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This study uses the Early Childhood Longitudinal Study-Kindergarten Cohort to examine the influence that teachers and classrooms have on children’s short- and long-term reading achievement trajectories throughout the elementary school years. The analytic sample in the 1st grade is 16,604 children nested within 5,029 teachers, the 3rd-grade sample includes 14,281 children nested within 6,023 teachers, and the 5th-grade sample includes 11,233 children nested within 4,734 teachers. Children’s previous teacher and classroom experiences are associated with a small but long-term influence on children’s reading achievement, explaining 5% to 10% of variability in student achievement at later time points. In contrast, the measures of concurrent teacher characteristics and qualifications, as well as concurrent instructional practices, used in this study were inconsistently associated with reading achievement in 1st, 3rd, and 5th grades. [ABSTRACT FROM PUBLISHER]

Hydrotalcite-hydroxyapatite material (HT-HAp) was produced by co-precipitation at room temperature (10 ≤ pH ≤ 11) with ultrasonic homogenization and hydrothermal treatment for 24 h/80 °C. The main physical-chemical characteristics were studied and the catalytic potential of the material was evaluated in transesterification of soybean oil into methyl esters. Best results were obtained at 240 °C, 4 h and 12:1 molar ratio methanol/oil: conversion rate of 80.4%. Free glycerol and free acids were not observed at these conditions. HT-HAp is a promising material for catalysis and adsorption studies. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Five different layered double hydroxides were synthesized from magnesium ethoxide in the presence of aluminium, gallium, indium, tin and zirconium acetylacetonates by using the sol-gel technique. The colloid suspensions initially obtained were gelled and separated by centrifugation. XRD patterns confirmed that the five solids thus obtained possessed a layered double hydroxide structure. Also, IR and Raman spectra revealed differences between the solids. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Majorana fermions (MFs) are exotic particles that are their own anti-particles. Currently, the search for MFs occurring as quasiparticle excitations in condensed matter systems has attracted widespread interest, because of their importance in fundamental physics and potential applications in topological quantum computation based on solid-state devices. Motivated by recent experimental progress towards the detection and manipulation of MFs in hybrid semiconductor/superconductor heterostructures, in this review, we present a novel proposal to probe MFs in all-optical domain. We introduce a single quantum dot (QD), a hybrid quantum dot-nanomechanical resonators (QD-NR) system, and a carbon nanotube (CNT) resonator implanted in a single electron spin system with optical pump-probe technology to detect MFs, respectively. With this scheme, a possible Majorana signature is investigated via the probe absorption spectrum and nonlinear optical Kerr effect, and the coupling strength between MFs and the QD or the single electron spin is also determined. In the hybrid QD-NR system, vibration of the NR will enhance the nonlinear optical effect, which makes the MFs more sensitive for detection. In the CNT resonator with a single electron, the single electron spin can be considered as a sensitive probe, and the CNT resonator behaved as a phonon cavity is robust for detecting of MFs. This optical scheme will provide another method for the detection MFs and will open the door for new applications ranging from robust manipulation of MFs to quantum information processing based on MFs. [ABSTRACT FROM AUTHOR]

ABSTRACT Unusually photoluminescent undoped oligomers and doped electrically conducting polymers of 4-(3-Pyrrolyl)butyric acid have been enzymatically synthesized using the oxidoreductase soybean peroxidase as a catalyst. This biocatalytic approach provides a direct route to a fluorescent-undoped oligomer of pyrrole that requires no protection/deprotection chemistry. The synthesis is carried out in aqueous media that requires only monomer, enzyme, and hydrogen peroxide. The undoped oligomer exhibits stable emission properties and is highly sensitive to the presence of environmentally important metal ions, such as Co(II), Hg(II), and Cu(II) in solution. Electrically conducting polymers can also be obtained by adding a dopant to a buffered reaction solution prior to initiating the polymerization. Polymers doped with camphor-10-sulfonic acid exhibit conductivity values as high as 10−2 S/cm. Additionally, polymers synthesized in the presence of a biobased cationic template, N,N,N-trimethylchitosan chloride, exhibit conductivity values that are an order of magnitude greater than polymers synthesized with the anionic polymeric template, poly(styrene sulfonic acid)-sodium salt. The biobased synthetic strategy described here is the first report of directly obtaining an undoped, fluorescent conjugated oligomer of a pyrrole in aqueous solution. Unlike conventional chemical catalysts, the enzyme does not dope the oligomer and therefore provides the opportunity to directly obtain fluorescent conjugated species. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41035. [ABSTRACT FROM AUTHOR]

The first hyperpolarizabilities β of the natural aromatic amino acids tryptophan and tyrosine have been investigated using several methods and basis sets. Some of the theoretical results obtained were compared to the only experimental hyper-Rayleigh scattering data available. The sensitivity of tryptophan to its local environment was analyzed by constructing two-dimensional potential energy plots around the dipeptide tryptophan-lysine. Static hyperpolarizabilities β(0) of the found minima were calculated by a second-order Møller-Plesset (MP2) method in combination with the 6-31 + G(d) basis set. Moreover, the efficiency of tryptophan and those of a series of unnatural amino acids as endogenous probe molecules were tested by calculating the nonlinear responses of some peptides. Impressive results were obtained for the amino acid ALADAN, which shows significantly improved nonlinear performance compared to other amino acids with weak nonlinear responses. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Chemistry is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fibrillization of peptides leads to the formation of amyloid fibres, which, when in large aggregates, are responsible for diseases such as Alzheimer's and Parkinson's. Here, we show that amyloids have strong nonlinear optical absorption, which is not present in native non-fibrillized protein. Z-scan and pump-probe experiments indicate that insulin and lysozyme β-amyloids, as well as α-synuclein fibres, exhibit either two-photon, three-photon or higher multiphoton absorption processes, depending on the wavelength of light. We propose that the enhanced multiphoton absorption is due to a cooperative mechanism involving through-space dipolar coupling between excited states of aromatic amino acids densely packed in the fibrous structures. This finding will provide the opportunity to develop nonlinear optical techniques to detect and study amyloid structures and also suggests that new protein-based materials with sizable multiphoton absorption could be designed for specific applications in nanotechnology, photonics and optoelectronics. [ABSTRACT FROM AUTHOR]

Intermediate neglect of differential overlap for spectroscopy is a semiempirical approach, which is widely used to calculate spectroscopic and electron-transfer properties of various molecular systems including biological molecules, transition metal compounds, and advanced materials. In the review, we consider the computational scheme of the method and its recent applications in chemistry, biophysics, and material science. © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this work, we investigate theoretically the spin-resolved local density of states (SR-LDOS) of a ferromagnetic (FM) island hybridized with an adatom, which is described by the Single Impurity Anderson Model (SIAM). Our results are comparable with Scanning Tunneling Microscope (STM) experimental data. [ABSTRACT FROM AUTHOR]

The second harmonic generation (SHG) hyperpolarizabilities of phenylalanine and homopolypeptides are investigated by configuration interaction among singly excited configurations (CIS) technique combined with the sum-over-states (SOS) method. The geometries of peptides containing phenylalanine ()n(n = 1-8) are optimized by B3LYP/6-31g(d) method, and they form the special structures like β-sheet (a common protein secondary structure). It is found that the energy gaps of various peptides are reduced and the hyperpolarizabilities are increased with the peptide chains lengthened. We discuss the origin of the second-order nonlinear optical response in phenylalanine homopolypeptides and confirm that the π → π* transitions in the aromatic residue of phenylalanine make the most important contributions to the second-order polarizability. Our results strongly suggest that the hyperpolarizabilities are dominated from the propagation direction of peptide chains. [ABSTRACT FROM AUTHOR]

Poly(2-amino-5-(4-pyridinyl)-1,3,4-thiadiazole) (PAPT) modified glassy carbon electrode (GCE) was fabricated and used for the simultaneous determinations of dopamine (DA), uric acid (UA) and nitrite (NO) in 0.1 mol L phosphate buffer solution (PBS, pH 5.0) by using cyclic voltammetry and differential pulse voltammetry (DPV) techniques. The results showed that the PAPT modified GCE (PAPT/GCE) not only exhibited electrocatalytic activities towards the oxidation of DA, UA and NO but also could resolve the overlapped voltammetric signals of DA, UA and NO at bare GCE into three strong and well-defined oxidation peaks with enhanced current responses. The peak potential separations are 130 mV for DA-UA and 380 mV for UA-NO using DPV, which are large enough for the simultaneous determinations of DA, UA and NO. Under the optimal conditions, the anodic peak currents were correspondent linearly to the concentrations of DA, UA and NO in the ranges of 0.95-380 μmol L, 2.0-1,000 μmol L and 2.0-1,200 μmol L for DA, UA and NO, respectively. The correlation coefficients were 0.9989, 0.9970 and 0.9968, and the detection limits were 0.2, 0.35 and 0.6 μmol L for DA, UA and NO, respectively. In 0.1 mol L PBS pH 5.0, the PAPT film exhibited good electrochemical activity, showing a surface-controlled electrode process with the apparent heterogeneous electron transfer rate constant ( k) of 25.9 s and the charge-transfer coefficient ( α) of 0.49, and thus displayed the features of an electrocatalyst. Due to its high sensitivity, good selectivity and stability, the modified electrode had been successfully applied to the determination of analytes in serum and urine samples. [ABSTRACT FROM AUTHOR]

Coherent spin-dependent electron transport is investigated in three conditions: (1) a C molecule is connected to two ferromagnetic (FM) electrodes symmetrically, (2) a CN molecule is connected to two FM electrodes symmetrically and (3) a CN molecule is connected to two FM electrodes asymmetrically. This work is based on a single-band tight-binding model Hamiltonian and the Green's function approach with the Landauer-Buttiker formalism. Electrodes used in this study are semi-infinite FM electrodes with finite cross-section. Obvious rectification effect is observed in the CN molecule which is connected to the FMelectrodes asymmetrically. This effect is more in the P alignment of FM electrodes than in AP alignment of FM electrodes. This study indicates that the rectification behaviour is due to the asymmetry in molecule and junctions. Also in this investigation tunnel magnetoresistance (TMR) is calculated for these molecules. Asymmetry is observed in TMR of CN which is coupled to the electrodes asymmetrically due to asymmetric junctions, but TMR of C is symmetric. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically studied the geometries, stabilities, and the electronic and thermodynamic properties of 4 H-cyclopenta[2,1- b,3;4- b′]dithiopene S-oxide derivatives (BTO-X, with X = BH, SiH, S, S=O, or O) using semi-empirical methods, ab initio methods, and density functional theory. The geometries and thermodynamic parameters calculated by PM3 were in good agreement with those calculated with B3LYP/6-31 G*. The band gap calculated using B3LYP/6-31 G* ranged from 3.94 eV (BTO-O) to 3.16 eV (BTO-B). The absorption λ calculated using B3LYP/6-31 G* was shifted to longer wavelengths when X = BH, SiH, or S=O (due to their electron-withdrawing effects) and to shorter wavelengths for BTO-S and BTO-O as compared to the λ for the thiophene S-oxide (2TO) dimer. The changes in Δ H°, Δ S°, and Δ G° calculated using both semi-empirical and DFT methods were quite similar. [ABSTRACT FROM AUTHOR]

Oleic acid (OA) is a monounsaturated omega-9 fatty acid which undergoes a first-order phase transition when it is influenced by high pressures. The transition results in a change of molecular structure, which was investigated by means of X-ray techniques [J. Przedmojski and R.M. Siegoczynski, X-ray diffraction investigation of oleic acid under high pressure, Phase Transit. 75 (2002), pp. 373-377]. Despite a significant change in the structure, the permittivity of the acid remains barely influenced during and after the phase transition. A rise in relative permittivity has been observed due to the increasing number of molecules per volume unit within a compression cycle. However, no significant fall in the permittivity has been observed as a result of the transition which occurs in the case of edible oils. This may be caused by a strongly dimerised structure and dipole-dipole interaction in the liquid at ambient pressure. [ABSTRACT FROM AUTHOR]

Transition energies for a ketocyanine dye and its complexes with Li and Mg ions with an implicit solvent have been studied. Molecular Dynamics simulations have been used to prepare structures of the dye in acetonitrle solution of lithium or magnesium perchlorate. TDDFT methodology has been used to calculate the transition energies for dye and dye-ion complexes solvated by an increasing number of acetonitrile molecules. Results have been compared to the predictions of the continuous solvation model. Evolution of the spectrum with the number of explicit solvent molecules has been observed and the solvent-induced shifts have been determined. It has been found that the explicit solvation model may predict sequence of transitions and their parentage different than that resulting from implicit solvation. Effect of the perchlorate counterion for the dye-cation spectrum has been also analyzed. [ABSTRACT FROM AUTHOR]

Copyright of International Journal of Quantum Chemistry is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract  Amorphous Mn2 polyphosphate materials were prepared at room temperature through the coacervation of polyphosphate solutions. These new materials display the typical Mn2 red emission with a broad band centered at 15,290 cm−1 (bandwidth—1,320 cm−1). Excitation spectra display typical Mn2 (d5) absorption bands assigned to transitions from the 6A1g ground state to the 4T2g, (4A1g, 4Eg), 4T2g, and 4T1g Mn2 excited states. Transition energies allow estimating the Mn2 ligand field strength as intermediate between the one observed in Mn2 aqueous solutions and the one observed in Mn2 phosphate glasses. Azo dyes, methyl red and methyl orange, were incorporated into the manganese polyphosphate coacervates structure. Raman scattering and visible light reflectance results show azo dyes acid forms inside the hydrated polyphosphate structure and sensitivity to the atmosphere pH. Release of azo dyes species was observed from these new solid hybrid materials in aqueous medium. [ABSTRACT FROM AUTHOR]

The field of molecular electronics is prompted by tremendous opportunities for using a single-molecule and molecular monolayers as active components in integrated circuits. Until now, a wide range of molecular devices exhibiting characteristic functions, such as diodes, transistors, switches, and memory, have been demonstrated. However, a full understanding of the crucial factors that affect charge transport through molecular electronic junctions should yet be accomplished. Remarkably, recent advances in transition voltage spectroscopy (TVS) elucidate that it can provide key quantities for probing the transport characteristics of the junctions, including, for example, the position of the frontier molecular orbital energy relative to the electrode Fermi level and the strength of the molecule–electrode interactions. These parameters are known to be highly associated with charge transport behaviors in molecular systems and can then be used in the design of molecule-based devices with rationally tuned electronic properties. This article highlights the fundamental principle of TVS and then demonstrates its major applications to study the charge transport properties of molecular electronic junctions. [ABSTRACT FROM AUTHOR]

The on-surface synthesis of carbon nanostructures has attracted tremendous attention owing to their unique properties and numerous applications in various fields. With the extensive development of scanning tunneling microscope (STM) and noncontact atomic force microscope (nc-AFM), the on-surface fabricated nanostructures so far can be characterized on atomic and even single-bond level. Therefore, various novel low-dimensional carbon nanostructures, challenging to traditional solution chemistry, have been widely studied on surfaces, such as polycyclic aromatic hydrocarbons, graphene nanoribbons, nanoporous graphene, and graphyne/graphdiyne-like nanostructures. In particular, nanostructures containing sp-hybridized carbons are of great advantage for their structural linearity and small steric demands as well as intriguing electronic and mechanical properties. Herein, the recent developments of low-dimensional sp-carbon nanostructures fabricated on surfaces will be summarized and discussed. [ABSTRACT FROM AUTHOR]

The large third-order nonlinearities of metal nanocluster doped oxide matrix composite films have been investigated widely, but there is very little literature reporting third-order nonlinearity of metal nanoparticle doped azobenzene molecule thin films induced by picosecond laser pulses. This paper has investigated the third-order nonlinearity of colloidal Ag and methyl orange composite films using the Z-scan technique with 38 ps pulses at 532 nm apart from the surface plasma resonance frequency of composite film. Large and negative third-order nonlinearity was observed. The mechanism responsible for the process of nonlinear refraction was discussed in terms of the enhancement of the local field effect, which was confirmed by using the SERS technique. At the end, the figures of merit were evaluated and the results showed that this material would be valuable in the application of all-optical devices. [ABSTRACT FROM AUTHOR]

We have studied, at the second-order Møller–Plesset level of approximation with the 6-31G(d) atomic basis set, the electron correlation effects on the first hyperpolarizability of increasingly long polymethineimine oligomers and alternating polymethineimine/polyacetylene copolymers showing different conformations. Both the direct (i.e., electronic) and indirect (i.e., geometric) electron correlation contributions are large and should consequently be accounted for, even for qualitative purposes. The electron correlation effects are both conformation and chain length dependent. Long alternating polymethineimine/polyacetylene copolymers present a very large first hyperpolarizabilities, especially in the all-trans conformation. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [ABSTRACT FROM AUTHOR]

Semiempirical molecular orbital methods have a long history. They serve to tackle large systems and complicated processes beyond the reach of ab initio or density functional methods. Although their setup is derived from Hartree-Fock theory, the design of approximate energy expressions and the empirical parameters are used to achieve higher accuracy than the underlying ab initio theory. In this way the effect of larger basis sets or correlation can be partially simulated. All widely used semiempirical methods establish their accuracy by error statistics for molecular properties with experimental and high-level ab initio or density functional theory calculations as a reference. Their computational efficiency makes them suitable for the study of biochemical systems and solid materials. The present review presents a variety of applications which demonstrate the need for and success of semiempirical methods. [ABSTRACT FROM AUTHOR]

Electropolymerized films have received considerable attention in the development of biosensors and biochips, and are advancing rapidly. This paper reviews recent advances and scientific progress in electrochemical immobilization procedures for biological macromolecules on electrodes via electrogenerated polymer films. Biomolecule immobilization is classified as covalent linkage, attachment by affinity interactions, and physical entrapment. The last approach entails the use of conducting and non-conducting films, composite polymer films, and templates for the electropolymerization process. Some advances in the electrochemical transduction of biological events (enzymatic reaction, immunoreaction, or oligonucleotide hybridization) involving the redox properties or the conductivity of electropolymerized films are also presented. [ABSTRACT FROM AUTHOR]

Based on the nonequilibrium Green's function method and density functional theory calculations, we theoretically investigate the electronic transport properties of an anthraquinone-based molecular switch with carbon nanotube electrodes. The molecules that comprise the switch can convert between reduced hydroquinone (HQ) and oxidized anthraquinne (AQ) states via redox reactions. Our results show that the on-off ratio is increased one order of magnitude when compared to the case of gold electrodes. Moreover, an obvious negative differential resistance behavior at much low bias (0.07 V) is observed in the HQ form. [ABSTRACT FROM AUTHOR]

Advances in photonics and optoelectronics depend on proposing new materials with well-defined nonlinear optics properties. Based on the foundations of density functional theory, this work presents a systematic investigation of linear and nonlinear optical properties of methyl orange, a well-known azo dye. Structural changes from alkaline to acidic structures drastically boost all investigated properties. For instance, the material dipole polarizability starts from an isotropic condition (αiso>Δα) to an anisotropic behavior (αiso<Δα). The first hyperpolarizabilities are also strongly tuned varying from 18.9 ×10-30 to 171.7 ×10-30 esu. A careful analysis of frontier molecular orbitals indicates proper wide-bandgap semiconductor energy gap (3.22 eV) and associates the highest hyperpolarizabilities to the lowest energy gap, which means semiconductor molecules with intense nonlinear optical activity. [ABSTRACT FROM AUTHOR]

Various techniques to characterize the nonlinear (NL) optical response of centro-symmetric materials are presented and evaluated with emphasis on the relationship between the macroscopic measurable quantities and the microscopic properties of photonic materials. NL refraction and NL absorption of the materials are the phenomena of major interest. The dependence of the NL refraction and NL absorption coefficients on the nature of the materials was studied as well as on the laser excitation characteristics of wavelength, intensity, spatial profile, pulse duration and pulses repetition rate. Selected experimental results are discussed and illustrated. The various techniques currently available were compared and their relative advantages and drawbacks were evaluated. Critical comparisons among established techniques provided elements to evaluate their accuracies and sensitivities with respect to novel methods that present improvements with respect to the conventional techniques. [ABSTRACT FROM AUTHOR]

Motivated by recent experimental progress towards the detection and manipulation of Majorana fermions in ferromagnetic atomic chains on a superconductor, we present a novel proposal based on a single-crystal diamond (SCD) microcantilever with a single nitrogen-vacancy (NV) center spin embedded in ultrapure diamond substrate to probe Majorana fermions in an all-optical domain. With this scheme, a possible distinct Majorana signature is investigated via the electron spin resonance spectrum. In the proposal, the SCD microcantilever behaves as a phonon cavity and is robust for detecting of Majorana fermions, while the NV center spin can be considered as a sensitive probe. Further, the vibration of the microcantilever will enhance the coupling effect, which makes the Majorana fermions more sensitive to detection and the well-established optical NV spin readout technology will certainly promote the detection. This proposed method may provide a potential supplement for the detection of Majorana fermions. [ABSTRACT FROM AUTHOR]