I-Ming Tang - Academia.edu (original) (raw)

Papers by I-Ming Tang

Journal of Low Temperature Physics, 1983

The effect of Anderson impurities on proximity effect tunneling into two-band metals such as pall... more The effect of Anderson impurities on proximity effect tunneling into two-band metals such as palladium is studied. The Yamada-Yosida approach is used to treat the Anderson impurities in the two-band metal. In the Kondo region, it is shown that the pair-breaking parameter for the d band mimics the pair-breaking parameter in the Miiller-Hartmann and Zittartz theory for low-Kondo-temperature alloys (Tc>>T~ but deviates from it for high-TK alloys. The change in the transition temperature of the proximity effect sandwich due to the presence of Anderson impurities in the two bands of the normal side appears to be similar to that obtained by Kaiser except for the presence of the new pair-breaking parameter.

Malaria is transmitted to the person by the biting of infectious Anopheles mosquitoes. This infec... more Malaria is transmitted to the person by the biting of infectious Anopheles mosquitoes. This infectious disease caused by the parasite genus Plasmodium. Four species of this parasite cause human malaria, namely, Plasmodium vivax, Plasmodium falciparum, Plasmodium ovale and Plasmodium malariae. The difference between P.vivax and P. falciparum is that a person suffering from P. vivax infection can suffer relapses of the disease. This is due the parasite being able to remain dormant in the liver of the cases where it is able to re-infect the case after a passage of time. During this stage, the case is classified as being in the dormant class. The model to describe the transmission between falciparum and vivax malaria consists of a human population divided into four classes, the susceptible, the infectious, the dormant and the recovered classes. The vector population is separated into two classes, the susceptible and infectious classes. We analyze our model by using standard dynamic mode...

Journal of Magnetism and Magnetic Materials, 2009

The magnetic properties of Co-ferrite-doped hydroxyapatite (HAP) nanoparticles of composition Ca ... more The magnetic properties of Co-ferrite-doped hydroxyapatite (HAP) nanoparticles of composition Ca 10À3x Fe 2x Co x (PO 4) 6 (OH) 2 (where x ¼ 0, 0.1, 0.2, 0.3, 0.4 and 0.5% mole) are studied. Transmission electron microscope micrograms show that the 90 nm size nanoparticles annealed at 1250 1C have a core/shell structure. Their electron diffraction patterns show that the shell is composed of the hydroxyapatite and the core is composed of the Co-ferrite, CoFe 2 O 4. Electron spin resonance measurements indicate that the Co 2+ ions are being substituted into the Ca(1) sites in HAP lattice. X-ray diffraction studies show the formation of impurity phases as higher amounts of the Fe 3+ /Co 2+ ions which are substituted into the HAP host matrix. The presence of two sextets (one for the A-site Fe 3+ and the other for the B-site Fe 3+) in the Mö ssbauer spectrum for all the doped samples clearly indicates that the CoFe 2 O 4 .cores are in the ferromagnetic state. Evidence of the impurity phases is seen in the appearance of doublet patterns in the Mö ssbauer spectrums for the heavier-doped (x ¼ 0.4 and 0.5) specimens. The decrease in the saturation magnetizations and other magnetic properties of the nanoparticles at the higher doping levels is consistent with some of the Fe 3+ and Co 2+ which being used to form the CoO and Fe 2 O 3 impurity phase seen in the XRD patterns.

Nature Nanotechnology, 2008

Recent toxicology studies suggest that nanosized aggregates of fullerene molecules can enter cell... more Recent toxicology studies suggest that nanosized aggregates of fullerene molecules can enter cells and alter their functions, and also cross the blood-brain barrier. However, the mechanisms by which fullerenes penetrate and disrupt cell membranes are still poorly understood. Here we use computer simulations to explore the translocation of fullerene clusters through a model lipid membrane and the effect of high fullerene concentrations on membrane properties. The fullerene molecules rapidly aggregate in water but disaggregate after entering the membrane interior. The permeation of a solid-like fullerene aggregate into the lipid bilayer is thermodynamically favoured and occurs on the microsecond timescale. High concentrations of fullerene induce changes in the structural and elastic properties of the lipid bilayer, but these are not large enough to mechanically damage the membrane. Our results suggest that mechanical damage is an unlikely mechanism for membrane disruption and fullerene toxicity.

The effect of a time delay on the transmission on dengue fever is studied. The time delay is due ... more The effect of a time delay on the transmission on dengue fever is studied. The time delay is due to the presence of an incubation period for the dengue virus to develop in the mosquito before the mosquito becomes infectious. The conditions for the existence of a Hopf bifurcation to limit cycle behavior are established. The conditions are different from the usual one and they are based on whether a particular third degree polynomial has positive real roots. A theorem for determining whether for a given set of parameter values, a critical delay time exist is given. It is found that for a set of realistic values of the parameters in the model, a Hopf bifurcation can not occur. For a set of unrealistic values of some of the parameters, it is shown that a Hopf bifurcation can occur. Numerical solutions using this last set show the trajectory of two of the variables making a transition from a spiraling orbit to a limit cycle orbit.

The Southeast Asian journal of tropical medicine and public health, 2001

The possibility of relapse is introduced into a mathematical model for the transmission of Plasmo... more The possibility of relapse is introduced into a mathematical model for the transmission of Plasmodium vivax malaria. In the model, the human population is divided into four classes: susceptible, infected, dormant and recovered. Loss of immunity by individuals in the recovered class moves these individuals back into the susceptible class. Two equilibrium states are found, a disease-free state and an endemic state. A basic reproduction number Ro is found. Depending on whether Ro is less than or greater than one. the disease free state or the endemic state results. The dependence of Ro on the rate of relapse is determined and the implication of this dependence is identified.

The Southeast Asian journal of tropical medicine and public health, 2004

The risk of dengue virus infection to travelers visiting dengue fever endemic regions was studied... more The risk of dengue virus infection to travelers visiting dengue fever endemic regions was studied through the use of mathematical modeling. A Susceptible-Infected-Recovered (SIR) model is used to describe the transmission of dengue fever (DF) in an endemic region into which tourists enter. The dynamics of a new class of human, the traveler, is incorporated into the systems of first order differential equations in the SIR describing the dynamics of the transmission in the host region. Using standard dynamic analysis methods, the numbers of travelers who become infected with the dengue virus are calculated as a function of the length of time the tourist stays in the region.

The Southeast Asian journal of tropical medicine and public health, 2001

The influence of age structure in the susceptible class of the Susceptible-Infected Recovered (SI... more The influence of age structure in the susceptible class of the Susceptible-Infected Recovered (SIR) model used to describe the transmission of dengue hemorrhagic fever (DHF) was studied. This was done by first dividing all of the population classes into cohorts and then writing a set of coupled SIR equations for each cohort. The consequences of assuming different behavior of the transmission rates on the age structure in the DHF incidence rates were determined. In order for the predicted incidence rates to be similar to the DHF incidence patterns observed in several provinces in Thailand during the DHF epidemic in 1998, the transmission rates should be age dependent.

Malaria is an infectious disease caused by the bite of female Anopheles mosquitoes. There are fou... more Malaria is an infectious disease caused by the bite of female Anopheles mosquitoes. There are four species, namely, Plasmodium vivax, Plasmodium falciparum, Plasmodium ovale and Plasmodium malariae causing human malaria. The difference between P.vivax malaria and P. falciparum malaria is that a person suffering from P. vivax infection can suffer relapses of the disease. The effect of a time delay on the transmission of this disease is studied. The time delay is the period in which the P.vivax parasite develops inside the mosquito (vector) before the vector becomes infectious (i.e., pass on the infection). The model is analyzed by using standard dynamic modeling method. Two stable equilibrium states are found to be possible. It is found that the disease free equilibrium state is stable when a newly defined basic reproduction number L is less than one. If L is greater than one, the endemic equilibrium state is stable. The conditions for the endemic equilibrium state to be a stable spi...

Journal of Low Temperature Physics, 1984

Using the approach of Matsuura, Ichinose, and Nagaoka to treat Anderson impurities dissolved in a... more Using the approach of Matsuura, Ichinose, and Nagaoka to treat Anderson impurities dissolved in a transition metal superconductor, the Kondo effect in a two-band superconductor is studied. It is found that the two-particle propagators for the superconductor are coupled to each other through thes- andd-electron vertex functions, which are obtained as solutions to a set of coupled Bethe-Salpeter equations. By rearranging some of the terms in the two-particle propagators, the pair-breaking parameters for thes andd electrons are obtained. An expression for the decrease in the transition temperature due to the Kondo scattering is obtained.

Journal of Bioscience and Bioengineering, 2004

The effects of the exposure of the bacterium, Leptospira interrogans serovar canicola to a consta... more The effects of the exposure of the bacterium, Leptospira interrogans serovar canicola to a constant magnetic field with magnetic flux density from a permanent ferrite magnet = 140±5 mT were stud ied. Changes in Leptospira cells after their exposure to the field were determined on the basis of changes in their growth behavior and agglutination immunoreactivity with a homologous antiserum using darkfield microscopy together with visual imaging. The data showed that the exposed Leptospira cells have lower densities and lower agglutination immunoreactivity than the unexposed control group. Interestingly, some of the exposed Leptospira cells showed abnormal morphologies such as large lengths. We discussed some of the possible reasons for these observations.

In this work, we consider a deterministic model for the transmission of leptospirosis which is cu... more In this work, we consider a deterministic model for the transmission of leptospirosis which is currently spreading in the Thai population. The SIR model which incorporates the features of this disease is applied to the epidemiological data in Thailand. It is seen that the numerical solutions of the SIR equations are in good agreement with real empirical data. Further improvements are discussed.

In this work, we consider a deterministic model for the transmission of leptospirosis which is cu... more In this work, we consider a deterministic model for the transmission of leptospirosis which is currently spreading in the Thai population. The SIR model which incorporates the features of this disease is applied to the epidemiological data in Thailand. It is seen that the numerical solutions of the SIR equations are in good agreement with real empirical data. Further improvements are discussed.

In this work, we consider a deterministic model for the transmission of leptospirosis which is cu... more In this work, we consider a deterministic model for the transmission of leptospirosis which is currently spreading in the Thai population. The SIR model which incorporates the features of this disease is applied to the epidemiological data in Thailand. It is seen that the numerical solutions of the SIR equations are in good agreement with real empirical data. Further improvements are discussed.

Journal of Low Temperature Physics, 1983

The effect of Anderson impurities on proximity effect tunneling into two-band metals such as pall... more The effect of Anderson impurities on proximity effect tunneling into two-band metals such as palladium is studied. The Yamada-Yosida approach is used to treat the Anderson impurities in the two-band metal. In the Kondo region, it is shown that the pair-breaking parameter for the d band mimics the pair-breaking parameter in the Miiller-Hartmann and Zittartz theory for low-Kondo-temperature alloys (Tc>>T~ but deviates from it for high-TK alloys. The change in the transition temperature of the proximity effect sandwich due to the presence of Anderson impurities in the two bands of the normal side appears to be similar to that obtained by Kaiser except for the presence of the new pair-breaking parameter.

Malaria is transmitted to the person by the biting of infectious Anopheles mosquitoes. This infec... more Malaria is transmitted to the person by the biting of infectious Anopheles mosquitoes. This infectious disease caused by the parasite genus Plasmodium. Four species of this parasite cause human malaria, namely, Plasmodium vivax, Plasmodium falciparum, Plasmodium ovale and Plasmodium malariae. The difference between P.vivax and P. falciparum is that a person suffering from P. vivax infection can suffer relapses of the disease. This is due the parasite being able to remain dormant in the liver of the cases where it is able to re-infect the case after a passage of time. During this stage, the case is classified as being in the dormant class. The model to describe the transmission between falciparum and vivax malaria consists of a human population divided into four classes, the susceptible, the infectious, the dormant and the recovered classes. The vector population is separated into two classes, the susceptible and infectious classes. We analyze our model by using standard dynamic mode...

Journal of Magnetism and Magnetic Materials, 2009

The magnetic properties of Co-ferrite-doped hydroxyapatite (HAP) nanoparticles of composition Ca ... more The magnetic properties of Co-ferrite-doped hydroxyapatite (HAP) nanoparticles of composition Ca 10À3x Fe 2x Co x (PO 4) 6 (OH) 2 (where x ¼ 0, 0.1, 0.2, 0.3, 0.4 and 0.5% mole) are studied. Transmission electron microscope micrograms show that the 90 nm size nanoparticles annealed at 1250 1C have a core/shell structure. Their electron diffraction patterns show that the shell is composed of the hydroxyapatite and the core is composed of the Co-ferrite, CoFe 2 O 4. Electron spin resonance measurements indicate that the Co 2+ ions are being substituted into the Ca(1) sites in HAP lattice. X-ray diffraction studies show the formation of impurity phases as higher amounts of the Fe 3+ /Co 2+ ions which are substituted into the HAP host matrix. The presence of two sextets (one for the A-site Fe 3+ and the other for the B-site Fe 3+) in the Mö ssbauer spectrum for all the doped samples clearly indicates that the CoFe 2 O 4 .cores are in the ferromagnetic state. Evidence of the impurity phases is seen in the appearance of doublet patterns in the Mö ssbauer spectrums for the heavier-doped (x ¼ 0.4 and 0.5) specimens. The decrease in the saturation magnetizations and other magnetic properties of the nanoparticles at the higher doping levels is consistent with some of the Fe 3+ and Co 2+ which being used to form the CoO and Fe 2 O 3 impurity phase seen in the XRD patterns.

Nature Nanotechnology, 2008

Recent toxicology studies suggest that nanosized aggregates of fullerene molecules can enter cell... more Recent toxicology studies suggest that nanosized aggregates of fullerene molecules can enter cells and alter their functions, and also cross the blood-brain barrier. However, the mechanisms by which fullerenes penetrate and disrupt cell membranes are still poorly understood. Here we use computer simulations to explore the translocation of fullerene clusters through a model lipid membrane and the effect of high fullerene concentrations on membrane properties. The fullerene molecules rapidly aggregate in water but disaggregate after entering the membrane interior. The permeation of a solid-like fullerene aggregate into the lipid bilayer is thermodynamically favoured and occurs on the microsecond timescale. High concentrations of fullerene induce changes in the structural and elastic properties of the lipid bilayer, but these are not large enough to mechanically damage the membrane. Our results suggest that mechanical damage is an unlikely mechanism for membrane disruption and fullerene toxicity.

The effect of a time delay on the transmission on dengue fever is studied. The time delay is due ... more The effect of a time delay on the transmission on dengue fever is studied. The time delay is due to the presence of an incubation period for the dengue virus to develop in the mosquito before the mosquito becomes infectious. The conditions for the existence of a Hopf bifurcation to limit cycle behavior are established. The conditions are different from the usual one and they are based on whether a particular third degree polynomial has positive real roots. A theorem for determining whether for a given set of parameter values, a critical delay time exist is given. It is found that for a set of realistic values of the parameters in the model, a Hopf bifurcation can not occur. For a set of unrealistic values of some of the parameters, it is shown that a Hopf bifurcation can occur. Numerical solutions using this last set show the trajectory of two of the variables making a transition from a spiraling orbit to a limit cycle orbit.

The Southeast Asian journal of tropical medicine and public health, 2001

The possibility of relapse is introduced into a mathematical model for the transmission of Plasmo... more The possibility of relapse is introduced into a mathematical model for the transmission of Plasmodium vivax malaria. In the model, the human population is divided into four classes: susceptible, infected, dormant and recovered. Loss of immunity by individuals in the recovered class moves these individuals back into the susceptible class. Two equilibrium states are found, a disease-free state and an endemic state. A basic reproduction number Ro is found. Depending on whether Ro is less than or greater than one. the disease free state or the endemic state results. The dependence of Ro on the rate of relapse is determined and the implication of this dependence is identified.

The Southeast Asian journal of tropical medicine and public health, 2004

The risk of dengue virus infection to travelers visiting dengue fever endemic regions was studied... more The risk of dengue virus infection to travelers visiting dengue fever endemic regions was studied through the use of mathematical modeling. A Susceptible-Infected-Recovered (SIR) model is used to describe the transmission of dengue fever (DF) in an endemic region into which tourists enter. The dynamics of a new class of human, the traveler, is incorporated into the systems of first order differential equations in the SIR describing the dynamics of the transmission in the host region. Using standard dynamic analysis methods, the numbers of travelers who become infected with the dengue virus are calculated as a function of the length of time the tourist stays in the region.

The Southeast Asian journal of tropical medicine and public health, 2001

The influence of age structure in the susceptible class of the Susceptible-Infected Recovered (SI... more The influence of age structure in the susceptible class of the Susceptible-Infected Recovered (SIR) model used to describe the transmission of dengue hemorrhagic fever (DHF) was studied. This was done by first dividing all of the population classes into cohorts and then writing a set of coupled SIR equations for each cohort. The consequences of assuming different behavior of the transmission rates on the age structure in the DHF incidence rates were determined. In order for the predicted incidence rates to be similar to the DHF incidence patterns observed in several provinces in Thailand during the DHF epidemic in 1998, the transmission rates should be age dependent.

Malaria is an infectious disease caused by the bite of female Anopheles mosquitoes. There are fou... more Malaria is an infectious disease caused by the bite of female Anopheles mosquitoes. There are four species, namely, Plasmodium vivax, Plasmodium falciparum, Plasmodium ovale and Plasmodium malariae causing human malaria. The difference between P.vivax malaria and P. falciparum malaria is that a person suffering from P. vivax infection can suffer relapses of the disease. The effect of a time delay on the transmission of this disease is studied. The time delay is the period in which the P.vivax parasite develops inside the mosquito (vector) before the vector becomes infectious (i.e., pass on the infection). The model is analyzed by using standard dynamic modeling method. Two stable equilibrium states are found to be possible. It is found that the disease free equilibrium state is stable when a newly defined basic reproduction number L is less than one. If L is greater than one, the endemic equilibrium state is stable. The conditions for the endemic equilibrium state to be a stable spi...

Journal of Low Temperature Physics, 1984

Using the approach of Matsuura, Ichinose, and Nagaoka to treat Anderson impurities dissolved in a... more Using the approach of Matsuura, Ichinose, and Nagaoka to treat Anderson impurities dissolved in a transition metal superconductor, the Kondo effect in a two-band superconductor is studied. It is found that the two-particle propagators for the superconductor are coupled to each other through thes- andd-electron vertex functions, which are obtained as solutions to a set of coupled Bethe-Salpeter equations. By rearranging some of the terms in the two-particle propagators, the pair-breaking parameters for thes andd electrons are obtained. An expression for the decrease in the transition temperature due to the Kondo scattering is obtained.

Journal of Bioscience and Bioengineering, 2004

The effects of the exposure of the bacterium, Leptospira interrogans serovar canicola to a consta... more The effects of the exposure of the bacterium, Leptospira interrogans serovar canicola to a constant magnetic field with magnetic flux density from a permanent ferrite magnet = 140±5 mT were stud ied. Changes in Leptospira cells after their exposure to the field were determined on the basis of changes in their growth behavior and agglutination immunoreactivity with a homologous antiserum using darkfield microscopy together with visual imaging. The data showed that the exposed Leptospira cells have lower densities and lower agglutination immunoreactivity than the unexposed control group. Interestingly, some of the exposed Leptospira cells showed abnormal morphologies such as large lengths. We discussed some of the possible reasons for these observations.

In this work, we consider a deterministic model for the transmission of leptospirosis which is cu... more In this work, we consider a deterministic model for the transmission of leptospirosis which is currently spreading in the Thai population. The SIR model which incorporates the features of this disease is applied to the epidemiological data in Thailand. It is seen that the numerical solutions of the SIR equations are in good agreement with real empirical data. Further improvements are discussed.

In this work, we consider a deterministic model for the transmission of leptospirosis which is cu... more In this work, we consider a deterministic model for the transmission of leptospirosis which is currently spreading in the Thai population. The SIR model which incorporates the features of this disease is applied to the epidemiological data in Thailand. It is seen that the numerical solutions of the SIR equations are in good agreement with real empirical data. Further improvements are discussed.

In this work, we consider a deterministic model for the transmission of leptospirosis which is cu... more In this work, we consider a deterministic model for the transmission of leptospirosis which is currently spreading in the Thai population. The SIR model which incorporates the features of this disease is applied to the epidemiological data in Thailand. It is seen that the numerical solutions of the SIR equations are in good agreement with real empirical data. Further improvements are discussed.