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881.
Ranieri Bizzarri Federica Chiellini Christopher K. Ober W. Mark Saltzman Roberta Solaro Emo Chiellini 《Macromolecular Symposia》2003,197(1):303-314
A new class of malolactonate polymers and copolymers with a wide range of lateral chain structures were synthesized by anionic ring opening polymerization of alkyl malolactonate monomers. The monomers were prepared in good yields according to established procedures. Final macromolecular and thermal characteristics were in agreement with the designed monomer structures. Molecular weights in the range 4-20 kD were attained, as a result of chain transfer reactions. Representative polymeric compounds displayed stability up to 200 °C. Many of the obtained poly(alkyl malolactonate)s were able to sustain and promote with 3T3 murine fibroblasts adhesion and proliferation onto their surface. 相似文献
882.
Cryogels are a class of macroporous, interconnective hydrogels polymerized at sub-zero temperatures forming mechanically robust, elastic networks. In this review, latest advances of cryogels containing mainly glycosaminoglycans (GAGs) or composites of GAGs and other natural or synthetic polymers are presented. Cryogels produced in this way correspond to the native extracellular matrix (ECM) in terms of both composition and molecular structure. Due to their specific structural feature and in addition to an excellent biocompatibility, GAG-based cryogels have several advantages over traditional GAG-hydrogels. This includes macroporous, interconnective pore structure, robust, elastic, and shape-memory-like mechanical behavior, as well as injectability for many GAG-based cryogels. After addressing the cryogelation process, the fabrication of GAG-based cryogels and known principles of GAG monomer crosslinking are discussed. Finally, an overview of specific GAG-based cryogels in biomedicine, mainly as polymeric scaffold material in tissue regeneration and tissue engineering-related controlled release of bioactive molecules and cells, is provided. 相似文献
883.
V. Alastrué M.A. Martínez M. Doblaré A. Menzel 《Journal of the mechanics and physics of solids》2009,57(1):178-82
A fully three-dimensional anisotropic elastic model for vascular tissue modelling is presented here. The underlying strain energy density function is assumed to additively decouple into volumetric and deviatoric contributions. A straightforward isotropic neo-Hooke-type law is used to model the deviatoric response of the ground substance, whereas a micro-structurally or rather micro-sphere-based approach will be employed to model the contribution and distribution of fibres within the biological tissue of interest. Anisotropy was introduced by means of the use of von Mises orientation distribution functions. Two different micro-mechanical approaches—a, say phenomenological, exponential ansatz, and a worm-like-chain-based formulation—are applied to the micro-fibres and illustratively compared. The passage from micro-structural contributions to the macroscopic response is obtained by a computational homogenisation scheme, namely numerical integration over the surface of the individual micro-spheres. The algorithmic treatment of this integration is discussed in detail for the anisotropic problem at hand, so that several cubatures of the micro-sphere are tested in order to optimise the accuracy at reasonable computational cost. Moreover, the introduced material parameters are identified from simple tension tests on human coronary arterial tissue for the two micro-mechanical models investigated. Both approaches are able to recapture the experimental data. Based on the identified sets of parameters, we first discuss a homogeneous deformation in simple shear to evaluate the models’ response at the micro-structural level. Later on, an artery-like two-layered tube subjected to internal pressure is simulated by making use of a non-linear finite element setting. This enables to obtain the micro- and macroscopic responses in an inhomogeneous deformation problem, namely a blood vessel representative boundary value problem. The effect of residual stresses is additionally included in the model by means of a multiplicative decomposition of the deformation gradient tensor which turns out to crucially affect the simulation results. 相似文献
884.
Summary A simple rapid method has been developed for the determination of flumequine and oxolinic acid in edible animal tissues. Analytes
are extracted from the sample matrix using dichloromethane in neutral conditions, then back-extracted in 0.01 M sodium hydroxide
and determined by reversed-phase liquid chromatography with fluorimetric detection. The method has been applied to pork, salmon
and chicken muscle with recoveries higher than 77% in all matrices. The detection limits achieved (<1 μg kg−1) allow the determination of these drugs at a residue level far below their MRL Moreover, some variables that may affect the
spiking process have been studied. 相似文献
885.
O. V. Angel'skii A. G. Ushenko S. B. Ermolenko D. N. Burkovets V. P. Pishak Yu. A. Ushenko O. V. Pishak 《Journal of Applied Spectroscopy》2000,67(5):919-923
A polarization-phase method of visualization of optically anisotropic inhomogeneities of biotissues, which is based on multifractal modeling of biotissue properties, is proposed. An algorithm for obtaining topograms of orientations of the fractal domains of a visualized architectonic net of a biotissue is developed and realized experimentally. 相似文献
886.
I. Papadakis Christophe R. Quétel Philip D. P. Taylor Paul De Bièvre 《Accreditation and quality assurance》2000,5(5):198-204
Metrological certification through a primary method of measurement and how it can be achieved is demonstrated in this paper,
using the example of re-certification of cadmium and lead content in a biological material, the Bureau Communataire de Reference,
reference material CRM-278R mussel tissue. The measurement method used was isotope dilution in combination with inductively
coupled plasma mass spectrometry. Microwave digestion was applied to the samples prior to the measurements. A detailed uncertainty
budget was evaluated according to the International Organisation of Standardisation, Guide to the Expression of Uncertainty
and EURACHEM Guide, resulting in an expanded uncertainty.
Received: 20 August 1999 / Accepted: 3 January 2000 相似文献
887.
Evaluating the mechanical behavior of arterial tissue using digital image correlation 总被引:5,自引:0,他引:5
In this study, digital image correlation (DIC) was adopted to examine the mechanical behavior of arterial tissue from bovine
aorta. Rectangular sections comprised of the intimal and medial layers were excised from the descending aorta and loaded in
displacement control uniaxial tension up to 40 percent elongation. Specimens of silicon rubber sheet were also prepared and
served as a benchmark material in the application of DIC for the evaluation of large strains; the elastomer was loaded to
50 percent elongation. The arterial specimens exhibited a non-linear hyperelastic stress-strain response and the stiffness
increased with percent elongation. Using a bilinear model to describe the uniaxial behavior, the average minor and major elastic
modulii were 192±8 KPa and 912±40 KPa, respectively. Poisson's ratio of the arterial sections increased with the magnitude
of axial strain; the average Poisson's ratio was 0.17±0.02. Although the correlation coefficient obtained from image correlation
decreased with the percent elongation, a correlation coefficient greater than 0.8 was achieved for the tissue experiments
and exceeded that obtained in the evaluation of the elastomer. Based on results from this study, DIC may serve as a valuable
method for the determination of mechanical properties of arteries and other soft tissues. 相似文献
888.
Mohamed A. Taher A. A. Loay Mostafa Gouda Safaa A. Limam Mohamed F. M. Abdelkader Samah O. Osman Mohammad Fikry Esmat F. Ali Sayed. Y. Mohamed Hoda A. Khalil Diaa O. El-Ansary Sherif F. El-Gioushy Hesham S. Ghazzawy Aly M. Ibrahim Mahmoud F. Maklad Mohamed A. Abdein Dalia M. Hikal 《Molecules (Basel, Switzerland)》2022,27(8)
Peaches are grown in many Egyptian orchards for local and global fresh market sales. The interior fruit tissue breakdown (IFTB), often resulting in decayed peaches, is a severe problem during marketing. Therefore, to minimize FTB of peaches, in this study, gum arabic (GA) and polyvinylpyrrolidone (PVP) were mixed with different concentrations of salicylic acid (SA) (0, 1, and 2 mM) and were applied as edible coating to extend the shelf life of peach fruits. Mature peaches were selected and harvested when peaches reached total soluble solid content (SSC: 8.5%) and fruit firmness of about 47 N. Fruits were coated and stored at room temperature (26 ± 1 °C and air humidity 51 ± 1%) for 10 days during two seasons: 2020 and 2021. Fruit coated with GA/PVP-SA 2 mM showed a significant (p < 0.05) inhibition in degrading enzyme activities (CWDEs), such as lipoxygenase (LOX), cellulase (CEL), and pectinase (PT), compared to uncoated and coated fruits during the shelf-life period. Hence, cell wall compartments were maintained. Consequently, there was a reduction in browning symptoms in fruits by inhibiting polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) activities. Thus, the fruit skin browning index showed almost no symptoms. The lipid peroxidation process and ionic permeability declined as well. The result suggests that, by applying GA/PVP-SA 2 mM as an edible coating, fruit tissue breakdown can be minimized, and the shelf life of peach can be extended up to 10 days without symptoms of tissue breakdown. 相似文献
889.
Yue Xu Hang Zhang Nannan Li Wen Ma Shuyuan Wang Jianguo Sun Baoxue Yang 《Molecules (Basel, Switzerland)》2022,27(8)
Urea transporter (UT) inhibitors are a class of promising novel diuretics that do not cause the imbalance of Na+, K+, Cl−, and other electrolytes. In our previous studies, 25a, a promising diuretic candidate inhibiting UT, was discovered and showed potent diuretic activities in rodents. Here, a sensitive liquid chromatography–tandem mass spectrometry method for the quantitation of 25a in rat plasma, urine, feces, bile, and tissue homogenates was developed and validated to support the preclinical pharmacokinetic studies. The tissue distribution, excretion, and plasma protein binding were investigated in rats. After a single oral dose of 25a at 25, 50, and 100 mg/kg, the drug exposure increased linearly with the dose. The drug accumulation was observed after multiple oral doses compared to a single dose. In the distribution study, 25a exhibited a wide distribution to tissues with high blood perfusion, such as kidney, heart, lung, and spleen, and the lowest distribution in the brain and testis. The accumulative excretion rate of 25a was 0.14%, 3.16%, and 0.018% in urine, feces, and bile, respectively. The plasma protein binding of 25a was approximately 60% in rats and 40% in humans. This is the first study on the preclinical pharmacokinetic profiles of 25a. 相似文献
890.
乳腺肿瘤周边组织的拉曼光谱研究 总被引:5,自引:5,他引:0
使用REMSHAW显微共焦拉曼光谱仪测量了40例手术切除乳腺肿瘤周边(肿块边约5 mm)组织的拉曼光谱.通过对浸润性导管癌、乳腺增生、纤维腺瘤等乳腺肿瘤周边组织的拉曼光谱分析,发现不同乳腺肿瘤周边组织的拉曼光谱有显著差异.这些差异在肿瘤诊断中,可作为乳腺癌和其他乳腺肿瘤拉曼光谱的特征,为乳腺疾病诊断提供依据.乳腺肿瘤周边组织的拉曼光谱对乳腺肿瘤诊断具有重要的价值. 相似文献