Aggregation Behavior of pHLIP in Aqueous Solution at Low Concentrations: A Fluorescence Study

pH (low) insertion peptide (pHLIP) is a 36-residue peptide derived from the third transmembrane helix of the membrane protein bacteriorhodopsin. The hydrophobicity of this peptide makes it prone to aggregation even at low concentrations, but this has not been studied in detail. In this work, we characterized monomeric and aggregated forms of pHLIP in aqueous solution (pH 8) at low concentrations (~μM) using fluorescence-based approaches, complemented by circular dichroism (CD) spectroscopy. We show here that monomeric and aggregated pHLIP display differential red edge excitation shift (REES) and CD spectra. These spectroscopic features allowed us to show that pHLIP aggregates even at low concentrations. A detailed knowledge of the aggregation behavior of pHLIP under these conditions will be useful for monitoring and quantifying its interaction with membranes.     

Electronic structure and optical properties of CuAlO2 under biaxial strain

An ab initio calculation has been carried out to investigate the biaxial strain ( - 10.71% < ε < 9.13%) effect on elastic, electronic and optical properties of CuAlO(2). All the elastic constants (c(11), c(12), c(13), c(33)) except c(44) decrease (increase) during tensile (compressive) strain. The band gap is found to decrease in the presence of tensile as well as compressive strain. The relative decrease of the band gap is asymmetric with respect to the sign of the strain. Significant differences between the parallel and perpendicular components of the dielectric constant and the optical properties have been observed due to anisotropic crystal structure. It is further noticed that these properties are easily tunable by strain. Importantly, the collective oscillation of the valence electrons has been identified for light polarized perpendicular to the c-axis. From calculations, it is clear that the tensile strain can enhance the hole mobility as well as the transparency of CuAlO(2).     

Investigation of Noise-Induced Escape Rate: A Quantum Mechanical Approach

A quantum system coupled to a heat-bath in non-equilibrium environment is considered to study the problem of noise-induced escape rate from a metastable state in the moderate to strong friction limit (Kramers’ regime). It is known that starting from an initial coherent state representation of bath oscillators, one can derive a c-number generalized quantum Langevin equation where the quantum correction terms appear as a coupled infinite set of hierarchy of equations. For practical purpose, one should truncate these equations after a certain order. In our present development, we calculate the quantum correction terms in a closed analytical form based on a systematic perturbation technique and then derive the lowest order quantum correction factor exactly in the case of an Ohmic dissipative bath. Finally, to demonstrate its applicability, the effective equation of motions has been used to study the barrier crossing dynamics which incorporates the quantum correction factors.     

Production and Storage of Energy with One-Dimensional Semiconductor Nanostructures

This article outlines state-of-the-art energy technologies, including production and storage, available to us through semiconductor nanomaterials. The nanostructure growth processes have been illustrated in detail, with emphasis on the latest developments in hierarchical and radial-composition modulated nanostructures. On the energy efficiency and generation part, light-emitting diodes, photovoltaics, photoelectrochemistry, thermoelectric, and fuel cells have been discussed. In the energy storage part, supercapacitors and lithium batteries have been discussed.     

Low-macroscopic field emission from nanocrystalline Al doped SnO<Subscript>2</Subscript> thin films synthesized by sol–gel technique

We have observed low-macroscopic field electron emission from wide bandgap nanocrystalline Al doped SnO₂ thin films deposited on glass substrates. The emission properties have been studied for different anode-sample spacings and for different Al concentrations in the films. The turn-on field and approximate work function were calculated and we have tried to explain the emission mechanism from this. The turn-on field was found to vary in the range 5.6–7.5 V/μm for a variation of anode sample spacing from 80–120 μm. The turn-on field was also found to vary from 4.6–5.68 V/μm for a fixed anode-sample separation of 80 μm with a variation of Al concentration in the films 8.16–2.31%. The Al concentrations in the films have been measured by energy dispersive X-ray analysis. Optical transmittance measurement of the films showed a high transparency with a direct bandgap ∼3.98 eV. Due to the wide bandgap, the electron affinity of the film decreased. This, along with the nanocrystalline nature of the films, enhanced the field emission properties. PACS 81.20.Fw; 61.10.-i; 79.70.+q     

Observation of enhanced two-photon absorption in ZnS quantum dots at an ultraviolet wavelength

Two-photon absorption(2PA) in zinc sulphide(ZnS) and Mn2+-doped ZnS quantum dots is reported by the z-scan technique,with nanosecond pulsed laser radiation at 355 nm.The observed values of the 2PA cross section of all the samples are 105 times larger than that of bulk ZnS.     

Propagation of arbitrary initial wave packets in a quantum parametric oscillator: Instability zones for higher order moments

We consider the dynamics of a particle in a parametric oscillator with a view to exploring any quantum feature of the initial wave packet that shows divergent (in time) behaviour for parameter values where the classical motion dynamics of the mean position is bounded. We use Ehrenfest's theorem to explore the dynamics of nth order moment which reduces exactly to a linear non autonomous differential equation of order $n+1$. It is found that while the width and skewness of the packet is unbounded exactly in the zones where the classical motion is unbounded, the kurtosis of an initially non-gaussian wave packet can become infinitely large in certain additional zones. This implies that the shape of the wave packet can change drastically with time in these zones.     

Noise Stability of SIS Receivers

There is a strong interest in the submillimeter astronomy community to increase the IF bandwidth of SIS receivers in order to better facilitate broad spectral linewidth and continuum observations of extragalactic sources. However, with an increase in receiver IF bandwidth there is a decrease in the mixer stability. This in turn effects the integration efficiency and quality of the measurement. In order to better understand the noise mechanisms responsible for reducing the receiver stability, we employed a technique first described by D.W. Allan and later elaborated upon by Schieder et al. In this paper we address a variety of factors that degrade the noise stability of SIS receivers. The goal of this exercise is to make recommendations aimed at maximizing SIS receiver stability.     

Stability of thin film flowing down the outer surface of a rotating non-uniformly heated vertical cylinder

Nonlinear Dynamics - We investigated an incompressible viscous liquid film flow over a rotating vertical cylinder of radius R and of infinite length rotating with a uniform angular velocity...     

On the magnetic anisotropy of CuO

The anisotropy of the magnetic susceptibility of CuO has been measured. In both, the paramagnetic and the antiferromagnetic state the susceptibility can be described to a good approximation by