Bright blue emission from Te-doped ZnS nanowires

Optical properties of Te-doped ZnS (ZnS:Te) nanowires (NWs) synthesized by a thermal chemical vapor deposition method were investigated by cathodeluminescence and photoluminescence (PL) measurements. ZnS:Te NWs exhibit the blue emission with the maximum peak at ∼440 nm at room temperature. We calculated Te-induced states on the valence band and conduction band in ZnS bulk crystal compared with PL peaks of ZnS:Te NWs. Temperature-dependent PL indicated that the activation energy of electron confined in ZnS:Te NWs is 85 meV. Blue light-emitting dot matrix displays were also fabricated using ZnS:Te NWs. This result suggested that ZnS:Te NWs could be applied as a blue-color-emitter on display devices.     

Simulation of coherent structures in nonlinear Schrödinger-type equations

This paper presents some numerical methods to simulate the evolution of coherent structures with small fluctuations, that appear as typical solutions of a class of nonintegrable nonlinear Schrödinger equations. The construction of the methods is particularly focused on two points: on one hand, the generation of the ground state profiles, to be used in the initial data of the simulations, combines a suitable spatial discretization with the resolution of a discrete variational problem. On the other hand, the approximation to leading parameters of these structures is controlled by the time integration. We compare different methods when simulating the evolution of initial ground state profiles and some initial data perturbed from them.     

Properties of boron and phosphorous incorporated tetrahedral amorphous carbon films grown using filtered cathodic vacuum arc process

This paper reports the electrical, mechanical, structural and field emission properties of as grown and also boron and phosphorous incorporated tetrahedral amorphous carbon (ta-C) films, deposited using a filtered cathodic vacuum arc process. The effect of varying boron and phosphorous content (up to 2.0 at.% in to ta-C) on the conductivity (σ_D), activation energy (ΔE₁), hardness, microstructure, emission threshold (E_turn-ON) and emission current density (J) at 12.5 V/μm of ta-C: B and ta-C: P films deposited at a high negative substrate bias of −300 V are reported. It is observed that both boron and phosphorous incorporation leads to a nearly an order increase in σ_D and corresponding decrease in ΔE₁ and a slight increase in hardness as compared to as grown ta-C films. In the case of field assisted electron emission, it is observed that E_turn-ON increases and J decreases. The changes are attributed to the changes in the sp³/sp² ratio of the films due to boron and phosphorous incorporation. The effect of boron on ta-C is to give a p-type effect whereas the effect of phosphorous gives n-type doping effect.     

Co-microencapsulate of ammonium polyphosphate and pentaerythritol and kinetics of its thermal degradation

Co-microencapsulated ammonium polyphosphate (APP) and pentaerythritol (PER) (M (A&P)) is prepared using melamine-formaldehyde (MF) resin by in situ polymerization method, and characterized by Energy dispersive spectrometer (EDS) and Fourier transform infrared (FTIR) spectra. Thermal stability of M (A&P) has been analyzed and compared with APP/PER mixture. In air atmosphere, the mass loss of M (A&P) at different heating rates was investigated using TGA. The kinetics of thermal degradation and activation energy was described using Flynn-Wall-Ozawa and Kissinger methods. It showed that there were two degradation stages. Expanded carbon structure with honeycomb was formed in the first stage between 200 and 450 °C. The second stage was the oxidation of carbon with E_a as high as 151.7 kJ/mol, so the expanded carbon had a good thermal stability. The reaction order of thermal degradation was found to be 0.935, so the mechanism of M (A&P) thermal degradation was controlled by the process of random nuclear formation and growth.     

Diffusion and solubility of mineral oils through ethylene-vinyl acetate copolymer

This paper reports a study of mineral oil diffusion through a filled ethylene-vinyl acetate crosslinked polymer, together with some comparisons with aliphatic linear hydrocarbons. Permeation was monitored by classical gravimetric measurements leading to values of solubility and diffusion coefficient at several temperatures ranging from 20 to 120 °C. Diffusion coefficients display a change in activation energy at at ca. 70 °C for mineral oils but not for simple hydrocarbons. The values obtained were discussed regarding available structure-diffusivity relationships and diffusion models derived from free volume theory. A relationship between penetrant evaporation temperature and its diffusivity was observed and tentatively justified.     

Studies on the activation energy from the ac conductivity measurements of rubber ferrite composites containing manganese zinc ferrite

Manganese zinc ferrites (MZF) have resistivities between 0.01 and 10 Ω m. Making composite materials of ferrites with either natural rubber or plastics will modify the electrical properties of ferrites. The moldability and flexibility of these composites find wide use in industrial and other scientific applications. Mixed ferrites belonging to the series Mn_(1−x)Zn_xFe₂O₄ were synthesized for different ‘x’ values in steps of 0.2, and incorporated in natural rubber matrix (RFC). From the dielectric measurements of the ceramic manganese zinc ferrite and rubber ferrite composites, ac conductivity and activation energy were evaluated. A program was developed with the aid of the LabVIEW package to automate the measurements. The ac conductivity of RFC was then correlated with that of the magnetic filler and matrix by a mixture equation which helps to tailor properties of these composites.     

Transition time asymptotics of queue-based activation protocols in random-access networks

We consider networks where each node represents a server with a queue. An active node deactivates at unit rate. An inactive node activates at a rate that depends on its queue length, provided none of its neighbors is active.For complete bipartite networks, in the limit as the queues become large, we compute the average transition time between the two states where one half of the network is active and the other half is inactive. We show that the law of the transition time divided by its mean exhibits a trichotomy, depending on the activation rate functions.     

The activation mechanism of peroxidase by ultrasound

The activation mechanism of peroxidase by ultrasound was investigated. The catalysis performance of peroxidase with ultrasound treatment was prior to the controls determined by UV–visible spectra and Fourier transform infrared spectra. The transformation of tryptophan residues in peroxidase led to the increase of a-helix and anti-parallel content in the secondary structure, and the content of p-sheet, p-turn and random coil in the secondary structure. In addition, under the atomic force microscope, under ultrasonic treatment, the large molecular clusters of tyrosinase are broken down into small molecular clusters. The current results showed that the activity of peroxidase is activated under ultrasonic treatment, which is mainly caused by ultrasound without conformational change, the catalytic center is exposed, and the affinity with the substrate is stronger.     

Trouton–Noble Paradox Revisited

An apparent paradox is obtained in all previous treatments of the Trouton–Noble experiment; there is a three-dimensional (3D) torque T in an inertial frame S in which a thin parallel-plate capacitor is moving, but there is no 3D torque T′ in S′, the rest frame of the capacitor. Different explanations are offered for the existence of another 3D torque, which is equal in magnitude but of opposite direction giving that the total 3D torque is zero. In this paper, it is considered that 4D geometric quantities and not the usual 3D quantities are well-defined both theoretically and experimentally in the 4D spacetime. In analogy with the decomposition of the electromagnetic field F (bivector) into two 1-vectors E and B we introduce decomposition of the 4D torque N (bivector) into 1-vectors N _s , N _t . It is shown that in the frame of “fiducial” observers, in which the observers who measure N _s and N _t are at rest, and in the standard basis, only the spatial components and remain, which can be associated with components of two 3D torques T and T _t . In such treatment with 4D geometric quantities the mentioned paradox does not appear. The presented explanation is in complete agreement with the principle of relativity and with the Trouton–Noble experiment without the introduction of any additional torque.     

Photoconductivity of Se85−xTe15Hgx thin films

The photoconductive properties such as dark conductivity, steady state and transient characteristics of a-Se_85−xTe₁₅Hg_x thin films, prepared by thermal vacuum evaporation technique have been studied in the temperature range 312–380 K. Analysis of data shows that the activation energy of dark current is greater as compared to the activation energy of photocurrent. The activation energy increases at higher concentration of Hg which shows that the defect density of states decreases. Analysis of intensity dependent photoconductivity shows that the bimolecular recombination is predominant. The transient photoconductivity shows that the carrier lifetime decreases with the increase in Hg concentration and increases at higher concentration of Hg. This decrease is due to the transition trapping process. Further the photosensitivity and carrier lifetime increases at higher concentration of Hg which also confirms that the density of defect states decreases.