Observation of Mixed Alkali Like Behaviour by Fluorine Ion in Mixed Alkali Oxyfluro Vanadate Glasses: Analysis from Conductivity Measurements

In this communication we report the fluorine ion dynamics in mixed alkali oxyfluro vanadate glasses. We have measured the electrical conductivity using impedance spectroscopy technique Room temperature conductivity falls to 5 orders of magnitude from its single alkali values at 33 mol% of rubidium concentration. We have also estimated the distance between similar mobile ions using the density values. Assuming this distance as the hopping distance between the similar ions we have estimated the anionic (Fluorine ion in our case) conductivity. It is observed that the fluorine ion dynamics mimics the mixed alkali effect and scales as the onset frequency f0.Comment: submitted to DAE-SSDP 2018 Indi

Charge Transport and Photo-Physical Studies in Conjugated Polymers, Hybrid Nanocomposites and Devices

The main motivation of this thesis is derived from the fact that physics of disordered systems like conjugated polymer has yet not achieved as concrete understanding as ordered and crystalline systems such as inorganic semiconductors. Through the work done in this thesis, several efforts have been made in order to understand basic charge transport (hopping, current injection) phenomena and photo-physical properties (photoluminescence quenching, absorption, photoconductivity) in conjugated polymer and their hybrid composites. The thesis consists of 7 chapters. Chapter 1 discusses the background knowledge and information of the general properties of conjugated polymers, quantum dots and their hybrid nanocomposites. Chapter 2 deals with the sample preparation and experimental techniques used in this thesis. Chapter 3 elaborates the temperature and field dependent anisotropic charge transport in polypyrrole. Chapter 4 presents an idea to probe and correlate disorder and transport properties using impedance and Raman spectroscopy. Chapter 5 mainly talks about the doping level dependent photophysical and electrical properties of poly(3-hexylthiophene). Chapter 6 reveals the charge transport phenomena in hybrid composites of poly(3,4-ethyldioxythiophene):polysterene sulfonate (PEDOT:PSS) and cadmium telluride quantum dots. Chapter 1: Conjugated polymers and their hybrid systems are easily processible and cost effective material having huge scope for advanced materials of the future. Although variable range hopping (VRH) is widely accepted to model charge transport in π-conjugated systems, but at very low temperatures, high fields, high carrier concentrations one need to explore other models. Conjugated polymers are anisotropic intrinsically. Therefore, anisotropic charge transport can provide basic insights about the physics of charge hopping. Quantum dots, and their hybrid nanocomposites with semiconducting polymers receiving a huge attention for light emission and photovoltaic purposes. It is important to learn about the charge injection,barrier heights, etc. in order to achieve efficient hybrid devices. Chapter 2: Synthesis of the samples, both conjugated polymers and quantum dots, and fabrication of hybrid devices is an important and integral part of this thesis. An Electropolymerization technique is used for making polymer samples on conducting substrates. This is quite interesting because one can tune doping level, disorder and thickness simultaneously. Hydrothermal process is adopted to get highly aqua-dispersible quantum dots. Samples are characterized by different techniques like Raman spectroscopy, energy dispersive spectroscopy. Photoluminescence, UV-Vis absorption, transmission electron microscopy and atomic force microscopy are used to explore several properties of the polymer and hybrid nanocomposites. Chapter 3: It is known that conjugated polymers are intrinsically one–dimensional materials. Therefore it is important to learn anisotropic behavior of these complex systems. Hence, a comparison of electronic transport to their morphology has been carried out and role of carrier density and disorder is discussed further. Both in-plane and out-of-plane charge transport is studied in electrochemically deposited polypyrrole on platinum. Strong anisotropy is observed in the system which is correlated to granular morphology. Field dependence of anisotropic conductivity is also explored. Field scaling analysis shows that all field dependent curves of conductance at different temperatures can fall on to single master curve. Glazman – Matveev model is used to describe nonlinear conduction in field dependence and nonlinearity exponent is estimated. Disorder and carrier density along with the morphological structure like length and orientation of polymer chains with stacking arrangement of different layers in PPy films play an important role in governing the anisotropy in transport properties. Chapter 4: Two different techniques, namely impedance and Raman spectroscopies are used to probe disorder and transport properties in the polypyrrole. An effort is made to correlate the transport properties to the morphology by probing disorder via two different spectroscopic techniques. Frequency dependence of both real and imaginary part has shown that disorder and inhomogeneity varies in different PPy devices, which thus affect the transport properties like conductivity and mobility. Mobility values along the thickness direction for each sample reveal the impact of disorder on out-of¬plane geometry. A circuit based on consideration of the distributed relaxation times, is successfully used to obtain the best fit for the Cole–Cole plot of various PPy devices. FWHM of the de-convoluted peaks of Raman spectra is attributed to the change in distribution of the conjugation length in the PPy films. Chapter 5: The main focus of this chapter is the qualitative exploration of different photo-physical and electrical properties of electropolymerized poly(3-hexylthiophene) and their dependence on doping level. Photoluminescence quenching, band edge shifting in absorption spectra, electrochromic effect, significant enhancement in photocurrent at optimum doping level, two relaxation behaviors in reactance spectra and presence of negative capacitance at low frequencies are distinct features which are observed in poly(3-hexylthiophene) in this work. Quenching in photoluminescence intensity is attributed to charge transfer occurring between polymer chains and dopant ions. Two semicircles in the Cole-Cole plots refer to two type of relaxation process occurring in bulk layer and at interface. Frequency response of capacitance at higher bias and lo side of frequency shows a negative capacitance due to the relaxation mechanism associated with the space-charge effect. Chapter 6: Synthesis of quantum dots and fabrication of hybrid devices is one of the catchy parts of this chapter. Huge quenching photoluminescence intensity and very high increment (~ 400 %) in photocurrent clearly depict the charge transfer at molecular level. Temperature dependent current–voltage characteristics show the absence of thermionic emission since the barrier height is more than the thermal energy of the carriers. Further analysis confirms that the charge carrier injection of ITO/PPCdTe3/Al device is controlled by tunneling processes. The hybrid system has shown a peculiar transition from direct tunneling to Fowler–Nordheim tunneling mechanism which is because of the change in shape of the barrier height from trapezoidal to triangular type with increase in applied electric field. Chapter 7: The conclusions of the different works presented in this thesis are coherently summarized in this thesis. Thoughts and prospective for future directions are also summed up

A RAPID VALIDATED UNI-DIMENSIONAL DOUBLE DEVELOPMENT HPTLC-DENSITOMETRY METHOD FOR SIMULTANEOUS ESTIMATION OF METFORMIN HYDROCHLORIDE, GLICLAZIDE AND PIOGLITAZONE HYDROCHLORIDE

Objective: To develop and validate a uni-dimensional double development high-performance thin layer chromatography (UDDD-HPTLC) for estimation of anti-diabetic medicine compromising of metformin (MET) gliclazide (GLZ) and pioglitazone hydrochloride (PIO). Methods: The chromatographic separation of these drugs was carried out on precoated TLC plates silica gel 60F254by two mobile phases consisting of Ammonium Sulphate: Methanol: Acetonitrile: Water (4:3:2:1) for MET and PIO and Toluene: Ethyl Acetate: Formic Acid (6:4:0.5) for GLZ respectively for ideal separation and good resolution. The densitometric detection and quantification were carried out at 237 nm for MET and 200 nm for GLZ and PIO. The validation parameters were strictly followed as per the ICH guidelines. Results: The linearity range was obtained at 3000-8000ng/spot, 360-960 ng/spot, 90-240 ng/spot for MET, GLZ and PIO with r2value>0.999. The other parameters such as precision, reproducibility, robustness were efficiently obtained within the limits. The proposed method was successfully applied for simultaneous determination of MET, GLZ and PIO in the commercial formulation. Conclusion: In simultaneous estimation, the different polarity of drugs makes it more cumbersome to develop and validate any chromatographic method. In the present study, a uni-dimensional double development high-performance thin layer chromatography (UDDD-HPTLC) for estimation of these drugs have been developed and validated to resolve the estimation problem. It is an effortless and speedy method which was developed and validated using ICH guidelines. The developed and validated method using ICH guidelines is effortless and speedy technique

Comparative Study of Networking Protocols in WSN Implementation for Greenhouse Monitoring

Wireless sensor networks consist of number of small devices called sensor nodes formed by combining a sensing unit, processor unit, wireless communication unit and power source unit. WSN has gained a lot of importance in recent years because of its use in various fields where monitoring and controlling are important aspects. This paper discusses implementation of wireless sensor network in greenhouse for the growth of crop yields. Wireless sensor networkcan use various types of networking protocols for implementing WSN in greenhouse monitoring.Main focus of this paper is on comparative study of various networking protocols available for implementing WSN

Multifocal myoclonus as a presentation of levetiracetam toxicity.

BACKGROUND: Levetiracetam (LEV) is widely used for treatment of focal and myoclonic seizures, but reports of LEV toxicity are scarce. Here, we report a rare case of multifocal myoclonus due to LEV toxicity in a patient with chronic renal insufficiency. CASE PRESENTATION: A 52-year-old woman with history of chronic kidney disease was admitted to the ICU for sedation and intubation after a cardiac arrest. She developed nonconvulsive status epilepticus that resolved after administration of propofol while receiving LEV 1500 mg twice a day. After holding the propofol infusion, the patient started having multifocal myoclonic jerks, documented on video-EEG recordings with a supratherapeutic level of LEV. After discontinuation of LEV, the myoclonus resolved. CONCLUSION: This is a unique manifestation of LEV toxicity, which has been scarce in the literature. It suggests an inverted U-shaped dose–response of the antimyoclonic effect of LEV

Throughput Maximization of Cognitive Radio Multi Relay Network with Interference Management

In this paper, an Orthogonal Frequency Division Multiplexing (OFDM) based cognitive multi relay network is investigated to maximize the transmission rate of the cognitive radio (CR) with enhanced  fairness among CR users  with interference to the primary users (PUs) being managed below a certain threshold level. In order to improve the transmission rate of the CR, optimization of the subcarrier pairing and power allocation is to be carried out simultaneously. Firstly joint optimization problem is formulated and Composite Genetic and Ordered Subcarrier Pairing (CGOSP) algorithm is proposed to solve the problem. The motivation behind merging genetic and OSP algorithm is to reduce the complexity of Genetic Algorithm (GA). Further, to have a fair allocation of resources among CR users, the Round Robin allocation method is adopted so as to allocate subcarrier pairs to relays efficiently. The degree of fairness of the system is calculated using Jain’s Fairness Index (JFI). Simulation results demonstrate the significant improvement in transmission rate of the CR, low computational complexity and enhanced fairness

STUDY OF TWACHA SHARIR WITH SPECIAL REFERENCE TO CHARAKOKTA CHATURTHA STHARIYA (FOURTH LAYER) DADRU VYADHI

Twacha (skin) is one of the important Dnyanendriya (sense organ) which covers all other Indriyas and whole body. There are many doubts and unknown things regarding Ayurvedokta Twacha. Charaka has described six layers and the corresponding diseases of that layer of the Twacha. Out of these, the fourth layer is the seat of manifestation of Dadru Vyadhi. Also signs and symptoms of Dadru shows similarities with the signs and symptoms of tinea infection according to modern science. Hence to simplify above described terminologies regarding Twacha present study was carried out. 30 patients having signs and symptoms of Dadru were selected to rule out whether there is any extent of Dadru Vyadhi other than fourth layer with the help of skin biopsy. Also to establish relation between Dadru and likewise disease tinea infection of fourth layer i.e. stratum and to study anatomico-physiological changes in skin layers in Dadru Vyadhi with the help of histopathological study. From the present work done it was observed that the anatomico-physiological changes were found upto the fourth layer of skin which Charaka has already stated. Most of the signs and symptoms of Dadru patients found similar to tinea corporis infection which demonstrate the relation between Dadru and tinea infection