Early detection of thermoacoustic instabilities in a cryogenic rocket thrust chamber using combustion noise features and machine learning.

We present a data-driven method for the early detection of thermoacoustic instabilities. Recurrence quantification analysis is used to calculate characteristic combustion features from short-length time series of dynamic pressure sensor data. Features like recurrence rate are used to train support vector machines to detect the onset of instability a few hundred milliseconds in advance. The performance of the proposed method is investigated on experimental data from a representative LOX/H 2 research thrust chamber. In most cases, the method is able to timely predict two types of thermoacoustic instabilities on test data not used for training. The results are compared with state-of-the-art early warning indicators.

Impact of Long-Term Organic and Mineral Fertilization on Rhizosphere Metabolites, Root-Microbial Interactions and Plant Health of Lettuce.

Fertilization management can affect plant performance and soil microbiota, involving still poorly understood rhizosphere interactions. We hypothesized that fertilization practice exerts specific effects on rhizodeposition with consequences for recruitment of rhizosphere microbiota and plant performance. To address this hypothesis, we conducted a minirhizotron experiment using lettuce as model plant and field soils with contrasting properties from two long-term field experiments (HUB-LTE: loamy sand, DOK-LTE: silty loam) with organic and mineral fertilization history. Increased relative abundance of plant-beneficial arbuscular mycorrhizal fungi and fungal pathotrophs were characteristic of the rhizospheres in the organically managed soils (HU-org; BIODYN2). Accordingly, defense-related genes were systemically expressed in shoot tissues of the respective plants. As a site-specific effect, high relative occurrence of the fungal lettuce pathogen Olpidium sp. (76-90%) was recorded in the rhizosphere, both under long-term organic and mineral fertilization at the DOK-LTE site, likely supporting Olpidium infection due to a lower water drainage potential compared to the sandy HUB-LTE soils. However, plant growth depressions and Olpidium infection were exclusively recorded in the BIODYN2 soil with organic fertilization history. This was associated with a drastic (87-97%) reduction in rhizosphere abundance of potentially plant-beneficial microbiota (Pseudomonadaceae, Mortierella elongata) and reduced concentrations of the antifungal root exudate benzoate, known to be increased in presence of Pseudomonas spp. In contrast, high relative abundance of Pseudomonadaceae (Gammaproteobacteria) in the rhizosphere of plants grown in soils with long-term mineral fertilization (61-74%) coincided with high rhizosphere concentrations of chemotactic dicarboxylates (succinate, malate) and a high C (sugar)/N (amino acid) ratio, known to support the growth of Gammaproteobacteria. This was related with generally lower systemic expression of plant defense genes as compared with organic fertilization history. Our results suggest a complex network of belowground interactions among root exudates, site-specific factors and rhizosphere microbiota, modulating the impact of fertilization management with consequences for plant health and performance.

Pay for performance - motivation to succeed in Advanced Trauma Life Support courses - a question of background or funding?

Objective: To correlate students' performance with their professional background and motivation to take part in Advanced Trauma Life Support (ATLS) courses. We base our analysis on the self-determination theory that differentiates intrinsic (ambition to perform by individual itself) from extrinsic motivation (incentive by external stimuli). Design: We present a non-blinded, monocentric, non-randomized descriptive study of 376 students taking part in an ATLS course at one course site in Germany. Part of a two-day ATLS course are two written tests; we correlate test scores with background information provided by the students in a questionnaire of 13 items (age, sex, adress, board certification, specialty, subspecialty, position, hospital level of care, hospital operator and hospital participation in trauma network, motivation, funding source, condition of funding). Setting: The students were recuited at the BG Trauma Center Ludwigshafen (Germany), a large 528-bed trauma center and one of 13 ATLS course sites in Germany. Participants: 449 ATLS course students taking part in ATLS courses at the above-mentioned course site from February 2009 to May 2010 were sent a questionnaire asking for their background. All 449 course students were eligible to participate. 376 (83.7%) questionnaires were returned, pre- and post-test results of all students aquired and included into our calculations. 312 (83%) were male and 64 (17%) female. The majority (59.3%) of recruited students came from trauma surgery, 21.8% from anesthesiology, 8% from general surgery, 4% from abdominal surgery, 0.5% from vascular or thoracic surgery each and 5.9% from other specialties. Results: Neither age, sex, subspecialty, hospital level of care, hospital operator, or hospital participation in trauma network played a role with respect to motivation or test results. The high degree of intrinsic motivation of consultants (92.3%) had no impact on their test results. Anesthesiologists were higher motivated (75.6% intrinsically motivated) in contrast to all surgical colleagues (63.6%), which showed significant differences in the pre- (89.8% vs. 85.3%, p=0.03) but not the post-test. Of all 13.6% students who were self-payers, 94.1% were intrinsically motivated; the 86.2% whose course fee was accounted for were less likely to be intrinsically motivated (63.9%). Sponsoring however did not have a negative impact on test results. Conditional funding (sponsored only on passing both tests) was detrimental to motivation: 0% of these individuals were intrinsically motivated and they scored significantly lower (82.5%) than all other students in the post-test (86.9%, p=0.002). Overall, intrinsically motivated students overtopped extrinsically motivated students in the post-test (88.0% vs. 83.4%, p<0.001). Conclusions: ATLS course participation is not compulsory for medical doctors in Germany. Intrinsic motivation to take part in these courses is a key prerequisite to increase performance, irrespective of the background of the students. Intrinsically motivated students are ready to invest into their education and vice versa. Conditional funding (course fee only sponsored on passing the course) evokes no intrinsic motivation at all and causes worse results.

Detection of argan oil adulteration with vegetable oils by high-performance liquid chromatography-evaporative light scattering detection.

Triacylglycerol profiles were selected as indicator of adulteration of argan oils to carry out a rapid screening of samples for the evaluation of authenticity. Triacylglycerols were separated by high-performance liquid chromatography-evaporative light scattering detection. Different peak area ratios were defined to sensitively detect adulteration of argan oil with vegetable oils such as sunflower, soy bean, and olive oil up to the level of 5%. Based on four reference argan oils, mean limits of detection and quantitation were calculated to approximately 0.4% and 1.3%, respectively. Additionally, 19 more argan oil reference samples were analysed by high-performance liquid chromatography-refractive index detection, resulting in highly comparative results. The overall strategy demonstrated a good applicability in practise, and hence a high potential to be transferred to routine laboratories.

Biosynthesis of the vitamin E compound delta-tocotrienol in recombinant Escherichia coli cells.

The biosynthesis of natural products in a fast growing and easy to manipulate heterologous host system, such as Escherichia coli, is of increasing interest in biotechnology. This procedure allows the investigation of complex natural product biosynthesis and facilitates the engineering of pathways. Here we describe the cloning and the heterologous expression of tocochromanol (vitamin E) biosynthesis genes in E. coli. Tocochromanols are synthesized solely in photosynthetic organisms (cyanobacteria, algae, and higher green plants). For recombinant tocochromanol biosynthesis, the genes encoding hydroxyphenylpyruvate dioxygenase (hpd), geranylgeranylpyrophosphate synthase (crtE), geranylgeranylpyrophosphate reductase (ggh), homogentisate phytyltransferase (hpt), and tocopherol-cyclase (cyc) were cloned in a stepwise fashion and expressed in E. coli. Recombinant E. coli cells were cultivated and analyzed for tocochromanol compounds and their biosynthesis precursors. The expression of only hpd from Pseudomonas putida or crtE from Pantoea ananatis resulted in the accumulation of 336 mg L(-1) homogentisate and 84 microg L(-1) geranylgeranylpyrophosphate in E. coli cultures. Simultaneous expression of hpd, crtE, and hpt from Synechocystis sp. under the control of single tac-promoter resulted in the production of methyl-6-geranylgeranyl-benzoquinol (67.9 microg g(-1)). Additional expression of the tocopherol cyclase gene vte1 from Arabidopsis thaliana resulted in the novel formation of a vitamin E compound-delta-tocotrienol (15 microg g(-1))-in E. coli.

Stable carbon isotope ratios of POPs--a tracer that can lead to the origins of pollution.

An elemental analyzer in combination with stable isotope ratio mass spectrometry (EA-IRMS) was used to demonstrate that two samples of the chloropesticide Melipax discovered in two countries varied only by 0.1 per thousand in their delta 13C values. Gas chromatography interfaced to a stable isotope mass spectrometer (GC-IRMS) was used to study the delta 13C values of individual congeners in two technical polybrominated diphenyl ether products, i. e. DE-71 and DE-79, at three different concentration levels. Injections of 4 microg and 5.2 microg of DE-71 and DE-79 were most suited for the determinations. In both products, the delta 13C values were usually the more negative the higher the degree of bromination was. The delta 13C values of three hexabromo isomers BDE 138, BDE 153, and BDE 154 could be determined in both products. In all cases the delta 13C values of the three hexaBDEs were more depleted in delta 13C in the higher brominated technical octabromo diphenyl ether DE-79.

Production of medium-chain-length hydroxyalkanoic acids from Pseudomonas putida in pH stat.

Pseudomonas putida GP01 cells that had accumulated medium-chain-length polyhydroxyalkanoates (PHA(MCL)) secreted 3-hydroxyoctanoate and 3-hydroxyhexanoate when incubated in alkaline buffers. The release of acids strongly decreased the pH resulting in less efficient secretion of 3HA(MCL) at neutral pH. To increase the yield of secreted MCL-hydroxyalkanoates, experiments at constant pH in a pH stat apparatus were performed. High acid releasing rates were recorded for the wild type GP01 at pH 9.2 (0.60 mmol acid h(-1) g(-1) cellular dry weight [cdw]). At more alkaline constant pH values (pH 9.3-11), the initial acid secretion rates were even higher but rapidly decreased by time. When acid secretion of PHA depolymerase mutant GPo500 was tested (pH 9.2), considerably lower rates compared to wild type were recorded (0.18 mmol acid h(-1) g(-1) cdw). Determination of dissolved oxygen during acid release indicated different respiratoric activity in wild type (low) and mutant (high). Acid release of mutant, but not of the wild type, could be enhanced by aeration. Determination of PHA content of cells after alkaline incubation showed that the wild type had lost most of its accumulated PHA, whereas the PHA content of the depolymerase mutant was not significantly reduced. Considerable amounts of 3HA(MCL) were secreted by the wild type, but only little 3HA(MCL) were found for the depolymerase mutant. In summary, 3HA(MCL) can be more efficiently produced at constant high pH than by incubation without pH control. High PHA depolymerase activity enabled the wild type to compensate for the high external pH by secretion of PHA hydrolysis products, whereas production of protons at aerobic conditions presumably was responsible for the major portion of the observed acid releasing rates in the depolymerase mutant.

Identification of genes and proteins necessary for catabolism of acyclic terpenes and leucine/isovalerate in Pseudomonas aeruginosa.

Geranyl-coenzyme A (CoA)-carboxylase (GCase; AtuC/AtuF) and methylcrotonyl-CoA-carboxylase (MCase; LiuB/LiuD) are characteristic enzymes of the catabolic pathway of acyclic terpenes (citronellol and geraniol) and of saturated methyl-branched compounds, such as leucine or isovalerate, respectively. Proteins encoded by two gene clusters (atuABCDEFGH and liuRABCDE) of Pseudomonas aeruginosa PAO1 were essential for acyclic terpene utilization (Atu) and for leucine and isovalerate utilization (Liu), respectively, as revealed by phenotype analysis of 10 insertion mutants, two-dimensional gel electrophoresis, determination of GCase and MCase activities, and Western blot analysis of wild-type and mutant strains. Analysis of the genome sequences of other pseudomonads (P. putida KT2440 and P. fluorescens Pf-5) revealed candidate genes for Liu proteins for both species and candidate genes for Atu proteins in P. fluorescens. This result concurred with the finding that P. fluorescens, but not P. putida, could grow on acyclic terpenes (citronellol and citronellate), while both species were able to utilize leucine and isovalerate. A regulatory gene, atuR, was identified upstream of atuABCDEFGH and negatively regulated expression of the atu gene cluster.

Establishing a chromium-reactor design for measuring delta2H values of solid polyhalogenated compounds using direct elemental analysis and stable isotope ratio mass spectrometry.

2H/1H isotope ratios of polyhalogenated compounds were determined by elemental analysis and isotope ratio mass spectrometry (EA-IRMS). Initial measurements with standard EA-IRMS equipment, which used high-temperature pyrolysis to convert the organic compounds into hydrogen, did not achieve significant signals for polychlorinated pesticides and related compounds, presumably due to the formation of HCl instead of hydrogen. To reverse this problematic reaction, a chromium reactor was incorporated into the element analyzer system, which scavenged Cl, forming chromium chloride and releasing hydrogen again in the form of H2. The optimized system therefore allowed the delta2H values of polyhalogenated compounds to be determined. A quality assurance program was developed based on several parameters. (i) Each compound was analyzed using a sequence of five injections, where the first measurement was discarded. (ii) Recovery of H (when calculated relative to acetanilide) had to be >90% for all replicates in a sequence. (iii) All delta-values within a sequence had to vary by less than 10/1000. (iv) Results had to be reproducible on another day with a different sample scheme. Once this reproducibility had been established, variabilities in the delta2H values of organohalogen standards were investigated using the technique. The highest delta2H value of +75/1000 was found for o,p'-DDD, whereas the strongest depletion in deuterium was found for Melipax (-181/1000). The most important results for comparable compounds were as follows. DDT-related compounds gave delta2H values of between +59 and +75/1000 (technical DDT, o,p'- and p,p'-DDD) or in the range of approximately -1/1000, indicative of the different sources/methods of producing this compound. Four HCH isomers from the same supplier showed relatively similar hydrogen isotope distributions, whereas two lindane (gamma-HCH) standards from other sources had 39/1000 less deuterium. This difference is likely due to different purification steps during the isolation of pure lindane from the technical HCH mixture. An even greater difference was observed between the delta2H values of Toxaphene (US product dating from 1978) and Melipax (product from the former East Germany, dating from 1979), which gave delta2H values of -101/1000 and -181/1000, respectively, meaning that both products were easily distinguished via delta2H-IRMS. Fractioning of hydrogen isotopes in the atmospheric water cycle was suggested as one reason for the different values. In this theory, the water (which had different delta2H values depending on where it was taken from) was incorporated during the biosynthesis of camphene, which is the natural product used to produce both products. These results indicate that hydrogen isotope-specific analysis can be a valuable tool for tracing the origins of a compound in certain cases.

Baseline isotopic data of polyhalogenated compounds.

The delta2H- and delta13C-values of polyhalogenated compounds were determined by EA-IRMS. Most of the compounds were related to the chloropesticides DDT and its metabolites, hexachlorocyclohexanes, and toxaphene, as well as several polybrominated compounds such as bromophenols and -anisoles. delta2H-values ranged between -235 per thousand and +75 per thousand whereas delta13C-values were found in the range -22 per thousand to -38 per thousand. No correlation between delta2H- and delta13C-values could be identified. Comparative analysis clarified that bromophenols and the corresponding bromoanisoles may vary in their isotopic distribution. 2H NMR was used to quantify abundances of 2H isotopomers. Quantification of isotopomers of 2,4-dibromophenol and 2,4-dibromoanisole proved that both compounds from different suppliers do not originate from the same source. Differences in the delta2H-values of two toxaphene products were further investigated by the synthesis of products of different degree of chlorination from camphene. It was shown that the delta13C-values remained mostly unaltered as was expected since no carbon is lost in this procedure. However, the reaction products became enriched in 2H with increasing degree of chlorination. Different delta2H-values of the starting material will also impact the delta2H-values of the chlorination products.

Heme-dependent rubber oxygenase RoxA of Xanthomonas sp. cleaves the carbon backbone of poly(cis-1,4-Isoprene) by a dioxygenase mechanism.

Oxidative cleavage of poly(cis-1,4-isoprene) by rubber oxygenase RoxA purified from Xanthomonas sp. was investigated in the presence of different combinations of (16)O(2), (18)O(2), H(2)(16)O, and H(2)(18)O. 12-oxo-4,8-dimethyl-trideca-4,8-diene-1-al (ODTD; m/z 236) was the main cleavage product in the absence of (18)O-compounds. Incorporation of one (18)O atom in ODTD was found if the cleavage reaction was performed in the presence of (18)O(2) and H(2)(16)O. Incubation of poly(cis-1,4-isoprene) (with RoxA) or of isolated unlabeled ODTD (without RoxA) with H(2)(18)O in the presence of (16)O(2) indicated that the carbonyl oxygen atoms of ODTD significantly exchanged with oxygen atoms derived from water. The isotope exchange was avoided by simultaneous enzymatic reduction of both carbonyl functions of ODTD to the corresponding dialcohol (12-hydroxy-4,8-dimethyl-trideca-4,8-diene-1-ol (HDTD; m/z 240) during RoxA-mediated in vitro cleavage of poly(cis-1,4-isoprene). In the presence of (18)O(2), H(2)(16)O, and alcohol dehydrogenase/NADH, incorporation of two atoms of (18)O into the reduced metabolite HDTD was found (m/z 244), revealing that RoxA cleaves rubber by a dioxygenase mechanism. Based on the labeling results and the presence of two hemes in RoxA, a model of the enzymatic cleavage mechanism of poly(cis-1,4-isoprene) is proposed.

Congener-specific concentrations and carbon stable isotope ratios (delta13C) of two technical toxaphene products (Toxaphene and Melipax).

In this study we compared the contribution of individual congeners and the ratios of stable carbon isotopes of two technical toxaphene products. The former US-American product Toxaphene was from 1978 and the East-German product Melipax from 1979. Both technical products showed the known complexity in GC/ECD measurements. Contributions of 24 peaks to each of the technical products were determined by gas chromatography in combination high resolution electron capture negative ion mass spectrometry (GC/ECNI-HRMS). The percentages of the compounds studied in the technical mixtures ranged from approximately 0.05% to approximately 2.5% but showed some individual differences. 2,2,5,5,8,9,9,10,10-nonachlorobornane (B9-1025 or P-62) was identified as a major congener in both mixtures. 2-Endo,3-exo,5-endo,6-exo,8,8,10,10-octachlorobornane (B8-1413 or P26) and 2-endo,3-exo,5-endo,6-exo,8,8,9,10,10-nonachlorobornane (B9-1679 or P-50) were found at similar concentration in both technical products. Identical amounts of Melipax or Toxaphene were combusted to CO2 in an element analyzer and their delta13C values were determined relative to the international standard Vienna PeeDee belemnite (VPDB). The mean delta13C values of both products varied by 2.8% (determined at two different locations) which is roughly one order of magnitude more than the precision obtained in repetitive analyses of the individual products. Thus, both investigated products could be unequivocally distinguished by stable isotope ratio mass spectrometry (IRMS). IRMS analyses may thus be a suitable tool for tracing back toxaphene residues in environmental and food samples to the one or both of the products.