Comment on: “Confined states in two-dimensional flat elliptic quantum dots and elliptic quantum wires” [Physica E 11 (2001) 345]

We argue that the two-dimensional elliptic quantum dot problem with finite barrier cannot be exactly solved, contrary to a recent assertion (van den Broek and Peeters, Physica E 11 (2001) 345. We also prove it explicitly by numerically calculating the correct energy spectrum.     

Temperature dependent characteristics of La2O2S: Ln [Ln=Eu, Tb] with various Ln concentrations over 5-60 °C

This research is aimed at developing an optical sensor for remotely measuring human skin temperature in electromagnetically hostile environments, such as within a magnetic resonance imaging (MRI) scanner. In this feasibility study, various concentrations of europium-doped lanthanum oxysulphide (La₂O₂S: Eu—0.1-15 mol% (m/o)) and terbium-doped lanthanum oxysulphide (La₂O₂S: Tb—0.005-50 m/o) have been investigated in terms of crystallinity, photoluminescent (PL) spectral and decay time characteristics. For both phosphors, X-ray diffraction (XRD) has shown that as dopancy increases, the (1 0 0) and (0 0 2) reflections merge and there is a reduction in the c-axis parameter as well as the crystallite size. Photoluminescent characterisation (337 nm excitation) has also shown a dependency to dopant concentration through variance of peak intensity. Temperature dependent decay time measurements were carried out over a low temperature range 5-60 °C. Optimum brightness of these temperature dependent lines is achieved at concentrations of 1 and 10 m/o for La₂O₂S: Eu and La₂O₂S: Tb respectively. However, optimum temperature dependency is achieved at lower concentration for La₂O₂S: Eu, specifically at 0.1 m/o. In comparison to conventional phosphor temperature dependent characteristic, La₂O₂S: Tb showed an increase in decay time with respect to temperature for concentrations above 2 m/o.     

Eigenmodes of triaxial ellipsoidal acoustical cavities with mixed boundary conditions

The linear acoustics problem of resonant vibrational modes in a triaxial ellipsoidal acoustic cavity with walls of arbitrary acoustic impedance has been quasi-analytically solved using the Frobenius power-series expansion method. Eigenmode results are presented for the lowest two eigenmodes in cases with pressure-release, rigid-wall, and lossy-wall boundary conditions. A mode crossing is obtained as a function of the specific acoustic impedance of the wall; the degeneracy is not symmetry related. Furthermore, the damping of the wave is found to be maximal near the crossing.     

Multifunctional carbon-coated magnetic sensing graphene oxide-cyclodextrin nanohybrid for potential cancer theranosis

Journal of Nanoparticle Research - Over the last years, an environmentally friendly and economically efficient way of nanoparticle production has been found in the biosynthesis of metal...     

Alkyl Chain Length- and Polymorph-Dependent Photomechanochromic Fluorescence of Anthracene Photodimerization in Molecular Crystals: Role of the Lattice Stiffness

Anthracene–pentiptycene hybrid systems 1-Cn , where n refers to the number of carbon atoms in the linear alkyl chain, crystallize in three different polymorphs, denoted Y (yellow), G (green), and B (blue) forms in terms of the fluorescence color. While all Y-form crystals show the same yellow-to-blue fluorescence color response to the photomechanical stress generated by the anthracene [4+4] photodimerization reaction, the four G forms exhibit distinct photomechanofluorochromism (PMFC): from green to blue for G-1-C4 , to orange for G-1-C7 , to red for G-1-C8 , and to red then blue for G-1-C9 , and the B forms show no photochromic activity. The intriguing RGB three-color PMFC and abnormal topochemical reactivity of G-1-C9 are attributed to inherent softness of the crystal lattice.     

Flow acoustics in periodic structures

A recent paper [A.A. Krokhin, J. Arriaga, L.N. Gumen, Speed of sound in periodic elastic composites, Phys. Rev. Lett. 91 (2004) 264302-1-4] addresses the speed of sound in periodic elastic composites (phononic crystals) with particular emphasis to the case where air bubbles are present in water and arranged periodically. In such periodically arranged mixtures, the well-known phenomena of the drop of the speed of sound may occur and applications related to, e.g., sound-beam focusing and acoustic surgery are possible [F. Cervera, L. Sanchez, J.V. Sanchez-Perez, R. Martinez-Sala, C. Rubio, F. Meseguer, C. Lopez, D. Caballero, J. Sanchez-Dehesa, Phys. Rev. Lett. 88 (2002) 023902]. In this paper, the analysis is extended theoretically to include cases where a background flow in a periodic structure is maintained. Calculations of dispersion relations and group velocities are presented in cases with one- and two-dimensional material periodicity for background flow values in the range: 0-1m/s. Materials considered in the calculations are periodic water-air mixtures. It is shown that acoustic waves couple to the group velocities only if the (acoustic) wave vector has a component along the background flow velocity direction.     

High-performance integrated field-effect transistor-based sensors

Field-effect transistors (FETs) have succeeded in modern electronics in an era of computers and hand-held applications. Currently, considerable attention has been paid to direct electrical measurements, which work by monitoring changes in intrinsic electrical properties. Further, FET-based sensing systems drastically reduce cost, are compatible with CMOS technology, and ease down-stream applications. Current technologies for sensing applications rely on time-consuming strategies and processes and can only be performed under recommended conditions. To overcome these obstacles, an overview is presented here in which we specifically focus on high-performance FET-based sensor integration with nano-sized materials, which requires understanding the interaction of surface materials with the surrounding environment. Therefore, we present strategies, material depositions, device structures and other characteristics involved in FET-based devices. Special attention was given to silicon and polyaniline nanowires and graphene, which have attracted much interest due to their remarkable properties in sensing applications.     

Pressure effect on structural,electronic and thermodynamic investigations of europium filled skutterudite EuFe4Sb12: LDA and LSDA approximations

Numerical calculations based on the full potential muffin-tin orbitals method (FP-LMTO) within the local density approximation (LDA) and the local spin-density approximation (LSDA) to investigate the structural, electronic and thermodynamic properties of filled skutterudite EuFe₄Sb₁₂ are presented. The electronic band structure and density of states profiles prove that this material is a conductor. The present investigation is also extended to the elastic constants, such as the bulk modulus B, anisotropy factor A, shear modulus G, young's modulus E, Poisson's ratio ν, and the B/G ratio with pressure in the range of 0–40 GPa. The sound velocities and Debye temperatures are also predicted from the above constants. The variations of the primitive cell volume, expansion coefficient α, bulk modulus B, heat capacity (C_p and C_v), Debye temperature θ_D, Helmholtz free energy A, Gibbs free energy G, entropy S, and internal energy U with pressure and temperature in the range 0–3000 K are calculated successfully.