Comparison of mechanical and electrical activity and interstitial cells of Cajal in urinary bladders from wild-type and W/W-v mice

Background and purpose: W/Wv and wild-type murine bladders were studied to determine whether the W/Wv phenotype, which causes a reduction in, but not abolition of, tyrosine kinase activity, is a useful tool to study the function of bladder interstitial cells of Cajal (ICC).

Experimental approach: Immunohistochemistry, tension recordings and microelectrode recordings of membrane potential were performed on wild-type and mutant bladders.

Key results: Wild-type and W/Wv detrusors contained c-Kit- and vimentin-immunopositive cells in comparable quantities, distribution and morphology. Electrical field stimulation evoked tetrodotoxin-sensitive contractions in wild-type and W/Wv detrusor strips. Atropine reduced wild-type responses by 50% whereas a 25% reduction occurred in W/Wv strips. The atropine-insensitive component was blocked by pyridoxal-5-phosphate-6-azophenyl-2',4'-disulphonic acid in both tissue types. Wild-type and W/Wv detrusors had similar resting membrane potentials of -48 mV. Spontaneous electrical activity in both tissue types comprised action potentials and unitary potentials. Action potentials were nifedipine-sensitive whereas unitary potentials were not. Excitatory junction potentials were evoked by single pulses in both tissues. These were reduced by atropine in wild-type tissues but not in W/Wv preparations. The atropine-insensitive component was abolished by pyridoxal-5-phosphate-6-azophenyl-2',4'-disulphonic acid in both preparations.

Conclusions and implications: Bladders from W/Wv mice contain c-Kit- and vimentin-immunopositive ICC. There are similarities in the electrical and contractile properties of W/Wv and wild-type detrusors. However, significant differences were found in the pharmacology of the responses to neurogenic stimulation with an apparent up-regulation of the purinergic component. These findings indicate that the W/Wv strain may not be the best model to study ICC function in the bladder.

Barrier height variations and interface properties of PtSi/Si structures

To study some of the interfacial properties of PtSi/Si diodes, Schottky structures were fabricated on (100) crystalline silicon substrates by conventional thermal evaporation of Pt on Si followed by annealing at different temperatures (from 400 degrees C to 700 degrees C) to form PtSi. The PtSi/n-Si diodes, all yielded Schottky barrier (SB) heights that are remarkably temperature dependent. The temperature range (20-290 K) over which the I-V characteristics were measured in the present study is broader with a much lower limit (20 K), than what is usually reported in literature. These variations in the barrier height are adequately interpreted by introducing spatial inhomogeneity into the barrier potential with a Gaussian distribution having a mean barrier of 0.76 eV and a standard deviation of 30 meV. Multi-frequency capacitance-voltage measurements suggest that the barrier is primarily controlled by the properties of the silicide-silicon interface. The forward C-V characteristics, in particular, show small peaks at low frequencies that can be ascribed to interface states rather than to a series resistance effect.

Precipitation, microstructure and mechanical properties of low nickel maraging steel

A maraging steel with a composition of Fe–12·94Ni–1·61Al–1·01Mo–0·23Nb (wt-%) was investigated. Optical, scanning electron and transmission electron microscopy and X-ray diffraction analysis were employed to study the microstructure of the steel after different aging periods at temperatures of 450–600°C. Hardness and Charpy impact toughness of the steel were measured. The study of microstructure and mechanical properties showed that nanosized precipitates were formed homogeneously during the aging process, which resulted in high hardness. As the aging time is prolonged, precipitates grow and hardness increases. Fractography of the as forged steel has shown mixed ductile and brittle fracture and has indicated that the steel has good toughness. Relationships among heat treatment, microstructure and mechanical properties are discussed. Further experiments using tensile testing and impact testing for aged steel were carried out.

Structural and magnetic properties of sol-gel Co2xNi0.5-xZn0.5-xFe2O4 thin films

Nanocrystalline Co2xNi0.5-xZn0.5-xFe2O4 (x = 0-0.5) thin films have been synthesized with various grain sizes by a sol-gel method on polycrystalline silicon substrates. The morphology as well as magnetic and microwave absorption properties of the films calcined at 1073 K were studied using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and vibrating sample magnetometry. All films were uniform with out microcracks . The Co content in the Co-Ni-Zn films resulted in a grain size ranging from 15 to 32 nm while it ranged from 33 to 49 nm in the corresponding powders. Saturation and remnant magnetization increased with increase in grain size, while coercivity demonstrated a drop due to multidomain behavior of crystallites for a given value of x. Saturation magnetization increased and remnant magnetization had a maximum as a function of grain size in dependent of x. In turn, coercivity increased with x independent of grain size. Complex permittivity of the Co-Ni-Zn ferrite films was measured in the frequency range 2-15 GHz. The highest hysteretic heating rate in the temperature range 315-355 K was observed in CoFe2O4. The maximum absorption band shifted from 13 to 11GHz as cobalt content increased from x = 0.1 to 0.2.

Interstitial Nitrogen in Diamond – Optical and EPR Studies

Nitrogen is one of the most common impurities in diamond. On a substitutional site it acts as a deep donor, approximately 1.7 eV below the conduction band. Irradiation of nitrogen containing diamond and subsequent annealing creates the nitrogen vacancy centre, which has recently attracted much attention for quantum information processing application. Another possible product of irradiation and annealing of nitrogen containing diamond is interstitial nitrogen. Presumably, a mobile carbon interstitial migrates to a substitutional nitrogen to produce an interstitial nitrogen complex which may or may not be mobile. The configuration(s) of interstitial nitrogen related defects (e.g. bond centred, [001]-split) are not known. An infra-red (IR) absorption peak at 1450 cm-1 labelled H1a has been associated with an nitrogen interstitial complex. [1] Theoretical modelling suggested that this IR local mode is due to a bond centred nitrogen interstitial [2]. However, more recent modelling [3] suggests that this defect is mobile at temperatures were H1a is stable and instead assign H1a to two nitrogen atoms occupying a single lattice site in a [001]-split configuration. To date no electron paramagnetic resonance (EPR) spectra have been conclusively associated with an interstitial nitrogen defect.

In this study we present data from new EPR and optical absorption studies in combination with uniaxial stress of nitrogen interstitial related defects in electron irradiated and annealed nitrogen doped diamond. These measurements yield symmetry information about the defects allowing us to determine which of the proposed models are possible. EPR spectra of nitrogen interstitial related defects in samples isotopically enriched with 15N are reported and we show that these explain the lack of previous EPR data for these defects. Correlations between the IR absorbance and the integrated intensity of the new EPR defects are studied for varying irradiation doses and annealing temperatures.

Melt Processing and Properties of Polyamide 6/Graphene Nanoplatelet Composites

Graphene, due to its outstanding properties, has become the topic of much research activity in recent years. Much of that work has been on a laboratory scale however, if we are to introduce graphene into real product applications it is necessary to examine how the material behaves under industrial processing conditions. In this paper the melt processing of polyamide 6/graphene nanoplatelet composites via twin screw extrusion is investigated and structure–property relationships are examined for mechanical and electrical properties. Graphene nanoplatelets (GNPs) with two aspect ratios (700 and 1000) were used in order to examine the influence of particle dimensions on composite properties. It was found that the introduction of GNPs had a nucleating effect on polyamide 6 (PA6) crystallization and substantially increased crystallinity by up to 120% for a 20% loading in PA6. A small increase in crystallinity was observed when extruder screw speed increased from 50 rpm to 200 rpm which could be attributed to better dispersion and more nucleation sites for crystallization. A maximum enhancement of 412% in Young's modulus was achieved at 20 wt% loading of GNPs. This is the highest reported enhancement in modulus achieved to date for a melt mixed thermoplastic/GNPs composite. A further result of importance here is that the modulus continued to increase as the loading of GNPs increased even at 20 wt% loading and results are in excellent agreement with theoretical predictions for modulus enhancement. Electrical percolation was achieved between 10–15 wt% loading for both aspect ratios of GNPs with an increase in conductivity of approximately 6 orders of magnitude compared to the unfilled PA6.

CSI 2264: Simultaneous Optical and Infrared Light Curves of Young Disk-bearing Stars in NGC 2264 with CoRoT and Spitzer—Evidence for Multiple Origins of Variability

We present the Coordinated Synoptic Investigation of NGC 2264, a continuous 30 day multi-wavelength photometric monitoring campaign on more than 1000 young cluster members using 16 telescopes. The unprecedented combination of multi-wavelength, high-precision, high-cadence, and long-duration data opens a new window into the time domain behavior of young stellar objects. Here we provide an overview of the observations, focusing on results from Spitzer and CoRoT. The highlight of this work is detailed analysis of 162 classical T Tauri stars for which we can probe optical and mid-infrared flux variations to 1% amplitudes and sub-hour timescales. We present a morphological variability census and then use metrics of periodicity, stochasticity, and symmetry to statistically separate the light curves into seven distinct classes, which we suggest represent different physical processes and geometric effects. We provide distributions of the characteristic timescales and amplitudes and assess the fractional representation within each class. The largest category (>20%) are optical "dippers" with discrete fading events lasting ~1-5 days. The degree of correlation between the optical and infrared light curves is positive but weak; notably, the independently assigned optical and infrared morphology classes tend to be different for the same object. Assessment of flux variation behavior with respect to (circum)stellar properties reveals correlations of variability parameters with Hα emission and with effective temperature. Overall, our results point to multiple origins of young star variability, including circumstellar obscuration events, hot spots on the star and/or disk, accretion bursts, and rapid structural changes in the inner disk. Based on data from the Spitzer and CoRoT missions. The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain.