To provide prominent accessibility of fishmeal to the European population, the currently available, time- and cost-extensive feeding trials, which evaluate fish feed, should be replaced. The current paper reports on the development of a novel 3D culture platform, mimicking the microenvironment of the intestinal mucosa in vitro. The key requirements of the model include sufficient permeability for nutrients and medium-size marker molecules (equilibrium within 24 h), suitable mechanical properties (G' < 10 kPa), and close morphological similarity to the intestinal architecture. To enable processability with light-based 3D printing, a gelatin-methacryloyl-aminoethyl-methacrylate-based biomaterial ink is developed and combined with Tween 20 as porogen to ensure sufficient permeability. To assess the permeability properties of the hydrogels, a static diffusion setup is utilized, indicating that the hydrogel constructs are permeable for a medium size marker molecule (FITC-dextran 4 kg mol−1). Moreover, the mechanical evaluation through rheology evidence a physiologically relevant scaffold stiffness (G' = 4.83 ± 0.78 kPa). Digital light processing-based 3D printing of porogen-containing hydrogels results in the creation of constructs exhibiting a physiologically relevant microarchitecture as evidenced through cryo-scanning electron microscopy. Finally, the combination of the scaffolds with a novel rainbow trout (Oncorhynchus mykiss) intestinal epithelial cell line (RTdi-MI) evidence scaffold biocompatibility. 相似文献
A general kinetic method, based upon population balances of generating functions, is applied to the prediction of the microstructure and molecular size of non‐linear terpolymers obtained through the coordination polymerization of two monovinyl monomers and a non‐conjugated diene. A rather complex kinetic scheme involving crosslinking and long‐chain branching is considered. It is shown that even in these conditions it is possible to carry out the prediction of molecular size and mass distributions, sequence size distributions, and z‐average mean‐square radius of gyration of the polymers. The influence of some kinetic parameters on the properties of the products is studied, considering a homogeneous operation in a semi‐batch reactor. The used simulation method is able to predict these properties before and after gelation whenever it occurs.
We consider solutions of initial-boundary value problems for the heat equation on bounded domains in and their spatial critical points as in the previous paper [MS]. In Dirichlet, Neumann, and Robin homogeneous initial-boundary
value problems on bounded domains, it is proved that if the origin is a spatial critical point never moving for sufficiently
many compactly supported initial data being centrosymmetric with respect to the origin, then the domain must be centrosymmetric
with respect to the origin. Furthermore, we consider spatial zero points instead of spatial critical points, and prove some
similar symmetry theorems. Also, it is proved that these symmetry theorems hold for initial-boundary value problems for the
wave equation.
Received October 31, 1997; in final form February 3, 1998 相似文献
The metric sample space of Fréechet curves (Fréechet , 1934,1951,1961) is based on a generalization of regular curves that covers continuous curves in full generality. This makes it possible to deal with both smooth and non-smooth, even non-rectifiable geometric curves in statistical analysis. In the present paper this sample space is further extended in two directions that are relevant in practice: to incorporate information on landmark points in the curves and to impose invariance with respect to an arbitrary group of isometric spatial transformations. Properties of the introduced sample spaces of curves are studied, specially those concerning to the generation and representation of random curves by random functions.In order to provide measures of central tendency and dispersion of random curves, centroids and restricted centroids ofrandom curves are defined in a general metric framework, and methods for their consistent estimation are derived. 相似文献
The hexasaccharide (trimer) and tetrasaccharide (dimer) oligomers of hyaluronic acid were investigated by 1H and 13C high resolution Nuclear Magnetic Resonance. The dynamic behavior of the molecules and their complexation with copper(II) were analysed by 1H NMR relaxation studies. A specific site for the complexation of the tetrasaccharide with Cu2+ was demonstrated by analysis of the paramagnetic effect of the metal on non-selective proton relaxation rates. A model for the complex involving two molecules of the tetrasaccharide is proposed. 相似文献
The mechanisms that trigger the phototoxic response to 2-chlorophenothiazine derivatives are still unknown. To better understand the relationship between the molecular structure of halogenated phenothiazines and their phototoxic activity, their photophysics and photochemistry were studied in several alcohols. The photodestruction quantum yields were determined under anaerobic conditions using monochromatic light (313 nm). Absorption- and emission-spectroscopy, 1H- and 13C-NMR and GC-MS were used to characterize the photoproducts and reference compounds. An electron transfer mechanism had been previously proposed by Bunce et al . ( J. Med. Chem . 22 , 202–204) to explain the large difference between the photodestruction quantum yield of 2-chlorpromazine (φ = 0.46) and 2-chlorphenothiazine (φ = 0.20). According to these authors, the alkylamino chain transfers an electron to the phenothiazine moiety. Our results demonstrate that this mechanism is incorrect, because the photodestruction quantum yields of all chlorinated derivatives of this study are the same under the same conditions of solvent and irradiation wavelength. The quantum yield has no dependence on the 10-substituent, but it depends on the solvent. The percentage of each photoproduct, on the other hand, strongly depends on that substituent, but not very much on the solvent. Finally, it is demonstrated that the phototoxic effect of chlorinated phenothiazines is not related to the photodechlorination, although both processes share the same transient. 相似文献
This work is concerned with controlled Markov chains with finite state and action spaces. It is assumed that the decision
maker has an arbitrary but constant risk sensitivity coefficient, and that the performance of a control policy is measured
by the long-run average cost criterion. Within this framework, the existence of solutions of the corresponding risk-sensitive
optimality equation for arbitrary cost function is characterized in terms of communication properties of the transition law. 相似文献
The syntheses, structure, and inclusion properties of trinuclear boron compounds having a calix-like shape are described. The compounds have been obtained via self-assembly reactions between salicylaldehyde derivatives and 3-aminophenylboronic acid, whereby the formation of three N --> B coordination bonds favored the oligomerization. The products have high melting points (>370 degrees C), are stable to moisture, and have good solubility in organic solvents; the latter property is useful for host-guest recognition experiments. The structural analysis by X-ray diffraction revealed that diverse conformations are possible because of the presence of two different units of aromatic rims. A cone-cone (double-cone) conformation is observed for three of these compounds, while the remaining one has a cone-partial cone conformation. An analysis of the molecular packing showed that the molecules are stacked in columns in two different orientations in relation to the organization of the macrocycles when referred to the N-B bonds. The inclusion properties toward primary amines and ammonium chlorides were analyzed by titration experiments and monitored by UV spectroscopy, whereby association constants on the order of 10(2)-10(3) M(-1) were determined. 相似文献
Unprecedented 2-iminium chloride salts of 5,8-dihydro-2H-pyrido[3,2-e][1,3]thiazines derivatives (8) were easily synthesized in one step from the corresponding o-chloroformyl-1,4-dihydropyridine (2) and thiourea. The structural study has been carried out by X-ray crystallography and theoretical calculations at the B3LYP/6-31G* levels and reveal that the new salts exhibit appropriate structural features to behave as calcium channel modulators. 相似文献