Mohamed Bachir Moussa - Academia.edu (original) (raw)
Papers by Mohamed Bachir Moussa
Recent Advances in Geo-Environmental Engineering, Geomechanics and Geotechnics, and Geohazards, 2018
The application of sewage sludge compost in agricultural soils has a dual interest. This allows p... more The application of sewage sludge compost in agricultural soils has a dual interest. This allows preserving nature and improving the soil quality by supplying plant nutrients. A field experiment was carried out to evaluate the effect of different amounts of sewage sludge compost (0, 20, 40 and 60 t ha −1) on chemical soil properties. The considered soil depths are (0-20; 20-40 and 40-60 cm). OM, N, P, K, pH, CE determination followed amendment with sewage sludge compost. The results indicated that the evaluated chemical soil parameters were changed by the application of this biosolid. In addition, sludge application increased the organic status of the soil and nutrients.
Agriculture, 2021
Farmyard manure, an amendment traditionally used for improving the fertility of sandy soils in ar... more Farmyard manure, an amendment traditionally used for improving the fertility of sandy soils in arid climates, is becoming scarce and expensive. Its shortage makes it necessary to evaluate, at field scale, the suitability and medium-term performance of other cheap, highly available substitutes. A field trial was established to analyze the effects of a single application of three organic residues on barley yield and nutrient uptake and selected soil properties after two consecutive harvests. Municipal solid waste compost (MSWC), sewage sludge compost (SSC) and farmyard manure (FYM) were tested at rates of 0, 20, 40 and 60 t ha−1. Adding all three organic amendments increased organic matter, cation exchange capacity and available P, Ca, Mg and K in the soil, the grain yield (up to 51%), and the barley plants’ nutrient contents. After the second harvest, a positive residual effect of the amendment was observed in plant yield (up to 77%) and nutrient contents. MSWC and SSC induced slight...
Numerical and analytical introduction to the prediction of grain boundary micro-crack initiation ... more Numerical and analytical introduction to the prediction of grain boundary micro-crack initiation induced by slips bands impingement. Effect of material and microstructure parameters. Abstract Micro-cracks are often observed at the intersections of thin slip bands (SB) and grain boundaries (GB) due to local stress concentration. Numerous models are based on the pile-up theory and the Griffith criterion, used since the pioneering work of Stroh. We have shown that the former underestimate strongly the macroscopic stress for GB micro crack nucleation. In fact, the key issue is that slip bands display finite thickness, ob-served to belong to [20nm 1000nm]. Therefore, one aims to account for the effect of SB thickness in crystal-line finite element (FE) calculations performed using the Cast3M software. The simulations take into account the effects of isotropic elasticity parameters, cubic elasticity, GB orientation and crystallographic orientation of the considered grain. Following the th...
Proceedings of the 2004 Winter Simulation Conference, 2004.
Procedia Materials Science, 2014
Strain localization is often observed in single and poly-crystals, for instance forming clear ban... more Strain localization is often observed in single and poly-crystals, for instance forming clear bands or persistent slip bands respectively during post-irradiation tensile loading or cyclic loading. This concerns FCC, BCC or HCP crystallographic structures. At the intersection of the so-called slip bands (SBs) and grain boundaries (GBs), stress concentration areas emerge contributing to intergranular microcrack initiation. Indeed, GB stress fields show singularities due to the SB plastic shearing of the surrounding elastic matrix. Since Stroh's work [[? ]], GB normal stress fields have been computed using pileup theory assumptions. However, as these approaches assume that slip occurs along only one single atomic plane, they overestimate GB normal stress fields because SBs generally display finite thickness, from a few ten nm to a few μm. Crystalline finite elements (FE) computations are carried out using the Cast3M software. Meshed microstructure includes an elastoplastic SB within a main elastic grain which which is embedded at free surface of an elastic matrix. Results show in fact that using the pileup formalism leads to large GB stress field overestimations. Therefore, an analytical formula describing the normal GB stress fields is proposed in the current paper, extending the pileup solution in the neighbourhood of the SB corner. The relationships between SB length and thickness and stress singularities are established in the light of the theory of matching asymptotic expansions. A double fracture criterion allows the prediction of intergranular microcrack initiation based on the computed stress singularities. Another analytical model based on the solution of the thermoelastic problem allow to propose a more general formula of the grain boundary stress fields accounting for the unloading effects. Using only one stress field computed by FE, the prefactors are computed and both analytical formulae are shown to be validated for all the range of grain size, SB thickness and remote applied stress.
American journal of orthopedics (Belle Mead, N.J.), 2013
We report the case of a patient who sustained a missed locked posterior shoulder dislocation with... more We report the case of a patient who sustained a missed locked posterior shoulder dislocation with a sizable anterior impression fracture and a concomitant acute rupture of the subscapularis tendon. Despite compromise of the tendon, a transfer of the lesser tuberosity into the humeral head defect along with suture anchor repair of the subscapularis was performed. Within 6 months, the patient regained near complete function of his shoulder with no episodes of instability. To our knowledge, this is the first reported case of an acute subscapularis rupture associated with a posterior shoulder dislocation and anterior humeral impression fracture, treated with the modified McLaughlin procedure and tendon repair with an excellent clinical result.
Journal of Construction Engineering, 2014
Large construction projects are complex, dynamic, and unpredictable. They are subject to external... more Large construction projects are complex, dynamic, and unpredictable. They are subject to external and uncontrollable events that affect their schedule and financial outcomes. Project managers take decisions along the lifecycle of the projects to align with projects objectives. These decisions are data dependent where data change over time. Simulation-based modeling and experimentation of such dynamic environment are a challenge. Modeling of large projects or multiprojects is difficult and impractical for standalone computers. This paper presents the criteria required in a simulation environment suitable for modeling large and complex systems such as construction projects to support their lifecycle management. Also presented is a platform that encompasses the identified criteria. The objective of the platform is to facilitate and simplify the simulation and modeling process and enable the inclusion of complexity in simulation models.
The Journal of Arthroplasty, 2015
The aims of this study were to assess damage on the surface of retrieved oxidized zirconium metal... more The aims of this study were to assess damage on the surface of retrieved oxidized zirconium metal (OxZr) femoral heads, to measure surface roughness of scratches, and to evaluate the extent of surface effacement using scanning electron microscopy (SEM). Ceramic zirconia-toughened alumina (ZTA) heads were analyzed for comparison. OxZr femoral heads explanted for recurrent dislocation had the most severe damage (p<0.001). The median surface roughness of damaged OxZr femoral heads was 1.49μm, compared to 0.084μm for damaged ZTA heads and 0.052μm for undamaged OxZr (p<0.001). This may be of clinical concern because increased surface roughness has the potential to increase the wear of polyethylene liners articulating against these OxZr heads in THA.
SPE Drilling Engineering, 1988
Summary This paper reports a successful application of multiple regression analysis, supported by... more Summary This paper reports a successful application of multiple regression analysis, supported by a detailed statistical study to verify the Bourgoyne and Young model. The model estimates the optimum penetration rate (ROP), weight on bit (WOB), and rotary speed under the effect of controllable and uncontrollable factors. Field data from three wells in the Arabian Gulf were used and emphasized the validity of this model. The model coefficients are sensitive to the number of points included. The correlation coefficients and multicollinearity sensitivity of each drilling parameter on the ROP are studied.
2010 3rd International Conference on Computer Science and Information Technology, 2010
AbstractThe massively growing demand for bandwidth-consuming real-time applications such as voic... more AbstractThe massively growing demand for bandwidth-consuming real-time applications such as voice and video, added to the need of QoS being guaranteed are the main motivation of this work. In this paper we propose a new medium access mechanism that ...
Water Research, 2005
A mathematical model describing the interaction between nitrifiers, heterotrophs and predators in... more A mathematical model describing the interaction between nitrifiers, heterotrophs and predators in wastewater treatment has been developed. The inclusion of a predation mechanism is a new addition to the existing activated sludge models. The developed model considered multi-substrate consumption and multi-species growth, maintenance and decay in a culture where nitrifiers, heterotrophs and predators (protozoa and metazoa) are coexisting. Two laboratoryscale sequenced batch reactors (SBRs) operated at different sludge retention time (SRT) of 30 and 100 days for a period of 4 years were used to calibrate and validate the model. Moreover, to assess the predator activity, a simple procedure was developed, based on measuring the respiration rate with and without the presence of the predators. The model successfully described the performance of two SBRs systems. The fraction of active biomass (ammonia oxidisers, nitrite oxidisers and heterotrophs) predicted by the proposed model was only 33% and 14% at SRT of 30 and 100 days, respectively. The high fraction of inert biomass predicted by the model was in accordance with the microscopic investigations of biomass viability in both reactors. The presented model was used to investigate the effect of increasing sludge age and the role of predators on the biomass composition of the tested SBR system.
Radiation Measurements, 2003
High concentrations of radon are often used as a geophysical tool for uranium exploration, earthq... more High concentrations of radon are often used as a geophysical tool for uranium exploration, earthquake and volcanic activity predication, and fault zones conÿrmation. The aim of this study was to assure the suitability of this method in the study of fault zones. For this purpose, a portable AlphaGUARD PQ 2000 device was used to detect the fracture zones along Qena-Safaga road, Eastern Desert, Egypt. Radon soil gas anomalies were found to be linearly distributed along NW-SE and NE-SW trends. Such directions agree well with the directions of the active fault deduced from earlier studies. Radon concentration in soil along the repeated three proÿles was anomalously high in all fault zones by a factor of 3-6 above background values. In the proÿles studied, the peaks recorded on the fault trace were found to be higher than the background. The analysis of the water samples collected from a well in the studied area showed that the HCO3 contents exceeded 1000 ppm, providing an additional evidence that the area under study is likely to be included within a major seismic belt. This study conÿrms strongly that radon gas and hydrochemical studies are a good tool for fault zones detection in similar areas.
Journal of Gastroenterology and Hepatology, 2013
Background and AimPatients infected with hepatitis C virus (HCV) often develop chronic liver dise... more Background and AimPatients infected with hepatitis C virus (HCV) often develop chronic liver disease, liver cirrhosis and concurrent thrombocytopenia, which manifests as decreased platelet counts and bleeding complications. Romiplostim, a thrombopoietin mimetic peptibody that stimulates the thrombopoietin receptor, has been used as a treatment for primary immune thrombocytopenia. We monitored the efficacy of preoperative romiplostim over 90 days in 35 male patients with chronic hepatitis C, liver cirrhosis and thrombocytopenia secondary to HCV infection.MethodsRomiplostim was administered at 2 μg/kg Q1W for a maximum of one month with a target platelet count of 70 × 109/L as a prerequisite for planned surgeries. Bone marrow aspirate was collected at baseline and at the end of the study, along with liver and kidney function assessments. A complete blood count was performed every third day throughout the study period.ResultsA rapid response to romiplostim therapy was observed, with 33...
Journal of Construction Engineering and Management, 2007
ABSTRACT
Journal of Construction Engineering and Management, 2006
... Mohamed Moussa, Janaka Ruwanpura, M.ASCE, George Jergeas. ... The decision maker considers th... more ... Mohamed Moussa, Janaka Ruwanpura, M.ASCE, George Jergeas. ... The decision maker considers the range of possible outcomes of a single alternative and uses the estimated values of this alternative in modeling the problem at hand, which produces a risk/benefit profile that ...
European Neuropsychopharmacology, 2010
European Neuropsychopharmacology, 2009
No abstract is available. To read the body of this article, please view the PDF online. ... © 200... more No abstract is available. To read the body of this article, please view the PDF online. ... © 2009 Elsevier BV and ECNP. Published by Elsevier Inc. All rights reserved. ... Visit SciVerse ScienceDirect to see if you have access via your institution. ... Advertisements on this site do not ...
Controlled Clinical Trials, 1989
It is shown how the predictive power, which takes account of prior clinical opinion about treatme... more It is shown how the predictive power, which takes account of prior clinical opinion about treatment differences, can be extended to group sequential designs based on a range rather than point of equivalence. It is found that such design when averaged over the whole prior distribution seems to be most conservative in terms of probability of firm conclusion followed by the nonzero null hypothesis design. Planning a trial based on calculations of the "exact" power or zero null hypothesis design may result in a practically unacceptable probability of firm conclusion.
Computers in Biology and Medicine, 1993
The paper considers the estimation of the potency of an unknown test preparation in relation to a... more The paper considers the estimation of the potency of an unknown test preparation in relation to a standard in a dilution assay. The method utilizes the Mantel-Haenszel one degree of freedom chi-square approach to test consistency of the observed potency ratio with a range of alternative potency ratios. The method is nonparametric as it does not require any distributional assumptions. However, it requires the doses employed to be equally spaced logarithmically. The dose-response curve is also required to be monotone over the dose range used.
Computers in Biology and Medicine, 1993
The paper deals with potency ratio estimation of parallel curve analytic dilution assays in case ... more The paper deals with potency ratio estimation of parallel curve analytic dilution assays in case log dose-response relationship could be reasonably described by a parabola. It comprises: (1) testing the adequacy and validity of the quadratic model by the analysis of variance; and (2) estimation of the relative potency of an unknown in relation to a standard preparation, its standard deviation and fiducial limits for its true value. The method is applicable whenever successive doses of an unknown are a constant multiple of a standard in randomized blocks or completely randomized design. The method can be generalized to polynomial models of higher order.
Recent Advances in Geo-Environmental Engineering, Geomechanics and Geotechnics, and Geohazards, 2018
The application of sewage sludge compost in agricultural soils has a dual interest. This allows p... more The application of sewage sludge compost in agricultural soils has a dual interest. This allows preserving nature and improving the soil quality by supplying plant nutrients. A field experiment was carried out to evaluate the effect of different amounts of sewage sludge compost (0, 20, 40 and 60 t ha −1) on chemical soil properties. The considered soil depths are (0-20; 20-40 and 40-60 cm). OM, N, P, K, pH, CE determination followed amendment with sewage sludge compost. The results indicated that the evaluated chemical soil parameters were changed by the application of this biosolid. In addition, sludge application increased the organic status of the soil and nutrients.
Agriculture, 2021
Farmyard manure, an amendment traditionally used for improving the fertility of sandy soils in ar... more Farmyard manure, an amendment traditionally used for improving the fertility of sandy soils in arid climates, is becoming scarce and expensive. Its shortage makes it necessary to evaluate, at field scale, the suitability and medium-term performance of other cheap, highly available substitutes. A field trial was established to analyze the effects of a single application of three organic residues on barley yield and nutrient uptake and selected soil properties after two consecutive harvests. Municipal solid waste compost (MSWC), sewage sludge compost (SSC) and farmyard manure (FYM) were tested at rates of 0, 20, 40 and 60 t ha−1. Adding all three organic amendments increased organic matter, cation exchange capacity and available P, Ca, Mg and K in the soil, the grain yield (up to 51%), and the barley plants’ nutrient contents. After the second harvest, a positive residual effect of the amendment was observed in plant yield (up to 77%) and nutrient contents. MSWC and SSC induced slight...
Numerical and analytical introduction to the prediction of grain boundary micro-crack initiation ... more Numerical and analytical introduction to the prediction of grain boundary micro-crack initiation induced by slips bands impingement. Effect of material and microstructure parameters. Abstract Micro-cracks are often observed at the intersections of thin slip bands (SB) and grain boundaries (GB) due to local stress concentration. Numerous models are based on the pile-up theory and the Griffith criterion, used since the pioneering work of Stroh. We have shown that the former underestimate strongly the macroscopic stress for GB micro crack nucleation. In fact, the key issue is that slip bands display finite thickness, ob-served to belong to [20nm 1000nm]. Therefore, one aims to account for the effect of SB thickness in crystal-line finite element (FE) calculations performed using the Cast3M software. The simulations take into account the effects of isotropic elasticity parameters, cubic elasticity, GB orientation and crystallographic orientation of the considered grain. Following the th...
Proceedings of the 2004 Winter Simulation Conference, 2004.
Procedia Materials Science, 2014
Strain localization is often observed in single and poly-crystals, for instance forming clear ban... more Strain localization is often observed in single and poly-crystals, for instance forming clear bands or persistent slip bands respectively during post-irradiation tensile loading or cyclic loading. This concerns FCC, BCC or HCP crystallographic structures. At the intersection of the so-called slip bands (SBs) and grain boundaries (GBs), stress concentration areas emerge contributing to intergranular microcrack initiation. Indeed, GB stress fields show singularities due to the SB plastic shearing of the surrounding elastic matrix. Since Stroh's work [[? ]], GB normal stress fields have been computed using pileup theory assumptions. However, as these approaches assume that slip occurs along only one single atomic plane, they overestimate GB normal stress fields because SBs generally display finite thickness, from a few ten nm to a few μm. Crystalline finite elements (FE) computations are carried out using the Cast3M software. Meshed microstructure includes an elastoplastic SB within a main elastic grain which which is embedded at free surface of an elastic matrix. Results show in fact that using the pileup formalism leads to large GB stress field overestimations. Therefore, an analytical formula describing the normal GB stress fields is proposed in the current paper, extending the pileup solution in the neighbourhood of the SB corner. The relationships between SB length and thickness and stress singularities are established in the light of the theory of matching asymptotic expansions. A double fracture criterion allows the prediction of intergranular microcrack initiation based on the computed stress singularities. Another analytical model based on the solution of the thermoelastic problem allow to propose a more general formula of the grain boundary stress fields accounting for the unloading effects. Using only one stress field computed by FE, the prefactors are computed and both analytical formulae are shown to be validated for all the range of grain size, SB thickness and remote applied stress.
American journal of orthopedics (Belle Mead, N.J.), 2013
We report the case of a patient who sustained a missed locked posterior shoulder dislocation with... more We report the case of a patient who sustained a missed locked posterior shoulder dislocation with a sizable anterior impression fracture and a concomitant acute rupture of the subscapularis tendon. Despite compromise of the tendon, a transfer of the lesser tuberosity into the humeral head defect along with suture anchor repair of the subscapularis was performed. Within 6 months, the patient regained near complete function of his shoulder with no episodes of instability. To our knowledge, this is the first reported case of an acute subscapularis rupture associated with a posterior shoulder dislocation and anterior humeral impression fracture, treated with the modified McLaughlin procedure and tendon repair with an excellent clinical result.
Journal of Construction Engineering, 2014
Large construction projects are complex, dynamic, and unpredictable. They are subject to external... more Large construction projects are complex, dynamic, and unpredictable. They are subject to external and uncontrollable events that affect their schedule and financial outcomes. Project managers take decisions along the lifecycle of the projects to align with projects objectives. These decisions are data dependent where data change over time. Simulation-based modeling and experimentation of such dynamic environment are a challenge. Modeling of large projects or multiprojects is difficult and impractical for standalone computers. This paper presents the criteria required in a simulation environment suitable for modeling large and complex systems such as construction projects to support their lifecycle management. Also presented is a platform that encompasses the identified criteria. The objective of the platform is to facilitate and simplify the simulation and modeling process and enable the inclusion of complexity in simulation models.
The Journal of Arthroplasty, 2015
The aims of this study were to assess damage on the surface of retrieved oxidized zirconium metal... more The aims of this study were to assess damage on the surface of retrieved oxidized zirconium metal (OxZr) femoral heads, to measure surface roughness of scratches, and to evaluate the extent of surface effacement using scanning electron microscopy (SEM). Ceramic zirconia-toughened alumina (ZTA) heads were analyzed for comparison. OxZr femoral heads explanted for recurrent dislocation had the most severe damage (p<0.001). The median surface roughness of damaged OxZr femoral heads was 1.49μm, compared to 0.084μm for damaged ZTA heads and 0.052μm for undamaged OxZr (p<0.001). This may be of clinical concern because increased surface roughness has the potential to increase the wear of polyethylene liners articulating against these OxZr heads in THA.
SPE Drilling Engineering, 1988
Summary This paper reports a successful application of multiple regression analysis, supported by... more Summary This paper reports a successful application of multiple regression analysis, supported by a detailed statistical study to verify the Bourgoyne and Young model. The model estimates the optimum penetration rate (ROP), weight on bit (WOB), and rotary speed under the effect of controllable and uncontrollable factors. Field data from three wells in the Arabian Gulf were used and emphasized the validity of this model. The model coefficients are sensitive to the number of points included. The correlation coefficients and multicollinearity sensitivity of each drilling parameter on the ROP are studied.
2010 3rd International Conference on Computer Science and Information Technology, 2010
AbstractThe massively growing demand for bandwidth-consuming real-time applications such as voic... more AbstractThe massively growing demand for bandwidth-consuming real-time applications such as voice and video, added to the need of QoS being guaranteed are the main motivation of this work. In this paper we propose a new medium access mechanism that ...
Water Research, 2005
A mathematical model describing the interaction between nitrifiers, heterotrophs and predators in... more A mathematical model describing the interaction between nitrifiers, heterotrophs and predators in wastewater treatment has been developed. The inclusion of a predation mechanism is a new addition to the existing activated sludge models. The developed model considered multi-substrate consumption and multi-species growth, maintenance and decay in a culture where nitrifiers, heterotrophs and predators (protozoa and metazoa) are coexisting. Two laboratoryscale sequenced batch reactors (SBRs) operated at different sludge retention time (SRT) of 30 and 100 days for a period of 4 years were used to calibrate and validate the model. Moreover, to assess the predator activity, a simple procedure was developed, based on measuring the respiration rate with and without the presence of the predators. The model successfully described the performance of two SBRs systems. The fraction of active biomass (ammonia oxidisers, nitrite oxidisers and heterotrophs) predicted by the proposed model was only 33% and 14% at SRT of 30 and 100 days, respectively. The high fraction of inert biomass predicted by the model was in accordance with the microscopic investigations of biomass viability in both reactors. The presented model was used to investigate the effect of increasing sludge age and the role of predators on the biomass composition of the tested SBR system.
Radiation Measurements, 2003
High concentrations of radon are often used as a geophysical tool for uranium exploration, earthq... more High concentrations of radon are often used as a geophysical tool for uranium exploration, earthquake and volcanic activity predication, and fault zones conÿrmation. The aim of this study was to assure the suitability of this method in the study of fault zones. For this purpose, a portable AlphaGUARD PQ 2000 device was used to detect the fracture zones along Qena-Safaga road, Eastern Desert, Egypt. Radon soil gas anomalies were found to be linearly distributed along NW-SE and NE-SW trends. Such directions agree well with the directions of the active fault deduced from earlier studies. Radon concentration in soil along the repeated three proÿles was anomalously high in all fault zones by a factor of 3-6 above background values. In the proÿles studied, the peaks recorded on the fault trace were found to be higher than the background. The analysis of the water samples collected from a well in the studied area showed that the HCO3 contents exceeded 1000 ppm, providing an additional evidence that the area under study is likely to be included within a major seismic belt. This study conÿrms strongly that radon gas and hydrochemical studies are a good tool for fault zones detection in similar areas.
Journal of Gastroenterology and Hepatology, 2013
Background and AimPatients infected with hepatitis C virus (HCV) often develop chronic liver dise... more Background and AimPatients infected with hepatitis C virus (HCV) often develop chronic liver disease, liver cirrhosis and concurrent thrombocytopenia, which manifests as decreased platelet counts and bleeding complications. Romiplostim, a thrombopoietin mimetic peptibody that stimulates the thrombopoietin receptor, has been used as a treatment for primary immune thrombocytopenia. We monitored the efficacy of preoperative romiplostim over 90 days in 35 male patients with chronic hepatitis C, liver cirrhosis and thrombocytopenia secondary to HCV infection.MethodsRomiplostim was administered at 2 μg/kg Q1W for a maximum of one month with a target platelet count of 70 × 109/L as a prerequisite for planned surgeries. Bone marrow aspirate was collected at baseline and at the end of the study, along with liver and kidney function assessments. A complete blood count was performed every third day throughout the study period.ResultsA rapid response to romiplostim therapy was observed, with 33...
Journal of Construction Engineering and Management, 2007
ABSTRACT
Journal of Construction Engineering and Management, 2006
... Mohamed Moussa, Janaka Ruwanpura, M.ASCE, George Jergeas. ... The decision maker considers th... more ... Mohamed Moussa, Janaka Ruwanpura, M.ASCE, George Jergeas. ... The decision maker considers the range of possible outcomes of a single alternative and uses the estimated values of this alternative in modeling the problem at hand, which produces a risk/benefit profile that ...
European Neuropsychopharmacology, 2010
European Neuropsychopharmacology, 2009
No abstract is available. To read the body of this article, please view the PDF online. ... © 200... more No abstract is available. To read the body of this article, please view the PDF online. ... © 2009 Elsevier BV and ECNP. Published by Elsevier Inc. All rights reserved. ... Visit SciVerse ScienceDirect to see if you have access via your institution. ... Advertisements on this site do not ...
Controlled Clinical Trials, 1989
It is shown how the predictive power, which takes account of prior clinical opinion about treatme... more It is shown how the predictive power, which takes account of prior clinical opinion about treatment differences, can be extended to group sequential designs based on a range rather than point of equivalence. It is found that such design when averaged over the whole prior distribution seems to be most conservative in terms of probability of firm conclusion followed by the nonzero null hypothesis design. Planning a trial based on calculations of the "exact" power or zero null hypothesis design may result in a practically unacceptable probability of firm conclusion.
Computers in Biology and Medicine, 1993
The paper considers the estimation of the potency of an unknown test preparation in relation to a... more The paper considers the estimation of the potency of an unknown test preparation in relation to a standard in a dilution assay. The method utilizes the Mantel-Haenszel one degree of freedom chi-square approach to test consistency of the observed potency ratio with a range of alternative potency ratios. The method is nonparametric as it does not require any distributional assumptions. However, it requires the doses employed to be equally spaced logarithmically. The dose-response curve is also required to be monotone over the dose range used.
Computers in Biology and Medicine, 1993
The paper deals with potency ratio estimation of parallel curve analytic dilution assays in case ... more The paper deals with potency ratio estimation of parallel curve analytic dilution assays in case log dose-response relationship could be reasonably described by a parabola. It comprises: (1) testing the adequacy and validity of the quadratic model by the analysis of variance; and (2) estimation of the relative potency of an unknown in relation to a standard preparation, its standard deviation and fiducial limits for its true value. The method is applicable whenever successive doses of an unknown are a constant multiple of a standard in randomized blocks or completely randomized design. The method can be generalized to polynomial models of higher order.