Pressure leaching of metals from waste printed circuit boards using sulfuric acid

Jha, M. K.,Lee, J. c.,Kumari, A.,Choubey, P. K.,Kumar, V.,Jeong, J. Springer Verlag 2011 JOM Vol.63 No.8

Electron-Electron Interactions based Metal-Insulator Transition in Ga Doped ZnO Thin Films

R V Muniswami Naidu,A Subrahmanyam,A Verger,M K Jain,S V N Bhaskara Rao,S N Jha,D M Phase 대한금속·재료학회 2012 ELECTRONIC MATERIALS LETTERS Vol.8 No.4

We report on the charge carrier transport mechanisms of undoped and Ga doped (2 wt. % and 4 wt. %)ZnO thin films grown by pulsed dc magnetron sputtering technique. Temperature dependent resistivity measurements showed typical semiconducting behaviour for undoped ZnO thin films where as Ga doped ZnO thin films showed metallic nature at higher temperatures and insulating nature with a metal to insulator transition at lower temperatures. The observed transition temperatures are 91 K and 140 K for 2 wt. % and 4 wt. %Ga doped ZnO films respectively. The observed metal insulator transition is attributed to the electron-electron interactions at low temperatures. The variations in the transition temperatures are explained based on the disorderness induced in the system due to the doping effect. ZnO doped with 4 wt. % Ga showed the lowest resistivity of 5.7 × 10−4Ω cm with a carrier concentration of 1.2 × 1021/cm3. Undoped and doped ZnO thin films are about 90% transparent in the visible region. Blue shift is observed in the absorption edge with the effect of doping and it is explained based on B-M shift. The Fermi level measured from valance band spectroscopy showed a shift of +0.6 eV for 2 wt. % Ga doped ZnO thin film and +0.7 eV for 4 wt. %Ga doped ZnO thin film compared to the Fermi edge of undoped ZnO thin films. This ascertains the movement of Fermi level in to the conduction band with the effect of doping.

Negative regulation of signal transducer and activator of transcription-3 signalling cascade by lupeol inhibits growth and induces apoptosis in hepatocellular carcinoma cells

Siveen, K S,Nguyen, A H,Lee, J H,Li, F,Singh, S S,Kumar, A P,Low, G,Jha, S,Tergaonkar, V,Ahn, K S,Sethi, G Nature Publishing Group 2014 The British journal of cancer Vol.111 No.7

<P><B>Background:</B></P><P>Constitutive activation of signal transducer and activator of transcription signalling 3 (STAT3) has been linked with survival, proliferation and angiogenesis in a wide variety of malignancies including hepatocellular carcinoma (HCC).</P><P><B>Methods:</B></P><P>We evaluated the effect of lupeol on STAT3 signalling cascade and its regulated functional responses in HCC cells.</P><P><B>Results:</B></P><P>Lupeol suppressed constitutive activation of STAT3 phosphorylation at tyrosine 705 residue effectively in a dose- and time-dependent manner. The phosphorylation of Janus-activated kinases (JAKs) 1 and 2 and Src was also suppressed by lupeol. Pervanadate treatment reversed the downregulation of phospho-STAT3 induced by lupeol, thereby indicating the involvement of a phosphatase. Indeed, we observed that treatment with lupeol increased the protein and mRNA levels of SHP-2, and silencing of SHP-2 abolished the inhibitory effects of lupeol on STAT3 activation. Treatment with lupeol also downregulated the expression of diverse STAT3-regulated genes and decreased the binding of STAT3 to VEGF promoter. Moreover, the proliferation of various HCC cells was significantly suppressed by lupeol, being associated with substantial induction of apoptosis. Depletion of SHP-2 reversed the observed antiproliferative and pro-apoptotic effects of lupeol.</P><P><B>Conclusions:</B></P><P>Lupeol exhibited its potential anticancer effects in HCC through the downregulation of STAT3-induced pro-survival signalling cascade.</P>

Critical Appraisal of Methods for the Assessment of Environmental Flows and their Application in Two River Systems of India

Ramakar Jha,K.D. Sharma,V.P. Singh 대한토목학회 2008 KSCE JOURNAL OF CIVIL ENGINEERING Vol.12 No.3

In recent years, many hydrology-based approaches have been used to assess the environmental flows in various riversystems over the globe. However, their application has been very limited in India. Brahmani and Baitarani River basins inIndia are two important water surplus basins, in which several water resources projects are coming up shortly. There is anurgent need for the water planners and stakeholders to assess best management practices of available water resources. The present paper (i) critically evaluates the applicability of existingapproaches, (ii) provides values of environmental design flows at different locations of Brahmani and Baitarani River systems,and (iii)suggest a suitable scientific approach for the assessment of environmental flows.

Experiences with Some Toxic and Relatively Accessible Heavy Metals on theSurvival and Biomass Production of Amphora costataW. Smith

S. K. Mandal,T. Ishimaru,B. Jha,D.C. Bhatt,H.V.Joshi 한국조류학회I 2006 ALGAE Vol.21 No.4

Amphora costata W. Smith 1853 is a down thrown diatom species and also known as metal corrosive ship-fouling organism. A. costata was isolated from Alang ship breaking yard, Alang and evaluated the toxicity tolerance and growth responses of the cultures exposed to different doses of toxic and relatively accessible heavy metals, such as Fe, Mn, Cd, Co, Cu, Zn, Ni, and Pb in the constantly monitored laboratory culture conditions. The strongest toxic effect was observed on A. costata exposed to Cd even at relatively low concentrations as compared to other metals . The following trend of decreasing order of toxicity i.e. Cd>Zn>Ni>Co>Pb>Cu>Fe was observed, when they were exposed to equal concentration and expose time.

Optimization of synthesis technique and luminescent properties in Eu³⁺-activated NaCaPO₄ phosphor for solid state lighting applications

Ratnam, B.V.,Sahu, Mukesh K.,Vishwakarma, Amit K.,Jha, Kaushal,Woo, Hyun-Joo,Jang, Kiwan,Jayasimhadri, M. North-Holland 2017 Journal of luminescence Vol.185 No.-

<P><B>Abstract</B></P> <P>Europium activated NaCaPO<SUB>4</SUB> phosphor has been synthesized by various synthesis techniques such as solid-state reaction (SSR), molten salt synthesis (MSS) and sol-gel combustion (SGC) method to optimize the synthesis procedure. The comparative investigations of structural and luminescent properties have been studied to know the best synthesis method. The XRD patterns and Rietveld refinement analysis of the synthesized phosphors confirmed the single phase orthorhombic structure of NaCaPO<SUB>4</SUB>. Excitation spectra indicate the strong absorption in near ultraviolet (n-UV) region and the emission spectra exhibit strong emission band at 595nm corresponds to <SUP>5</SUP>D<SUB>0</SUB>→<SUP>7</SUP>F<SUB>1</SUB> transition under n-UV (λ<SUB>ex</SUB>=392nm) excitation. The SGC route synthesized phosphor exhibit intense emission than that of the SSR and MSS method. Therefore, the effect of dopant (Eu<SUP>3+</SUP>) concentration on the emission intensity and concentration quenching mechanism has been discussed in detail for the Eu<SUP>3+</SUP> doped NaCaPO<SUB>4</SUB> phosphor synthesized by SGC method. The CIE chromaticity coordinates have been calculated for the phosphors synthesized by SSR, MSS and SGC methods to reveal the emitting color and also to know the utility of this phosphor for white LEDs.</P>

Analysis of the light transmission through nano-apertures on plateau pyramid

S.S. Choi,O.K. Suwal,V.K. Jha,김대욱,M.J. Park 한국물리학회 2009 Current Applied Physics Vol.9 No.11

The nano-size metallic aperture array has been fabricated using conventional semiconductor fabrication techniques and focused ion beam. The micron size patterns were transferred on SOI wafer using photographic patterning process, and the plateau pyramidal structures were fabricated using wet Si etching with alkaline solution followed by thermal oxidation. In order to reveal the plateau type pyramid, the backside Si bulk etching was performed. The metallic Al thin film was deposited and the nano-apertures with the diameters ranging from 190 nm to 380 nm were fabricated using focused ion beam milling method. The skin-depth of the Al thin film at 532 nm wavelength is known to be ~10 nm. The deposited Al thin film is thick enough to become opaque. Circular types of periodic grooves were fabricated around the sub-wavelength size nano-aperture in order to examine the transmittance of the light coupled to circular periodic grooves. The far-field measurements for the optical transmittance through a sub-wavelength size nano-probe have been investigated and found to be up to 103 fold increase, compared to the output intensity of aperture without groove patterns.

Leaching of rare earth metals (REMs) from Korean monazite concentrate

Panda, R.,Kumari, A.,Jha, M.K.,Hait, J.,Kumar, V.,Rajesh Kumar, J.,Lee, J.Y. Korean Society of Industrial and Engineering Chemi 2014 Journal of industrial and engineering chemistry Vol.20 No.4

Systematic scientific studies for dephosphorization and acid leaching of Korean monazite are reported here. 50% NaOH (w/v) solubilizes 99.99% phosphate, at 170<SUP>o</SUP>C, 100g/L pulp density in 4h. Kinetics of phosphate leaching fitted well with model ''chemical reaction control,'' i.e. 1-(1-X)<SUP>½</SUP>=k<SUB>c</SUB>t, E<SUB>a</SUB>=58.04kJ/mol. Further, rare earth hydroxides (REHs) was leached using 6N HCl at 90<SUP>o</SUP>C, 60g/L pulp density for 2h to recover ~95% REMs. Leach liquor generated can be further processed using solvent extraction/ion exchange techniques. From the pure solutions, metal/salts could be obtained using evaporation, precipitation, etc.

Analysis of the light transmission through nano-apertures on plateau pyramid

Choi, S.S.,Suwal, O.K.,Jha, V.K.,Kim, D.W.,Park, M.J. Elsevier 2009 Current Applied Physics Vol.9 No.1

The nano-size metallic aperture array has been fabricated using conventional semiconductor fabrication techniques and focused ion beam. The micron size patterns were transferred on SOI wafer using photographic patterning process, and the plateau pyramidal structures were fabricated using wet Si etching with alkaline solution followed by thermal oxidation. In order to reveal the plateau type pyramid, the backside Si bulk etching was performed. The metallic Al thin film was deposited and the nano-apertures with the diameters ranging from 190nm to 380nm were fabricated using focused ion beam milling method. The skin-depth of the Al thin film at 532nm wavelength is known to be ∼10nm. The deposited Al thin film is thick enough to become opaque. Circular types of periodic grooves were fabricated around the sub-wavelength size nano-aperture in order to examine the transmittance of the light coupled to circular periodic grooves. The far-field measurements for the optical transmittance through a sub-wavelength size nano-probe have been investigated and found to be up to 10<SUP>3</SUP> fold increase, compared to the output intensity of aperture without groove patterns.

Corrosion and Nanomechanical Behaviors of 16.3Cr-0.22N-0.43C-1.73Mo Martensitic Stainless Steel

( Rahul Ghosh ),( S. Chenna Krishna ),( A. Venugopal ),( P. Ramesh Narayanan ),( Abhay K. Jha ),( P. Ramkumar ),( P. V. Venkitakrishnan ) 한국부식방식학회(구 한국부식학회) 2016 Corrosion Science and Technology Vol.15 No.6

The effect of nitrogen on the electrochemical corrosion and nanomechanical behaviors of martensitic stainless steel was examined using potentiodynamic polarization and nanoindentation test methods. The results indicate that partial replacement of carbon with nitrogen effectively improved the passivation and pitting corrosion resistance of conventional high-carbon and high- chromium martensitic steels. Post-test observation of the samples after a potentiodynamic test revealed a severe pitting attacks in conventional martensitic steel compared with nitrogen- containing martensitic stainless steel. This was shown to be due to (i) microstructural refinement results in retaining a high-chromium content in the matrix, and (ii) the presence of reversed austenite formed during the tempering process. Since nitrogen addition also resulted in the formation of a Cr₂N phase as a process of secondary hardening, the hardness of the nitrogen- containing steel is slightly higher than the conventional martensitic stainless steel under tempered conditions, even though the carbon content is lowered. The added nitrogen also improved the wear resistance of the steel as the critical load (Lc2) is less, along with a lower scratch friction coefficient (SFC) when compared to conventional martensitic stainless steel such as AISI 440C.