Prem Vaishnava - Academia.edu (original) (raw)

Papers by Prem Vaishnava

Advances in Superconductivity IV, 1992

The present investigation was performed with a purpose to study the effect of silver substitution... more The present investigation was performed with a purpose to study the effect of silver substitution and addition on the transition temperature, the Meissner fraction and the diamagnetic shielding of Pb2Sr2Y0.5Ca0.5Cu3O8+z superconductor. Samples were prepared by substitution (Cu depletion) and addition of silver to the title superconductor. X-ray diffraction measurements indicated that all the samples were single phase materials. Energy dispersive X-ray measurements were performed to determine exact amounts of the elements in the samples. From magnetic measurements, which were performed between 10 and 300 K using a SQUID magnetometer, it was found that both diamagnetic shielding and the Meissner fraction decreased by substitution and addition of silver to the superconductor. Superconducting transition temperature and the lattice parameters were not affected.

Journal of the Less Common Metals, 1987

MRS Proceedings, 1982

ABSTRACTIn situ 57Fe Mössbauer spectra are reported for the first-, higher-stage ferric chloride,... more ABSTRACTIn situ 57Fe Mössbauer spectra are reported for the first-, higher-stage ferric chloride, and a mixed ferric chloride-potassium chloride intercalated graphite catalysts under reduction and Fischer-Tropsch reaction conditions. The mass spectroscopic measurements reveal a different catalytic selectivity for the three catalysts. The first two catalysts predominantly possess a higher selectivity for methane, whereas the third catalyst has higher selectivity for the formation of propane. The differences are attributed to geometrical effects in the catalytic sites of the intercalated compounds.

We propose to synthesize and characterize magnetic microbubbles for examining the use of magnetic... more We propose to synthesize and characterize magnetic microbubbles for examining the use of magnetic microbubbles for targeted drug delivery. Using magnetic microbubbles as carriers, we will test how well drugs can be dispersed by means of ultrasound and hyperthermia

Bulletin of the American Physical Society, 2016

Submitted for the MAR16 Meeting of The American Physical Society A comparison of methods for the ... more Submitted for the MAR16 Meeting of The American Physical Society A comparison of methods for the determination of the magneotcrystalline anisotropy constant in an Fe 3 O 4-based ferrofluid RONALD TACKETT, MEGAN ALLYN, Kettering University, VIJAYENDRA GARG, ADERBAL DE OLIVEIRA, University of Brasilia, PREM VAISHNAVA, Kettering University-The dynamics of the relaxation behavior of superparamagnetic nanoparticles is governed by many factors such as the anisotropy constant, composition, size and nature of coating of the nanoparticles particles. We report values of the anisotropy constant (K) for magnetite nanoparticle (size ∼12 nm) coated with dextran and suspended in water by dc and ac magnetization measurements, MOssbauer spectroscopy and the temperature dependent specific absorption rate (SAR) measurement. The magnetite nanoparticles were synthesized by co-precipitation and characterized by X-ray diffraction (XRD) and Transmission electron microscopy (TEM). The K values from dc magnetic susceptibility, MOssbauer spectroscopy, ac magnetic susceptibility, and that obtained by temperature dependent SAR measurements are all within the range of the accepted values in the literature. Merits and demerits of the four methods of determining K values will be discussed. We will also report on the temperature dependence of the anisotropy constant and the NEel relaxation constant.

Magnetic induction heating of iron oxide nanoparticles has been proposed as a method for noninvas... more Magnetic induction heating of iron oxide nanoparticles has been proposed as a method for noninvasive cancer treatment without the side effects of chemotherapy and ionizing radiation. At Kettering University we propose to improve the uptake of nanoparticles by cells through the use of nanoparticle engineering and ultrasonic fields.

Journal of Nanoparticle Research, 2011

We have synthesized iron oxide nanoparticles coated with a monolayer of dextran, with molecular w... more We have synthesized iron oxide nanoparticles coated with a monolayer of dextran, with molecular weights of the polymer between 5 and 670 kDa. Transmission electron microscopy images confirm that the hard core has a crystalline diameter of approximately 12 nm. The hydrodynamic diameters of these coated nanoparticles in solution measured using dynamical light scattering and estimated from magnetic susceptibility studies vary from near 90 nm for the lightest polymer to 140 nm for the heaviest polymer. Conversely, fluorescence correlation spectroscopy measurements yield a diameter of approximately 55 nm for the 15-20 kDa dextran coated nanoparticles, which is consistent with the expected value estimated from the sum of the hard-core diameter and monolayer dextran coating. We discuss the implications of this discrepancy for applications involving polymer-coated magnetic nanoparticles.

Journal of Power Sources, 2016

h i g h l i g h t s A new process is developed for preparation of conductive carbon coated LiFePO... more h i g h l i g h t s A new process is developed for preparation of conductive carbon coated LiFePO 4. Excess lithium significantly improved the electrochemical performance of LiFePO 4. M€ ossbauer spectroscopy identifies the presence of new impurity phases. LiFePO 4 with excess lithium made in presence of surfactant is a promising cathode.

We report a novel method of determining the average Neel relaxation time and its temperature depe... more We report a novel method of determining the average Neel relaxation time and its temperature dependence by calculating derivatives of the measured time dependence of temperature for a frozen ferrofluid exposed to an alternating magnetic field. The ferrofluid, composed of dextran-coated Fe3O4 nanoparticles (diameter 13.7 nm +/- 4.7 nm), was synthesized via wet chemical precipitation and characterized by x-ray diffraction and transmission electron microscopy. An alternating magnetic field of constant amplitude (H0 = 20 kA/m) driven at frequencies of 171 kHz, 232 kHz and 343 kHz was used to determine the temperature dependent magnetic energy absorption rate in the temperature range from 160 K to 210 K. We found that the specific absorption rate of the ferrofluid decreased monotonically with temperature over this range at the given frequencies. From these measured data, we determined the temperature dependence of the Neel relaxation time and estimate a room-temperature magnetocrystallin...

Nanostructured Materials - Fabrication to Applications

Nanotechnology has facilitated the applications of a class of nanomaterials called superparamagne... more Nanotechnology has facilitated the applications of a class of nanomaterials called superparamagnetic iron oxide nanoparticles (SPIONs) in cancer theranostics. This is a new discipline in biomedicine that combines therapy and diagnosis in one platform. The multifunctional SPIONs, which are capable of detecting, visualizing, and destroying the neoplastic cells with fewer side effects than the conventional therapies, are reviewed in this chapter for theranostic applications. The chapter summarizes the design parameters such as size, shape, coating, and target ligand functionalization of SPIONs, which enhance their ability to diagnose and treat cancer. The review discusses the methods of synthesizing SPIONs, their structural, morphological, and magnetic properties that are important for theranostics. The applications of SPIONs for drug delivery, magnetic resonance imaging, and magnetic hyperthermia therapy (MHT) are included. The results of our recent MHT study on Gd-doped SPION as a possible theranostic agent are highlighted. We have also discussed the challenges and outlook on the future research for theranostics in clinical settings.

International Journal of Applied Electromagnetics and Mechanics

Many induction heating coils use soft magnetic composite materials (SMCs) to improve induction sy... more Many induction heating coils use soft magnetic composite materials (SMCs) to improve induction system performance. In demanding induction heating applications, the core loss in the soft magnetic composite material is one of the critical factors in predicting the reliability of the induction coil using computer modelling. In this paper we have used calorimetry method for experimentally determining core losses in SMCs up to ≈1 T magnetic flux densities at a frequency near 150 kHz. This paper contains a discussion on the limitations of current methods for calculating core losses. To address these limitations, a new method for calculating core losses is presented. Using the new method, the results of the core loss measurement did not fit well with traditional core loss models over the full range of magnetic flux densities. A discussion on the different models and a hypothesis for the source of the variation from the models is presented.

Translational Vision Science & Technology

Purpose: To evaluate selective apoptosis of Y79 retinoblastoma versus ARPE-19 retinal pigment epi... more Purpose: To evaluate selective apoptosis of Y79 retinoblastoma versus ARPE-19 retinal pigment epithelial cells by using different doses of dextran-coated iron oxide nanoparticles (DCIONs) in a magnetic hyperthermia paradigm. Methods: Y79 and ARPE-19 cells were exposed to different concentrations of DCIONs, namely, 0.25, 0.5, 0.75, and 1 mg/ml. After 2 hours of incubation, cells were exposed to a magnetic field with a frequency of 250 kHz and an amplitude of 4 kA/m for 30 minutes to raise the cellular temperature between 42 and 468C. Y79 and ARPE-19 cells incubated with DCION without magnetic field exposure were used as controls. Cell viability and apoptosis were assessed at 4, 24, and 72 hours after hyperthermia treatment. Results: At 4 hours following magnetic hyperthermia, cell death for Y79 cells was 1%, 8%, 17%, and 17% for 0.25, 0.5, 0.75 and 1 mg/ml of DCION, respectively. Cell death increased to 47%, 59%, 70%, and 75% at 24 hours and 16%, 45%, 50%, and 56% at 72 hours for 0.25, 0.5, 0.75, and 1 mg/ml of DCIONs, respectively. Magnetic hyperthermia did not have any significant toxic effects on ARPE-19 cells at all DCION concentrations, and minimal baseline cytotoxicity of DCIONs on Y79 and ARPE-19 cells was observed without magnetic field activation. Gene expression profiling showed that genes involved in FAS and tumor necrosis factor alpha signaling pathways were activated in Y79 cells following hyperthermia. Caspase 3/7 activity in Y79 cells increased following treatment, consistent with the activation of caspase-mediated apoptosis and loss of cell viability by magnetic hyperthermia. Conclusion: Magnetic hyperthermia using DCIONs selectively kills Y79 cells at 0.5 mg/ ml or higher concentrations via the activation of apoptotic pathways. Translational Relevance: Magnetic hyperthermia using DCIONs might play a role in targeted management of retinoblastoma.

Nanofluid Heat and Mass Transfer in Engineering Problems, 2017

The temperature dependence of the Moessbauer effect has been measured at ¹¹⁹Sn sites in oxyge... more The temperature dependence of the Moessbauer effect has been measured at ¹¹⁹Sn sites in oxygen-free, SnMoâSâ (T/sub c/ = 14.2K) and in oxygen substituted SnMoâSâ âOâ â (T/sub c/ = 10.1K). The temperature dependence of the asymmetry of the quadrupole doublet for SnMoâSâ shows phonon anomalies near 50 and 120K. <z²> /sub T/ indicates contraction with increasing temperature between 4.3 and 50K. For the oxygen substituted compound a study of the variation of mean square displacement with temperature shows lattice softening near 120K.

Journal of Materials Chemistry, 2010

... groups to promote iron oxide nanoparticle attachment. The mixture was refluxed under the same... more ... groups to promote iron oxide nanoparticle attachment. The mixture was refluxed under the same condition for 4 h. After this procedure, the microgels were dialyzed in de-ionized water for two days, freeze dried, and preserved at room temperature. The microgel sample obtained ...

Applied Physics Letters, 2008

Iron oxide having the magnetite structure is a widely used biomaterial, having applications rangi... more Iron oxide having the magnetite structure is a widely used biomaterial, having applications ranging from cell separation and drug delivery to hyperthermia. In order to increase the efficacy of drug treatments, magnetite nanoparticles can be incorporated into a composite system with a surfactant-polymer nanoparticle, which can act as a platform for sustained and enhanced cellular delivery of water-soluble molecules. Here

Advances in Superconductivity IV, 1992

The present investigation was performed with a purpose to study the effect of silver substitution... more The present investigation was performed with a purpose to study the effect of silver substitution and addition on the transition temperature, the Meissner fraction and the diamagnetic shielding of Pb2Sr2Y0.5Ca0.5Cu3O8+z superconductor. Samples were prepared by substitution (Cu depletion) and addition of silver to the title superconductor. X-ray diffraction measurements indicated that all the samples were single phase materials. Energy dispersive X-ray measurements were performed to determine exact amounts of the elements in the samples. From magnetic measurements, which were performed between 10 and 300 K using a SQUID magnetometer, it was found that both diamagnetic shielding and the Meissner fraction decreased by substitution and addition of silver to the superconductor. Superconducting transition temperature and the lattice parameters were not affected.

Journal of the Less Common Metals, 1987

MRS Proceedings, 1982

ABSTRACTIn situ 57Fe Mössbauer spectra are reported for the first-, higher-stage ferric chloride,... more ABSTRACTIn situ 57Fe Mössbauer spectra are reported for the first-, higher-stage ferric chloride, and a mixed ferric chloride-potassium chloride intercalated graphite catalysts under reduction and Fischer-Tropsch reaction conditions. The mass spectroscopic measurements reveal a different catalytic selectivity for the three catalysts. The first two catalysts predominantly possess a higher selectivity for methane, whereas the third catalyst has higher selectivity for the formation of propane. The differences are attributed to geometrical effects in the catalytic sites of the intercalated compounds.

We propose to synthesize and characterize magnetic microbubbles for examining the use of magnetic... more We propose to synthesize and characterize magnetic microbubbles for examining the use of magnetic microbubbles for targeted drug delivery. Using magnetic microbubbles as carriers, we will test how well drugs can be dispersed by means of ultrasound and hyperthermia

Bulletin of the American Physical Society, 2016

Submitted for the MAR16 Meeting of The American Physical Society A comparison of methods for the ... more Submitted for the MAR16 Meeting of The American Physical Society A comparison of methods for the determination of the magneotcrystalline anisotropy constant in an Fe 3 O 4-based ferrofluid RONALD TACKETT, MEGAN ALLYN, Kettering University, VIJAYENDRA GARG, ADERBAL DE OLIVEIRA, University of Brasilia, PREM VAISHNAVA, Kettering University-The dynamics of the relaxation behavior of superparamagnetic nanoparticles is governed by many factors such as the anisotropy constant, composition, size and nature of coating of the nanoparticles particles. We report values of the anisotropy constant (K) for magnetite nanoparticle (size ∼12 nm) coated with dextran and suspended in water by dc and ac magnetization measurements, MOssbauer spectroscopy and the temperature dependent specific absorption rate (SAR) measurement. The magnetite nanoparticles were synthesized by co-precipitation and characterized by X-ray diffraction (XRD) and Transmission electron microscopy (TEM). The K values from dc magnetic susceptibility, MOssbauer spectroscopy, ac magnetic susceptibility, and that obtained by temperature dependent SAR measurements are all within the range of the accepted values in the literature. Merits and demerits of the four methods of determining K values will be discussed. We will also report on the temperature dependence of the anisotropy constant and the NEel relaxation constant.

Magnetic induction heating of iron oxide nanoparticles has been proposed as a method for noninvas... more Magnetic induction heating of iron oxide nanoparticles has been proposed as a method for noninvasive cancer treatment without the side effects of chemotherapy and ionizing radiation. At Kettering University we propose to improve the uptake of nanoparticles by cells through the use of nanoparticle engineering and ultrasonic fields.

Journal of Nanoparticle Research, 2011

We have synthesized iron oxide nanoparticles coated with a monolayer of dextran, with molecular w... more We have synthesized iron oxide nanoparticles coated with a monolayer of dextran, with molecular weights of the polymer between 5 and 670 kDa. Transmission electron microscopy images confirm that the hard core has a crystalline diameter of approximately 12 nm. The hydrodynamic diameters of these coated nanoparticles in solution measured using dynamical light scattering and estimated from magnetic susceptibility studies vary from near 90 nm for the lightest polymer to 140 nm for the heaviest polymer. Conversely, fluorescence correlation spectroscopy measurements yield a diameter of approximately 55 nm for the 15-20 kDa dextran coated nanoparticles, which is consistent with the expected value estimated from the sum of the hard-core diameter and monolayer dextran coating. We discuss the implications of this discrepancy for applications involving polymer-coated magnetic nanoparticles.

Journal of Power Sources, 2016

h i g h l i g h t s A new process is developed for preparation of conductive carbon coated LiFePO... more h i g h l i g h t s A new process is developed for preparation of conductive carbon coated LiFePO 4. Excess lithium significantly improved the electrochemical performance of LiFePO 4. M€ ossbauer spectroscopy identifies the presence of new impurity phases. LiFePO 4 with excess lithium made in presence of surfactant is a promising cathode.

We report a novel method of determining the average Neel relaxation time and its temperature depe... more We report a novel method of determining the average Neel relaxation time and its temperature dependence by calculating derivatives of the measured time dependence of temperature for a frozen ferrofluid exposed to an alternating magnetic field. The ferrofluid, composed of dextran-coated Fe3O4 nanoparticles (diameter 13.7 nm +/- 4.7 nm), was synthesized via wet chemical precipitation and characterized by x-ray diffraction and transmission electron microscopy. An alternating magnetic field of constant amplitude (H0 = 20 kA/m) driven at frequencies of 171 kHz, 232 kHz and 343 kHz was used to determine the temperature dependent magnetic energy absorption rate in the temperature range from 160 K to 210 K. We found that the specific absorption rate of the ferrofluid decreased monotonically with temperature over this range at the given frequencies. From these measured data, we determined the temperature dependence of the Neel relaxation time and estimate a room-temperature magnetocrystallin...

Nanostructured Materials - Fabrication to Applications

Nanotechnology has facilitated the applications of a class of nanomaterials called superparamagne... more Nanotechnology has facilitated the applications of a class of nanomaterials called superparamagnetic iron oxide nanoparticles (SPIONs) in cancer theranostics. This is a new discipline in biomedicine that combines therapy and diagnosis in one platform. The multifunctional SPIONs, which are capable of detecting, visualizing, and destroying the neoplastic cells with fewer side effects than the conventional therapies, are reviewed in this chapter for theranostic applications. The chapter summarizes the design parameters such as size, shape, coating, and target ligand functionalization of SPIONs, which enhance their ability to diagnose and treat cancer. The review discusses the methods of synthesizing SPIONs, their structural, morphological, and magnetic properties that are important for theranostics. The applications of SPIONs for drug delivery, magnetic resonance imaging, and magnetic hyperthermia therapy (MHT) are included. The results of our recent MHT study on Gd-doped SPION as a possible theranostic agent are highlighted. We have also discussed the challenges and outlook on the future research for theranostics in clinical settings.

International Journal of Applied Electromagnetics and Mechanics

Many induction heating coils use soft magnetic composite materials (SMCs) to improve induction sy... more Many induction heating coils use soft magnetic composite materials (SMCs) to improve induction system performance. In demanding induction heating applications, the core loss in the soft magnetic composite material is one of the critical factors in predicting the reliability of the induction coil using computer modelling. In this paper we have used calorimetry method for experimentally determining core losses in SMCs up to ≈1 T magnetic flux densities at a frequency near 150 kHz. This paper contains a discussion on the limitations of current methods for calculating core losses. To address these limitations, a new method for calculating core losses is presented. Using the new method, the results of the core loss measurement did not fit well with traditional core loss models over the full range of magnetic flux densities. A discussion on the different models and a hypothesis for the source of the variation from the models is presented.

Translational Vision Science & Technology

Purpose: To evaluate selective apoptosis of Y79 retinoblastoma versus ARPE-19 retinal pigment epi... more Purpose: To evaluate selective apoptosis of Y79 retinoblastoma versus ARPE-19 retinal pigment epithelial cells by using different doses of dextran-coated iron oxide nanoparticles (DCIONs) in a magnetic hyperthermia paradigm. Methods: Y79 and ARPE-19 cells were exposed to different concentrations of DCIONs, namely, 0.25, 0.5, 0.75, and 1 mg/ml. After 2 hours of incubation, cells were exposed to a magnetic field with a frequency of 250 kHz and an amplitude of 4 kA/m for 30 minutes to raise the cellular temperature between 42 and 468C. Y79 and ARPE-19 cells incubated with DCION without magnetic field exposure were used as controls. Cell viability and apoptosis were assessed at 4, 24, and 72 hours after hyperthermia treatment. Results: At 4 hours following magnetic hyperthermia, cell death for Y79 cells was 1%, 8%, 17%, and 17% for 0.25, 0.5, 0.75 and 1 mg/ml of DCION, respectively. Cell death increased to 47%, 59%, 70%, and 75% at 24 hours and 16%, 45%, 50%, and 56% at 72 hours for 0.25, 0.5, 0.75, and 1 mg/ml of DCIONs, respectively. Magnetic hyperthermia did not have any significant toxic effects on ARPE-19 cells at all DCION concentrations, and minimal baseline cytotoxicity of DCIONs on Y79 and ARPE-19 cells was observed without magnetic field activation. Gene expression profiling showed that genes involved in FAS and tumor necrosis factor alpha signaling pathways were activated in Y79 cells following hyperthermia. Caspase 3/7 activity in Y79 cells increased following treatment, consistent with the activation of caspase-mediated apoptosis and loss of cell viability by magnetic hyperthermia. Conclusion: Magnetic hyperthermia using DCIONs selectively kills Y79 cells at 0.5 mg/ ml or higher concentrations via the activation of apoptotic pathways. Translational Relevance: Magnetic hyperthermia using DCIONs might play a role in targeted management of retinoblastoma.

Nanofluid Heat and Mass Transfer in Engineering Problems, 2017

The temperature dependence of the Moessbauer effect has been measured at ¹¹⁹Sn sites in oxyge... more The temperature dependence of the Moessbauer effect has been measured at ¹¹⁹Sn sites in oxygen-free, SnMoâSâ (T/sub c/ = 14.2K) and in oxygen substituted SnMoâSâ âOâ â (T/sub c/ = 10.1K). The temperature dependence of the asymmetry of the quadrupole doublet for SnMoâSâ shows phonon anomalies near 50 and 120K. <z²> /sub T/ indicates contraction with increasing temperature between 4.3 and 50K. For the oxygen substituted compound a study of the variation of mean square displacement with temperature shows lattice softening near 120K.

Journal of Materials Chemistry, 2010

... groups to promote iron oxide nanoparticle attachment. The mixture was refluxed under the same... more ... groups to promote iron oxide nanoparticle attachment. The mixture was refluxed under the same condition for 4 h. After this procedure, the microgels were dialyzed in de-ionized water for two days, freeze dried, and preserved at room temperature. The microgel sample obtained ...

Applied Physics Letters, 2008

Iron oxide having the magnetite structure is a widely used biomaterial, having applications rangi... more Iron oxide having the magnetite structure is a widely used biomaterial, having applications ranging from cell separation and drug delivery to hyperthermia. In order to increase the efficacy of drug treatments, magnetite nanoparticles can be incorporated into a composite system with a surfactant-polymer nanoparticle, which can act as a platform for sustained and enhanced cellular delivery of water-soluble molecules. Here