Andreev reflection near the Dirac point at Graphene - NbSe2 junction

Despite extensive search for about a decade, specular Andreev reflection is only recently realized in bilayer graphene-superconductor interface. However, the evolution from the typical retro type Andreev reflection to the unique specular Andreev reflection in single layer graphene has not yet been observed. We investigate this transition by measuring the differential conductance at the van der Walls interface of single layer graphene and NbSe2 superconductor. We find that the normalized conductance becomes suppressed as we pass through the Dirac cone via tuning the Fermi level and bias energy, which manifests the transition from retro to non-retro type Andreev reflection. The suppression indicates the blockage of Andreev reflection beyond a critical angle of the incident electron with respect to the normal between the single layer graphene and the superconductor junction. The results are compared with a theoretical model of the corresponding setup

Rheological behavior of clay water slurry in the presence of cationic surfactants and Electrolytes

The rheological properties have been studied in the presence of different additives like surfactant and electrolyte. The effect of solid concentration in bentonite-water slurry was studied. Without any additives bentonite-clay suspension behaved as a rheopectic fluid and its viscosity increased with clay concentration and time at constant shear rate. The addition of electrolytes like NaCl, Na2SO4, CaCl2 were altered the rheological properties of clay-water suspension. It was found that viscosity decreases with electrolyte concentration. The effect of cationic cetyl trimethyl ammonium bromide (CTAB) on the rheological behaviors of bentonite-water slurry was also investigated. For CTAB initially viscosity decreased with concentration, then increased till a certain value and after that viscosity decreased. The combined effect of both electrolyte and CTAB at different concentration of each was also studied. These combinations had more reducing effect on viscosity than each of the individuals’ effect on slurry viscosity. The zeta-potential values of bentonite water slurry at different pH and in the presence of different concentration of CTAB were studied. All the experiments were carried out at 30oC using a water circulato

Enhanced Specular Andreev reflection in bilayer graphene

Andreev reflection in graphene is special since it can be of two types- retro or specular. Specular Andreev reflection (SAR) dominates when the position of the Fermi energy in graphene is comparable to or smaller than the superconducting gap. Bilayer graphene (BLG) is an ideal candidate to observe the crossover from retro to specular since the Fermi energy broadening near the Dirac point is much weaker compared to monolayer graphene. Recently, the observation of signatures of SAR in BLG have been reported experimentally by looking at the enhancement of conductance at finite bias near the Dirac point. However, the signatures were not very pronounced possibly due to the participation of normal quasi-particles at bias energies close to the superconducting gap. Here, we propose a scheme to observe the features of enhanced SAR even at zero bias at a normal metal (NM)-superconductor (SC) junction on BLG. Our scheme involves applying a Zeeman field to the NM side of the NM-SC junction on BLG (making the NM ferromagnetic), which energetically separates the Dirac points for up-spin and down-spin. We calculate the conductance as a function of chemical potential and bias within the superconducting gap and show that well-defined regions of specular- and retro-type Andreev reflection exist. We compare the results with and without superconductivity. We also investigate the possibility of the formation of a p-n junction at the interface between the NM and SC due to a work function mismatch.Comment: 9 pages, 10 captioned figures. Published versio

Bu4N(+) Alkoxide-Initiated/Autocatalytic Addition Reactions with Organotrimethylsilanes.

The use of Me3SiO(-)/Bu4N(+) as a general activator of organotrimethylsilanes for addition reactions has been established. The broad scope of the method offers trimethylsilanes (including acetate, allyl, propargyl, benzyl, dithiane, heteroaryl, and aryl derivatives) as bench-stable organometallics that can be readily utilized as carbanion equivalents for synthesis. Reactions are achieved at rt without the requirement of specialized precautions that are commonplace for other organometallics

Emerging evidence on the role of secondary metabolites as nutraceutical

Nutraceuticals have time-honored considerable interest because of their reputed safety, nutritional and therapeutic potential effects. Pharmaceutical and nutritional industries are conscious of the monetary success taking advantage of the more health-seeking consumers. Natural products such as cereals are likely to form the basis of nutraceutical as its revolution represents an enormous opportunity for growth and expansion. Wheat, rice, millets, barley, oat, buckwheat, corn, sorghum, flaxseed psyllium, brown rice, and products are notify the most common cereal based functional foods and nutraceuticals. The nutrients in the cereals have identified prospective for reducing the risk of coronary heart disease, diabetes, tumor incidence, cancer risk, blood pressure, reduces the rate of cholesterol and fat absorption, delaying gastrointestinal emptying and providing gastrointestinal health. Thus, the regular insertion of cereals and their processed products can make a payment to health endorsement and disease avoidance

Time Delay Compensation in Networked Control System

Networked control system is a special type of distributed control system where control loop is enclosed by communication medium. Networked Control System (NCS) suffers from the networked induced delay which may be induced in the forward path as well as in the feedback path. This delay is variable in nature. So if a controller is designed without considering the delays or considering the fixed delay then system performance will be degraded and in the worst case the system become unstable. To compensate the network induced variable transporting delay,a number of methods have been proposed in the literature such as robust control, Smith Predictor and Inteligent control theory. But there are few works reported in literature that employ Linear Quadratic Regulator (LQR) to compensate the networked induced delays.Firstly an LQR controller is designed to compensate the networked induced variable delay which is varied up to a maximum value. Then an LQG controller is designed to compensate the networked induced delay in noisy environment. Here the controller is the same controller used in LQR technique. Only difference between the standard LQR and the LQG controller said now is that it uses Kalman Filter to estimate the plant output using noisy measurement. Then an Model Predictive Controller (MPC) controller is designed using Laguerre network considering the constraints on control input and on the rate of control input. An integrator plant is considered for simulation where the above three controllers are applied. From the simulation result, it is observed that LQR gives a better step response but MPC has better disturbance rejection capacity. To validate the controllers in real-time, an experiment has been conducted in the Labrotory. In the experimental setup using one PC is considered as controller and other one is considered as plant. They are connected through an Ethernet network. From the real time experiment results it is seen that LQR exibits superior delay compensation performance

Development of a self-consistent thermodynamically optimized database along with phase transition experiments in Ni-Mn-Ga system for magnetocaloric applications

Magnetocaloric materials have received significant attention of research community as they can minimize the use of harmful gases (CFCs, HFCs) and render eco-friendly refrigeration. Heusler alloys (Ni2MnGa) are known for their magnetocaloric effects, which make them useful as energy efficient and eco-friendly refrigerating materials. Magnetocaloric properties significantly depend on the composition of these alloys. Ni-Mn-Ga is one of the interesting Heusler systems, which exhibits magnetocaloric properties. In the present study, we performed the thermodynamic optimization of two sub binaries of the Ni-Mn-Ga system: Mn-Ga and Ni-Ga, using CALPHAD approach. A Modified Quasichemical Model (MQM) was used to describe the thermodynamic properties of the liquid solutions in both the binaries. Both the binaries were combined with Mn-Ni to develop a self-consistent thermodynamic database for Ni-Mn-Ga. In order to resolve the existing experimental discrepancies in the Mn-Ga and Ni-Ga system, few alloy compositions were prepared and analyzed using differential thermal analysis. Finally, the developed thermodynamic database was used to calculate the ternary isothermal section of the Ni-Mn-Ga (Heusler alloy) system at 1073 K with a proposed phase region for magnetocaloric applications.Comment: 26 Pages, 10 Figure

Study of Thermo-Sensitive In-Situ Gels for Ocular Delivery

The aim of the present study was the development of thermo-sensitive in-situ gels for in-vitro evaluation of ophthalmic delivery systems of ketorolac tromethamine (KT), based on methylcellulose (MC) in combination with hydroxypropylmethyl cellulose (HPMC). The gel temperature of 1% MC solution was observed at 60°C. It was found that 6% oral rehydration salt without dextrose (ORS) was capable to reduce the gel temperature below physiological temperature. HPMC was added to increase viscosity and drug release time. The results indicated a large increase in viscosity at 37°C with addition of HPMC whch provided sustained release of the drug over a 4h period. From in-vitro release studies, it could be concluded that the developed systems were thus a better alternative to conventional eye drops