Low Levels Of Cr Research Articles

Prognostic Factors Determining Morbidity and Mortality in Organophosphate Poisoning.

Objective:Our aim in this retrospective study was to determine the factors affecting poor prognosis and mortality of organophosphate (OP) poisoning by reviewing patient data. We also reviewed present knowledge to make conclusions on certain longstanding debates in light of the literature.Methods:In this retrospective descriptive study, patients who were admitted to and hospitalized in the emergency department (ED) or intensive care unit (ICU) of a university hospital with the diagnosis of OP poisoning between December 2010 and December 2015 were evaluated. All the data were obtained from electronic and manual patient files. A total of 80 patients were included in the study.Results:The mean age of the study patients was 32.4±15.0 (13-94). Forty-nine (61.2%) patients were female. Twenty-two (27.5%) patients were seriously poisoned and needed mechanical ventilation (MV) support. Low pseudocholinesterase (PChE), high creatinine (Cr), low Glasgow Coma Scale (GCS) scores and long hospitalization durations were all found to be poor prognostics in MV patients. Low PChE and high Cr levels were found to be independent predictors of the hospitalization duration and high Cr was found to be an independent predictor of the intubation duration of MV patients in regression analyses. Ten (45.5%) of the MV patients were unresponsive to medical treatment and Therapeutic plasma exchange (TPE) was performed. Seven patients were discharged healthy. Three patients with low PChE levels and comorbidities died.Conclusions:Prolongation of respiratory depression necessitating MV support, comorbidities, long hospital stay, elevated creatinine, low GCS scores and low PcHE levels without regeneration in the first 48 hours of admission are all found to be poor prognostic factors for organophosphate (OP) poisoning.

Chromium Displacement in Subtropical Soils Fertilized with Hydrolysed Leather: A Laboratory Study.

Prolonged use of biosolids with high metal content may result in diffuse pollution across large regions, especially if such ions can move freely through the soil profile and reach underground water sources. The objective of this study was to verify whether Cr added to the soil surface in the form of hydrolysed leather or a soluble salt would migrate over significant distances in four subtropical soils differing in physical, chemical and mineralogical properties. Horizontal and vertical mobility were assessed in Petri dishes and small pots, respectively, using low (12mgkg-1 soil) and high Cr levels (150mgkg-1 soil) added to the soil surface. Irrespective of concentration, soluble Cr salts were found to move more easily in soils with low organic matter and clay content. Contrarily, Cr added as hydrolysed leather exhibited negligible mobility and tended to accumulate in the vicinity of application.

Automated Single-Phase Liquid-Liquid Extraction for Determination of Cr(VI) Using Graphite Furnace Atomic Absorption Spectrophotometry without Wet Digestion of Samples

This paper proposes a method to perform rapid and sensitive graphite furnace atomic absorption spectrometry (GFAAS) determination of Cr(VI) in vinegar samples without wet digestion. Taking into account low levels of Cr(VI) and the presence of several concomitants in the sample matrix, the proposed method uses single-phase liquid-liquid extraction (SPLLE). The method is automated, employing a flow-batch analyzer (FBA) which uses a mixing chamber designed to emulate a separation funnel promoting the formation/break of the single-phase solution, reaction and extraction. The Cr(VI) extraction procedure was performed by proportioned mixing of the vinegar sample (aqueous phase), amyl alcohol (organic phase), and ethanol (consolute) to form a single-phase solution. The chelating reagent sodium diethyldithiocarbamate (DDTC) dissolved in the consolute reacts rapidly with Cr(VI), in the single phase to produce a stable Cr-DDTC complex. The single-phase break step is performed by adding an excess of Britton-Robinson buffer, and then the organic phase enriched with Cr(VI) was analyzed by GFAAS. Factors such as extraction steps, single-phase composition, pH, chelating agent concentration, and flow-batch parameters were optimized. The FBA-SPLLE-GFAAS was evaluated in vinegar samples showing satisfactory analytical features in terms of limit of quantification (0.86 μg L −1 ), precision (RSD <12 %), characteristic mass (m0 = 0.32 pg), high sampling rate (26 h −1 ), and accuracy (recovery rate = 82–108 %). The proposed method requires one-step extraction and is eco-friendly since it consumes low amounts of non-toxic chemicals and generates little waste (about 700 μL per determination).

Does Response to Bortezomib-Based Therapies Correlate to Beta-2 Microglobulin in Multiple Myeloma?

Introduction. Multiple Myeloma (MM) is a heterogeneous, incurable disease. Several prognostic scores have been developed to estimate response to treatment, progression free survival (PFS) and overall survival (OS). The International Staging System defines 3 stages with distinct prognostic significance, using serum beta 2 microglobulin (b2M) and serum albumin. However, due to a higher power of risk discrimination, current guidelines recommend to stratify patients according to cytogenetics (CG) and treat high-risk patients with Bortezomib (BZ)-based therapies.In Uruguay, BZ is financed and regulated by a National Funding Board and is approved for high-risk MM or renal impairment at diagnosis or at relapse. As a consequence, the patients included in this study are a selected high risk MM subgroup.Even though proteasome inhibitors have improved outcomes for many high-risk MM patients, some still present short response duration and poor survival. Identifying simple factors that can predict response to BZ would be useful in order to better select the most appropriate therapeutic choice.Patients and Methods. We conducted a retrospective study to evaluate MM response to BZ-based therapy according to b2M, serum creatinin (Cr) and CG. Forty-seven MM patients [median age 59 years (38-77), females 25 (53%)] from two public centers treated with BZ-based combinations were included. According to local regulatory policies, only patients with renal failure and/or high risk CG features received BZ as first line therapy (n=31). Other 16 individuals received BZ combinations for relapsed/refractory disease. Patients received a median of 5 cycles of BZ (3-6). Nineteen individuals (40%) received high dose melphalan and autologous stem cell transplantation after BZ-based induction. At diagnosis, 28 (59%) had an ISS 3, 24 (51%) patients had serum Cr higher than 2 mg/dL and 14 (30%) exhibited high risk CG. Responses to BZ therapy were evaluated according with International Myeloma Working Group criteria as complete response (CR), very good partial response (VGPR), partial response (PR), stable disease (SD) and progressive disease (PD). Responses were analyzed depending on b2M level, serum Cr and CG. Comparison between groups was made by chi-square test. PFS and OS were calculated by the Kaplan-Meier method. Survival was compared between groups by log-rank test.Results. No differences in responses to BZ-based therapies were found when comparing patients with low (lower than 5,5 mg/L) versus high b2M levels (CR/VGPR 44,4 vs 44% respectively, p=0.97), low versus high serum Cr (CR/VGPR 34 vs 55% respectively, p=0.18) and standard versus high risk CG (CR/VGPR 46,7 vs 38,5% respectively, p=0.62). Patients with renal failure (serum Cr 2 mg/dL or higher at diagnosis, n=23) had a median of 53% (0 - 88%) reduction in Cr levels after receiving at least three cycles of BZ therapy. Eleven of them (47,8%) had normal renal function after completing BZ treatment. From 9 patients requiring dyalisis at diagnosis, 4 were out of dyalisis after BZ treatment. No significant differences in PFS and OS were observed when patients with low versus high b2M levels and standard versus high risk CG were compared. Patients with low Cr levels at diagnosis show a significantly better OS compared with those with Cr higher than 2 mg/dL (median OS not reached versus 42 months respectively, p=0.004), with no differences in PFS.Conclusion. In a selected high risk MM patients group treated with BZ-based therapies, similar response rates were obtained in individuals with high or low b2M levels, Cr levels, and standard or high risk CG. Although individuals with renal failure at diagnosis exhibit similar quality of responses than standard patients, long term OS of this group is still impaired and further improvements in therapy are needed.Note: GB and ER have contributed in equal parts to this work. DisclosuresNo relevant conflicts of interest to declare.

Hair elements and healthy aging: a cross-sectional study in Hainan Island, China.

Healthy aging is considered as the core issue of aging population. Centenarians are a symbol of healthy aging. Concentration of elements in hair is an indicator of micronutrient status, which can affect the human health. In the present study, we investigated element concentrations in the scalp hair of 255 healthy centenarians from Hainan Island, China. The pattern of intergenerational transmission of elements and the effects of confounders such as sex, age, education level, smoking habits, alcohol intake, and frequency of hospitalization on hair element concentrations were assessed. For most elements, the load in hair increased significantly through intergenerational transmission (i.e., centenarians<children<grandchildren). Our results also demonstrated that female centenarians had significantly higher concentrations of Ca, Mg, Mn, Se, and Sr but lower levels of Cr and P. The Mn level was statistically significantly lower in the primary studies group. Alcohol intake was positively associated with Cd and Na levels, whereas smoking habits showed no significant effect on all the elements. Furthermore, the frequency of hospitalization was significantly positively associated with Cd, Cu, and Pb concentration. Moreover, our analysis suggested that adequate concentrations of Fe and Se might increase the life span of centenarians, whereas excessive concentrations of P and Pb were harmful to health and reduced life span. These results imply that element concentrations could be manipulated as a therapeutic modality in geriatric disease. They might also provide reference values for diseased subjects, allowing improved diagnoses and more effective therapies, which might support effective policies on health and aging.

Comparing the Levels of Trace Elements in Patients With Diabetic Nephropathy and Healthy Individuals.

Background:Diabetic nephropathy is the most common cause of end stage renal disease (ESRD) in developed countries. Several trace elements were reported to be changed in diabetic nephropathy.Objectives:The aim of this study was to investigate changes in serum levels of zinc, copper and chromium and their association with the incidence of ESRD in patients with diabetes.Patients and Methods:This study was performed on 70 patients with type 2 diabetic nephropathy (macro and micro-albuminuria) and 70 healthy individuals. Samples were collected to survey metals by atomic absorption spectrophotometer. Data was analyzed by SPSS18 using descriptive and inferential analysis methods.Results:Mean ± SD levels of Zn, Cu and Cr were significantly decreased in blood samples of patients compared to healthy subjects (P < 0.01). Also the mean concentrations of Cu, Zn and Cr in drinking water of Sari were lower than the accepted limit. Only in one case, Cu was higher than the accepted limit, which was the possibility of contamination by water supply pipes.Conclusions:Cu, Zn and Cr play a specific role in the pathophysiology of diabetic nephropathy. Meanwhile in these patients, low serum levels of Cu, Zn and Cr were not associated with factors such as drinking water. Possible causes should be sought in other factors like urine, intervention factors in absorption and utilization and individual conditions.

A Meta-Analysis of Renal Function After Adult Cardiac Surgery With Pulsatile Perfusion.

The aim of this meta-analysis was to determine whether pulsatile perfusion during cardiac surgery has a lesser effect on renal dysfunction than nonpulsatile perfusion after cardiac surgery in randomized controlled trials. MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials were used to identify available articles published before April 25, 2014. Meta-analysis was conducted to determine the effects of pulsatile perfusion on postoperative renal functions, as determined by creatinine clearance (CrCl), serum creatinine (Cr), urinary neutrophil gelatinase-associated lipocalin (NGAL), and the incidences of acute renal insufficiency (ARI) and acute renal failure (ARF). Nine studies involving 674 patients that received pulsatile perfusion and 698 patients that received nonpulsatile perfusion during cardiopulmonary bypass (CPB) were considered in the meta-analysis. Stratified analysis was performed according to effective pulsatility or unclear pulsatility of the pulsatile perfusion method in the presence of heterogeneity. NGAL levels were not significantly different between the pulsatile and nonpulsatile groups. However, patients in the pulsatile group had a significantly higher CrCl and lower Cr levels when the analysis was restricted to studies on effective pulsatile flow (P < 0.00001, respectively). The incidence of ARI was significantly lower in the pulsatile group (P < 0.00001), but incidences of ARF were similar. In conclusion, the meta-analysis suggests that the use of pulsatile flow during CPB results in better postoperative renal function.

Chromium toxicity tolerance of Solanum nigrum L. and Parthenium hysterophorus L. plants with reference to ion pattern, antioxidation activity and root exudation

Chromium (Cr), being a highly toxic metal, adversely affects the mineral uptake and metabolic processes in plants when present in excess. The current study was aimed at investigating the Cr accumulation in various plant tissues and its relation to the antioxidation activity and root exudation. Plants were grown in soil spiked with different concentrations of Cr for three weeks in pots and analysed for different growth, antioxidants and ion attributes. Furthermore, plants treated with different concentrations of Cr in pots were shifted to rhizobox-like system for 48h and organic acids were monitored in the mucilage dissolved from the plant root surface, mirroring rhizospheric solution. The results revealed that the Cr application at 1mM increased the shoot fresh and dry weight and root dry weight of Solanum nigrum, whereas the opposite was observed for Parthenium hysterophorus when compared with lower levels of Cr (0.5mM) or control treatment. In both plant species, Cr and Cl concentrations were increased while Ca, Mg and K concentrations in root, shoot and root exudates were decreased with increasing levels of Cr. Higher levels of Cr treatments enhanced the activities of SOD, POD and proline content in leaves of S. nigrum, whereas lower levels of Cr treatment were found to have stimulatory effects in P. hysterophorus. P. hysterophorus exhibited highest exudation of organic acid contents. With increasing levels of Cr treatments, citric acid concentration in root exudates increased by 35% and 44% in S. nigrum, whereas 20% and 76% in P. hysterophorus. Cr toxicity was responsible for the shoot growth reduction of S. nigrum and P. hysterophorus, however, shoot growth response was different at different levels of applied Cr. Consequently, Cr stress negatively altered the plant physiology and biochemistry. However, the enhanced antioxidant production, Cl uptake and root exudation are the physiological and biochemical indicators for the plant adaptations in biotic systems polluted with Cr.

Impact of solid fuel combustion technology on valence speciation of chromium in fly ash

Fly ash (FA) generated in real furnaces was used to evaluate the impact of the kind of the solid fuel burnt and combustion technology on chromium speciation, particularly the presence of Cr(III) and Cr(VI) forms as well as readily and hardly leachable chromium(VI) species in FAs. The FAs originated from a pulverized coal combustion boiler (PCC boiler), a fluidized bed combustion boiler (FBC boiler), a stoker-fired boiler (SF boiler), a municipal solid waste incinerator (MSWI), a cement rotary kiln (CRK) and a modern domestic boiler (DB). The speciation analysis of chromium was carried out by means of extraction followed by catalytic cathodic stripping voltammetry with adsorption of Cr(III)-DTPA complexes (CCSV-DTPA) for determination of Cr(VI) and AAS was used for determination of Cr content.It has been revealed that the antagonistic action of alkali metal compounds and iron oxides plays a crucial role in shaping valence speciation of chromium. According to the proposed transformation path of oxidation of Cr(III) to Cr(VI), hard coal combustion in an SF boiler, an FBC boiler or a domestic boiler will generate FAs with a low Cr(VI) level. Replacing fuel with biomass should create favorable conditions for generating FA enriched with Cr(VI). Relatively high concentrations of Cr(VI) can also be expected in FA generated in the process of high-temperature combustion of coal in PCC boilers.

Chromate alters root system architecture and activates expression of genes involved in iron homeostasis and signaling in Arabidopsis thaliana

Soil contamination by hexavalent chromium [Cr(VI) or chromate] due to anthropogenic activities has become an increasingly important environmental problem. To date few studies have been performed to elucidate the signaling networks involved on adaptive responses to (CrVI) toxicity in plants. In this work, we report that depending upon its concentration, Cr(VI) alters in different ways the architecture of the root system in Arabidopsis thaliana seedlings. Low concentrations of Cr (20-40µM) promoted primary root growth, while concentrations higher than 60µM Cr repressed growth and increased formation of root hairs, lateral root primordia and adventitious roots. We analyzed global gene expression changes in seedlings grown in media supplied with 20 or 140µM Cr. The level of 731 transcripts was significantly modified in response to Cr treatment with only five genes common to both Cr concentrations. Interestingly, 23 genes related to iron (Fe) acquisition were up-regulated including IRT1, YSL2, FRO5, BHLH100, BHLH101 and BHLH039 and the master controllers of Fe deficiency responses PYE and BTS were specifically activated in pericycle cells. It was also found that increasing concentration of Cr in the plant correlated with a decrease in Fe content, but increased both acidification of the rhizosphere and activity of the ferric chelate reductase. Supply of Fe to Cr-treated Arabidopsis allowed primary root to resume growth and alleviated toxicity symptoms, indicating that Fe nutrition is a major target of Cr stress in plants. Our results show that low Cr levels are beneficial to plants and that toxic Cr concentrations activate a low-Fe rescue system.

Calcium supplements as source of trace elements: Adequacy and safety of supplements with vitamin C, vitamin D and phosphate formulations

Instrumental neutron activation analysis and atomic absorption spectrometry were used to quantify trace elements in different national and multinational Ca supplements categorized on the basis of Ca with vitamin D, vitamin C and phosphate formulations. The supplements were found to contain low levels of Co, Cr and Cu with elevated amounts of Fe, K and Na. Toxic elements (As, Cd and Sb) were detected in very few samples at very low concentrations. The essential elements contribute to >3% of their respective Dietary Reference Intakes.

Evaluation of chromium and manganese in biological samples (scalp hair, blood and urine) of tuberculosis and diarrhea male human immunodeficiency virus patients.

The consequence of trace elements deficiency has been associated with an increased risk of human immunodeficiency virus type 1 (HIV-1) disease progression and mortality. This study examined the association between high concentrations of chromium (Cr) and manganese (Mn) in scalp hair, blood, and urine and opportunistic infections in hospitalized patients with the acquired immune deficiency syndrome (AIDS). The study was performed on 62 male HIV+ patients (HIV-1) from different cities of Pakistan. The patients were divided in two groups according to secondary infections (tuberculosis, diarrhea, or high fever). The biological samples (scalp hair, blood and urine) were collected from AIDS patients, and for comparative study 120 healthy subjects (males) of same age group (31 - 45 years), socio-economic status, localities, and dietary habits were also included. The elements in the biological samples were analyzed by electrothermal atomic absorption spectrophotometry after microwave-assisted acid digestion. The validity and accuracy of the methodology was checked by using certified reference materials (CRMs) and with the values obtained by conventional wet acid digestion method on the same CRMs. The results indicated significantly lower concentrations of Cr and Mn in the biological samples (scalp hair, blood, and urine) of male HIV-1 patients, compared with control subjects. It was observed that the lower levels of these trace elements may be predictors for secondary infections in HIV-1 patients. There was a significant decrease in mean values of Cr and Mn in whole blood and scalp hair, whilst higher concentrations were observed in urine samples of the three groups of AIDS patients as compared to a controlled healthy male group (p < 0.001). Low Cr and Mn levels may be due to increased Cr and Mn losses. These data present guidance to clinicians and other professional investigating deficiencies of Cr and Mn in biological samples of AIDS patients.

Determination of trace heavy metals in environmental and biological samples by solution cathode glow discharge-atomic emission spectrometry and addition of ionic surfactants for improved sensitivity

Solution cathode glow discharge-atomic emission spectrometry (SCGD-AES) was evaluated for its ability to determine toxic heavy metals, including cadmium (Cd), mercury (Hg), lead (Pb), and chromium (Cr), in environmental and biological samples. A significant enhancement in heavy metal signal was observed by addition of a small amount of cetyltrimethylammoniumchloride (CTAC, C16H33 (CH3)3NCl) to the samples. The net intensity of atomic emission lines of Cd, Hg, Pb, and Cr increased by 2.1-, 4.8-, 6.6-, and 2.6-fold, respectively, after addition of 0.15% CTAC to the test solutions. The effects of ionic surfactants (CTAC) compared with non-ionic surfactants, e.g., Triton x-45 and Triton x-100, on the sensitivity of Cd, Hg, Pb, and Cr were also investigated in the present study. The enhancement effect is in the order Triton x-45<Triton x-100<CTAC for Hg, Pb and Cr and Triton x-45<CTAC<Triton x-100 for Cd. Addition of CTAC to the electrolyte solutions decreased the background intensity and fluctuation of atomic emission lines of studied metals. It also changed the surface tension and the viscosity, and increased average discharge current of electrolyte solution. SCGD sensitivity to the heavy metals greatly improved by addition of the surfactant. The improved detection limits of Cd, Hg, Pb, and Cr were 1.0, 7.0, 2.0, and 42 ng mL(-1), respectively. The proposed method was validated by quantifying Cd, Hg, Pb, and Cr in certified reference materials, including human hair (GBW 09101b) and stream sediment (GBW 07310 and GBW07311). Measurement results obtained for the determination of Cd, Hg, Pb, and Cr in the reference materials agreed well with reference values. This study improves the application of SCGD-AES in quantifying very low levels of Cd, Hg, Pb, and Cr from biological and environmental materials.

Phytoremediation ability of some floricultural plant species

Chromium (Cr) is one of the most common heavy metals affecting the soil quality which is introduced into the environment from industries such as leather tanning, electroplating and inorganic pigment (green, orange and yellow) production. The leather industry is the major source for the environmental influx of Cr. Cleaning up of the Cr contaminated sites is a challenging task. Phytoremediation is an emerging area that could be considered for the remediation of contaminated sites because of its cost effectiveness and aesthetic advantages. An experiment was therefore was conducted to study the phytoremediation ability of different floriculture plant species (calendula, chrysanthemum, aster and dahlia). In all the four plant species, Cr beyond 10 ppm was toxic to the plants resulting in a drastic reduction in growth of plants. At 25 ppm, Cr mediated mortality of the plants was observed in chrysanthemum. In calendula and dahlia the application of Cr beyond 10 ppm inhibited flowering. The data on the partitioning of Cr revealed that the highest concentration of Cr was found in the roots and was followed by shoots and flowers. Dahlia recorded the highest concentration of Cr and calendula the least. Our results suggest that, among the four floriculture plant species only calendula is a good candidate for phytoremediation of soils contaminated with low level of Cr (up to 10 ppm).

Biomonitoring study of an estuarine coastal ecosystem, the Sacca di Goro lagoon, using Ruditapes philippinarum (Mollusca: Bivalvia)

Coastal lagoons are constantly subjected to releases of chemical pollutants, and so organisms may be exposed to such toxicants. This study investigated through a multivariate approach the physiological status of bivalve Ruditapes philippinarum, farmed in Sacca di Goro lagoon. Biomarkers at different levels of biological organization (catalase, superoxide dismutase, genotoxicity, reburrowing behavior) were evaluated at three sites exposed to different environmental conditions. A seasonal trend was observed, and micronucleus frequency was significantly lowest at the relatively pristine reference site. Enzymatic activity toward oxyradicals be quite efficient since variations in responsiveness were not consistent. However, behavioral impairment was observed in reburrowing rates. Sediment concentrations showed low PAH levels and high natural levels of trace metals Cr and Ni. DistLM statistical analysis revealed a non-significant relationship between selected biomarkers and xenobiotics. Therefore other potentially toxic compounds in admixture at low doses may be involved in driving differing spatial distribution of physiological impairment.

Silicon Mediated the Detoxification of Cr on Pakchoi (Brassica Chinensis L.) in Cr-contaminated Soil

Abstract To test the hypothesis that exogenous silicon (Si) would mediate the detoxification of Chromium (Cr) on pakchoi ( Brassica Chinensis L.) growing in Cr-contaminated soil, a pot experiment that 0, 50, 100 and 200 mg·kg -1 Cr (Na 2 Cr 2 O 7 2H 2 O) were supplied to soil together with 0, 0.5, 1.0 and 1.5 g·kg-1 Si (Na2SiO3) for 48 days, was studied. Results showed that supplying Si improved the growth of pakchoi in low Cr level. However, the shoot dry weight decreased with the increasing Si supplied in high Cr level. Compared with under non-Cr stress, the application of Si significantly increased the activities of POD, SOD and CAT of pakchoi under excess Cr. However, antioxidant enzymes activities displayed no difference under three Cr levels supplied. Shoot Cr accumulation decreased, while root Cr concentration increased, which was ascribed to the formation of precipitation-bound, “organic matter bound” Cr and the reduction of exchangeable-bound Cr fractions in the soil. Furthermore, the rhizosphere soil pH increased with Si level under either Cr level, suggesting that exogenous Si would induce the alkalization in the rhizosphere mediated detoxification of Cr on pakchoi by promoting the formation of precipitation-bound, organic matter bound Cr in Cr-contaminated soil, thereby probably decreasing Cr uptake from Cr-contaminated soil. These results proved direct evidence that Si played a mediated role, which decreased Cr uptake and improved the stabilization of Cr in Cr- contaminated soil.

Effect of Chromium on La0.6Sr0.4Co0.2Fe0.8O3-δ Solid Oxide Fuel Cell Cathodes

The transfer of chromium from metallic components into the cathode of a solid oxide fuel cell (SOFC) can severely degrade its performance and is known as ‘chromium poisoning’. In this study we investigate the relationship between the amount of chromium introduced into La0.6Sr0.4Co0.2Fe0.8O3-δ, LSCF (6428), cathodes and their electrochemical performance, and clarify further the poisoning mechanism. LSCF cathodes were screen printed onto Ce0.9Gd0.1O1.95 electrolyte pellets and infiltrated with Cr(NO3)3 solutions to different Cr levels up to 2 wt%. Electrochemical impedance spectroscopy at 500–800°C showed that even very low levels of Cr give a significant increase in cathode polarization resistance, which increases with Cr concentration. The impedance response was analyzed using the model of Adler, Lane and Steele to extract oxygen self-diffusion (DO) and surface exchange (kO) parameters for the LSCF. The results show that Cr reduces both DO and kO, the latter being the more affected. However, the activation energies for polarization resistance, DO and kO are not significantly affected by Cr content. This indicates that the Cr poisoning mechanism involves the de-activation of sites for oxygen exchange on the LSCF surface and that the cathode's residual activity is by means of remaining active sites.

1H MRSI of middle frontal gyrus in pediatric ADHD

Neuroimaging studies in multiple modalities have implicated the left or right dorsolateral prefrontal cortex (here, middle frontal gyrus) in attentional functions, in ADHD, and in dopamine agonist treatment of ADHD. The far lateral location of this cortex in the brain, however, has made it difficult to study with magnetic resonance spectroscopy (MRS). We used the smaller voxel sizes of the magnetic resonance spectroscopic imaging (MRSI) variant of MRS, acquired at a steep coronal-oblique angle to sample bilateral middle frontal gyrus in 13 children and adolescents with ADHD and 13 age- and sex-matched healthy controls. Within a subsample of the ADHD patients, aspects of attention were also assessed with the Trail Making Task. In right middle frontal gyrus only, mean levels of N-acetyl-aspartate + N-acetyl-aspartyl-glutamate (tNAA), creatine + phosphocreatine (Cr), choline-compounds (Cho), and myo-inositol (mI) were significantly lower in the ADHD than in the control sample. In the ADHD patients, lower right middle frontal Cr was associated with worse performance on Trails A and B (focused attention, concentration, set-shifting), while the opposite relationship held true for the control group on Trails B. These findings add to evidence implicating right middle frontal cortex in ADHD. Lower levels of these multiple species may reflect osmotic adjustment to elevated prefrontal cortical perfusion in ADHD and/or a previously hypothesized defect in astrocytic production of lactate in ADHD resulting in decelerated energetic metabolism (Cr), membrane synthesis (Cho, mI), and acetyl-CoA substrate for NAA synthesis. Lower Cr levels may indicate attentional or executive impairments.

The Effect of Chromium on the Optical Properties and Photoactivity of Nano-Particulate Rutile

Chromium doped rutile TiO2was synthesized by either co-precipitation or impregnation (surface-doping) and characterized by XRD and reflectance spectroscopy. Chromium addition did not change the TiO2structure nor did the structure of the co-precipitated products differ from that of the impregnated samples. However, chromium doping moved the absorption of both sets of products into the visible and significantly affected the TiO2photocatalytic activity for isopropanol (IPA) oxidation. At high chromium concentrations the photoactivity of the co-precipitated samples was reduced by a larger amount than that of the impregnated samples; this was attributed to a higher concentration of Cr3+ions in the rutile lattice. Unexpectedly, increased photoactivity was measured for low Cr levels of surface-doped rutile. This may be caused by increased electron-trapping, at surface Cr6+ions, and correspondingly reduced, electron-hole recombination.

Separation and spectrophotometric determination of very low levels of Cr(VI) in water samples by novel pyridine-functionalized mesoporous silica

A modified SBA-15 mesoporous silica was developed, as an adsorbent, for the removal of Cr(VI) ions from natural-water samples. The effects of experimental parameters, including pH of solution, sample and eluent flow rate, the eluent composition, the eluent volume, and the effect of coexisting ions on the separation and determination of Cr(VI), were investigated. It was shown that Cr(VI) was selectively adsorbed from aqueous solution at pH 3, but Cr(III) could be adsorbed from solution at alkaline pH range. The retained Cr(VI) was eluted with 0.5 mol L−1 KCl solution in 0.1 mol L−1 Na2CO3 subsequently. Under the optimum conditions, the modified mesoporous silica (py-SBA-15) with a high pore diameter exhibited an adsorption capacity of 136 mg g−1 and a lower limit of detection than 2.3 µg L−1 by using diphenylcarbazide as a chromophorous reagent for the determination of Cr(VI) ions. A preconcentration factor as high as 200 was calculated for Cr(VI). The loaded py-SBA-15 can be reactivated with recovery of more than 98.5% over at least eight cycles. The relative standard deviation (RSD) for Cr(VI) ion recovery was less than 1.8%. Validation of the outlined method was performed by analysing a certified reference material (BCR 544). The proposed method was applied to determine Cr(VI) value in natural and waste water samples successfully.