Synthesis, magnetic and Mossbauer spectroscopic studies of Cr doped lithium ferrite nanoparticles

Srivastava, M.,Layek, S.,Singh, J.,Das, A.K.,Verma, H.C.,Ojha, A.K.,Kim, N.H.,Lee, J.H. Elsevier Sequoia 2014 JOURNAL OF ALLOYS AND COMPOUNDS Vol.591 No.-

Lithium-based ferrites are promising and potential magnetic materials for microwave applications. They possess a spinel (AB<SUB>2</SUB>O<SUB>4</SUB>) type crystal structure, where the distributions of metal cations over the tetrahedral (A) and octahedral (B) voids play a crucial role for exhibiting different physical properties. Among various parameter of synthesis, pH is an important factor that influences the cation distribution over A and B voids, overall growth of the nanoparticles and different physical properties. In the present work single phase Cr substituted lithium ferrite nanoparticles have been synthesized by the sol-gel method at different pH. The phase identification and crystallite size have been probed by X-ray diffraction studies. The crystallite size changes by 44.2-48.8nm upon varying the pH from 3.5 to 11.5. In order to investigate the cations distribution at A/B sites, Mossbauer spectroscopic measurements were done. The values of magnetic hyperfine field obtained from the Mossbauer data for the A and B sites are ~49.5T and 51T, respectively. Moreover, it is observed that the area ratio of B site to A site increases with increasing the pH. This observation further suggests that the B site is more preferable for Fe<SUP>3+</SUP> cations at higher pH than the A site. The magnetic parameter such as saturation magnetization (M<SUB>s</SUB>), remanent magnetization (M<SUB>r</SUB>), coercive field (H<SUB>C</SUB>) and squareness (S) are determined by vibrating sample magnetometer (VSM) measurements, which show a consistent increase with increasing pH. The reason for the variation in magnetic properties has been explained on the basis of increased Fe<SUP>3+</SUP> cation occupancies at the B site and size effect, which is well supported by Mossbauer spectroscopic and XRD studies.

Development of High-Current Sheet Beam Cathodes for Terahertz Sources

Lili Li,Yiman Wang,Wei Liu,Yanchun Wang,Jinshu Wang,Srivastava, A.,Jin-Kyu So,Gun-Sik Park IEEE 2009 IEEE transactions on electron devices Vol.56 No.5

<P>Generation of a sheet beam directly from a scandia-doped dispenser cathode has been investigated and optimized by means of beam-profile simulations and measurements. Rectangular beams 600 mum wide and 100 mum thick with current densities over 50 A/cm<SUP>2</SUP> have been generated. The beams are stable for at least several hundred hours with the cathodes operating at 950degC<SUB>b</SUB>, making them promising candidates for application in the next generation of terahertz vacuum electron devices such as a 0.5-THz superradiant Smith-Purcell radiation source.</P>

Stoichiometry dependent changes in the optical properties and nanoscale track formation of PECVD grown a-SiNx:H thin films upon 100 MeV Au8+ ion irradiation

Gupta Harsh,Ghosh Santanu,Khan Saif A.,Srivastava Himanshu,Srivastava Arvind,Srivastava Pankaj 한국물리학회 2021 Current Applied Physics Vol.24 No.-

-SiNx:H thin films of different stoichiometry grown by PECVD were subjected to irradiation by 100 MeV Au8+ ions with various fluences to understand the effect of stoichiometry on properties of thin films upon irradiation. Ellipsometry and UV–Vis study suggest the variation in the refractive index of thin films with fluence. The evolution of Hydrogen due to irradiation is quantified with the help of ERDA. RBS was probed to study the change in thin films’ composition upon irradiation, which further helps understand the change in thin films’ optical properties. Quenching of photoluminescence in the films with all stoichiometries was also observed due to ion irradiation. X-TEM images show the formation of discontinuous ion tracks of radius 2.5 nm in the film closer to silicon nitride stoichiometry. However, Si rich film does not show the clear formation of tracks. Results are explained in the framework of the Thermal spike mechanism of ion-solid interaction.

Plasma Vascular Endothelial Growth Factors A and C in Patients undergoing Prostatic Biopsy and TURP for Suspected Prostatic Neoplasia

Singh, A.N.,Gautam, Kirti A.,Dalela, D.,Sankhwar, S.N.,Natu, S.M.,Sankhwar, P.L.,Srivastava, A.N. Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.3

Background: Formation of new blood vessels is necessary for the development and spread of neoplasms more than 1 mm3 in volume, angiogenesis being responsible for formation of new from pre-existing blood vessels. Vascular endothelial growth factor (VEGF) is pivotal and the best studied angiogenic factor in all human cancers. Therefore we designed this study to investigate the role of VEGF-A and VEGF-C in prostate cancer in comparison with BPH controls in a north Indian population. Methods: In this case-control study a total of 100 subjects were included on the basis of confirmed histopathological reports, out of which 50 were prostate cancer patients and the other 50 were BPH patients with PSA levels >2 ng/ml and abnormal digital rectal examination (DRE) findings during September 2009 to August 2011 from the Department of Urology, KGMU, Lucknow, India. Plasma levels of VEGF were determined using quantitative immunoassay (ELISA-enzyme linked immunosorbent assay). Statistical analysis was carried out using SPSS 15.0 version. Results: The mean age of prostate cancer ($67.6{\pm}5.72$) patients was significantly higher (p=0.005) than BPH ($63.6{\pm}7.92$) patients. Expression of VEGF-A was not significantly higher in disease stage C1 than D1 or D2 and A or B (p=0.13) while the level of VEGF-A was significantly higher (p=0.04) in prostate cancer as compared to BPH subjects (PCa=13.0 pg/ml, BPH=6.8 pg/ml). Levels of VEGF-C were similar in both groups (PCa=832.6 pg/ml, BPH=823.7 pg/ml). In ROC curve, the area under curve (AUC) was 0.70 (95%CI: 0.60-0.80) and the cut-off value for which a higher proportion of patients was correctly classified (20%) was 26.0 pg/mL. Conclusion: Although VEGF-A is increased in cancer prostate patients a statistically significant correlation could not be established in this study. VEGF-C was not found to be a useful biomarker.

Modeling of Absorption of NO_2 with Chemical Reaction in a Falling Raindrop

Pareek, Vishnu,Srivastava, Vinod K.,Adesina, Adesoji A. 한국화학공학회 2003 Korean Journal of Chemical Engineering Vol.20 No.2

A model has been proposed for the scavenging of NO_2 in a falling raindrop. After absorption, aqueous NO_2 undergoes a second order reaction to form various ions such as NO^-_2, NO^-_3 and H^+. The model is based on the unsteady state convective diffusion equation which was solved for given boundary conditions by using impicit alternate direction(ADI) method. The circulation of fluid inside and outside the raindrop has been taken into account to realistically describe the flow field in the numerical domain. The model predictions indicate that the pH of a raindrop is a direct function of the drop size and bulk concentration of NO^-_2. The model predicted a pH of about 4.9 for a 100micron raindrop falling through a 20-ppb ambient concentration of NO_2. For the same ambient concentration of NO_2, a 10-micron raindrop would have a pH of about 4.75. The predictions also suggested that for all practical purposes the gas phase resistance may be taken as the rate-controlling step. The predicted values of gas-side mass transfer coefficient compared well with the estimated values using standard mass transfer correlations.

Breakthrough behaviour of NBC canister against carbon tetrachloride: a simulant for chemical warfare agents

Avanish Kumar Srivastava,D. Shah,T.H. Mahato,Beer Singh,A. Saxena,A.K. Verma,S. Shrivastava,A. Roy,S.S. Yadav,A.R. Shrivastava 한국탄소학회 2012 Carbon Letters Vol.13 No.2

A nuclear, biological, chemical (NBC) canister was indigenously developed using active carbon impregnated with ammoniacal salts of copper (II), chromium (VI) and silver (I), and high efficiency particulate aerosol filter media. The NBC canister was evaluated against carbon tetra chloride (CCl4) vapours, which were used as a simulant for persistent chemical warfare agents under dynamic conditions for testing breakthrough times of canisters of gas masks in the National Approval Test of Respirators. The effects of CCl4 concentration, test flow rate, temperature, and relative humidity (RH) on the breakthrough time of the NBC canister against CCl4 vapour were also studied. The impregnated carbon that filled the NBC canister was characterized for surface area and pore volume by N2 adsorption-desorption isotherm at liquid nitrogen temperature. The study clearly indicated that the NBC canister provides adequate protection against CCl4 vapours. The breakthrough time decreased with the increase of the CCl4 concentration and flow rate. The variation in temperature and RH did not significantly affect the breakthrough behaviour of the NBC canister at high vapour concentration of CCl4, whereas the breakthrough time of the NBC canister was reduced by an increase of RH at low CCl4 vapour concentration.

Determination of Double-K Fracture Parameters of Concrete Using Split-Tension Cube

Shashi Ranjan Pandey,Shailendra Kumar,A. K. L. Srivastava 한국콘크리트학회 2016 International Journal of Concrete Structures and M Vol.10 No.2

This paper presents a revised procedure for computation of double-K fracture parameters of concrete split-tension cube specimen using weight function of the centrally cracked plate of finite strip with a finite width. This is an improvement over the previous work of the authors in which the determination of double-K fracture parameters of concrete for split-tension cube test using weight function of the centrally cracked plate of infinite strip with a finite width was presented. In a recent research, it was pointed out that there are great differences between a finite strip and an infinite strip regarding their weight function and the solution of infinite strip can be utilized in the split-tension specimens when the notch size is very small. In the present work, improved version of LEFM formulas for stress intensity factor, crack mouth opening displacement and crack opening displacement profile presented in the recent research work are incorporated. The results of the double-K fracture parameters obtained using revised procedure and the previous work of the authors is compared. The double-K fracture parameters of split-tension cube specimen are also compared with those obtained for standard three point bend test specimen. The input data required for determining double-K fracture parameters for both the specimen geometries for laboratory size specimens are obtained using well known version of the Fictitious Crack Model.

Transvaginal ultrasound guided trigone and bladder injection: A cadaveric feasibility study for a novel route of intradetrusor chemodenervation

Raveen Syan,Mason A. Briggs,John C. Olivas,Sakti Srivastava,Craig V. Comiter,Amy D. Dobberfuhl 대한비뇨의학회 2019 Investigative and Clinical Urology Vol.60 No.1

Purpose: OnabotulinumtoxinA (BTX) detrusor chemodenervation is an efficacious third-line treatment for overactive bladder. Despite high clinical efficacy rates for BTX injection, many patients refuse initial or repeat treatment due to the invasiveness of the cystoscopic route of delivery. We assess the feasibility of injecting the trigone and posterior bladder wall via a transvaginal route under ultrasound guidance using a human cadaveric model. Materials and Methods: Eight de-identified anonymous fresh female deceased donor cadaver pelvises were placed in supine split leg position. A transvaginal ultrasound probe guided injections of India ink into the trigone in 3 sites and the posterior wall in 2 sites. Full thickness bladder biopsies were then obtained and histologic analysis was performed to confirm presence of India ink in the detrusor layer. Results: The mean time from day of death was 11.0 days (range, 4.0–23.0 days). Three to five bladder biopsies were obtained per cadaver, for a total of 34 specimens (20 trigone, 14 posterior wall). Histologic analysis revealed presence of India ink within the detrusor layer in 8/8 (100.0%) of cadavers. The surgeon's perception of appropriate targeting under ultrasound guidance was confirmed in 8/8 cadavers (100.0%) involving the bladder trigone, and 7/8 (87.5%) involving the posterior wall. Of injections that were believed to have appropriately targeted the detrusor layer, 22/34 specimens (64.7%) demonstrated the presence of India ink under histologic analysis. Conclusions: Intradetrusor injection of the bladder trigone and posterior wall under transvaginal ultrasound guidance is feasible and has acceptable accuracy.

Improved mixing efficiency and biomass productivity of Ettlia sp. in co-cultivation system with loaches

La, H.J.,Seo, S.H.,Lee, J.Y.,Lee, C.S.,Kim, B.H.,Srivastava, A.,Han, M.S.,Oh, H.M. Elsevier B.V 2016 Algal research Vol.17 No.-

<P>Maintaining a homogeneous cell suspension has been identified as a key parameter for higher biomass productivity of microalgae cultivation systems. This study proposes an alternative mixing method where microalgae are co-cultivated with loaches to improve the mixing efficiency and microalgal biomass productivity. The highly settleable microalga, Ettlia sp. showed a stable temporal cell concentration at the specified sampling sites when co-cultivated with 10 loaches, whereas it sank to the bottom of a 20 L rectangular vessel (20 cm deep) within 12 h in a water-pump-assisted mixing system. As a consequence of the better mixing efficiency in the co-cultivation system, biomass and lipid productivities of co-cultivation system were 66.9 +/- 8.3 mg/L/day and 14.7 +/- 1.0 mg/L/day, respectively, and were about 57.6% and 32.4% higher than the results from the water-pump-assisted mixing system. In addition, when the co-cultivation systems were cultured under various depth conditions (10, 16, 20, 40, 60, 80 cm deep) to determine the maximum areal biomass and lipid productivity, the system showed the highest biomass productivity with a depth of around 16-20 cm, while the lipid content and productivity were sharply lowered at this depth. The introduction of loaches also altered the microbial community structure of the co-cultivation systems. Therefore, these results suggest that the co-cultivation of loaches can be used as an efficient mixing method, while also introducing new ecological players, the loaches themselves and associated microorganisms, which can improve the sustainability of microalgae cultivation systems. (C) 2016 Elsevier B.V. All rights reserved.</P>

Effect of ethyl acetate aroma on viability of human breast cancer and normal kidney epithelial cells in vitro

Mohsin A. Khan,Rumana Ahmad,Anand N. Srivastava 한국한의학연구원 2017 Integrative Medicine Research Vol.6 No.1

Background: Aromatherapy is used in clinical settings for patients suffering from several chronic and critical diseases such as cancer. Ethyl acetate (EA) is a colorless liquid with a characteristic fruity smell and is naturally present in fruits and wines. Methods: In the present study, the effect of the aroma of EA was evaluated on human breast cancer cell line MDA-MB-231 and normal cell line, Vero. Cell line viability and mechanism of EA cytotoxicity were determined by Trypan blue dye exclusion assay and phase contrast microscopy. Results: It was found that EA at a concentration of 0.026 M was effective in causing considerable cytotoxicity in breast cancer cells (without even coming in contact with the culture medium and cells), while showing no effect on normal cells. Mechanism of action of EA on cancer and Vero cells was investigated by DNA fragmentation and dye binding assays using agarose gel electrophoresis (AGE) and fluorescence microscopy/cytometry, respectively. It was found that EA aroma induced predominantly necrosis in the cancer cells exposed to it. Conclusion: A study such as this has not been attempted before and results need further investigation before EA aroma can be used as a complementary therapy.