Polyethylene glycol (PEG) chains with different lengths were covalently bonded to polypropylene membranes by means of RF plasma
polymerisation of acrylic acid (pp-Aac) followed by mono-amino PEG attachment in liquid phase. Two reactor configurations
were tested for the plasma deposition of ppAAc in order to obtain high retention of carboxylic groups in the deposited thin
films. A best configuration was assessed evaluating the membrane surface modifications by means of water droplet adsorption
time and contact angles measurements, attenuated total reflection (ATR) spectroscopy and X-ray photoelectron spectroscopy
(XPS) analysis. PEG chains were covalently bonded to the best plasma modified membranes and the resulting anti-fouling properties
were evaluated. 相似文献
Naringinase fromAspergillus niger shows -L-rhamnosidase and -D-glucosidase activity. The ratio of these enzymatic activities varies, depending on the protein concentration as well as thepH. The rhamnosidase activity is nearly independent of thepH in the range from 3 to 7, whereas glucosidase shows a distinct optimum which varies betweenpH4 andpH6 depending on its pretreatment. By gel filtration the enzyme complex can be separated into various oligomers, which are multiples of the smallest active subunit with a molecular weight of 95 000. The oligomers show either both enzymatic activities or mere rhamnosidase action. Protein fractions with glucosidase activity only could not be isolated. However in fractions with rhamnosidase activity only, the glucosidase activity could be restored by immobilisation. Glucosidase activity is related to the concentration of protein in solution, disappearing in very diluted solutions, where rhamnosidase is still active.Dedicated to Professor Dr.Karl Schlögl at the occasion of his 60th anniversary. 相似文献
Diphosphine 2,2′-bis(di-tert-butylphosphino)methyl)-1,1′-biphenyl (ditbi) is synthesised by the addition of to 2,2′-bis(bromomethyl)-1,1′-biphenyl, followed by deprotection with diethylamine. Treatment of [Rh2Cl2(1,5-cod)2], with ditbi gives [Rh2Cl2(1,5-cod)2(μ-ditbi)] (2) as confirmed by its X-ray crystal structure determination. Hydroformylation of 1-hexene using [Rh(acac)(CO)2]/ditbi as catalyst gave n- and iso-heptanal in a ratio of 1:1. 相似文献
Cellulases hydrolysing the interior parts of cellulose, also called endoglucanases, were immobilised in micro-immobilised enzyme reactors (μIMER) made of porous silicon with the purpose of investigating the use of such μIMERs for hydrolysis of cellodextrins and soluble cellulose derivatives. The endoglucanases Trichoderma reesei Cel 12A (TrCel 12A) and Bacillus agaradhaerens Cel 5A (BaCel 5A) were covalently coupled to the surface of a silicon microchip through Schiff base formation. For characterisation cellohexaose was used as substrate for the immobilised enzymes. The characteristics of the μIMER were investigated by studying the product formation when varying the concentration, flow-rate, temperature and pH of the substrate solution. Hydrolysis was performed in the μIMER connected on-line to a chromatographic system, where the products were separated and detected using high-performance anion exchange chromatography (HPAEC) coupled to pulsed amperometric detection (PAD). A comparison of the hydrolytic pattern between BaCel 5A and TrCel 12A was carried out and the results show that the two investigated endoglucanases give specific hydrolytic patterns in the products formed that provide important information about the enzymes. The μIMERs are robust and can be employed continuously over a period of at least several days. Moreover, on appropriate storage, no activity loss is seen after 60 days. The ability of the BaCel 5A containing μIMER to perform hydrolysis of derivatised cellulose was also investigated using carboxymethyl cellulose (CMC) as substrate. Separation and detection were carried out using size exclusion chromatography (SEC) with refractive index detection (RI). The results show that the μIMERs are robust and can be employed for on-line hydrolysis of both cellodextrins and derivatised cellulose of high molecular weight. 相似文献
When an ultrasonic examination is performed, a segmentation tool would often be very useful, either for the detection of pathologies, the early diagnosis of cancer or the follow-up of the lesions. Such a tool must be both reliable and accurate. However, because of the relatively reduced quality of ultrasound images due to the speckled texture, the segmentation of ultrasound data is a difficult task. We have previously proposed to tackle the problem using a multiresolution Bayesian region-based algorithm. For computation time purposes, a multiresolution version has been implemented. In order to improve the quality of the segmentation, we propose to perform the segmentation not only from the envelope image but to combine more information about the properties of the tissues in the segmentation process. Several acoustical parameters have thus been computed, either directly from the images or from the radio-frequency (RF) signal.
In a previous study, two parametric images were involved in the segmentation process. The parameter represented the integrated backscatter (IBS) and the mean central frequency (MCF), which is a measurement related to the attenuation of ultrasound waves in the media. In this study, parameters representative of the scattering conditions in the tissue are evaluated in the multiparametric segmentation process. They are extracted from the K-distribution (,b) and the Nakagami distribution (m,Ω) and are related to the local density of scatterers (,m), the size of the scatterers (b) and the backscattering properties of the medium (Ω).
The acoustical features are calculated locally on a sliding window. This procedure allows to built parametric mapping representing the particular characteristics of the medium. To test the influence of the acoustical parameters in the segmentation process, a set of numerical phantoms has been computed using the Field software developed by J.A. Jensen. Each phantom consists in two regions with two different acoustical properties: the density of scatterers and the scattering amplitude. From both the simulated RF signals and envelope images, the parameters have been computed; their relevance to represent a particular characteristic of the medium is evaluated. The segmentation has been processed for each phantom. The ability of each parameter to improve the segmentation results is validated. A agar–gel phantom has also been created, in order to test the accuracy of the parameters in conditions closer to the in vivo ultrasound imaging. This phantom contains four inclusions with different concentrations of silica. A B&K ultrasound device provides the RF data. The quantification of the segmentation quality is based on the rate of correctly classified pixels and it has been computed for all the parameters either from the field images or the phantom images. The large improvement in the segmentation results obtained reveals that the multiparametric segmentation scheme proposed in this study can be a reliable tool for the processing of noisy ultrasound data. 相似文献
Several calamitic reactive mesogens containing only two benzene rings in the molecular core and with or without lateral substitution by the methyl/methoxy groups have been designed and their mesomorphic behaviour was characterised. Depending on the molecular structure, some of the materials exhibit the nematic and the orthogonal smectic mesophases. The reactive mesogens are aimed for further design of the macromolecular materials like polysiloxane-based polymers and elastomers. Beyond the mesomorphic and structural properties, the electrorheological properties within the temperature range of the nematic and smectic A mesophases were studied with and without applied electric field for the selected reactive mesogen. The increase of viscosity was found not to be higher than three times under applied electric field strength of 2 kV/mm. The mesomorphic, structural and rheological properties of the newly designed reactive mesogens are discussed in order to contribute to better understanding of the molecular architecture–nano-organisation properties relationship of such mesogenic materials. 相似文献
Two kilns, one of which collapsed during firing cycle together with its entire pottery load, have been excavated at the Egnazia
site in Southern Italy.
To understand the reason for the collapse, ‘Broad Line’ typology pottery finds were analysed by complementary analytical techniques.
Analytical results not only suggest as cause of collapse sudden overheating in kiln due to uncontrolled increases in temperature,
but also indicate a good technological cycle from the recovery of raw materials to the manufacturing and firing process, which
tends to disprove the common assumption of non-professional production. 相似文献