Completely reducible hypersurfaces in a pencil

We study completely reducible fibers of pencils of hypersurfaces on Pn and associated codimension one foliations of Pn. Using methods from theory of foliations we obtain certain upper bounds for the number of these fibers as functions only of n. Equivalently this gives upper bounds for the dimensions of resonance varieties of hyperplane arrangements. We obtain similar bounds for the dimensions of the characteristic varieties of the arrangement complements.     

Combined laser/sol-gel synthesis of calcium silicate coating on Ti-6Al-4V substrates for improved cell integration

New studies have shown that tricalcium silicate powder is a bioactive material and can encourage bone-implant integration. This paper reports the synthesis of Ca₂SiO₄ coating on Ti-6Al-4V samples by laser irradiation under submerged conditions. The results of using a 160-1500 LDL 1.5 kW diode laser (rectangular spot = 2.5 mm × 3.5 mm, λ = 808 and 940 nm with equal intensities) is reported. A number of experiments were carried out varying laser parameters, such as scanning speed and laser power. Coatings are evaluated in terms of microstructure, elemental composition (XRD), SEM and wettability. The in vitro biocompatibility of the samples is investigated by monitoring 2T3 osteoblast cell growth on the samples.     

Cell vertex finite volume discretizations in three dimensions

The cell vertex method is generalized to three dimensions. It is proved that there exists a one-parameter family of eight-point three-dimensional methods with second-order truncation error on parallelepipeds. Using different triangulations of control volume faces, various finite volume methods are derived. Some of these are identified as members of the aforementioned one-parameter family and may be regarded as second-order upwind schemes. A Fourier analysis is used to investigate the spectral properties of these discretizations. Numerical experiments illustrate that second-order global accuracy is achieved on parallelepiped grids, as suggested by the theory. Randomly perturbed, stretched, sheared meshes are used to test these methods to destruction. It is found that upwinding improves both the accuracy on distorted meshes and the spectrum of the discretization.     

Enhanced fibroblast cell adhesion on Al/Al2O3 nanowires

Biological cells stick together via transmembrane proteins, which are linked to receptor molecules of the extracellular matrix (ECM). This specific biochemical adhesion plays a leading role in many cellular processes, among them cell differentiation, morphogenesis, and wound healing. Various medical applications require endogen cells to bind to an exogene substrate as in the case of an implant. Coatings with proteins that naturally belong to the ECM are known to enhance the cell adhesion. However, the choice of inorganic materials, which promote cell adhesion, is limited. Here, we report on a new engineered surface composed of Al/Al₂O₃ bi-phasic nanowires (NWs), which promotes the adhesion of fibroblast cells. Fibroblasts grow well on this inorganic layer and keep proliferating. Using the cell monolayer rheology (CMR) technique, we show that the adhesion of fibroblasts on Al/Al₂O₃ NWs is comparable to fibronectin coated surfaces. To our knowledge, this is one of the strongest cell adhesions on an inorganic surface, which has been reported on so far, since it compares to bio-organic layers such as fibronectin.     

Cellular automata models of tumour natural shrinkage

In this paper we present three dimensional cellular automata models for tumour growth, with a focus on the tumour’s natural shrinkage caused by the removal of the dead cells’ mortal remains. The significance of this phenomenon for the resulting volume of the in silico tumour is shown. Two algorithms are presented, one using the chain shifting approach for tumour expansion and shrinkage and another improving the performance of the chain shifting approach. Simulations are validated against the experimental results.     

Spatial arrangements of dorsal root ganglion cells after sciatic nerve crush

The present study explores 3D spatial arrangements of the A- and B-cells within the fifth lumbar dorsal root ganglion (DRG) of rat in order to test for differences after sciatic nerve crush (SNC). The pair correlation and cross-correlation functions were estimated through counting dipole probes superimposed on DRG sections. The data showed that the A- and B-cells were clustered at distances below 40 and 35 μm in sham-operated animals, respectively. These values were 35 and 25 μm in SNC animals. Beyond these distances, the cells of the control group were arranged neither clustered nor repulsed. The A- and B-cells showed a negative correlation (repulsion) at r = 270–290 μm and r = 100 in SNC ganglions, respectively. The plot of the cross-correlation function showed that the first maximum curve was r = 51 μm and 41 μm in sham-operated and SNC rats, respectively. The other differences were seen at r = 51–61 μm and r = 165 μm between cross-covariance of the cells. The “degree of order” for the A- and B-cells showed no significant difference and the low values of the two groups indicated the random distribution of cells in them.

Conclusion

The obtained data revealed that cellular spatial patterns in the dorsal root ganglion of the sciatic nerve crush were changed.     

Evaluating cell migration in vitro by the method based on cell patterning within microfluidic channels

Cell migration is an early-stage and critical step for cancer metastasis. The most common approach to monitor this process is wound-healing assay. However, this traditional method has some unavoidable limitations. We observed that simply scratching the monolayer of cultured cells might cause local cell damage around the injury line. The cells along the scratched border seemed to be irritated and exhibited abnormal distribution of cytoskeleton reassembly with protruding "cell islands" and "pseudopodia" during wound healing, which might potentially affect the assessment of cell migration behavior. Herein, we applied a microfluidic device that mechanically constrained cells seeded in a designed pattern inside microchannels, and monitored cell movement in a way of mimicking the natural microenvironment of cancerous tissues. We illustrated the capacity of this simple method to probe cellular migration behaviors and to screen some biological active agents that reflected in their influence on cellular motility.     

Centrifugal countercurrent chromatography to elucidate surface differences of adipose tissue-derived stem cells

The current methods of isolation of adipose tissue-derived stem cells result in a heterogeneous population that might interfere with their differentiation potential and makes it difficult to compare the results between different groups. Partition in aqueous two-phase systems is one of the few techniques that separate cells on the basis of surface properties, gentle enough to isolate fragile cell types in isotonic conditions without altering their structure, and can be easily scaled. In this study, stem cells isolated from human adipose tissue seeded and expanded in vitro were fractionated by using centrifugal countercurrent distribution in an aqueous two-phase system. The separated subpopulations revealed the high heterogeneity of adipose tissue-derived stem cell samples. Comparative partition analyses showed that aging induces a loss of heterogeneity, which is not due to a loss of cell viability associated to age. The phosphatidylserine externalization, an apoptotic feature, is the main factor in cell partition that results in a decreased hydrophobicity of the cell surface. This procedure may be suitable for separating adipose tissue-derived stem cell populations enriched in some functional and/or structural surface characteristics. The possibility of a very effective separation of different subpopulations in opposite phases would be an interesting development of the method.