Deepika singh - Academia.edu (original) (raw)

Papers by Deepika singh

Deep Ultra Violet (DUV) Diamond Light Emitting Diodes (LED's) MDA A STTR Phase I Project... more Deep Ultra Violet (DUV) Diamond Light Emitting Diodes (LED's) MDA A STTR Phase I Project "Deep Ultra-Violet (DUV) Light Emitting Diodes" Final Status Report Identification Number: DI-MGMT-80368 STTR Contract Number DASG60-02-P-0285 Sponsored by Missile ...

Thin Solid Films, 2009

Superhydrophobic polytetrafluoroethylene films with hierarchical surface roughness were deposited... more Superhydrophobic polytetrafluoroethylene films with hierarchical surface roughness were deposited using pulse electron deposition technique. We were able to modulate roughness of the deposited films by controlling the beam energy and hence the electron penetration depth. The films deposited at higher beam energy showed contact angle as high as 166°. The scanning electron and atomic force microscope studies revealed clustered growth and two level sub-micron asperities on films deposited at higher energies. Such dual-scale hierarchical roughness and heterogeneities at the water-surface interface was attributed to the observed contact angle and thus its superhydrophobic nature.

Applied Surface Science, 2008

Chemical mechanical polishing of free-standing GaN substrates is found to reduce the reverse leak... more Chemical mechanical polishing of free-standing GaN substrates is found to reduce the reverse leakage current of Ni/Au Schottky diodes fabricated on the Ga-face. The barrier height extracted from currentvoltage measurements is found to increase from 0.4 eV on un-treated ...

Genesis (New York, N.Y. : 2000), Jan 2, 2016

Many developmental processes are inherently robust due to network organization of the participati... more Many developmental processes are inherently robust due to network organization of the participating factors and functional redundancy. The heterogeneity of the factors involved and their connectivity puts these processes at risk of abrupt system collapse under stress. The polarization of the one-cell C. elegans embryo constitutes such an inherently robust process with functional redundancy. However, how polarization is affected by acute stress has not been thoroughly investigated. Here, we report that heat shock (34°C, 1 h) triggers a highly reproducible loss of the anterior and collapse of the posterior polarity domains. Temperature-dependent loss of cortical non-muscle myosin II drastically reduces cortical tension and leads to internalization of large plasma membrane domains including the membrane-associated polarity factor PAR-2. After internalization, plasma membrane vesicles and associated factors cluster around centrosomes and are thereby withdrawn from the polarization proce...

Powder Technology, 2013

Surface modification of precipitated calcium carbonate particles in a planetary ball mill using d... more Surface modification of precipitated calcium carbonate particles in a planetary ball mill using different dispersants such as stearic acid, oleic acid, palmitic acid, salicylic acid, oleyl amine, DDSA (dodecenyl succinic anhydride), ODSA (octadecenyl succinic anhydride), TPSA (tetra propenyl succinic anhydride) as modification agent was done in order to find out the potential of dispersant in surface modification and for making dispersion in hydrocarbon oil was investigated. Different dispersants were ball milled keeping all the parameters for processing (milling) like-milling time, ball ratios, sample dosage and milling constant. The physical properties of the hydrophobically modified calcium carbonate were measured; the particle size and morphology of the resulting samples were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The surface coating thickness was also estimated by geometric calculation using results of TEM and TGA considering the formation of core shell structure.

ACS Catalysis, 2014

H 2 S has been used as a probe molecule both in an "in situ" poisoning experiment and in intermed... more H 2 S has been used as a probe molecule both in an "in situ" poisoning experiment and in intermediate-temperature heat-treatment steps during and after the preparation of FeNC catalysts in an attempt to analyze its effect on their ORR activity. The heat treatments were employed either on the ball-milled precursor of FeNC or after the Ar-NH 3 high temperature heat treatments. ORR activity of the H 2 S-treated catalysts was seen to be significantly lower than the sulfur-free catalysts, whether the sulfur exposure was during a half-cell testing, or as an intermediate-temperature exposure to H 2 S. The incorporation of sulfur species and interaction of Fe with sulfur were confirmed by characterization using XPS, EXAFS, TPO, and TPD. This study provides crucial evidence regarding differences in active sites in FeNC versus nitrogen-containing carbon nanostructured (CN x) catalysts.

Scientific reports, Jan 3, 2014

Although tailored wet ball milling can be an efficient method to produce a large quantity of two-... more Although tailored wet ball milling can be an efficient method to produce a large quantity of two-dimensional nanomaterials, such as boron nitride (BN) nanosheets, milling parameters including milling speed, ball-to-powder ratio, milling ball size and milling agent, are important for optimization of exfoliation efficiency and production yield. In this report, we systematically investigate the effects of different milling parameters on the production of BN nanosheets with benzyl benzoate being used as the milling agent. It is found that small balls of 0.1-0.2 mm in diameter are much more effective in exfoliating BN particles to BN nanosheets. Under the optimum condition, the production yield can be as high as 13.8% and the BN nanosheets are 0.5-1.5 μm in diameter and a few nanometers thick and of relative high crystallinity and chemical purity. The lubrication properties of the BN nanosheets in base oil have also been studied. The tribological tests show that the BN nanosheets can gre...

Chen/Non-Noble Metal Fuel Cell Catalysts, 2014

ABSTRACT Novel carbon materials such as fullerene, graphenes, and carbon nanotubes of various mor... more ABSTRACT Novel carbon materials such as fullerene, graphenes, and carbon nanotubes of various morphologies have seen immense development in the last few decades due to their widespread potential applications. Doping with heteroatoms such as nitrogen, phosphorus, and sulfur brings about significant changes in the electronic and structural properties, which makes them viable for use in semiconductors, fuel cells, and various other catalytic processes. Here, we present a brief review of the evolution of carbon materials (doped and undoped) and their applications as oxygen reduction reaction (ORR) catalysts for proton exchange membrane (PEM) fuel cells. The effect of transition metal on the catalytic activity of these materials has been reviewed, by comparing literature that report enhancement of catalytic activity owing to contribution of transition metal, with those that attribute activity to heteroatom doping: primarily nitrogen functional groups. This chapter covers the breadth of literature on these doped carbon materials for ORR, directing towards the many questions that remain to be answered.

Communicative & Integrative Biology, 2014

International Journal of Computer Applications, 2012

Speech synthesis systems which involve concatenation of recorded speech units are currently very ... more Speech synthesis systems which involve concatenation of recorded speech units are currently very popular. These systems are known for producing high quality, naturalsounding speech as they generate speech by joining together waveforms of different speech units. This method of speech generation is quite practical. However the speech units that are being concatenated may have different spectra on either side of the concatenation points. Such mismatches are spectral in nature and give rise to spectral discontinuity in concatenated speech waveforms. The presence of such discontinuities can be very distracting to the listener and degrade the overall quality of output speech. This paper proposes a speech signal processing technique that deals with the problem of spectral discontinuity in the context of concatenated waveform synthesis. It involves the post-processing of the synthesized speech waveform in time domain. This technique is implemented on different single channel Punjabi wave audio files which were created by concatenating different Punjabi syllables. A listening test was conducted to evaluate the proposed technique, and it was observed that the spectral discontinuity is reduced to a large extent and the output speech sounds more natural with the reduction of audible noise.

Journal of Molecular Catalysis, 1988

... of India, for pro-viding financial assistance to (Miss) Deepika Singh. References 1 R. Filler... more ... of India, for pro-viding financial assistance to (Miss) Deepika Singh. References 1 R. Filler, Chem. Rev., 63 (1963) 21. 2 J. Mukherjee and KK Banerji, J. Org. Chem., 46 (1981) 2323. 3 PS Radhakrishnamurthi and NC Sahu, Indian J. Chem., 20A (1981) 269. 4 B. Shah, AL Jain ...

The Journal of Organic Chemistry, 2010

Part 1: experimental procedures and spectra data Contents: 1. Synthesis of nitrones……………………………………... more Part 1: experimental procedures and spectra data Contents: 1. Synthesis of nitrones……………………………………………………………………………..S2 2. Synthesis of acetylenes 2, 6-13…………………………………………………………………S2 1. Synthesis of nitrones Nitrones 1, ent-1 and 20 were prepared according to Brandi's protocol. 1 2. Synthesis of acetylenes. Acetylene 3 was purchased from Aldrich. Acetylenes 23a and 23b were obtained from commercially available (R)-1-phenyl-2-propyn-1-ol (Aldrich) and (S)-3-butyn-2-ol (Aldrich) using standard silylation protocol. (S)-4-ethynyl-2,2-dimethyl-1,3-dioxolane (2): 2 A solution of D-glyceraldehyde acetonide 3 (1.03 g, 7.90 mmol) and the Bestmann-Ohira reagent 4 (2.42 g, 12.6 mmol) in methanol (50 mL) was cooled to 0 ºC. Anhydrous potassium carbonate (2.33 g, 16.8 mmol) was gradually added (30 min). The mixture was stirred for 12 h, allowing it to warm to room temperature. Saturated aqueous ammonium chloride (50 mL) was added and the aqueous solution was extracted with pentane (50 mL). The organic layer was separated, dried over magnesium sulfate, and the solvent carefully evaporated under reduced pressure (650 mbar, bath 35 ºC). After purification by flash-column chromatography (eluent pentane/diethyl ether 10:1), alkyne 2 (820 mg, 6.50 mmol; 82%) was isolated as a colourless oil. [α]D +40 (c 1.0, CH2Cl2) [lit. 2 +40.6 (c 1.1, CHCl3)]; IR (film)

Journal of Catalysis, 2012

The role of the transition metal used during the growth of non-noble metal electrochemical oxygen... more The role of the transition metal used during the growth of non-noble metal electrochemical oxygen reduction CN x catalysts was investigated through sulfur treatment, a well-known poison for transition metal-based catalysts. The intent of sulfur poisoning was to show the existence of an electrocatalytic active site in CN x that did not depend on iron. The sulfur treatment was shown to be effective on a platinum catalyst, as seen by the decreasing onset potential. The same treatment, however, not only showed no negative effect on the CN x catalyst, but enhanced its performance, as seen by the increase in the onset potential. This suggests that, if there are iron-based active sites in these catalysts, they are either sulfur tolerant or they do not participate in the electrocatalytic oxygen reduction. The deposition of sulfur onto CN x catalyst was verified by temperature-programmed oxidation and X-ray photoelectron spectroscopy. Iron K-edge X-ray absorption near edge structural analysis of the CN x catalyst suggested that the iron phase, which was primarily composed of nanometer-sized metallic particles, was unchanged by sulfur poisoning, suggesting that the residual iron left in these materials is not catalytically accessible.

International Journal of Geriatric Psychiatry, 2013

Our primary aim was to compare the rate of vascular depression among a clinical sample of African... more Our primary aim was to compare the rate of vascular depression among a clinical sample of African American and Caucasian depressed older adults. Secondary aims included characterizing the clinical and neuropsychological profile of vascular depression and comparing antidepressant response rates between patients with vascular and nonvascular depression. This was a two-site, multi-ethnic, open 8-week trial of antidepressant medication in older adults with depression. Men and women 50 years or older meeting DSM-IV criteria for nonpsychotic unipolar depression participated in this trial. Each participant underwent a comprehensive psychiatric and neuropsychological evaluation and a brain MRI, which were performed at baseline. Forty-six patients met inclusion and exclusion criteria. Forty-two of those patients received an MRI at baseline. Sixteen patients met criteria for vascular depression. Patients with vascular depression were significantly more likely to be African American and have a higher likelihood of being female, a higher rate of hypertension and psychomotor retardation, a lower rate of family history of affective illness, and frontal systems dysfunction on neuropsychological testing. The difference in response rates between patients with vascular and nonvascular depression did not reach statistical significance. This is the first study to document high rates of vascular depression in a clinical sample of African Americans and Caucasians. Our findings suggest that vascular depression may be overrepresented among African Americans, which is consistent with the high rates of cardiovascular disease, hypertension, and stroke in this population.

International Journal of Chemical Kinetics, 1988

Kinetics of oxidation of ethylene glycol and glycerol by acidic solution of N-bromoacetamide (NBA... more Kinetics of oxidation of ethylene glycol and glycerol by acidic solution of N-bromoacetamide (NBAI in the presence of ruthenium (111) chloride as a homogeneous catalyst and mercuric acetate as scavenger in the temperature range of 30-50°C have been reported. The ...

Applied Catalysis B: Environmental, 2012

Interaction of carbon monoxide with CN x catalysts was investigated using pulse chemisorption, DR... more Interaction of carbon monoxide with CN x catalysts was investigated using pulse chemisorption, DRIFTS, and cyclic voltammetry techniques. Pulsed chemisorption experiments showed no CO uptake over the CN x catalysts. Cyclic voltammetry and potential hold studies showed carbon monoxide not to have any electrocatalytic interaction with nitrogen-doped graphite surfaces and not to have any poisoning effect for the oxygen reduction reaction. This is in contrast to the preferential adsorption of CO in the presence of oxygen on ORR sites of Pt catalysts, inhibiting the oxygen reduction activity drastically. Cyanide poisoning experiments performed using KCN showed no activity loss for CN x , while Pt/VC catalysts showed significant deactivation. These studies suggest that it is unlikely for coordinated metal sites to have significant contribution to the oxygen reduction reaction in CN x catalysts.