Here we present a facile method to fabricate microporous hydrogel scaffolds that can be functionalized with a chemokine gradient. These scaffolds allow studying cellular responses in a 3D environment. 相似文献
The isomerization of perindopril has been investigated using dynamics chromatography and an unified equation introduced by Trapp that was based on stochastic and theoretical plate models to determine the energies. The isomerization rate constants and Gibbs activation energies of isomerization are directly calculated from chromatographic peak parameters, i.e., retention times of the inter-converting species, peak width at half height, and relative plateau height. From the rate constant \( k_{1}^{ue} (T) \), measured at variable temperatures, the kinetic eyring activation parameters ΔG#, ΔH# and ΔS# of isomerization of perindopril were obtained. By variation of the flow rate of the mobile phase, the expected independence of the isomerization barrier from the chromatographic time scale was demonstrated for the first time. The relationships between peak shape and chromatographic conditions, such as flow rate, temperature, pH, organic modifier, and β-cyclodextrin, such as an additive, were investigated. In addition, an NMR investigation on perindopril was described.
In this paper, two speech enhancement algorithms (SEAs) based on spectral subtraction (SS) principle have been evaluated for bilateral cochlear implant (BCI) users. Specifically, dual-channel noise power spectral estimation algorithm using power spectral densities (PSD) and cross power spectral density (CPSD) of the observed signals was studied. The enhanced speech signals were obtained using either Dual Channel Non Linear Spectral Subtraction ‘DC-NLSS’ or Dual-Channel Multi-Band Spectral Subtraction ‘DC-MBSS’ algorithms. For performance evaluation, some objective speech assessment tests relying on Perceptual Evaluation of Speech Quality (PESQ) score and speech Itakura-Saito (IS) distortion measurement were performed to fix the optimal number of frequency band needed in DC-MBSS algorithm. In order to evaluate the speech intelligibility, subjective listening tests were assessed with 50 normal hearing listeners using a specific BCI simulator and with three deafened BCI patients. Experimental results, obtained using French Lafon database corrupted by an additive babble noise at different Signal-to-Noise Ratios (SNR), showed that DC-MBSS algorithm improves speech understanding better than DC-NLSS algorithm for single and multiple interfering noise sources. 相似文献
Different functions describing matrix-fracture transfer were tested for counter-current capillary imbibition interaction.
The recovery curves obtained from capillary imbibition experiments were used to fit the transfer functions. The exponential
coefficients yielding the best fit to the experimental data were obtained and correlated to the effective parameters such
as viscosity, IFT, matrix length and diameter, matrix permeability and porosity, and wettability using multivariable regression
analysis. In order to obtain the recovery curves, experiments were conducted on Berea sandstone and Indiana limestone samples.
Cylindrical samples with different shape factors were obtained by cutting the plugs 1, 2.5, and 5 cm in diameter and 2.5,
5, and 10 cm in length. All sides were coated with epoxy except one end. More than fifty static imbibition experiments were
carried out on vertically and horizontally situated samples where the imbibition took place upward and lateral directions,
respectively. Brine–air, brine–kerosene, brine–mineral oil, and surfactant solution–mineral oil pairs were used as fluids.
For many matrix shape factors (especially longer and small diameter ones), dividing the recovery curve into three parts were
needed as the early, intermediate, and late times, which are typically distinguished by the time required for the imbibition
front to reach the closed boundary at the end of the core. Correlations among the exponential coefficients and rock/fluid
properties were developed. It was observed that different rock/fluid properties and transfer mechanisms (capillary imbibition
and gravity drainage) govern the process for each part. Hence, the analyses done in this study were useful not only for developing
explicit transfer functions but also identifying the physics of the counter-current imbibition recovery. 相似文献
Fish are an important human food with increasing consumption in recent decades. Diet is the main route of exposure to heavy metals for human health. For this reason, many studies have been performed on the pollution by heavy metals in different species of fish. Our main objective was to evaluate the pollution by trace metals (Zn, Cu, Pb, and Cd) in sardine muscles collected from the bay of Boumerdés (Algeria). Flame atomic absorption spectroscopy (AAS) was used for the quantification of Cu and Zn. The quantification of Cd and Pb was achieved by graphite furnace (GF) AAS. The analysis revealed the presence of metal trace elements in the muscles of species at concentrations below the thresholds established by national and international regulations. 相似文献
A series of 3-(N-substituted thiocarbamoyl)hydrazino-1,2,4-triazino[5,6-b]indole derivatives 3–22 has been synthesized and evaluated for in vitro antimicrobial activity. Although some of the products displayed significant activity against Staphylococcus aureus, Escherichia coli and Candida albicans, their bactericidal and bacterostatic potencies were lower than that of penicillin G. The structure of the products was assigned upon the basis of their infrared, 1H-nmr and 13C-nmr spectra. 相似文献
When high resolution convection schemes are used for discretizing chemical species mass balance equations, the mass fractions are not guaranteed to add to one. We show that a proposed remedy called χ —scheme (Darwish and Moukalled, Comput. Methods Appl. Mech. Engrg. 192 (2003): 1711) will degrade to a diffusive first‐order scheme when a chemical species vanishes from the mixture, for example, because of chemical reactions. We propose an improvement to the χ ‐scheme to overcome this problem. Furthermore, a computationally efficient alternative scheme is proposed and evaluated with several examples, to quantify the improvements in the accuracy and the computational time. Published 2013. This article is a U.S. Government work and is in the public domain in the USA. 相似文献
Small micellar casein particles, so-called submicelles, were obtained by removing colloidal calcium phosphate from native casein by adding sodium polyphosphate. Aqueous submicelle suspensions were characterized using light scattering and rheology as a function of concentration and temperature. The casein submicelles behave like soft spheres that jam at a critical concentration (C(c)) of about 100 g L(-1). The viscosity does not diverge at C(c), but increases sharply, similarly to that of multiarm star polymers. C(c) increases weakly with increasing temperature, which leads to a strong decrease of the viscosity close to and above C(c). Concentrated submicelle suspensions show strong shear-thinning above a critical shear rate and the shear stress becomes independent of the shear rate. The critical shear rates at different temperatures and concentrations are inversely proportional to the zero-shear viscosity. At much higher shear rates, the shear stress fluctuates strongly in time indicating inhomogeneous flow. The frequency dependence of casein submicelle suspensions is characterized by elastic behavior at high frequencies (concentrations) and viscous behavior at low frequencies (concentrations). 相似文献
Single crystals of Nd5(AsO3)4Cl3 (monoclinic, P2/n, Z = 2, a = 1026.0(1), b = 543.35(3), c = 1400.2(1) pm, β = 93.48(1)°) were obtained from the reaction of Nd2O3, As2O3 and NaCl in a sealed silica ampoule. In the crystal structure the Nd3+ ions are linked by AsO33? groups into layers that alternate with layers of Cl? ions. Two of the three crystallographically different Nd3+ ions are coordinated by eight oxygen atoms, the third one has four oxygen and four chlorine atoms as neighbours. 相似文献