D.M. Motiur Rahaman - Academia.edu (original) (raw)

Papers by D.M. Motiur Rahaman

Powder compacts having a nominal composition of YBaâCuâO{sub 6+δ} were sintered in air between 9... more Powder compacts having a nominal composition of YBaâCuâO{sub 6+δ} were sintered in air between 910° to 940°C in a loading dilatometer that permitted the application of small, controlled uniaxial stresses to the sintering compact. The highest density (95% of theoretical) was obtained after sintering without load for â 2 h at 935°C. The application of constant, small uniaxial stresses produced extensive shear deformation and a small increase in the densification rate. The measured ratio of the densification rate to the creep rate provided strong support for the presence of a liquid phase during sintering. The data allowed the measurement of the ratio of the creep viscosity to the densification viscosity, which was â 0.8 over the density range 0.6 to 0.8, and the sintering stress, which was â 0.8 over the density range 0.6 to 0.8, and the sintering stress, which was â 400 kPa. These data show that extensive shear deformation and small but measurable increases in the densification rates may be achieved by the application of relatively small uniaxial stresses (â 1 MPa) during sintering of YBaâCuâO{sub 6+δ} powder compacts.

MRS Online Proceeding Library

ABSTRACT

Review of Scientific Instruments

A loading dilatometer has been constructed to study the sintering behavior of powder compacts sub... more A loading dilatometer has been constructed to study the sintering behavior of powder compacts subjected to low uniaxial stresses between 0 and 0.4 MPa and at temperatures up to 1250 K. A novel feature of the instrument is a device for the application of a controlled and measured stress to the sintering compact. Constant, as well as transient, stresses can be applied and the atmosphere inside the dilatometer can be controlled. Some representative results are reported.

Journal of the American Ceramic Society

ABSTRACT

Theriogenology, 2011

Cardiovascular disease is the leading cause of death in developed countries and is one of the lea... more Cardiovascular disease is the leading cause of death in developed countries and is one of the leading causes of disease burden in developing countries. Therapies have markedly increased survival in several categories of patients, nonetheless mortality still remains high. For this reason high hopes are associated with recent developments in stem cell biology and regenerative medicine that promise to replace damaged or lost cardiac muscle with healthy tissue, and thus to dramatically improve the quality of life and survival in patients with various cardiomyopathies. Much of our insight into the molecular and cellular basis of cardiovascular biology comes from small animal models, particularly mice. However, significant differences exist with regard to several cardiac characteristics when mice are compared with humans. For this reason, large animal models like dog, sheep and pig have a well established role in cardiac research. A distinct characteristic of cardiac stem cells is that they can either be endogenous or derive from outside the heart itself; they can originate as the natural course of their differentiation programme (e.g., embryonic stem cells) or can be the result of specific inductive conditions (e.g., mesenchymal stem cells). In this review we will summarize the current knowledge on the kind of heart-related stem cells currently available in large animal species and their relevance to human studies as pre-clinical models.

Journal of the American Ceramic Society, 1997

Page 1. Initial Coarsening and Microstructural Evolution of Fast-Fired and MgO-Doped Al2O3 Frank ... more Page 1. Initial Coarsening and Microstructural Evolution of Fast-Fired and MgO-Doped Al2O3 Frank JT Lin* and Lutgard C. De Jonghe* Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California ...

Journal of the American Ceramic Society, 1985

The early and intermediate stages of densification of alumina containing calcia were examined at ... more The early and intermediate stages of densification of alumina containing calcia were examined at subeutectic temperatures. Up to 0.15 wt% calcia causes a decrease in the densification rate; from 0.15 to 0.7 wt% calcia, the densification rate increases initially but then decreases at longer times; more than 0.75 wt% calcia leads to a monotonically decreasing densification rate. The data for materials containing more than 0.15 wt% calcia may be interpreted as a competition between enhanced subeutectic densification and the presence of densification-retarding second phases.

Journal of the American Ceramic Society, 2005

Page 1. Microstructure Refinement of Sintered Alumina by a Two-Step Sintering Technique Frank JT ... more Page 1. Microstructure Refinement of Sintered Alumina by a Two-Step Sintering Technique Frank JT Lin* and Lutgard C. De Jonghe* Materials Science Division, Lawrence Berkeley Laboratory, Berkeley, California 94720, and ...

Journal of the American Ceramic Society, 1987

... MgO Compacts MARK LIN, MOHAMMED N. RAHAMAN,“ and LUTGARD C. DE JONGHE* ... The exponent rn eq... more ... MgO Compacts MARK LIN, MOHAMMED N. RAHAMAN,“ and LUTGARD C. DE JONGHE* ... The exponent rn equals 3 for grain-boundary diffusion (Coble creep') and m equals 2 for lattice diffusion (Nabarro-Herring creep”.”). ...

Journal of Biomedical Materials Research Part A, 2010

Bioactive glass scaffolds with a microstructure similar to that of dry human trabecular bone but ... more Bioactive glass scaffolds with a microstructure similar to that of dry human trabecular bone but with three different compositions were evaluated for potential applications in bone repair. The preparation of the scaffolds and the effect of the glass composition on the degradation and conversion of the scaffolds to a hydroxyapatite (HA)-type material in a simulated body fluid (SBF) are reported here (Part I). The in vitro response of osteogenic cells to the scaffolds and the in vivo evaluation of the scaffolds in a rat subcutaneous implantation model are described in Part II. Scaffolds (porosity = 78-82%; pore size = 100-500 microm) were prepared using a polymer foam replication technique. The glasses consisted of a silicate (13-93) composition, a borosilicate composition (designated 13-93B1), and a borate composition (13-93B3), in which one-third or all of the SiO2 content of 13-93 was replaced by B2O3, respectively. The conversion rate of the scaffolds to HA in the SBF increased markedly with the B2O3 content of the glass. Concurrently, the pH of the SBF also increased with the B2O3 content of the scaffolds. The compressive strengths of the as-prepared scaffolds (5-11 MPa) were in the upper range of values reported for trabecular bone, but they decreased markedly with immersion time in the SBF and with increasing B2O3 content of the glass. The results show that scaffolds with a wide range of bioactivity and degradation rate can be achieved by replacing varying amounts of SiO(2) in silicate bioactive glass with B2O3.

Clinical Orthopaedics and Related Research®, 2011

Background Replacement of diseased areas of the joint with tissue-engineered osteochondral grafts... more Background Replacement of diseased areas of the joint with tissue-engineered osteochondral grafts has shown potential in the treatment of osteoarthritis. Bioactive glasses are candidates for the osseous analog of these grafts. Questions/purposes (1) Does Bioactive Glass 13-93 (BG 13-93) as a subchondral substrate improve collagen and glycosaminoglycan production in a tissue-engineered cartilage layer? (2) Does BG 13-93 as a culture medium supplement increase the collagen and glycosaminoglycan production and improve the mechanical properties in a tissue-engineered cartilage layer?

Acta Biomaterialia, 2012

Scaffolds of 13-93 bioactive glass (6Na 2 O, 12K 2 O, 5MgO, 20CaO, 4P 2 O 5 , 53SiO 2 ; wt.%) wit... more Scaffolds of 13-93 bioactive glass (6Na 2 O, 12K 2 O, 5MgO, 20CaO, 4P 2 O 5 , 53SiO 2 ; wt.%) with an oriented pore architecture were formed by unidirectional freezing of camphene-based suspensions, followed by thermal annealing of the frozen constructs to grow the camphene crystals. After sublimation of the camphene, the constructs were sintered (1 h at 700°C) to produce a dense glass phase with oriented macropores. The objective of this work was to study how constant freezing rates (1-7°C min À1 ) during the freezing step influenced the pore orientation and mechanical response of the scaffolds. When compared to scaffolds prepared by freezing the suspensions on a substrate kept at a constant temperature of 3°C (time-dependent freezing rate), higher freezing rates resulted in better pore orientation, a more homogeneous microstructure and a marked improvement in the mechanical response of the scaffolds in compression. Scaffolds fabricated using a constant freezing rate of 7°C min À1 (porosity = 50 ± 4%; average pore diameter = 100 lm), had a compressive strength of 47 ± 5 MPa and an elastic modulus of 11 ± 3 GPa (in the orientation direction). In comparison, scaffolds prepared by freezing on the constant-temperature substrate had strength and modulus values of 35 ± 11 MPa and 8 ± 3 GPa, respectively. These oriented bioactive glass scaffolds prepared by the constant freezing rate route could potentially be used for the repair of defects in load-bearing bones, such as segmental defects in the long bones.

Bulletin of the World Health Organisation

A clinical trial was carried out with 126 male patients over 2 years ofage suffering from diarrho... more A clinical trial was carried out with 126 male patients over 2 years ofage suffering from diarrhoea requiring intravenous rehydration, 80 of the patients sufferingfrom cholera and 46 from non-cholera diarrhoea. A new "diarrhoea treatment solution " (DTS) containing sodium at a concentration of 118 mmol/litre and glucose at 44 mmol/litre was compared with the usual Dacca intravenous solution (DS) which has a sodium concentration of 133 mmol/litre and contains no glucose. The other constituents and their concentrations were the same in both solutions. All the patients responded well clinically and made an uneventful recovery. Oral water intake measured during the first 24 h was higher in the group receiving the DS. This group also excreted a significantly higher quantity ofsodium in the urine. A significant fall in the level of blood glucose from the admission values occurred in both the groups; the fall was relatively less in the DTS group, this solution containing 44 mmol of glucose per litre. Further work is required to find the optimum concentration of glucose in the solution for infants and young children.

The Journal of tropical medicine and hygiene

Clinical nephrology

The hemolytic-uremic syndrome (HUS) following dysentery caused by S. dysenteriae Type 1, characte... more The hemolytic-uremic syndrome (HUS) following dysentery caused by S. dysenteriae Type 1, characterized by microangiopathic hemolytic anemia and acute renal insufficiency, is clinically similar but not identical to the idiopathic HUS. We studied renal necropsy specimens of nine children who died of HUS following shigellosis by light and immunofluorescent microscopy and compared them to 12 controls: six cases with severe shigellosis without HUS, and six with pneumonia or sepsis. Eight of nine HUS cases showed cortical necrosis, extensive glomerular thrombosis or arterial thrombosis. Cases without HUS showed only scattered glomerular fibrin thrombin and widening of the mesangium. Among seven HUS cases studied by immunofluorescent microscopy, three demonstrated deposition of glomerular IgM and complement (C3) and one of the three had IgG and IgA as well; four cases had neither immunoglobulin or complement deposits. Among nine controls, two demonstrated IgM and three IgG, but none had C3. Both HUS and non-HUS cases had fibrin deposition. In the three HUS cases studied by electron microscopy intracapillary material (fibrin and platelets) was seen in all three, and sparse electron-dense deposits in mesangial matrix in one. The data indicate that the renal histopathology in the HUS following shigellosis consistently presents as a severe thrombotic microangiopathy, but lacks the characteristic endothelial and mesangial lesions of idiopathic HUS. The infrequent demonstration of glomerular immunoglobulin deposition fails to support an immunoglobulin-mediated pathogenesis.

Journal of clinical & laboratory immunology

In order to study the relationship between the presence of circulating immune complexes (CIC) and... more In order to study the relationship between the presence of circulating immune complexes (CIC) and the severity and duration of acute dysentery, we studied 11 adults and 45 children in Bangladesh with bacillary and amebic dysentery, using the Raji cell and solid-phase C1q (C1q-SPA) assays. CIC were found in 70% of patients with shigellosis and in all eight cases of amebic dysentery. Mild shigellosis was associated with positive samples in the first week of clinical illness, whereas severe cases, including those with the hemolytic-uremic syndrome, had negative admission assays but positive convalescent assays. Samples positive in the first two weeks of illness were more likely positive by the Raji cell assay alone whereas samples in the third and fourth weeks of illness were positive more often by the C1q-SPA assay. Only one shigellosis sample was positive by both assays. In amebiasis 11 of 13 samples were positive by the Raji assay alone. In dysenteric disease circulating immune complexes probably represents the failure of the inflamed mucosa to exclude microbial and dietary antigens, and suggests that the presence of CIC in any intestinal disease must be interpreted with caution.

Powder compacts having a nominal composition of YBaâCuâO{sub 6+δ} were sintered in air between 9... more Powder compacts having a nominal composition of YBaâCuâO{sub 6+δ} were sintered in air between 910° to 940°C in a loading dilatometer that permitted the application of small, controlled uniaxial stresses to the sintering compact. The highest density (95% of theoretical) was obtained after sintering without load for â 2 h at 935°C. The application of constant, small uniaxial stresses produced extensive shear deformation and a small increase in the densification rate. The measured ratio of the densification rate to the creep rate provided strong support for the presence of a liquid phase during sintering. The data allowed the measurement of the ratio of the creep viscosity to the densification viscosity, which was â 0.8 over the density range 0.6 to 0.8, and the sintering stress, which was â 0.8 over the density range 0.6 to 0.8, and the sintering stress, which was â 400 kPa. These data show that extensive shear deformation and small but measurable increases in the densification rates may be achieved by the application of relatively small uniaxial stresses (â 1 MPa) during sintering of YBaâCuâO{sub 6+δ} powder compacts.

MRS Online Proceeding Library

ABSTRACT

Review of Scientific Instruments

A loading dilatometer has been constructed to study the sintering behavior of powder compacts sub... more A loading dilatometer has been constructed to study the sintering behavior of powder compacts subjected to low uniaxial stresses between 0 and 0.4 MPa and at temperatures up to 1250 K. A novel feature of the instrument is a device for the application of a controlled and measured stress to the sintering compact. Constant, as well as transient, stresses can be applied and the atmosphere inside the dilatometer can be controlled. Some representative results are reported.

Journal of the American Ceramic Society

ABSTRACT

Theriogenology, 2011

Cardiovascular disease is the leading cause of death in developed countries and is one of the lea... more Cardiovascular disease is the leading cause of death in developed countries and is one of the leading causes of disease burden in developing countries. Therapies have markedly increased survival in several categories of patients, nonetheless mortality still remains high. For this reason high hopes are associated with recent developments in stem cell biology and regenerative medicine that promise to replace damaged or lost cardiac muscle with healthy tissue, and thus to dramatically improve the quality of life and survival in patients with various cardiomyopathies. Much of our insight into the molecular and cellular basis of cardiovascular biology comes from small animal models, particularly mice. However, significant differences exist with regard to several cardiac characteristics when mice are compared with humans. For this reason, large animal models like dog, sheep and pig have a well established role in cardiac research. A distinct characteristic of cardiac stem cells is that they can either be endogenous or derive from outside the heart itself; they can originate as the natural course of their differentiation programme (e.g., embryonic stem cells) or can be the result of specific inductive conditions (e.g., mesenchymal stem cells). In this review we will summarize the current knowledge on the kind of heart-related stem cells currently available in large animal species and their relevance to human studies as pre-clinical models.

Journal of the American Ceramic Society, 1997

Page 1. Initial Coarsening and Microstructural Evolution of Fast-Fired and MgO-Doped Al2O3 Frank ... more Page 1. Initial Coarsening and Microstructural Evolution of Fast-Fired and MgO-Doped Al2O3 Frank JT Lin* and Lutgard C. De Jonghe* Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California ...

Journal of the American Ceramic Society, 1985

The early and intermediate stages of densification of alumina containing calcia were examined at ... more The early and intermediate stages of densification of alumina containing calcia were examined at subeutectic temperatures. Up to 0.15 wt% calcia causes a decrease in the densification rate; from 0.15 to 0.7 wt% calcia, the densification rate increases initially but then decreases at longer times; more than 0.75 wt% calcia leads to a monotonically decreasing densification rate. The data for materials containing more than 0.15 wt% calcia may be interpreted as a competition between enhanced subeutectic densification and the presence of densification-retarding second phases.

Journal of the American Ceramic Society, 2005

Page 1. Microstructure Refinement of Sintered Alumina by a Two-Step Sintering Technique Frank JT ... more Page 1. Microstructure Refinement of Sintered Alumina by a Two-Step Sintering Technique Frank JT Lin* and Lutgard C. De Jonghe* Materials Science Division, Lawrence Berkeley Laboratory, Berkeley, California 94720, and ...

Journal of the American Ceramic Society, 1987

... MgO Compacts MARK LIN, MOHAMMED N. RAHAMAN,“ and LUTGARD C. DE JONGHE* ... The exponent rn eq... more ... MgO Compacts MARK LIN, MOHAMMED N. RAHAMAN,“ and LUTGARD C. DE JONGHE* ... The exponent rn equals 3 for grain-boundary diffusion (Coble creep') and m equals 2 for lattice diffusion (Nabarro-Herring creep”.”). ...

Journal of Biomedical Materials Research Part A, 2010

Bioactive glass scaffolds with a microstructure similar to that of dry human trabecular bone but ... more Bioactive glass scaffolds with a microstructure similar to that of dry human trabecular bone but with three different compositions were evaluated for potential applications in bone repair. The preparation of the scaffolds and the effect of the glass composition on the degradation and conversion of the scaffolds to a hydroxyapatite (HA)-type material in a simulated body fluid (SBF) are reported here (Part I). The in vitro response of osteogenic cells to the scaffolds and the in vivo evaluation of the scaffolds in a rat subcutaneous implantation model are described in Part II. Scaffolds (porosity = 78-82%; pore size = 100-500 microm) were prepared using a polymer foam replication technique. The glasses consisted of a silicate (13-93) composition, a borosilicate composition (designated 13-93B1), and a borate composition (13-93B3), in which one-third or all of the SiO2 content of 13-93 was replaced by B2O3, respectively. The conversion rate of the scaffolds to HA in the SBF increased markedly with the B2O3 content of the glass. Concurrently, the pH of the SBF also increased with the B2O3 content of the scaffolds. The compressive strengths of the as-prepared scaffolds (5-11 MPa) were in the upper range of values reported for trabecular bone, but they decreased markedly with immersion time in the SBF and with increasing B2O3 content of the glass. The results show that scaffolds with a wide range of bioactivity and degradation rate can be achieved by replacing varying amounts of SiO(2) in silicate bioactive glass with B2O3.

Clinical Orthopaedics and Related Research®, 2011

Background Replacement of diseased areas of the joint with tissue-engineered osteochondral grafts... more Background Replacement of diseased areas of the joint with tissue-engineered osteochondral grafts has shown potential in the treatment of osteoarthritis. Bioactive glasses are candidates for the osseous analog of these grafts. Questions/purposes (1) Does Bioactive Glass 13-93 (BG 13-93) as a subchondral substrate improve collagen and glycosaminoglycan production in a tissue-engineered cartilage layer? (2) Does BG 13-93 as a culture medium supplement increase the collagen and glycosaminoglycan production and improve the mechanical properties in a tissue-engineered cartilage layer?

Acta Biomaterialia, 2012

Scaffolds of 13-93 bioactive glass (6Na 2 O, 12K 2 O, 5MgO, 20CaO, 4P 2 O 5 , 53SiO 2 ; wt.%) wit... more Scaffolds of 13-93 bioactive glass (6Na 2 O, 12K 2 O, 5MgO, 20CaO, 4P 2 O 5 , 53SiO 2 ; wt.%) with an oriented pore architecture were formed by unidirectional freezing of camphene-based suspensions, followed by thermal annealing of the frozen constructs to grow the camphene crystals. After sublimation of the camphene, the constructs were sintered (1 h at 700°C) to produce a dense glass phase with oriented macropores. The objective of this work was to study how constant freezing rates (1-7°C min À1 ) during the freezing step influenced the pore orientation and mechanical response of the scaffolds. When compared to scaffolds prepared by freezing the suspensions on a substrate kept at a constant temperature of 3°C (time-dependent freezing rate), higher freezing rates resulted in better pore orientation, a more homogeneous microstructure and a marked improvement in the mechanical response of the scaffolds in compression. Scaffolds fabricated using a constant freezing rate of 7°C min À1 (porosity = 50 ± 4%; average pore diameter = 100 lm), had a compressive strength of 47 ± 5 MPa and an elastic modulus of 11 ± 3 GPa (in the orientation direction). In comparison, scaffolds prepared by freezing on the constant-temperature substrate had strength and modulus values of 35 ± 11 MPa and 8 ± 3 GPa, respectively. These oriented bioactive glass scaffolds prepared by the constant freezing rate route could potentially be used for the repair of defects in load-bearing bones, such as segmental defects in the long bones.

Bulletin of the World Health Organisation

A clinical trial was carried out with 126 male patients over 2 years ofage suffering from diarrho... more A clinical trial was carried out with 126 male patients over 2 years ofage suffering from diarrhoea requiring intravenous rehydration, 80 of the patients sufferingfrom cholera and 46 from non-cholera diarrhoea. A new "diarrhoea treatment solution " (DTS) containing sodium at a concentration of 118 mmol/litre and glucose at 44 mmol/litre was compared with the usual Dacca intravenous solution (DS) which has a sodium concentration of 133 mmol/litre and contains no glucose. The other constituents and their concentrations were the same in both solutions. All the patients responded well clinically and made an uneventful recovery. Oral water intake measured during the first 24 h was higher in the group receiving the DS. This group also excreted a significantly higher quantity ofsodium in the urine. A significant fall in the level of blood glucose from the admission values occurred in both the groups; the fall was relatively less in the DTS group, this solution containing 44 mmol of glucose per litre. Further work is required to find the optimum concentration of glucose in the solution for infants and young children.

The Journal of tropical medicine and hygiene

Clinical nephrology

The hemolytic-uremic syndrome (HUS) following dysentery caused by S. dysenteriae Type 1, characte... more The hemolytic-uremic syndrome (HUS) following dysentery caused by S. dysenteriae Type 1, characterized by microangiopathic hemolytic anemia and acute renal insufficiency, is clinically similar but not identical to the idiopathic HUS. We studied renal necropsy specimens of nine children who died of HUS following shigellosis by light and immunofluorescent microscopy and compared them to 12 controls: six cases with severe shigellosis without HUS, and six with pneumonia or sepsis. Eight of nine HUS cases showed cortical necrosis, extensive glomerular thrombosis or arterial thrombosis. Cases without HUS showed only scattered glomerular fibrin thrombin and widening of the mesangium. Among seven HUS cases studied by immunofluorescent microscopy, three demonstrated deposition of glomerular IgM and complement (C3) and one of the three had IgG and IgA as well; four cases had neither immunoglobulin or complement deposits. Among nine controls, two demonstrated IgM and three IgG, but none had C3. Both HUS and non-HUS cases had fibrin deposition. In the three HUS cases studied by electron microscopy intracapillary material (fibrin and platelets) was seen in all three, and sparse electron-dense deposits in mesangial matrix in one. The data indicate that the renal histopathology in the HUS following shigellosis consistently presents as a severe thrombotic microangiopathy, but lacks the characteristic endothelial and mesangial lesions of idiopathic HUS. The infrequent demonstration of glomerular immunoglobulin deposition fails to support an immunoglobulin-mediated pathogenesis.

Journal of clinical & laboratory immunology

In order to study the relationship between the presence of circulating immune complexes (CIC) and... more In order to study the relationship between the presence of circulating immune complexes (CIC) and the severity and duration of acute dysentery, we studied 11 adults and 45 children in Bangladesh with bacillary and amebic dysentery, using the Raji cell and solid-phase C1q (C1q-SPA) assays. CIC were found in 70% of patients with shigellosis and in all eight cases of amebic dysentery. Mild shigellosis was associated with positive samples in the first week of clinical illness, whereas severe cases, including those with the hemolytic-uremic syndrome, had negative admission assays but positive convalescent assays. Samples positive in the first two weeks of illness were more likely positive by the Raji cell assay alone whereas samples in the third and fourth weeks of illness were positive more often by the C1q-SPA assay. Only one shigellosis sample was positive by both assays. In amebiasis 11 of 13 samples were positive by the Raji assay alone. In dysenteric disease circulating immune complexes probably represents the failure of the inflamed mucosa to exclude microbial and dietary antigens, and suggests that the presence of CIC in any intestinal disease must be interpreted with caution.