Home About us Contact
|
Home About us Contact | ||
|
|
||
Oxide Content (oxide + content)
Selected AbstractsFactors influencing the sorption of oxytetracycline to soilsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2005Aaryn D. Jones Abstract Veterinary antibiotics such as oxytetracycline (OTC) increasingly are found in the environment and often come into direct contact with soils via the release of animal wastes. Oxytetracycline is known to sorb strongly to soils by interaction with soil organic matter, clay minerals, and metal oxides. However, current knowledge of the influence of soil properties on OTC sorption is limited, as is our ability to predict OTC sorption to soils. This work was aimed at identifying properties that most influence the extent of OTC sorption in a suite of soils from the eastern United States representing a wide range in soil properties. Thirty soils were well characterized, an OTC soil-water distribution coefficient (Kd) was determined for each soil, and statistical analyses were employed to determine appropriate soil descriptors of OTC sorption. Soil texture, cation exchange capacity, and iron oxide content seemed to most influence the extent of OTC sorption in soils with organic carbon (OC) content between 0 and 4%. Thus, the knowledge of these three soil properties would be key to anticipating the extent of OTC sorption and gaining insight into OTC fate within a given soil system. Notably, OC content appeared to influence OTC sorption only in a soil with 9% OC. [source] The Effect of Compaction Method on the Expansion and Stability of Aluminium Foams,ADVANCED ENGINEERING MATERIALS, Issue 9 2006S. Asavavisithchai Abstract The foam expansion and collapse behaviour for heat treated Al-TiH2 precursors has been shown to be driven by the oxidation of the Al powder, which can, in moderation, improve the foam expansion and increase foam stability, and the premature loss of gas from the TiH2, which delays but decreases the foam expansion. The evidence presented indicates that as long as theoretical precursor densities >,99,% can be achieved, simultaneous heating and compaction are not required to achieve the best foaming behaviour. Instead, the oxygen or oxide content in the powder is critical and if the oxygen content in the atomised powder is in the range 0.3,0.4,wt.%, cold compaction is sufficient to produce foams which show expansions at least as good as those for precursors made by high cost hot working processes. [source] Simultaneous analyses and applications of multiple fluorobenzoate and halide tracers in hydrologic studiesHYDROLOGICAL PROCESSES, Issue 14 2005Qinhong Hu Abstract An analytical method that employs ion chromatography has been developed to exploit the use of fluorobenzoic acids (FBAs) and halides more fully as hydrologic tracers. In a single run, this reliable, sensitive, and robust method can simultaneously separate and quantify halides (fluoride, chloride, bromide, and iodide) and up to seven FBAs from other common groundwater constituents (e.g. nitrate and sulphate). The usefulness of this analytical method is demonstrated in both field and laboratory tracer experiments. The field study examines the hydrologic response of fractures and the matrix to different flow rates and the contribution of matrix diffusion in chemical transport. Laboratory tracer experiments with eight geologic media from across the USA,mostly from Department of Energy facilities where groundwater contamination is prevalent and where subsurface characterization employing tracers has been ongoing or is in need,reveal several insights about tracer transport behaviour: (1) bromide and FBAs are not always transported conservatively; (2) the delayed transport of these anionic tracers is likely related to geologic media characteristics, such as organic matter, pH, iron oxide content, and clay mineralogy; (3) use of iodine as a hydrologic tracer should take into account the different sorption behaviours of iodide and iodate and the possible conversion of iodine's initial chemical form; (4) the transport behaviour of potential FBA and halide tracers under relevant geochemical conditions should be evaluated before beginning ambitious, large-scale field tracer experiments. Copyright © 2005 John Wiley & Sons, Ltd. [source] Analysis of the possibility of the relationship between various implant-related measures: an 18-month follow-up studyJOURNAL OF ORAL REHABILITATION, Issue 2 2008T. F. TÖZÜM Summary, Better clarification of the long-term relationship among the various implant-related measures could improve the evaluation process for dental implants. Thus, the aim of the present study was to determine the potential correlations among the volumetric features and nitric oxide content of peri-implant sulcus fluid (PISF) and measures of implant stability, and the marginal bone loss. Completely edentulous patients (n = 15) treated with dental implants and ball attachment mandibular over dentures were included. Resonance frequency analysis (RFA), marginal bone level measurements, PISF volume and spectrophotometrically determined nitrite levels were recorded for all dental implant sites. Measures for early (n = 16) and delayed (n = 14) loaded dental implants were comparatively analysed for a period of 18 months. Some random correlations between PISF volume and marginal bone level, PISF nitrite level and marginal bone level and PISF volume and PISF nitrite content, and RFA and PISF volume were observed. However, the only constant correlation was noticed between implant stability (RFA scores) and marginal bone level. This correlation was negative and significant for all dental implants and for delayed loaded implants (P < 0·05). The pattern of loading seemed to affect the extent, but not the pattern of this relationship. While some of the implant-related measures may be strongly associated (e.g. dental implant stability and marginal bone level), not all measures from a single implant site are likely to be related. Such associations may be under the influence of a variety of factors including the loading protocol of dental implants. [source] A Limited Review of Water Diffusivity and Solubility in Glasses and MeltsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2008James E. Shelby A limited review of the literature dealing with water solubility and diffusion in oxide glasses and melts is presented, with an emphasis on simple and commercial compositions and on work during the past decade. Several methods for determination of water solubilities and diffusivities are discussed. Experimental results are presented for silicate, borate, and germanate glasses and melts. Water diffusivities always increase with increasing temperature and modifier oxide content in these melts. Variations in water solubility and diffusivity with alkali and alkaline earth identity for otherwise identical compositions are small, while variations with the identity of the glass-forming oxide are large. Water solubility increases with increasing modifier oxide content in alkali silicate melts, but decreases with increasing modifier oxide content in alkali borate and germanate melts. [source] Surface activity,thermodynamic properties and light scattering studies for some novel aliphatic polyester surfactantsPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 5 2004R. A. El-Ghazawy Abstract The preparation of 12 new polyester surfactants based on aliphatic amines and different ethylene oxide content is described. These surfactants were characterized by determining their molecular weights and polydispersity by gel permeation chromatography (GPC) and nitrogen content. Drop volume tensiometry (DVT) was used to measure the surface tension at 25, 35, 45 and 55°C. The surface tension isotherms were used to determine critical micelle concentration (CMC), maximum Gibb's adsorption (,max), minimum area per molecule (Amin), the effectiveness of surface tension reduction (,cmc) and the efficiency (pC20). The thermodynamic parameters of micellization (,Gmic, ,Hmic, ,Smic) and of adsorption (,Gad, ,Had, ,Sad) were calculated and the data showed that these surfactants favor micellization to adsorption. The static scattered light intensity measurements provide the calculation of the molecular weight of micelle and the aggregation number (N°), while the dynamic light scattering provide the hydrodynamic radius of micelle (RH) and the diffusion coefficient at different surfactant concentrations. The hydrodynamic radius of micelle (RH) at different surfactant concentrations could be used also to determine the CMC giving results that are comparable to those obtained by surface tension measurements. All the data are discussed regarding the chemical structure of the polymeric surfactants. Copyright © 2004 John Wiley & Sons, Ltd. [source] Application of magnetic and spectrometry methods in the detection of human activity in soils: a case study at the archaeological site of Kitros (Northern Greece)ARCHAEOLOGICAL PROSPECTION, Issue 3 2001E. V. Aidona Abstract In the present study the archaeological site of (Louloudies,Kitros) (northern Greece) is investigated by the use of magnetic and spectrometry geophysical methods. Soil samples were collected from several trenches within the archaeological site, as well as from radial traverses around kilns, which were used for glass production. Moreover, samples were collected from a long traverse, starting from the middle of the archaeological site and extending outside the site, in order to identify the limits of the settlement. Measurements were successful in identifying the different occupation levels and the boundaries of the archaeological site. High values of magnetic susceptibility and iron oxide content correlated well with the periods of intense human activity. Around the kilns, the mean values of the magnetic susceptibility indicated the effect of the fire mechanism in the surrounding area and gave some first evidence concerning the use of the kilns. Comparison of the magnetic and chemical properties of the anthropogenic soils suggests that their enhancement may be used as an index for locating areas and features of archaeological interest. Additionally, archaeomagnetic data have been obtained from a pottery and a glass kiln of the site. The magnetic directions (D = 355°, I = 62°, a95 = 3.6 and D = 356°, I = 51°, a95 = 2.3) were correlated to the reference curves compiled for Bulgaria and showed a satisfactory consistency for the declination, but the inclination values of the recorded magnetic field were divergent by about 10°. Copyright © 2001 John Wiley & Sons, Ltd. [source] l -Arginine Inhibits Isoproterenol-Induced Cardiac Hypertrophy through Nitric Oxide and Polyamine PathwaysBASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 2 2008Yan Lin Nitric oxide exhibits antihypertrophic functions and inhibits cardiac remodelling. However, the metabolism of polyamines and the potential interactions with nitric oxide in cardiac hypertrophy remain unclear. We randomly divided Wistar rats into four treatment groups: controls, isoproterenol (ISO), ISO and l -arginine, and l -arginine. Isoproterenol (5 mg/kg/day, subcutaneously) and/or l -arginine (800 mg/kg/day, intraperitoneally) was administered once daily for 7 days. The expression of atrial natriuretic peptide mRNA was determined by reverse transcription,polymerase chain reaction, and fibrogenesis of heart was assessed by Van Gieson staining. Polyamines were measured with high-performance liquid chromatography, and plasma nitric oxide content and lactate dehydrogenase (LDH) activity were determined with a spectrophotometer. The expression levels of ornithine decarboxylase, spermidine/spermine N1-acetyltransferase (SSAT), endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) were analysed by Western blot. Heart-to-body weight ratio, left ventricle-to-body weight ratio, atrial natriuretic peptide mRNA expression, collagen fibres and LDH activity were elevated, both ornithine decarboxylase and SSAT proteins were up-regulated, and total polyamines were increased in the group treated with ISO. Additionally, the expression of iNOS was up-regulated, eNOS was down-regulated, and nitric oxide levels were low. Notably, cotreatment with l -arginine reversed most of these changes except for SSAT expression, which was further up-regulated. We propose that increased polyamines and decreased nitric oxide are involved in cardiac hypertrophy induced by ISO and suggest that l -arginine pre-treatment can attenuate cardiac hypertrophy through the regulation of key enzymes of the polyamine and nitric oxide pathways. [source] Concentration of Wax-like Alcohol Ethoxylates with Supercritical PropaneCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 6 2007C. E. Schwarz Abstract The virtual insolubility of synthetic wax can be improved by ethoxylating the wax with a polyethylene glycol segment to form an alcohol ethoxylate. Current methods lead to a wide ethylene oxide distribution. This work shows that supercritical propane can fractionate alcohol ethoxylates according to the ethylene oxide content. Solubility measurements in propane at 408,K show total solubility of an alcohol mixture (average 40 carbon atoms) below 140,bar and a region of immiscibility between 0.975 and 0.5 at pressures below 275,bar for the alcohol ethoxylate mixture (average 40 carbon atoms, 50,% ethoxylation). This large solubility difference shows that fractionation of the alcohol ethoxylate with propane is possible. Countercurrent pilot plant runs proved that separation is possible and with energy integration and selection of the correct decompression process the technology is both technically and economically viable. [source] THE TECHNOLOGY OF PRODUCTION OF SASANIAN GLAZED POTTERY FROM VEH ARDA,?R (CENTRAL IRAQ)ARCHAEOMETRY, Issue 4 2008M. PACE Scanning electron microscopy coupled with an energy dispersive X-ray detector (SEM-EDS) has been used to study samples of Sasanian glazed pottery. Analysis of ceramic bodies revealed a general homogeneity in composition among the studied samples and the use of calcareous clay for their manufacture. Glazes are typically alkaline in composition, with sodium and potassium oxide contents between 8 and 13%, and between 3 and 5%, respectively; calcium and magnesium oxide contents are between 7 and 10%, and between 3 and 5%, respectively. These data suggest the use of plant ash together with a silica source for glaze production. Coating thickness is highly variable among different samples, from some 400 up to 1200 µm, but it is generally uniform when a single sample is concerned. Glazes are mostly coloured blue or blue-green; copper and iron are the colouring agents detected; abundance of bubbles, silicate crystals and relics of unmelted material are responsible for their generally opaque appearance, together with the presence of weathering products. The characteristics of the body to glaze contact zone, together with the widespread presence of bubbles, would not rule out production by a single firing process. A few samples feature a peculiar gritty coating on one side of their surface; SEM images show that they are actually partially vitrified, and EDS data denote a rather heterogeneous composition. It seems possible that they result from mixing clay together with the frit used for glaze development. [source] ICP,MS ANALYSIS OF GLASS FRAGMENTS OF PARTHIAN AND SASANIAN EPOCH FROM SELEUCIA AND VEH ARDA,?R (CENTRAL IRAQ)*ARCHAEOMETRY, Issue 3 2008P. MIRTI Forty-one glass fragments were analysed by inductively coupled plasma , mass spectrometry, determining 40 major, minor and trace elements, including rare earth elements. The fragments came from excavations carried out at the archaeological sites of Seleucia and Veh Arda,?r in modern Iraq, and were dated to the Parthian and Sasanian epochs. Analytical data indicate that all the samples are silica,soda,lime glasses. Magnesium and potassium oxide contents below 1% suggest that eight out of nine glasses from Seleucia, dating from between the first and the third century ad, could have been obtained by use of an evaporite as a flux; the same conclusion can be drawn for some of the Sasanian glasses dating from the fourth and fifth centuries ad. The other glasses from Veh Arda,?r, as well as the remaining sample from Seleucia, are characterized by higher contents of magnesium and potassium, which suggests recourse to plant ash; different magnesium and phosphorus contents allow one to separate these samples into two main groups, pointing to the use of different kinds of plant ash. Aluminium and calcium contents, together with trace element data, may indicate that different sands were used for preparing glasses of different composition. Samples from Seleucia and Veh Arda,?r are mainly blue,green and green to yellow,green, respectively; iron and manganese contents suggest that the furnace atmosphere was mainly responsible for the development of these hues. [source] Total and soluble fluorine concentrations in relation to properties of soils in New ZealandEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2006P. Loganathan Summary Soil fluorine (F) concentrations continue to increase in agricultural soils receiving regular applications of phosphatic fertilizer. Continued accumulation of soil F poses a risk to grazing ruminants and may pose a future risk to groundwater quality. This paper examines the range of total F (Ft) concentrations and forms of soluble F species and their relationship to selected soil properties in New Zealand agricultural soils. The Ft and soluble F (soil F extracted with water (Fwater) and 0.01 m KCl (FKCl)) concentrations in 27 soil samples (0,75 mm depth) taken from predominantly pasture sites in the North and South Islands of New Zealand were much less than those reported in the literature for sites contaminated with F from industry. The Ft concentrations ranged from 212 to 617 µg F g,1 soil. The F-toxicity risk to grazing animals in farms at these sites through soil ingestion is small at present, but farms with very large Ft concentrations (i.e. > 500 µg F g,1) need to adopt suitable grazing and fertilizer management practices to avoid future F-toxicity risk. The Ft concentration had very strong positive correlations with both total soil P and total soil Cd concentrations, reflecting the link between P fertilizer use and F accumulation in the soils. It also had significant positive correlations with organic matter and amorphous Al oxides contents, indicating that F is strongly bound to Al polymers adsorbed to organic matter and amorphous Al oxides. The Fwater and FKCl concentrations and free F, ion concentrations in water (F,water) and 0.01 m KCl (F,KCl) extracts were generally two and three orders of magnitude, respectively, less than the Ft concentrations and were much less than the concentrations considered phytotoxic. The Fwater and FKCl concentrations were positively related to soil organic matter content and negatively related to soil pH. Regression models relating Fwater and FKCl concentrations to soil organic matter content and soil pH suggest that F can be very soluble in extremely acidic soils (pH(water) < 4.9) with large organic matter contents and therefore F potentially may contaminate groundwater if these soils are also coarse-textured and the water table is shallow. [source] | ||||||||||||||||