Lalit Kumar

Impact of sintering temperature on structural, optical and ferroelectric properties of V-doped ZnO

This paper reports the effect of sintering temperature on the structural, optical and ferroelectric properties of vanadium (V) doped zinc oxide (ZnO) samples. X-ray diffraction (XRD) study confirms the formation of a hexagonal wurtzite phase. It has been found that the increase in sintering temperature leads to very small enhancement in lattice parameters as well as in grain sizes. The presence of E2 (high) modes in Raman spectra of V-doped ZnO indicate the stability of the wurtzite structure of ZnO, consistent with the XRD results. The optical band gap estimated from UV–Vis spectroscopy reveals the reduction in band gap of ZnO. Furthermore, changes in ferroelectric polarizations are also observed with an increase in the sintering temperature. The above results are understood based on the increased crystallinity and the presence of mixed phases of the samples with sintering temperature.

Opinion Dynamics Through Natural Phenomenon of Grain Growth and Population Migration

Opinion dynamics has witnessed a colossal interest in research and development activity aimed at the realization of intelligent systems facilitating the understanding and prediction of these. Many nature-inspired phenomena have been used for modelling and investigation of opinion formation. One of the prominent models based on the concept of ferromagnetism is the Ising model in statistical mechanics. The model represents magnetic dipole moments of atomic spins, which can exist in any one of two states, +1 or −1. We have used NetLogo to simulate the Ising model and correlated the results with opinion dynamics within its purview. For the first time, the grain growth phenomenon has been investigated to analyze opinion dynamics. We have also modelled natural phenomena of population growth using rigorous mathematics and corroborated the results with opinion dynamics. The results substantiate the potential use of such nature-inspired phenomena that encompass an ensemble large enough to be investigated and correlated with the real world, in terms of the involvement of numerous actors/agents participating in the process of opinion formation.

A unique complication of self-expandable metal stent placement in malignant duodenal obstruction

Abstract Intestinal obstruction is a common complication in patients with advanced gastrointestinal malignancies. In the last two decades, endoscopic placement of duodenal stents has become a mainstay of palliative treatment in patients with unresectable obstructive duodenal pathology. Self-expandable metal stents have been reported to have excellent success rates, besides dramatically improve the patient’s quality of life by reinstating the oral feeding ability. Re-intervention rates remain high, commonly as a consequence of tumour ingrowth resulting stent occlusion. We describe a unique case of duodenal stent obstruction secondary to impacted gallstones. To the best of our knowledge, this is the first case described in the literature and should alert clinicians to this unusual complication.

A REVIEW ON PHARMACOGNOSTIC STUDY OF BUTEA MONOSPERMA

The plant Butea monosperma is a wonderful medicinal plant with lots of uses. The plant is used for many therapeutic properties like astringent, anti diarrheal activity, anti-implantation activities, etc. Due to different pharmacological effects, intense studies have been done on it s chemical constituents. It is called as the ‘Flame of Forest’ due to its look. The flowers look like fire and therefore considered as a form of Agnidev (God of Fire). Mostly found in the greater parts of India, and less found in the arid regions. It is known by different names according to the region or place in which it is found. Its gum is called as Bengal Kino or Butea Gum and is used for many purposes. Other parts of the plant are well known for different uses and this article is all about the wonderfulness of Butea monosperma.

Surface Structure-Dependent Low Turn-On Electron Field Emission from Polypyrrole/Tin Oxide Hybrid Cathodes

We present a new surface structure-dependent cold cathode material capable of sustaining high electron emission current suitable for next-generation low turn-on field-emission devices. The low turn-on electric field for electron emission in the cathode materials is critical, which facilitates the low-power room-temperature operation, a key factor required by the industrial sector. We demonstrate the facile synthesis of polypyrrole (PPy)/tin oxide (SnO2)-based core–shell hybrid cold cathode materials for large area applications. The technique used here is based on a simple and economical method of surfactant-mediated polymerization. The coupled investigation of X-ray diffraction along with electron microscopy reveals the formation of rutile phase SnO2 nanoparticles of size ∼15 nm. These SnO2 nanoparticles act as nucleation sites for the growth of PPy nanofibers, resulting in encapsulated SnO2 nanoparticles in the PPy amorphous matrix. The coupling of spherical-shaped core–shell structures of PPy/SnO2 resulted into the particle train-like nanostructured form of the hybrid material. These core–shell structures formed the local p–n junction between the n-type SnO2 (core) and p-type PPy (shell). The long chains of these p–n junctions in nanofibers result in the modification of the electronic band structure of PPy, leading to a reduction in the work function of the electrons. The significant surface structural modification in PPy/SnO2 causes a prominent reduction in the turn-on electric field for electron emission in PPy/SnO2 nanocomposite (∼1.5 V/μm) as compared to the pure PPy (∼3.3 V/μm) without significant loss in current density (∼1 mA/cm2). The mechanism of improved field-emission behavior and advantages of using such hybrid nanomaterials as compared to other composite nanomaterials have also been discussed in detail.

Gold nanoparticles prepared by electro-exploding wire technique in aqueous solutions

This article presents an effective approach for the synthesis of Au nanoparticles via an environmentally benevolent electro-exploding wire (EEW) technique. In this process, Au nanoparticles evolve through the plasma generated from the parent Au metal. Compared to other typical chemical methods, electro-exploding wire technique is a simple and economical technique which normally operates in water or organic liquids under ambient conditions. Efficient size control was achieved using different aqueous medium like (1mM) NaCl, deionized water and aqueous solution of sodium hydroxide (NaOH, pH 9.5) using identical electro-exploding conditions. The gold nanoparticles exhibited the UV-vis absorption spectrum with a maximum absorption band at 530u2005nm, similar to that of gold nanoparticles chemically prepared in a solution. The mechanism of size variation of Au nanoparticles is also proposed. The results obtained help to develop methodologies for the control of EEW based nanoparticle growth and the functionalization...

Fabrication of PANI/ZnO heterojunction

In the present work we report formation of a junction between ZnO and Polyaniline. This Organic/Inorganic junction has shown diode like characteristics with low rectification ratio. ZnO/PANI hybrid structure is highly desirable because both materials are of low cost and are easy to synthesize. The direct growth of ZnO on the conductive polymer is still limited. In this work, PANI is synthesized by electrochemical deposition and on top of it ZnO film is deposited by r.f. sputtering.