Metabolic regulation of collagen gel contraction by porcine aortic valvular interstitial cells

Despite a high incidence of calcific aortic valve disease in metabolic syndrome, there is little information about the fundamental metabolism of heart valves. Cell metabolism is a first responder to chemical and mechanical stimuli, but it is unknown how such signals employed in valve tissue engineering impact valvular interstitial cell (VIC) biology and valvular disease pathogenesis. In this study porcine aortic VICs were seeded into three-dimensional collagen gels and analysed for gel contraction, lactate production and glucose consumption in response to manipulation of metabolic substrates, including glucose, galactose, pyruvate and glutamine. Cell viability was also assessed in two-dimensional culture. We found that gel contraction was sensitive to metabolic manipulation, particularly in nutrient-depleted medium. Contraction was optimal at an intermediate glucose concentration (2 g l⁻¹) with less contraction with excess (4.5 g l⁻¹) or reduced glucose (1 g l⁻¹). Substitution with galactose delayed contraction and decreased lactate production. In low sugar concentrations, pyruvate depletion reduced contraction. Glutamine depletion reduced cell metabolism and viability. Our results suggest that nutrient depletion and manipulation of metabolic substrates impacts the viability, metabolism and contractile behaviour of VICs. Particularly, hyperglycaemic conditions can reduce VIC interaction with and remodelling of the extracellular matrix. These results begin to link VIC metabolism and macroscopic behaviour such as cell–matrix interaction.     

Spatial statistics of carbon nanotube polymer composites

Dispersion, distribution, and alignment of carbon nanotubes (CNT) in polycarbonate (PC) composites are quantified by means of statistical analysis of transmission electron microscopy (TEM) images. The analysed images originate from samples with 0.875 and 2 wt% CNT, processed by compression and injection moulding, respectively. The composites exhibit different microstructures with different electrical properties, depending on the processing parameters. By means of stereological approaches for projections of three dimensional fibre systems the CNT contents within the TEM samples are estimated. The tendency of CNT clustering as well as characteristic distances between the CNT and CNT clusters are quantified by evaluation of morphological functions. Furthermore, a correlation function is introduced to obtain a quantitative measure of CNT clustering within the isotropic compression moulded samples. For the injection moulded samples the correlation function is used to derive local orientation factors. The results underline that clustering of CNT can enhance and alignment of tubes can reduce electrical conductivity.     

Going beyond histology. Synchrotron micro-computed tomography as a methodology for biological tissue characterization: from tissue morphology to individual cells

Current light microscopic methods such as serial sectioning, confocal microscopy or multiphoton microscopy are severely limited in their ability to analyse rather opaque biological structures in three dimensions, while electron optical methods offer either a good three-dimensional topographic visualization (scanning electron microscopy) or high-resolution imaging of very thin samples (transmission electron microscopy). However, sample preparation commonly results in a significant alteration and the destruction of the three-dimensional integrity of the specimen. Depending on the selected photon energy, the interaction between X-rays and biological matter provides semi-transparency of the specimen, allowing penetration of even large specimens. Based on the projection-slice theorem, angular projections can be used for tomographic imaging. This method is well developed in medical and materials science for structure sizes down to several micrometres and is considered as being non-destructive. Achieving a spatial and structural resolution that is sufficient for the imaging of cells inside biological tissues is difficult due to several experimental conditions. A major problem that cannot be resolved with conventional X-ray sources are the low differences in density and absorption contrast of cells and the surrounding tissue. Therefore, X-ray monochromatization coupled with a sufficiently high photon flux and coherent beam properties are key requirements and currently only possible with synchrotron-produced X-rays. In this study, we report on the three-dimensional morphological characterization of articular cartilage using synchrotron-generated X-rays demonstrating the spatial distribution of single cells inside the tissue and their quantification, while comparing our findings to conventional histological techniques.     

Rubber-Wood Composites from Chemically Modified Olive Husk Powder and Carboxylated Nitrile Butadiene Rubber: Cure Characteristics,Tensile Behavior,and Morphological Studies

Abstract

Olive husk powder (OHP) was chemically treated using sodium hydroxide, silane coupling agent, and stearic acid. The treatment was performed to improve both the dispersion of the OHP as well as the degree of interactions between the filler and the matrix. The treated OHP was mixed with carboxylated nitrile butadiene rubber (XNBR) using a lab-scale two roll mill. The potential of the treated filler on the cure characteristics and tensile performance of the fabricated samples was monitored. We found that the cure characteristics and the tensile properties were increased after the incorporation of the modified OHP into the matrix. The interactions between the treated OHP and the XNBR were inspected by attenuated total reflectance infrared spectroscopy (ATR-IR). The spectra revealed the emergence of a new peak at 1770 cm^?1. This suggests the occurrence of a condensation reaction between the modified OHP and the carboxylic group of the XNBR. The morphology of the fractured surfaces of the samples was inspected under scanning electron microscope (SEM). The images revealed an improved filler dispersion and better degree of interaction with the matrix after chemical modification.     

The perfectly matched layer as lateral boundary infinite-difference transmission-line analysis

Using a perfectly matched layer (PML) as lateral boundary in waveguide analysis introduces artificial modes and other unexpected effects. This paper presents results of a finite-difference frequency-domain approach and an analytical investigation of the PML's capability to simulate the lateral open space, including an accuracy estimation. A criterion how to detect the desired modes out of the mode spectrum is also given. The findings are verified for a coplanar waveguide radiating into the substrate     

Graph-regularized 3D shape reconstruction from highly anisotropic and noisy images

Analysis of microscopy images can provide insight into many biological processes. One particularly challenging problem is cellular nuclear segmentation in highly anisotropic and noisy 3D image data. Manually localizing and segmenting each and every cellular nucleus is very time-consuming, which remains a bottleneck in large-scale biological experiments. In this work, we present a tool for automated segmentation of cellular nuclei from 3D fluorescent microscopic data. Our tool is based on state-of-the-art image processing and machine learning techniques and provides a user-friendly graphical user interface. We show that our tool is as accurate as manual annotation and greatly reduces the time for the registration.     

Petrov-Galerkin finite element model for compressible flows

A Petrov-Galerkin method for the solution of the compressible Euler and Navier-Stokes equations is presented. It is based on the introduction of an anisotropic blancing diffusion in the direction of the local direction of propagation of the scalar variables. The local direction in which the anisotropic diffusion is introduced is uniquely determined, and the magnitude of the balancing diffusion is automatically calculated locally using a criterion that is optimal for one-dimensional transport equations. The algorithm has been implemented using four-noded bilinear elements with forward Euler and second-order Runge-Kutta methods of integration in time. Several applications are presented and show the stability and approximation properties of the method.     

The frequency behavior of InGaAs-AlInAs metal-semiconductor-metalphotodetectors at low bias voltages for data communication applications

The authors have fabricated lattice matched InGaAs/AlInAs metal-semiconductor-metal photodetectors on InP. The detectors have very low dark currents, low capacitance, and good responsivity, corresponding to at least 95% internal collection efficiency. It is demonstrated that multigigahertz bandwidths, as measured in the frequency domain, are achievable at typical logic-level bias voltages, and that therefore these detectors are viable candidates for long-wavelength data communication applications