Impact of microaeration bioreactor on dissolved sulfide and methane removal from real UASB effluent for sewage treatment.

Two bioreactors were investigated as an alternative for the post-treatment of effluent from an upflow anaerobic sludge blanket (UASB) reactor treating domestic sewage, aiming at dissolved sulfide and methane removal. The bioreactors (R-control and R-air) were operated at different hydraulic retention times (HRT; 6 and 3 h) with or without aeration. Large sulfide and methane removal efficiencies were achieved by the microaerated reactor at HRT of 6 h. At this HRT, sulfide removal efficiencies were equal to 61% and 79%, and methane removal efficiencies were 31% and 55% for R-control and R-air, respectively. At an HRT of 3 h, sulfide removal efficiencies were 22% (R-control) and 33% (R-air) and methane removal did not occur. The complete oxidation of sulfide, with sulfate formation, prevailed in both phases and bioreactors. However, elemental sulfur formation was more predominant at an HRT of 6 h than at an HRT of 3 h. Taken together, the results show that post-treatment improved the anaerobic effluent quality in terms of chemical oxygen demand and solids removal. However, ammoniacal nitrogen was not removed due to either the low concentration of air provided or the absence of microorganisms involved in the nitrogen cycle.

Evaluation of EPS extraction protocols from anaerobic sludge for gel-based proteomic studies.

Despite the importance of anaerobic sludge extracellular polymeric substances (EPSs), their characterization is limited to information regarding their chemical classes and molecular size. This work explores the possibility of using proteomic techniques to study the proteins present in this matrix. Thus, this paper compares eight EPS extraction methods regarding extraction yield, protein/carbohydrate ratio, size distribution profile and suitability to sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses. Despite the differences found in quantification and size exclusion chromatography assays, the band profile found for all methods was very similar. Considering the band pattern, extraction time and background level, heating method followed by ammonium sulfate precipitation proved to be the most appropriate method for gel-based analyses of anaerobic sludge EPS proteins.

Local vibrational dynamics of hematite (α-Fe2O3) studied by extended x-ray absorption fine structure and molecular dynamics.

The local vibrational dynamics of hematite (α-Fe2O3) has been investigated by temperature-dependent extended x-ray absorption fine structure spectroscopy and molecular dynamics simulations. The local dynamics of both the short and long nearest-neighbor Fe-O distances has been singled out, i.e., their local thermal expansion and the parallel and perpendicular mean-square relative atomic displacements have been determined, obtaining a partial agreement with molecular dynamics. No evidence of the Morin transition has been observed. More importantly, the strong anisotropy of relative thermal vibrations found for the short Fe-O distance has been related to its negative thermal expansion. The differences between the local dynamics of short and long Fe-O distances are discussed in terms of projection and correlation of atomic motion. As a result, we can conclude that the short Fe-O bond is stiffer to stretching and softer to bending than the long Fe-O bond.

Allergy and acute leukaemia in children with Down syndrome: a population study. Report from the Mexican inter-institutional group for the identification of the causes of childhood leukaemia.

BACKGROUND: Allergies have been described as protective factors against the development of childhood acute leukaemia (AL). Our objective was to investigate the associations between allergy history and the development of AL and acute lymphoblastic leukaemia (ALL) in children with Down syndrome (DS). METHODS: A case-control study was performed in Mexico City. The cases (n=97) were diagnosed at nine public hospitals, and the controls (n=222) were recruited at institutions for children with DS. Odds ratios (OR) were calculated. RESULTS: Asthma was positively associated with AL development (OR=4.18; 95% confidence interval (CI): 1.47-11.87), whereas skin allergies were negatively associated (OR=0.42; 95% CI: 0.20-0.91). CONCLUSION: Our findings suggest that allergies and AL in children with DS share biological and immune mechanisms. To our knowledge, this is the first study reporting associations between allergies and AL in children with DS.

Degradation of a model azo dye in submerged anaerobic membrane bioreactor (SAMBR) operated with powdered activated carbon (PAC).

This work investigated the anaerobic degradation of the model azo dye Remazol Yellow Gold RNL in an upflow anaerobic sludge blanket reactor (UASB) and two submerged anaerobic membrane (SAMBR) bioreactors, one of which (SAMBR-1) was operated with powdered activated carbon (PAC) in its interior. The reactors were operated at 35 °C with a hydraulic retention time of 24 h in three operational phases, aimed to assess the effect of external sources of carbon (glucose) or redox mediator (yeast extract) on the removal or color and organic matter. The results showed that removal efficiencies of COD (73-94%) and color (90-94%) were higher for SAMBR-1 when compared to SAMBR-2 (operated without PAC) and UASB reactors. In addition, the presence of PAC in SAMBR-1 increased reactor stability, thereby leading to a lower accumulation of volatile fatty acids (VFA). The microfiltration membrane was responsible for an additional removal of ~50% of soluble residual COD in the form of VFA, thus improving permeate quality. On its turn, PAC exhibited the ability to adsorb byproducts (aromatic amines) of azo dye degradation as well as to act as source of immobilized redox mediator (quinone groups on its surface), thereby enhancing color removal.

Psychosocial predictors of binge-drinking residual harm in adolescence and young adulthood: Findings from the Australian Temperament Project.

AIMS: We examine the extent to which adolescent and young adult psychosocial factors are associated with variation in the experience of common types of harm (e.g., injuries, violence, sexual regrets) with respect to binge-drinking frequency - termed residual harm. METHODS: Data were from the Australian Temperament Project, a population-based cohort study that has followed a sample of young Australians from infancy to adulthood since 1983. The current sample comprised 1,081 (565 women). Residual harm was operationalised by saving residuals from models regressing number of alcohol harms onto binge-drinking frequency at each of 5 waves, two in adolescence (15-16 and 17-18 years) and three in young adulthood (19-20, 23-24, and 27-28 years). Psychosocial factors (mental health, social skills, quality of parent and peer relationships) were assessed prior to binge drinking in early adolescence (13-14 years) and then again in young adulthood (19-20 years). RESULTS: Adolescent predictors of decreased residual harm were lower depressive symptoms, and higher cooperation, self-control, and peer and parent attachment. Young adult predictors of decreased residual harm were lower depressive, anxiety, and stress symptoms and peer and parent negative appraisal, and higher responsibility, and peer and parent emotional support. Associations were evident in males and females, although the strength of some associations diminished with age. CONCLUSIONS: Adolescents and young adults with better mental health, social skills, and relationship quality experienced less harm with respect to their binge-drinking frequency. Future research should examine the potential of investment in strength-based interventions for young people.

Exploring a causal model in observational cohort data: The role of parents and peers in shaping substance use trajectories.

AIMS: To explore the process of applying counterfactual thinking in examining causal determinants of substance use trajectories in observational cohort data. Specifically, we examine the extent to which quality of the parent-adolescent relationship and affiliations with deviant peers are causally related to trajectories of alcohol, tobacco, and cannabis use across adolescence and into young adulthood. METHODS: Data were drawn from the Australian Temperament Project, a population-based cohort study that has followed a sample of young Australians from infancy to adulthood since 1983. Parent-adolescent relationship quality and deviant peer affiliations were assessed at age 13-14 years. Latent curve models were fitted for past month alcohol, tobacco, and cannabis use (n = 1590) from age 15-16 to 27-28 years (5 waves). Confounding factors were selected in line with the counterfactual framework. RESULTS: Following confounder adjustment, higher quality parent-adolescent relationships were associated with lower baseline cannabis use, but not alcohol or tobacco use trajectories. In contrast, affiliations with deviant peers were associated with higher baseline binge drinking, tobacco, and cannabis use, and an earlier peak in the cannabis use trajectory. CONCLUSIONS: Despite careful application of the counterfactual framework, interpretation of associations as causal is not without limitations. Nevertheless, findings suggested causal effects of both parent-adolescent relationships and deviant peer affiliations on the trajectory of substance use. Causal effects were more pervasive (i.e., more substance types) and protracted for deviant peer affiliations. The exploration of causal relationships in observational cohort data is encouraged, when relevant limitations are transparently acknowledged.

Breastfeeding and early infection in the aetiology of childhood leukaemia in Down syndrome.

BACKGROUND: For a child to develop acute leukaemia (AL), environmental exposure may not be sufficient: interaction with a susceptibility factor to the disease, such as Down syndrome (DS), may also be necessary. We assessed whether breastfeeding and early infection were associated with the risk of developing AL in children with DS. METHODS: Children with DS in Mexico City, and either with or without AL, were the cases (N=57) and controls (N=218), respectively. Population was divided in children with AL and with acute lymphoblastic leukaemia (ALL) and also in children < or = 6 and >6 years old. RESULTS: Breastfeeding and early infections showed moderate (but not significant) association for AL, whereas hospitalisation by infection during the first year of life increased the risk: odds ratios (confidence interval 95%) were 0.84 (0.43-1.61), 1.70 (0.82-3.52); and 3.57 (1.59-8.05), respectively. A similar result was obtained when only ALL was analysed. CONCLUSION: We found that breastfeeding was a protective factor for developing AL and ALL, and during the first year of life, infections requiring hospitalisation were related to a risk for developing the disease in those children with DS >6 years of age. These data do not support the Greaves's hypothesis of early infection being protective for developing ALL.

On the neglecting of higher-order cumulants in EXAFS data analysis.

The cumulant expansion is one of the most powerful and useful methods for EXAFS data analysis, in which the higher-order cumulants allow to consider deviations from a simple Gaussian distribution. In this work, analytical expressions have been derived to show the effects of neglecting higher-order cumulants in EXAFS analysis by the ratio method. The errors in the best-fitting procedure owing to the omission of the higher-order cumulants, as well as of the coordination number, can be determined.

A GDP/GTP exchange factor involved in linking a spatial landmark to cell polarity.

In both animal and yeast cells, signaling pathways involving small guanosine triphosphatases (GTPases) regulate polarized organization of the actin cytoskeleton. In the budding yeast Saccharomyces cerevisiae, the Ras-like GTPase Bud1/Rsr1 and its guanosine 5'-diphosphate (GDP)/guanosine 5'-triphosphate (GTP) exchange factor Bud5 are involved in the selection of a specific site for growth, thus determining cell polarity. We found that Bud5 is localized at the cell division site and the presumptive bud site. Its localization is dependent on potential cellular landmarks, such as Bud3 and Axl2/Bud10 in haploid cells and Bud8 and Bud9 in diploid cells. Bud5 also physically interacts with Axl2/Bud10, a transmembrane glycoprotein, suggesting that a receptor-like transmembrane protein recruits a GDP/GTP exchange factor to connect an intrinsic spatial signal to oriented cell growth.

A comparison of longitudinal modelling approaches: Alcohol and cannabis use from adolescence to young adulthood.

BACKGROUND: Modelling trajectories of substance use over time is complex and requires judicious choices from a number of modelling approaches. In this study we examine the relative strengths and weakness of latent curve models (LCM), growth mixture modelling (GMM), and latent class growth analysis (LCGA). DESIGN: Data were drawn from the Australian Temperament Project, a 36-year-old community-based longitudinal study that has followed a sample of young Australians from infancy to adulthood across 16 waves of follow-up since 1983. Models were fitted on past month alcohol use (n = 1468) and cannabis use (n = 549) across six waves of data collected from age 13-14 to 27-28 years. FINDINGS: Of the three model types, GMMs were the best fit. However, these models were limited given the variance of numerous growth parameters had to be constrained to zero. Additionally, both the GMM and LCGA solutions had low entropy. The negative binomial LCMs provided a relatively well-fitting solution with fewer drawbacks in terms of growth parameter estimation and entropy issues. In all cases, model fit was enhanced when using a negative binomial distribution. CONCLUSIONS: Substance use researchers would benefit from adopting a complimentary framework by exploring both LCMs and mixture approaches, in light of the relative strengths and weaknesses as identified. Additionally, the distribution of data should inform modelling decisions.

Strong inflammatory response and Th1-polarization profile in children with acute lymphoblastic leukemia without apparent infection.

Children with acute lymphoblastic leukemia (ALL) often present fever. Febrile states are usually associated with infectious processes that generate an inflammatory response involving various molecules, including cytokines. However, an inflammatory response may also occur in the absence of infection. We hypothesized that the levels of inflammatory cytokines are increased in children with ALL without apparent infection. The serum levels of 13 cytokines in 99 patients with ALL and 48 non-oncological patients without apparent infection were measured using multiplex analyte profiling technology (Luminex®). The concentration of circulating pro-inflammatory cytokines associated with fever was similar between patients with ALL and fever at diagnosis and those without fever. The levels of tumor necrosis factor α, interleukin (IL)-6, IL-8, monocyte chemoattractant protein-1 (MCP-1) and IL-10 were higher in patients with ALL vs. the control group (P<0.05). Moreover, the levels of the T helper 1 (interferon­Î³ and IL-12) cytokines were higher in patients with ALL vs. the control group. Transforming growth factor ß was lower in patients with ALL vs. the control group (P<0.05). The levels of IL-1ß, IL-2, IL-4, IL-13, and IL-17 were similar in the two groups. Our results indicate that the circulating levels of seven of the important studied cytokines are elevated in patients with newly diagnosed ALL without apparent infection, reflecting a strong and deregulated inflammatory state in this disease, with a Th1-polarization profile.

A NMR study of the ionization of fatty acids, fatty amines and N-acylamino acids incorporated in phosphatidylcholine vesicles.

The ionization of fatty acids, fatty amines and N-acylamino acids incorporated in phosphatidylcholine single-walled vesicles has been measured. The guest molecules have been specifically enriched with 13C and titrated by using NMR spectroscopy. The apparent pKa of fatty acids in phosphatidylcholine bilayers if 7.2-7.4 and those of fatty amines are approx. 9.5. These pKa values depend on many different parameters related to the structure of the lipid/solution interface, to the composition of the aqueous medium and to the localization of the ionizable groups. A special sensitivity to the ionic strength and to the surface charge has been found. A positive surface charge decreases the pKa value whereas a negative one increases it, the total range of variation being 2.5-3 units. In a qualitative macroscopic interpretation, it is proposed that pKa is essentially determined by the low polarity of the lipidic matrix.

Exploring the folding pathways of annexin I, a multidomain protein. II. Hierarchy in domain folding propensities may govern the folding process.

In the context of exploring the relationship between sequence and folding pathways, the multi-domain proteins of the annexin family constitute very attractive models. They are constituted of four approximately 70-residue domains, named D1 to D4, with identical topologies but only limited sequence homology of approximately 30%. The domains are organized in a pseudochiral circular arrangement. Here, we report on the folding propensity of the D1 domain of annexin I obtained from overexpression in Escherichia coli. Unlike the D2 domain, which is only partially folded, the isolated D1 domain exhibits autonomous refolding in pure aqueous solution. Similarly, the D3 domain and D2-D3 module were obtained from expression in E. coli but were found to be largely unfolded. No conclusion could be drawn for the D4 domain because it was not possible to extract it from the bacterial inclusion bodies. The data allow us to propose a plausible scenario for the annexin I folding. This working model states that firstly the D1 domain folds, and the D2 and D3 domains remain partly unfolded, facilitating the docking of the D4 domain to the D1 domain. In a second step, the D1 and D4 domains dock, and D4 may fold if already not folded. The final step starts with the stabilization of the D1-D4 module. This stabilization is crucial for allowing the non-native local interactions inside the still partially unfolded D2 domain to switch to the native long-range interactions involving D4. This switch allows the complete folding of D2 and D3. The model proposes a sequential and hierarchical process for the folding of annexin I and emphasizes the role of both native framework and non-native structures in the process.

Exploring the folding pathways of annexin I, a multidomain protein. I. non-native structures stabilize the partially folded state of the isolated domain 2 of annexin I.

Proteins of the annexin family constitute very attractive models because of their four approximately 70 residue domains, D1 to D4, exhibiting an identical topology comprising five helix segments with only a limited sequence homology of approximately 30%. We focus on the isolated D2 domain, which is only partially folded. A detailed analysis of this equilibrium partially folded state in aqueous solution and micellar solution using 15N-1H multidimensional NMR is presented. Comparison of the residual structure of the entire domain with that of shorter fragments indicates the presence of long-range transient hydrophobic interactions that slightly stabilize the secondary structure elements. The unfolded domain tends to behave as a four-helix, rather than as a five-helix domain. The ensemble of residual structures comprises: (i) a set of native structures consisting of three regions with large helix populations, in rather sharp correspondence with A, B and E helices, and a small helix population in the second part of the C helix; (ii) a set of non-native local structures corresponding to turn-like structures stabilized by several side-chain to side-chain interactions and helix-disruptive side-chains to backbone interactions. Remarkably, residues involved in these local non-native interactions are also involved, in the native structure, in structurally important non-local interactions. During the folding process of annexin I, the local non-native interactions have to switch to native long-range interactions. This structural switch reveals the existence of a sequence-encoded regulation of the folding pathways and kinetics, and emphasizes the key role of the non-native local structures in this regulation.

Role of Different Solvents on the Purification of As-Synthesized Nano-Ce(1-x)Gd(x)O(2-d) Powders.

Ceria and rare earth-doped ceria powders have important applications in catalysis, gas sensoring, and electronics. Even if many authors report different methods for the synthesis of nano-sized doped-ceria only few of them give information about the necessary washing processes for the powder purification. The organics adsorbed on the as-synthesized particles surface strongly affect, in fact, the properties of the powder. In this work, CeO2 and Ce(1-x)Gd(x)O(2-d) (x = 0.10, 0.20, 0.30) solid solutions were produced by polyol microwave assisted method. The amount of synthesis residues adsorbed on the as-synthesized powders was firstly evaluated. The purification ability of different solvents on the as-synthesized Ce0.80Gd0.20O190 was, then, accurately studied in order to obtain a clean powder without the need of any thermal treatments. The study shows that water purification allows to reduce the amount of the residues of synthesis leading to the production of nano-particles with a mono-dispersed distribution of dimensions.

Monte-Carlo simulations of clinically realistic respiratory gated (18)F-FDG PET: application to lesion detectability and volume measurements.

In PET/CT thoracic imaging, respiratory motion reduces image quality. A solution consists in performing respiratory gated PET acquisitions. The aim of this study was to generate clinically realistic Monte-Carlo respiratory PET data, obtained using the 4D-NCAT numerical phantom and the GATE simulation tool, to assess the impact of respiratory motion and respiratory-motion compensation in PET on lesion detection and volume measurement. To obtain reconstructed images as close as possible to those obtained in clinical conditions, a particular attention was paid to apply to the simulated data the same correction and reconstruction processes as those applied to real clinical data. The simulations required 140,000h (CPU) generating 1.5 To of data (98 respiratory gated and 49 ungated scans). Calibration phantom and patient reconstructed images from the simulated data were visually and quantitatively very similar to those obtained in clinical studies. The lesion detectability was higher when the better trade-off between lesion movement limitation (compared to ungated acquisitions) and image statistic preservation is considered (respiratory cycle sampling in 3 frames). We then compared the lesion volumes measured on conventional PET acquisitions versus respiratory gated acquisitions, using an automatic segmentation method and a 40%-threshold approach. A time consuming initial manual exclusion of noisy structures needed with the 40%-threshold was not necessary when the automatic method was used. The lesion detectability along with the accuracy of tumor volume estimates was largely improved with the gated compared to ungated PET images.

A conformational equilibrium in a protein fragment caused by two consecutive capping boxes: 1H-, 13C-NMR, and mutational analysis.

The conformational properties of an 18 residues peptide spanning the entire sequence, L1KTPA5QFDAD10ELRAA15MKG, of the first helix (A-helix) of domain 2 of annexin I, were thoroughly investigated. This fragment exhibits several singular features, and in particular, two successive potential capping boxes, T3xxQ6 and D8xxE11. The former corresponds to the native hydrogen bond network stabilizing the alpha helix N-terminus in the protein; the latter is a non-native capping box able to break the helix at residue D8, and is observed in the domain 2 partially folded state. Using 2D-NMR techniques, we showed that two main populations of conformers coexist in aqueous solution. The first corresponds to a single helix extending from T3 to K17. The second corresponds to a broken helix at residue Ds. Four mutants, T3A, F7A, D8A, and E11A, were designed to further analyze the role of key amino acids in the equilibrium between the two ensembles of conformers. The sensitivity of NMR parameters to account for the variations in the populations of conformers was evaluated for each peptide. Our data show the delta13Calpha chemical shift to be the most relevant parameter. We used it to estimate the population ratio in the various peptides between the two main ensembles of conformers, the full helix and the broken helix. For the WT, E11A, and F7A peptides, these ratios are respectively 35/65, 60/40, 60/40. Our results were compared to the data obtained from helix/coil transition algorithms.

Investigating the conformational coupling between the transmembrane and cytoplasmic domains of a single-spanning membrane protein. A 1H-NMR study.

PMP1 is a 38-residue single-spanning membrane protein whose C-terminal cytoplasmic domain, Y25-F38, is highly positively charged. The conformational coupling between the transmembrane span and the cytoplasmic domain of PMP1 was investigated from 1H-nuclear magnetic resonance data of two synthetic fragments: F9-F38, i.e. 80% of the whole sequence, and Y25-F38, the isolated cytoplasmic domain. Highly disordered in aqueous solution, the Y25-F38 peptide adopts a well-defined conformation in the presence of dodecylphosphocholine micelles. Compared with the long PMP1 fragment, this structure exhibits both native and non-native elements. Our results make it possible to assess the influence of a hydrophobic anchor on the intrinsic conformational propensity of a cytoplasmic domain.

Structure of human annexin I: comparison of homology modelling and crystallographic experiment.

A model of domain II of annexin I has been built by homology modelling using an annexin V crystal structure as a template. The method used is based on that of Summers and Karplus (J Mol Biol (1989) 210, 785-811) and involves the calculation of torsion-angle rotational energy maps to position side chains. The RMS deviation of the backbone heavy atoms between the model and a crystal structure of annexin I is 1.1 A. Similarities and differences in the experimental and model-derived side-chain rotameric conformations and hydrogen-bonding interactions are examined. It is found that whereas many of the side chains are well positioned some of those placed using the 'entropy argument' in which the broadest of the available minima are preferred, are erroneous. The domain is subjected to molecular dynamics simulation in explicit solvent. The simulations are found to 'correct' some of the side-chain rotamer positions that were poorly placed in the homology modelling. Considerable helix instability is seen in the simulations, consistent with the requirement of domain interactions for the structural integrity of the protein.