Concentration Ratio Of Cr Research Articles

Enhanced Cr (VI) removal with Pb (II) presence by Fe2+-activated persulfate and zero-valent iron system

ABSTRACT Combined heavy metals such as chromium (Cr (VI)) and lead (Pb (II)) in natural water have globally posed severe environmental and public health risk. Here the removal of Cr (VI) and Pb (II) mixed pollutants using Fe2+-activated persulfate (PS) with extra zero-valent iron (ZVI), which was not only a supplementary Fe2+ source, but also a high-efficiency absorbent, was investigated. During removal, pivotal factors of initial pollutant concentration, dosages of ZVI and PS, initial pH and temperatures were examined. Interestingly, generating a lot of H+ in the process of Fe (II) activating persulfate were helpful to the corrosion of ZVI over a large range of pH (1–9). Under the optimum condition, removal efficiency of Pb (II) and Cr (VI) have reached 100% and 94.26% respectively. The removal mechanism was suggested as a three-step reaction that the Pb (II) boosted the removal of Cr (VI) by co-precipitated in wastewater, and the Pb (II) and Cr (VI) were adsorbed and subsequently reduced to Pb0 and Cr3+ as Cr(OH)3 or Cr3+-Fe3+ hydroxides on ZVI surface. Cr (VI) and Pb (II) adsorption kinetics agreed with the pseudo-second-order reaction rate expression. In addition, we were surprised to found that the contribution effect of chromium and lead co-precipitation for their removal by Fe (II) – PS-ZVI has strong dependence on initial pH and concentration ratio of Cr (VI) and Pb (II). The result indicated that Fe (II)-PS-ZVI system should be a favourable removal technology for Cr (VI) and Pb (II).

Polypyrrole/reduced graphene oxide aerogel particle electrodes for high-efficiency electro-catalytic synergistic removal of Cr(VI) and bisphenol A

In this paper, synthesis of polypyrrole/reduced graphene oxide aerogel (PGAs) as particle electrodes and their application in three-dimensional electrode system for simultaneous reduction of hexavalent chromium (Cr(VI)) and oxidation of bisphenol A (BPA) were implemented firstly. Electro-catalytic properties were investigated systemically in terms of the influences of pivotal factors, such as pH, the concentration ratio of Cr(VI) and BPA, voltage and the ratio of PGAs mass to solution volume (S/L). The results showed superb removal rates of 98.52 ± 1.48% for Cr(VI) and 98.00 ± 1.17% for BPA within 30 min under the optimal conditions. Furthermore, synergy of both pollutants was testified by the comparison of removal rates in electro-catalytic kinetics and their fitting in mixed solution with kobs-Cr(VI) = 0.2019 min−1, kobs-BPA = 0.1463 min−1 significantly higher than that in one-component aqueous solution (kobs-Cr(VI) = 0.0397 min−1, kobs-BPA = 0.0417 min−1). After 20 cycles of experiments, there were still high contaminants and total organic carbon (TOC) removal rates, which showed excellent reutilized ability of PGAs. More deeply, final destination of Cr(VI) was analyzed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscope-energy dispersive X-ray spectroscopy (SEM−EDX). Meanwhile, intermediates of BPA oxidized with the aid of Cr(VI) and OH were analyzed and a possible degradation pathway was proposed. Importantly, Cr(VI)/BPA system provided a remarkable example of a “waste control by waste” strategy for the synergetic removal.

The effect of the nickel and chromium concentration ratio on the temperature coefficient of the resistance of a Ni–Cr thin film-based temperature sensor

Wearable devices have become one of the most promising modern technologies due to the rapid development of network and sensor systems. Moreover, flexible sensors were researched to be applied in wearable devices. In this paper, we show a low cost and flexible temperature sensor that has high responsivity to temperature. A cylindrical PET monofilament was used as a main substrate and a Ni–Cr thin film was deposited by RF magnetron co-sputtering without a pattern. Various Ni–Cr concentration ratios were applied in this paper by altering the sputtering power of the Cr target. Increasing the concentration of Cr resulted in the variation of several characteristics such as the thickness of the Ni–Cr thin film, crystallinity, and the surface state. In addition, depositing the Ni–Cr thin film on a PET monofilament meant that the device showed resistive behavior when the temperature increased. This was proven by measuring the Temperature Coefficient of Resistance (TCR). The TCR was also measured after both repetitive bending and washing to evaluate its suitability in wearable devices. Overall, TCR showed diverse features for different Ni–Cr concentration ratios with a maximum value of 30×10−3°C−1.

Simultaneous Photocatalytic Reduction of Cr(Ⅵ) and Oxidation of SSA by Carbon Nitride

Carbon nitride is a novel nonmetal semiconductor photocatalyst, which has developed into an ideal environmental treatment material in recent years. Graphite carbon nitride(g-C3N4) was prepared through pyrolysis melamine, and the structure, morphology and optical properties of samples were characterized by X-ray diffraction(XRD), transmission electron microscopy(TEM) and UV-Vis diffuse reflectance spectra(UV-Vis DRS). The potential application of g-C3N4 in the simultaneous photocatalysis reduction of Cr(Ⅵ) and oxidation of sulfosalicylic acid(SSA) was further explored. And the effects of different conditions such as catalyst dosage, pH and initial concentration ratio of Cr(Ⅵ) with SSA on the simultaneous photocatalysis were also investigated. The results showed that when the catalyst dosage was 0.5 g·L-1, pH=2, the initial concentration ratio of Cr (VI) and SSA was 1:4(10 mg·L-1:40 mg·L-1), optimal simultaneous photocatalysis efficiency was achieved, which was more than 3 times higher than that of the separated photoreduction or photooxidation reactions. Within 3 hours, the reduction ratio of Cr(Ⅵ) and oxidation ratio of SSA could reach 98.9% and 93.4%, respectively. The mechanism of simultaneous photocatalysis was discussed. Cr(Ⅵ) was reduced by electrons and SSA was oxidized by the combined function of hole, O2·- and·OH under visible light.

Annealing effect on the electrical properties and composition of a NiCrAl thin film resistor

The composition of NiCrAl thin film resistors, under different annealing conditions in a N2 atmosphere, was investigated. The Auger electron spectrum (AES) has been used in studying the composition of NiCrAl thin films. The concentration ratio of Cr to Ni decreases when the annealing temperature increases. The electrical properties of a NiCrAl thin film resistor are affected by the concentrations of Cr and Ni, which lead to a higher temperature coefficient of resistance (TCR) and a lower sheet resistivity. The TCR of a NiCrAl thin film resistor is −5 ppm/°C at a 250 °C annealing temperature.

The combined effects of Cu and Ag on the nanostructure and mechanical properties of CrCuAgN PVD coatings

Abstract In order to study the combined effects of the noble, low miscibility metals, Cu and Ag, on the nanostructure and mechanical properties of nitrogen-containing Cr coatings, CrCuAgN coatings were prepared using unbalanced magnetron sputtering. An optimised semi-orthogonal closed-field target configuration was used to obtain coatings with similar thicknesses and distributed Cu + Ag concentrations across different stainless steel sample positions in the deposition chamber. The coating cross-sections and surface morphologies were investigated using Scanning Electron Microscopy (SEM), and the chemical compositions were analysed using Energy Dispersive X-ray (EDX) spectrometry. Phase compositions were analysed using X-Ray Diffraction (XRD), and the hardness and elastic modulus were measured using nanoindentation. The (Cu + Ag)/Cr concentration ratios of coatings were found to be strongly correlated to deposition rate (and thus coating thickness). In the nitrogen-free control group, coatings showed strong preferential orientation for both metallic Cr and Ag, with the orientations changing depending on the sample position relative to the sputter target. The introduction of nitrogen resulted in the formation of coatings showing a high-degree of solubility of Cu in metallic Cr and Cr 2 N nitride, or even an amorphous phase containing all four elements. A coating with moderately high hardness of 14.1 GPa and H/E ratio of 0.072, with combined Cu + Ag concentration approaching 15 at.% was obtained, which could be promising in prolonging the lifetime of solid-lubrication tribological coatings.

Development, validation and clinical evaluation of a dried urine spot method for determination of hippuric acid and creatinine

ObjectivesThe purpose of this study was to develop and validate a HPLC–DAD method for determination of creatinine and hippuric acid in dried urine spots (DUS), evaluating its clinical applicability. Design and methodsSample preparation was based on a simple one step extraction with water. Analysis was performed in a reversed phase column Hypersil Gold® C18 (150×4.6mm, 3μm) with isocratic elution. Mobile phase was a mixture of triethylammonium phosphate buffer 5mM, pH3.3 and acetonitrile (90:10, v/v). ResultsTotal analytical run time was 6min. Precision assays presented CV% lower than 11.8%. Accuracy was 96.0–103%. The lower limit of quantitation was 50mgL−1. Mean extraction yields were 99% for CR and 79.3% for HA. Analytes were stable in DUS up to 11days at 40°C. The method was tested in 49 paired DUS and urine samples, with acceptable agreement. HA–CR concentration ratios in DUS were in the range of 0.06 to 2.74, being in average 100.7% from those values found in urine. ConclusionsDUS samples are a useful alternative for biological monitoring of toluene occupational exposure, especially in Developing Countries where sample logistics could be an important concern.

TÜRKİYE ELEKTRİK ENERJİSİ PİYASASINDA HERFINDAHL-HIRSCHMAN VE CRm ENDEKSLERİ İLE YOĞUNLAŞMA ANALİZİ

In this study, the structure of Turkish electricity market is analyzed comparatively through CR Concentration Ratio (CR4 and CR8) and Herfindahl-Hirschman Index computed with sales from production of the firms in Turkish electricity market between 1993-2011. As a result of the analysis, the structure of the market is said to be highly concentrated in CR4 and Herfindahl-Hirschman Index. According to both methods, the structure of the market is close to monopoly thus far from being competitive.

Transfer of natural radionuclides from soil to plants in tropical forest (Western Ghats - India).

Soil and 2 wild plant species (Evodia roxburghiana and Eleaocarpus oblangus)have been collected from the western Ghats region and analysed for 210Po and238U. The radioactivity concentrations in plants and soil reflect the impact of the existence of igneous nature of rock in the area of study. Concentration ratios (CR) of these radionuclides, between plants and underlying soil, have been studied and the results shows that the concentration ratios (CR) seem to be depend on radionuclides in soil. Key words: Primordial radionuclides, western Ghats, monazite, igneous rock, CR-concentration ratio.

Effects of Al target power on the mechanical and oxidation resistance of the CrN/AlN multilayer coatings

Synthesis of CrN/AlN superlattice coatings with various composition (Cr/Al at.%) and superlattice period using closed-field unbalanced magnetron sputtering method was studied in this work. The coatings were characterized in terms of crystal phase, chemical composition, microstructure, microhardness using scanning electron microscopy (SEM), X-ray diffraction (XRD), cross-section TEM, glow discharge optical emission spectroscopy (GDOES) and nano-indentation hardness test. In addition an isothermal oxidation test at 900 °C was performed using a TGA for up to 20 h in air to evaluate the oxidation resistance of these films. Results from TEM and XRD analysis showed that the crystal structure of AlN layer in the CrN/AlN superlattice coatings has a metastable cubic lattice structure, matching coherently with the CrN layer. The maximum hardness approximately 34 GPa of the CrN/AlN superlattice film was observed when the atomic concentration ratio of Cr to Al is 0.51 and the superlattice period (λ) is 11 nm. This hardness values were 1.4 times higher than that of the CrN single layer coating. These enhancement effects in superlattice films could be attributed to the resistance to dislocation glide across interfaces between the CrN and AlN layers. Isothermal oxidation tests using a TGA showed that the CrN/AlN multilayer films have a superior oxidation resistance to that of CrN films due to the presence of alternating AlN thin films, This oxidation resistance of the thin film increased as the Al content in the film increases up to 12.3 at.% Al above which no further improvement of the oxidation resistance was observed.

Magnetic resonance spectroscopy in a patient with Kleine-Levin syndrome

Sirs: Kleine-Levin syndrome (KLS) is a rare recurrent hypersomnia associated with behavioural, cognitive, eating and sexual disturbances [1, 2]. A recent SPECT study in 7 patients with (KLS) showed decreased thalamic perfusion during the hypersomnolent attacks [3]. These findings were later confirmed in a case report by Hong et al. [4]. Proton magnetic resonance spectroscopy (1H MRS) is a noninvasive method of obtaining metabolic information. By means of MRS, different compounds can be measured including N-acetylaspartate (NAA), a marker of neuronal integrity and glutamate-glutamine (Glu-Gln), which plays an important role in excitatory neurotransmission and mitochondrial metabolism [5]. We present a 19-year-old patient with idiopathic, classical KLS. Over a 4-year period he suffered 19 stereotypical hypersomnolent episodes. The attacks were always preceded or accompanied by fever up to 39 °C, sore throat or stomach pain. At the beginning of the episodes mood depression was observed, the patient was melancholic, sad and withdrew socially. Sleep behaviour reached 20 hours/day, interrupted by compulsive eating, 7–8/days without any specific food preference resulting in a weight gain of approximately 5 kg/attack. Sexual disinhibition with masturbation, irritability, aggressiveness, cognitive and concentration disturbances were frequent. The attacks usually ended with insomnia lasting 2–3 days and a subsequent gradual improvement of emotional state and cognition. The patient described this phase as awakening from a dream and had difficulty recalling the events that had occurred during the attack. In the first year before treatment 12 attacks were observed. Under therapy with lithium 30 mg/day and valproic acid 2000 mg/day a remarkable reduction in frequency and severity of the episodes (7 attacks over a period of 2.5 years) was noted. The duration of the hypersomnolent episodes remained unchanged, 10 days on average. Hypocretin-1 in the cerebrospinal fluid during an attack was in the normal range, 530 pg/ ml. The patient underwent 1H MRS in an asymptomatic period and a month later during a typical episode. Because of presumed hypothalamic [6] or thalamic [3, 4] dysfunction in KLS we chose three regions of interest: hypothalamus and both thalami. MRS was performed on a Philips Achieva 3.0 T scanner. Single-voxel proton MR spectra, voxels of 17 x 14 x 15 mm in both thalami (3.57 cm3) and of 10 10 10 mm (1 cm3) in the hypothalamus, were acquired and processed to determine metabolite concentration ratios. A remarkable change between the two examinations was observed in the concentration ratios of NAA-NAAG, (total NAA)/Cr and Glu-Gln/Cr (Fig. 1). During the attack lower (total NAA)/Cr ratios in the right (–25.7 %) and left (–13.2 %) thalami were observed. In the hypothalamus the (total NAA)/Cr ratio was slightly higher in the second scan during the hypersomnolent attack. The Glu-Gln/Cr ratio was higher during the attack – in both the right (59.8 %) and left (52.3 %) thalamus. In hypothalamus a reliable value for Glu-Gln/Cr ratio was obtained only during the second scan and it was similar to the values in both thalami. Different values for intraindividual metabolite ratio, variability and reproducibility of the results are reported in the literature, depending on the technical parameters of the acquisition and on the region of interest. For example an intraindividual temporal cortical variation up to 12 % was observed for (total NAA)/Cr and up to 29 % for Glu-Gln/Cr on a 3T scanner [7]. The decrease in the (total NAA)/Cr concentration ratio in both thalami during the hypersomnolent episode in our patient exceeds the normal range of the intraindividual variability at 3T. Our finding supports the hypothesis of a thalamic dysfunction in KLS, recently suggested by other authors [3, 4]. This hypothesis is indirectly supported also by the observation of KLS-similar symptoms (reduced alertness, impaired sleep and behavioural changes) following paramedian thalamic strokes [8]. The observed high Glu-Gln/Cr concentration ratio in all regions of interest during the episode points to additional, global metabolic changes in the brain. Glutamate is a primary excitatory neurotransmitter. Decreased NAA/Cr and increased LETTER TO THE EDITORS

Synthesis of CrN/AlN superlattice coatings using closed-field unbalanced magnetron sputtering process

Synthesis of CrN/AlN superlattice coatings with various composition (Cr/Al at.%) and superlattice period (λ) using closed-field unbalanced magnetron sputtering method was studied in this work. The coatings were characterized in terms of crystal phase, chemical composition, microstructure and mechanical properties by transmission electron microscopy (TEM), X-ray diffractometry (XRD), glow discharge optical emission spectroscopy and nano-indentation test. Results from TEM and XRD analysis showed that the crystal structure of AlN layer in the CrN/AlN superlattice coatings has a metastable cubic lattice structure rather than an equilibrium hexagonal structure (wurtzite-type), matching coherently with the CrN layer, which has a NaCl type lattice structure. The maximum hardness and plastic deformation resistance (H3/E2) of CrN/AlN superlattice film, when the atomic concentration ratio of Cr to Al is 0.98 and the superlattice period (λ) is 4.8 nm, are approximately 37 and 0.48 GPa, respectively. These values are 1.6 and 2.5 times higher than those of the CrN single layer coating (23.5 and 0.17 GPa), respectively. These enhancement effects in superlattice films could be attributed to the resistance to dislocation glide across interface between the CrN and AlN layers.

Brain water diffusion in normal and creatine-supplemented rats during transient global ischemia.

Brain water diffusion in response to transient global ischemia (12 min), reperfusion (60 min), and cardiac arrest was monitored by localized proton magnetic resonance spectroscopy. The trace of the apparent diffusion coefficient tensor (ADC(Av)) was determined at high temporal resolution (10 sec) to assess the putative neuroprotective potential of oral creatine (Cr) in rats that received 2.2 g Cr-monohydrate per kg body weight per day for 10 days (n = 8) relative to controls (n = 9). Cr-fed rats revealed a statistically significant increase of the cerebral concentration ratio of Cr to choline-containing compounds (20%). The decrease of the ADC(Av) value during acute ischemia showed a three-phasic behavior in line with energy depletion, cytotoxic edema, and brain cooling. In Cr-fed rats, slightly less severe and mildly delayed diffusion changes during ischemia and similar beneficial trends during early reperfusion did not reach statistical significance. Magn Reson Med 42:798-802, 1999.

Brain water diffusion in normal and creatine‐supplemented rats during transient global ischemia

Brain water diffusion in response to transient global ischemia (12 min), reperfusion (60 min), and cardiac arrest was monitored by localized proton magnetic resonance spectroscopy. The trace of the apparent diffusion coefficient tensor (ADCAv) was determined at high temporal resolution (10 sec) to assess the putative neuroprotective potential of oral creatine (Cr) in rats that received 2.2 g Cr-monohydrate per kg body weight per day for 10 days (n = 8) relative to controls (n = 9). Cr-fed rats revealed a statistically significant increase of the cerebral concentration ratio of Cr to choline-containing compounds (20%). The decrease of the ADCAv value during acute ischemia showed a three-phasic behavior in line with energy depletion, cytotoxic edema, and brain cooling. In Cr-fed rats, slightly less severe and mildly delayed diffusion changes during ischemia and similar beneficial trends during early reperfusion did not reach statistical significance. Magn Reson Med 42:798–802, 1999. © 1999 Wiley-Liss, Inc.

Use of Oral Calcium Loading to Characterize the Hypercalciuria of Young Insulin-Dependent Diabetics*

To investigate the pathogenesis of the alterations in bone and mineral metabolism that are found in young insulin-dependent diabetics (IDDs), we performed a standard oral calcium load in 26 IDDs, 7-18 yr of age, and in 17 normal children, 9-18 yr of age. Eighty-five percent of the IDDs had second metacarpal cortical bone widths below the mean for matched controls. Calcium excretion in the IDDs fell along a continuous spectrum, ranging from normal to values consistent with renal hypercalciuria. Immunoreactive PTH was significantly (P less than 0.03) lower in the IDDs compared to that in the controls, and 24,25-dihydroxyvitamin D was significantly elevated (P less than 0.001). We were not able to document a significantly lower concentration of 1,25-dihydroxyvitamin D in the IDDs. Serum calcium, phosphate, and PRL levels were normal, as were creatinine (Cr) clearance and 24-hr urinary cortisol excretion. There was no apparent correlation between the fasting and postload urinary Ca to Cr and glucose to Cr concentration ratios. The accumulated data suggest that in many young IDDs, there is a component of intestinal calcium hyperabsorption which results in appropriate feedback responses by the parathyroid gland and vitamin D metabolic pathway(s). This imbalance between circulating PTH and vitamin D metabolites could result in defective bone remodeling and decreased cortical thickness.

Photoconductivity analysis of chromium and oxygen-related levels in semi-insulating GaAs

Semi-insulating GaAs doped with different amounts of Cr and oxygen has been characterized by extrinsic photocon-ductivity spectra at room temperature. The shape of the spectrum depends on the amount of Cr and oxygen dopant. It is interpreted by the two-level model which assumes the lattice relaxation effect at the Cr and oxygen-related levels. The height of the photoconductivity hump around 0.9 eV depends on the concentration ratio of Cr to oxygen; the larger the ratio is, the higher the hump is.