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Key Criterion (key + criterion)
Selected AbstractsPreparation and properties of ,-chitin-whisker-reinforced hyaluronan,gelatin nanocomposite scaffoldsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Parintorn Hariraksapitak Abstract Tissue scaffolds made of naturally derived polymers present poor mechanical properties, which may limit their actual utilization in certain areas where high strength is a key criterion. This study was aimed at developing tissue scaffolds from a 50 : 50 w/w blend of hyaluronan (HA) and gelatin (Gel) that contained different amounts of acid-hydrolyzed ,-chitin whiskers (CWs) by a freeze-drying method. The weight ratios of the CWs to the blend were 0,30%. These scaffolds were characterized for their physical, physicochemical, mechanical, and biological properties. Regardless of the CW content, the average pore size of the scaffolds ranged between 139 and 166 ,m. The incorporation of 2% CWs in the HA,Gel scaffolds increased their tensile strength by about two times compared to those of the other groups of the scaffolds. Although the addition of 20,30% CWs in the scaffolds improved their thermal stability and resistance to biodegradation, the scaffolds with 10% CWs were the best for supporting the proliferation of cultured human osteosarcoma cells (SaOS-2). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] The relative orientation of the Arg and Asp side chains defined by a pseudodihedral angle as a key criterion for evaluating the structure,activity relationship of RGD peptidesJOURNAL OF PEPTIDE SCIENCE, Issue 8 2004Sarantos Kostidis Abstract The ability of an integrin to distinguish between the RGD-containing extracellular matrix proteins is thought to be due partially to the variety of RGD conformations. Three criteria have been proposed for the evaluation of the structure,activity relationship of RGD-containing peptides. These include: (i) the distance between the charged centres, (ii) the distance between the Arg C, and Asp C, atoms, and (iii) the pseudo-dihedral angle defining the Arg and Asp side-chain orientation formed by the Arg C,, Arg C,, Asp C, and Asp C, atoms. A comparative conformation,activity study was performed between linear RGD peptides and strongly constrained cyclic (S,S) -CDC- bearing compounds, which cover a wide range of inhibition potency of platelet aggregation. It is concluded that the fulfilment of the ,45° , pseudo-dihedral angle , +45° criterion is a prerequisite for an RGD compound to exhibit inhibitory activity. Once this criterion is accomplished, the longer the distance between the charged centres and/or between the Arg and Asp C, atoms, the higher is the biological activity. In addition, the stronger the ionic interaction between Arg and Asp charged side chains, the lower the anti-aggregatory activity. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd. [source] Reactively and physically compatibilized immiscible polymer blends: stability of the copolymer at the interfaceMACROMOLECULAR SYMPOSIA, Issue 1 2003Charef Harrats Abstract This paper reports on the interfacial behaviour of block and graft copolymers used as compatibilizers in immiscible polymer blends. A limited residence time of the copolymer at the interface has been shown in both reactive blending and blend compatibilization by preformed copolymers. Polystyrene (PS)/polyamide6 (PA6), polyphenylene oxide (PPO)/PA6 and polymethylmethacrylate (PMMA)/PA6 blends have been reactively compatibilized by a styrene-maleic anhydride copolymer SMA. The extent of miscibility of SMA with PS, PPO and PMMA is a key criterion for the stability of the graft copolymer at the interface. For the first 10 to 15 minutes of mixing, the in situ formed copolymer is able to decrease the particle size of the dispersed phase and to prevent it from coalescencing. However, upon increasing mixing time, the copolymer leaves the interface which results in phase coalescence. In PS/LDPE blends compatibilized by preformed PS/hydrogenated polybutadiene (hPB) block copolymers, a tapered diblock stabilizes efficiently a co-continuous two-phase morphology, in contrast to a triblock copolymer that was unable to prevent phase coarsening during annealing at 180°C for 150 minutes. [source] A technique for rapid single-echo spin-echo T2 mappingMAGNETIC RESONANCE IN MEDICINE, Issue 2 2010Marshall S. Sussman Abstract A rapid technique for mapping of T2 relaxation times is presented. The method is based on the conventional single-echo spin echo approach but uses a much shorter pulse repetition time to accelerate data acquisition. The premise of the new method is the use of a constant difference between the echo time and pulse repetition time, which removes the conventional and restrictive requirement of pulse repetition time , T1. Theoretical and simulation investigations were performed to evaluate the criteria for accurate T2 measurements. Measured T2s were shown to be within 1% error as long as the key criterion of pulse repetition time/T2 ,3 is met. Strictly, a second condition of echo time/T1 , 1 is also required. However, violations of this condition were found to have minimal impact in most clinical scenarios. Validation was conducted in phantoms and in vivo T2 mapping of healthy cartilage and brain. The proposed method offers all the advantages of single-echo spin echo imaging (e.g., immunity to stimulated echo effects, robustness to static field inhomogeneity, flexibility in the number and choice of echo times) in a considerably reduced amount of time and is readily implemented on any clinical scanner. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc. [source] Neutrophil regeneration precedes healing of tissue destruction, as indicated by serum C-reactive protein, in children with cancer recovering from neutropenic feverACTA PAEDIATRICA, Issue 8 2002K Vettenranta Aim: To evaluate the relationship between absolute neutrophil count and C-reactive protein (CRP) in the recovery phase of neutropenic fever among paediatric patients with cancer. Methods: A total of 102 paediatric oncology patients with 177 episodes of fever and neutropenia was studied prospectively in a two-centre setting. Antimicrobial therapy was discontinued 9 d (mean) post-initiation with a mean absolute neutrophil count of 1.8 ± 109l -1 and CRP of 32 mg l -1. Results: The mean level of CRP below 20 mg l -1 was reached on day 12. The level of CRP peaked on the day following the commencement of antimicrobial therapy. Throughout the episodes of fever and neutropenia higher levels of CRP were associated with a lower absolute neutrophil count. Following defervescence the pace of marrow recovery as evidenced by an increasing absolute neutrophil count to < 0.2 and < 0.5 ± 109l -1 was more rapid than the normalization of serum CRP. There was a 2,3 d lag period between absolute neutrophil count exceeding the level of 200 ± 106l -1 and the return of CRP to a baseline level. All episodes were treated successfully and there were no fatalities. Conclusion: Among patients recovering from neutropenia and fever the signs of marrow recovery remain the key criterion in evaluating the safety of discontinuing antimicrobial therapy, with serum CRP remaining more of an indicator of ongoing tissue repair. [source] | |||||||||||||