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Objective: Previous work suggested that the ultrasound-based benign Simple Descriptors can reliably exclude malignancy in a large proportion of women presenting with an adnexal mass. We aim to validate a modified version of the Benign Simple Descriptors (BD), and we introduce a two-step strategy to estimate the risk of malignancy: if the BDs do not apply, the ADNEX model is used to estimate the risk of malignancy. Methods: This is a retrospective analysis using the data from the 2-year interim analysis of the IOTA5 study, in which consecutive patients with at least one adnexal mass were recruited irrespective of subsequent management (conservative or surgery). The main outcome was classification of tumors as benign or malignant, based on histology or on clinical and ultrasound information during one year of follow-up. Multiple imputation was used when outcome based on follow-up was uncertain according to predefined criteria. Results: 8519 patients were recruited at 36 centers between 2012 and 2015. We included all masses that were not already in follow-up at recruitment from 17 centers with good quality surgical and follow-up data, leaving 4905 patients for statistical analysis. 3441 (70%) tumors were benign, 978 (20%) malignant, and 486 (10%) uncertain. The BDs were applicable in 1798/4905 (37%) tumors, and 1786 (99.3%) of these were benign. The two-step strategy based on ADNEX without CA125 had an area under the receiver operating characteristic curve (AUC) of 0.94 (95% CI, 0.91-0.95). The risk of malignancy was slightly underestimated, but calibration varied between centers. A sensitivity analysis in which we expanded the definition of uncertain outcome resulted in 1419 (29%) tumors with uncertain outcome and an AUC of the two-step strategy without CA125 of 0.93 (95% CI, 0.91-0.95). Conclusion: A large proportion of adnexal masses can be classified as benign by the BDs. For the remaining masses the ADNEX model can be used to estimate the risk of malignancy. This more...

Importance: Correct diagnosis of ovarian cancer results in better prognosis. Adnexal lesions can be stratified into the Ovarian-Adnexal Reporting and Data System (O-RADS) risk of malignancy categories with either the O-RADS lexicon, proposed by the American College of Radiology, or the International Ovarian Tumor Analysis (IOTA) 2-step strategy. Objective: To investigate the diagnostic performance of the O-RADS lexicon and the IOTA 2-step strategy. Design, Setting, and Participants: Retrospective external diagnostic validation study based on interim data of IOTA5, a prospective international multicenter cohort study, in 36 oncology referral centers or other types of centers. A total of 8519 consecutive adult patients presenting with an adnexal mass between January 1, 2012, and March 1, 2015, and treated either with surgery or conservatively were included in this diagnostic study. Twenty-five patients were excluded for withdrawal of consent, 2777 were excluded from 19 centers that did not meet predefined data quality criteria, and 812 were excluded because they were already in follow-up at recruitment. The analysis included 4905 patients with a newly detected adnexal mass in 17 centers that met predefined data quality criteria. Data were analyzed from January 31 to March 1, 2022. Exposures: Stratification into O-RADS categories (malignancy risk <1%, 1% to <10%, 10% to <50%, and ≥50%). For the IOTA 2-step strategy, the stratification is based on the individual risk of malignancy calculated with the IOTA 2-step strategy. Main Outcomes and Measures: Observed prevalence of malignancy in each O-RADS risk category, as well as sensitivity and specificity. The reference standard was the status of the tumor at inclusion, determined by histology or clinical and ultrasonographic follow-up for 1 year. Multiple imputation was used for uncertain outcomes owing to inconclusive follow-up information. Results: Median age of the 4905 patients was 48 years (IQR, 36-62 years). more...

Objective: Previous work has suggested that the ultrasound-based benign simple descriptors (BDs) can reliably exclude malignancy in a large proportion of women presenting with an adnexal mass. This study aimed to validate a modified version of the BDs and to validate a two-step strategy to estimate the risk of malignancy, in which the modified BDs are followed by the Assessment of Different NEoplasias in the adneXa (ADNEX) model if modified BDs do not apply. Methods: This was a retrospective analysis using data from the 2-year interim analysis of the International Ovarian Tumor Analysis (IOTA) Phase-5 study, in which consecutive patients with at least one adnexal mass were recruited irrespective of subsequent management (conservative or surgery). The main outcome was classification of tumors as benign or malignant, based on histology or on clinical and ultrasound information during 1 year of follow-up. Multiple imputation was used when outcome based on follow-up was uncertain according to predefined criteria. Results: A total of 8519 patients were recruited at 36 centers between 2012 and 2015. We excluded patients who were already in follow-up at recruitment and all patients from 19 centers that did not fulfil our criteria for good-quality surgical and follow-up data, leaving 4905 patients across 17 centers for statistical analysis. Overall, 3441 (70%) tumors were benign, 978 (20%) malignant and 486 (10%) uncertain. The modified BDs were applicable in 1798/4905 (37%) tumors, of which 1786 (99.3%) were benign. The two-step strategy based on ADNEX without CA125 had an area under the receiver-operating-characteristics curve (AUC) of 0.94 (95% CI, 0.92–0.96). The risk of malignancy was slightly underestimated, but calibration varied between centers. A sensitivity analysis in which we expanded the definition of uncertain outcome resulted in 1419 (29%) tumors with uncertain outcome and an AUC of the two-step strategy without CA125 of 0.93 (95% CI, 0.91–0.95). Conclusion more...

ObjectivePrevious work has suggested that the ultrasound-based benign simple descriptors (BDs) can reliably exclude malignancy in a large proportion of women presenting with an adnexal mass. This study aimed to validate a modified version of the BDs and to validate a two-step strategy to estimate the risk of malignancy, in which the modified BDs are followed by the Assessment of Different NEoplasias in the adneXa (ADNEX) model if modified BDs do not apply. MethodsThis was a retrospective analysis using data from the 2-year interim analysis of the International Ovarian Tumor Analysis (IOTA) Phase-5 study, in which consecutive patients with at least one adnexal mass were recruited irrespective of subsequent management (conservative or surgery). The main outcome was classification of tumors as benign or malignant, based on histology or on clinical and ultrasound information during 1 year of follow-up. Multiple imputation was used when outcome based on follow-up was uncertain according to predefined criteria. ResultsA total of 8519 patients were recruited at 36 centers between 2012 and 2015. We excluded patients who were already in follow-up at recruitment and all patients from 19 centers that did not fulfil our criteria for good-quality surgical and follow-up data, leaving 4905 patients across 17 centers for statistical analysis. Overall, 3441 (70%) tumors were benign, 978 (20%) malignant and 486 (10%) uncertain. The modified BDs were applicable in 1798/4905 (37%) tumors, of which 1786 (99.3%) were benign. The two-step strategy based on ADNEX without CA125 had an area under the receiver-operating-characteristics curve (AUC) of 0.94 (95% CI, 0.92-0.96). The risk of malignancy was slightly underestimated, but calibration varied between centers. A sensitivity analysis in which we expanded the definition of uncertain outcome resulted in 1419 (29%) tumors with uncertain outcome and an AUC of the two-step strategy without CA125 of 0.93 (95% CI, 0.91-0.95). ConclusionA large more...

Importance: Correct diagnosis of ovarian cancer results in better prognosis. Adnexal lesions can be stratified into the Ovarian-Adnexal Reporting and Data System (O-RADS) risk of malignancy categories with either the O-RADS lexicon, proposed by the American College of Radiology, or the International Ovarian Tumor Analysis (IOTA) 2-step strategy. Objective: To investigate the diagnostic performance of the O-RADS lexicon and the IOTA 2-step strategy. Design, Setting, and Participants: Retrospective external diagnostic validation study based on interim data of IOTA5, a prospective international multicenter cohort study, in 36 oncology referral centers or other types of centers. A total of 8519 consecutive adult patients presenting with an adnexal mass between January 1, 2012, and March 1, 2015, and treated either with surgery or conservatively were included in this diagnostic study. Twenty-five patients were excluded for withdrawal of consent, 2777 were excluded from 19 centers that did not meet predefined data quality criteria, and 812 were excluded because they were already in follow-up at recruitment. The analysis included 4905 patients with a newly detected adnexal mass in 17 centers that met predefined data quality criteria. Data were analyzed from January 31 to March 1, 2022. Exposures: Stratification into O-RADS categories (malignancy risk <1%, 1% to <10%, 10% to <50%, and ≥50%). For the IOTA 2-step strategy, the stratification is based on the individual risk of malignancy calculated with the IOTA 2-step strategy. Main Outcomes and Measures: Observed prevalence of malignancy in each O-RADS risk category, as well as sensitivity and specificity. The reference standard was the status of the tumor at inclusion, determined by histology or clinical and ultrasonographic follow-up for 1 year. Multiple imputation was used for uncertain outcomes owing to inconclusive follow-up information. Results: Median age of the 4905 patients was 48 years (IQR, 36-62 years). more...

OBJECTIVE: To evaluate the performance of diagnostic prediction models for ovarian malignancy in all patients with an ovarian mass managed surgically or conservatively. DESIGN: Multicentre cohort study. SETTING: 36 oncology referral centres (tertiary centres with a specific gynaecological oncology unit) or other types of centre. PARTICIPANTS: Consecutive adult patients presenting with an adnexal mass between January 2012 and March 2015 and managed by surgery or follow-up. MAIN OUTCOME MEASURES: Overall and centre specific discrimination, calibration, and clinical utility of six prediction models for ovarian malignancy (risk of malignancy index (RMI), logistic regression model 2 (LR2), simple rules, simple rules risk model (SRRisk), assessment of different neoplasias in the adnexa (ADNEX) with or without CA125). ADNEX allows the risk of malignancy to be subdivided into risks of a borderline, stage I primary, stage II-IV primary, or secondary metastatic malignancy. The outcome was based on histology if patients underwent surgery, or on results of clinical and ultrasound follow-up at 12 (±2) months. Multiple imputation was used when outcome based on follow-up was uncertain. RESULTS: The primary analysis included 17 centres that met strict quality criteria for surgical and follow-up data (5717 of all 8519 patients). 812 patients (14%) had a mass that was already in follow-up at study recruitment, therefore 4905 patients were included in the statistical analysis. The outcome was benign in 3441 (70%) patients and malignant in 978 (20%). Uncertain outcomes (486, 10%) were most often explained by limited follow-up information. The overall area under the receiver operating characteristic curve was highest for ADNEX with CA125 (0.94, 95% confidence interval 0.92 to 0.96), ADNEX without CA125 (0.94, 0.91 to 0.95) and SRRisk (0.94, 0.91 to 0.95), and lowest for RMI (0.89, 0.85 to 0.92). Calibration varied among centres for all models, however the ADNEX models and SRRisk were th more...

OBJECTIVE: To evaluate the performance of diagnostic prediction models for ovarian malignancy in all patients with an ovarian mass managed surgically or conservatively. DESIGN: Multicentre cohort study. SETTING: 36 oncology referral centres (tertiary centres with a specific gynaecological oncology unit) or other types of centre. PARTICIPANTS: Consecutive adult patients presenting with an adnexal mass between January 2012 and March 2015 and managed by surgery or follow-up. MAIN OUTCOME MEASURES: Overall and centre specific discrimination, calibration, and clinical utility of six prediction models for ovarian malignancy (risk of malignancy index (RMI), logistic regression model 2 (LR2), simple rules, simple rules risk model (SRRisk), assessment of different neoplasias in the adnexa (ADNEX) with or without CA125). ADNEX allows the risk of malignancy to be subdivided into risks of a borderline, stage I primary, stage II-IV primary, or secondary metastatic malignancy. The outcome was based on histology if patients underwent surgery, or on results of clinical and ultrasound follow-up at 12 (±2) months. Multiple imputation was used when outcome based on follow-up was uncertain. RESULTS: The primary analysis included 17 centres that met strict quality criteria for surgical and follow-up data (5717 of all 8519 patients). 812 patients (14%) had a mass that was already in follow-up at study recruitment, therefore 4905 patients were included in the statistical analysis. The outcome was benign in 3441 (70%) patients and malignant in 978 (20%). Uncertain outcomes (486, 10%) were most often explained by limited follow-up information. The overall area under the receiver operating characteristic curve was highest for ADNEX with CA125 (0.94, 95% confidence interval 0.92 to 0.96), ADNEX without CA125 (0.94, 0.91 to 0.95) and SRRisk (0.94, 0.91 to 0.95), and lowest for RMI (0.89, 0.85 to 0.92). Calibration varied among centres for all models, however the ADNEX models and SRRisk were th more...

Plasma lipoprotein (a) [Lp(a)] levels are largely determined by variation in the LPA gene, which codes for apo(a). Genome-wide association studies (GWASs) have identified nonsynonymous variants in LPA that associate with low Lp(a) levels, although their effect on apo(a) function is unknown. We investigated two such variants, R990Q and R1771C, which were present in four null Lp(a) individuals, for structural and functional effects. Sequence alignments showed the R990 and R1771 residues to be highly conserved and homologous to each other and to residues associated with plasminogen deficiency. Structural modeling showed both residues to make several polar contacts with neighboring residues that would be ablated on substitution. Recombinant expression of the WT and R1771C apo(a) in liver and kidney cells showed an abundance of an immature form for both apo(a) proteins. A mature form of apo(a) was only seen with the WT protein. Imaging of the recombinant apo(a) proteins in conjunction with markers of the secretory pathway indicated a poor transit of R1771C into the Golgi. Furthermore, the R1771C mutant displayed a glycosylation pattern consistent with ER, but not Golgi, glycosylation. We conclude that R1771 and the equivalent R990 residue facilitate correct folding of the apo(a) kringle structure and mutations at these positions prevent the proper folding required for full maturation and secretion. To our knowledge, this is the first example of nonsynonymous variants in LPA being causative of a null Lp(a) phenotype. more...

Background: Ovarian tumours are usually surgically removed because of the presumed risk of complications. Few large prospective studies on long-term follow-up of adnexal masses exist. We aimed to estimate the cumulative incidence of cyst complications and malignancy during the first 2 years of follow-up after adnexal masses have been classified as benign by use of ultrasonography. Methods: In the international, prospective, cohort International Ovarian Tumor Analysis Phase 5 (IOTA5) study, patients aged 18 years or older with at least one adnexal mass who had been selected for surgery or conservative management after ultrasound assessment were recruited consecutively from 36 cancer and non-cancer centres in 14 countries. Follow-up of patients managed conservatively is ongoing at present. In this 2-year interim analysis, we analysed patients who were selected for conservative management of an adnexal mass judged to be benign on ultrasound on the basis of subjective assessment of ultrasound images. Conservative management included ultrasound and clinical follow-up at intervals of 3 months and 6 months, and then every 12 months thereafter. The main outcomes of this 2-year interim analysis were cumulative incidence of spontaneous resolution of the mass, torsion or cyst rupture, or borderline or invasive malignancy confirmed surgically in patients with a newly diagnosed adnexal mass. IOTA5 is registered with ClinicalTrials.gov, number NCT01698632, and the central Ethics Committee and the Belgian Federal Agency for Medicines and Health Products, number S51375/B32220095331, and is ongoing. Findings: Between Jan 1, 2012, and March 1, 2015, 8519 patients were recruited to IOTA5. 3144 (37%) patients selected for conservative management were eligible for inclusion in our analysis, of whom 221 (7%) had no follow-up data and 336 (11%) were operated on before a planned follow-up scan was done. Of 2587 (82%) patients with follow-up data, 668 (26%) had a mass that was already in fo more...

Liver cancer is a poor prognosis cancer with limited treatment options. To develop a new therapeutic approach, we derived HCC cells from a known model of murine hepatocellular carcinoma (HCC). We treated adiponectin (APN) knock-out mice with the carcinogen diethylnitrosamine, and the resulting tumors were 7-fold larger than wild-type controls. Tumors were disassociated from both genotypes and their growth characteristics evaluated. A52 cells from APN KO mice had the most robust growth in vitro and in vivo, and presented with pathology similar to the parental tumor. All primary tumors and cell lines exhibited activity of the mammalian target of Rapamycin (mTOR) and Src pathways. Subsequent combinatorial treatment, with the mTOR inhibitor Rapamycin and the Src inhibitor Dasatinib reduced A52 HCC growth 29-fold in vivo. Through protein and histological analyzes we observed activation of these pathways in human HCC, suggesting that targeting both mTOR and Src may be a novel approach for the treatment of HCC. more...

Background: Ovarian tumours are usually surgically removed because of the presumed risk of complications. Few large prospective studies on long-term follow-up of adnexal masses exist. We aimed to estimate the cumulative incidence of cyst complications and malignancy during the first 2 years of follow-up after adnexal masses have been classified as benign by use of ultrasonography. Methods: In the international, prospective, cohort International Ovarian Tumor Analysis Phase 5 (IOTA5) study, patients aged 18 years or older with at least one adnexal mass who had been selected for surgery or conservative management after ultrasound assessment were recruited consecutively from 36 cancer and non-cancer centres in 14 countries. Follow-up of patients managed conservatively is ongoing at present. In this 2-year interim analysis, we analysed patients who were selected for conservative management of an adnexal mass judged to be benign on ultrasound on the basis of subjective assessment of ultrasound images. Conservative management included ultrasound and clinical follow-up at intervals of 3 months and 6 months, and then every 12 months thereafter. The main outcomes of this 2-year interim analysis were cumulative incidence of spontaneous resolution of the mass, torsion or cyst rupture, or borderline or invasive malignancy confirmed surgically in patients with a newly diagnosed adnexal mass. IOTA5 is registered with ClinicalTrials.gov, number NCT01698632, and the central Ethics Committee and the Belgian Federal Agency for Medicines and Health Products, number S51375/B32220095331, and is ongoing. Findings: Between Jan 1, 2012, and March 1, 2015, 8519 patients were recruited to IOTA5. 3144 (37%) patients selected for conservative management were eligible for inclusion in our analysis, of whom 221 (7%) had no follow-up data and 336 (11%) were operated on before a planned follow-up scan was done. Of 2587 (82%) patients with follow-up data, 668 (26%) had a mass that was already in fo more...

Some puzzles which arise in matrix models with multiple cuts are presented. They are present in the smoothed eigenvalue correlators of these models. First a method is described to calculate smoothed eigenvalue correlators in random matrix models with eigenvalues distributed in a single-cut, previous known results are reproduced. The method is extended to symmetric two-cut random matrix models. The correlators are written in a form suitable for application to mesoscopic systems. Connections are made with the smooth correlators derived using the Orthogonal Polynomial (OP) method. A few interesting observations are made regarding even and odd density-density correlators and cross-over correlators in $Z_2$ symmetric random matrix models., Comment: 20 pages Latex, three postscript figures more...

An attempt is made to solve the graph-isomorphism problem by first formulating it as an integer LP problem and then applying the Ellipsoid algorithm of L. G. Khachian. This provides some new insight into the complexity of the isomorphism problem. Additional keywords; Army research; reprints; Khachian algorithm; graph theory; linear programming; quadratic programming. (Author) more...

Although a respectable body of theoretical literature has emerged on parallel algorithms for graphs during the last ten years, scant attention has been paid to the real-life issues. These issues include (i) realistically buildable parallel computers with (ii) a bounded number of processors, with (iii) nonzero communication delays and synchronization overheads. Nor has much consideration been given to parallel processing of large weighted, sparse graphs along with suitable data structures for them. In this paper we discuss these issues and problems, which have to be faced while designing parallel programs to solve practical problems on large, sparse networks (i.e. weighted graphs) on general-purpose parallel computers that have been built or are being built. Only tightly-coupled, shared-memory MIMD (multiple instruction stream, multiple data stream) computers seem to fit the bill, at least in the present and the near future. more...

We prove an inverted version of A.J. Schwenk's result, which in turn is related to Ulman's reconstruction conjecture. We add a vertex v and join it to all other vertices of G to get a perturbed graph G+v. We derive an expression for the characteristic polynomial of the perturbed graph G+v and then show the extent to which the characteristic polynomials of the perturbed graphs can be used in determining whether two graphs are non-isomorphic. Keywords: Non-isomorphism of graphs; characteristic polynomial; reconstruction conjecture; graph perturbation. more...

Tests using mixtures of haematite and corundum (Al2O3) or haematite, quartz and corundum, in the presence of cells and metabolic products separated from bacterial culture pre-adapted to corundum over a period of 6 months, indicated that more than 99% of the haematite could be efficiently separated by selective flocculation of Al2O3 after desliming. Tests on a bauxite ore containing 85% Al2O3, 11% haematite and 4% silica gave similar results. Alumina-specific bioproteins and other non-protein compounds, secreted by the bacterial cells after adaptation, caused the flocculation of alumina as a result of their surface affinity for it. To preserve the beneficial acquired properties of the bacteria, it was essential to grow and preserve them continuously in the presence of Al2O3; reculturing in Bromfield medium in the absence of alumina led to a gradual loss of their separational ability., Tests using mixtures of haematite and corundum (Al2O3) or haematite, quartz and corundum, in the presence of cells and metabolic products separated from bacterial culture pre-adapted to corundum over a period of 6 months, indicated that more than 99% of the haematite could be efficiently separated by selective flocculation of Al2O3 after desliming. Tests on a bauxite ore containing 85% Al2O3, 11% haematite and 4% silica gave similar results. Alumina-specific bioproteins and other non-protein compounds, secreted by the bacterial cells after adaptation, caused the flocculation of alumina as a result of their surface affinity for it. To preserve the beneficial acquired properties of the bacteria, it was essential to grow and preserve them continuously in the presence of Al2O3; reculturing in Bromfield medium in the absence of alumina led to a gradual loss of their separational ability. more...

The mechanisms were studied of the adhesion of Paenibacillus polymyxa on quartz and calcite using zeta potential, contact angle, FTIR and TEM measurements. Bacterial interaction made the calcite surface more negative and the quartz surface more positive. Contact angle measurements showed that quartz surfaces became more hydrophobic and calcite surfaces more hydrophilic. FTIR results showed that bacteria grown in the presence of quartz produced more surface proteins, while in the presence of calcite more surface polysaccharides were produced. The TEM study showed that a slime layer surrounded cells grown in Bromfield medium without minerals, whereas the calcite-grown cells were surrounded by a well-structured capsule consisting of polysaccharides and the quartz-grown cells exhibited neither a capsule nor a slime layer on their surfaces. Flotation and flocculation studies showed that both bacterial cells and their metabolites enhanced the flocculation of calcite, whereas similar biotreatments promoted the dispersion of quartz. Studies with Thiobacillus ferroxidans also showed marked differences in its effect on flotation of sulphide minerals such as sphalerite and galena. The selective effects of bacterial treatments are potentially useful in the development of environmentally benign and efficient bioprocessing technologies to extract low-grade valuable minerals in a cost-effective way., The mechanisms were studied of the adhesion of Paenibacillus polymyxa on quartz and calcite using zeta potential, contact angle, FTIR and TEM measurements. Bacterial interaction made the calcite surface more negative and the quartz surface more positive. Contact angle measurements showed that quartz surfaces became more hydrophobic and calcite surfaces more hydrophilic. FTIR results showed that bacteria grown in the presence of quartz produced more surface proteins, while in the presence of calcite more surface polysaccharides were produced. The TEM study showed that a slime layer surrounded cells grown in Bromfield medium without minerals, whereas the calcite-grown cells were surrounded by a well-structured capsule consisting of polysaccharides and the quartz-grown cells exhibited neither a capsule nor a slime layer on their surfaces. Flotation and flocculation studies showed that both bacterial cells and their metabolites enhanced the flocculation of calcite, whereas similar biotreatments promoted the dispersion of quartz. Studies with Thiobacillus ferroxidans also showed marked differences in its effect on flotation of sulphide minerals such as sphalerite and galena. The selective effects of bacterial treatments are potentially useful in the development of environmentally benign and efficient bioprocessing technologies to extract low-grade valuable minerals in a cost-effective way. more...

A number of biological leaching processes are available: Thiobacillus ferrooxidans is used to oxidise a variety of sulphide ores, fungi can degrade bauxite and clays, and soil bacteria and fungi can solubilise phosphates. Bacterial conditioning with T. ferrooxidans can also affect the flotation behaviour of sulphide minerals by significantly modifying their surfaces, allowing the separation of sphalerite from galena or pyrite from coal. Bacillus polymyxa can render quartz more hydrophobic and haematite, corundum and calcite more hydrophilic, depressing their flotation and enhancing their flocculation. Mycobacterium phlei is a useful flocculant for phosphate slimes, haematite and coal fines. Microorganisms can also be used to remove heavy metals from waste water by biosorption, bioaccumulation and bioremediation., A number of biological leaching processes are available: Thiobacillus ferrooxidans is used to oxidise a variety of sulphide ores, fungi can degrade bauxite and clays, and soil bacteria and fungi can solubilise phosphates. Bacterial conditioning with T. ferrooxidans can also affect the flotation behaviour of sulphide minerals by significantly modifying their surfaces, allowing the separation of sphalerite from galena or pyrite from coal. Bacillus polymyxa can render quartz more hydrophobic and haematite, corundum and calcite more hydrophilic, depressing their flotation and enhancing their flocculation. Mycobacterium phlei is a useful flocculant for phosphate slimes, haematite and coal fines. Microorganisms can also be used to remove heavy metals from waste water by biosorption, bioaccumulation and bioremediation. more...

Bacillus polymyxa, a heterotrophic soil bacterium indigenously associated with several ore deposits, was shown to be capable of biodegrading several organic collectors such as dodecyl amine, diamine, isopropyl xanthate and sodium oleate. The bacteria could utilise the reagents for their carbon and nitrogen requirements, growing very well and generating polysaccharides, proteins and fatty acids during metabolism. They were also able to strip adsorbed collectors from mineral surfaces. Biodegradation mechanisms, determined from studies of zeta potential, adsorption, bacterial growth and mineral surfaces, included both direct bacterial metabolism and contributions from acidic metabolites. A biological route is demonstrated for detoxifying mineral processing effluents containing residual organic reagents., Bacillus polymyxa, a heterotrophic soil bacterium indigenously associated with several ore deposits, was shown to be capable of biodegrading several organic collectors such as dodecyl amine, diamine, isopropyl xanthate and sodium oleate. The bacteria could utilise the reagents for their carbon and nitrogen requirements, growing very well and generating polysaccharides, proteins and fatty acids during metabolism. They were also able to strip adsorbed collectors from mineral surfaces. Biodegradation mechanisms, determined from studies of zeta potential, adsorption, bacterial growth and mineral surfaces, included both direct bacterial metabolism and contributions from acidic metabolites. A biological route is demonstrated for detoxifying mineral processing effluents containing residual organic reagents. more...

Discussion is presented of the role of Bacillus polymyxa in altering the surface chemistry of haematite, corundum and quartz with reference to flotation and selective flocculation. Significant surface chemical changes occurred both on the cell surfaces and on the interacted oxide minerals. After such treatment with the bacteria, quartz was rendered relatively more hydrophobic, while haematite and corundum were more hydrophilic. Biopretreatment was observed to be beneficial in the separation of silica from haematite and alumina by both selective flocculation and flotation. The possible role of bacterial adhesion and metabilites in the biobeneficiation process is illustrated., Discussion is presented of the role of Bacillus polymyxa in altering the surface chemistry of haematite, corundum and quartz with reference to flotation and selective flocculation. Significant surface chemical changes occurred both on the cell surfaces and on the interacted oxide minerals. After such treatment with the bacteria, quartz was rendered relatively more hydrophobic, while haematite and corundum were more hydrophilic. Biopretreatment was observed to be beneficial in the separation of silica from haematite and alumina by both selective flocculation and flotation. The possible role of bacterial adhesion and metabilites in the biobeneficiation process is illustrated. more...

Interaction of the Bacillus with calcite, haematite, corundum and quartz resulted in significant surface chemical changes to both cells and minerals. Cell surfaces and quartz were rendered more hydrophobic after mutual interaction, while the rest of the minerals exhibited enhanced hydrophobicity after interaction. The bacteria were also capable of dissolving calcite, haematite and corundum and biosorbing the dissolved metal ions to varying extents. An excess of polysaccharides was observed on biotreated calcite, haematite and corundum while a protein-based metabolic product predominated on quartz surfaces. The surface changes can be used for desiliconisation of calcite, iron oxide and alumina through bioflotation and bioflocculation, while bacterial processing can also be used in environmental control for settling and consolidation of mineral fines., Interaction of the Bacillus with calcite, haematite, corundum and quartz resulted in significant surface chemical changes to both cells and minerals. Cell surfaces and quartz were rendered more hydrophobic after mutual interaction, while the rest of the minerals exhibited enhanced hydrophobicity after interaction. The bacteria were also capable of dissolving calcite, haematite and corundum and biosorbing the dissolved metal ions to varying extents. An excess of polysaccharides was observed on biotreated calcite, haematite and corundum while a protein-based metabolic product predominated on quartz surfaces. The surface changes can be used for desiliconisation of calcite, iron oxide and alumina through bioflotation and bioflocculation, while bacterial processing can also be used in environmental control for settling and consolidation of mineral fines. more...