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Diverse and well-preserved acritarchs are reported from the type section of the Cambrian Hanford Brook Formation at Hanford Brook, southern New Brunswick. This section fills an important gap in acritarch studies by providing the first detailed picture of changing acritarch associations close to the traditional lower–middle Cambrian boundary in Avalonia. Acritarchs from the St Martins Member, at the base of the succession, include Skiagia ciliosa, Heliosphaeridium notatum, H. longum and Liepaina plana and suggest attribution to Cambrian Stage 4. Acritarchs from the Somerset Street Member, in the middle of the formation, include Eliasum llaniscum and Comasphaeridium silesiense. This information adds new biochronological context to an ash bed in the Somerset Street Member previously dated as c. 510 Ma or 508 Ma, and to the endemic trilobites from the same member, including Protolenus elegans. It also places absolute ages on the basal range of stratigraphically important acritarchs. Both the acritarch assemblage and the radiometric age are consistent with a position very close to the traditional lower–middle Cambrian transition and likely within Cambrian Stage 5. Acritarchs from the Long Island Member, at the top of the succession, include additional taxa demonstrating assignment to Cambrian Stage 5. Both the Somerset Street and Long Island members probably correlate with the Morocconus notabilis Zone. The new acritarch species Retisphaeridium striatum Palacios is described. New data are presented on acritarchs from the upper part of the Hell's Mouth Formation, Wales, and correlation proposed with the Long Island Member.
During 1990 we surveyed the southern sky using a multi-beam receiver at frequencies of 4850 and 843 MHz. The half-power beamwidths were 4 and 25 arcmin respectively. The finished surveys cover the declination range between +10 and −90 degrees declination, essentially complete in right ascension, an area of 7.30 steradians. Preliminary analysis of the 4850 MHz data indicates that we will achieve a five sigma flux density limit of about 30 mJy. We estimate that we will find between 80 000 and 90 000 new sources above this limit. This is a revised version of the paper presented at the Regional Meeting by the first four authors; the surveys now have been completed.
A scalable approach for synthesis of ultra-thin (<10 nm) transition metal dichalcogenides (TMD) films on stretchable polymeric materials is presented. Specifically, magnetron sputtering from pure TMD targets, such as MoS2 and WS2, was used for growth of amorphous precursor films at room temperature on polydimethylsiloxane substrates. Stacks of different TMD films were grown upon each other and integrated with optically transparent insulating layers such as boron nitride. These precursor films were subsequently laser annealed to form high quality, few-layer crystalline TMDs. This combination of sputtering and laser annealing is commercially scalable and lends itself well to patterning. Analysis by Raman spectroscopy, scanning probe, optical, and transmission electron microscopy, and x-ray photoelectron spectroscopy confirm our assertions and illustrate annealing mechanisms. Electrical properties of simple devices built on flexible substrates are correlated to annealing processes. This new approach is a significant step toward commercial-scale stretchable 2D heterostructured nanoelectronic devices.
We present the results of an approximately 6 100 deg2 104–196 MHz radio sky survey performed with the Murchison Widefield Array during instrument commissioning between 2012 September and 2012 December: the MWACS. The data were taken as meridian drift scans with two different 32-antenna sub-arrays that were available during the commissioning period. The survey covers approximately 20.5 h < RA < 8.5 h, − 58° < Dec < −14°over three frequency bands centred on 119, 150 and 180 MHz, with image resolutions of 6–3 arcmin. The catalogue has 3 arcmin angular resolution and a typical noise level of 40 mJy beam− 1, with reduced sensitivity near the field boundaries and bright sources. We describe the data reduction strategy, based upon mosaicked snapshots, flux density calibration, and source-finding method. We present a catalogue of flux density and spectral index measurements for 14 110 sources, extracted from the mosaic, 1 247 of which are sub-components of complexes of sources.
We are conducting a large survey of distant clusters of galaxies using radio sources with bent jets and lobes as tracers. These radio sources are driven by AGN and achieve their bent morphologies through interaction with the surrounding gas found in clusters of galaxies. Based on low-redshift studies, these types of sources can be used to identify clusters very efficiently. We present initial results from our survey of 653 bent-double radio sources with optical hosts too faint to appear in the SDSS. The sample was observed in the infrared with Spitzer, and it has revealed ~200 distant clusters or proto-clusters in the redshift range z ~ 0.7 - 3.0. The sample of bent-doubles contains both quasars and radio galaxies enabling us to study both radiative and kinetic mode feedback in cluster and group environments at a wide range of redshifts.
We present results from deep Chandra X-ray observations of the galaxy group NGC 5813. This system shows three pairs of collinear cavities, with each pair associated with an elliptical AGN outburst shock. Due to the relatively regular morphology of this system, and the unique unambiguous detection of three distinct AGN outburst shocks, it is particularly well-suited for the study of AGN feedback and the AGN outburst history. We find that the mean kinetic power is roughly the same for each outburst, and that the total energy associated with the youngest outburst is significantly lower than that of the previous outbursts. This implies that the mean AGN jet power has remained stable for at least 50 Myr, and that the youngest outburst is ongoing. We find that the mean shock heating rate balances the local radiative cooling rate at each shock front, suggesting that AGN outburst shock heating alone is sufficient to offset cooling and establish AGN/ICM feedback within at least the central 30 kpc. Finally, we find non-zero shock front widths that are too large to be explained by particle diffusion, but are instead consistent with arising from broadening of the shock fronts due to propagation through a turbulent ICM with a mean turbulent speed of ~ 70 km s−1.
Significant new opportunities for astrophysics and cosmology have been identified at low radio frequencies. The Murchison Widefield Array is the first telescope in the southern hemisphere designed specifically to explore the low-frequency astronomical sky between 80 and 300 MHz with arcminute angular resolution and high survey efficiency. The telescope will enable new advances along four key science themes, including searching for redshifted 21-cm emission from the EoR in the early Universe; Galactic and extragalactic all-sky southern hemisphere surveys; time-domain astrophysics; and solar, heliospheric, and ionospheric science and space weather. The Murchison Widefield Array is located in Western Australia at the site of the planned Square Kilometre Array (SKA) low-band telescope and is the only low-frequency SKA precursor facility. In this paper, we review the performance properties of the Murchison Widefield Array and describe its primary scientific objectives.
Growth stresses in amorphous SiO2 scales formed during SiC fiber oxidation were calculated. A numerical method using Deal-Grove oxidation kinetics and shear-stress dependent SiO2 viscosity was used. Initial compressive stresses in SiO2 of ∼25 GPa from the 2.2× oxidation volume expansion rapidly relaxes. At >1200°C, viscous flow of amorphous SiO2 further relaxes stress to negligible levels. At 700° - 900°C, axial and hoop stress at the GPa level persist in SiO2 near the SiC-SiO2 interface. Radial expansion of the scale causes hoop stress to become tensile, and axial stresses are driven to tensile values by the Poisson effect. These tensile stresses can be >1 GPa for thick scales formed at lower temperatures on surfaces with high curvature. Approximate analytical expressions for growth stress are discussed. Effects of viscosity variation as well as other assumptions and limitations of the calculation method are discussed.
There is currently no information regarding the genetic diversity of HPV-6 variants circulating in South Africa. The aim of this study was to determine the HPV-6 variants affecting patients with recurrent respiratory papillomatosis, to determine whether mutations correlate with disease severity and identify molecular determinants of virulence with prognostic relevance. HPV-6 variants were identified based on genome changes within the 712-991 bp region encompassing the non-coding region (URR) of the genome, with variations in length resulting from insertions and duplications, and the 453-bp gene encoding the E6 protein. Based on manual comparison of sequence data from the URR, the isolates were identified as HPV-6a and HPV-6vc variants. Three novel HPV-6 variants were identified: one based on a mutation in the E6 region; two based on changes in the URR including a unique substitution detected in three isolates and an insertion and 170-bp duplication in the URR genome in one patient, who had clinical features of severe disease.
The genetically unrelated chick strains Hy-1 and Hy-2, which have been strongly selected for growth rate, both exhibit hyperplasia of the lens epithelium. These two strains and a control strain N, not selected for growth rate, were compared with respect to incorporation of 3H-thymidine and 14C-uridine by freshly excised lenses in culture at different times throughout a 24-h period. The levels of incorporation of label into the lens cells were found to vary according to the time of day. The pattern of diurnal variation in both thymidine and uridine incorporation was found to be strain specific. Hy-1 and Hy-2 showed a greater degree of synchrony than did normal (N) lenses, and the frequency of the peaks of incorporation was also higher. Autoradiography confirmed that only lens epithelium incorporates thymidine during culture and that the number of labelled nuclei depends on the time of day when the lenses were explanted. These data point to genetic control of the cell cycle.
Atomic Force Microscopy (AFM) was employed to probe the internal structure of living HepG2/C3A cells grown on various commercially-available substrates. In order to understand the driving mechanisms behind the different cell morphologies, the surface properties of these substrates was characterized with AFM and related techniques. The roughness of a 10μm×10μm region of a series of substrates was determined and found to be independent of both coating and culture media, with the exception of thick hydrogel-like coatings. Probing with functionalized tips could not distinguish relative degrees of hydrophobicity under cell culture media, presumably because Debye shielding masks the substrate surfaces. Force spectroscopy was performed on the surfaces to determine exposed surface proteins/polymers intrinsic to the substrate and adsorbed from culture media. Preliminary investigation of cell-mediated substrate reconstruction suggests that the cells secrete large (1000kDa) polymeric molecules at the substrate interface.
Why photoreceptors turn over a portion of their photoreceptive
membrane daily is not clear; however, failure to do so properly leads
to retinal degeneration in vertebrates and invertebrates. Little is
known about the molecular mechanisms that regulate shedding and renewal
of photoreceptive membrane. Photoreceptor cells in the lateral eye of
the horseshoe crab Limulus turn over their photoreceptive
membrane (rhabdom) in a brief, synchronous burst in response to dawn
each morning. Transient rhabdom shedding (TRS), the first phase of
rhabdom turnover in Limulus, is triggered by dawn, but
requires a minimum of 3–5 h of overnight priming from the central
circadian clock (Chamberlain & Barlow,
1984). We determined previously that the clock primes the
lateral eye for TRS using the neurotransmitter octopamine (OA) (Khadilkar et al., 2002), and report here that OA
primes the eye for TRS through a Gs-coupled, adenylate
cyclase (AC)/cyclic adenosine 3′,5′-monophosphate
(cAMP)/cAMP-dependent protein kinase (PKA) signaling cascade.
Long-term intraretinal injections (6–7 h @ 1.4 μl/min) of
the AC activator forskolin, or the cAMP analogs Sp-cAMP[S]
and 8-Br-cAMP primed the retina for TRS in eyes disconnected from the
circadian clock, and/or in intact eyes during the day when the
clock is quiescent. This suggests that OA primes the eye for TRS by
stimulating an AC-mediated rise in intracellular cAMP concentration
([cAMP]i). Co-injection of SQ 22,536, an AC
inhibitor, or the PKA inhibitors H-89 and PKI (14-22) with OA
effectively antagonized octopaminergic priming by reducing the number
of photoreceptors primed for TRS and the amount of rhabdom shed by
those photoreceptors compared with eyes treated with OA alone. Our data
suggest that OA primes the lateral eye for TRS in part through
long-term phosphorylation of a PKA substrate.
High-density MOS capacitors have been fabricated with ∼ 30 nF/mm2 specific capacitance on highly-doped Si-wafers with arrays of macropores with ∼ 2 μm diameter. Using the Bosch process  these pores were dry-etched to depths of ∼ 30 μm or more. The enlarged Si-surface thus obtained serves as a substrate for capacitors fabricated by fully MOS-compatible processing.
Wafers were fabricated with a top electrode of poly-Si and Al and ‘ONO’ (i.e. oxide / nitride / oxide) dielectric stacks showing 7–10 MV/cm electrical breakdown field and leakage < 1 nA/mm2 @ 20 V. These wafers were thinned to 380 μm and sawn into dies, representing 40 nF capacitors. Typically low loss factors such as ESR < 50 mΩ and ESL < 20 pH and resonance frequencies of ∼ 0.1 GHz were found for 40 nF capacitor dies. Next, 40 nF dies were mounted by wire bonding on Al2O3 or laminate substrate as supply-line decoupling capacitors in complete GSM power amplifier test modules. RF decoupling and transmission were measured and compared to identical test modules with conventional discrete ceramic capacitors. The MOS capacitors showed very efficient decoupling, resulting in superior signal stability as measured in the 0 – 1 GHz range (less noisy, free from oscillations).
The new capacitor is very suitable for integrated decoupling purposes, e.g. supply-line decoupling in RF wireless communication and analog and mixed-signal systems.