High-Temperature Immittance Response in Anatase-Based Sensor Materials

The ac small-signal electrical response of anatase-based sensors is examined at elevated temperatures (400°C T 900°C) via lumped parameter/complex plane analysis (LP/CPA). The ac data, monitored in the frequency range 5 Hz f 13 MHz, are used to establish the role of microstructures on the resulting electrical behavior in these polycrystalline materials. Two semicircular relaxations, observed in the impedance plane, are attributed to the low-frequency related grain boundary and high-frequency related grain response. The grain-boundary response is difficult to quantify at elevated temperatures via LP/CPA and dc measurements. The electrical path homogeneity is examined via the presence of the depression angle which remained nearly invariant in the range of measurement temperatures. These features are discussed and compared with the results obtained at room temperature.     

Plain and drug loaded polyphosphazene membranes and microspheres in the treatment of rabbit bone defects

The healing of periodontal surgical defects was studied in rabbits, using polyphosphazenes (POP) membranes and microspheres, both plain or drug-enriched. POP polymers having amino acid ester as backbone substituents, are used since they resorb and undergo hydrolytic degradation to ammonia, phosphate and amino acids. Fourteen animal were operated in tibia, and other fourteen at angle of the mandible, that was reached by extraoral access. Bone defects were performed in tibiae, and covered either with POP or with poly-tetrafluoroethylene (PTFE) membranes, while other rabbits served as controls. The animals were sacrificed after one and two months, and the tibiae taken and processed for optical microscopy. Similar surgical defects were made in mandible, and POP membranes were placed over the breaches, some of which were filled with POP microspheres, both alone or mixed with granular hydroxyapatite. For comparison, two rabbits were treated with PTFE membranes, while other two served as controls. The animals operated at the mandible were all sacrificed after one month, and the operated bones taken and processed for histology. It was found that POP membranes were very effective in promoting the healing in tibiae, while less satisfactory results were found in the animals treated with PTFE membranes and in controls. In mandible, the healing occurred without a clear relationship with the grafted microgranular material or the membrane, since repairing bone was found also in controls. In any case, both POP membranes and microspheres showed excellent biocompatibility, as no inflammatory cells or macrophages were found in the surrounding tissue. This property was completely independent from the presence of drug, since the matrix-entrapped drugs, released in the tissue, did not hamper the bone healing. It was also found that POP, by itself, has a positive effect in stimulating the bone repair.     

Scratch behavior of extrusion and adhesive laminated multilayer food packaging films

Scratch‐induced puncture damages on adhesive and extrusion laminated multilayer food packaging films were investigated. Films were tested using a modified standardized linearly increasing load scratch test methodology, ASTM D7027‐05/ISO 19252:2008, which has successfully demonstrated an ability to correlate damages observed in field use of packaging films to laboratory findings. Samples were cross‐sectioned to view the evolution of damage in a layer‐by‐layer fashion to determine any potential weak‐link in the laminate. It was observed that the extrusion laminated film showed both superior scratch performance and superior layer adhesion with increasing scratch load, particularly upon severe film deformation. The extrusion lamination process may be used to produce strong, scratch‐resistant packaging films without the need for additional adhesive layers and the associated health and environmental concerns. Usefulness of the standardized scratch testing for evaluating performance of food packaging films and laminates is discussed. POLYM. ENG. SCI., 54:71–77, 2014. © 2013 Society of Plastics Engineers     

Evaluation of conventional and alternative monitoring methods for a recreational marine beach with nonpoint source of fecal contamination

The objectives of this work were to compare enterococci (ENT) measurements based on the membrane filter, ENT(MF) with alternatives that can provide faster results including alternative enterococci methods (e.g., chromogenic substrate (CS), and quantitative polymerase chain reaction (qPCR)), and results from regression models based upon environmental parameters that can be measured in real-time. ENT(MF) were also compared to source tracking markers (Staphylococcus aureus, Bacteroidales human and dog markers, and Catellicoccus gull marker) in an effort to interpret the variability of the signal. Results showed that concentrations of enterococci based upon MF (<2 to 3320 CFU/100 mL) were significantly different from the CS and qPCR methods (p < 0.01). The correlations between MF and CS (r = 0.58, p < 0.01) were stronger than between MF and qPCR (r ≤ 0.36, p < 0.01). Enterococci levels by MF, CS, and qPCR methods were positively correlated with turbidity and tidal height. Enterococci by MF and CS were also inversely correlated with solar radiation but enterococci by qPCR was not. The regression model based on environmental variables provided fair qualitative predictions of enterococci by MF in real-time, for daily geometric mean levels, but not for individual samples. Overall, ENT(MF) was not significantly correlated with source tracking markers with the exception of samples collected during one storm event. The inability of the regression model to predict ENT(MF) levels for individual samples is likely due to the different sources of ENT impacting the beach at any given time, making it particularly difficult to to predict short-term variability of ENT(MF) for environmental parameters.     

Synthesis, characterization, and oxygen permeability of homo- and copolymers from p-[tris(trimethylsilyl)silyl]-phenylacetylene

Summary Homopolymerization of p-[tris(trimethylsilyl)silyl]phenylacetylene [p(Me₃Si)₃SiPA] by Rh catalyst provided insoluble polymer. On the other hand, copolymerization of p(Me₃Si)₃SiPA with p-(trimethylsilyl)phenylacetylene (pMe₃SiPA) at 80:20, 50:50, and 20:80 feed ratios afforded high molecular weight copolymers (M _w > 1×10⁶), all of which were soluble in common solvents such as toluene and chloroform. The mole ratios of p(Me₃Si)₃SiPA to pMe₃SiPA unit in copolymers were close to those in the feeds. The oxygen permeability increased monotonously with increasing p(Me₃Si)₃SiPA content of copolymer in correspondence with fractional free volume; the value of the copolymer for the 80:20 feed ratio reached 770 barrers. Received: 30 August 2000/ Accepted: 6 September 2000     

Gamma ray-induced copolymerization of copper (II) methacrylate: A way of access to copper-based synthetic micro- and macroporous resins

Copper methacrylate undergoes high-yield copolymerization with hydroxi-ethylmethacrylate in the presence of 1,1,1-tris(hydroximethyl) propane trimethacrylate under γ-rays irradiation at room temperature. The bluish-green materials are characterized by bulk expanded volume measurements and infrared and ultraviolet-visible spectroscopy, and appear to be able to slowly release an appreciable percentage of the metal center embodied in the polymer network. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 11–17, 1998