Variations of common riverine contaminants in reservoir sediments.

Organic molecules in reservoir sediments can be used as tracers of contaminant inputs into rivers. Vertical variations in the molecular records can be ascribed to pre-depositional alteration within the water column, or in situ post-depositional alteration. We report the molecular stratigraphy of four common riverine contaminant groups in sediment of the largest reservoir on the Danube River, the Iron Gate I Reservoir. Sediments were rapidly deposited, with little variation in texture and, as revealed by analytical pyrolysis, in the concentration and composition of natural sedimentary organic matter. However, a detailed molecular inspection did reveal differences in distribution and organic carbon (OC)-normalized concentrations of contaminants. The OC-normalized concentrations of nonylphenol increased by one order of magnitude with depth down the 70 cm sediment core. There is a strong correlation between sediment depth and the ratio of nonylphenol to its precursor (nonylphenol monoethoxylate). This indicated that nonylphenol was produced in situ. While the relative proportions of C10-C14 linear alkylbenzenes remained constant with increasing depth, they exhibited variations in isomer distribution. These variations, which are due to different degrees of degradation, appear to have occurred within the water column prior to sedimentation of suspended solids. The distribution of 40 polycyclic aromatic hydrocarbons revealed origins from both pyrogenic and petrogenic sources. The differences in their compositions were not depth-related, but rather were associated with variations in the sorption capacities of texturally different sediments. Perylene showed slightly higher concentrations at greater depths, while the OC-normalized concentration of retene systematically increased with sediment depth. This is consistent with formation of retene and perylene via very early diagenetic transformation. The presence of petroleum biomarkers indicated minor contamination by fossil fuels.

Multiple Acetabular Revisions in THA - Poor Outcome Despite Maximum Effort.

A consecutive series of 52 acetabular revisions was evaluated retrospectively. Inclusion criteria for all patients were at least one former exchange of the acetabular component. Reconstruction was performed with reliable techniques and implants other than extensively porous coated device (e.g. tantalum). The mean follow up was 5.63 (0.01-14.05) years. Cumulative survival at 14.05 years with removal of the acetabular component due to aseptic loosening or the worst case criterion (removal of the acetabular component for any cause and/or lost to follow-up) as the end point was 66.38 (95 % C.-I.: 47.80-84.96) % and 58.42 (95 % C.-I.: 41.01-75.83) %, respectively. The cumulative survival rate with mechanical failure of the acetabular reconstruction as the endpoint was significantly lower in patients with two or more previous revisions in comparison to those with only one former procedure (log rank test: p=0,0112 respectively). The mean Merle d'Aubignée-score improved from 7.3 (0-14) preoperatively to 10.6 (0-17) points at latest follow up examination.Survival of acetabular reconstructions with common techniques and implants is decreasing with the number of previous revisions. This may cause major concerns with regard to the rising number of patients needing repeated revisions. Maximizing durability of primary THA, precise preoperative planning as well as improved techniques and implants for revision may decrease this problem in the long term.

Variations in concentrations and compositions of polycyclic aromatic hydrocarbons (PAHs) in coals related to the coal rank and origin.

The release of unburnt coal particles and associated polycyclic aromatic hydrocarbons (PAHs) may cause adverse impacts on the environment. This study assessed variations in the concentration and composition of PAHs in a set of fifty coal samples from eleven coal basins worldwide. The maximum PAH concentrations at high volatile bituminous rank were recorded in samples from a single basin. Considering the entire sample set, the highest PAH concentrations were in fact found outside of this rank range, suggesting that the maceral composition and thus the coal's origin also influenced PAH concentrations. The examination of the PAH compositions revealed that alkylated 2-3 ring PAHs remain dominant compounds irrespective of coal rank or origin. Multivariate analysis based on PAH and maceral content, bulk and maturity parameters allowed the recognition of seven groups with different rank and origin within the coal sample set.

Natural, anthropogenic and fossil organic matter in river sediments and suspended particulate matter: a multi-molecular marker approach.

Different classes of organic matter (OM) have been systematically investigated in sediments and suspended particulate matter (SPM) along the Danube River in order to understand causes of compositional changes. Analytical pyrolysis revealed the dominance of natural organic matter (NOM) in most of the samples. The predominance of aquatic biomass is evident mainly from the abundance of organonitrogen compounds and phenol distributions. As the river enters a forested gorge, the terrestrial component of the NOM in sediments is more significant. This is reflected in abundant methoxyphenols and a very high carbon preference index. SPM sample from a tributary shows a unique geochemical signature. It contains abundant carboxylic acids, amines, isoprenoids in the pyrolyzate, and is dominated by phytol and 24-methyl-cholesta-5,24(28)-dien-3ß-ol in the extract, produced by a diatom bloom. Wax esters with a relatively high proportion of short, methyl-branched alkyl-chains appear together with abundant phytadienes and n-C(17) alkane in some samples, suggesting a microbial origin. Anthropogenic OM from runoff and atmospheric deposition was evident from a minor input of polycyclic aromatic hydrocarbons (PAHs) originating from mixed combustion sources. Multivariate analysis using PAH data led us to define simple molecular ratios to distinguish the PAH composition in sand and silty sediments. The newly defined ratios are the alkylated phenanthrenes and anthracenes ratio (APA; C(1)-C(3)/C(0)-C(3) phenanthrenes and anthracenes) and the PAH ring number ratio (RN; 5-6 ring parent PAHs/all parent PAHs). This demonstrates that alkylated, as well as 5-6 ring PAHs are better preserved in the finer than in coarser grained sediments. A ubiquitous, but minor input of petroleum-related contamination with a uniform composition was evident in all samples as revealed by the analysis of petroleum biomarkers. This study demonstrates that the investigation of different classes of riverine OM requires a detailed molecular analysis, applying a series of analytical techniques and adequate statistical data treatment.

Cerumen composition by flash pyrolysis-gas chromatography/mass spectrometry.

OBJECTIVE: To assess the chemical composition of cerumen by flash pyrolysis-gas chromatography/mass spectrometry. STUDY DESIGN: Collected earwax specimens were fractionated into residue and supernatant by means of deoxycholate. This natural bile acid produces significantly better disintegration of earwax in vitro than do presently available ceruminolytic preparations, and also has demonstrated excellent clinical results in vivo to date. PATIENTS: The sample for analysis was obtained from a patient with clinical earwax impaction. RESULTS: The supernatant is composed of simple aromatic hydrocarbons, C5-C17 straight-chain hydrocarbons, a complex mixture of compounds tentatively identified as diterpenoids, and steroids, in particular cholesterol. The residue, on the other hand, produced simple aromatic compounds (including benzenes, phenols, and benzonitriles), C5-C25 straight-chain hydrocarbons, greater relative quantities of nitrogen compounds and phenol, and lesser importance of the (tentatively identified) diterpenoids. CONCLUSIONS: Through the use of the detergent deoxycholate, squalene and a tentatively identified diterpenoid were revealed to be present in a free, unbound state, whereas some steroids and hydrocarbons appeared to be bound to a macromolecular structure by nitrogen linkages or other bonds. Additionally, this study reintroduces detergents as a viable method of earwax removal, specifically the bile acids.

Molecular composition of the louse sheath.

Flash pyrolysis-gas chromatography/mass spectrometry was used to assess the chemical composition of the head louse's nit sheath. The pyrolyzate of the female insect's secretions, which form a cement-like cylinder holding the egg onto the hair, is dominated by amino acid derivatives and fatty acids. No chitin-specific compounds were detected in the sheath. These results, contrary to previous reports, show that the polymeric complex of the sheath is composed of proteinaceous moieties, possibly cross-linked to aliphatic components. This study constitutes the first chemical characterization of the pyrolysis products of insect (louse) glue and unequivocally confirms that louse sheaths are not chitinous, as suggested by earlier histochemical studies. Development of agents that might loosen nits from the hair shaft is dependent on research that addresses the chemical composition of the nit sheath.