Nanocomposite Hydrogels as Platform for Cells Growth,Proliferation, and Chemotaxis

The challenge of mimicking the extracellular matrix with artificial scaffolds that are able to reduce immunoresponse is still unmet. Recent findings have shown that mesenchymal stem cells (MSC) infiltrating into the implanted scaffold have effects on the implant integration by improving the healing process. Toward this aim, a novel polyamidoamine‐based nanocomposite hydrogel is synthesized, cross‐linked with porous nanomaterials (i.e., mesoporous silica nanoparticles), able to release chemokine proteins. A comprehensive viscoelasticity study confirms that the hydrogel provides optimal structural support for MSC infiltration and proliferation. The efficiency of this hydrogel, containing the chemoattractant stromal cell‐derived factor 1α (SDF‐1α), in promoting MSC migration in vitro is demonstrated. Finally, subcutaneous implantation of SDF‐1α‐releasing hydrogels in mice results in a modulation of the inflammatory reaction. Overall, the proposed SDF‐1α‐nanocomposite hydrogel proves to have potential for applications in tissue engineering.     

An adaptive image watermarking algorithm based on perceptual model

An adaptive image watermarking algorithm based on Watson＇s perceptual model is proposed in this paper. The proposed watermarking algorithm fully considers image regional characteristic. First, the cover image is divided into different smooth regions according to its gray value. Then watermark adjustment factors of those different regions are calculated respectively based on Watson＇s perceptual model. The watermark is embedded by the adjustment factors at last. Experiments show that the proposed algorithm has excellent imperceptibility and has little influence upon the eigenvalue of the cover image.     

On the Discrete Maximum Principle for the Beltrami Color Flow

We analyze the discrete maximum principle for the Beltrami color flow. The Beltrami flow can display linear as well as nonlinear behavior according to the values of a parameter β, which represents the ratio between spatial and color distances. In general, the standard schemes fail to satisfy the discrete maximum principle. In this work we show that a nonnegative second order difference scheme can be built for this flow only for small β, i.e. linear-like diffusion. Since this limitation is too severe, we construct a novel finite difference scheme, which is not nonnegative and satisfies the discrete maximum principle for all values of β. Numerical results support the analysis.

Numerical study of 2024 T3 aluminum plates subjected to impact and perforation

The paper describes a work focused on the process of perforation of aluminum sheet. A numerical investigation has been carried out to analyze in details the perforation process subjected to normal impact by different nose shapes of projectiles. The perforation process has been simulated by the application of 3D analysis using IMPACT dynamic FE program suite. The comparison on failure modes depending on the projectile nose shape have been studied and evaluated. An appropriate constitutive relation was applied to describe the material behavior of the aluminum sheet. The study covered different failure modes including petalling, plug ejection and circumference necking of perforated aluminum sheet according to different level of impact velocity ranging from 100 m/s to 600 m/s. In this investigation, a special attention will be given on the deformation and failure.     

Therapeutic Advances in Gut Microbiome Modulation in Patients with Inflammatory Bowel Disease from Pediatrics to Adulthood

There is mounting evidence that the gut microbiota plays an important role in the pathogenesis of inflammatory bowel disease (IBD). For the past decade, high throughput sequencing-based gut microbiome research has identified characteristic shifts in the composition of the intestinal microbiota in patients with IBD, suggesting that IBD results from alterations in the interactions between intestinal microbes and the host’s mucosal immune system. These studies have been the impetus for the development of new therapeutic approaches targeting the gut microbiome, such as nutritional therapies, probiotics, fecal microbiota transplant and beneficial metabolic derivatives. Innovative technologies can further our understanding of the role the microbiome plays as well as help to evaluate how the different approaches in microbiome modulation impact clinical responses in adult and pediatric patients. In this review, we highlight important microbiome studies in patients with IBD and their response to different microbiome modulation therapies, and describe the differences in therapeutic response between pediatric and adult patient cohorts.     

Thermal properties and enthalpy relaxation of tyrosine-derived polyarylates

Sixteen degradable, tyrosine-derived polyarylates with well-defined chemical structures were used to study the effect of polymer structure on the glass transition temperature and enthalpy relaxation kinetics (physical aging). These polyarylates compose a model system where the number of methylene groups present in either the pendent chain or the polymer backbone can be altered independently and in a systematic fashion. Quantitative differential scanning calorimetry was employed to measure the glass transition temperature and the enthalpy relaxation kinetics. Correlations between these material properties and the polymer structure were established. The glass transition temperature of this family of polymers ranged from 13 to 78°C. The addition of methylene groups to either the pendent chain or the polymer backbone made a fairly constant contribution to lowering the glass transition temperature. The rate of enthalpy relaxation increased with an increasing number of methylene groups in the polymer backbone, but was independent of the number of methylene groups in the pendent chain. This observation indicated that the rate of enthalpy relaxation in these polymers was limited by the mobility of the polymer backbone. The enthalpy relaxation data was fitted to the Cowie-Ferguson model and the relaxation times obtained ranged from 44 min to about 100 min. Although these structure-property correlations facilitate the design of new materials with predictable thermal properties, they are rarely investigated for biomedical polymers. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1441–1448, 1997     

Self-assembly of amphiphilic di and triblock copolymers of styrene and quaternized 5-(N,N-diethylamino) isoprene in selective solvents

Self-association of highly asymmetric block copolymers of styrene and quaternized 5-(N,N-diethylamino)isoprene was studied. After quaternization with dimethyl sulfate, the di and triblock copolymers consisted of a long block of polystyrene (PS) with a short poly[5-(N,N,N-diethylmethylammonium)isoprene][methyl sulfate](PAI) block at one or both chain ends, respectively. The aggregates were prepared by first dissolving the copolymers in an organic solvent and then adding water to induce the segregation of the PS chains. Pure DMF, THF or dioxane was used as the organic solvent, as well as DMF/THF mixtures. The critical water content (cwc) and the morphologies were studied as a function of the common solvent, initial copolymer concentration and architecture (di or triblock) by static light scattering and by Transmission Electron Microscopy (TEM), respectively. It was found that both, the cwc and the morphologies of the aggregates are most strongly affected by the nature of the common solvent. Some unexpected behaviors were found for the triblock copolymer. Morphologies of a triblock copolymer in various mixtures of DMF and THF, quenched at determined water contents, were investigated in order to study the degree of morphological control that can be achieved solely as function of the organic solvent composition. Multiple morphologies have been found including equilibrium morphologies and kinetically trapped ones. Finally, the stability of primary micelles prepared in DMF was studied by DLS, upon dilution with DMF and water, and a possible mechanism for the destabilization of the aggregates is proposed.