Ab-initio study of the vibrational properties of Mg(AlH$_4$)$_2$
Based on Density Functional Theory and Density Functional Perturbation Theory we have studied the thermodynamical and vibrational properties of Mg(AlH$_4$)$_2$.
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Raman thresholds and rigid to floppy transitions in calcium silicate glasses
Alkaline earth silicate glasses $xCaO-(1-x)SiO_2$ exhibit a well marked threshold in Raman lineshapes which can be related to the onset of network rigidity as the concentration of calcium oxide $x$ is decreased. The present results are analyzed by constraint counting algorithms and more deeply characterized by a size…
Quantum Mott Transition and Multi-Furcating Criticality
Phenomenological theory of the Mott transition is presented. When the critical temperature of the Mott transition is much higher than the quantum degeneracy temperature, the transition is essentially described by the Ising universality class. Below the critical temperature, phase separation or first-order transition o…
Level structure and spin-orbit effects in semiconductor nanorod dots
We investigate theoretically how the spin-orbit Dresselhaus and Rashba effects influence the electronic structure of quasi-one-dimensional semiconductor quantum dots, similar to those that can be formed inside semiconductor nanorods. We calculate electronic energy levels, eigen-functions, and effective g-factors for c…
[Gd-AAZTA]-: A New Structural Entry for an Improved Generation of MRI Contrast Agents
An innovative MRI contrast agent based on the unprecedented and easily obtained ligand AAZTA is described. The simple and straightforward synthesis of the ligand, together with the potentiometric and relaxometric behavior of the corresponding Gd(III) chelate, is reported. The complex [Gd(AAZTA)]- shows outstanding mag…
Atomic Charges for Classical Simulations of Polar Systems
Structure and reactivity often are dependent on the polarity of chemical bonds. This relationship is reflected by atomic charges in classical (semiempirical) atomistic simulations; however, disagreement between atomic charges from accurate experimental investigations, ab initio methods, and semiempirical methods has n…
Probing Electronic Transitions in Individual Carbon Nanotubes by Rayleigh Scattering
Rayleigh scattering spectra were obtained from individual single-walled carbon nanotubes with the use of a laser-generated visible and near-infrared supercontinuum. This diagnostic method is noninvasive and general for nanoscale objects. The approach permits clear identification of excited states in arbitrary metallic…
Strain hardening in polypropylenes and its role in extrusion foaming
Abstract Extensional viscosity of several polypropylene polymers and their blends was measured and the foam processing of these blends using carbon dioxide blowing agent was studied. Foaming was carried out on a co‐rotating twin‐screw extrusion line, with a gear pump to build pressure. A linear isotactic polypropylene…
Foam Superstabilization by Polymer Microrods
Few foam systems stabilized by solid particles have been reported, and usually the particles have been used in combination with surfactants. We report how foams can be stabilized solely with a new class of anisotropic particles, hydrophobic polymer microrods of diameter less than 1 mum and length of a few tens of micr…
Ring‐banded spherulites in poly(pentamethylene terephthalate): A model of waving and spiraling lamellae
Abstract A new aryl polyester, poly(pentamethylene terephthalate) (PPT) with five methylene groups in the repeat unit, was synthesized. Its multiple‐melting behavior and crystal structure were analyzed with differential scanning calorimetry and wide‐angle X‐ray diffraction. In addition, the spherulitic/lamellar morpho…
Exploitation of the thermotunnel effect for energy scavenging
Over the past few years, MEMS and smart material technologies improvements have allowed autonomous sensor devices to become more and more widespread. As batteries are not always appropriate to power these systems, energy scavenging solutions from ambient power are currently being developed. In particular, many researc…
Polarized Raman scattering of highly [111]-oriented Pb(Zr,Ti)O3 thin films in the rhombohedral-phase field
Highly [111]-oriented rhombohedral lead zirconate titanate [Pb(Zr1−xTix)O3;PZT] thin films were prepared on Pt(111)∕Ti∕SiO2∕Si substrates by suitably combining pulsed laser deposition with sol-gel coating. Two distinctive types of the backscattering geometry were employed for the polarized Raman scattering study: (i)…
Microcavity-like leaky mode emission from a planar optical waveguide made of luminescent silicon nanocrystals
The propagation of light emitted from silicon nanocrystals forming planar waveguides buried in SiO2 is studied both experimentally and theoretically. Experiments reveal that photoluminescence spectra detected from the sample facet mainly contains narrow (10–20nm full-with-at-half-maximum) polarization-resolved transve…
Fabrication temperature effect of the field emission from closed and open tip carbon nanotube arrays fabricated on anodic aluminum oxide films
We have studied the field emission from highly ordered closed and open tip carbon nanotubes (CNTs) fabricated, in the range of 550–750°C, on porous anodic aluminum oxide films. The field-emission efficiency of the closed and open tip CNTs showed the opposite behavior as the fabrication temperature increased. The forme…
High resolution x-ray absorption spectroscopy using a laser plasma radiation source
In this article we present a setup of a spectrometer for near edge x-ray absorption spectroscopy at the carbon K-edge (284 eV). The spectrometer works with a laser produced plasma as x-ray source and a single x-ray optical element in grazing incidence configuration called off-axis reflection zone plate. Using differen…
Femtosecond time-resolved reflection spectroscopy of photoinduced ionic-neutral phase transition in TTF-CA crystals
We study the dynamics of photoinduced transition from ionic to neutral phases in tetrathiafulvalen-$p$-chloranil crystals by means of the fs time-resolved reflection spectroscopy at $6\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. We find that the phase transition consists of three sequential steps: (1) Precursor neutral reg…
Amine‐cured epoxy/clay nanocomposites. II. The effect of the nanoclay aspect ratio
Abstract The thermophysical and mechanical properties of a nanocomposite material composed of amine‐cured diglycidyl ether of bisphenol A (DGEBA) reinforced with organomontmorillonite clay are reported. The storage modulus at 100 °C, which was above the glass‐transition temperature ( T g ), increased approximately 350…
Electronic Structure and Bonding of Au on aSiO2Cluster: A Nanobullet for Tumors
The binding of gold atoms to a small silica cluster has been studied by using density functional theory with generalized gradient approximation for exchange and correlation. It is shown that gold atoms bind to silicon atoms with dangling bonds and serve as seeds for the growth of Au islands. The large electron affinit…
Synthesis and Structure of Nongeminally Substituted Cyclic Phosphazenes with Haloalkyl and Thioester Functional Groups
Nongeminally substituted cyclic phosphazenes with various haloalkyl substituents were prepared using deprotonation-substitution reactions at the methyl groups of the cis isomers of nongeminally substituted cis-[Me(Ph)P=N]3, 2. Treatment of 2 with n-BuLi followed by reaction with organic halogenated reagents (RX=C2Cl6,…
Formation, structure, and phonon confinement effect of nanocrystalline Si1−xGex in SiO2-Si-Ge cosputtered films
Using magnetron cosputtering of SiO2, Ge, and Si targets, Si-based SiO2:Ge:Si films were fabricated for exploring the influence of Si target proportion (PSi) and annealing temperature (Ta) on formation, local structure, and phonon properties of nanocrystalline Si1−xGex (nc-Si1−xGex). At low PSi and Ta higher than 800°…