Devendra Tiwari | The University of Texas Health Science Center at Houston (original) (raw)

Papers by Devendra Tiwari

To get relief from tired feet, massage them, use rolling stick, soak them, cleanse and get refres... more To get relief from tired feet, massage them, use rolling stick, soak them, cleanse and get refreshed feet.

2016 Ninth International Conference on Contemporary Computing (IC3), 2016

Sustainable Energy Fuels, 2017

ACS applied materials & interfaces, Jan 29, 2016

A single molecular precursor solution is described for the deposition of CuIn(S,Se)2 (CIS) film o... more A single molecular precursor solution is described for the deposition of CuIn(S,Se)2 (CIS) film onto Mo coated glass substrates by spin coating followed by annealing in Se atmosphere. Characterization of the films by X-ray diffraction, Raman spectroscopy and scanning electron microscopy demonstrates the formation of a highly homogenous and compact 1.1 m thick CIS layer, with a MoSe2 under-layer. Atomic force microscopy reveals the presence of spherical grains between 400-450 nm, featuring surface corrugation in the range of 30 nm. Film composition is found to be in close agreement with that of the precursor solution. Diffuse reflectance spectroscopy shows a direct band gap (Eg) of 1.36 eV. Intensity and temperature dependence photoluminescence spectra show characteristic features associated with a donor-acceptor pair recombination mechanism, featuring activation energy of 34 meV. Over 85 solar cell devices with the configuration Mo/CIS/CdS/i-ZnO/Al:ZnO/Ni-Al and an total area of 0....

Cultura International Journal of Philosophy of Culture and Axiology, 2016

2016 IEEE Students' Conference on Electrical, Electronics and Computer Science (SCEECS), 2016

The Journal of Physical Chemistry C, 2016

The user has requested enhancement of the downloaded file. All in-text references underlined in b... more The user has requested enhancement of the downloaded file. All in-text references underlined in blue are added to the original document and are linked to publications on ResearchGate, letting you access and read them immediately.

Chemistry of Materials, 2016

Polish Journal of Microbiology Polskie Towarzystwo Mikrobiologow the Polish Society of Microbiologists, Feb 1, 2004

Alkaline phosphatase (phosphomonoesterase i.e. PMEase) activity in heterocystous cyanobacteria An... more Alkaline phosphatase (phosphomonoesterase i.e. PMEase) activity in heterocystous cyanobacteria Anabaena flos-aquae, Nostoc calcicola, Calothrix brevissima, Scytonema javanicum and Hapalosiphon intricatus is known to be temperature and pH dependent. Maximum level of enzyme activity was recorded at either 35 degrees C or 37.5 degrees C. Also, the cell bound phosphomonoesterase enzyme was shown to exhibit pH optima of 10.0 or 10.2. A thermo-tolerant (tr) mutant isolated after MNNG (N-methyl-N'-nitro-N-nitrosoguanidine) mutagenesis in Calothrix brevissima exhibited 10 degrees C higher temperature optima and comparatively high pH optima (pH 10.4) for phosphomonoesterase enzyme. The mutant grew with a maximum growth rate (k) at 50 degrees C. Activation energy (Ea) for cyanobacterial strains was in a narrow range between 45 to 52 kJ mol(-1). A little variation in temperature and pH optima was also observed in phosphomonoesterase activity of Calothrix brevissima and its thermo-tolerant mutant while utilizing various organic phosphates as substrate what indicated the substrate dependence temperature and pH optima. Cyanobacterial strains grown at their respective temperature and pH optima differentiated spores less frequently though, coupled with early initiation of spore.

Environmental Pollution, 1994

The impact of graded concentrations (5, 10, 15 and 20 mg dm 3) of acid mordant Metomega Chronw Or... more The impact of graded concentrations (5, 10, 15 and 20 mg dm 3) of acid mordant Metomega Chronw Orange GL, a common d.ve used in woollen, carpet and textile industries, was studied on protein and pigment content and photosynthetic oxygen evolution in a diazotrophie ~Tanobacterium Nostoc rnuscorum. The lower concentration of 5 mg dm 3 showed a negligible effect on protein and pigment content and photoo,nthetie oxygen evolution, whereas at higher concentrations a drastic decrease in the above parameters was observed. The highest coneentration of 20 mg dm 3 resulted in a decrease of protein, chlorophyll a, phycocyanin and carotenoid eontent by 72, 76, 54 and 17% of the control, respeetively. Photoo,nthetic oxygen evolution also decreased by 92% of the control at this concentration qfl the dye.

Lecture Notes in Computer Science, 2015

A survey of Himalayan Thar was carried out in Langtang valley in response to the lacking of scien... more A survey of Himalayan Thar was carried out in Langtang valley in response to the lacking of scientific information of its population status and distribution in the area. The study was carried out from Ghodatabela to Langsisa Kharka during April to June of 2003/04/2005. The area was divided into 5 survey blocks measuring 5sqkm each and study was conducted through blocks. Observed herds and individual animals were repeatedly counted and recorded. A total of 218 individuals of different age and sex Himalayan Thar were recorded during the study in 8 different herds. Three types of herds were recognized; Adult maleadult female-young (37.5%), Adult female-young (37.5%) and All adult-male (25%). Survey revealed that 50% of Thar herds were observed in 4200-4900m (Fourth block) and least (12%) were in 3700-4000m (First block), animals were not located in 3850-4200m (Third, Fifth block). Stratified random sampling was done to analyze the vegetation in their habitat and identified 26 potential plant species. The encroachment of their habitat is severe by the excessive livestock grazing and utilization for cowshed. Noticeable disturbance felt due to frequent poaching and tourist flow. The conservation of this species seems vital as it is prime prey species of Snow leopard in LNP.

Journal of Materials Science: Materials in Electronics, 2014

ABSTRACT Cu2SnS3 (CTS) is a simple and potential material for low-cost thin film solar cells. The... more ABSTRACT Cu2SnS3 (CTS) is a simple and potential material for low-cost thin film solar cells. The present work incorporates the study of changes in structural and optical properties of layer-by-layer solution deposited CTS films with annealing. Raman spectroscopy is used to ascertain structural modification upon annealing. Increase in annealing temperature leads to a structural transition from tetragonal to cubic phase. Effect of annealing on optical properties of the films is evaluated in the wavelength range of 400-2,400 nm. It is proposed that layer-by-layer growth method fundamentally defines the optical behaviour of these films. Optical constants and parameters such as refractive indices, dielectric constants and electron energy loss function are calculated from transmittance and reflectance data. The refractive indices, n and k are determined to be in ranges of 1.8-2.2 and 0.18-1.2, respectively. The real and imaginary dielectric constants vary from 1.5 to 4.6 and 0.7 to 5, respectively. Dispersion of refractive index is analyzed using two different theoretical models of Wemple-diDomenico and Spitzer-Fan.

Applied Physics A, 2014

ABSTRACT A simple and rapid process for the synthesis of Cu2SnS3 (CTS) nanoparticles by microwave... more ABSTRACT A simple and rapid process for the synthesis of Cu2SnS3 (CTS) nanoparticles by microwave heating of metal-organic precursor solution is described. X-ray diffraction and Raman spectroscopy confirm the formation of tetragonal CTS. X-ray photoelectron spectroscopy indicates the presence of Cu, Sn, S in + 1, + 4, -2 oxidation states, respectively. Transmission electron microscopy divulges the formation of crystalline tetragonal CTS nanoparticles with sizes ranging 2-25 nm. Diffuse reflectance spectroscopy in the 300-2,400 nm wavelength range suggests a band gap of 1.1 eV. Pellets of CTS nanoparticles show p-type conduction and the carrier transport in temperature range of 250-425 K is thermally activated with activation energy of 0.16 eV. Thin film solar cell (TFSC) with architecture: graphite/Cu2SnS3/ZnO/ITO/SLG is fabricated by drop-casting dispersion of CTS nanoparticles which delivered a power conversion efficiency of 0.135 % with open circuit voltage, short circuit current and fill factor of 220 mV, 1.54 mA cm(-2), 0.40, respectively.

The Journal of Physical Chemistry C, 2015

ABSTRACT The present work delivers the first assessment of BiFeO3 (BFO) thin films as an intermed... more ABSTRACT The present work delivers the first assessment of BiFeO3 (BFO) thin films as an intermediate band gap absorber for sustainable photovoltaic devices. Films are deposited from a metal-organic precursor complex solution followed by annealing in air at 673 K for 2 hrs. X-ray diffraction, complemented by quantitative analysis indicated formation of pure BFO with rhombohedral structure (R3C). Atomic force microscopy suggests deposition of compact and smooth films with spherical particles of sizes ~ 150 nm. A direct band gap of 2.2 eV is ascertained from UV-Visible-NIR spectroscopy. Mechanistic aspects of the BFO formation are discussed based on thermograveminetric analysis, differential scanning calorimetry and infrared spectroscopy of the precursor complex. A proof-of-concept BFO/ZnO heterojunction based solar cell fabricated by solution processing delivered a photo-conversion efficiency of 3.98 % with open-circuit voltage (VOC), short-circuit current density and fill factor of 642 mV, 12.47 mA/cm2 and 50.4%, respectively. The device exhibits a maximum external quantum efficiency of nearly 70 %. These parameters are among the highest values reported for all oxide PV. Analysis of the VOC, series resistance and conversion efficiency as a function of temperature revealed valuable information about recombination processes.

Polish journal of microbiology / Polskie Towarzystwo Mikrobiologów = The Polish Society of Microbiologists, 2004

Alkaline phosphatase (phosphomonoesterase i.e. PMEase) activity in heterocystous cyanobacteria An... more Alkaline phosphatase (phosphomonoesterase i.e. PMEase) activity in heterocystous cyanobacteria Anabaena flos-aquae, Nostoc calcicola, Calothrix brevissima, Scytonema javanicum and Hapalosiphon intricatus is known to be temperature and pH dependent. Maximum level of enzyme activity was recorded at either 35 degrees C or 37.5 degrees C. Also, the cell bound phosphomonoesterase enzyme was shown to exhibit pH optima of 10.0 or 10.2. A thermo-tolerant (tr) mutant isolated after MNNG (N-methyl-N'-nitro-N-nitrosoguanidine) mutagenesis in Calothrix brevissima exhibited 10 degrees C higher temperature optima and comparatively high pH optima (pH 10.4) for phosphomonoesterase enzyme. The mutant grew with a maximum growth rate (k) at 50 degrees C. Activation energy (Ea) for cyanobacterial strains was in a narrow range between 45 to 52 kJ mol(-1). A little variation in temperature and pH optima was also observed in phosphomonoesterase activity of Calothrix brevissima and its thermo-tolerant ...

ABSTRACT The properties of pure Cu2SnS3 thin films synthesized by direct liquid coating method ha... more ABSTRACT The properties of pure Cu2SnS3 thin films synthesized by direct liquid coating method have been studied for application in TFSCs. The films have band gap of 1.12 eV and an absorption coefficient of ~105 cm-1. They are p-type with electrical conductivity of 0.5 S/cm and show photoconductivity. TFSCs made of these p-CTS films and n-CdS have been analyzed. The maximum efficiency of CTS solar cells is 33% with VOC and ISC of 0.75 V and 40 mA/cm.

International Journal of Computer Applications, 2010

To get relief from tired feet, massage them, use rolling stick, soak them, cleanse and get refres... more To get relief from tired feet, massage them, use rolling stick, soak them, cleanse and get refreshed feet.

2016 Ninth International Conference on Contemporary Computing (IC3), 2016

Sustainable Energy Fuels, 2017

ACS applied materials & interfaces, Jan 29, 2016

A single molecular precursor solution is described for the deposition of CuIn(S,Se)2 (CIS) film o... more A single molecular precursor solution is described for the deposition of CuIn(S,Se)2 (CIS) film onto Mo coated glass substrates by spin coating followed by annealing in Se atmosphere. Characterization of the films by X-ray diffraction, Raman spectroscopy and scanning electron microscopy demonstrates the formation of a highly homogenous and compact 1.1 m thick CIS layer, with a MoSe2 under-layer. Atomic force microscopy reveals the presence of spherical grains between 400-450 nm, featuring surface corrugation in the range of 30 nm. Film composition is found to be in close agreement with that of the precursor solution. Diffuse reflectance spectroscopy shows a direct band gap (Eg) of 1.36 eV. Intensity and temperature dependence photoluminescence spectra show characteristic features associated with a donor-acceptor pair recombination mechanism, featuring activation energy of 34 meV. Over 85 solar cell devices with the configuration Mo/CIS/CdS/i-ZnO/Al:ZnO/Ni-Al and an total area of 0....

Cultura International Journal of Philosophy of Culture and Axiology, 2016

2016 IEEE Students' Conference on Electrical, Electronics and Computer Science (SCEECS), 2016

The Journal of Physical Chemistry C, 2016

The user has requested enhancement of the downloaded file. All in-text references underlined in b... more The user has requested enhancement of the downloaded file. All in-text references underlined in blue are added to the original document and are linked to publications on ResearchGate, letting you access and read them immediately.

Chemistry of Materials, 2016

Polish Journal of Microbiology Polskie Towarzystwo Mikrobiologow the Polish Society of Microbiologists, Feb 1, 2004

Alkaline phosphatase (phosphomonoesterase i.e. PMEase) activity in heterocystous cyanobacteria An... more Alkaline phosphatase (phosphomonoesterase i.e. PMEase) activity in heterocystous cyanobacteria Anabaena flos-aquae, Nostoc calcicola, Calothrix brevissima, Scytonema javanicum and Hapalosiphon intricatus is known to be temperature and pH dependent. Maximum level of enzyme activity was recorded at either 35 degrees C or 37.5 degrees C. Also, the cell bound phosphomonoesterase enzyme was shown to exhibit pH optima of 10.0 or 10.2. A thermo-tolerant (tr) mutant isolated after MNNG (N-methyl-N'-nitro-N-nitrosoguanidine) mutagenesis in Calothrix brevissima exhibited 10 degrees C higher temperature optima and comparatively high pH optima (pH 10.4) for phosphomonoesterase enzyme. The mutant grew with a maximum growth rate (k) at 50 degrees C. Activation energy (Ea) for cyanobacterial strains was in a narrow range between 45 to 52 kJ mol(-1). A little variation in temperature and pH optima was also observed in phosphomonoesterase activity of Calothrix brevissima and its thermo-tolerant mutant while utilizing various organic phosphates as substrate what indicated the substrate dependence temperature and pH optima. Cyanobacterial strains grown at their respective temperature and pH optima differentiated spores less frequently though, coupled with early initiation of spore.

Environmental Pollution, 1994

The impact of graded concentrations (5, 10, 15 and 20 mg dm 3) of acid mordant Metomega Chronw Or... more The impact of graded concentrations (5, 10, 15 and 20 mg dm 3) of acid mordant Metomega Chronw Orange GL, a common d.ve used in woollen, carpet and textile industries, was studied on protein and pigment content and photosynthetic oxygen evolution in a diazotrophie ~Tanobacterium Nostoc rnuscorum. The lower concentration of 5 mg dm 3 showed a negligible effect on protein and pigment content and photoo,nthetie oxygen evolution, whereas at higher concentrations a drastic decrease in the above parameters was observed. The highest coneentration of 20 mg dm 3 resulted in a decrease of protein, chlorophyll a, phycocyanin and carotenoid eontent by 72, 76, 54 and 17% of the control, respeetively. Photoo,nthetic oxygen evolution also decreased by 92% of the control at this concentration qfl the dye.

Lecture Notes in Computer Science, 2015

A survey of Himalayan Thar was carried out in Langtang valley in response to the lacking of scien... more A survey of Himalayan Thar was carried out in Langtang valley in response to the lacking of scientific information of its population status and distribution in the area. The study was carried out from Ghodatabela to Langsisa Kharka during April to June of 2003/04/2005. The area was divided into 5 survey blocks measuring 5sqkm each and study was conducted through blocks. Observed herds and individual animals were repeatedly counted and recorded. A total of 218 individuals of different age and sex Himalayan Thar were recorded during the study in 8 different herds. Three types of herds were recognized; Adult maleadult female-young (37.5%), Adult female-young (37.5%) and All adult-male (25%). Survey revealed that 50% of Thar herds were observed in 4200-4900m (Fourth block) and least (12%) were in 3700-4000m (First block), animals were not located in 3850-4200m (Third, Fifth block). Stratified random sampling was done to analyze the vegetation in their habitat and identified 26 potential plant species. The encroachment of their habitat is severe by the excessive livestock grazing and utilization for cowshed. Noticeable disturbance felt due to frequent poaching and tourist flow. The conservation of this species seems vital as it is prime prey species of Snow leopard in LNP.

Journal of Materials Science: Materials in Electronics, 2014

ABSTRACT Cu2SnS3 (CTS) is a simple and potential material for low-cost thin film solar cells. The... more ABSTRACT Cu2SnS3 (CTS) is a simple and potential material for low-cost thin film solar cells. The present work incorporates the study of changes in structural and optical properties of layer-by-layer solution deposited CTS films with annealing. Raman spectroscopy is used to ascertain structural modification upon annealing. Increase in annealing temperature leads to a structural transition from tetragonal to cubic phase. Effect of annealing on optical properties of the films is evaluated in the wavelength range of 400-2,400 nm. It is proposed that layer-by-layer growth method fundamentally defines the optical behaviour of these films. Optical constants and parameters such as refractive indices, dielectric constants and electron energy loss function are calculated from transmittance and reflectance data. The refractive indices, n and k are determined to be in ranges of 1.8-2.2 and 0.18-1.2, respectively. The real and imaginary dielectric constants vary from 1.5 to 4.6 and 0.7 to 5, respectively. Dispersion of refractive index is analyzed using two different theoretical models of Wemple-diDomenico and Spitzer-Fan.

Applied Physics A, 2014

ABSTRACT A simple and rapid process for the synthesis of Cu2SnS3 (CTS) nanoparticles by microwave... more ABSTRACT A simple and rapid process for the synthesis of Cu2SnS3 (CTS) nanoparticles by microwave heating of metal-organic precursor solution is described. X-ray diffraction and Raman spectroscopy confirm the formation of tetragonal CTS. X-ray photoelectron spectroscopy indicates the presence of Cu, Sn, S in + 1, + 4, -2 oxidation states, respectively. Transmission electron microscopy divulges the formation of crystalline tetragonal CTS nanoparticles with sizes ranging 2-25 nm. Diffuse reflectance spectroscopy in the 300-2,400 nm wavelength range suggests a band gap of 1.1 eV. Pellets of CTS nanoparticles show p-type conduction and the carrier transport in temperature range of 250-425 K is thermally activated with activation energy of 0.16 eV. Thin film solar cell (TFSC) with architecture: graphite/Cu2SnS3/ZnO/ITO/SLG is fabricated by drop-casting dispersion of CTS nanoparticles which delivered a power conversion efficiency of 0.135 % with open circuit voltage, short circuit current and fill factor of 220 mV, 1.54 mA cm(-2), 0.40, respectively.

The Journal of Physical Chemistry C, 2015

ABSTRACT The present work delivers the first assessment of BiFeO3 (BFO) thin films as an intermed... more ABSTRACT The present work delivers the first assessment of BiFeO3 (BFO) thin films as an intermediate band gap absorber for sustainable photovoltaic devices. Films are deposited from a metal-organic precursor complex solution followed by annealing in air at 673 K for 2 hrs. X-ray diffraction, complemented by quantitative analysis indicated formation of pure BFO with rhombohedral structure (R3C). Atomic force microscopy suggests deposition of compact and smooth films with spherical particles of sizes ~ 150 nm. A direct band gap of 2.2 eV is ascertained from UV-Visible-NIR spectroscopy. Mechanistic aspects of the BFO formation are discussed based on thermograveminetric analysis, differential scanning calorimetry and infrared spectroscopy of the precursor complex. A proof-of-concept BFO/ZnO heterojunction based solar cell fabricated by solution processing delivered a photo-conversion efficiency of 3.98 % with open-circuit voltage (VOC), short-circuit current density and fill factor of 642 mV, 12.47 mA/cm2 and 50.4%, respectively. The device exhibits a maximum external quantum efficiency of nearly 70 %. These parameters are among the highest values reported for all oxide PV. Analysis of the VOC, series resistance and conversion efficiency as a function of temperature revealed valuable information about recombination processes.

Polish journal of microbiology / Polskie Towarzystwo Mikrobiologów = The Polish Society of Microbiologists, 2004

Alkaline phosphatase (phosphomonoesterase i.e. PMEase) activity in heterocystous cyanobacteria An... more Alkaline phosphatase (phosphomonoesterase i.e. PMEase) activity in heterocystous cyanobacteria Anabaena flos-aquae, Nostoc calcicola, Calothrix brevissima, Scytonema javanicum and Hapalosiphon intricatus is known to be temperature and pH dependent. Maximum level of enzyme activity was recorded at either 35 degrees C or 37.5 degrees C. Also, the cell bound phosphomonoesterase enzyme was shown to exhibit pH optima of 10.0 or 10.2. A thermo-tolerant (tr) mutant isolated after MNNG (N-methyl-N'-nitro-N-nitrosoguanidine) mutagenesis in Calothrix brevissima exhibited 10 degrees C higher temperature optima and comparatively high pH optima (pH 10.4) for phosphomonoesterase enzyme. The mutant grew with a maximum growth rate (k) at 50 degrees C. Activation energy (Ea) for cyanobacterial strains was in a narrow range between 45 to 52 kJ mol(-1). A little variation in temperature and pH optima was also observed in phosphomonoesterase activity of Calothrix brevissima and its thermo-tolerant ...

ABSTRACT The properties of pure Cu2SnS3 thin films synthesized by direct liquid coating method ha... more ABSTRACT The properties of pure Cu2SnS3 thin films synthesized by direct liquid coating method have been studied for application in TFSCs. The films have band gap of 1.12 eV and an absorption coefficient of ~105 cm-1. They are p-type with electrical conductivity of 0.5 S/cm and show photoconductivity. TFSCs made of these p-CTS films and n-CdS have been analyzed. The maximum efficiency of CTS solar cells is 33% with VOC and ISC of 0.75 V and 40 mA/cm.

International Journal of Computer Applications, 2010

Santamedical Infrared thermometer use without body contact.