Characterisation of the anisotropy of pyrolytic carbon coatings and the graphite matrix in fuel compacts by two modulator generalised ellipsometry and selected area electron diffraction

The safety and performance of the fuel of the high temperature reactor is largely controlled by the anisotropy of the pyrolytic carbon (PyC) coatings in the tristructural isotropic (TRISO) coated fuel particles and the graphite matrix of its fuel compacts. The optical anisotropy factor (OPTAF) and diattenuation of several PyC coatings were characterised by two modulator generalised ellipsometry microscopy. These results were compared to the texture values obtained from selected area electron diffraction patterns by transmission electron microscopy. The differences between “nano-, micro- and macro”-anisotropy are discussed. We established that previously observed sudden increase of PyC coating failure under neutron irradiation at OPTAF values above 1.04 originates from the development of a microstructure with polyhedral growth features and graphene planes with a single preferred orientation within these microstructural features. Three graphite fuel compacts (two cylindrical and one pebble) were also characterised. We have identified that the use of an overcoating on the TRISO particles can result in the formation of a macro-anisotropic area.     

Generation of antifouling layers on stainless steel surfaces by plasma‐enhanced crosslinking of polyethylene glycol

Polyethylene glycol (PEG) structures were deposited onto stainless steel (SS) surfaces by spin coating and argon radio frequency (RF)‐plasma mediated crosslinking. Electron spectroscopy for chemical analysis (ESCA) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR) indicated the presence of  CH₂ CH₂ O structure and C C C linkage, as a result of the plasma crosslinking, on PEG‐modified SS surfaces. Scanning electron microscopy (SEM) indicated complete deposition, and water contact angle analysis revealed higher hydrophilicity on PEG‐modified surfaces compared to unmodified SS surfaces. Surface morphology and roughness analysis by atomic force microscopy (AFM) revealed smoother SS surfaces after PEG modification. The evaluation of antifouling ability of the PEG‐modified SS surfaces was carried out. Compared to the unmodified SS, PEG‐modified surfaces showed about 81–96% decrease in Listeria monocytogenes attachment and biofilm formation (p < 0.05). This cold plasma mediated PEG crosslinking provided a promising technique to reduce bacterial contamination on surfaces encountered in food‐processing environments. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 485–497, 2005     

Functional MRI reveals spatially specific attentional modulation in human primary visual cortex

Selective visual attention can strongly influence perceptual processing, even for apparently low-level visual stimuli. Although it is largely accepted that attention modulates neural activity in extrastriate visual cortex, the extent to which attention operates in the first cortical stage, striate visual cortex (area V1), remains controversial. Here, functional MRI was used at high field strength (3 T) to study humans during attentionally demanding visual discriminations. Similar, robust attentional modulations were observed in both striate and extrastriate cortical areas. Functional mapping of cortical retinotopy demonstrates that attentional modulations were spatially specific, enhancing responses to attended stimuli and suppressing responses when attention was directed elsewhere. The spatial pattern of modulation reveals a complex attentional window that is consistent with object-based attention but is inconsistent with a simple attentional spotlight. These data suggest that neural processing in V1 is not governed simply by sensory stimulation, but, like extrastriate regions, V1 can be strongly and specifically influenced by attention.     

Aplasia and hypoplasia of the vestibulocochlear nerve: diagnosis with MR imaging

PURPOSE: To introduce aplasia or hypoplasia of the vestibulocochlear nerve (VCN) as a possible cause of hearing loss and to identify the magnetic resonance (MR) imaging characteristics of this entity. MATERIALS AND METHODS: In seven patients with congenital deafness or unexplained sensorineural hearing loss, MR imaging enabled diagnosis of aplasia or hypoplasia of the VCN. Axial (0.7-mm) three-dimensional Fourier transformation-constructive interference in steady state (3DFT-CISS) images and parasagittal reconstruction images perpendicular on the course of the VCN were obtained. Twenty normal inner ears were also studied; their findings were compared with those of the patients. RESULTS: The facial nerve and inferior and superior vestibular and cochlear branches of the VCN were identified on the MR images in the 20 normal inner ears. Aplasia of the VCN was detected in two patients with normal labyrinths but with a severe stenosis of the internal auditory canal. A common VCN with absence of the cochlear branch was found bilaterally in two patients with a congenital malformation of the labyrinth. A common VCN with absence or hypoplasia of the cochlear branch was found in three patients with normal internal auditory canals and labyrinths. CONCLUSION: Submillimetric gradient-echo images (eg, 3DFT-CISS) should always be used to exclude aplasia or hypoplasia of the cochlear branch of the VCN in all cochlear implant candidates and patients with congenital deafness. This entity, which can occur with or without associated labyrinthine malformation, should be confirmed in two planes.     

e-Agricultural innovation using a human-centred systems lens,proposed conceptual framework

Historically, farmers have been amongst the most innovative people in the world. However, agriculture now lags behind other sectors in its uptake of new information technologies for the control and automation of farming systems. In spite of decades of research into innovation, we still do not have a good understanding as to why this is the case. With the globalisation of food markets, IT adoption in agricultural communities is perceived to be increasingly important by policy makers. As the most marginalised of rural communities, it is self-evident that agricultural communities in less developed countries are most in need of these systems. This paper proposes a new integral systems framework of e-agricultural adoption and innovation in less developed countries. It opens up a new avenue of research for control and automation systems theory and practice, which informs policy in respect of e-readiness of rural communities.     

Gain and noise saturation of wide-band InAs-InP quantum dash optical amplifiers: model and experiments

We present a theoretical model for gain and noise saturation in quantum dash (QDash) semiconductor optical amplifiers. The model is based on the density matrix formalism and addresses static saturation spectra. The calculations are confirmed by a series of experiments which highlight the unique properties of these amplifiers. We demonstrate a high gain, a wide bandwidth, and high saturation power. The saturation spectrum is shown to be asymmetric, emphasizing saturation at short wavelength. The asymmetry stems from the high energy tail of the density of state function in those quantum wire (QWire) like gain media as well as from the interactions with the wetting layer.     

Structure of yttria stabilized zirconia beads produced by gel supported precipitation

Yttria stabilized zirconia (YSZ) is one of the inert matrix candidates selected for investigation as host matrix for minor actinide (MA) transmutation. The structural properties of (Zr_0.84, Y_0.16)O_1.92 beads prepared by a sol–gel method for MA infiltration, are characterized as calcined (850 °C) and sintered (1,600 °C) beads. The calcined YSZ beads are fine-grained and homogenous over the entire sphere and are surrounded by a uniform outer layer of approximately 30 μm thickness. After sintering at 1,600 °C, the beads are compacted to 51% of their initial volume and exhibit a granular structure. The thermal expansion is nearly linear for the calcined material, but shows a parabolic behavior for the sintered (1,400 °C) beads. In addition, the thermal expansion of calcined material is 20–25% less than after sintering. During heating up to 1,400 °C, two processes can be distinguished. The first occurs between 900 and 1,000 °C and is related to an increase in unit cell order. The second process involves grain-growth of the less crystalline calcined material between 1,100 and 1,300 °C. These results have implications for preparation of YSZ and its use as an inert MA transmutation matix.     

Development of a new electroplating process for Ni-W alloy deposits

In the present work, the effect of the complexing agents citrate, glycine and triethanolamine (TEA) on the electrodeposition of Ni-W layers from electrolytes based on NiSO₄ and Na₂WO₄, is investigated. The investigations include measurement of the current efficiencies, determination of the tungsten content in the electrodeposits (by energy dispersive X-ray analysis), voltammetry studies and characterization of complex formation by UV-spectrometry. High W content and current efficiency could be realized by using electrolytes containing all of the three complexing agents. The results show that small amounts of glycine in a citrate-triethanolamine based electrolyte positively influences both the mass-transfer and the deposition potential.