Comparison of surgically attached and non-attached repair of the rat Achilles tendon-bone interface. Cellular organization and type X collagen expression

The effects of surgical repair versus non-repair on cell morphology and type X collagen expression were investigated using a rat model of Achilles tendon avulsion. The animals were divided into four groups. In Group 1, tendon was reattached to the original attachment site by suturing through a drill hole in the calcaneus; in Group II, tendon was not reattached and a drill hole was not made; in Group III, tendon was not reattached but a drill hole was made; and the animals in Group IV were sham operated. In Group I (tendon reattached), at 2 weeks postoperatively, many hypertrophic chondrocytes appeared at the reattachment site adjacent to bone and type X collagen was detected immunologically both in the cells and in the extracellular matrix. After 4 weeks, the cells at the original site of attachment were arranged in rows along the newly formed tendon fibers and were stained with type X collagen antibody. By contrast, when tendon was not reattached (Groups II and III), a gap between the original attachment site and the tendon stump was observed through the entire postoperative period. At 8 weeks, the original attachment site was covered by fibrocartilaginous tissue and tendon became attached to the calcaneal fibrocartilage area, which is proximal to the original attachment site. Type X collagen was detected in the cells which were adjacent to bone. In Group IV (sham operation), there were no changes in histology or type X collagen distribution, either at the attachment site or in tendon and bone, compared with the non-operated control rats. These results suggest that surgical reattachment of tendon to the original site is important to help reorganize cells during the repair process. Type X collagen was identified immunohistochemically in the cells adjacent to bone in all the groups, suggesting that it may play a role in maintaining distinct areas of calcified and non-calcified fibrocartilage.     

Preparation and dielectric properties of La doped NBCCTO ceramics

Journal of Electroceramics - CaCu3Ti4O12 ceramics have great dielectric constant, excellent temperature stability and good frequency stability. However, due to high dielectric loss, its practical...     

Growth characteristics of agrowaste‐immobilised lactobacilli in soymilk during refrigerated storage

We aimed at evaluating agricultural wastes as solid supports for the immobilisation of lactobacilli in a liquid media, namely soymilk. Lactobacillus acidophilus FTDC 1331, L. acidophilus FTDC 2631, L. acidophilus FTDC 2333, L. acidophilus FTDC 1733 and L. bulgaricus FTCC 0411 were immobilised on solid supports produced from durian (Durio zibethinus), cempedak (Artocarpus champeden) and mangosteen (Garcinia mangostana). The immobilised cells were inoculated into soymilk and stored at 4 °C over 168 h. Soymilk inoculated with non‐immobilised cells was used as the control. Immobilised cells showed higher survivability over 168 h compared to the control, accompanied by higher reduction of simple sugars and oligosaccharides in soymilk. Higher growth and higher utilisation of substrates also led to the higher production of lactic and acetic acids, which lowered the pH in soymilk compared to the control. Our results illustrated that agrowastes could be used as immobilisers to enhance the growth of lactobacilli in a liquid medium.     

Influence of Liquid Phase Additives on Structural and Sintering Behaviour of Samarium Modified Lead Titanate Ceramics

The combination of metal oxides Bi₂O₃:Li₂O in a ratio 89:11 gives a eutectic with a melting point of ～680°C. Such a low melting point oxide combination creates a working liquid phase at a highly favorable temperature for use as a densification aid. A liquid—phase sintering aid incorporating Bi₂O₃ and Li₂O is presented which demonstrates not only a reduction in the required sintering temperature but also shows relatively higher ‘c/a’ ratio (tetragonality) of PbTiO₃ ceramics with no fragility of the samples. Detailed dilatometric investigations have been performed in order to study the dominant shrinkage mechanism in the present system. Besides acting as a liquid phase fluxing agent, Bi₂O₃/Li₂O also behave as Curie shifter, which decreases Curie temperature in lead titanate system. The Curie temperature has also been verified from the thermal expansion behavior of sintered specimens. The value of dielectric constant increases after poling which may be due to the dominance of 180° domain wall over 90°.     

Low temperature coefficient and low line sensitivity subthreshold curvature-compensated voltage reference

A high-order curvature-compensated subthreshold voltage reference is proposed in this paper. The proposed curvature-compensated voltage reference consists of two supply-independent first-order voltage references and a curvature compensation circuit. The supply-independent first-order voltage reference uses a negative feedback loop which improves the line sensitivity and eliminates the demand of operational amplifier, whereas the curvature compensation circuit provides high-order temperature-compensated output reference voltage. The proposed curvature-compensated voltage reference provides an output reference voltage of 118.54 mV with a temperature coefficient of 21.5 ppm/°C over a wide temperature range of −60°C to 120°C . The power supply rejection ratio and line sensitivity are observed as −68.64 dB (for the frequency range of 1 Hz to 100 Hz) and 0.035%/V (for the supply voltage varies from 0.85 V to 2.5 V), respectively. The values of output noise at the frequencies of 1 kHz and 10 kHz without using any capacitive filter are obtained as 179.13 nV/ √ Hz and 123.87 nV/ √ Hz , respectively.     

Combined economic and emission dispatch problems using biogeography-based optimization

In this work, biogeography-based optimization (BBO) is presented for solving different constrained economic load dispatch (ELD) problems combined with economic emission aspects in power system. Nonlinear characteristics of generators like valve point discontinuities, ramp rate limits and prohibited operating zones are considered in the problem. The simulation results show that the proposed BBO algorithm based solutions prove to be the best near-global optimal as compared to the solutions based on Newton–Raphson, Tabu search, genetic algorithm (GA), non-dominated sorting genetic algorithm (NSGA), fuzzy logic controlled genetic algorithm (FCGA), particle swarm optimization (PSO) and differential evolution (DE).     

Study of Temperature Dependence of Electrode–Glass Ceramic Interface Using Impedance Spectroscopy

The electrical behavior of strontium titanate borosilicate glass ceramics (SrO.TiO₂- 2SiO₂.B₂O₃) with additives K₂O, La₂O₃, CoO and Nb₂O₅ was studied by using Impedance Spectroscopy as a function of temperature and composition. An equivalent circuit model having three parallel RC's connected in series with a capacitor C₄ could represent the data well. By comparing the complex modulus plots with simulated ones and looking at the values of the time constants these RC's were attributed to represent crystalline, glassy and glass-crystal interface regions of the glass- ceramic whereas C₄ represented the glass-ceramic sample and contact electrode interface. When the glass ceramic sample contained only SrTiO₃ crystalline phase and the remaining glassy matrix, the interface capacitance showed an Arrhenius type of nature with an activation energy (0.11 ± 0.04) eV and when the glass- ceramic sample contained number of crystalline phases no clear cut trend appeared. These findings are useful in selecting suitable electrodes for applications as well as in deciding upon experimental techniques for measurement of dielectric constants of materials.     

Numerical and experimental study of bistable piezoelectric energy harvester

Piezoelectric energy harvesting from mechanical vibrations is a reliable technology to charge low power electronic equipment. It has been reported in the literature that low frequency broadband vibrations cannot be harvested effectively using linear piezoelectric energy harvester (PEH). In this paper a bistable nonlinear PEH with two distinct energy wells generated using repulsive magnetic interactions between a cantilever magnetic proof mass and an external magnet is considered. It has been modeled using finite element method and validated with experimental results. Experimental results verify that, for our study, distance between magnetic proof mass and external magnet of 1.32 T flux density should be less than or equal to 8.5?mm for maintaining bistability. This distance also affects to the resonance frequency of harvester. Maximum efficiency of the harvester has been noticed at 8.5mm. Further it has been shown experimentally that the bistable nonlinear piezoelectric energy harvester takes almost half of the time taken by its linear counterpart to charge a 20 mAh battery.     

Taguchi method to optimize the micron and submicron size cenosphere particulates filled E‐glass fiber‐reinforced vinylester composites

In this work, the mechanical and tribological characteristics of E‐glass fiber‐reinforced vinylester composites have been investigated experimentally under dry sliding conditions. The E‐glass fiber‐reinforced vinylester composites with uniform micron and submicron size cenosphere particulates of three different sizes (2 µm, 900 nm, and 400 nm) had been prepared in the laboratory. In this work the effect of parameters such as applied normal load, particulate size, sliding speed, sliding distance and roughness on friction and wear behavior have been carried. A plan of experiments, based on the Taguchi design, was performed to acquire data in a controlled way. An orthogonal array L₂₇ (3¹³) and Analysis of variance (ANOVA) have been applied to investigate the influence of process parameters on the coefficient of friction (COF) and sliding wear behavior of these composites. It was found that the submicron size particulates 400 nm as filler contributed significantly to improve the mechanical properties and wear resistance of the composites. The experimental results indicate that the specific wear rate is greatly influenced by applied normal load and particle size. ANOVA results showed that the applied normal load significantly influence the specific wear rate of cenosphere filled glass fiber‐reinforced vinylester composites. Regression analysis is carried to check the suitability of the prediction equation and modeling of the wear parameters and the typical R² values for COF and specific wear rate are 86.7 and 94.3%, respectively. The scanning electron microscopy are used clarify the experimental in the frictional and wear testing. POLYM. COMPOS., 35:775–787, 2014. © 2013 Society of Plastics Engineers