Diffusion of carbon and titanium in γ -iron in a magnetic field and a magnetic field gradient

The diffusion coefficients of carbon and titanium in γ -iron were measured in a 6T magnetic field and in magnetic field gradients ranging from 30 to 45 T/m. We have found that the diffusion of carbon in γ -iron is retarded by application of a 6T magnetic field. In contrast with carbon diffusion, no noticeable effect of a magnetic field on the diffusivity of titanium in γ -iron is observed. On the other hand, the diffusion of carbon in γ -iron can be enhanced in a magnetic field gradient when carbon atoms move towards the direction with a higher magnetic field strength. The higher the magnetic field gradient strength becomes, the more the carbon diffusion is enhanced. Nevertheless, a magnetic field gradient causes a decrease in diffusivity of carbon in γ -iron when the opposite magnetic field gradient is applied.     

Vortex Dynamics in a Superconducting Film with a Kagome and?a?Honeycomb Pinning Landscape

The vortex dynamics in a superconducting thin Al film with a periodic Honeycomb or Kagome array of antidots has been investigated by electrical transport measurements. The large values of the superconducting coherence length and penetration depth of the Al films guarantee a maximum of one flux quantum trapped per pinning site. This allows us to directly compare the experimental results with previous theoretical investigations based on molecular dynamics simulations. For the Kagome lattice, two submatching features not anticipated theoretically at H/H ₁=1/3 and 2/3, where H ₁ is the field at which the number of vortices coincides with the number of pinning sites, are observed. Possible corresponding stable vortex patterns are suggested. For the Honeycomb pinning landscape, the commensurability effects are in agreement with the theoretical expectations. A preliminary analysis of the vortex mobility in this lattice shows the presence of a weak vortex guidance.     

Theory of constraints: is it a theory and a good one?

In this study, we attempted to advance the academic dialogue towards establishing TOC as a formal operations management theory, so it can continue improving practice. We link the component parts of the TOC and map the theoretical arrangement to the consensual definitional components and properties of a theory. Also, we examine whether TOC satisfy the virtues of a good theory (uniqueness, parsimony, conservation, generalisability, fecundity, internal consistency, empirical riskiness, and abstraction). Consequently, a practical outcome of our study stems from demonstrating the utility of the goodness criteria as a useful instrument for examining future theories in the field of operations. From a practitioner's standpoint, by establishing a strong theoretical foundation for TOC, we assist managers deploying it to gain better understanding of TOC elements and ultimately avoid implementation failures. Also, we increase the credibility of TOC in the eyes of senior executives. The study concludes by sketching new avenues for future research that have industrial relevance for successful TOC implementation efforts.     

IMPLAST symposia and large deformations—a perspective

IMPLAST symposia have come of age, and are valued by the IMPLAST fraternity. A brief history of IMPLAST and its growth since the first in the series was held in 1973, and the contributions that these symposia have made to the subject, in general, are reviewed. Over the years there has been a phenomenal growth in the analytical, numerical, and experimental methods for the study of large deformation problems. Mechanics of large deformations, however, is yet not fully understood, and experimental observations are of help in providing plausible explanations, realistic assumptions, and parameters for the analysis of the phenomenon. In the second part of this paper, some observations in large deformation experiments which I hope would be of interest are presented.     

Nanoparticle-supported catalysts and catalytic reactions – a mini-review

This article reviews recent developments of using nanometer-sized particular matrices for supporting catalysts and catalytic organic reactions. Immobilization of a catalyst onto the surface of an Au or magnetic (e.g. Fe₂O₃) nanoparticle allowed facile separation and recycling of the catalyst out of the reaction mixture. The activity and selectivity of the nanoparticle-supported catalytic species were found to be comparable to those of their parent catalysts in solution or their counterparts immobilized on the solid-phase. In addition, due to the unique surface structure of the nano-host, cooperative catalysis was observed in a dyad of amino acid residues and peptide analogues on the nanoparticle surface. Thereby, immobilization of catalysts on the surface of a nanoparticular matrix will not only facilitate the isolation and recovery of expensive catalysts, but also open a new avenue to regulate their activity and selectivity.     

Extrinsic problem of mass exchange for a solid sphere and a drop at high peclet numbers and Re ≤100

Based on the solution of the problem of flow around a liquid sphere for 0.5Re100, values are found for the mass-transfer coefficients for a solid sphere, a drop, and a gas bubble in diffusion boundary-layer approximation.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 30, No. 1, pp. 69–72, January, 1976.     

A thin PANI and carrageenan–gold nanoparticle film on a flexible gold electrode as a conductive and low-cost platform for sensing in a physiological environment

In this work, we report the production of a layer-by-layer (LbL) film of gold nanoparticles stabilized with carrageenan (carr-AuNPs) interspersed with a conductive polyaniline (PANI) layer. Conventionally, PANI has poor electroactivity in physiological buffers, limiting its using in electrochemical biosensors. The films were prepared on low cost and easy to manufacture flexible gold electrodes (FEAu). Two adsorption sequences were tested for production of the films—PANI/carr-AuNP and carr-AuNP/PANI. The gold nanoparticle size and colloidal stability were characterized. The films were characterized by cyclic voltammetry, UV–visible spectroscopy and atomic force microscopy. The results showed the synergistic effects of the carr-AuNPs (120 nm) and PANI, which improved both the electrochemical response and the stability of the conductive polymer in physiological medium by three times. The presence of the carr-AuNPs in the film caused a significant increase in roughness of the FEAu-modified electrode compared to that of an unmodified electrode, resulting in an increased active electrode area. Studies of film growth by UV–Vis spectroscopy indicated that the deposition mechanisms of both films involved an auto-regulating adsorption process, with the same amount of material adsorbed in each coating step. The PANI/carr-AUNP film showed considerable improvement in stability and conductivity compared to PANI-only films in the physiological environment, which confers advantages for use as a biosensor.     

Primary and Anelastic Creep of a Near α-Ti Alloy and Their Dependencies on Stress and Temperature

The primary creep behaviour of a high temperature near -Ti alloy Ti6242Si has been investigated in the temperature range from 500 to 625°C, and the stress range from 80 to 450 MPa. The results are analysed in terms of the dependencies of stress on strain (strain hardening) and on strain rate (strain rate sensitivity). Furthermore, full unloading experiments were conducted in order to gain additional information as to the nature of primary creep. It is shown that primary creep can be described by an athermal component, strain hardening, with a mean strain hardening coefficient of 0.37, and a thermally activated component, strain rate sensitivity, with a strain rate sensitivity coefficient suggesting a mechanism based on climb controlled recovery. This is confirmed by the activation energy of 259 kJ/mol determined at different stresses, which is similar to the activation energy of Ti self diffusion in -Ti. The anelastic strain obtained on full unloading was analysed in its fast stage in a similar way. The kinetics of anelastic creep and its activation energy are in many aspects very similar to those of primary creep. It is thought that, in the stress and temperature range investigated, primary creep is to a relatively high extent anelastic in nature, and is controlled by the climb controlled bow out of pinned dislocation segments, particularly dislocations pinned at lath boundaries.     

Microstructural Characteristics and Stability in a RapidlySolidified Al-Fe-Nb-Si Alloy

The microstructure and stability in a rapidly solidified Al-Fe-Nb-Si alloy were studied by using transmission electron microscopy (TEM) with energy dispersive X-ray spectrometry (EDXS) and X-ray difFraction technique. It is shown that the addition of Nb to Al-Fe-Si alloy may increase undercooling of melt, and form the featureless zone structure, the size of the intercellular phases and the distance betWeen intercellulars of Al-Fe-Nb-Si alloy are two times smaller than that of Al-Fe-V-Si alloy under the same conditions. Further, the microstructure of the featureIess zone has the better thermal stability after annealing at 623 K for 24 h.     

Preparation and evaluation of a timolol maleate drug–resin ophthalmic suspension as a sustained-release formulation in vitro and in vivo

Abstract

The aim of this work was to assess the performance of resin as an ocular delivery system. Timolol maleate (TM) was chosen as the model drug and an ion exchange resin (IER) as the carrier. The drug–resin complex was prepared using an oscillation method and then characterized regarding particle size, zeta potential, morphology, and drug content. After in vitro drug release study and corneal permeation study were performed, in vivo studies were performed in New Zealand albino rabbits using a suspension with particles sized 4.8?±?1.2?μm and drug loading at 43.00?±?0.09 %. The results indicate that drug released from the drug–resin ophthalmic suspension permeated the cornea and displayed a sustained-release behavior. Drug levels in the ocular tissues after administration of the drug–resin ophthalmic suspension were significantly higher than after treatment with an eye drop formulation but were lower in body tissues and in the plasma. In conclusion, resins have great potential as effective ocular drug delivery carriers to increase ocular bioavailability of timolol while simultaneously reducing systemic drug absorption.     

Focal switch and dual focal switch of a Hermite–Gaussian beam illuminating a lens and sinusoidal amplitude grating separated system

Based on the Collins formula, analytical representation of a Hermite–Gaussian beam propagating through a lens and sinusoidal amplitude grating separated system is obtained. Focal shift occurring in such a system is studied in detail with numerical calculation examples. It is found that the focal switch and the dual focal switch can emerge depending not only on the effective Fresnel number, but also on the uniform transmittance amplitude and the spatial frequency of the grating and beam parameter of the illumination Hermite–Gaussian beam.     

Enhanced π-π interactions between a C60 fullerene and a buckle bend on a double-walled carbon nanotube

In situ low-voltage aberration corrected transmission electron microscopy (TEM) observations of the dynamic entrapment of a C₆₀ molecule in the saddle of a bent double-walled carbon nanotube is presented. The fullerene interaction is non-covalent, suggesting that enhanced π-π interactions (van der Waals forces) are responsible. Classical molecular dynamics calculations confirm that the increased interaction area associated with a buckle is sufficient to trap a fullerene. Moreover, they show hopping behavior in agreement with our experimental observations. Our findings further our understanding of carbon nanostructure interactions, which are important in the rapidly developing field of low-voltage aberration corrected TEM and nano-carbon device fabrication.      

The Principle and Architecture of a Hybrid System of a Neural Network and an Expert System in Intelligent CAD of Electrical Machines

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Degradative and mechanical properties of a novel resorbable plating system during a 3-year follow-up in vivo and in vitro

We tested the tissue reactions and mechanical strength of a novel biodegradable craniomaxillofacial plating system, Inion CPS™, in the course of degradation. Plates and screws composed of l-lactide, d-lactide and trimethylene carbonate were implanted to the mandible and dorsal subcutis of 12 sheep. The animals were sacrificed at 6–156 weeks. Histological evaluation was done using paraffin and methylmetacrylate techniques. Degradative and mechanical properties during the follow-up were measured both of in vivo and in vitro implants. In light microscopy, the in vivo implant material began to fragment at 52 weeks and could not be detected at 104 weeks. No significant foreign body reactions were seen in the mandibles. The dorsal subcutis disclosed mild reactions, which were, however, not of clinical significance. The implants in vitro maintained their entire mass for 26 weeks and lost 63–80% of the mass by week 104. The inherent viscosity of the implants in vitro and in vivo diminished uniformly. The screws retained their shear strength for 12–16 weeks. The plates maintained their tensile strength for at least 6 weeks. The maximum capacity of the plates in 3-point bending tests diminished gradually by 87% in 26 weeks. In conclusion, the plates and screws examined maintain adequate strength for the healing period of a bone fracture or osteotomy, producing no harmful foreign body reactions. Dr Nieminen is a consultant for Inion Ltd., while the other co-authors do not have any conflicts of interest. Inion Ltd. has financed the costs related to the study sheep, including their housing.     

Interaction between a vortex and an edge dislocation nested in a cos‐Gaussian beam passing through a tilted lens

The interaction between a vortex and an edge dislocation nested in a cos‐Gaussian beam passing through a tilted lens was studied analytically and numerically. It is shown that in the presence of the tilted lens, by varying the cos‐part parameter of the beam, the slope of the edge dislocation, or the tilt coefficient of the lens, the topological charge is conserved for the case of the off‐axis edge dislocation, while charge conservation does not hold true for the case of an on‐axis edge dislocation, irrespective of the on‐axis or off‐axis vortex. The relation between the transverse positions (x, y) of vortices and the tilt coefficient is linear, and is interpreted.     

Where, and how, does a nanowire break?

Using molecular dynamics (MD) simulation, we studied the structural transformation and breaking mechanism of a single crystalline copper nanowire under continuous strain. At a certain strain rate, an ensemble of relaxed initial states of the nanowire can preferentially go through one or more paths of deformation. In each deformation path, disordered atoms can be generated at the specific positions of the nanowire, where necking and breaking take place afterward. Such a breaking position is not predetermined; multiple initial states lead to a strain-rate-dependent, statistical distribution of breaking positions.     

Editorial for a special issue on nanostructured metals and alloys

Nanostructured metals and alloys are a versatile family of metallic materials that possess various excellent properties and offer the potential for a diverse range of industrial and biomedical applications.Research over more than two decades in this field has achieved tremendous progress in processing,characterization,and microstructural design,as well as fundamental understanding,and applications.In recent years.     

Oxidation and Hot Corrosion Behavior of a Composite Coating System

The oxidation and hot corrosion behavior of Co-Ni-Cr-Al-Ta-Y coating produced by magnetron sputtering with and without enamel coating has been investigated in air at 900℃ and in molten 75 wt pct NaCl 25 wt pct Na2SO4 at 850℃. The results show that the enamel coating possesses good hot corrosion resistance in the molten salts, in comparison with the sputtered Co-Ni-Cr-Al-Ta-Y coating. In the hot corrosion test, breakaway corrosion did not occur on the samples with enamel coating and the composition of enamel coating did not significantly change either. The oxidation resistance of the sputtered coating, which offers good adhesion, can be improved by the enamel coating.