Microhardness studies of PMMA/natural rubber blends

The microhardness, H, of PMMA/natural rubber blends, prepared following the solution method has been investigated by means of the microindentation technique. Hardness changes are correlated with the variation of the glass transition temperature. The influence of temperature and degree of deformation on H were additionally examined. The inclusion of rubber particles in the PMMA matrix is shown to soften the blends. The variation of the micromechanical property at the phase boundary of polymer/rubber particle has been studied. Results reveal that H drastically drops at the interphase. In the case of the drawn materials, the indentation anisotropy (ΔH) is shown to gradually increase with the draw ratio, where ΔH is found to be higher for the PMMA/rubber blend than for the original PMMA. This result is explained by the higher orientation of the PMMA molecules near the periphery of stretched rubber particles. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 205–210, 2004     

The lesbian,gay, bisexual and transgender community online: discussions of bullying and self-disclosure in YouTube videos

Computer-mediated communication has become a popular platform for identity construction and experimentation as well as social interaction for those who identify as lesbian, gay, bisexual or transgender (LGBT). The creation of user-generated videos has allowed content creators to share experiences on LGBT topics. With bullying becoming more common amongst LGBT youth, it is important to obtain a greater understanding of this phenomenon. In our study, we report on the analysis of 151 YouTube videos which were identified as having LGBT- and bullying-related content. The analysis reveals how content creators openly disclose personal information about themselves and their experiences in a non-anonymous rhetoric with an unknown public. These disclosures could indicate a desire to seek friendship, support and provide empathy.     

Improved electro-assisted removal of phosphates and nitrates using mesoporous carbon aerogels with controlled porosity

Three-activated carbon aerogels were synthesized by CO₂ activation of the materials prepared by the polycondensation of resorcinol and formaldehyde mixtures followed by supercritical drying. The obtained carbon aerogels were characterized and used as electrode materials for the electrosorption of sodium phosphate and nitrate. X-ray diffraction and Raman spectroscopy showed the dependence of the structural ordering of the aerogels with the resorcinol/catalyst ratio and the extent of activation. The electrosorption capacitance evaluated by cyclic voltammetry revealed large values for the activated samples containing a large contribution of mesopores, regardless the electrolyte salt. Due to an adequate combination of chemical and porous features, the desalting capacity of the activated carbon aerogel electrodes exceeded that of the as-prepared materials. The evaluation of the kinetic properties by chronocoulometric relaxation and impedance spectroscopy showed a decrease of time constant and resistances for highly mesoporous activated samples. A high deionization capacity and fast electrode discharge was detected for the deionization of sodium nitrate on the highly mesoporous activated aerogel. Data also showed the efficient electrosorption of ionic species on consecutive charge/discharge cycles, confirming the stability of the aerogel electrodes at the high applied potentials.     

Low-frequency noise in TaSiN/HfO/sub 2/ nMOSFETs and the effect of stress-relieved preoxide interfacial layer

Low-frequency noise characteristics are reported for TaSiN-gated n-channel MOSFETs with atomic-layer deposited HfO/sub 2/ on thermal SiO/sub 2/ with stress-relieved preoxide (SRPO) pretreatment. For comparison, control devices were also included with chemical SiO/sub 2/ resulting from standard Radio Corporation of America clean process. The normalized noise spectral density values for these devices are found to be lower when compared to reference poly Si gate stack with similar HfO/sub 2/ dielectric. Consequently, a lower oxide trap density of /spl sim/4/spl times/10/sup 17/ cm/sup -3/eV/sup -1/ is extracted compared to over 3/spl times/10/sup 18/ cm/sup -3/eV/sup -1/ values reported for poly Si devices indicating an improvement in the high-/spl kappa/ and interfacial layer quality. In fact, this represents the lowest trap density values reported to date on HfO/sub 2/ MOSFETs. The peak electron mobility measured on the SRPO devices is over 330 cm/sup 2//V/spl middot/s, much higher than those for equivalent poly Si or metal gate stacks. In addition, the devices with SRPO SiO/sub 2/ are found to exhibit at least /spl sim/10% higher effective mobility than RCA devices, notwithstanding the differences in the high-/spl kappa/ and interfacial layer thicknesses. The lower Coulomb scattering coefficient obtained from the noise data for the SRPO devices imply that channel carriers are better screened due to the presence of SRPO SiO/sub 2/, which, in part, contributes to the mobility improvement.     

Finite size effects in multilayered polymer systems: Development of PET lamellae under physical confinement

The glass transition temperature and the crystallization behaviour of poly(ethylene terephthalate) PET ultra-thin layers (a few tens of nm) within multilayered PET/polycarbonate (PC) coextruded films are investigated as a function of layer thickness by means of calorimetric measurements. Results are discussed in terms of reduced thickness and interface effects. The appearance and evolution of lamellar orientation upon isothermal crystallization of ultra-thin PET layers from the glassy state are explored based on real time small-angle X-ray scattering (SAXS) studies. Analysis of the SAXS measurements reveals that finite size effects hamper the crystallization process. However, the final lamellar structure is similar in both, the nanolayered PET and the bulk material. Results suggest that not only lamellar insertion but also some lamellar thickening contribute to the development of the final lamellar structure. Room temperature SAXS and wide-angle X-ray diffraction (WAXS) measurements indicate that two lamellar populations develop: edge-on lamellae are proposed to appear close to the interphases while flat-on lamellae, arising as a consequence of confinement, should be preferentially located in the layers core.     

Solid respirometry to characterize nitrification kinetics: a better insight for modelling nitrogen conversion in vertical flow constructed wetlands

We developed an original method to measure nitrification rates at different depths of a vertical flow constructed wetland (VFCW) with variable contents of organic matter (sludge, colonized gravel). The method was adapted for organic matter sampled in constructed wetland (sludge, colonized gravel) operated under partially saturated conditions and is based on respirometric principles. Measurements were performed on a reactor, containing a mixture of organic matter (sludge, colonized gravel) mixed with a bulking agent (wood), on which an ammonium-containing liquid was applied. The oxygen demand was determined from analysing oxygen concentration of the gas passing through the reactor with an on-line analyzer equipped with a paramagnetic detector. Within this paper we present the overall methodology, the factors influencing the measurement (sample volume, nature and concentration of the applied liquid, number of successive applications), and the robustness of the method. The combination of this new method with a mass balance approach also allowed determining the concentration and maximum growth rate of the autotrophic biomass in different layers of a VFCW. These latter parameters are essential inputs for the VFCW plant modelling.     

The Large Electrochemical Capacitance of Microporous Doped Carbon Obtained by Using a Zeolite Template

A novel microporous templated carbon material doped with nitrogen is synthesized by using a two‐step nanocasting process using acrylonitrile (AN) and propylene as precursors, and Na–Y zeolite as a scaffold. Liquid‐phase impregnation and in situ polymerization of the nitrogenated precursor inside the nanochannels of the inorganic scaffold, followed by gas‐phase impregnation with propylene, enables pore‐size control and functionality tuning of the resulting carbon material. The material thereby obtained has a narrow pore‐size distribution (PSD), within the micropore range, and a large amount of heteroatoms (i.e., oxygen and nitrogen). In addition, the carbon material inherits the ordered structure of the inorganic host. Such features simultaneously present in the carbon result in it being ideal for use as an electrode in a supercapacitor. Although presenting a moderately developed specific surface area (S_BET = 1680 m² g^–1), the templated carbon material displays a large gravimetric capacitance (340 F g^–1) in aqueous media because of the combined electrochemical activity of the heteroatoms and the accessible porosity. This material can operate at 1.2 V in an aqueous medium with good cycleability—‐beyond 10 000 cycles—and is extremely promising for use in the development of high‐energy‐density supercapacitors.