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.

Structural, magnetic and optical properties of diluted magnetic semiconductor (DMS) phase of Ni modified CuO nanoparticles

Kumar Arvind,Kumar Manish,Chandra Sati Prakash,Srivastava Manish Kumar,Ghosh Surajit,Kumar Shiv 한국물리학회 2021 Current Applied Physics Vol.32 No.-

Control on the size of copper oxide (CuO) in the nano range is a highly motivating approach to study its multifunctional nature. The present investigation reports a sol-gel derived Ni doped CuO nanoparticles (Cu1- xNixO). Rietveld refinement of the XRD spectra confirms the formation of single monoclinic phase of Cu1-xNixO nanoparticles having crystallite size within the range of 19–21 nm. Raman spectra show the presence of characteristics Raman active modes and vibrational bands in the Cu1-xNixO samples that corroborate the monoclinic phase of the samples as revealed by refinement of XRD data. The estimated band gap of pure CuO is found to be ~1.43 eV, which decreases with the increase of dopant concentration into CuO matrix. This result is in line with estimated crystallite size. Magnetization curves confirm the weak ferromagnetic nature of Cu1-xNixO nanoparticles which reveal the DMS phase. This weak magnetic nature may be induced in the samples due to the exchange interaction between the localized magnetic d-spins of Ni ions and carriers (holes or electrons) from the valence band of pristine CuO lattice. Replacement of Cu+2 by Ni+2 ions into the host CuO lattice induces the magnetization. The quantified value of squareness ratio (S < 0.5) confirms the inter-grain magnetic interactions in the Cu1-xNixO nanoparticles which is also the reason of weak induced magnetization.

Intra-operative cerebral blood flow assessment by indocyanine green video-angiography after temporary arterial occlusion in aneurysm surgery and its clinical implications: a prospective study

Dutta Gautam,Jagetia Anita,Srivastava Arvind K,Singh Daljit,Singh Hukum,Chawla Rajiv,Agarwal Atul,Iqbal Mohd,Tandon Monica 대한뇌혈관외과학회 2021 Journal of Cerebrovascular and Endovascular Neuros Vol.23 No.3

Objective Indocyanine green video angiography (ICG-VA) is a routine while performing vascular surgery to assess patency of perforators, completeness of clipping and/or to assess patency of anastomosis. Its usefulness in assessing cerebral blood flow and perfusion is not well studied. This study is aimed to assess the cerebral blood flow and perfusion after temporary clipping and to correlate with the risk of ischemia. Methods Prospective analysis of intra-operative ICG-VA performed during temporary arterial occlusion in 38 patients from January 2014 to December 2018 was conducted. Co-relation with post-operative MR diffusion weighted imaging (MR DWI) in terms of vascular territory of interest within 48 hours of surgery was performed. Clinical outcome was assessed using modified Rankin Scale (mRS) score 1-month post-surgery. Results 43 aneurysms in 38 patients clipped using ICG-VA were included in this study. No side effect of ICG dye was seen in any patients. The number of times temporary clips applied had a direct relationship to the delay in appearance of ICG in the surgical field which became statistically significant after application of 3rd temporary clip. Nine (23.7%) patients developed ischemia following the procedure confirmed by post-operative MR DWI and all the ischemic cases had visible decrease in ICG fluorescence post-temporary clipping. Conclusions No previous study had tried to assess the intraoperative cerebral blood flow and perfusion during temporary clipping of parent vessels during aneurysm surgery. The use of ICG-VA can be extended to assess perfusion in desired territory by merely assessing the degree of opacification.

Impregnated Active Carbon-Shelf Life Studies and Its Evaluation Against Cyanogen Chloride with and without Canister

Singh, Beer,Saxena, Amit,Srivastava, Avanish Kumar,Dubey, Devendra Kumar,Gupta, Arvind Kumar Korean Carbon Society 2007 Carbon Letters Vol.8 No.4

Samples of active carbon of $1150\;m^2/g$ surface area were impregnated with ammoniacal salts of copper, chromium and silver, with and without triethylenediamine. The samples of impregnated carbon were aged at $50^{\circ}C$, with and without 90% RH (relative humidity), for a little more than one year and chemically evaluated periodically. Initially copper (II) and chromium (VI) reduced very fast in the samples in humid atmosphere to the extent of 30% and 60% respectively in four months. These values were found to be unaffected by the presence of triethylenediamine (TEDA) indicating that the chemical did not retard the reduction process of chromium (VI) and copper (II). However, in the absence of humidity the reduction of the impregnants was significantly less (10-12%, w/w) in four months. It was quite evident; therefore, that the moisture was mainly responsible for the reduction of chromium (VI) and copper (II) species in impregnated carbons. The prolonged ageing of the samples with and without triethylenediamme after four months with and without humid atmosphere showed that the extent of reduction of chromium (VI) was very low, i.e. 5-10% and of copper (II) was 2-25%. Silver is not reduced due to carbon, as it remained unchanged in concentration on storage. The impregnated carbon samples (100 g) without triethylenediamine, which were aged at room temperature for 5 years in absence of humidity and unaged when evaluated against cyanogen chloride (CNCl) at a concentration of 4 mg/L and airflow rate of 30 lpm showed a high degree of protection (80- 110 minutes).

Endovascular management of large and giant intracranial aneurysms: Experience from a tertiary care neurosurgery institute in India

Dutta Gautam,Singh Daljit,Jagetia Anita,Srivastava Arvind K,Singh Hukum,Kumar Anil 대한뇌혈관외과학회 2021 Journal of Cerebrovascular and Endovascular Neuros Vol.23 No.2

Objective With the development of endovascular technique and devices, large and giant intracranial aneurysms are increasingly being managed by this less invasive method. Here we discuss our experience on managing such aneurysms via endovascular technique. Methods Retrospective data on 42 patients with large and giant intracranial aneurysms managed by endovascular techniques between September 2015 to December 2017 at our neurosurgery institute were included in this analysis. Results There were a total 42 patients with 9 giant and 33 large aneurysms in this study. Eight aneurysms were treated by parent vessel occlusion, 22 aneurysms with coils and rest 12 aneurysms were treated with stent assisted coiling. Following the procedure, Raymond class I occlusion was accomplished in 31 (73.8%) patients while class Ⅱ in 9 (21.4%) and class Ⅲ in 2 (4.8%) patients. Overall morbidity and mortality were 9.5% and 14.3% respectively and favorable outcome was seen in 80.9% patients. Significant correlation was observed with clinical outcome and initial neurological status. Conclusions The study indicates that endovascular intervention is a safe and effective method in managing large and giant intracranial aneurysms with lesser morbidity and mortality. Objective With the development of endovascular technique and devices, large and giant intracranial aneurysms are increasingly being managed by this less invasive method. Here we discuss our experience on managing such aneurysms via endovascular technique. Methods Retrospective data on 42 patients with large and giant intracranial aneurysms managed by endovascular techniques between September 2015 to December 2017 at our neurosurgery institute were included in this analysis. Results There were a total 42 patients with 9 giant and 33 large aneurysms in this study. Eight aneurysms were treated by parent vessel occlusion, 22 aneurysms with coils and rest 12 aneurysms were treated with stent assisted coiling. Following the procedure, Raymond class I occlusion was accomplished in 31 (73.8%) patients while class Ⅱ in 9 (21.4%) and class Ⅲ in 2 (4.8%) patients. Overall morbidity and mortality were 9.5% and 14.3% respectively and favorable outcome was seen in 80.9% patients. Significant correlation was observed with clinical outcome and initial neurological status. Conclusions The study indicates that endovascular intervention is a safe and effective method in managing large and giant intracranial aneurysms with lesser morbidity and mortality.

Impregnated Active Carbon-Shelf Life Studies and Its Evaluation Against Cyanogen Chloride with and without Canister

Beer Singh,Amit Saxena,Avanish Kumar Srivastava,Devendra Kumar Dubey,Arvind Kumar Gupta 한국탄소학회 2007 Carbon Letters Vol.8 No.4

Samples of active carbon of 1150 m2/g surface area were impregnated with ammoniacal salts of copper, chromium and silver, with and without triethylenediamine. The samples of impregnated carbon were aged at 50℃, with and without 90% RH (relative humidity), for a little more than one year and chemically evaluated periodically. Initially copper (II) and chromium (VI) reduced very fast in the samples in humid atmosphere to the extent of 30% and 60% respectively in four months. These values were found to be unaffected by the presence of triethylenediamine (TEDA) indicating that the chemical did not retard the reduction process of chromium (VI) and copper (II). However, in the absence of humidity the reduction of the impregnants was significantly less (10-12%, w/w) in four months. It was quite evident; therefore, that the moisture was mainly responsible for the reduction of chromium (VI) and copper (II) species in impregnated carbons. The prolonged ageing of the samples with and without triethylenediamme after four months with and without humid atmosphere showed that the extent of reduction of chromium (VI) was very low, i.e. 5-10% and of copper (II) was 2-25%. Silver is not reduced due to carbon, as it remained unchanged in concentration on storage. The impregnated carbon samples (100 g) without triethylenediamine, which were aged at room temperature for 5 years in absence of humidity and unaged when evaluated against cyanogen chloride (CNCl) at a concentration of 4 mg/L and airflow rate of 30 lpm showed a high degree of protection (80- 110 minutes).

Study of electrospun polycarbosilane (PCS) nanofibrous web by needle-less technique

Mukesh Kumar Sinha,Biswa Ranjan Das,Raghwesh Mishra,Ashok Ranjan,Anurag Srivastava,Arvind Kumar Saxena 한국의류학회 2014 Fashion and Textiles Vol.1 No.1

This study reports on the various functional characteristics of silicon carbide (SiC) nanofibrous web. The SiC nanofibrous web was spun by the electrospinning technique using Nano Spider (needle-less) machine. The as-spun nanofibrous web was cured to 180°C and subsequently, pyrolized at 1000°C under inert nitrogen (N2) atmosphere to convert into silicon carbide nanofibrous web. The various properties of SiC web is characterized by using FESEM, Thermal Analysis, X-ray Diffraction, Energy Dispersive Spectroscopy (EDX), Atomic Force Microscopy and Surface Profilomertry. FESEM microphotographs indicated the interconnected fibres leading to pores of prepared SiC Nanofibrous web. Deep rooted fibre surface porosity was revealed by AFM. The thermal behavior of as-spun, cured and pyrolized PCS webs are influenced by the heat treatment at different temperatures. The surface roughness changes with the heat treatment of PCS nanofibrous webs. The pyrolized web carries higher surface roughness as compared to as-spun and cured webs. The EDX plots indicated the presence of C and Si elements in pyrolized PCS nanofibrous web.

Major forests and plant species discrimination in Mudumalai forest region using airborne hyperspectral sensing

Bodi Surya Pratap Chandra Kishore,Amit Kumar,Purabi Saikia,Nikhil Lele,Arvind Chandra Pandey,Parul Srivastava,Bimal Kumar Bhattacharya,Mohamed Latif Khan 국립중앙과학관 2020 Journal of Asia-Pacific Biodiversity Vol.13 No.4

The present study focused on forest type classification and major plant species assemblages in Mudumalaiforest region using Airborne Visible/Infrared Imaging Spectrometer Next Generation. The phytosociologicalanalysis exhibited a total of 657 individuals (1095 individuals ha-1) of 24 tree speciesbelonging to 22 genera and 18 families. The highest tree density was contributed by Tectona grandis (132individuals ha-1 and 12.05% of total tree density) followed by Anogeissus latifolia (105 individuals ha-1 and9.59% of total tree density). The support vector machine study showed the dominance of SouthernTropical Semi-Evergreen forests (31%) followed by Southern Tropical moist deciduous forests (26.7%) andSouthern Tropical dry deciduous forests (24.8%) with a very high accuracy (92.37%). The comparativeanalysis of the existing forest types with Champion and Seth’s (1968) classification of forests exhibited achange of 30% in forest types in terms of their structure, composition, and extent over a period of 50years. The spectral angle mapperebased study emphasized the defining role of elevation, rainfall, andtemperature in species distribution, and physiognomy with dominance of A. latifolia (w19.22%). Thestudy implies the high spectral fidelity of airborne images for forest type mapping and plant speciesdiscrimination in tropical forests.