Enhanced photoluminescence response of Ca²⁺/Ba²⁺ substituted solid solutions of SrS:Ce phosphors

Vij, Ankush,Kumar, Shalendra,Won, S.O.,Chae, K.H.,Dubey, Abhinav,Kumar, Ravi Elsevier 2018 Materials letters Vol.227 No.-

<P><B>Abstract</B></P> <P>The quest of improving luminescence efficiency in alkaline earth sulfide phosphors has been of great interest due to their applications in diverse areas. We synthesized SrS:Ce<SUB>0.05</SUB>, Sr<SUB>0.75</SUB>Ba<SUB>0.20</SUB>S:Ce<SUB>0.05</SUB>, Sr<SUB>0.75</SUB>Ca<SUB>0.20</SUB>S:Ce<SUB>0.05</SUB> and Sr<SUB>0.75</SUB>Ca<SUB>0.10</SUB>Ba<SUB>0.10</SUB>S:Ce<SUB>0.05</SUB> phosphors using solid state diffusion method. X-ray diffraction patterns of all the samples were found similar to the cubic SrS phase except minor shifts in angles. To ascertain the valence state of Ce, near edge X-ray absorption fine structure spectroscopy was employed using synchrotron radiations. We simulated Ce M<SUB>5,4</SUB>-edges of Ce<SUP>3+</SUP> ions using atomic multiplet calculations, which agrees well with the experimental data, clearly suggesting that Ce enters as Ce<SUP>3+</SUP> in all the samples. The photoluminescence spectra of synthesized phosphors exhibit blue-green emission assigned to the 5d-4f transitions in Ce<SUP>3+</SUP> levels, with minor shifts in wavelength. Interestingly, Ca<SUP>2+</SUP>/Ba<SUP>2+</SUP>substitution in SrS:Ce phosphors increases the PL intensity considerably. In comparison to SrS:Ce<SUB>0.05</SUB> , PL intensity of Sr<SUB>0.75</SUB>Ca<SUB>0.10</SUB>Ba<SUB>0.10</SUB>S:Ce<SUB>0.05</SUB> phosphors was enhanced by 2.7 times, which may be exploited in many optical applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Probed the effect of Ca<SUP>2+</SUP>/Ba<SUP>2+</SUP> substituted solid solutions of SrS:Ce<SUB>0.05</SUB> phosphors. </LI> <LI> NEXAFS spectra collected at Ce-M<SUB>5,4</SUB> edges confirms presence of Ce<SUP>3+</SUP>. </LI> <LI> PL intensity increases appreciably with Ca<SUP>2+</SUP>/Ba<SUP>2+</SUP> substitution in SrS:Ce. </LI> <LI> SrCaBaS:Ce exhibits maximum PL efficiency, 2.7 times as that of SrS:Ce phosphors. </LI> <LI> Enhanced PL emission in SrCaBaS:Ce can be exploited in many optical applications. </LI> </UL> </P>

Covalent versus Charge Transfer Modification of Graphene/Carbon-Nanotubes with Vitamin B1: Co/N/S–C Catalyst toward Excellent Oxygen Reduction

Vij, Varun,Tiwari, Jitendra N.,Kim, Kwang S. American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.25

<P>High-performance nonprecious cathodic catalysts for oxygen reduction are highly demanded for low temperature polymer electrolyte membrane fuel cells (PEMFCs). Here, we report a noble-meta- free, nitrogen and sulfur codoped graphene (G)/carbon-nanotube(CNT) material decorated with Co nanoparticles (NPs), which serve as catalytic sites for excellent oxygen reduction reaction (ORR) in basic and acidic media. Out of the cathodic catalysts synthesized by either covalent (cov) or charge transfer (CT) modification of graphen oxide (GO) with thiamine (Th: Vitamin B1), ThG/CNT/Co-cov shows more promising ORR properties than ThG/CNT/Co-CT. Catalyst ThG/CNT/Co-cov exhibits onset/halfwave potentials of 0.95/0.86 V in 0.1 M KOH and 0.92/0.83 V in 0.1 M HClO4, which are comparable to those of commercial catalyst Pt/C (0.95/0.86 V). As compared to Pt/C, our catalyst shows higher current densities of 6.72 mA cm(-2) in basic medium and 7.08 mA cm(-2) in acidic medium at 0.55 V (vs reversible hydrogen electrode (RHE)). It also exhibits better catalytic stability and methanol tolerance. High catalytic efficiency and stability of ThG/CNT/Co-cov show a promising prospect of materialization of PEMFCs for clean energy production.</P>

Radiofrequency in arthroscopic shoulder surgery: a systematic review

Neeraj Vij,Joseph N. Liu,Nirav Amin 대한견주관절학회 2023 대한견주관절의학회지 Vol.26 No.4

Background: Radiofrequency has seen an increase in use in orthopedics including cartilage lesion debridement in the hip and knee as well as many applications in arthroscopic shoulder surgery. The purpose of this systematic review is to evaluate the safety and usage of radiofrequency in the shoulder. Methods: This systematic review was registered with PROSPERO (international registry) and followed the preferred reporting items for systematic review and meta-analysis protocols (PRISMA-P) guidelines. Embase and PubMed were searched using: “shoulder,” “rotator cuff,” “biceps,” “acromion” AND “monopolar,” “bipolar,” “ablation,” “coblation,” and “radiofrequency ablation.” The title and abstract review were performed independently. Any discrepancies were addressed through open discussion. Results: A total of 63 studies were included. Radiofrequency is currently utilized in impingement syndrome, fracture fixation, instability, nerve injury, adhesive capsulitis, postoperative stiffness, and rotator cuff disease. Adverse events, namely superficial burns, are limited to case reports and case series, with higher-level evidence demonstrating safe use when used below the temperature threshold. Bipolar radiofrequency may decrease operative time and decrease the cost per case. Conclusions: Shoulder radiofrequency has a wide scope of application in various shoulder pathologies. Shoulder radiofrequency is safe; however, requires practitioners to be cognizant of the potential for thermal burn injuries. Bipolar radiofrequency may represent a more efficacious and economic treatment modality. Safety precautions have been executed by institutions to cut down patient complications from shoulder radiofrequency. Future research is required to determine what measures can be taken to further minimize the risk of thermal burns.

Need for a RS and GIS Based-Risk Assessment, Preparedness and Prevention of Crowd Disasters

Monika Vij 세계문화관광학회 2010 International Journal of Culture and tourism Resea Vol.3 No.1

Crowds occur frequently, usually without serious problems. Occasionally venue inadequacies and deficient crowd management result in injuries and fatalities. The crowd incidents occur in a wide variety of venues and different circumstances. There is an imperative need to put in place an effective management, control and monitoring mechanism to prevent avoidable tragedies. As an effort in this direction, the scholar has made an attempt at studying the risk assessment, preparedness and prevention of crowd disaster in the religious pilgrimage of Shri Mahakelshwar at Ujjain where millions of people throng throughout the year.

Study of the Electronic Structure and Luminescence of Mn-doped SrS Phosphors

Ankush Vij,Sanjeev Gautam,채근화,R. Brajpuriya,S.P. Lochab 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.10

In this paper, the electronic structure and the luminescence properties of Mn (1 mole%)-doped SrS phosphors synthesized by using the solid state diffusion method are reported. The X-ray diffraction pattern reveals a single-phase rocksalt structure, and the average crystallite size calculated using a Williamson-Hall plot is 72 nm. The near-edge X-ray absorption fine structure (NEXAFS) collected at Mn L_3,2-edges confirms the presence of divalent Mn in SrS. A bright green photoluminescence (PL) at 547 nm is observed at an excitation wavelength of 355 nm, which may be attributed to the ⁴<i>T</i>₁−⁶<i>A</i>₁ inner atomic transition of the 3<i>d</i> electrons in the Mn²⁺ ion under the cubic crystal field of SrS. We have also studied the thermoluminescence (TL) of UV (254 nm)-irradiated Mn-doped SrS phosphors. The TL glow curve has a well-resolved single peak around 360 K, which shifts slightly to lower temperatures with increasing UV exposure time, confirming second-order kinetics. A kinetic analysis of the experimental TL glow curve has been carried out using Chen’s peak shape method to determine the trapping parameters.

Summative program evaluation of a Student-Led Seminar Series in the subject of physiology: an outcome-based study

Vinu Vij,Pallavi Chitnis,Sadhana Mendhurwar 한국의학교육학회 2022 Korean journal of medical education Vol.34 No.1

Purpose: Active involvement of students in their learning process is a recommended andragogical approach to increase student engagement. Many new teaching-learning strategies based on active learning have been implemented, but their efficacies to achieve the proposed benefits of attaining knowledge, skills, and attitude have not been evaluated, especially in the field of medical education. We substituted passive learning in the conventional tutorial classes with an active-learning strategy of Student-Led Seminar Series (SLSS) in the subject of physiology over 4 months and performed program evaluation for the SLSS. Methods: Sixty-four first-year medical undergraduate students volunteered to participate, who were divided into groups to present seminars on the allocated topics under the guidance of a mentor. At the end of 4 months, program evaluation was done using Kirkpatrick’s model of evaluation—levels 1 and 2, which correspond to reaction and learning, respectively. Results: Statistically significant improvement was observed in students’ satisfaction, and the self-perceived increase was observed in knowledge, skills, and attitude. Conclusion: Program evaluation of SLSS not only established the significant impact of SLSS as an andragogical approach but also helped us in the improvisation of the program for the next cycle.

A Comparative Study between the Use of Biliary Stent and T-Tube for Biliary Decompression after Laparoscopic Common Bile Duct Exploration

( Vikesh Vij ),( Rahul Yadav ),( Jeevan Kankaria ),( Raj Kamal Jenaw ) 대한간학회 2018 춘·추계 학술대회 (KASL) Vol.2018 No.1

Aims: Laparoscopic common bile duct exploration (LCBDE) and cholecystectomy as a single-stage treatment of choledocholithiasis have been shown to be superior when compared to the two stage management. Decompression after supra-duodenal choledochotomy is common practice as it reduces the chance of bile leaks. We conducted a randomized comparative study to compare the feasibility and outcomes in patients undergoing biliary stent insertion versus T-tube drainage following LCBDE via choledochotomy. Methods: The study involved 64 patients with choledocholithiasis, half of which underwent biliary decompression after LCBDE using biliary stent and in the other half T-tube was used. Results: Patients in the stent group had significantly shorter operative time, lesser post-operative complications, lesser hospital stay and earlier return to normal activity (P<0.001). Conclusions: In our study, we found there is a significant reduction in length of hospital stay and morbidity for patients that have ante-grade biliary stent decompression of the CBD post laparoscopic choledochotomy when compared to T-Tube drainage. This implies that ante grade biliary stent insertion is likely to reduce costs and increase overall patient satisfaction.

A Smart and Automated Negotiation System based on Linear Programming in a Multilateral Environment

Sheetal Vij,Madhur Patrikar,Debajyoti Mukhopad,Avinash Agrawal 한국산학기술학회 2015 SmartCR Vol.5 No.6

Automated negotiation is a branch of e-commerce. Successful management of purchase and sale activities depends not only on selecting the right products or services but also on choosing the best method for buying and selling them. We propose a linear programming and pattern matching–based multilateral automated negotiation system. We compared some methods of automated negotiation. A multilateral negotiation system gives better results for participants than bilateral automated negotiation. The technique of pattern matching–based automated negotiation gives fast results and reduces the overhead from calculations. Automated negotiations are not an easy task without the interactions of human beings. Automated negotiation can be done in bilateral or multilateral environments. In this paper, we consider many-to-many negotiations where agents concurrently negotiate with many other agents. In this paper, we also propose a matrix method to manage the concurrent negotiations conducted by multiple buyer agents with multiple seller agents.

Need for a RS and GIS Based – Risk Assessment, Preparedness and Prevention of Crowd Disasters

Dr. Monika Vij 세계문화관광학회 2010 Conference Proceedings Vol.11 No.0

Crowds occur frequently, usually without serious problems. Occasionally venue inadequacies and deficient crowd management result in injuries and fatalities. The crowd incidents occur in a wide variety of venues and different circumstances. There is an imperative need to put in place an effective management, control and monitoring mechanism to prevent avoidable tragedies. As an effort in this direction, the scholar has made an attempt at studying the risk assessment, preparedness and prevention of crowd disaster in the religious pilgrimage of Shri Mahakelshwar at Ujjain where millions of people throng throughout the year.

Evidence of a moderate refrigerant capacity in cation disordered Ruddlesden-Popper compounds A1.4Sr1.6Mn2O7 (A = La, Pr, Nd) probed with various figures of merit

Kumar Akshay,Vij Ankush,Huh Seok Hwan,Kim Jong-Woo,Sharma Mohit K.,Kumari Kavita,Yadav Naveen,Akram Fazli,구본흔 한국물리학회 2023 Current Applied Physics Vol.49 No.-

We investigated the influence of structural disorders on the magnetic and magnetocaloric (MC) properties upon A-site rare-earth substitution in A1.4Sr1.6Mn2O7 (A = La, Pr, Nd) Ruddlesden-Popper (R–P) compounds. The samples were produced through the solid-state method, and the structural analysis indicated formation of R–P phase with the Jahn-Teller distortion parameter varying from highest in La1.4Sr1.6Mn2O7 (LSMO) to Nd1.4Sr1.6Mn2O7 (NSMO) and followed by Pr1.4Sr1.6Mn2O7 (PSMO). Hence, the magnetization value was increased in LSMO sample implying an enhanced interbilayer and interlayer spin correlations. It resulted in a high value of MC parameters like temperature average entropy change (TEC) and relative cooling power (RCP) of 4.21 J/kgK and 87 J/kg for LSMO, while lowest value of 0.53 J/kgK and 27 J/kg for PSMO respectively, at 2.5 T field. The room temperature MC response in PSMO, whereas a large TEC in LSMO and NSMO compounds advocate their candidacy in broad range of refrigeration applications.