Biphenyl ethers conjugated CdSe/ZnS core/shell quantum dots and interpretation of the mechanism of amyloid fibril disruption

The biphenyl ethers (BPEs) are the potent inhibitors of TTR fibril formation and are efficient fibril disrupter. However, the mechanism by which the fibril disruption occurs is yet to be fully elucidated. To gain insight into the mechanism, we synthesized and used a new QD labeled BPE to track the process of fibril disruption. Our studies showed that the new BPE-QDs bind to the fiber uniformly and has affinity and specificity for TTR fiber and disrupted the pre-formed fiber at a relatively slow rate. Based on these studies we put forth the probable mechanism of fiber disruption by BPEs. Also, we show here that the BPE-QDs interact with high affinity to the amyloids of A beta(42), lysozyme and insulin. The potential of BPE-QDs in the detection of senile plaque in the brain of transgenic Alzheimer's mice has also been explored. (C) 2010 Elsevier Ltd. All rights reserved.

A soluble random-matrix model for relaxation in quantum systems

We study the relaxation of a degenerate two-level system interacting with a heat bath, assuming a random-matrix model for the system-bath interaction. For times larger than the duration of a collision and smaller than the Poincaré recurrence time, the survival probability of still finding the system at timet in the same state in which it was prepared att=0 is exactly calculated.

Completeness of the Coulomb wave functions in quantum mechanics

We give an explicit, direct, and fairly elementary proof that the radial energy eigenfunctions for the hydrogen atom in quantum mechanics, bound and scattering states included, form a complete set. The proof uses only some properties of the confluent hypergeometric functions and the Cauchy residue theorem from analytic function theory; therefore it would form useful supplementary reading for a graduate course on quantum mechanics.

On the two-dimensional thermoelectric power in quantum wells of non-parabolic materials under magnetic quantization

We present a simplified theoretical formulation of the thermoelectric power (TP) under magnetic quantization in quantum wells (QWs) of nonlinear optical materials on the basis of a newly formulated magneto-dispersion law. We consider the anisotropies in the effective electron masses and the spin-orbit constants within the framework of k.p formalism by incorporating the influence of the crystal field splitting. The corresponding results for III-V materials form a special case of our generalized analysis under certain limiting conditions. The TP in QWs of Bismuth, II-VI, IV-VI and stressed materials has been studied by formulating appropriate electron magneto-dispersion laws. We also address the fact that the TP exhibits composite oscillations with a varying quantizing magnetic field in QWs of n-Cd3As2, n-CdGeAs2, n-InSb, p-CdS, stressed InSb, PbTe and Bismuth. This reflects the combined signatures of magnetic and spatial quantizations of the carriers in such structures. The TP also decreases with increasing electron statistics and under the condition of non-degeneracy, all the results as derived in this paper get transformed into the well-known classical equation of TP and thus confirming the compatibility test. We have also suggested an experimental method of determining the elastic constants in such systems with arbitrary carrier energy spectra from the known value of the TP. (C) 2010 Elsevier Ltd. All rights reserved.

Controlled photoluminescence from self-assembled semiconductor-metal quantum dot hybrid array films

Thin films of hybrid arrays of cadmium selenide quantum dots and polymer grafted gold nanoparticles have been prepared using a BCP template. Controlling the dispersion and location of the respective nanoparticles allows us to tune the exciton-plasmon interaction in such hybrid arrays and hence control their optical properties. The observed photoluminescence of the hybrid array films is interpreted in terms of the dispersion and location of the gold nanoparticles and quantum dots in the block copolymer matrix.

Droplet Epitaxy of InN Quantum Dots on Si(111) by RF Plasma-Assisted Molecular Beam Epitaxy

InN quantum dots (QDs) were fabricated on Si(111) substrate by droplet epitaxy using an RF plasma-assisted MBE system. Variation of the growth parameters, such as growth temperature and deposition time, allowed us to control the characteristic size and density of the QDs. As the growth temperature was increased from 100 C to 300 degrees C, an enlargement of QD size and a drop in dot density were observed, which was led by the limitation of surface diffusion of adatoms with the limited thermal energy. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to assess the QDs size and density. The chemical bonding configurations of InN QDs were examined by X-ray photo-electron spectroscopy (XPS). Fourier transform infrared (FTIR) spectrum of the deposited InN QDs shows the presence of In-N bond. Temperature-dependent photoluminescence (PL) measurements showed that the emission peak energies of the InN QDs are sensitive to temperature and show a strong peak emission at 0.79 eV.

Search on a hypercubic lattice using a quantum random walk. I. d > 2

Random walks describe diffusion processes, where movement at every time step is restricted to only the neighboring locations. We construct a quantum random walk algorithm, based on discretization of the Dirac evolution operator inspired by staggered lattice fermions. We use it to investigate the spatial search problem, that is, to find a marked vertex on a d-dimensional hypercubic lattice. The restriction on movement hardly matters for d > 2, and scaling behavior close to Grover's optimal algorithm (which has no restriction on movement) can be achieved. Using numerical simulations, we optimize the proportionality constants of the scaling behavior, and demonstrate the approach to that for Grover's algorithm (equivalent to the mean-field theory or the d -> infinity limit). In particular, the scaling behavior for d = 3 is only about 25% higher than the optimal d -> infinity value.

Search on a hypercubic lattice using a quantum random walk. II. d = 2

We investigate the spatial search problem on the two-dimensional square lattice, using the Dirac evolution operator discretized according to the staggered lattice fermion formalism. d = 2 is the critical dimension for the spatial search problem, where infrared divergence of the evolution operator leads to logarithmic factors in the scaling behavior. As a result, the construction used in our accompanying article A. Patel and M. A. Rahaman, Phys. Rev. A 82, 032330 (2010)] provides an O(root N ln N) algorithm, which is not optimal. The scaling behavior can be improved to O(root N ln N) by cleverly controlling the massless Dirac evolution operator by an ancilla qubit, as proposed by Tulsi Phys. Rev. A 78, 012310 (2008)]. We reinterpret the ancilla control as introduction of an effective mass at the marked vertex, and optimize the proportionality constants of the scaling behavior of the algorithm by numerically tuning the parameters.

A Compact Model incorporating Quantum Effects for Ultra-Thin-Body Double-Gate MOSFETs

We propose a compact model which predicts the channel charge density and the drain current which match quite closely with the numerical solution obtained from the Full-Band structure approach. We show that, with this compact model, the channel charge density can be predicted by taking the capacitance based on the physical oxide thickness, as opposed to C-eff, which needs to be taken when using the classical solution.

Effects of Parasitics and Interface Traps on Ballistic Nanowire FET in the Ultimate Quantum Capacitance Limit

In this paper, we focus on the performance of a nanowire field-effect transistor in the ultimate quantum capacitance limit (UQCL) (where only one subband is occupied) in the presence of interface traps (D-it), parasitic capacitance (C-L), and source/drain series resistance (R-s,R-d), using a ballistic transport model and compare the performance with its classical capacitance limit (CCL) counterpart. We discuss four different aspects relevant to the present scenario, namely: 1) gate capacitance; 2) drain-current saturation; 3) subthreshold slope; and 4) scaling performance. To gain physical insights into these effects, we also develop a set of semianalytical equations. The key observations are as follows: 1) A strongly energy-quantized nanowire shows nonmonotonic multiple-peak C-V characteristics due to discrete contributions from individual subbands; 2) the ballistic drain current saturates better in the UQCL than in the CCL, both in the presence and absence of D-it and R-s,R-d; 3) the subthreshold slope does not suffer any relative degradation in the UQCL compared to the CCL, even with Dit and R-s,R-d; 4) the UQCL scaling outperforms the CCL in the ideal condition; and 5) the UQCL scaling is more immune to R-s,R-d, but the presence of D-it and C-L significantly degrades the scaling advantages in the UQCL.

Scaling theory of quantum resistance distributions in disordered systems

We have derived explicitly, the large scale distribution of quantum Ohmic resistance of a disordered one-dimensional conductor. We show that in the thermodynamic limit this distribution is characterized by two independent parameters for strong disorder, leading to a two-parameter scaling theory of localization. Only in the limit of weak disorder we recover single parameter scaling, consistent with existing theoretical treatments.

Analytical modeling of quantum threshold voltage for triple gate MOSFET

In this work a physically based analytical quantum threshold voltage model for the triple gate long channel metal oxide semiconductor field effect transistor is developed The proposed model is based on the analytical solution of two-dimensional Poisson and two-dimensional Schrodinger equation Proposed model is extended for short channel devices by including semi-empirical correction The impact of effective mass variation with film thicknesses is also discussed using the proposed model All models are fully validated against the professional numerical device simulator for a wide range of device geometries (C) 2010 Elsevier Ltd All rights reserved

Descriptions of operators in quantum mechanics

The problem of expressing a general dynamical variable in quantum mechanics as a function of a primitive set of operators is studied from several points of view. In the context of the Heisenberg commutation relation, the Weyl representation for operators and a new Fourier-Mellin representation are related to the Heisenberg group and the groupSL(2,R) respectively. The description of unitary transformations via generating functions is analysed in detail. The relation between functions and ordered functions of noncommuting operators is discussed, and results closely paralleling classical results are obtained.

Wigner distribution for angle coordinates in quantum mechanics

The method of Wigner distribution functions, and the Weyl correspondence between quantum and classical variables, are extended from the usual kind of canonically conjugate position and momentum operators to the case of an angle and angular momentum operator pair. The sense in which one has a description of quantum mechanics using classical phase‐space language is much clarified by this extension.

Patterning Nanoroads and Quantum Dots on Fluorinated Graphene

Using ab initio methods we have investigated the fluorination of graphene and find that different stoichiometric phases can be formed without a nucleation barrier, with the complete “2D-Teflon” CF phase being thermodynamically most stable. The fluorinated graphene is an insulator and turns out to be a perfect matrix-host for patterning nanoroads and quantum dots of pristine graphene. The electronic and magnetic properties of the nanoroads can be tuned by varying the edge orientation and width. The energy gaps between the highest occupied and lowest unoccupied molecular orbitals (HOMO-LUMO) of quantum dots are size-dependent and show a confinement typical of Dirac fermions. Furthermore, we study the effect of different basic coverage of F on graphene (with stoichiometries CF and C4F) on the band gaps, and show the suitability of these materials to host quantum dots of graphene with unique electronic properties.