EELS analysis of {1 1 1} Σ3 and {1 1 2} Σ3 twin boundaries and their junctions in phosphor-doped cast polycrystalline silicon

{1 1 1} Σ3 and {1 1 2} Σ3 twin boundaries and their junctions in a phosphor-doped cast polycrystalline silicon were investigated by EELS using HREM to study the local electrical properties and impurity effects at these boundaries and junctions. FWHMs of the silicon plasmon-loss peaks are wider at the grain boundary junctions and {1 1 2} Σ3 twin boundary as compared with other area partly because of the overlapped effect of plasmon loss of SiO₂ and carbon. In the inner-shell edge part of EELS spectrum, the grain boundary junction having distorted structure shows slightly strong intensity at around 110 eV, suggesting the formation of nano-size SiO₂, even though the presence of the SiO₂ could not be observed by HREM. The effects of carbon K-edge can be recognized in the EELS spectra acquired at {1 1 1} Σ3 and {1 1 2} Σ3 boundaries and their junctions, suggesting the grain boundary segregation of carbon atoms.     

Facile Formation of Uniform Shell‐Crosslinked Nanoparticles with Built‐in Functionalities from N‐Hydroxysuccinimide‐Activated Amphiphilic Block Copolymers

An amphiphilic block copolymer, poly(methylacrylate)₈₂‐block‐poly(N‐(acryloyloxy)succinimide_0.29‐co‐(N‐acryloylmorpholine)_0.71)₁₅₅ (PMA₈₂‐b‐P(NAS_0.29‐co‐NAM_0.71)₁₅₅), was synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization and then was supramolecularly assembled into micelles in aqueous solution, followed by chemical crosslinking throughout the shell region upon the introduction of 2,2′‐(ethylenedioxy)‐bis(ethylamine) as a crosslinker to afford well‐defined shell crosslinked nanoparticles (SCKs). The number‐averaged hydrodynamic diameters of the micelles and SCKs were (17 ± 4) nm and (16 ± 3) nm, respectively, by dynamic light scattering (DLS), and (15 ± 2) nm and (13 ± 2) nm, respectively, by transmission electron microscopy (TEM). In an attempt to narrow the particle size distributions, the dodecyl trithiocarbonate chain end of the block copolymer was replaced by a 2‐cyanoisopropyl moiety. Each nanoparticle system was characterized by DLS, electrophoretic light scattering (ELS), TEM, and small‐angle X‐ray scattering (SAXS). SAXS was of particular importance, as it provided definitive observation and quantification of shell contraction and densification upon shell crosslinking. The direct incorporation of NAS into the block copolymers during their preparation allowed for unique crosslinking chemistry to proceed with added diamino crosslinkers. The primary advantages of this system include the ability to conduct in situ synthesis of SCKs that are crosslinked directly and derivatized easily by adding nucleophilic ligands before, during, or after the crosslinking.     

Metabotropic glutamate receptor subtype 7 ablation causes deficit in fear response and conditioned taste aversion

Metabotropic glutamate receptors (mGluRs) consist of eight different subtypes and exert their effects on second messengers and ion channels via G-proteins. The function of individual mGluR subtypes in the CNS, however, largely remains to be clarified. We examined the fear response of freezing after electric shock in wild-type and mGluR7(-/-) knockout littermates. Wild-type mice displayed freezing immediately after and 1 d after footshock. In comparison, mGluR7(-/-) knockout mice showed significantly reduced levels in both immediate postshock and delayed freezing responses. However, the knockout mice exhibited no abnormalities in pain sensitivity and locomotor activity. To further examine amygdala-dependent behavior, we performed conditioned taste aversion (CTA) experiments. In wild-type mice, the administration of saccharin followed by intraperitoneal injection of the malaise-inducing agent LiCl resulted in an association between saccharin and LiCl. This association caused strong CTA toward saccharin. In contrast, mGluR7(-/-) knockout mice failed to associate between the taste and the negative reinforcer in CTA experiments. Again, the knockout mice showed no abnormalities in taste preference and in the sensitivity to LiCl toxicity. These results indicate that mGluR7 deficiency causes an impairment of two distinct amygdala-dependent behavioral paradigms. Immunohistochemical and immunoelectron-microscopic analyses showed that mGluR7 is highly expressed in amygdala and preferentially localized at the presynaptic axon terminals of glutamatergic neurons. Together, these findings strongly suggest that mGluR7 is involved in neural processes subserving amygdala-dependent averse responses.     

Selective formation of Na-X zeolite from coal fly ash by fusion with sodium hydroxide prior to hydrothermal reaction

Hydrothermal treatment of fly ash with alkali gives various types of zeolites such as Na-Pl, Na-A and hydroxysodalite, where the zeolite zone was formed like an egg white, covering the central core of fly ash particles, as evinced in the previous paper. By fusion with sodium hydroxide, most of the fly ash particles were converted into sodium salts such as silicate and aluminate, from which hydrothermal reaction without stirring favourably resulted in the formation of Na-X zeolite. Crystallinity of Na-X zeolite as high as 62% was attained at the optimum condition of NaOH/fly ash = 1.2 and a fusion temperature of 823 K. Fly ash contains 14 wt% mullite (3Al₂O₃·2SiO₂), which was revealed to be a less-active crystalline component for zeolite formation. Aluminium-enriched fly ash gave Na-A in place of Na-X zeolite. Scanning electron microscope images of cubic and octahedral crystals characteristic of Na-A and Na-X zeolite, respectively, obtained from fly ash, are given.     

Use of associating polymers as multifunctional thickeners: studies of Their structure in aqueous solutions via nmr, qels, fluorescence, And rheology measurements

The solution properties of an associating polymer were studied by NMR, quasi‐elastic light scattering (QELS), fluorescence, and rheology measurements. An associative thickening (AT) polymer was designed having a nonionic poly(ethylene oxide) backbone with long alkyl chains at both ends to achieve high viscosity even at relatively high salt concentrations and over a wide pH range. This study focuses on the associative state of the polymer in aqueous solutions at various polymer concentrations. In a fluorescence probe study using pyrene a spectral change in the I₃/I₁ ratio was observed for pyrene at a polymer concentration (C_p) of 3 x 10^‐4%, indicating an apparent critical concentration (cmc) of the amphiphilic polymer. The viscosity, self‐diffusion coefficient (D_sel), and hydrodynamic size (R_h) distribution measurements at various C_p all suggest that there is a second transition at C_p? 0.4%. Although we observed the discontinuity in viscosity, D_sel, and R_h at C_p? 0.4%, no changes in the relaxation times (T₁ and T₂) were recognized for either the alkyl chain or the ethylene oxide moiety of the polymer at C _p= 0.1–1%. These data suggest that there are no structural changes or phase transitions at C_p? 0.4%, but that intermicellar networks are presumably formed by bridging of the end alkyl groups of the polymer, which is driven by hydrophobic forces. Because the polymer forms networks by hydrophobic interaction and the polymer itself is nonionic, the viscosity of the polymer solution was influenced very little by either the addition of salt or a pH change, as would be expected. The dynamic viscoelastic study revealed that the polymer solution exhibits a single mode Maxwell type relaxation behavior with a terminal relaxation time of about 0.61 s, which imparts a unique flow appearance to the polymer solutions. The time course measurements of the dynamic elastic modulus of the stratum corneum revealed that the polymer has excellent potential for skin softening. It was concluded that the associative thickening polymer not only is a useful thickener with a salt and pH tolerance but also has beneficial skincare effects.     

Blood rheological study in rats with fatty liver--with special reference to effects of ethyl icosapentate

A blood rheological study was conducted using Kikuchi's micro-channel method in rats with fatty liver. Effects of eicosapentaenoic acid (EPA) on blood rheology were also evaluated. Male SD rats given normal feed served as the control. One group was given choline-deficient feed for 4 weeks (EPA (-) group), while another group was daily given EPA (1000 mg/kg) for 4 weeks together with choline-deficient feed (EPA (+) group). The micro-channel passage time was determined using 100 microliters of whole blood. The passage time significantly increased in the EPA (-) group compared to the control (p < 0.01). It significantly decreased in the EPA (+) group compared to the EPA (-) group (p < 0.01). Findings obtained in the present study suggested that blood rheological factors are related to the development of fatty liver and that EPA inhibits fatty changes of the liver by improving these rheological factors.     

Influence of voltage rise time on oxidation treatment of NO in simulated exhaust gas by polarity‐reversed pulse discharge

This paper describes an experimental study of NO removal from a simulated exhaust gas by repetitive surface discharge on a glass barrier subjected to polarity‐reversed voltage pulses. The very fast polarity‐reversal with a rise time of 20 ns is caused by direct grounding of a charged coaxial cable 10 m in length. The influence of the voltage rise time on energy efficiency for NO removal is studied. The results of NO removal using a barrier‐type plasma reactor with a screw‐plane electrode system indicate that the energy efficiency of very fast polarity reversal caused by direct grounding is higher than that of slower polarity reversal caused by grounding through an inductor at the cable end. The energy efficiency of direct grounding is approximately 80 g/kWh for a 50% NO removal ratio and approximately 60 g/kWh for a 100% NO removal ratio. Very intense discharge light is observed at an initial time of 10 ns for fast polarity reversal, whereas the intensity of the initial discharge light for slower polarity reversal is relatively small. To confirm the effectiveness of the polarity‐reversed pulse application, a comparison of the energy efficiency of polarity‐reversed voltage pulses and an AC 60‐Hz voltage is presented. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(4): 32–38, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21215     

CO2 bubble nucleation in polystyrene: Experimental and modeling studies

Polymer foams are used extensively in a variety of applications. A firm understanding of bubble nucleation is vital to predict foam properties based on process conditions. However, a number of theoretical and experimental challenges have thus far limited progress in this area. We propose the use of a scaling theory to connect nucleation behavior to well understood bulk phase behavior of polystyrene-CO₂ systems, which can be predicted by equations of state, such as the Sanchez–Lacombe equation of state. Scaling theory of nucleation asserts that when the reversible work of critical nucleus formation is properly normalized and plotted against the normalized degree of supersaturation, the resulting scaling curve is insensitive to temperature and the materials being used. Once the form of the scaling function is known, it can be used to predict the nucleation barrier knowing only the initial foaming conditions and calculating only bulk thermodynamic values. Using an extension of diffuse interface theory, we determined the slope of the scaling curve near saturation. This initial slope allows us to constrain the scaling function for better predictions of the reversible work. We also performed a series of experiments to help verify the accuracy of the scaling theory. The scaled free energy barriers determined from our experiments are consistent with the scaling function so constructed, and our theoretical results qualitatively agree with those found previously. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012