Poly(3-hydroxyalkanoate)s: Diversification and biomedical applications: A state of the art review

Biomaterials have played an important role in the treatment of disease and the improvement of health care. Synthetic and naturally occurring biodegradable and biocompatible polymers have been used as biomaterials. Polyhydroxyalkanoates (PHAs) are promising materials for biomedical applications because they are biodegradable, non-toxic and biocompatible. We will shortly summarize the modification reactions, which include functionalization and grafting reactions, to improve the mechanical, thermal and hydrophilic properties of PHAs. The use of the modified PHAs in numerous biomedical applications, such as sutures, cardiovascular patches, wound dressings, scaffolds in tissue engineering, tissue repair/regeneration devices, drug carriers will be discussed in this review.     

Magnetic chitosan microspheres: preparation and characterization

In this study, magnetic chitosan microspheres were prepared in a well shaped spherical form with a size range of 100 to 250 μm (size distribution ±15 to ±40 μm, respectively) by the suspension cross-linking technique for use in the application of magnetic carrier technology. The magnetic material (i.e. Fe₃O₄) used in the preparation of the magnetic chitosan microspheres was prepared by precipitation from FeSO₄ and Fe₂(SO₄)₃ solutions in basic medium and then ground to the desired size (i.e. 1–5 μm). The morphological and magnetic properties of the microspheres were characterized by different techniques (i.e. SEM, optical microscopy, magnetometry). The results demonstrated that the stirring rate of the suspension medium and the Fe₃O₄/chitosan ratio are the most effective parameters for the size/size distribution and the magnetic quality of the microspheres, while the chitosan molecular weight (MW) has no significant effect on these properties for the given MW range (i.e. 150 to 650 kDa). The best magnetic quality of the magnetic chitosan microspheres is around 9.1 emu/g microsphere at 10 kG magnetic field intensity.     

Plasma transferred arc surface modification of atmospheric plasma sprayed ceramic coatings

In this study, a 90MnCrV8 steel surface was coated with aluminum oxide and chromium oxide powders through the Atmospheric plasma spray (APS) and Plasma transferred arc (PTA) methods. The effects of PTA surface melting on the microstructure, hardness, and wear behavior were investigated. The microstructures of plasma-sprayed and modified layers were characterized by Optical microscopy (OM), Scanning electron microscopy (SEM) and Energy dispersive X-ray spectroscopy (EDS). The dry-sliding wear properties of the samples were determined through the ball-on-disk wear test method. Voids, cracks, and nonhomogeneous regions were observed in the microstructure of the APS ceramic-coated surface. These microstructure defects were eliminated by the PTA welding process. The microhardness of the samples was increased. Significant reductions in wear rate were observed after the PTA surface modification. The wear resistance of ceramic coatings increased 7 to 12 times compared to that of the substrate material.

     

Low-complexity adaptive decision-feedback equalization of MIMO channels

A new adaptive MIMO channel equalizer is proposed based on adaptive generalized decision-feedback equalization and ordered-successive interference cancellation. The proposed equalizer comprises equal-length subequalizers, enabling any adaptive filtering algorithm to be employed for coefficient updates. A recently proposed computationally efficient recursive least squares algorithm based on dichotomous coordinate descents is utilized to solve the normal equations associated with the adaptation of the new equalizer. Convergence of the proposed algorithm is examined analytically and simulations show that the proposed equalizer is superior to the previously proposed adaptive MIMO channel equalizers by providing both enhanced bit error rate performance and reduced computational complexity. Furthermore, the proposed algorithm exhibits stable numerical behavior and can deliver a trade-off between performance and complexity.     

Secondary extradural spinal tumours in children

Secondary extradural spinal tumours are very rare, but they comprise most of the extradural neoplasms seen in infancy and childhood. Thirty-nine patients with this type of secondary tumour were treated in our hospital between 1965 and 1991. The diagnosis was proved by biopsy in every case. Following surgical decompression, all 35 survivors had radiotherapy and/or chemotherapy. Their outcome is reported.     

Evaluation of Alfa grass soda lignin as a filler for novolak molding powder

Behavior of Alpha grass soda lignin was investigated for the preparation of novolak molding powders. Thermal analysis of the different investigated formulations indicated that molding powders prepared from Alpha grass soda lignin were more resistant to thermal degradation compared to a standard formulation prepared from wood flour. Limiting oxygen index determined for the different composites confirmed the higher thermal stability of Alpha grass soda lignin composites. Mechanical properties tested either from Shore hardness tests or from impact strength measurements revealed a slight decrease of mechanical properties for composites prepared from Alpha grass soda lignin. All these results showed the possibility to replace imported wood flours by locally available Alpha grass soda lignin to obtain phenolic composites with quite similar properties. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1065–1068, 2005     

Analysis of Large Seeds from Three Different Medicago truncatula Ecotypes Reveals a Potential Role of Hormonal Balance in Final Size Determination of Legume Grains

Legume seeds are important as protein and oil source for human diet. Understanding how their final seed size is determined is crucial to improve crop yield. In this study, we analyzed seed development of three accessions of the model legume, Medicago truncatula, displaying contrasted seed size. By comparing two large seed accessions to the reference accession A17, we described mechanisms associated with large seed size determination and potential factors modulating the final seed size. We observed that early events during embryogenesis had a major impact on final seed size and a delayed heart stage embryo development resulted to large seeds. We also observed that the difference in seed growth rate was mainly due to a difference in embryo cell number, implicating a role of cell division rate. Large seed accessions could be explained by an extended period of cell division due to a longer embryogenesis phase. According to our observations and recent reports, we observed that auxin (IAA) and abscisic acid (ABA) ratio could be a key determinant of cell division regulation at the end of embryogenesis. Overall, our study highlights that timing of events occurring during early seed development play decisive role for final seed size determination.     

Dynamic substructuring and reanalysis methods in a surrogate-based design optimization environment

In light weight structure design, vibration control is necessary to meet strict stability requirements and to improve the fatigue life of structural components. Due to ever-increasing demands on products, it is generally more convenient to include vibration prerequisites in a design process instead of using vibration control devices on fixed designs. One of the main difficulties associated to design optimization of complex and/or large structures is the numerous computationally demanding Finite Element (FE) calculations. The objective of this research is to present a novel strategy for efficient and accurate optimization of vibration characteristics of structures. In the proposed strategy, a sub-structuring method is utilized. The FE model of the complete structure is partitioned, reduced and then reassembled. This increases the computational efficiency of dynamic analyses. Moreover, this method is coupled with a novel reanalysis technique to speed up the repeated structural analyses. These methods are finally embedded in a surrogate-based design optimization procedure. An academic test problem is used for the validation of this novel approach.     

Conflict adaptation depends on task structure.

The dependence of the Simon effect on the correspondence of the previous trial can be explained by the conflict-monitoring theory, which holds that a control system adjusts automatic activation from irrelevant stimulus information (conflict adaptation) on the basis of the congruency of the previous trial. The authors report on 4 experiments showing that conflict adaptation is mediated by task structure as well as previous congruency. Experiment 1 showed that for 2 completely segregated sets of stimulus-response pairs there was no conflict adaptation across sets. However, if the stimulus sets overlapped for 2 separate response sets, conflict adaptation could be observed across the response sets. Experiment 2 showed that this effect was not due to the use of stimulus-response sets lateralized to 1 hemisphere each. Experiment 3 showed that if response sets are common for 2 separate stimulus sets, then conflict adaptation can again be observed across sets. Finally, Experiment 4 showed local control effects in the absence of confounding feature-overlap effects. These results indicate that deployment of control as evidenced by conflict adaptation reflects task structure. (PsycINFO Database Record (c) 2010 APA, all rights reserved)