Screening of Hydrogels for Human Pluripotent Stem Cell–Derived Neural Cells: Hyaluronan‐Polyvinyl Alcohol‐Collagen‐Based Interpenetrating Polymer Network Provides an Improved Hydrogel Scaffold

There is a clear need for novel in vitro models, especially for neuronal applications. Development of in vitro models is a multiparameter task consisting of cell‐, biomaterial‐, and environment‐related parameters. Here, three different human origin neuronal cell sources are studied and cultured in various hydrogel 3D scaffolds. For the efficient evaluation of complex results, an indexing method for data is developed and used in principal component analysis (PCA). It is found that no single hydrogel is superior to other hydrogels, and collagen I (Col1) and hyaluronan–poly(vinyl alcohol) (HA1‐PVA) gels are combined into an interpenetrating network (IPN) hydrogel. The IPN gel combines cell supportiveness of the collagen gel and stability of the HA1‐PVA gel. Moreover, cell adhesion is studied in particular and it is found that adhesion of neurons differs from that observed for fibroblasts. In conclusion, the HA1‐PVA‐col1 hydrogel is a suitable scaffold for neuronal cells and supports adhesion formation in 3D.     

High-molecular-weight hydrolyzed polyacrylamides. II. Potentiometric titrations

Potentiometric titrations in water of high-molecular-weight partly hydrolyzed polyacrylamides were analyzed by the Lifson—Katchalsky rodlike model. A fair concordance was found between theory and experimental curves with pK₀ of acid functions of about 4.75 when 0 < τ < 0.49. Two methods were derived to calculate the parameter n of the extended Henderson-Hasselbach equation by using a series expansion of pK_a vs. α, not yet reported in the literature. A new equation for n was established and comparison between two sets of values of n, obtained by using the theoretical ΔpK curves and series expansion is discussed.     

Musical quality assessment of clarinet reeds using optical holography

Vibrational modes of 24 clarinet reeds have been observed in both dry and wet conditions using holographic interferometry. Results have been compared with the "musical quality" of the reeds as judged by two professional clarinet players. An excellent correspondence has been demonstrated between specific vibrational behavior and musical quality. The results suggest that the presence and symmetry of a strong first torsional mode are indicative of good or very good musical quality. A second, but less stringent quality criterion is the proximity of frequencies corresponding to the second torsional and the second flexural mode. This proximity leads to the creation of mixed vibrational modes for the very best of the investigated clarinet reeds.     

Pedestal antiresonant reflecting waveguides for robust coupling to microsphere resonators and for microphotonic circuits

Strip-line pedestal antiresonant reflecting waveguides are high-confinement, silica integrated optical waveguides in which the optical modes are completely isolated from the substrate by thin high-index layers. These waveguides are particularly well suited for whispering-gallery mode excitation in high-Q microspheres. They can also be used in microphotonic circuits, such as for microring resonators. The theory and design of these structures are highlighted. Experiments that show high coupling efficiency to microspheres are also demonstrated.     

Wetting of nanogrooved polymer surfaces

Molecular dynamics simulations were used to study the wetting of nanogrooved PE and PVC polymer surfaces. The contact angles, equilibrium states, and equilibrium shapes of two nanosized water droplets were analyzed on surfaces with 1D-arranged periodic roughness of various dimensions. The composite solid-liquid contact, which is preferred in practical applications and in which a droplet rests on top of the surface asperities, was observed on the roughest PE surfaces, whereas water filled the similar but slightly deeper grooves on PVC surfaces. The transition from the wetted to composite contact regime occurred when the contact angle with a flat surface reached the value at which the apparent Wenzel and Cassie contact angles are equal. Droplets on grooved PE surfaces with the composite contact exhibited contact angles in agreement with Cassie's equation, but the increase in hydrophobicity on smoother surfaces with the wetted contact was less than expected from Wenzel's equation. The difference between the simulated and theoretical values decreased as the dimensions of the surface grooves increased. Only a slight increase or even a slight decrease in the contact angles was observed on the grooved PVC surfaces, owing to the less hydrophobic nature of the flat PVC surface. On both polymers, the nanodroplet assumed a spherical shape in the composite contact. Only minor anisotropy was observed in the wetted contact on PE surfaces, whereas even a highly anisotropic shape was seen on the grooved PVC surfaces. The contact angle in the direction of the grooves was smaller than that in the perpendicular direction, and the difference between the two angles decreased with the increasing size of the water droplet.     

Solidification/stabilization of lead with the aid of bagasse as an additive to Portland cement

Solidification/stabilization (S/S) of hazardous waste is a widely used technology; therefore, it is crucial to evaluate its effectiveness and make attempts to improve the technique. A better matrix for S/S of hazardous waste was designed that is effective and economically feasible. This was accomplished by adding bagasse (byproduct of milling or diffusing sugar cane) to the waste/cement matrix. Lead nitrate was used as the model heavy metal waste with a 10 or 15% lead by weight to cement loading. Samples were cured for 7, 14, and 28 days at 24°C. Samples containing bagasse typically resulted in TCLP (modified) extract lead concentrations of approximately 0.5 mg/l of lead for all samples, while samples containing no bagasse had lead extract concentrations of approximately 5 mg/l for 10% samples and 45 mg/l for 15%. Results indicate that using bagasse as an additive to cement effectively improved the S/S of lead.