Effect of Mixture Composition on Washout Resistance of Highly Flowable Underwater Concrete

The underwater casting of relatively thin lifts of concrete in water requires the proportioning of highly flowable concrete that can resist water dilution and segregation and spread readily into place. An investigation was carried out to determine the effects of antiwashout admixture concentration, water-cementitious materials ratio, and binder composition on the washout resistance of highly flowable concrete. Two main types of antiwashout admixtures were used: 1) a powdered welan gum at concentrations of 0.07 and 0.15% (by mass of binder); and 2) a liquid-based cellulosic admixture with dosages up to 1.65 L/100 kg of binder. The water-cementitious materials ratios were set at 0.41 and 0.47, corresponding to high-quality underwater concrete. Four binder compositions were used: a standard Canadian Type 10 cement, the same cement with 10% silica fume replacement, the cement with 50% granulated blast-furnace slag replacement, and a ternary cement containing 6% silica fume and 20% Class F fly ash. The concentrations of anti-washout admixture have direct impact on washout resistance. For a given washout loss, greater slump flow consistency can be achieved with the increases in anti-washout admixture concentration and decreases in water-binder ratio. The washout mass loss can be reduced, for a given consistency

Preparation and characterization of Poly(vinyl alcohol) nanocomposites made from cellulose nanofibers

A method using a combination of ball milling, acid hydrolysis, and ultrasound was developed to obtain a high yield of cellulose nanofibers from flax fibers and microcrystalline cellulose (MCC). Poly(vinyl alcohol) (PVA) nanocomposites were prepared with these additives by a solution-casting technique. The cellulose nanofibers and nanocomposite films that were produced were characterized with Fourier transform infrared spectrometry, X- ray diffraction, thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy. Nanofibers derived from MCC were on average approximately 8 nm in diameter and 111 nm in length. The diameter of the cellulose nanofibers produced from flax fibers was approximately 9 nm, and the length was 141 nm. A significant enhancement of the thermal and mechanical properties was achieved with a small addition of cellulose nanofibers to the polymer matrix. Interestingly, the flax nanofibers had the same reinforcing effects as MCC nanofibers in the matrix. Dynamic mechanical analysis results indicated that the use of cellulose nanofibers (acid hydrolysis) induced a mechanical percolation phenomenon leading to outstanding and unusual mechanical properties through the formation of a rigid filler network in the PVA matrix. X-ray diffraction showed that there was no significant change in the crystallinity of the PVA matrix with the incorporation of cellulose nanofibers. © 2009 Wiley Periodicals, Inc.

Near infrared electroluminescence from neodymium complex-doped polymer light emitting diodes

Organic light emitting diode devices employing organometallic Nd(9-hydroxyphenalen-1-one)(3) complexes as near infrared emissive dopants dispersed within poly(N-vinylcarbazole) (PVK) host matrices have been fabricated by spin-casting layers of the doped polymer onto glass/indium tin oxide (ITO)/3,4-polyethylene-dioxythiophene-polystyrene sulfonate (PEDOT) substrates. Room temperature electroluminescence, centered at similar to 1065 nm. was observed from devices top contacted by evaporated aluminum or calcium metal cathodes and was assigned to transitions between the F-4(3/2) -> I-4(11/2) levels of the Nd3+ ions. In particular, a near infrared irradiance of 8.5 nW/mm(2) and an external quantum efficiency of 0.007% was achieved using glass/ITO/PEDOT/PVK:Nd(9-hydroxyphenalen-1-one)(3)/Ca/Al devices. (c) 2005 Elsevier B.V. All rights reserved.

Narrow bandwidth red electroluminescence from solution-processed lanthanide-doped polymer thin films

Narrow bandwidth red electroluminescence from OLED devices fabricated using a simple solution-based approach is demonstrated. A spin-casting method is employed to fabricate organic light emitting diode (OLED) devices comprising a poly(N-vinylcarbazole) (PVK) host matrix doped with a europium beta-diketonate complex, Eu(dbM)(3)(Phen) (dibenzoylmethanate, dbm; 1,10-phenanthroline, Phen) on glass/ indium tin oxide (ITO)/3,4-polyethylene-dioxythiophene-polystyrene sulfonate (PEDOT) substrates. Saturated red europium ion emission, based on the (5)Do ->F-7(2) transition, is centered at a wavelength of 612 nm with a full width at half maximum of 3.5 rim. A maximum external quantum efficiency of 6.3 x 10(-2) cd/A (3.1 X 10(-2)%) and a maximum luminance of 130 cd/M-2 at 400 mA/cm(2) and 25 V is measured for ITO/PEDOT/PVK:Eu(dbM)3(Phen)/Ca/Al devices. This measured output luminance is comparable to that of devices fabricated using more sophisticated small molecule evaporation techniques. (c) 2005 Elsevier B.V All rights reserved.

'Last Vegas?'

This article, and the research out of which it springs, has a number of points of origin; it may also have more than one point of conclusion even as it argues that the current manifestation of Las Vegas could well be read as its last. This is not to say that Las Vegas will cease to create its new versions of itself; after all, this is one of the main sustaining factors of Las Vegas’ success in the last two decades as a new Strip on Las Vegas Boulevard has arisen from the demolitions and redesigns of the original Las Vegas Strip of the 1950s and 1960s. What is argued for here is a reading of Vegas as a terminal point within American culture and particularly within its visual realms. Las Vegas’ place within the dynamics of American visual and exhibition culture comes as the latest in a sequence which, since the nineteenth century, has included among its manifestations World’s Fairs, side shows, freak shows and travelling carnivals. America’s experiments in the visual domain have been updated in both the twentieth- and twenty-first centuries in a variety of spectacular forms and entertainment zones (Disneyland, EPCOT, the new Las Vegas). Vegas is the ultimate incarnation of a carnivalised display culture, the city’s casino Strip reclothed primarily as a theme park for digital camera-toting tourists than as a resort for dedicated gamblers. The possibility that the current incarnation of Las Vegas of late 2009 and 2010 will be the last Vegas hovers as a spectral remnant of the economic downturn and financial collapse of 2008, marked by the unfinished skeletons of projected new casino hotels on Las Vegas Boulevard and by a sudden reversal of fortune for the nation’s favourite gaming location.

Perturbed frequency-selective surfaces fabricated on large thin polymer membranes for multiband infrared applications

The design, fabrication, and characterization of single-screen perturbed frequency-selective surfaces (FSS) at infrared frequencies for single and multiband applications are reported. Single-band FSS based on parallel strips have been perturbed by decreasing the length of every second strip within the array in order to achieve dual band-stop responses. The same principle has been extended to design FSS exhibiting tri- and quadreflection bands. In addition, strip FSSs have been perturbed by replacing every second strip for a metallic ring, resulting in dual-band filters with different polarization responses of the bands. These designs have been fabricated on large thin polyimide membranes using sacrificial silicon wafers. An oxide interlayer between the sacrificial silicon wafer and the polyimide membrane is employed to stop the silicon etching and is wet etched subsequently by a solution of ammonium fluoride and acetic acid that does not attack either the polyimide membrane or the aluminium FSS elements. Fourier transform infrared spectroscopy measurements are presented to validate the predicted responses of the fabricated prototypes.

Missing the targets and being misunderstood: Child phonology and interactive problems

Effects of vowel variation on interaction are considered, with particular relevance to their role in conversational breakdown. The effect of speaker knowledge and experience is noted as a variable in developmental progress which must inform profiling decisions, and the need for appropriate taxonomies of speech varieties is emphasized as a precursor to clinical and educational assessments. It is noted, too, that a shared sociolinguistic background between speaker and listener does not always resolve difficulties arising from non-target realizations, casting some doubt on ideas that assessors always possess a guaranteed sense of phonological variability and its effects. Hence, an informed understanding of phonological variation, rather than merely awareness that such variation exists, is advocated.

Order without law? An anatomy of Hamas security: The Executive Force (Tanfithya)

In the struggle to assert and consolidate its power, the Hamas movement of the Palestinian territories has devised several strategies for control. In recognition that control of security remains a key goal for any power-seeker, following its election victory in January 2006, Hamas entered into a fierce and ultimately successful conflict with Fatah for control of the Palestinian Authority Ministry of Interior and Palestinian Security Forces (PSF) in the Gaza Strip. One way in which Hamas was able to achieve this objective was through the creation of its own internal ‘police’ force called the Tanfithya (Executive Force or EF). This article details an anatomy of the EF and the implications of this force in terms of Hamas' confrontation with opponents and its attempts at governance. It also examines the extent to which the EF can be considered to be a model of Islamic policing and its impact on secular rivals in the Gaza Strip.

Passive Intermodulation in Printed Lines: Effects of Trace Dimensions and Substrate

A comprehensive experimental study was performed to identify and discriminate mechanisms contributing to passive intermodulation (PIM) in microstrip transmission lines. The effects of strip length and width, and substrate materials on PIM performance of printed lines were investigated in the GSM900, DCS1800 and UMTS frequency bands. The major features of the experiment design, sample preparation and test setup are discussed in detail. The measurement results have demonstrated that the PIM level cumulatively grows on the longer microstrip lines and decreases on wider strips and, thus, indicated that the distributed resistive nonlinearity of the printed traces represents the dominant mechanism of intermodulation generation in the printed lines on PTFE-based substrates. © 2009 The Institution of Engineering and Technology.

Determination of the heat transfer coefficient at the metal–die interface for high pressure die cast AlSi9Cu3Fe

When simulating the High Pressure Die Casting ‘HPDC’ process, the heat transfer coefficient ‘HTC’ between the casting and the die is critical to accurately predict the quality of the casting. To determine the HTC at the metal–die interface a production die for an automotive engine bearing beam, Die 1, was instrumented with type K thermocouples. A Magmasoft® simulation model was generated with virtual thermocouple points placed in the same location as the production die. The temperature traces from the simulation model were compared to the instrumentation results. Using the default simulation HTC for the metal–die interface, a poor correlation was seen, with the temperature response being much less for the simulation model. Because of this, the HTC at the metal–die interface was modified in order to get a better fit. After many simulation iterations, a good fit was established using a peak HTC of 42,000 W/m2 K, this modified HTC was further validated by a second instrumented production die, proving that the modified HTC gives good correlation to the instrumentation trials. The updated HTC properties for the simulation model will improve the predictive capabilities of the casting simulation software and better predict casting defects.

Time-resolved optical spectroscopy of the pulsating DA white dwarf HS0507+0434B - New constraints on mode identification and pulsation properties

We present a detailed analysis of time-resolved optical spectra of the ZZ Ceti white dwarf, HS 0507+0434B. Using the wavelength dependence of observed mode amplitudes, we deduce the spherical degree, l, of the modes, most of which have l = 1. The presence of a large number of combination frequencies (linear sums or differences of the real modes) enabled us not only to test theoretical predictions but also to indirectly infer spherical and azimuthal degrees of real modes that had no observed splittings. In addition to the above, we measure line-of-sight velocities from our spectra. We find only marginal evidence for periodic modulation associated with the pulsation modes: at the frequency of the strongest mode in the lightcurve, we measure an amplitude of 2.6 +/- 1.0 kms(-1), which has a probability of 2% of being due to chance; for the other modes, we find lower values. Our velocity amplitudes and upper limits are smaller by a factor of two compared to the amplitudes found in ZZ Psc. We find that this is consistent with expectations based on the position of HS 0507+0434B in the instability strip. Combining all the available information from data such as ours is a first step towards constraining atmospheric properties in a convectionally unstable environment from an observational perspective.

Determination of the molar extinction coefficient for the ferric reducing/antioxidant power assay

The FRAP reagent contains 2,4,6-tris(2-pyridyl)-s-triazine, which forms a blue-violet complex ion in the presence of ferrous ions. Although the FRAP (ferric reducing/antioxidant power) assay is popular and has been in use for many years, the correct molar extinction coefficient of this complex ion under FRAP assay conditions has never been published, casting doubt on the validity of previous calibrations. A previously reported value of 19.800 is an underestimate. We determined that the molar extinction coefficient was 21,140. The value of the molar extinction coefficient was also shown to depend on the type of assay and was found to be 22,230 under iron assay conditions, in good agreement with published data. Redox titration indicated that the ferrous sulfate heptahydrate calibrator recommended by Benzie and Strain, the FRAP assay inventors, is prone to efflorescence and, therefore, is unreliable. Ferrous ammonium sulfate hexahydrate in dilute sulfuric acid was a more stable alternative. Few authors publish their calibration data, and this makes comparative analyses impossible. A critical examination of the limited number of examples of calibration data in the published literature reveals only that Benzie and Strain obtained a satisfactory calibration using their method. (C) 2011 Elsevier Inc. All rights reserved.

Physicochemical and drug diffusion analysis of rifampicin containing polyethylene glycol-poly(epsilon-caprolactone) networks designed for medical device applications

This study reports the physicochemical and drug diffusion properties of rifampicin containing poly(epsilon-caprolactone) (PCL)/polyethylene glycol (PEG) networks, designed as bioactive biomaterials. Uniquely, the effects of the states of both rifampicin and PEG and the interplay between these components on these properties are described. PCL matrices containing rifampicin (1-5%, w/w) and PEG 200 (0-15%, w/w) were prepared by casting from an organic solvent (dichloromethane). The films were subsequently characterized in terms of their thermal/thermorheological, surface and tensile properties, biodegradation and drug diffusion/release properties. Incorporation of PEG and/or rifampicin significantly affected the tensile and surface properties of PCL, lowering the ultimate tensile strength, % elongation at break, Young modulus and storage and loss moduli. Both in the absence and presence of PEG, solubilisation of rifampicin within the crystalline domains of PCL was observed. PEG was present as a dispersed liquid phase. The release of rifampicin (3% loading) was unaffected by the presence of PEG. Similarly the release of rifampicin (5%) was unaffected by low concentrations of PEG (5-10%) however, at higher loadings, the release rate of rifampicin was enhanced by the presence of PEG. Rifampicin release (10% loading) was enhanced by the presence of PEG in a concentration dependent fashion. These observations were accredited to enhanced porosity of the matrix. In all cases, diffusion-controlled release of rifampicin occurred which was unaffected by polymer degradation. This study has uniquely illustrated the effect of hydrophilic pore formers on the physicochemical properties of PCL. Interestingly, enhanced diffusion controlled release was only observed from biomaterials containing high loadings of PEG and rifampicin (5, 10%), concentrations that were shown to affect the mechanical properties of the biomaterials. Care should therefore be shown when adopting this strategy to enhance release of bioactive agents from biomaterials. (C) 2011 Elsevier B.V. All rights reserved.

APEASPFIRFamide, a novel FMRFamide-related decapeptide from Caenorhabditis elegans: Structure and myoactivity

To date, 9 FMRF amide-related peptides (FaRPs) have been identified in Caenorhabditis elegans. Eight of these peptides are encoded on the flp-1 gene. However, AF2 (KHEYLRF amide) which was not co-encoded was the most abundant FaRP identified in ethanolic extracts. Further radioimmunometrical screening of acidified ethanol extracts of C. elegans has revealed the presence of other novel FaRPs, which are not encoded on the flp-l gene. One of these peptides has been isolated by sequential rpHPLC and subjected to Edman degradation analysis and gas-phase sequencing and the unequivocal primary structure of the decapeptide Ala-Pro-Glu-Ala-Ser-Pro-Phe-Ile-Arg-Phe-NH2 was determined following a single gas-phase sequencing run. The molecular mass of the peptide was found to be 1133.7 Ha, determined using a time-of-flight mass spectrometer. Synthetic replicates of this peptide were found to induce a profound relaxation of both dorsal and ventral somatic muscle-strip preparations of Ascaris suum with a threshold for activity of 10 nM. The inhibitory response was not dependent on the presence of nerve cords, indicating a post-synaptic site-of-action. The relaxation was Ca++- and Cl--independent but was abolished in high-KI medium and could be distinguished from those of other inhibitory nematode FaRPs, including PF1 (SDPNFLRFamide)and PF1 (KPNFIRF amide). (C) 1997 Academic Press.