Evaluation of 3D Printed Gelatin‐Based Scaffolds with Varying Pore Size for MSC‐Based Adipose Tissue Engineering

Adipose tissue engineering aims to provide solutions to patients who require tissue reconstruction following mastectomies or other soft tissue trauma. Mesenchymal stromal cells (MSCs) robustly differentiate into the adipogenic lineage and are attractive candidates for adipose tissue engineering. This work investigates whether pore size modulates adipogenic differentiation of MSCs toward identifying optimal scaffold pore size and whether pore size modulates spatial infiltration of adipogenically differentiated cells. To assess this, extrusion‐based 3D printing is used to fabricate photo‐crosslinkable gelatin‐based scaffolds with pore sizes in the range of 200–600 µm. The adipogenic differentiation of MSCs seeded onto these scaffolds is evaluated and robust lipid droplet formation is observed across all scaffold groups as early as after day 6 of culture. Expression of adipogenic genes on scaffolds increases significantly over time, compared to TCP controls. Furthermore, it is found that the spatial distribution of cells is dependent on the scaffold pore size, with larger pores leading to a more uniform spatial distribution of adipogenically differentiated cells. Overall, these data provide first insights into the role of scaffold pore size on MSC‐based adipogenic differentiation and contribute toward the rational design of biomaterials for adipose tissue engineering in 3D volumetric spaces.     

Corrosion inhibitors: design, performance, and computer simulations

The development of a methodology to predict the performance of a corrosion inhibitor (CI) using specific types of modeled and experimental surfaces and their subsequent estimation is presented. For previously reported imidazoline CIs, the theoretical partition coefficients and molecular volumes were calculated, providing a guide for molecular engineering of new imidazolines. The new CIs, N-[2-(2-alkyl-4,5-dihydroimidazol-1-yl)ethyl]alkylamides and N-[2-(2-alkyloylaminoethylamino)ethyl]alkylamides, were designed, prepared, and their theoretical partition coefficients and molecular volumes calculated. These indexes were correlated between tested and prototype CIs to select the best ones for the corrosion inhibition tests. The inhibition efficiencies were measured through potentiodynamic polarization curves (PPC), linear polarization resistance (LPR), and weight loss measurements (WLM) for SAE-1010 and SAE-1018 steels. The leading molecules were 1-(2-decylaminoethyl)-2-decylimidazoline and 1-(2-dodecylaminoethyl)-2-dodecylimidazoline with WLM efficiencies (steel 1010), of 62.8 and 78.9%, respectively. The efficiencies for the PPC/LPR tests (steel 1018) were 97 and 94%. To understand the mechanism of action of CIs, a simple model is suggested for the growth of self-assembled monolayers of CIs on a crystalline substrate. This model takes into account the amphiphilic nature of the inhibitor molecule on the adsorption process. Despite the simplicity of the model, the Monte Carlo simulations reproduce qualitatively many of the experimentally observed features involved in the formation of monolayers and provide a tentative explanation for the mechanism of corrosion inhibition.     

Mutual attraction of laser beams in plasmas: braided light

The energy loss of slow ions during grazing scattering from a LiF(100) surface as a function of the projectile atomic number Z1 is observed to show oscillations similar to those occurring in metals. A model of stopping of ions in an electron gas where screening is calculated from density functional theory reproduces well the experimental data. The same model gives good agreement with the energy loss obtained in transmission experiments performed with H and He projectiles. Analysis of these results allows us to gain new insights in the stopping of slow ions in ionic crystals.     

Null sets and games in Banach spaces

The notion of Aronszajn-null sets generalizes the notion of Lebesgue measure zero in the Euclidean space to infinite dimensional Banach spaces. We present a game-theoretic approach to Aronszajn-null sets, establish its basic properties, and discuss some ensuing open problems.     

Properties of methylammonium lead iodide perovskite single crystals

The technique for growing CH₃NH₃PbI₃ single crystals from saturated solutions in concentrated hydroiodic acid is improved by introducing a reducing agent (hypophosphorous acid). The structure of perovskite is confirmed by single crystal XRD. By energy dispersive spectroscopy and X-ray photoelectron spectroscopy it is established that the stoichiometry of the grown crystals corresponds to the CH₃NH₃PbI₃ compound. Changes in the photoluminescence intensity during in-air measurements show that the crystals synthesized using the reducing agent are more stable in the external environment with laser exposure than without it.     

Continuum percolation of the four-bonding-site associating fluids

Wertheim’s integral equation theory for associating fluids is reformulated for the study of the connectedness properties of associating hard spheres with four bonding sites. The association interaction is described as a square-well saturable attraction between these sites. The connectedness version of the Ornstein-Zernike (OZ) integral equation is supplemented by the PY-like closure relation and solved analytically within an ideal network approximation in which the network is represented as resulting from the crossing of ideal polymer chains. The pair connectedness functions and the mean cluster size are calculated and discussed. The condition for the percolation transition and the analytical form of the percolation threshold are derived. The connection of the percolation with the gas-liquid phase transition is discussed.     

Compatibility conditions for the Cauchy-Green strain fields: Solutions for the plane case

This paper considers the issues related to uniqueness and existence of a finite deformation generated by prescribed right or left Cauchy-Green strain tensor field in the plane. First, the questions of uniqueness and existence to a pre-assigned right strain field C are discussed. It is shown that the existence condition, in the context of continuum mechanics, are naturally posed using the field corresponding to the square root of C instead of C, the latter a classical approach. Then, the corresponding questions for the left strain field are considered, which is more involved. The analysis of uniqueness gives rise to an appropriate classification of the deformation fields. The question of existence is discussed and a complete solution is presented. In both the right and left cases, we stress the techniques for obtaining the corresponding deformation fields.     

The correlations in a star molecule fluid. Integral equation theory and Monte Carlo study

The structure of a starlike molecule (SLM) fluid with four arms of different length is studied by applying the associative Percus–Yevick integral equation (IE) theory and canonical Monte Carlo (MC) simulations. In the IE study the SLM fluid is modelled by a fluid of hard spheres with four associative sites on each sphere while the MC has been performed for a freely-joined tangent hard sphere fluid. The total radial distribution functions have been calculated in both approaches for different volume fraction regimes and different arm lengths. It is shown that the associative IE theory predicts the structure of SLM fluid best for relatively long arms and at high densities. Additionally, the dependence of the SLM centre–centre correlations on the functionality and fluid particle density has been analysed using the MC results.