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Crystallinity Index (crystallinity + index)

Distribution by Scientific Domains
Life Sciences50%

Selected Abstracts

Electrospun Silk Fibroin Mats for Tissue Engineering

ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 3 2008
A. Alessandrino
Abstract Processing Silk Fibroin (SF) with electrospinning (ES) offers a very attractive opportunity for producing a variety of 2D and 3D matrices with great potential for tissue regeneration and repair due to the superior biocompatibility and mechanical properties of SF. Different combinations of ES parameters were explored to investigate the best experimental set-up related to the dimension and uniformity of the fibers in the electrospun silk fibroin (ES-SF) mats. Using SEM it was found that the ES-SF mats contain uniform fibers with a diameter in the nanometric range obtained by electrospinning a 7.5,% w/v SF solution in formic acid, with an electric field of 2.4,kV/cm and a spinneret-collector distance of 10,cm. FT-IR and DSC analyses were performed to investigate the structure of the ES-SF mats before and after immersion in methanol for different times (5, 10, and 15,min). The methanol treatment was able to promote the crystallization of SF by conformational transition of random coil and other poorly ordered conformations (turns and bends) to the ,-sheet structure. The degree of crystallinity was enhanced as shown by the trend of both the FT-IR crystallinity index and the melting/decomposition peak temperature (from DSC). To study the cytocompatibility of ES-SF mats, tests with L929 murine fibroblasts were carried out. Samples were seeded with the cells and incubated for 1, 3, and 7,days at 37,°C. At each time point, SEM investigations and Alamar blue tests were performed. The SEM images showed cell adhesion and proliferation just after 1,day and cell confluence at 7,days. Alamar blue test demonstrated that there were very low differences between cell viability on ES-SF mats and the tissue culture plastic control. [source]

The impact of silane chemistry conditions on the properties of wood plastic composites with low density polyethylene and high wood content

POLYMER COMPOSITES, Issue 5 2010
Yu Geng
Silane chemistry was implemented on various formulations of wood/thermoplastic polymer composites (WPCs) with low density polyethylene (LDPE) and high wood content (60 wt%). Taguchi analysis was used to evaluate the impact of vinyltrimethoxysilane content (VTMS), dicumyl peroxide content (DCP), and processing temperature on the rheological, morphological, and dynamic mechanic properties of WPCs. The torque power was measured by a Haake torque rheometer and indicated that the VTMS content and temperature most significantly impacted the rheological properties related to silane reactions. Differential scanning calorimetry also showed a larger depression in LDPE melting point and crystallinity index when a high VTMS content (35 phr), high DCP content (0.5 phr), and a high compounding temperature (200°C) were used. With dynamic mechanical analysis (DMA), it was shown that the compounded formulations had a higher storage modulus over a wide range of temperature whereas the , transition temperature increased with higher content in silane reactants. Interestingly, the high humidity/temperature conditioning step aimed at crosslinking resulted in a drop of dynamic moduli compared to the freshly compounded formulations. This was explained by the fact that during compounding of LDPE with high wood content and silane reactants, significant amounts of matrix and interfacial silane crosslinking already occurred. Subsequent conditioning in a high humidity and temperature environment was proposed to hydrolyze the interfacial siloxane bonds resulting in a degradation of mechanical properties. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [source]

The crystallinity of ancient bone and dentine: new insights by transmission electron microscopy

ARCHAEOMETRY, Issue 3 2002
I. Reiche
We studied various archaeological and palaeontological bones and dentines from different burial environments by Fourier transform infrared spectroscopy (FT,IR), X,ray diffraction (XRD) and transmission electron microscopy (TEM), in the framework of a general study of diagenesis. FT,IR and XRD were used to evaluate the global preservation state of the bone and dentine mineral phase by determining a splitting factor (SF) or a crystallinity index (CI), respectively. These data can be combined with studies on the nanometer scale made with TEM. This latter technique,coupled with electron microdiffraction, provides determination of dimensions and shapes of individual bone and dentine apatite nanocrystals as well as of secondary minerals formed during diagenesis. It enables us to distinguish between heat,induced recrystallization processes and crystal growth in solution occurring during diagenesis. [source]

Neural Network Prediction of Biomass Digestibility Based on Structural Features

BIOTECHNOLOGY PROGRESS, Issue 2 2008
Jonathan P. O'Dwyer
Plots of biomass digestibility are linear with the natural logarithm of enzyme loading; the slope and intercept characterize biomass reactivity. The feed-forward back-propagation neural networks were performed to predict biomass digestibility by simulating the 1-, 6-, and 72-h slopes and intercepts of glucan, xylan, and total sugar hydrolyses of 147 poplar wood model samples with a variety of lignin contents, acetyl contents, and crystallinity indices. Regression analysis of the neural network models indicates that they performed satisfactorily. Increasing the dimensionality of the neural network input matrix allowed investigation of the influence glucan and xylan enzymatic hydrolyses have on each other. Glucan hydrolysis affected the last stage of xylan digestion, and xylan hydrolysis had no influence on glucan digestibility. This study has demonstrated that neural networks have good potential for predicting biomass digestibility over a wide range of enzyme loadings, thus providing the potential to design cost-effective pretreatment and saccharification processes. [source]