Corrosion scales play an important role in modifying water quality in drinking water distribution systems. The corrosion scales from old iron/steel pipes were analyzed for their structure and ...composition. Scales were studied both before and after drying, and goethite, magnetite and lepidocrocite were identified as the primary constituents of the dried samples. High concentrations of readily soluble ferrous phases were detected in wet-scale samples. The corrosion scales had a shell-like, enveloping layer, covering porous deposits of iron oxide phases. Our studies were able to identify important differences between corrosion scales found in two different water distribution systems. Further studies are needed to establish the role of corrosion scales in the mechanism of iron release from corroded pipes.
1) To update the 2006 systematic review and meta-analysis by Nnoaham & Clarke exploring the association between serum vitamin D and risk of active tuberculosis (TB) following discrepant evidence; and ...2) to identify whether TB and vitamin D are associated in rural Afghanistan.
Systematic review and meta-analysis of studies published between January 1980 and June 2014 using Nnoaham & Clarke's methodology. For this case-control study, 90 age- and sex-matched pairs were recruited from rural provinces, and blood 25-hydroxyvitamin D concentrations were measured using enzyme-linked immunosorbent assay.
Sixteen studies were eligible for review. Eleven showed differences between vitamin D levels in TB patients and controls, two showed partial differences and three showed none. Studies on African and European populations show lower vitamin D levels in TB patients, but results from Asia vary. No significant differences were found in vitamin D levels in our rural Afghan population. Controls had a higher body mass index (BMI) (mean control BMI 21.50 kg/m(2), mean case BMI 18.86 kg/m(2), P < 0.001), and were more likely to have been employed (40% of controls, 15.6% of cases, P = 0.002).
Genetic differences may account for the differences among study results in the systematic review. Vitamin D levels are not associated with TB among Afghans living in these rural provinces.
Iron release from corroded iron pipes is the principal cause of “colored water” problems in drinking water distribution systems. The corrosion scales present in corroded iron pipes restrict the flow ...of water, and can also deteriorate the water quality. This research was focused on understanding the effect of dissolved oxygen (DO), a key water quality parameter, on iron release from the old corroded iron pipes.
Corrosion scales from 70-year-old galvanized iron pipe were characterized as porous deposits of Fe(III) phases (goethite (
α-FeOOH), magnetite (Fe
3O
4), and maghemite (
α-Fe
2O
3)) with a shell-like, dense layer near the top of the scales. High concentrations of readily soluble Fe(II) content was present inside the scales. Iron release from these corroded pipes was investigated for both flow and stagnant water conditions. Our studies confirmed that iron was released to bulk water primarily in the ferrous form. When DO was present in water, higher amounts of iron release was observed during stagnation in comparison to flowing water conditions. Additionally, it was found that increasing the DO concentration in water during stagnation reduced the amount of iron release. Our studies substantiate that increasing the concentration of oxidants in water and maintaining flowing conditions can reduce the amount of iron release from corroded iron pipes. Based on our studies, it is proposed that iron is released from corroded iron pipes by dissolution of corrosion scales, and that the microstructure and composition of corrosion scales are important parameters that can influence the amount of iron released from such systems.
The high-temperature oxidation of ZrB2 and the effect of SiC in controlling the oxidation of ZrB2 in ZrB2-SiC composites were studied in situ, in air, using XRD. Oxidation was studied by ...quantitatively analysing the crystalline phase changes in the samples, both non-isothermally, as a function of temperature, up to about 1650 C, and isothermally, as a function of time, at about 1300 C. During the non-isothermal studies, the formation and transformation of intermediate crystalline phases of ZrO2 were also observed. The change in SiC content, during isothermal oxidation studies of ZrB2-SiC composites, was similar in the examined temperature range, regardless of sample microstructure and composition. A higher SiC content retarded the oxidation rate of the ZrB2 phase in the composites. A novel approach to quantify the extent of oxidation by estimating the thickness of the oxidation layer formed during oxidation of ZrB2 and ZrB2-SiC composites, based on fractional conversion of ZrB2 to ZrO2 in situ, is presented.
A broadband printed microstrip antenna having cross polarization level >; 15 dB with improved gain in the entire frequency band is presented. Principle of stacking is implemented on a strip loaded ...slotted broadband patch antenna for enhancing the gain without affecting the broadband impedance matching characteristics and offsetting the position of the upper patch excites a lower resonance which enhances the bandwidth further. The antenna has a dimension of 42 × 55 × 4.8 mm 3 when printed on a substrate of dielectric constant 4.2 and has a 2:1 VSWR bandwidth of 34.9%. The antenna exhibits a peak gain of 8.07 dBi and a good front to back ratio better than 12 dB is observed throughout the entire operating band. Simulated and experimental reflection characteristics of the antenna with and without stacking along with offset variation studies, radiation patterns and gain of the final antenna are presented.
Fine ceramic oxide fibers are widely used as reinforcements in composites for high temperature applications. The primary goal of this research was to investigate the growth of single crystal or ...textured oxide fibers by heat treatment of polycrystalline or amorphous, extruded precursor fibers. Mullite was selected for this study due to its excellent chemical stability, creep resistance and strength at high temperatures. A quadrupole lamp furnace (QLF), with a small, disc-shaped, hot zone was used for the heat treatment.
Micrographic analysis and
in situ synchrotron X-ray diffraction analysis have been performed on the mullite system for anisotropic grain growth of mullite. The estimated activation energies from the SEM micrographic analysis were 644.3 and 773.7
kJ/mol for the length and thickness, respectively. An
in situ synchrotron X-ray diffraction microstructure analysis was done with a curved image plate (CIP) detector and the fiber was heat treated with a QLF. A Williamson–Hall analysis was carried out for the calculation of the apparent crystallite sizes. The apparent crystallite size showed anisotropy in crystallite growth. Furthermore, the growth rates in the 0
0
1 and 1
1
0 directions demonstrated elongated crystallite growth.
Mullite whiskers were prepared by HF leaching out and templated into polycrystalline mullite fiber by extrusion. Textured growth of mullite fiber with elongated grains, ∼400
μm in length and aligned along the long-axis of the fibers, was achieved by heat treatment. Repeated heat treatment cycles of a whisker-templated fiber showed a bamboo-like microstructure. It was confirmed by TEM that the growth direction along the fiber length was the 0
0
1 direction of orthorhombic mullite.
This paper was presented in part by V. L. Snoeyink as the Simon W. Freese Lecture at the 2002 Canadian Society of Civil Engineers/Environmental and Water Resources Institute of ASCE Environmental ...Engineering Conference in Niagara Falls, Ontario, Canada, July 22, 2002. The interactions of corroded iron pipe surfaces with water are of importance because they can lead to serious water quality degradation and material deterioration. A conceptual model has been developed in this paper to describe the formation and growth of iron scales, and their reactions that lead to colored water problems. Most corrosion scales have characteristic structural features, such as a loosely held top surface layer, a shell-like layer(s), and a porous core. According to this model corrosion scales are expected to grow from inside the scale via the corrosion reaction, i.e., the conversion of iron metal to ferrous ion. The average oxidation state of iron increases with distance from the pipe wall. The scale structure and scale reactions permit the ferrous iron to be released to the bulk water, where it undergoes conversion to particulate ferric iron, which is the cause of colored water. Scale structure and composition play important roles in the reactions of iron scales that lead to iron release, and water quality control to decrease the porosity of the scale is an important means of reducing iron release. It is anticipated that the conceptual model presented here will be used as a basis for changing water quality to minimize colored water formation, and as a guide for further research.
This paper presents a technique of using magnetic metamaterial as a broadband non-resonant artificial high dielectric substrate for achieving enhanced radiation performance in the microwave region. ...The selected metamaterial (MTM) is the basic single split-ring resonator (SRR) printed on a bare dielectric substrate of permittivity 3.8. When it is electrically excited by a plane wave, a high permittivity of 25 for the frequency range of 0.5–3.1 GHz is achieved. The application of the artificially made high dielectric substrate is validated with a 1.3 dBi gain enhancement of a broadband slot antenna with a single finite transmitter array of 5 × 4 high dielectric metamaterial substrate. The MTM-antenna composite is having an overall size of 60 × 48 × 21.6 mm3 when printed on a substrate of dielectric constant 3.8 and height 1.6 mm. The detailed study of MTM unit cell and the effect of MTM on antenna performance is thoroughly studied in simulation and validated with free space measurements.
A Broadband L -Strip Fed Printed Microstrip Antenna Sarin, V P; Nishamol, M S; Tony, D ...
IEEE transactions on antennas and propagation,
2011-Jan., 2011, 2011-01-00, Letnik:
59, Številka:
1
Journal Article
Recenzirano
A broadband <;i>;L<;/i>; -strip fed printed microstrip antenna is presented. The strip loaded slotted broadband microstrip antenna is fed by an L -strip feed line to achieve impedance matching for ...the higher order modes of the patch antenna in addition to the existing resonances. The antenna offers 74% bandwidth when printed on a substrate of dielectric constant 4.2 and has an overall dimension of 42 × 55 × 3.2 mm 3 . The simulated and experimental reflection characteristics of the antenna with and without the L -feed along with radiation patterns, input impedance variations, gain and efficiency of the final antenna are presented and discussed. The time domain transient analysis indicates a minimum dispersion to the transmitted pulse.
Almost 100 genetic loci are known to affect serum cholesterol and triglyceride levels. For many of these loci, the biological function and causal variants remain unknown. We performed an association ...analysis of the reported 95 lipid loci against 216 metabolite measures, including 95 measurements on lipids and lipoprotein subclasses, obtained via serum nuclear magnetic resonance metabolomics and four enzymatic lipid traits in 8330 individuals from Finland. The genetic variation in the loci was investigated using a dense set of 440 807 directly genotyped and imputed variants around the previously identified lead single nucleotide polymorphisms (SNPs). For 30 of the 95 loci, we identified new metabolic or genetic associations (P < 5 × 10(-8)). In the majority of the loci, the strongest association was to a more specific metabolite measure than the enzymatic lipids. In four loci, the smallest high-density lipoprotein measures showed effects opposite to the larger ones, and 14 loci had associations beyond the individual lipoprotein measures. In 27 loci, we identified SNPs with a stronger association than the previously reported markers and 12 loci harboured multiple, statistically independent variants. Our data show considerable diversity in association patterns between the loci originally identified through associations with enzymatic lipid measures and reveal association profiles of far greater detail than from routine clinical lipid measures. Additionally, a dense marker set and a homogeneous population allow for detailed characterization of the genetic association signals to a resolution exceeding that achieved so far. Further understanding of the rich variability in genetic effects on metabolites provides insights into the biological processes modifying lipid levels.
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