surya gupta - Academia.edu (original) (raw)
Papers by surya gupta
Solid State Sciences, 2013
ABSTRACT BiFeO3 sample prepared by rapid liquid phase sintering (RLPS) technique is found to poss... more ABSTRACT BiFeO3 sample prepared by rapid liquid phase sintering (RLPS) technique is found to posses better dielectric properties than the subsequently annealed sample. These samples also show ferromagnetism at room temperature. Detailed X-ray diffraction and Rietveld refinement of the data show that oxygen–iron–oxygen (O–Fe–O) bond angle is considerably more distorted in samples prepared by rapid liquid-phase sintering technique than in the annealed sample. In addition, synchrotron X-ray diffraction as well as high resolution transmission electron microscopy studies show higher concentration of impurity phases in the annealed samples, which is the likely reason for inferior dielectric properties. Further transmission electron microscopy results indicate that high crystalline order is not necessary for better dielectric properties. However weak ferromagnetism is observed in all these samples and appears to be the intrinsic property of samples prepared by rapid liquid phase sintering technique.
Journal of Physics and Chemistry …, 2008
Investigations have been performed on lanthanum-modified layered ferroelectric bismuth titanate f... more Investigations have been performed on lanthanum-modified layered ferroelectric bismuth titanate for composition Bi 3.25 La 0.75 Ti 3 O 12 (BLT) using impedance spectroscopy to understand the role of microstructure on the dielectric properties of this important material. A wide range of frequency and a wide range of temperature passing through the Curie point were chosen for the measurement. The frequency dependence suggested an interfacial polarization controlled Maxwell-Wagner type relaxation at low frequencies, and the impedance spectrum correlated with the mathematical fitting indicated the presence of two types of interfaces, which were attributed to the metallurgical boundaries and the twinned planes parallel to the bismuth oxide layers inherent to the crystal structure within the metallurgical grains. A careful analysis of the dielectric properties, particularly the ac-conductivity analysis revealed that the grain boundaries did also follow their own Jonscher-like relaxation, and the overall relaxation of the sample changed to a purely grain boundary-limited response at low frequency to a pure grain-limited response at higher frequencies. And overall admittance of the ceramic sample neither follow unmodified nor modified Jonscher's law rather its behaviour can be well described by series addition of Jonscher's admittance corresponding to grain boundary and grain. It was demonstrated that the frequency response of the ac conductivity was related to the microstructure exactly in the same way as any other dielectric function, like the impedance or dielectric constant, a fact, which is not much emphasized in the open literature. r
World journal of clinical pediatrics, Jan 8, 2015
Complicated migraine encompasses several individual clinical syndromes of migraine. Such a syndro... more Complicated migraine encompasses several individual clinical syndromes of migraine. Such a syndrome in children frequently presents with various neurological symptoms in the Emergency Department. An acute presentation in the absence of headache presents a diagnostic challenge. A delay in diagnosis and treatment may have medicolegal implication. To date, there are no reports of a common clinical profile proposed in making a clinical diagnosis for the complicated migraine. In this clinical review, we propose and describe: (1) A common clinical profile in aid to clinical diagnosis for spectrum of complicated migraine; (2) How it can be used in differentiating complicated migraine from migraine without aura, migraine with aura, and seizure; (3) We discuss the status of complicated migraine in the International Headache Society classification 2013; and (4) In addition, a common treatment strategy for the spectrum of migraine has been described. To diagnose complicated migraine clinically...
Medicine, 2005
Fabry disease is a rare X-linked lysosomal storage disorder caused by deficient activity of alpha... more Fabry disease is a rare X-linked lysosomal storage disorder caused by deficient activity of alpha-galactosidase A (alpha-Gal A) resulting in the storage of glycosphingolipids, especially globotriaosylceramide (Gb3), in cells throughout the body, causing life-threatening renal, cardiac, and cerebrovascular complications in hemizygous males and some heterozygous females. Disease manifestations in heterozygotes are being recognized increasingly, but quantitative prospective data on their extent and severity are limited. Prospective clinical and laboratory assessments were performed in a 7-day study of 61 women with signs and symptoms of Fabry disease. Analyses included medical history and physical, neurologic, cardiac, and ophthalmologic assessments; laboratory assessments; renal function tests; magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) of the head; and Fabry-related blood and urine tests, including Gb3 levels in blood and urine, skin biopsies, and DNA g...
Solid State Communications, 2004
... Shape-memory effect in PMN-PT(65/35) ceramic. Pragya Pandit, Surya M. Gupta Corresponding Aut... more ... Shape-memory effect in PMN-PT(65/35) ceramic. Pragya Pandit, Surya M. Gupta Corresponding Author Contact Information , E-mail The Corresponding Author and Vinod K. Wadhawan. Laser Materials Division, Centre for Advanced Technology, Indore 245013, India. ...
Pramana, 2008
AC impedance spectroscopy technique has been used to study electrical properties of Bi 3.25 La 0.... more AC impedance spectroscopy technique has been used to study electrical properties of Bi 3.25 La 0.75 Ti 3 O 12 (BLT) ceramic. Complex impedance plots were fitted with three depressed semicircles, which are attributed to crystalline layer, plate boundary and grain boundary and all three were found to comprise of universal capacitance nature [C = C0w n−1 ]. Grain boundary resistance and capacitance evaluated from complex impedance plots have larger values than that of plate boundary and crystalline layer. The activation energies (E a ) for DC-conductance in grain boundary, plate boundary and crystalline layer are 0.68 eV, 0.89 eV and 0.89 eV, respectively. Relaxation activation energies calculated from impedance plots showed similar values, 0.81 eV and 0.80 eV for crystalline layer and plate boundary, respectively. These activation energy values are found to be consistent with the E a value of oxygen vacancies in perovskite materials. A mechanism is offered to explain the generation of oxygen vacancies in BLT ceramic and its role in temperature dependence of DC-conductance study.
Neurology, 2002
Mucolipidosis type IV (MLIV) is an autosomal recessive disease caused by mutations in the MCOLN1 ... more Mucolipidosis type IV (MLIV) is an autosomal recessive disease caused by mutations in the MCOLN1 gene that codes for mucolipin, a member of the transient receptor potential (TRP) gene family. To comprehensively characterize the clinical and genetic abnormalities of MLIV. Twenty-eight patients with MLIV, aged 2 to 25 years, were studied. Ten returned for follow-up every 1 to 2 years for up to 5 years. Standard clinical, neuroimaging, neurophysiologic, and genetic techniques were used. All patients had varying degrees of corneal clouding, with progressive optic atrophy and retinal dystrophy. Twenty-three patients had severe motor and mental impairment. Motor function deteriorated in three patients and remained stable in the rest. All had a constitutive achlorhydria with elevated plasma gastrin level, and 12 had iron deficiency or anemia. Head MRI showed consistent characteristic findings of a thin corpus callosum and remained unchanged during the follow-up period. Prominent abnormalities of speech, hand usage, and swallowing were also noted. Mutations in the MCOLN1 gene were present in all patients. Correlation of the genotype with the neurologic handicap and corpus callosum dysplasia was found. MLIV is both a developmental and a degenerative disorder. The presentation as a cerebral palsy-like encephalopathy may delay diagnosis.
Medicine, 2005
Fabry disease is a rare X-linked lysosomal storage disorder caused by deficient activity of alpha... more Fabry disease is a rare X-linked lysosomal storage disorder caused by deficient activity of alpha-galactosidase A (alpha-Gal A) resulting in the storage of glycosphingolipids, especially globotriaosylceramide (Gb3), in cells throughout the body, causing life-threatening renal, cardiac, and cerebrovascular complications in hemizygous males and some heterozygous females. Disease manifestations in heterozygotes are being recognized increasingly, but quantitative prospective data on their extent and severity are limited. Prospective clinical and laboratory assessments were performed in a 7-day study of 61 women with signs and symptoms of Fabry disease. Analyses included medical history and physical, neurologic, cardiac, and ophthalmologic assessments; laboratory assessments; renal function tests; magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) of the head; and Fabry-related blood and urine tests, including Gb3 levels in blood and urine, skin biopsies, and DNA genotype analysis of the alpha-Gal A gene to identify causative mutations. Quality of life, pain and concomitant medication were documented using validated questionnaires and diaries. All patients had normal Gb3 levels in plasma; only 1 patient had visible storage material in the superficial dermal vascular endothelial cells. Cardiac, renal, or cerebrovascular abnormalities were documented in 52 of the 57 patients (91%) with confirmed Fabry genotypes. These included electrocardiographic abnormalities in 38 of 52 patients (73%), echocardiographic abnormalities in 8 of 57 (14%), proteinuria (>150 g protein/24-h urine) in 23 of 38 (61%), low estimated glomerular filtration rate (<90 mL/min per 1.73 m) in 24 of 57 (42%), abnormal MRI in 4 of 54 (7%), and abnormal MRA in 10 of 50 patients (20%). Angiokeratomas and corneal epitheliopathy were documented in 63% and 82% of the 57 patients, respectively. Despite the virtual absence of storage material in plasma and skin vascular endothelial cells, this population of women with Fabry disease exhibited a wide spectrum of clinical abnormalities. Useful outcome measures for assessment of specific therapies need to be developed. Studies limited to homogeneously affected subjects may be possible.
Materials Science and Engineering: B, 2005
The basic classification of smart materials and structures is reviewed briefly. The role of nonli... more The basic classification of smart materials and structures is reviewed briefly. The role of nonlinear response for achieving field-tunability of properties is described in simple terms. The observation of the two-way shape-memory effect in a solid solution of lead magnesium niobate (PMN) and lead titanate (PT) for the nominal atomic composition 65:35 is reported. Possible factors influencing the occurrence of
Journal of the European Ceramic Society, 1996
Lead magnesium niobate (PMN) has been prepared using the partial oxalate method without addition ... more Lead magnesium niobate (PMN) has been prepared using the partial oxalate method without addition of excess PbO and sintering at four different temperatures, 900, 1000, 1100 and 1200° C. Increase in the sintering temperature resulted in increased dielectric ...
Journal of the American Ceramic Society, 2005
Hot-stage transmission electron microscopy studies of lanthanum-modified lead zirconate titanate ... more Hot-stage transmission electron microscopy studies of lanthanum-modified lead zirconate titanate (Pb 1−x La x -(Zr 0.53 Ti 0.47 ) 1−x/4 O 3 (PLZT 100x/53/47) have been performed for compositions close to the morphotropic phase boundary (MPB). These studies have revealed the coexistence of relaxor and normal ferroelectric phases. Lanthanum substitution disrupts long-range ferroelectric order, resulting in short-range polar ordering. Investigations also have been performed using dielectric spectroscopy, electrically induced polarization, and strain methods. Three phases have been found for 10/53/47: a low-temperature tetragonal phase, a high-temperature cubic phase, and an intermediate-temperature pseudocubic phase that exhibits relaxor ferroelectric behavior. Induced strain studies of 10/ 53/47 show a gradual change from butterfly-shaped to slimquadratic loops with increasing temperature. In addition, the remanent strain decreases with increasing temperature, and reversible strain shows a peak at 80°C that corresponds to the appearance of intermediate phase.
Journal of the American Ceramic Society, 2005
Page 1. J. Am. Ceram. Soc., 80 [2] 47785 (1997) Compositional Studies of Lanthanum-Modified Morp... more Page 1. J. Am. Ceram. Soc., 80 [2] 47785 (1997) Compositional Studies of Lanthanum-Modified Morphotropic Phase Boundary Pb(Mg1/3Nb2/3)O3PbTiO3 Ceramics Surya M. Gupta and Dwight Viehland* Department of Materials ...
Journal of the American Ceramic Society, 2000
Page 1. Direct Imaging of Atomic Ordering in Undoped and La-Doped Pb(Mg1/3Nb2/3)O3 Zhengkui Xu, S... more Page 1. Direct Imaging of Atomic Ordering in Undoped and La-Doped Pb(Mg1/3Nb2/3)O3 Zhengkui Xu, Surya M. Gupta, and Dwight ViehlandV Department of Materials Science and Engineering, University of Illinois, Urbana, Illinois 61801 Yanfa Yan and Stephen J. Pennycook ...
Journal of Applied Physics, 1999
Alternating current field effect on the freezing temperature of relaxor ferroelectrics. [Journal ... more Alternating current field effect on the freezing temperature of relaxor ferroelectrics. [Journal of Applied Physics 85, 362 (1999)]. Eugene V. Colla, Surya M. Gupta, Dwight Viehland. Abstract. Alternating current-field effects on the ...
Journal of Applied Physics, 2000
Relaxor-like dielectric behavior, analogous to that found in lead magnesium niobate, has been ind... more Relaxor-like dielectric behavior, analogous to that found in lead magnesium niobate, has been induced in the polar dielectric barium magnesium niobate ͑BMN͒. In BMN, the dielectric constant was increased and the temperature of the maximum dielectric constant was shifted to a lower temperature with a decrease in measurement frequency with increasing A-site vacancy concentrations. The frequency dispersion of the permittivity maximum exhibited good agreement with the Arrhenius relationship. An activation energy of 0.15 eV and a preexponential factor 10 14 s Ϫ1 were determined. No frequency dispersion in the imaginary part of the permittivity was found below the temperature of the dielectric maximum. A linear polarization-electric field dependence was observed at room temperature. A polarization of 0.3 C/cm 2 was found under a field of 75 kV/cm at 25°C. Phase analysis revealed a single phase perovskite structure with a hexagonal unit cell with aϭ5.77 Å and cϭ7.08 Å. ͗110͘ selected area electron diffraction patterns revealed superlattice reflections along the ͗111͘. High resolution Z-contrast imaging was used to study the local ordering and the origin of the relaxational polarization.
Journal of Applied Physics, 1996
... Surya M. Guptaa) and Dwight Viehland Department of Materials Science and Engineering and the ... more ... Surya M. Guptaa) and Dwight Viehland Department of Materials Science and Engineering and the Materials Research Laboratory, University of Illinois at Urbana-Champaign ... Quantitative analysis using standardless energy-dispersive x-ray spectroscopy was also performed. ...
Journal of Applied Physics, 1998
Tetragonal to rhombohedral transformation in the lead zirconium titanate lead magnesium niobate-l... more Tetragonal to rhombohedral transformation in the lead zirconium titanate lead magnesium niobate-lead titanate crystalline solution. [Journal of Applied Physics 83, 407 (1998)]. Surya M. Gupta, Dwight Viehland. Abstract. Evidence ...
Spinal Cord, 2007
Study design:Case report.Setting:Temple University Children's Medical Center in USA.Objectiv... more Study design:Case report.Setting:Temple University Children's Medical Center in USA.Objectives:To report a patient whose recurrent and transient episodes of quadriplegia mimicked cervical cord neurapraxia. Cervical spine neuroimaging revealed congenital intersegmental fusion of C5 through C7 (consistent with Klippel–Feil anomaly), corresponding abnormal spinal cord signals on T2-weighted images and enhancing focal lesion opposite the C4 vertebral body. A posterior cervical decompression at
Journal of Child Neurology, 2010
The purpose of this study was to test the hypothesis that children with developmental delay witho... more The purpose of this study was to test the hypothesis that children with developmental delay without regression of unknown etiology are more likely to have intracranial incidental findings than are children with autistic spectrum disorder or children with normal development. Of ...
Solid State Sciences, 2013
ABSTRACT BiFeO3 sample prepared by rapid liquid phase sintering (RLPS) technique is found to poss... more ABSTRACT BiFeO3 sample prepared by rapid liquid phase sintering (RLPS) technique is found to posses better dielectric properties than the subsequently annealed sample. These samples also show ferromagnetism at room temperature. Detailed X-ray diffraction and Rietveld refinement of the data show that oxygen–iron–oxygen (O–Fe–O) bond angle is considerably more distorted in samples prepared by rapid liquid-phase sintering technique than in the annealed sample. In addition, synchrotron X-ray diffraction as well as high resolution transmission electron microscopy studies show higher concentration of impurity phases in the annealed samples, which is the likely reason for inferior dielectric properties. Further transmission electron microscopy results indicate that high crystalline order is not necessary for better dielectric properties. However weak ferromagnetism is observed in all these samples and appears to be the intrinsic property of samples prepared by rapid liquid phase sintering technique.
Journal of Physics and Chemistry …, 2008
Investigations have been performed on lanthanum-modified layered ferroelectric bismuth titanate f... more Investigations have been performed on lanthanum-modified layered ferroelectric bismuth titanate for composition Bi 3.25 La 0.75 Ti 3 O 12 (BLT) using impedance spectroscopy to understand the role of microstructure on the dielectric properties of this important material. A wide range of frequency and a wide range of temperature passing through the Curie point were chosen for the measurement. The frequency dependence suggested an interfacial polarization controlled Maxwell-Wagner type relaxation at low frequencies, and the impedance spectrum correlated with the mathematical fitting indicated the presence of two types of interfaces, which were attributed to the metallurgical boundaries and the twinned planes parallel to the bismuth oxide layers inherent to the crystal structure within the metallurgical grains. A careful analysis of the dielectric properties, particularly the ac-conductivity analysis revealed that the grain boundaries did also follow their own Jonscher-like relaxation, and the overall relaxation of the sample changed to a purely grain boundary-limited response at low frequency to a pure grain-limited response at higher frequencies. And overall admittance of the ceramic sample neither follow unmodified nor modified Jonscher's law rather its behaviour can be well described by series addition of Jonscher's admittance corresponding to grain boundary and grain. It was demonstrated that the frequency response of the ac conductivity was related to the microstructure exactly in the same way as any other dielectric function, like the impedance or dielectric constant, a fact, which is not much emphasized in the open literature. r
World journal of clinical pediatrics, Jan 8, 2015
Complicated migraine encompasses several individual clinical syndromes of migraine. Such a syndro... more Complicated migraine encompasses several individual clinical syndromes of migraine. Such a syndrome in children frequently presents with various neurological symptoms in the Emergency Department. An acute presentation in the absence of headache presents a diagnostic challenge. A delay in diagnosis and treatment may have medicolegal implication. To date, there are no reports of a common clinical profile proposed in making a clinical diagnosis for the complicated migraine. In this clinical review, we propose and describe: (1) A common clinical profile in aid to clinical diagnosis for spectrum of complicated migraine; (2) How it can be used in differentiating complicated migraine from migraine without aura, migraine with aura, and seizure; (3) We discuss the status of complicated migraine in the International Headache Society classification 2013; and (4) In addition, a common treatment strategy for the spectrum of migraine has been described. To diagnose complicated migraine clinically...
Medicine, 2005
Fabry disease is a rare X-linked lysosomal storage disorder caused by deficient activity of alpha... more Fabry disease is a rare X-linked lysosomal storage disorder caused by deficient activity of alpha-galactosidase A (alpha-Gal A) resulting in the storage of glycosphingolipids, especially globotriaosylceramide (Gb3), in cells throughout the body, causing life-threatening renal, cardiac, and cerebrovascular complications in hemizygous males and some heterozygous females. Disease manifestations in heterozygotes are being recognized increasingly, but quantitative prospective data on their extent and severity are limited. Prospective clinical and laboratory assessments were performed in a 7-day study of 61 women with signs and symptoms of Fabry disease. Analyses included medical history and physical, neurologic, cardiac, and ophthalmologic assessments; laboratory assessments; renal function tests; magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) of the head; and Fabry-related blood and urine tests, including Gb3 levels in blood and urine, skin biopsies, and DNA g...
Solid State Communications, 2004
... Shape-memory effect in PMN-PT(65/35) ceramic. Pragya Pandit, Surya M. Gupta Corresponding Aut... more ... Shape-memory effect in PMN-PT(65/35) ceramic. Pragya Pandit, Surya M. Gupta Corresponding Author Contact Information , E-mail The Corresponding Author and Vinod K. Wadhawan. Laser Materials Division, Centre for Advanced Technology, Indore 245013, India. ...
Pramana, 2008
AC impedance spectroscopy technique has been used to study electrical properties of Bi 3.25 La 0.... more AC impedance spectroscopy technique has been used to study electrical properties of Bi 3.25 La 0.75 Ti 3 O 12 (BLT) ceramic. Complex impedance plots were fitted with three depressed semicircles, which are attributed to crystalline layer, plate boundary and grain boundary and all three were found to comprise of universal capacitance nature [C = C0w n−1 ]. Grain boundary resistance and capacitance evaluated from complex impedance plots have larger values than that of plate boundary and crystalline layer. The activation energies (E a ) for DC-conductance in grain boundary, plate boundary and crystalline layer are 0.68 eV, 0.89 eV and 0.89 eV, respectively. Relaxation activation energies calculated from impedance plots showed similar values, 0.81 eV and 0.80 eV for crystalline layer and plate boundary, respectively. These activation energy values are found to be consistent with the E a value of oxygen vacancies in perovskite materials. A mechanism is offered to explain the generation of oxygen vacancies in BLT ceramic and its role in temperature dependence of DC-conductance study.
Neurology, 2002
Mucolipidosis type IV (MLIV) is an autosomal recessive disease caused by mutations in the MCOLN1 ... more Mucolipidosis type IV (MLIV) is an autosomal recessive disease caused by mutations in the MCOLN1 gene that codes for mucolipin, a member of the transient receptor potential (TRP) gene family. To comprehensively characterize the clinical and genetic abnormalities of MLIV. Twenty-eight patients with MLIV, aged 2 to 25 years, were studied. Ten returned for follow-up every 1 to 2 years for up to 5 years. Standard clinical, neuroimaging, neurophysiologic, and genetic techniques were used. All patients had varying degrees of corneal clouding, with progressive optic atrophy and retinal dystrophy. Twenty-three patients had severe motor and mental impairment. Motor function deteriorated in three patients and remained stable in the rest. All had a constitutive achlorhydria with elevated plasma gastrin level, and 12 had iron deficiency or anemia. Head MRI showed consistent characteristic findings of a thin corpus callosum and remained unchanged during the follow-up period. Prominent abnormalities of speech, hand usage, and swallowing were also noted. Mutations in the MCOLN1 gene were present in all patients. Correlation of the genotype with the neurologic handicap and corpus callosum dysplasia was found. MLIV is both a developmental and a degenerative disorder. The presentation as a cerebral palsy-like encephalopathy may delay diagnosis.
Medicine, 2005
Fabry disease is a rare X-linked lysosomal storage disorder caused by deficient activity of alpha... more Fabry disease is a rare X-linked lysosomal storage disorder caused by deficient activity of alpha-galactosidase A (alpha-Gal A) resulting in the storage of glycosphingolipids, especially globotriaosylceramide (Gb3), in cells throughout the body, causing life-threatening renal, cardiac, and cerebrovascular complications in hemizygous males and some heterozygous females. Disease manifestations in heterozygotes are being recognized increasingly, but quantitative prospective data on their extent and severity are limited. Prospective clinical and laboratory assessments were performed in a 7-day study of 61 women with signs and symptoms of Fabry disease. Analyses included medical history and physical, neurologic, cardiac, and ophthalmologic assessments; laboratory assessments; renal function tests; magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) of the head; and Fabry-related blood and urine tests, including Gb3 levels in blood and urine, skin biopsies, and DNA genotype analysis of the alpha-Gal A gene to identify causative mutations. Quality of life, pain and concomitant medication were documented using validated questionnaires and diaries. All patients had normal Gb3 levels in plasma; only 1 patient had visible storage material in the superficial dermal vascular endothelial cells. Cardiac, renal, or cerebrovascular abnormalities were documented in 52 of the 57 patients (91%) with confirmed Fabry genotypes. These included electrocardiographic abnormalities in 38 of 52 patients (73%), echocardiographic abnormalities in 8 of 57 (14%), proteinuria (>150 g protein/24-h urine) in 23 of 38 (61%), low estimated glomerular filtration rate (<90 mL/min per 1.73 m) in 24 of 57 (42%), abnormal MRI in 4 of 54 (7%), and abnormal MRA in 10 of 50 patients (20%). Angiokeratomas and corneal epitheliopathy were documented in 63% and 82% of the 57 patients, respectively. Despite the virtual absence of storage material in plasma and skin vascular endothelial cells, this population of women with Fabry disease exhibited a wide spectrum of clinical abnormalities. Useful outcome measures for assessment of specific therapies need to be developed. Studies limited to homogeneously affected subjects may be possible.
Materials Science and Engineering: B, 2005
The basic classification of smart materials and structures is reviewed briefly. The role of nonli... more The basic classification of smart materials and structures is reviewed briefly. The role of nonlinear response for achieving field-tunability of properties is described in simple terms. The observation of the two-way shape-memory effect in a solid solution of lead magnesium niobate (PMN) and lead titanate (PT) for the nominal atomic composition 65:35 is reported. Possible factors influencing the occurrence of
Journal of the European Ceramic Society, 1996
Lead magnesium niobate (PMN) has been prepared using the partial oxalate method without addition ... more Lead magnesium niobate (PMN) has been prepared using the partial oxalate method without addition of excess PbO and sintering at four different temperatures, 900, 1000, 1100 and 1200° C. Increase in the sintering temperature resulted in increased dielectric ...
Journal of the American Ceramic Society, 2005
Hot-stage transmission electron microscopy studies of lanthanum-modified lead zirconate titanate ... more Hot-stage transmission electron microscopy studies of lanthanum-modified lead zirconate titanate (Pb 1−x La x -(Zr 0.53 Ti 0.47 ) 1−x/4 O 3 (PLZT 100x/53/47) have been performed for compositions close to the morphotropic phase boundary (MPB). These studies have revealed the coexistence of relaxor and normal ferroelectric phases. Lanthanum substitution disrupts long-range ferroelectric order, resulting in short-range polar ordering. Investigations also have been performed using dielectric spectroscopy, electrically induced polarization, and strain methods. Three phases have been found for 10/53/47: a low-temperature tetragonal phase, a high-temperature cubic phase, and an intermediate-temperature pseudocubic phase that exhibits relaxor ferroelectric behavior. Induced strain studies of 10/ 53/47 show a gradual change from butterfly-shaped to slimquadratic loops with increasing temperature. In addition, the remanent strain decreases with increasing temperature, and reversible strain shows a peak at 80°C that corresponds to the appearance of intermediate phase.
Journal of the American Ceramic Society, 2005
Page 1. J. Am. Ceram. Soc., 80 [2] 47785 (1997) Compositional Studies of Lanthanum-Modified Morp... more Page 1. J. Am. Ceram. Soc., 80 [2] 47785 (1997) Compositional Studies of Lanthanum-Modified Morphotropic Phase Boundary Pb(Mg1/3Nb2/3)O3PbTiO3 Ceramics Surya M. Gupta and Dwight Viehland* Department of Materials ...
Journal of the American Ceramic Society, 2000
Page 1. Direct Imaging of Atomic Ordering in Undoped and La-Doped Pb(Mg1/3Nb2/3)O3 Zhengkui Xu, S... more Page 1. Direct Imaging of Atomic Ordering in Undoped and La-Doped Pb(Mg1/3Nb2/3)O3 Zhengkui Xu, Surya M. Gupta, and Dwight ViehlandV Department of Materials Science and Engineering, University of Illinois, Urbana, Illinois 61801 Yanfa Yan and Stephen J. Pennycook ...
Journal of Applied Physics, 1999
Alternating current field effect on the freezing temperature of relaxor ferroelectrics. [Journal ... more Alternating current field effect on the freezing temperature of relaxor ferroelectrics. [Journal of Applied Physics 85, 362 (1999)]. Eugene V. Colla, Surya M. Gupta, Dwight Viehland. Abstract. Alternating current-field effects on the ...
Journal of Applied Physics, 2000
Relaxor-like dielectric behavior, analogous to that found in lead magnesium niobate, has been ind... more Relaxor-like dielectric behavior, analogous to that found in lead magnesium niobate, has been induced in the polar dielectric barium magnesium niobate ͑BMN͒. In BMN, the dielectric constant was increased and the temperature of the maximum dielectric constant was shifted to a lower temperature with a decrease in measurement frequency with increasing A-site vacancy concentrations. The frequency dispersion of the permittivity maximum exhibited good agreement with the Arrhenius relationship. An activation energy of 0.15 eV and a preexponential factor 10 14 s Ϫ1 were determined. No frequency dispersion in the imaginary part of the permittivity was found below the temperature of the dielectric maximum. A linear polarization-electric field dependence was observed at room temperature. A polarization of 0.3 C/cm 2 was found under a field of 75 kV/cm at 25°C. Phase analysis revealed a single phase perovskite structure with a hexagonal unit cell with aϭ5.77 Å and cϭ7.08 Å. ͗110͘ selected area electron diffraction patterns revealed superlattice reflections along the ͗111͘. High resolution Z-contrast imaging was used to study the local ordering and the origin of the relaxational polarization.
Journal of Applied Physics, 1996
... Surya M. Guptaa) and Dwight Viehland Department of Materials Science and Engineering and the ... more ... Surya M. Guptaa) and Dwight Viehland Department of Materials Science and Engineering and the Materials Research Laboratory, University of Illinois at Urbana-Champaign ... Quantitative analysis using standardless energy-dispersive x-ray spectroscopy was also performed. ...
Journal of Applied Physics, 1998
Tetragonal to rhombohedral transformation in the lead zirconium titanate lead magnesium niobate-l... more Tetragonal to rhombohedral transformation in the lead zirconium titanate lead magnesium niobate-lead titanate crystalline solution. [Journal of Applied Physics 83, 407 (1998)]. Surya M. Gupta, Dwight Viehland. Abstract. Evidence ...
Spinal Cord, 2007
Study design:Case report.Setting:Temple University Children's Medical Center in USA.Objectiv... more Study design:Case report.Setting:Temple University Children's Medical Center in USA.Objectives:To report a patient whose recurrent and transient episodes of quadriplegia mimicked cervical cord neurapraxia. Cervical spine neuroimaging revealed congenital intersegmental fusion of C5 through C7 (consistent with Klippel–Feil anomaly), corresponding abnormal spinal cord signals on T2-weighted images and enhancing focal lesion opposite the C4 vertebral body. A posterior cervical decompression at
Journal of Child Neurology, 2010
The purpose of this study was to test the hypothesis that children with developmental delay witho... more The purpose of this study was to test the hypothesis that children with developmental delay without regression of unknown etiology are more likely to have intracranial incidental findings than are children with autistic spectrum disorder or children with normal development. Of ...