of unusual presentation of rib exostosis. The first patient presented acutely with hemorrhagic shock due to massive hemothorax, and the second patient presented with repetitive chest infection complicated by empyema. In both patients, preoperative computed tomographic (CT) scan of the chest revealed rib exostoses, necessitating thoracotomy and rib resection.
Melatonin, the principle hormone of pineal gland plays an important role in several biological pr... more Melatonin, the principle hormone of pineal gland plays an important role in several biological processes. The effects of melatonin on hepatic marker enzymes [aspartate and alanine transaminases (AST and ALT)], lipid peroxides [thiobarbituric acid reactive substances (TBARS)] and antioxidants [reduced glutathione (GSH), glutathione peroxidase (GPx) and glutathione-S-transferase (GST)] during N-nitrosodiethylamine (NDEA)-induced hepatocarcinogenesis in rats were studied. Male albino Wistar rats of body weight 150-170 g were divided into four groups of six animals each. Group I animals served as control, Group II animals received single intraperitoneal injection of NDEA at a dose of 200 mg/kg body weight followed by weekly subcutaneous injections of CCl4 at a dose of 3 mL/kg body weight. Group III animals were treated as in Group II and melatonin (5 mg/kg body weight) was administered intraperitoneally. Group IV animals received melatonin alone at the same dose as Group III animals. A ...
Thymectomy is an established therapy in the management of generalized myasthenia gravis (MG). How... more Thymectomy is an established therapy in the management of generalized myasthenia gravis (MG). However, the optimal surgical approach to thymectomy has remained controversial. There are advocates for transternal, transcervical approaches for "maximal" thymectomy. Video-assisted thoracoscopic thymectomy (VATT) presents new approach to thymectomy. By minimizing chest wall trauma, VATT not only causes less postoperative pain, shortens hospital stay, gives better cosmetic results but also leads to wider acceptance by patients for earlier surgery. Anesthesia for thymectomy in MG is challenging. Currently we are using non-muscle relaxant technique (NMRT) which we adopted in 1994, for maximal thymectomy. In this paper, we present our limited experience with two cases of VATT using two different NMRTs. Two cases of MG underwent VATT under general anesthesia (GA) and one lung ventilation (OLV) using double lumen tube (DLT). In both cases NMRT was used which encompass, light GA plus ...
The present investigation was designed to study the protective role of Pongamia pinnata (an indig... more The present investigation was designed to study the protective role of Pongamia pinnata (an indigenous plant used in Ayurvedic medicine in India) leaf extract on oxidative stress during ammonium chloride-induced hyperammonemia by measuring the extent of oxidative damage as well as antioxidant status. Ethanolic extract of Pongamia pinnata (PPEt) leaves was administered orally (300 mg/kg body weight) and the effects of PPEt on the levels of thiobarbituric acid reactive substances (TBARS), hydroperoxides (HP), conjugated diene (CD), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and reduced glutathione (GSH) were studied in liver and kidney of ammonium chloride-induced hyperammonemic rats. On treatment with PPEt, a significant reduction in the levels of TBARS, HP, and CD and a significant increase in the levels of SOD, CAT, GPx, and GSH in liver and kidney of ammonium chloride-induced hyperammonemic rats were observed, which clearly shows the antioxidant property of PPEt. The study of induction of the antioxidant status is considered to be a reliable marker for evaluating the antiperoxidative effect of the medicinal plant. Our present findings show the protective role of PPEt against lipid peroxidation and suggest that PPEt possesses antioxidant potential that may be used for therapeutic purposes. The exact mechanism has to be still investigated and the isolation of active constituents is required.
ABSTRACT Tumors and tumor-bearing hosts exhibit markedly altered circadian rhythms, which serve a... more ABSTRACT Tumors and tumor-bearing hosts exhibit markedly altered circadian rhythms, which serve as markers in the early diagnosis and prognosis of cancer. Our study presents the effect of melatonin on circadian rhythms of lipid peroxides and antioxidants in N-nitrosodiethylamine (NDEA)-induced hepatocarcinogenesis. The circadian rhythm characteristics (acrophase, amplitude, and mesor) of thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and reduced glutathione (GSH) were markedly altered in NDEA-treated rats. Melatonin administration caused a significant increase in the amplitude and mesor values of antioxidants and a significant decrease in the mesor values of TBARS. Further delays in acrophase in NDEA-treated rats were reversed by melatonin administration. In conclusion, melatonin may exert its chemopreventive effect by its role as an antioxidant as well as by altering the circadian rhythm characteristics.
The Journal of Thoracic and Cardiovascular Surgery, 2005
This study was a prospective evaluation of surgical indications and outcomes for unilateral and b... more This study was a prospective evaluation of surgical indications and outcomes for unilateral and bilateral bronchiectasis according to hemodynamic (functional and morphologic) classification. Between January 1998 and January 2004, the morphologic features (cystic versus cylindric) by chest computed tomography and the hemodynamic features (perfused versus nonperfused) by lung ventilation/perfusion scan were determined in 66 patients with bronchiectasis (53 unilateral and 13 bilateral). The indication for surgical resection in both groups was the presence of localized areas of cystic, nonperfused bronchiectasis. In the unilateral bronchiectasis group, there were 28 female and 25 male patients with an average age of 37.5 +/- 3.8 years (range 6-40 years). Pneumonectomy was performed in 10 cases (8 left and 2 right), and lobectomy or bilobectomy was performed in 43. In the bilateral group, there were 7 male and 6 female patients with an average age of 42 +/- 5.4 years (range 9-55 years). Pneumonectomy was performed in 2 cases, lobectomy in 5, and bilateral staged lobectomy in 6. There was 1 postoperative death (1.5%), and morbidity was 18% (12 patients). Four patients required reexploration for bleeding, 4 had prolonged air leak develop, 3 acquired pulmonary infections, and 1 had localized empyema develop. During a mean follow-up of 52 months (range 24-82 months), 48 patients were considered cured (73%) and 17 had symptomatic improvement (26%). Pseudomonas infection and underlying chronic obstructive airway disease were poor prognostic factors (P < .05). The hemodynamic (functional and morphologic) classification provides an accurate functional classification for bronchiectasis. Its application in determining the indications and extent of surgical resection is superior to morphologic classification alone. Curative resection can be achieved in both unilateral and bilateral bronchiectasis with acceptable morbidity.
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Papers by Mohamed Essa