Detection of the human specific Bacteroides genetic marker provides evidence of widespread sewage contamination of stormwater in the urban environment

Human sewage contamination of surface waters is a major human health concern. We found urban stormwater systems that collect and convey runoff from impervious surfaces act as a conduit for sewage originating from breeches in sanitary sewer infrastructure. A total of 828 samples at 45 stormwater outfalls were collected over a four-year period and assessed by culture based methods, PCR, and quantitative PCR (qPCR) to test for traditional and alternative indicators of fecal pollution. All outfalls had the HF183 (human) Bacteroides genetic marker detected in at least one sample, suggesting sewage contamination is nearly ubiquitous in the urban environment. However, most outfalls were intermittently positive, ranging from detection in 11%-100% of the samples. Positive results did not correlate with seasonality, rainfall amounts, or days since previous rainfall. Approximately two-thirds of the outfalls had high (>5000 copy number, i.e. CN, per 100 ml) or moderate levels (1000-5000 CN per 100 ml) of the human Bacteroides genetic marker. Escherichia coli (E. coli) and enterococci levels did not correlate to human Bacteroides. A total of 66% of all outfall samples had standard fecal indicator levels above 10,000 CFU per 100 ml. A tiered assessment using this benchmark to identify high priority sites would have failed to flag 35% of the samples that had evidence of sewage contamination. In addition, high fecal indicators would have flagged 33% of samples as priority that had low or no evidence of sewage. Enteric virus levels in one outfall with high levels of the human Bacteroides genetic marker were similar to untreated wastewater, which illustrates stormwater can serve as a pathway for pathogen contamination. The major source of fecal pollution at four of five river sites that receive stormwater discharge appeared to be from sewage sources rather than non-human sources based on the ratios of human Bacteroides to total Bacteroides spp. This study shows the feasibility and benefits of employing molecular methods to test for alternative indicators of fecal pollution to identify sewage sources and potential health risks and for prioritization of remediation efforts.     

Multigrid methods with space–time concurrency

Computing and Visualization in Science - We consider the comparison of multigrid methods for parabolic partial differential equations that allow space–time concurrency. With current trends in...     

Selecting creep models using Bayesian methods

The development of creep prediction models has been a field of extensive research and many different models have already been proposed. This paper presents an evaluation method of the prediction quality of creep models for specific experimental data. Within the scope of this paper, the model according to Bockhold and the model according to Heidolf are examined. First, the parameters of the models are identified with respect to existing experimental data. This is done using a sampling based approach of Bayesian updating developed by Ba?ant and Chern. In extension to the method by Ba?ant and Chern, the uncertainty coming from inaccurate measurement data is taken into account in the definition of the likelihood function within the updating algorithm. The more inaccurate the measurements are, the more uncertain the estimated model parameters and model prognoses become. The identification is performed for different short- and long-term creep tests. The intension is not to validate these models intensively, but to evaluate their prognoses for the individually tested creep behavior. The results show that the identifiability of the models?? parameters is different for both models and consequently the models prognoses differ in their uncertainties. Second, the models are evaluated using two different strategies: the stochastic model selection according to MacKay, Beck and Yuen based on the Ockham factor, and a comparison of the uncertainties taking into account parameter and model uncertainties. The results of the evaluation of the creep models differ for various experimental tests. Model Heidolf is more flexible and gives a better fit to the data, however, it fails to predict reliable long-term creep deformations using only short-term measurements compared to model Bockhold. Comparing the evaluation methods, the analysis of uncertainties of the creep prognosis proofs to be more stable than the evaluation using the stochastic model selection.     

HPLC column switching technique for the clean-up of steroid samples

Summary A simple column-switching system was used for the clean-up of steroid samples. Fatty tissues were extracted as described in a previous paper [1]. The filtered and concentrated extract is injected on to a HPLC system consisting of three columns. After a front-cut between column 2 and column 3, the fraction of interest is separated on column 3. Gradient elution offers the possibility to isolate a single or multi- component fraction, which can be examined by HPTLC or another detection technique.

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HPLC-Kolonne-Umkehrtechnik fur die Reinigung von Anabolica-Proben

Zusammenfassung Ein einfaches Kolonnen-Umkehrsystem wurde fur die Reinigung von Steroid-Proben angewandt. Fettgewebe wurde, wie vorher beschrieben [1], extrahiert. Der filtrierte and konzentrierte Extrakt wurde in eine aus drei Kolonnen bestehende HPLC-Anlage injiziert. Nach Abschneiden der Front zwischen Kolonne 2 and 3 wurde die interessierende Fraktion durch die Kolonne 3 chromatographiert. Die Gradiente-Elution bietet die Möglichkeit, eine ein- oder multikomponente Fraktion zu isolieren, die durch HPTLC oder eine andere Nachweistechnik geprüft werden kann.

     

Epidemiology, clinical aspects, and biology of IDDM patients under age 40 years. Comparison of data from Antwerp with complete ascertainment with data from Belgium with 40% ascertainment. The Belgian Diabetes Registry

OBJECTIVE: To compare the incidence rate of IDDM in the age-groups 0-14 and 15-39 years in Antwerp, Belgium, and to compare demographic, clinical, and biological data from Antwerp IDDM patients with 92% ascertainment with those from a larger Belgian patient group with 40% ascertainment. RESEARCH DESIGN AND METHODS: Incident cases of IDDM were reported by physicians of the Belgian Diabetes Registry and in Antwerp by several other sources. In Antwerp, completeness of ascertainment was calculated by the capture-recapture method. Demographic and clinical data were collected by questionnaire. Blood was sampled for HLA-DQ genotyping and, in new-inset patients, for autoantibodies. RESULTS: In Antwerp, the age- and sex-standardized IDDM incidence rates were similar in both age-groups (0-14 years: 11.8/100,000; 15-39 years: 8.9/100,000). The incidence rate decreased in girls above age 15 years (6.9/100,000; P = 0.003) but not in boys (11.0/100,000). Both in Antwerp and Belgium, IDDM was diagnosed more frequently in the 15-39 years age-group (60% of all cases) than under age 15 years, with a lower prevalence of acute symptoms, ketonuria, high-risk HLA-DQ genotype, and autoantibodies against insulin, islet cells, and IA-2, but with a higher prevalence of GAD65 autoantibodies. CONCLUSIONS: In Antwerp, the incidence rate of IDDM under age 15 years is intermediately high compared with the rates in other European regions. It is similar in the 15-39 years age-group, but with a marked male predominance. Demographic, clinical, and biological data show the same age-dependent heterogeneity as the data collected nationwide, with 40% ascertainment indicating the representativeness of the latter.     

Iterative speed improvement for solving slowly varying total least squares problems

Many problems in signal processing, modal analysis, system identification, etc., give rise to an overdetermined set of linear equations AX ≈ B. Whenever both the observation matrix B and the data matrix A are inaccurate, the total least squares (TLS) method is appropriate for estimating the unknown parameters X. Since the TLS solution is deduced from only one right singular vector or, in general, a basis of the right singular subspace associated with the smallest singular values of the data [A; B], the computational speed can be improved by only calculating those desired base vectors. If a priori information is available (e.g. the TLS solution at a previous time step when slowly varying sets of equations must be solved at each time instant), iterative methods are appropriate to compute those base vectors. It is shown in this paper that inverse iteration is the most efficient iterative technique for solving generic TLS problems of known rank.Two algorithms for subspace inverse iteration are presented. Their convergence properties and applicability in solving TLS problems are analysed. Based on the convergence rate and the operation counts in each iteration step, these iterative algorithms are compared in efficiency with the direct computation methods—classical TLS and partial TLS. In particular, the efficiency of these methods is illustrated in a practical real life problem, namely multiple input estimation of frequency response functions.     

Periodic reactive flow simulation: Proof of concept for steam cracking coils

Streamwise periodic boundary conditions (SPBCs) have been successful in reducing the computational cost of simulating high aspect ratio processes. Extending beyond the classic assumptions of constant property flows, a novel approach incorporating non‐equilibrium kinetics was developed and implemented for the simulation of an industrial propane steam cracker. Comparison with non‐periodic benchmarks provided validation as relative errors on the main product yields were consistently below 1% for different reactor configurations. A further order‐of‐magnitude reduction of the radial errors on product concentrations was obtained via an intuitive correction method based on the concept of local fluid age. The computational speedup achieved through application of SPBCs was a factor 16–250 compared to the non‐periodic simulations. The presented methodology thus serves as a quick screening tool for the development of novel reactor designs and unlocks the potential for using more elaborate kinetic models or a more fundamental approach toward turbulence modeling. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1715–1726, 2017     

A note on `Efficient numerically stabilized rank-one eigenstructureupdating' [and reply]

In the above-named paper, R.D. DeGroat and R.A. Roberts (see ibid., vol.38, no.2, p.301-16, Feb. 1990) developed a reorthogonalization scheme for stabilizing eigenstructure updating algorithms. The commenters show that only part of this scheme, namely the renormalization, is essential for the stability, so that a cheaper scheme, with roughly half as many computations, can perform equally well. DeGroat addresses two points raised by the commenters' work