Sol-gel transition of a mixture of gelatin and κ-carrageenan

Abstract

The characteristics of sol-gel transition of a mixture made by mixing two kinds of gelling agents of different nature, i.e. gelatin and carrageenan were examined. The sample solutions consisted of 3.00 wt % gelatin solution, 1.00 wt % κ-carrageenan solution and 4.00 wt% mixed solution which was prepared by mixing the said gelatin and carrageenan solutions in the ratio 3:1. In the experiment, the optical rotation and the dynamic viscoelasticity were measured under the same temperature change program. As the sample solutions were cooled, the carrageenan solution started to show a change in the specific rotation in the first place, followed by the mixed solution and finally the gelatin solution. The gelatin and the mixed solutions had the same increasing tendency in the specific rotation, whereas the carrageenan solution changed a little. When the mixed solution was chilled to set, it turned into a highly elastic gel. In the mixed solution, the gelation of carrageenan was found to precede that of gelatin.     

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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Measurement and prediction of Young’s modulus of a Pb-free solder

Accurate and reproducible measurements of the Youngs modulus of solders are complicated by the early onset of yielding, microporosity, and variations in cooling rate. In this study, we report measurements of Youngs modulus of an Sn–3.5 wt % Ag solder by two techniques: (a) loading–unloading measurements in tension, and (b) non-destructive resonant ultrasound spectroscopy. Both techniques yielded similar values of Youngs modulus. The modulus decreased with increasing microporosity, in accordance with predicted values. Cooling rate affected the Ag₃Sn intermetallic morphology, but not Youngs modulus since the distribution of the particles was relatively random. This result was confirmed by microstructure-based finite element modeling.     

Evaluation of physical–chemical properties and biocompatibility of a microrough and smooth bioactive glass particles

The purpose of this study was to evaluate physical-chemical and biocompatibility characteristics of a simple synthesis and low cost experimental bioactive glass. Physical and chemical properties were analyzed using scanning electron microscopy (SEM), X-ray energy dispersive (EDX), X-ray fluorescence (XRF) and X-ray diffraction (XRD). The biomaterials were subcutaneously implanted into rats, according to the following groups: G1, PerioGlastrade mark; G2, Biograntrade mark, G3, Experimental Bioactive Glass U (BGU) and G4, Control (Sham). After 7, 15, 21, 45, and 60 days, 5 animals/group/period were sacrificed and the subcutaneous tissue was dissected for histological and histometric analysis, considering inflammatory reaction and granulation area, presence of polymorphonuclear (PMN), monuclear (MN) and fibroblast (F) cells. SEM analysis of biomaterials showed irregular particles with different surface characteristics. EDX showed calcium, oxygen, sodium, phosphorus and silicon; XRF revealed silica oxide (SiO(2)), sodium oxide (Na(2)O), calcium oxide (CaO) and phosphorus oxide (P(2)O(5)). XRD indicated non crystalline phase. Measurement of tissue reaction showed similar results among the experimental groups at 45 and 60 days. No difference was found for PMN, MN and F cell counts. All biomaterials exhibited partial resorption. In conclusion, the experimental bioactive glass analyzed showed physical and chemical characteristics similar to the commercially available biomaterials, and was considered biocompatible, being partially reabsorbed in the subcutaneous tissue.     

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.     

Preparation and thermal degradation behaviour of a layer-type complex consisting of TaS2 and α-naphthylamine

A layer-type complex TaS₂ (α-naphthylamine)_0.46 having a basal spacing of 2.2 nm was prepared by soaking a mixture of the components in an ampoule at 433 K for 25 to 35 days. This complex was resealed in an ampoule after purification, followed by γ-radiation and heating to 473 K. The resulting sample was again heated at various temperatures below 1273 K. On heating to 643 K, the insertedα-naphthylamine polymerized, although with some removal from the complex, with a decrease in basal spacing to 1.35 nm. Another complex appeared faintly simultaneously. This second complex with a basal spacing of 0.96 to 0.92nm formed more abundantly on heating to 773 K and then decreased in amount at higher temperature. The complex decomposed at1273 K to result in TaS₂. Such thermal degradation behaviour is discussed from the standpoint of preparation of the layer-type complex consisting of TaS₂ and carbon.     

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.     

Mixture of ε-caprolactone-lactide copolymer and tricalcium phosphate: a histological and immunohistochemical study of tissue reactions

In cranio-maxillofacial surgery, bone transplantation is needed for treatment of bony defects. An autograft, allograft or biomaterial can be used. Autogenous bone grafts are considered to be the best materials available, but there are some disadvantages in their use including donorsite morbidity, need for a second operative site and limited graft supply. A search for new bone-graft materials therefore remains necessary. We prepared a mixture of tricalcium phosphate (TCP), which is a resorbable, non-toxic, osteoconductive ceramic material and -caprolactone-lactide copolymer P(-CL/DL-LA), a resorbable polymer, and placed it in the dermis and in mandibular bone defects in 13 rabbits. Follow-up times were two, three, seven, eight, 12, 15 and 18 weeks, tissue reactions were assessed, histologically and immunohistochemically. Times of resorption of the material from tissues were reported. We found that the mixture caused a mild inflammatory reaction when placed in bone and severe inflammation when placed in dermis. No highly fluorescent layer of tenascin or fibronectin was found surrounding the implant area. The mixture was excellent to handle and very easy to place into bone defects. The results are promising and have led us to continue development of the mixture. © 1999 Kluwer Academic Publishers     

Preparation and Properties of a Group of Nanoporous Materials with Photo-semiconducting Host Structures

1. Introduction Preparation of nanostructured materials is a fundamental field for advances in nano-technology.Various chemical routes have been available that lead to well defined nanoparticles of metals or semiconductors, giving rise to different microelectronic applications.[1-4] Nanoporous crystals, on the other hand, having structures that contain pores of nanometer sizes, provide the possibility of ordering nanoparticles into strictly uniform arrays by occluding them in the pores. Nanoporous solids with insulating silicate host structures are well known.     

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.     

An Energy Model of a Failure Mechanism and its Application

The energy expression is presented for a failure mechanism, and it is applied in an Acceler-ated Life Test ( ALT) and an Accelerated Reliability Growth Test ( ARGT). The conditions of the common failure mechanism are obtained. The essential relationship between the conditions and the Accelerated Factor ( Af ) is proposed by using the energy model.     

Structure and formation of shot coke — a microscopy study

A series of shot cokes and sponge cokes from industrial delayed cokers was examined by scanning electron micrsocopy (SEM) and optical micrscopy (OM) of external, fractured internal and polished surfaces. Calcined cokes were etched with chromic acid solution and etching behaviour related to the optical texture of the cokes. The shot coke spheres have an inner structure of fine-grained mosaic and a smooth external skin, 50m thick, of coarse-grained mosaic and small domains. Sponge cokes can be heterogeneous with inclusions of well-ordered carbon within the matrix mosaics. It is considered that the feedstock leading to shot coke in the delayed coker forms a high viscosity fused pitch/ mesophase system which is subject to significant disturbance by volatile evolution. The paste-like system breaks up into fragments as a result of deep agitation by volatile release and movement through the system. The viscosity of the fragments is too high to permit their coalescence and reform a continuous system. Instead, they remain as fragments >1.0m diameter. Structure of cokes from delayed cokers and the associated manipulation of the system by the volatile evolution within the coker. These two factors are inter-related. Differences between cokes arise from differences between viscosities of the mesophase from the feedstock and control the balance between fragmentation and re-coalescence of the charge, as a result of manipulation by volatile release, leading to the two extremes of shot and needle coke.     

Excitation of Narrow‐Band Pulsations in a Short Portion of Transition from the Smaller Diameter of a Pipe to a Larger Diameter and Possibilities of Preventing Them

By using models of the portions of the circuit of main gascompressor stations, data on the frequencies of narrowband pressure pulsations have been obtained; these data demonstrate the jet character of flow in divergent channels with angles of opening on one side of 12°47 and 23°50. It has been shown that narrowband acoustic disturbances are generated in the internal flow with largescale hydrodynamic structures. Intense narrowband pulsations are prevented by a grid of internal divergent channels in the transition portion with small angles of opening in canals and in excitation of certain disturbances upstream of a short divergent channel.     

Investigation of the Strength and Elastic Properties of Glass‐Ceramic of a Lithium Alumosilicate Composition

This paper presents the results of investigations of the strength and elastic properties of the glassceramic obtained by novel technology with the use of the method of casting blanks from highdensity aqueous suspensions of lithium alumosilicate glass into porous moulds followed by their sintering and crystallization under combined conditions of thermal treatment. Comparison of the properties of the proposed glassceramic with the properties of the glassceramics obtained by conventional technology enabled us to gain a better insight into its potentialities and provide the necessary information for calculating the structural strength.     

Increasing the Resolution and SNR of an ADC＇s Measurement with a Method of OverSampling and Averaging

By analyzing the theory of over-sampling and averaging, the conclusion is educed that white noise accompanies the signal and the addition of each bit of resolution can be achieved via a fourfold sampling frequency. The addition of each bit will approximately increase the SNR （signal to noise ratio） to 6dB.     

Parameters of a Gas‐Powder Flow Formed by a Cumulative Accelerator and Realizing the Effect of Superdeep Penetration

The development of a gaspowder flow formed by an explosive accelerator with a cumulative recess in its lower part is numerically investigated. A comparative analysis of two variants of a cumulative system of impelling that are basic to the effect of superdeep penetration has been carried out, and their integral parameters have been estimated.     

Antiplane electro‐mechanical field of a bimaterial piezoelectric wedge under a pair of concentrated forces and surface charges

Abstract

This paper presents the general solutions of the antiplane electro‐mechanical field for a bimaterial piezoelectric wedge subjected to a pair of concentrated forces and surface charges. Identical wedge angles are assumed here. Using the Mellin transform method, the singularity orders and the generalized stress, strain, electric displacement and electric field intensity factors are derived analytically. The discussion of a semi‐infinite crack at the interface of two bonded piezoelectric half‐planes is also included. Some degenerated cases are investigated to check the accuracy of the obtained solutions.     

Antiplane electro‐mechanical field of a piezoelectric finite wedge under a pair of concentrated forces and free charges

Abstract

This paper presents general antiplane electro‐mechanical field solutions for a piezoelectric finite wedge subjected to a pair of concentrated forces and free charges. The boundary conditions on the circular segment are considered as traction free and insulated. Using finite Mellin transform methods, the stress and electrical displacement in all fields of the piezoelectric finite wedge are derived analytically. Singularity orders and intensity factors of stress and electrical displacement can be obtained too. After being reduced to a problem of an antiplane edge crack or an infinite wedge in a piezoelectric medium, the results compare well with those of previous studies.