The Experts below are selected from a list of 17311221 Experts worldwide ranked by ideXlab platform
Zumriye Aksu - One of the best experts on this subject based on the ideXlab platform.
-
binary biosorption of cadmium ii and nickel ii onto dried chlorella vulgaris co ion effect on mono component isotherm parameters
Process Biochemistry, 2006Co-Authors: Zumriye Aksu, Gonul DonmezAbstract:Abstract The competitive biosorption of cadmium(II) and nickel(II) onto dried Chlorella vulgaris, a green alga from binary metal mixture was studied and compared with single metal ion situation in a batch stirred system. The effects of single- and dual-metal ion concentrations on the biosorption capacity of biomass were investigated at an initial pH value of 4.0. Equilibrium uptake of cadmium(II) and nickel(II)) increased with increasing its initial metal ion concentration up to 150 mg l−1 and decreased considerably by the presence of increasing concentrations of the other metal ion. Both the Freundlich and Langmuir adsorption models were suitable for describing the biosorption equilibrium of cadmium(II) and nickel(II) ions both in single and binary systems. According to the Langmuir model the maximum biosorption capacity of dried alga was determined as 86.6 mg g−1 for cadmium(II) and as 58.4 mg g−1 for nickel(II) for single ion situation. These values dropped to 68.5 mg g−1 for cadmium(II) and to 28.3 mg g−1 for nickel(II) when co-ion concentration was kept at 150 mg l−1. For each metal ion, variation of isotherm constants due to the level of other metal ion were expressed as a function of initial co-ion concentration by non-linear regression techniques.
-
binary biosorption of iron iii and iron iii cyanide complex ions on rhizopus arrhizus modelling of synergistic interaction
Process Biochemistry, 2002Co-Authors: Zumriye Aksu, Hanife GulenAbstract:Abstract Many heavy metal-bearing wastewaters also contain their metal cyanide complex ions. Although the biosorption of single or multi-metal ions to various microorganisms has been extensively studied, very little attention has been given to the bioremoval and the expression of the adsorption equilibrium and kinetics of metal–metal cyanide complex ion systems. In this study, the simultaneous biosorption of iron(III) (ferric) cations and iron(III)-cyanide complex (ferricyanide) anions to Rhizopus arrhizus from binary mixtures was studied and compared with single metal and metal cyanide complex ion situation in a batch stirred system. The effects of initial pH and single and dual-component concentrations on the biosorption kinetics and equilibrium uptake of each component, both singly and in mixture were investigated. The working pH value for both species was determined as 2.0. Multi-component biosorption studies were also performed at this pH value. The biosorption rates and equilibrium uptakes of iron(III) or iron(III)-cyanide complex ions increased by the presence of increasing concentrations of the other ion up to 200 mg l−1 for iron(III) and up to 1000 mg l−1 for iron(III)-cyanide complex ions. This situation showed a synergistic interaction between these ions. The Freundlich, Langmuir and Redlich–Peterson adsorption models were used to predict the mono-component equilibrium uptake and model parameters were estimated by the non-linear regression. It was seen that the mono-component adsorption equilibrium data fitted very well to the mono-component Langmuir and Redlich–Peterson models for both the components at moderate ranges of concentration. A modified synergistic Langmuir model was proposed for dual-component system and model parameters were also estimated by the non-linear regression. The pseudo second-order kinetic model was applied to single and multi-component experimental data assuming that the external mass transfer limitations in the system can be neglected and biosorption is sorption controlled.
-
a comparative study of various biosorbents for removal of chromium vi ions from industrial waste waters
Process Biochemistry, 1994Co-Authors: M Nourbakhsh, Tulin Kutsal, Dursun Ozer, Zumriye Aksu, Arif CaglarAbstract:Abstract Chromium(VI) biosorption to non-living biomass of Chlorella vulgaris, Clodophara crispata, Zoogloea ramigera, Rhizopus arrhizus and Saccharomyces cerevisiae was investigated. The initial pH of the metal ion solution effected metal uptake capacity of the biomass and the optimum initial pH was found as 1·–2·0 for all microorganisms. Maximum adsorption rates of metal ions to microbial biomass were obtained at temperatures in the range 25–35°C. The adsorption rate increased with increasing metal ion concentration for C. vulgaris, C. crispata, R. Arrhizus, S. cerevisiae and Z. ramigera up to 200, 200, 125, 100 and 75 mg/litre, respectively. Freundlich constants were determined from the Freundlich adsorption isotherms of all microorganisms.
J A Skinner - One of the best experts on this subject based on the ideXlab platform.
-
surveillance of patients with metal on metal hip resurfacing and total hip prostheses a prospective cohort study to investigate the relationship between blood metal ion levels and implant failure
Journal of Bone and Joint Surgery American Volume, 2014Co-Authors: Alister Hart, J A Skinner, Sa Sabah, B Sampson, Jonathan J Powell, Luigi Palla, K J J Pajamaki, Timo Puolakka, Aleksi Reito, Antti EskelinenAbstract:Background: We designed a prospective, single-center study to assess whether blood metal ion levels could predict implant failure in patients managed with unilateral metal-on-metal hip resurfacing or total hip arthroplasty. Methods: Five hundred and ninety-seven patients who had received unilateral Articular Surface Replacement prostheses at least twelve months earlier were recruited. Blood metal ion levels were compared between the group of patients with failed implants and the group with non-failed implants. Implant failure was defined as prostheses associated with revision, an intention to revise, or poor patient-reported hip function (Oxford Hip Score, <31 of 48). Specificity, sensitivity, area under the curve, positive and negative predictive values, and odds ratios were calculated. Logistic regression analysis was used to identify other risk factors for implant failure. Results: Patients with failed arthroplasty had significantly higher blood cobalt and chromium ion levels than did patients with non-failed arthroplasty (p < 0.01). Blood cobalt ion levels were disproportionately raised in patients with failed total hip arthroplasty (8.2 μg/L) compared with patients with failed hip resurfacing (2.5 μg/L) (p = 0.018). Blood chromium ion levels were not significantly different in patients with failed total hip arthroplasty and failed hip resurfacing (p = 0.058). The maximum value of either metal ion had good discriminant ability to predict implant failure (area under the curve, 0.76). A 7-μg/L cutoff had a positive predictive value of 0.75 (95% confidence interval, 0.66 to 0.82) and a negative predictive value of 0.82 (95% confidence interval, 0.78 to 0.86). In patients managed with total hip arthroplasty, for each increase of 1 μg/L there was a 23% (p < 0.001) increase in the odds of them being in the failed group. For patients managed with hip resurfacing, the increase in odds was 5% (p < 0.001). Conclusions: Raised levels of blood metal ions were associated with failed metal-on-metal hip resurfacings and total hip arthroplasties. A threshold level of 7 μg/L had inadequate sensitivity to be used in isolation as a screening test for implant failure, but it provided nearly optimal misclassification rates. No level had a perfect positive predictive value, and so we discourage surgeons from performing revision surgery based on blood metal ion levels alone. Levels of cobalt ions were raised out of proportion to levels of chromium ions in failed total hip arthroplasty and may reflect a different mechanism for metal ion generation. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.
-
Surveillance of Patients with Metal-on-Metal Hip Resurfacing and Total Hip Prostheses: A Prospective Cohort Study to Investigate the Relationship Between Blood Metal Ion Levels and Implant Failure.
'Ovid Technologies (Wolters Kluwer Health)', 2014Co-Authors: Aj Hart, J A Skinner, Sa Sabah, Sampson B, Jj Powell, Palla L, Pajamäki Kjj, Puolakka T, Reito A, Eskelinen AAbstract:BACKGROUND: We designed a prospective, single-center study to assess whether blood metal ion levels could predict implant failure in patients managed with unilateral metal-on-metal hip resurfacing or total hip arthroplasty. METHODS: Five hundred and ninety-seven patients who had received unilateral Articular Surface Replacement prostheses at least twelve months earlier were recruited. Blood metal ion levels were compared between the group of patients with failed implants and the group with non-failed implants. Implant failure was defined as prostheses associated with revision, an intention to revise, or poor patient-reported hip function (Oxford Hip Score,
-
an analysis of metal ion levels in the joint fluid of symptomatic patients with metal on metal hip replacements
Journal of Bone and Joint Surgery-british Volume, 2011Co-Authors: Kinner Davda, J A Skinner, Ferdinand V Lali, Barry Sampson, Alister HartAbstract:We retrospectively analysed concentrations of chromium and cobalt ions in samples of synovial fluid and whole blood taken from a group of 92 patients with failed current-generation metal-on-metal hip replacements. We applied acid oxidative digestion to our trace metal analysis protocol, which found significantly higher levels of metal ion concentrations in blood and synovial fluid than a non-digestive method. Patients were subcategorised by mode of failure as either 'unexplained pain' or 'defined causes'. Using this classification, chromium and cobalt ion levels were present over a wider range in synovial fluid and not as strongly correlated with blood ion levels as previously reported. There was no significant difference between metal ion concentrations and manufacturer of the implant, nor femoral head size below or above 50 mm. There was a moderately positive correlation between metal ion levels and acetabular component inclination angle as measured on three-dimensional CT imaging. Our results suggest that acid digestion of samples of synovial fluid samples is necessary to determine metal ion concentrations accurately so that meaningful comparisons can be made between studies.
-
circulating levels of cobalt and chromium from metal on metal hip replacement are associated with cd8 t cell lymphopenia
Journal of Bone and Joint Surgery-british Volume, 2009Co-Authors: Aj Hart, J A Skinner, P Winship, Nuno Jorge Rodrigues Faria, Elena Kulinskaya, D Webster, S Muirheadallwood, C H Aldam, H A Anwar, Jonathan J PowellAbstract:We carried out a cross-sectional study with analysis of the demographic, clinical and laboratory characteristics of patients with metal-on-metal hip resurfacing, ceramic-onceramic and metal-on-polyethylene hip replacements. Our aim was to evaluate the relationship between metal-on-metal replacements, the levels of cobalt and chromium ions in whole blood and the absolute numbers of circulating lymphocytes. We recruited 164 patients (101 men and 63 women) with hip replacements, 106 with metal-on-metal hips and 58 with Non-Metal-on-metal hips, aged < 65 years, with a pre-operative diagnosis of osteoarthritis and no pre-existing immunological disorders. Laboratory-defined T-cell lymphopenia was present in13 patients (15%) (CD8 + lymphopenia) and 11 patients (13%) (CD3 + lymphopenia) with unilateral metal-on-metal hips. There were significant differences in the absolute CD8 + lymphocyte subset counts for the metal-on-metal groups compared with each control group (p-values ranging between 0.024 and 0.046). Statistical modelling with analysis of covariance using age, gender, type of hip replacement, smoking and circulating metal ion levels, showed that circulating levels of metal ions, especially cobalt, explained the variation in absolute lymphocyte counts for almost all lymphocyte subsets.
Alister Hart - One of the best experts on this subject based on the ideXlab platform.
-
surveillance of patients with metal on metal hip resurfacing and total hip prostheses a prospective cohort study to investigate the relationship between blood metal ion levels and implant failure
Journal of Bone and Joint Surgery American Volume, 2014Co-Authors: Alister Hart, J A Skinner, Sa Sabah, B Sampson, Jonathan J Powell, Luigi Palla, K J J Pajamaki, Timo Puolakka, Aleksi Reito, Antti EskelinenAbstract:Background: We designed a prospective, single-center study to assess whether blood metal ion levels could predict implant failure in patients managed with unilateral metal-on-metal hip resurfacing or total hip arthroplasty. Methods: Five hundred and ninety-seven patients who had received unilateral Articular Surface Replacement prostheses at least twelve months earlier were recruited. Blood metal ion levels were compared between the group of patients with failed implants and the group with non-failed implants. Implant failure was defined as prostheses associated with revision, an intention to revise, or poor patient-reported hip function (Oxford Hip Score, <31 of 48). Specificity, sensitivity, area under the curve, positive and negative predictive values, and odds ratios were calculated. Logistic regression analysis was used to identify other risk factors for implant failure. Results: Patients with failed arthroplasty had significantly higher blood cobalt and chromium ion levels than did patients with non-failed arthroplasty (p < 0.01). Blood cobalt ion levels were disproportionately raised in patients with failed total hip arthroplasty (8.2 μg/L) compared with patients with failed hip resurfacing (2.5 μg/L) (p = 0.018). Blood chromium ion levels were not significantly different in patients with failed total hip arthroplasty and failed hip resurfacing (p = 0.058). The maximum value of either metal ion had good discriminant ability to predict implant failure (area under the curve, 0.76). A 7-μg/L cutoff had a positive predictive value of 0.75 (95% confidence interval, 0.66 to 0.82) and a negative predictive value of 0.82 (95% confidence interval, 0.78 to 0.86). In patients managed with total hip arthroplasty, for each increase of 1 μg/L there was a 23% (p < 0.001) increase in the odds of them being in the failed group. For patients managed with hip resurfacing, the increase in odds was 5% (p < 0.001). Conclusions: Raised levels of blood metal ions were associated with failed metal-on-metal hip resurfacings and total hip arthroplasties. A threshold level of 7 μg/L had inadequate sensitivity to be used in isolation as a screening test for implant failure, but it provided nearly optimal misclassification rates. No level had a perfect positive predictive value, and so we discourage surgeons from performing revision surgery based on blood metal ion levels alone. Levels of cobalt ions were raised out of proportion to levels of chromium ions in failed total hip arthroplasty and may reflect a different mechanism for metal ion generation. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.
-
an analysis of metal ion levels in the joint fluid of symptomatic patients with metal on metal hip replacements
Journal of Bone and Joint Surgery-british Volume, 2011Co-Authors: Kinner Davda, J A Skinner, Ferdinand V Lali, Barry Sampson, Alister HartAbstract:We retrospectively analysed concentrations of chromium and cobalt ions in samples of synovial fluid and whole blood taken from a group of 92 patients with failed current-generation metal-on-metal hip replacements. We applied acid oxidative digestion to our trace metal analysis protocol, which found significantly higher levels of metal ion concentrations in blood and synovial fluid than a non-digestive method. Patients were subcategorised by mode of failure as either 'unexplained pain' or 'defined causes'. Using this classification, chromium and cobalt ion levels were present over a wider range in synovial fluid and not as strongly correlated with blood ion levels as previously reported. There was no significant difference between metal ion concentrations and manufacturer of the implant, nor femoral head size below or above 50 mm. There was a moderately positive correlation between metal ion levels and acetabular component inclination angle as measured on three-dimensional CT imaging. Our results suggest that acid digestion of samples of synovial fluid samples is necessary to determine metal ion concentrations accurately so that meaningful comparisons can be made between studies.
Jonathan J Powell - One of the best experts on this subject based on the ideXlab platform.
-
surveillance of patients with metal on metal hip resurfacing and total hip prostheses a prospective cohort study to investigate the relationship between blood metal ion levels and implant failure
Journal of Bone and Joint Surgery American Volume, 2014Co-Authors: Alister Hart, J A Skinner, Sa Sabah, B Sampson, Jonathan J Powell, Luigi Palla, K J J Pajamaki, Timo Puolakka, Aleksi Reito, Antti EskelinenAbstract:Background: We designed a prospective, single-center study to assess whether blood metal ion levels could predict implant failure in patients managed with unilateral metal-on-metal hip resurfacing or total hip arthroplasty. Methods: Five hundred and ninety-seven patients who had received unilateral Articular Surface Replacement prostheses at least twelve months earlier were recruited. Blood metal ion levels were compared between the group of patients with failed implants and the group with non-failed implants. Implant failure was defined as prostheses associated with revision, an intention to revise, or poor patient-reported hip function (Oxford Hip Score, <31 of 48). Specificity, sensitivity, area under the curve, positive and negative predictive values, and odds ratios were calculated. Logistic regression analysis was used to identify other risk factors for implant failure. Results: Patients with failed arthroplasty had significantly higher blood cobalt and chromium ion levels than did patients with non-failed arthroplasty (p < 0.01). Blood cobalt ion levels were disproportionately raised in patients with failed total hip arthroplasty (8.2 μg/L) compared with patients with failed hip resurfacing (2.5 μg/L) (p = 0.018). Blood chromium ion levels were not significantly different in patients with failed total hip arthroplasty and failed hip resurfacing (p = 0.058). The maximum value of either metal ion had good discriminant ability to predict implant failure (area under the curve, 0.76). A 7-μg/L cutoff had a positive predictive value of 0.75 (95% confidence interval, 0.66 to 0.82) and a negative predictive value of 0.82 (95% confidence interval, 0.78 to 0.86). In patients managed with total hip arthroplasty, for each increase of 1 μg/L there was a 23% (p < 0.001) increase in the odds of them being in the failed group. For patients managed with hip resurfacing, the increase in odds was 5% (p < 0.001). Conclusions: Raised levels of blood metal ions were associated with failed metal-on-metal hip resurfacings and total hip arthroplasties. A threshold level of 7 μg/L had inadequate sensitivity to be used in isolation as a screening test for implant failure, but it provided nearly optimal misclassification rates. No level had a perfect positive predictive value, and so we discourage surgeons from performing revision surgery based on blood metal ion levels alone. Levels of cobalt ions were raised out of proportion to levels of chromium ions in failed total hip arthroplasty and may reflect a different mechanism for metal ion generation. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.
-
circulating levels of cobalt and chromium from metal on metal hip replacement are associated with cd8 t cell lymphopenia
Journal of Bone and Joint Surgery-british Volume, 2009Co-Authors: Aj Hart, J A Skinner, P Winship, Nuno Jorge Rodrigues Faria, Elena Kulinskaya, D Webster, S Muirheadallwood, C H Aldam, H A Anwar, Jonathan J PowellAbstract:We carried out a cross-sectional study with analysis of the demographic, clinical and laboratory characteristics of patients with metal-on-metal hip resurfacing, ceramic-onceramic and metal-on-polyethylene hip replacements. Our aim was to evaluate the relationship between metal-on-metal replacements, the levels of cobalt and chromium ions in whole blood and the absolute numbers of circulating lymphocytes. We recruited 164 patients (101 men and 63 women) with hip replacements, 106 with metal-on-metal hips and 58 with Non-Metal-on-metal hips, aged < 65 years, with a pre-operative diagnosis of osteoarthritis and no pre-existing immunological disorders. Laboratory-defined T-cell lymphopenia was present in13 patients (15%) (CD8 + lymphopenia) and 11 patients (13%) (CD3 + lymphopenia) with unilateral metal-on-metal hips. There were significant differences in the absolute CD8 + lymphocyte subset counts for the metal-on-metal groups compared with each control group (p-values ranging between 0.024 and 0.046). Statistical modelling with analysis of covariance using age, gender, type of hip replacement, smoking and circulating metal ion levels, showed that circulating levels of metal ions, especially cobalt, explained the variation in absolute lymphocyte counts for almost all lymphocyte subsets.
Antti Eskelinen - One of the best experts on this subject based on the ideXlab platform.
-
surveillance of patients with metal on metal hip resurfacing and total hip prostheses a prospective cohort study to investigate the relationship between blood metal ion levels and implant failure
Journal of Bone and Joint Surgery American Volume, 2014Co-Authors: Alister Hart, J A Skinner, Sa Sabah, B Sampson, Jonathan J Powell, Luigi Palla, K J J Pajamaki, Timo Puolakka, Aleksi Reito, Antti EskelinenAbstract:Background: We designed a prospective, single-center study to assess whether blood metal ion levels could predict implant failure in patients managed with unilateral metal-on-metal hip resurfacing or total hip arthroplasty. Methods: Five hundred and ninety-seven patients who had received unilateral Articular Surface Replacement prostheses at least twelve months earlier were recruited. Blood metal ion levels were compared between the group of patients with failed implants and the group with non-failed implants. Implant failure was defined as prostheses associated with revision, an intention to revise, or poor patient-reported hip function (Oxford Hip Score, <31 of 48). Specificity, sensitivity, area under the curve, positive and negative predictive values, and odds ratios were calculated. Logistic regression analysis was used to identify other risk factors for implant failure. Results: Patients with failed arthroplasty had significantly higher blood cobalt and chromium ion levels than did patients with non-failed arthroplasty (p < 0.01). Blood cobalt ion levels were disproportionately raised in patients with failed total hip arthroplasty (8.2 μg/L) compared with patients with failed hip resurfacing (2.5 μg/L) (p = 0.018). Blood chromium ion levels were not significantly different in patients with failed total hip arthroplasty and failed hip resurfacing (p = 0.058). The maximum value of either metal ion had good discriminant ability to predict implant failure (area under the curve, 0.76). A 7-μg/L cutoff had a positive predictive value of 0.75 (95% confidence interval, 0.66 to 0.82) and a negative predictive value of 0.82 (95% confidence interval, 0.78 to 0.86). In patients managed with total hip arthroplasty, for each increase of 1 μg/L there was a 23% (p < 0.001) increase in the odds of them being in the failed group. For patients managed with hip resurfacing, the increase in odds was 5% (p < 0.001). Conclusions: Raised levels of blood metal ions were associated with failed metal-on-metal hip resurfacings and total hip arthroplasties. A threshold level of 7 μg/L had inadequate sensitivity to be used in isolation as a screening test for implant failure, but it provided nearly optimal misclassification rates. No level had a perfect positive predictive value, and so we discourage surgeons from performing revision surgery based on blood metal ion levels alone. Levels of cobalt ions were raised out of proportion to levels of chromium ions in failed total hip arthroplasty and may reflect a different mechanism for metal ion generation. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.
