Comparative performance of chloride attenuating and corrosion inhibiting systems for reinforced concrete

This paper reports a laboratory-based study carried out to compare the performance of various proprietary concrete protection systems, designed to reduce chloride ingress and reinforcement corrosion. These include: controlled permeability formwork (CPF), a silane/siloxane hydrophobic surface treatment (S/S), an integral liquid waterproofing admixture (WP) and a corrosion-inhibiting chemical admixture (CI). Tests were carried out on a Portland cement (PC) concrete (40 N/mm² design strength) for chloride diffusion index (using a two-cell compartment accelerated test) and, under cyclic wetting and drying conditions, total chloride content at cover depth (25 mm) and corrosion of carbon steel in reinforced concrete specimens (using half-cell potential and corrosion current density (polarisation resistance) measurements). The results indicate that for all protection systems, resistance to chloride ingress was improved, with the greatest benefits noted for the S/S and CPF concretes. Corrosion levels occurring for these generally followed the ranking of chloride ingress rates. The CI was found to reduce the rate of chloride ingress and to give lowest corrosion current densities in relation to chloride contents. This system appeared to provide best overall performance. The practical implications of the results are considered in terms of equivalence of the systems to an increase in design strength or cover depth,i.e. parameters used for specifying concrete durability in standards, and the wider issues relating to their selection and use are reviewed.     

Development of a measure of drinking and driving expectancies for youth.

The present study constructs and provides initial validation for a measure of positive expectancies for drinking and driving for use with adolescents and young adults (PEDD-Y). In Study 1, items were generated through open-ended responses from high school- and college-age youth. Data collected from a 2nd sample of college students (n = 404) identified a 29 item, 4 factor questionnaire. Two of the PEDD-Y factors (Convenience, Avoiding Consequences) explained additional variance in drinking and driving behavior above and beyond other cognitions about drinking and driving. Study 2 extended these results to a high school sample (n = 185). Study 3 demonstrated test-retest reliability of the PEDD-Y in college-age youth (n = 165). These results provide initial evidence for the utility of the PEDD-Y in assessing drinking and driving risk in adolescents and college students. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Blinking suppression and intensity recurrences in single CdSe-oligo(phenylene vinylene) nanostructures: experiment and kinetic model

We report time-resolved single molecule fluorescence imaging of individual CdSe quantum dots that are functionalized with oligomeric conjugated organic ligands. The fluorescence intensity trajectories from these composite nanostructures display both a strong degree of blinking suppression and intensity fluctuations with characteristic recurrence times on the order of 10-60?s. In addition, fluorescence decay rate measurements of individual hybrid nanostructures indicate significantly modified non-radiative quantum dot decay rates relative to conventional ZnS-capped CdSe quantum dots. We show that a modified diffusive reaction coordinate model with slow fluctuations in quantum dot electron energies (1S(e), 1P(e)) can reproduce the experimentally observed behaviour.     

Organochlorine levels in maternal and umbilical cord blood plasma in Arctic Canada

A baseline for exposure to organochlorine and metal contaminants has been established for mothers and newborns in the Northwest Territories and Nunavut areas of Arctic Canada. Maternal and umbilical cord blood plasma organochlorine levels are described for Inuit, Dene, Métis, Caucasian and Other non-Aboriginal participants. Overall, 523 women volunteered to participate by giving their written informed consent between May 1994 and June 1999, resulting in the collection of 386 maternal blood samples, 407 cord blood samples and 351 maternal/cord pairs. Nearly half of all the participants regularly smoked cigarettes, including 77% of the Inuit participants. Maternal and cord results are presented for PCBs (as Aroclor 1260 and 14 congeners) and organochlorine pesticides, including p,p'-DDT, p,p'-DDE, beta-hexachlorocyclohexane (beta-HCH), hexachlorobenzene (HCB), cis and trans nonachlor, heptachlor epoxide, oxychlordane, mirex, dieldrin and toxaphene. Maternal PCB levels (as Aroclor 1260) averaged 4.42 (+/-9.03) microg/l in Inuit, which was 3.3 times higher than those found in Dene/Métis, and 3.4 times higher than levels in Caucasians. Mean DDE levels were 2.8 times higher in the Other non-Aboriginal group (Chinese, Filipino, East Indian and multiple ethnicity) than in the Inuit group, at 3.99 microg/l and 1.42 microg/l, respectively. Cord blood PCB levels (as Aroclor 1260) averaged 1.16 (+/-2.42) microg/l for Inuit participants, which was 3.3-4 fold higher than the other ethnic groups. PCBs, p,p'-DDE and hexachlorobenzene were detected in all maternal samples, and p,p'-DDE was detected in all cord samples. Regression coefficients for maternal/cord pairs are presented for selected organochlorines. Other results from this study, including maternal and cord metals data, will be presented elsewhere.     

The analysis of halogenated acetic acids in dutch drinking water

Halo-acetic acids are produced during chlorine disinfection of drinking water. Besides the well-known dichloro-, and trichloroacetic acid, brominated and mixed chloro/bromo acetic acids are also produced. A method was developed to determine all halo-acetic acids. This method was applied for the analysis of 20 drinking waters prepared from different source waters. Halo-acetic acids were found in all drinking waters prepared from surface water while they could not be detected in drinking waters prepared from ground water. The acid concentrations were in the range of 0–14.7 μg/l and dibromoacetic acid was found to be the most prominent halo-acetic acid in chlorinated waters. Brominated acetic acids accounted for 65% of the total acid concentration showing that brominated compounds form a large part of the chlorination products. The total halo-acetic acid concentration correlated positively with the chlorine-to-carbon ratio and with the adsorbable organic halogen, to which it accounted for 15%.     

Synthesis and characterization of a series of poly(alkylene carbonate) macrodiols and the effect of their structure on the properties of polyurethanes

A series of polycarbonate and copolycarbonate macrodiols was prepared by using an ester interchange reaction with ethylene carbonate and diols such as 1,6-hexanediol, 1,10-decanediol, 2,2-diethyl-1,3-propanediol, 1,4-cyclohexanedimethanol, and 1,3-bis(4-hydroxybutyl)-1,1,3,3-tetramethyldisiloxane. The diols were chosen to prepare a series of macrodiols with different structural features including linear, branched, rigid, and flexible. The macrodiols were characterized by ¹H- and ¹³C-NMR spectroscopy and DSC. The commercial macrodiol based on 1,6-hexanediol exhibited a high level of crystallinity, while with the exception of 1,10-decanediol–based copolycarbonates all the others were completely amorphous. 1,10-Decanediol–based materials showed partial crystallinity under subambient conditions. A series of polyurethane elastomers with a constant hard segment percentage (40 wt %) was prepared using 4,4′-methylenediphenyl diisocyanate and 1,4-butanediol as the hard segment. Tensile test results and Shore hardness measurements demonstrated that polyurethanes based on polycarbonate macrodiols prepared from 1,3-bis(4-hydroxybutyl)-1,1,3,3-tetramethyldisiloxane had the lowest modulus and hardness of the series of polyurethanes. The remaining polyurethanes had high tensile strength with poor elasticity. The morphology of the polyurethanes, as determined by DSC analysis, varied from completely phase-mixed to well phase-separated structures. Polyurethanes based on macrodiols prepared from 1,3-bis(4-hydroxybutyl)-1,1,3,3-tetramethyldisiloxane showed good phase-separated morphology, with sharp hard segment melting endotherms and soft segment glass transitions close to that of the pure soft segment. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1621–1633, 1998     

Morphology–property relationships in ABS/PET blends. II. Influence of processing conditions on structure and properties

The effect of processing temperature on the low-speed tensile and high-speed impact properties of novel ABS/PET blends was investigated. In agreement with the conclusions from related studies of ABS/PC blends, it appears that catalytic impurities in the ABS accentuate the propensity of PET for chain scission. Due to the cocontinuous structure of the blend, the hydrolytic or thermomechanical degradation of the PET results in a dramatic loss in mechanical properties which can be explained by the entanglement theory for fracture and the Orowan brittle–ductile hypothesis. © 1996 John Wiley & Sons, Inc.     

Orthogonal Noise Annihilation for FTIR Spectroscopy in Fire Gas Analysis

Fourier Transformed Infrared (FTIR) spectroscopy may be used to monitor the evolved gases from a furniture calorimeter, but if concentration–time profiles are needed, compromises between spectral resolution, time resolution and sensitivity may have to be made, and the presence of significant noise levels limits the information that can be obtained from the infrared spectra. In this paper we demonstrate that the data may be satisfactorily treated by factor analysis to identify and reject factors attributable to noise. Subsequent reconstruction produces the original spectra with little or no noise and without significant loss of information. The reconstructed spectra were found to contain useful qualitative information even for the background spectra. By comparison, the traditional method of signal averaging for noise reduction not only leads to inferior spectra but also has a substantial disadvantage for fire gas monitoring because it leads to loss of information in poor time resolution, limiting the applicability of the FTIR spectroscopy to follow the combustion process.     

Metabolism of phospholipid in mammary gland: I. The supply of phospholipid for milk synthesis in the rat and goat

Data presented in this study demonstrate that under normal physiological conditions milk phospholipids in the rat and the goat originate predominantly, if not totally, by de novo synthesis within the mammary gland. Evidence to support this has been obtained for the goat by measurement of P³²-phosphate incorporation into milk phospholipids, and in the rat by measurement of P³²-phosphate incorporation and by feeding radioactive phospholipid to measure the incorporation of serum phospholipids into milk. The latter experiment showed that the fatty acid portion of the dietary phospholipid can readily be utilized by the mammary gland for triglyceride synthesis, but that the contribution of the serum phospholipid “backbone” to milk phospholipid is minimal.     

Energy‐dispersive X‐ray fluorescence spectrometry as a tool for the rapid determination of the five major minerals (Na,Mg, K,P and Ca) in skim milk powder

Milk and dairy products are comprised of a complex matrix of components that can interfere with analysis and, as a result, are often not suitable for direct introduction into analytical instruments. Energy‐dispersive X‐ray fluorescence spectrometry (EDXRF) can bypass time‐consuming preparation steps, with potential for rapid, onsite analysis of minerals. In this study, five major milk minerals, sodium, magnesium, potassium, phosphorus and calcium, were quantified in dairy powders, using EDXRF, and the systemic bias of the method was evaluated by Bland–Altman analysis. No significant systemic bias was observed for the quantification of sodium, magnesium, potassium and phosphorus, meaning that EDXRF has potential to be used as a rapid offline analytical technology suitable for the analysis of these minerals in skim milk powders.