The role of m‐phenylenebismaleimide (BMI) in reactive processing of poly(propylene)/magnesium hydroxide composites, 3. Analysis of interphase structure development

In the first and second parts of this series, the effect of m‐phenylenebismaleimide (BMI), processing temperature and a lubricant (a fatty acid ester/amide blend) on the mechanical and rheological properties of poly(propylene) (PP)/magnesium hydroxide composites was investigated. The third part focuses on interactions between BMI and the magnesium hydroxide and between the BMI and PP matrix. It has been shown that interaction between BMI and the filler is via an amide carboxylate together with possible polymerisation at the filler surface. Interaction of BMI with the PP matrix is via addition of PP macro‐radicals, produced via thermo‐mechanical degradation, to the maleimide alkenes of BMI. Greater crosslink density in the interphase region than in the bulk matrix is considered to result in a reduction of crystallinity within this region. This is manifested as a significant improvement in composite toughness relative to the equivalent unmodified composite.     

Polymerization of acrylamide in styrene containing inverse microemulsions: polymerization kinetics and polymer product composition studies

The kinetics of free‐radical homopolymerization and copolymerization of acrylamide (AAm) and styrene (S) initiated by water‐soluble ammonium peroxodisulfate, (APS) or by toluene‐soluble dibenzoyl peroxide (DBP) in inverse microemulsion toluene/S/AOT (sodium bis(2‐ethylhexyl)sulfosuccinate)/water/AAm characterized by a low volume fraction of the aqueous phase (Φ_aw ≈ 0.08) as a function of the concentration of S in the oil phase of the inverse microemulsion system have been studied. S strongly decreases the rate of AAm/S (co)polymerization. This is valid for both APS and DBP initiators. Kinetic measurements indicate the important role for cross‐initiation of water soluble AAm growing chains and of oil soluble S analogues activated by the primary free‐radicals generated from APS (or from DBP) in the dispersed water droplets (or in the continuous oil‐phase) of the inverse microemulsion, respectively. With inverse microemulsions containing toluene (70.73 %)/S (2.44 %)/AOT(17.56 %)/water (7.32 %)/AAm (1.95 %), after polymerization (initiator APS, 3.04 × 10⁻² mol dm⁻³ of water) and separation of the polymeric components, the following yields were obtained: AAm/S (co)polymer (89.20 mass%; ie 62.24 mass% of AAm structural units and 26.96 mass% of S structural units), polyacrylamide (9.4 mass%) and polystyrene (1.4 mass%). © 2000 Society of Chemical Industry     

Inverse microemulsion polymerization of acrylamide in the presence of N,N-dimethylacrylamide

The presence of N,N-dimethylacrylamide (NDA) influences the stability of initial, clear, single-phase Winsor IV inverse microemulsion composed of toluene/AOT (sodium salt of bis(2-ethylhexyl) sulfosuccinate)/NDA/water/acrylamide (AAm). For a molar fraction of NDA, n_NDA = [NDA]/([NDA] + [AAm]) = 0.200 a single-phase system turned to a milky one during polymerization initiated by oil-soluble dibenzoyl peroxide or water-soluble ammonium peroxodisulfate, and finally a two-phase system was formed. For n_NDA values greater than 0.200 also the precipitation of a polymeric product was observed during polymerization. The (co)polymerization rate of AAm and NDA exponentially decreases with increasing value of n_NDA, while the reverse is true for the (co)polymer particle diameter. The results support the idea of simultaneously proceeding free-radical polymerization initiated by free radicals in continuous oil and dispersed water phase of the inverse microemulsion system.     

Actinide ENDF/B-VII cross-section evaluations and validation testing

We describe advances made recently at Los Alamos for ENDF/B-VII, and for future ENDF releases, of actinide cross-section evaluations. Using americium as an illustrative example, we describe recent experiments that have largely confirmed the nuclear theory predictions that were the basis for the ENDF/B-VII.0 data for these americium reactions. The goal of this paper is to highlight some of the open issues in our understanding of the actinide nuclear data – especially for fast reactor applications – and show examples of how experiment, theory, and integral data validation has advanced our understanding. We will also describe the usage of these data in MCNP and S_N radiation transport simulations of various integral critical systems, for both criticality and for transmutation reaction rates.     

Behavioral Alterations and Decreased Number of Parvalbumin-Positive Interneurons in Wistar Rats after Maternal Immune Activation by Lipopolysaccharide: Sex Matters

Maternal immune activation (MIA) during pregnancy represents an important environmental factor in the etiology of schizophrenia and autism spectrum disorders (ASD). Our goal was to investigate the impacts of MIA on the brain and behavior of adolescent and adult offspring, as a rat model of these neurodevelopmental disorders. We injected bacterial lipopolysaccharide (LPS, 1 mg/kg) to pregnant Wistar dams from gestational day 7, every other day, up to delivery. Behavior of the offspring was examined in a comprehensive battery of tasks at postnatal days P45 and P90. Several brain parameters were analyzed at P28. The results showed that prenatal immune activation caused social and communication impairments in the adult offspring of both sexes; males were affected already in adolescence. MIA also caused prepulse inhibition deficit in females and increased the startle reaction in males. Anxiety and hypolocomotion were apparent in LPS-affected males and females. In the 28-day-old LPS offspring, we found enlargement of the brain and decreased numbers of parvalbumin-positive interneurons in the frontal cortex in both sexes. To conclude, our data indicate that sex of the offspring plays a crucial role in the development of the MIA-induced behavioral alterations, whereas changes in the brain apparent in young animals are sex-independent.     

Elimination of Separation Processes for Post‐Consumer Polyolefin Waste: Reactive Blending Using 1,3‐Phenylene Dimaleimide in Presence of Filler

A novel approach using reactive processing is explored that eliminates the labour‐intensive separation of post‐consumer polyolefin waste from the mixed plastics waste stream. The reactive compatibiliser BMI has been used to form a modified blend of PCPW with 40% improved tensile strength relative to the uncompatibilised control. Addition of 60 wt.‐% magnesium hydroxide [Mg(OH)₂] during reactive compatibilisation with BMI gave rise to an even more significant enhancement (up to 100%) of the tensile strength. BMI was also able to usefully enhance the properties of a composite based on calcium carbonate and the polyolefin waste.

     

Hybrid modelling and emulation of mem‐systems

The recently published memristor emulator is based on a digital potentiometer, which is controlled by a microprocessor according to a programmed algorithm. After completing the emulator with suitable mutators, it is possible to emulate also memcapacitors and meminductors. This paper describes a novel approach to the modelling and emulation of general mem‐systems without the necessity of utilizing a digital potentiometer and additional mutators. Copyright © 2011 John Wiley & Sons, Ltd.     

Efficient 2-$mu$m Continuous-Wave Laser Oscillation of Tm$^3 + $:KLu(WO$_4$)$_2$

Monoclinic crystals of Tm-doped KLu(WO₄)₂ were grown with high crystalline quality for several dopant concentrations. The relevant spectroscopic properties for the ³ F₄rarr³H₆ laser transition (cross sections, lifetime) were measured at room temperature. Laser oscillation in the 2-mum range was obtained both with Ti:sapphire and diode laser pumping near 800 nm using different setups. The maximum output powers achieved were 1.4 and 4 W, respectively, and the corresponding slope efficiencies with respect to the absorbed power were 60% and 69%, respectively. The novel monoclinic double tungstate thulium host KLu(WO₄)₂ was directly compared to KGd(WO₄)₂ and exhibited superior performance. The two laser polarization configurations for Tm:KLu(WO₄)₂ ,E//N_m and E//N_p, were also compared under identical conditions with pumping by the polarized Ti:sapphire laser. Tuning was studied for both of them using an intracavity Lyot filter and the tuning range achieved was from 1800 to 1987 nm. In the case of no polarization selective cavity elements the diode-pumped Tm:KLu(WO₄ )₂ laser naturally selected the E//N_m polarization     

Single-channel response of hamster oocytes to fertilization with homologous spermatozoa.

Electrophysiological events occur early after fertilization, along with changes in intracellular Ca2+ concentration. Passive electrical parameters were determined in golden hamster oocytes by whole cell patch-clamp method. In separate experiments the effect of 4-aminopyridine on resting oocytes was tested. The single-channel patch clamp configuration was employed to assess the electrical response to fertilization with homologous sperm. Structure of oocytes submitted to patch clamp was evaluated with scanning electron microscopy and found to be preserved. Oocyte diameter was 70.2 +/- 2.2 microm; their resting parameters were: membrane potential 23.8 +/- 0.8 mV; total membrane specific resistance 519.1 +/- 94.6 ohms.cm2, and specific capacity 0.99 +/- 0.03 microF.cm(-2). Total membrane current was decreased by 42 % by 4-aminopyridine. Control oocytes and oocytes exposed to sperm differed in their membrane currents in response to a voltage ramp clamping membrane potential from - 100 mV to + 100 mV. In both cases, currents were largest at the most negative potentials, but sperm-exposed oocytes had larger currents. Additionally, while in control oocytes the current was inward at negative potentials but outward at positive potentials, in the presence of spermatozoa oocytes was inward within the whole voltage range tested. This latter current may represent Ca2+ entry.