Photoluminescence, thermoluminescence and evaluation of some parameters of Dy³⁺ activated Sr₅(PO₄)₃F phosphor synthesized by sol-gel method

Gupta, K.K.,Kadam, R.M.,Dhoble, N.S.,Lochab, S.P.,Singh, V.,Dhoble, S.J. Elsevier Sequoia 2016 JOURNAL OF ALLOYS AND COMPOUNDS Vol.688 No.2

In this study, we have synthesized Dy<SUP>3+</SUP> activated Sr<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>F (S-FAP) phosphors by sol-gel synthesis method. The synthesized phosphors were characterized by X-ray diffraction pattern (XRD), scanning electron microscopic (SEM), photoluminescence (PL) and thermoluminescence (TL) for structural, morphological and luminescent properties. Dy<SUP>3+</SUP> activated Sr<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>F phosphor shows its characteristic PL emission at 481 nm and 574 nm due to <SUP>4</SUP>F<SUB>9/2</SUB> → <SUP>6</SUP>H<SUB>15/2</SUB> and <SUP>4</SUP>F<SUB>9/2</SUB> → <SUP>6</SUP>H<SUB>13/2</SUB> transitions, respectively. TL characteristics of Dy<SUP>3+</SUP> doped Sr<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>F phosphors were taken after irradiation by <SUP>60</SUP>Co gamma exposure. Two separate TL peaks at 126 <SUP>o</SUP>C and 279 <SUP>o</SUP>C were observed in case of Dy<SUP>3+</SUP> doped phosphor. Sr<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>F:Dy<SUP>3+</SUP> phosphor was irradiated within a wide range of exposure of 50 Gy to 7 kGy doses. Linearity was found up to 2 kGy and thereafter TL response saturates. Fading study was also carried out over the duration of six weeks for Sr<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>F phosphor. Trapping parameters were calculated using Chen's peak shape method, initial rise method and various heating rate method. Glow curve is deconvoluted using computerized glow curve deconvolution program. TL sensitivity of Sr<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>F:Dy<SUP>3+</SUP> phosphor is found to be less by a factor of 2.08 than commercially used CaSO<SUB>4</SUB>:Dy phosphor. In order to identify the defect centers formed upon γ-ray irradiation in Sr<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>F:Dy<SUP>3+</SUP> phosphor, EPR measurements were carried out on un-irradiated and irradiated phosphors.

IMPACT BEHAVIOR MODELING OF MOTORCYCLE FRONT WHEEL-TIRE ASSEMBLY

K. S. TAN,S. V. WONG,R. S. RADIN UMAR,N. K. GUPTA,A. M. S. HAMOUDA 한국자동차공학회 2009 International journal of automotive technology Vol.10 No.3

Experiments were conducted to investigate the influence of certain parameters that affect the impact response of the motorcycle front wheel-tire assembly under various impact conditions. Impact tests were conducted according to 2V 5–1 fractional factorial design using a pendulum impact test apparatus with impact speed, impact mass, tire inflation pressure level, striker geometry, and impact location as design factors. Significant factors influencing the response of the wheel-tire assembly were identified. Coefficients for each factor were also determined, and empirical models were then developed for each response. An analysis indicates that the developed models fit well within the experimental ranges of the respective factors. However, for several interaction effects, the models become unrealistic, whereby they give certain deformation values when approaching zero impact mass and/or zero impact velocity. This is not consistent with the mechanics of the physical world, as there should not be any significant deformation when delivered impact energy is small enough. Efforts have been made in developing better models to resolve the inconsistency and to include a wider range, especially considering the case of the lower limit of experimental factors, which are an impact mass of 51.18 kg and/or an impact velocity of 3 m s−1 (10.8 km/h) down to zero. The minimum amount of impact energy required to produce the onset of observable deformation on the wheel was incorporated in the development of new models. Finally, the present models have been developed not only to cover the lower regions but also to range up to the upper limits of the factors, which are an impact mass of 101.33 kg and an impact velocity of 6 m s−1 (21.6 km/h). Experiments were conducted to investigate the influence of certain parameters that affect the impact response of the motorcycle front wheel-tire assembly under various impact conditions. Impact tests were conducted according to 2V 5–1 fractional factorial design using a pendulum impact test apparatus with impact speed, impact mass, tire inflation pressure level, striker geometry, and impact location as design factors. Significant factors influencing the response of the wheel-tire assembly were identified. Coefficients for each factor were also determined, and empirical models were then developed for each response. An analysis indicates that the developed models fit well within the experimental ranges of the respective factors. However, for several interaction effects, the models become unrealistic, whereby they give certain deformation values when approaching zero impact mass and/or zero impact velocity. This is not consistent with the mechanics of the physical world, as there should not be any significant deformation when delivered impact energy is small enough. Efforts have been made in developing better models to resolve the inconsistency and to include a wider range, especially considering the case of the lower limit of experimental factors, which are an impact mass of 51.18 kg and/or an impact velocity of 3 m s−1 (10.8 km/h) down to zero. The minimum amount of impact energy required to produce the onset of observable deformation on the wheel was incorporated in the development of new models. Finally, the present models have been developed not only to cover the lower regions but also to range up to the upper limits of the factors, which are an impact mass of 101.33 kg and an impact velocity of 6 m s−1 (21.6 km/h).

ACCELERATING WAVES IN POLAR CORONAL HOLES AS SEEN BY EIS AND SUMER

Gupta, G. R.,Banerjee, D.,Teriaca, L.,Imada, S.,Solanki, S. IOP Publishing 2010 The Astrophysical journal Vol.718 No.1

Antiarthritic action of polar fraction from Sida rhombifolia aerial parts

Gupta, S.R.,Nirmal, S.A.,Patil, R.Y. Kyung Hee Oriental Medicine Research Center 2009 Oriental pharmacy and experimental medicine Vol.9 No.4

Aerial parts of Sida rhombifolia Linn. (Malvaceae) were extracted successively using various solvents and screened for various parameters of antiarthritic activity such as adjuvant-induced arthritis, motor performance, and histopathological study. The ethanol and the aqueous extracts showed potent activity; further these extracts were fractionated by using column chromatography. The fraction ET1 isolated from ethanol extract showed the most potent antiarthritic activity.

Interactions of methylated $\beta$-cyclodextrin and hydrophobically modified alkali-soluble emulsion (HASE) polymers: a rheological study

Gupta, R.K.,Tam, K.C.,Ong, S.H.,Jenkins, R.D. The Korean Society of Rheology 2000 Korea-Australia rheology journal Vol.12 No.2

The interactions between methylated $\beta$-cyclodextrin (CD) and hydrophobically modified alkali-soluble associative polymers (HASE) were examined by a rheological technique. The effect of "capping" of hydrophobes by methylated $\beta$-cyclodextrin on the viscosity and modulus was evaluated. Model HASE polymers with $C_1$to $C_{20}$ alkyl hydrophobic groups ethoxylated with~10 moles of ethylene-oxide (EO 10) and at concentrations up to 3 wt% were examined. With the addition of methylated $\beta$-CD, the steady shear viscosity profiles shift from a Newtonian profile to one that display a shear-thinning characteristic. Significant "capping" of the hydrophobes occurs for HASE polymers with $C_{l2}$, $C_{16}$ and $C_{20}$ hydrophobes as reflected by the large reduction in the viscosity. However, the steady shear viscosity remains constant when the concentration of $\beta$-CD exceeds 1 wt%, suggesting that $\beta$-CD is not able to fully encapsulate the hydrophobes of the HASE polymer. The temperature variation plots indicate that the activation energy of the HASE-EO10-$C_{20}$ system and $\beta$-CD is dependent on the magnitude of the applied shear stress. These results further reinforce the hypothesis that $\beta$-CD is not able to completely remove all the hydrophobic associations.phobic associations.

Preparation and characterization of highly conducting and transparent Al doped CdO thin films by pulsed laser deposition

R.K. Gupta,K. Ghosh,R. Patel,S.R. Mishra,P.K. Kahol 한국물리학회 2009 Current Applied Physics Vol.9 No.3

Highly conducting and transparent aluminum doped CdO thin films were deposited using pulsed laser deposition technique. The effect of growth temperature on structural, electrical, and optical properties was studied. It is observed that the film orientation changes from preferred (111) plane to (200) plane with increase in growth temperature. The electrical resistivity of the films was found to increase with increase in growth temperature. The low resistivity of 4.3 × 10-5 Ωcm and high transparency (~85%) was obtained for the film grown at 150 ℃. The band gap of the films varies from 2.74 eV to 2.84 eV.

CYTOGENETIC EFFECTS OF ORGANOPHOSPHATE PESTICIDES ON GOAT LYMPHOCYTES IN CULTURE

Gupta, S.C.,Sahal, R.,Gupta, N. Asian Australasian Association of Animal Productio 1996 Animal Bioscience Vol.9 No.4

Cytogenetic effects of malathion and parathion, the organophosphorus pesticides were studied on goat lymphocytes in culture. The mitotic indices (% of blast cells + cells at metaphase) of goat lymphocytes showed corresponding decrease with the increase in dose of pesticides. Malathion had significant effect only at $150{\mu}g/ml$ or higher dosages while, parathion caused antimitotic effects even at the lowest dose ($5{\mu}g/ml$) tested. The clastogenic effects of malathion were significant ($p{\leq}0.05$) at $100{\mu}g/ml$. In higher doses, the effects were highly significant ($p{\leq}0.01$). The frequency of metaphase plates with chromosomal abnormalities were highest (22.0%) at $200{\mu}g/ml$. The incidences of chromosomal abnormalities were significant ($p{\leq}0.05$) in parathion treated series even at $5{\mu}g/ml$ dose level. At $10{\mu}g/ml$ or higher dose levels the difference between treatment groups and controls were more pronounced ($p{\leq}0.01$). Various types of chromosomal abnormalities were encountered in goat lymphocytes treated by malathion and parathion. However, the incidence of gaps, breaks, acentric fragments, dicentric chromosomes were higher than other types of structural and numerical abnormalities.

Isolation of Thermotolerant Phytase Producing Fungi and Optimisation of Phytase Production by Aspergillus niger NRF9 in Solid State Fermentation Using Response Surface Methodology

R. K. Gupta,S. S. Gangoliya,N. K. Singh 한국생물공학회 2014 Biotechnology and Bioprocess Engineering Vol.19 No.6

Phytase is an enzyme that hydrolyses phyticacid into myo-inositol and inorganic phosphate. Onehundred thirteen fungi were isolated from 58 soil samplescollected from different sites with high organic mattercontent. They were screened for phytate hydrolysing activityon phytase screening medium (PSM). Clear zones wereformed around the colonies of 72 isolates on Ca-containingPSM. Solid state fermentation was done for the selectedfungal isolates for production of the phytase enzyme. Among the isolates, NRF9 showed maximum enzymeactivity (39.2 U/gds) upon quantitative screening after5 days of incubation at 30°C. The fungus grew vigorouslyand secreted enzyme at temperatures of 30, 37, and 45°C. The maximum phytase production was obtained at 30°C;the next-best production was obtained at 37°C. The isolatewas identified and characterised as Aspergillus niger NRF9on the basis of 18S rDNA sequencing. Various processparameters were optimised using a one-variable-at-a-timeapproach’. The significant factors for phytase productionwere identified as incubation time, solid:liquid ratio andglucose concentration. These factors were further optimisedusing a Box-Behnken design. Maximum phytase production(112.1 U/gds) was observed at 5 days of incubation time,a 1:2 solid:liquid ratio and a 1% glucose concentration. Validation of these optimised variables was done in shakeflasks. Optimisation resulted in a 2.9-fold increase in phytaseproduction compared to unoptimised cultivation conditions.

Metal Insulator Gate Geometric HEMT: Novel Attributes and Design Consideration for High Speed Analog Applications

Gupta, Ritesh,Kaur, Ravneet,Aggarwal, Sandeep Kr,Gupta, Mridula,Gupta, R.S. The Institute of Electronics and Information Engin 2010 Journal of semiconductor technology and science Vol.10 No.1

Improvement in breakdown voltage ($BV_{ds}$) and speed of the device are the key issues among the researchers for enhancing the performance of HEMT. Increased speed of the device aspires for shortened gate length ($L_g$), but due to lithographic limitation, shortening $L_g$ below sub-micrometer requires the inclusion of various metal-insulator geometries like T-gate onto the conventional architecture. It has been observed that the speed of the device can be enhanced by minimizing the effect of upper gate electrode on device characteristics, whereas increase in the $BV_{ds}$ of the device can be achieved by considering the finite effect of the upper gate electrode. Further, improvement in $BV_{ds}$ can be obtained by applying field plates, especially at the drain side. The important parameters affecting $BV_{ds}$ and cut-off frequency ($f_T$) of the device are the length, thickness, position and shape of metal-insulator geometry. In this context, intensive simulation work with analytical analysis has been carried out to study the effect of variation in length, thickness and position of the insulator under the gate for various metal-insulator gate geometries like T-gate, $\Gamma$-gate, Step-gate etc., to anticipate superior device performance in conventional HEMT structure.

Analytical Model for Metal Insulator Semiconductor High Electron Mobility Transistor (MISHEMT) for its High Frequency and High Power Applications

Gupta, Ritesh,Aggarwal, Sandeep Kr,Gupta, Mridula,Gupta, R.S. The Institute of Electronics and Information Engin 2006 Journal of semiconductor technology and science Vol.6 No.3

A new analytical model has been proposed for predicting the sheet carrier density of Metal insulator Semiconductor High Electron Mobility Transistor (MISHEMT). The model takes into account the non-linear relationship between sheet carrier density and quasi Fermi energy level to consider the quantum effects and to validate it from subthreshold region to high conduction region. Then model has been formulated in such a way that it is applicable to MESFET/HEMT/MISFET with few adjustable parameters. The model can also be used to evaluate the characteristics for different gate insulator geometries like T-gate etc. The model has been extended to forecast the drain current, conductance and high frequency performance. The results so obtained from the analysis show excellent agreement with previous models and simulated results that proves the validity of our model.