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Sample records for robust niti-zro2-peg spme

  1. Application of robust NiTi-ZrO2-PEG SPME fiber in the determination of haloanisoles in cork stopper samples

    International Nuclear Information System (INIS)

    Budziak, Dilma; Martendal, Edmar; Carasek, Eduardo

    2008-01-01

    In this study, a novel solid-phase microextraction (SPME) fiber obtained using sol-gel technology was applied in the determination of off-flavor compounds (2,4,6-trichloroanisole (TCA), 2,4,6-tribromoanisole (TBA) and pentachloroanisole (PCA)) present in cork stopper samples. A NiTi alloy previously electrodeposited with zirconium oxide was used as the substrate for a poly(ethylene glycol) (PEG) coating. Scanning electronic microscopy showed good uniformity of the coating and allowed the coating thickness to be estimated as around 17 μm. The optimization of the main parameters influencing the extraction efficiency, such as cork sample mass, sodium chloride mass, extraction temperature and extraction time were optimized using a full factorial design, followed by a Doehlert design. The optimum conditions were: 20 min of extraction at 70 deg. C using 60 mg of the cork sample and 10 mL of water saturated with sodium chloride in a 20 mL amber vial with constant magnetic stirring. Satisfactory detection limits between 2.5 and 5.1 ng g -1 were obtained, as well as good precision (R.S.D. in the range of 5.8-12.0%). Recovery tests were performed on three different cork samples, and values between 83 and 119% were obtained. The proposed SPME fiber was compared with commercially available fibers and good results were achieved, demonstrating its applicability

  2. Phytoscreening with SPME: Variability Analysis.

    Science.gov (United States)

    Limmer, Matt A; Burken, Joel G

    2015-01-01

    Phytoscreening has been demonstrated at a variety of sites over the past 15 years as a low-impact, sustainable tool in delineation of shallow groundwater contaminated with chlorinated solvents. Collection of tree cores is rapid and straightforward, but low concentrations in tree tissues requires sensitive analytics. Solid-phase microextraction (SPME) is amenable to the complex matrix while allowing for solvent-less extraction. Accurate quantification requires the absence of competitive sorption, examined here both in laboratory experiments and through comprehensive examination of field data. Analysis of approximately 2,000 trees at numerous field sites also allowed testing of the tree genus and diameter effects on measured tree contaminant concentrations. Collectively, while these variables were found to significantly affect site-adjusted perchloroethylene (PCE) concentrations, the explanatory power of these effects was small (adjusted R(2) = 0.031). 90th quantile chemical concentrations in trees were significantly reduced by increasing Henry's constant and increasing hydrophobicity. Analysis of replicate tree core data showed no correlation between replicate relative standard deviation (RSD) and wood type or tree diameter, with an overall median RSD of 30%. Collectively, these findings indicate SPME is an appropriate technique for sampling and analyzing chlorinated solvents in wood and that phytoscreening is robust against changes in tree type and diameter.

  3. Robust

    DEFF Research Database (Denmark)

    2017-01-01

    Robust – Reflections on Resilient Architecture’, is a scientific publication following the conference of the same name in November of 2017. Researches and PhD-Fellows, associated with the Masters programme: Cultural Heritage, Transformation and Restoration (Transformation), at The Royal Danish...

  4. Differentiation of wines according to grape variety and geographical origin based on volatiles profiling using SPME-MS and SPME-GC/MS methods.

    Science.gov (United States)

    Ziółkowska, Angelika; Wąsowicz, Erwin; Jeleń, Henryk H

    2016-12-15

    Among methods to detect wine adulteration, profiling volatiles is one with a great potential regarding robustness, analysis time and abundance of information for subsequent data treatment. Volatile fraction fingerprinting by solid-phase microextraction with direct analysis by mass spectrometry without compounds separation (SPME-MS) was used for differentiation of white as well as red wines. The aim was to differentiate between varieties used for wine production and to also differentiate wines by country of origin. The results obtained were compared to SPME-GC/MS analysis in which compounds were resolved by gas chromatography. For both approaches the same type of statistical procedure was used to compare samples: principal component analysis (PCA) followed by linear discriminant analysis (LDA). White wines (38) and red wines (41) representing different grape varieties and various regions of origin were analysed. SPME-MS proved to be advantageous in use due to better discrimination and higher sample throughput. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Uptake of Radionuclide Metals by SPME Fibers

    International Nuclear Information System (INIS)

    Duff, M; S Crump, S; Robert Ray, R; Keisha Martin, K; Donna Beals, D

    2006-08-01

    The Federal Bureau of Investigation (FBI) Laboratory currently does not have on site facilities for handling radioactive evidentiary materials and there are no established FBI methods or procedures for decontaminating high explosive (HE) and fire debris (FD) evidence while maintaining evidentiary value. One experimental method for the isolation of HE and FD residue involves using solid phase microextraction or SPME fibers to remove residue of interest. Due to their high affinity for organics, SPME fibers should have little affinity for most metals. However, no studies have measured the affinity of radionuclides for SPME fibers. The focus of this research was to examine the affinity of dissolved radionuclide ( 239/240 Pu, 238 U, 237 Np, 85 Sr, 133 Ba, 137 Cs, 60 Co and 226 Ra) and stable radionuclide surrogate metals (Sr, Co, Ir, Re, Ni, Ba, Cs, Nb, Zr, Ru, and Nd) for SPME fibers at the exposure conditions that favor the uptake of HE and FD residues. Our results from radiochemical and mass spectrometric analyses indicate these metals have little measurable affinity for these SPME fibers during conditions that are conducive to HE and FD residue uptake with subsequent analysis by liquid or gas phase chromatography with mass spectrometric detection

  6. Method for covering a spme fibre with carbon nanotubes and resulting spme fibre

    OpenAIRE

    Bertrán, Enric; Jover Comas, Eric; García Céspedes, Jordi; Bayona Termens, Josep María

    2010-01-01

    [EN] The invention relates to a method for covering solid phase microextraction (SPME) fibres with carbon nanotubes (CNT), comprising the following operations: (i) depositing a layer of a metal material on the SPME fibre; (ii) applying a heat treatment in order to form catalytic metal nanoparticles in a reducing atmosphere; and (iii) applying carbon using chemical deposition techniques, thereby forming CNT on top ofthe metal nanoparticles. The invention also relates to a fibre obtain...

  7. Recent Developments and Applications of Solid Phase Microextraction (SPME in Food and Environmental Analysis—A Review

    Directory of Open Access Journals (Sweden)

    Sybille Merkle

    2015-06-01

    Full Text Available Solid-phase microextraction (SPME is a simple, sensitive, rapid and solvent-free technique for the extraction of analytes from gaseous, liquid and solid samples and takes a leading position among microextraction methods. Application of SPME in sample preparation has been increasing continuously over the last decade. It is most often used as an automatized fiber injection system coupled to chromatographic separation modules for the extraction of volatile and semivolatile organic compounds and also allows for the trace analysis of compounds in complex matrices. Since SPME was first introduced in the early 1990s, several modifications have been made to adapt the procedure to specific application requirements. More robust fiber assemblies and coatings with higher extraction efficiencies, selectivity and stability have been commercialized. Automation and on-line coupling to analytical instruments have been achieved in many applications and new derivatization strategies as well as improved calibration procedures have been developed to overcome existing limitations regarding quantitation. Furthermore, devices using tubes, needles or tips for extraction instead of a fiber have been designed. In the field of food analysis, SPME has been most often applied to fruit/vegetables, fats/oils, wine, meat products, dairy and beverages whereas environmental applications focus on the analysis of air, water, soil and sediment samples.

  8. A comparison of sample preparation methods for extracting volatile organic compounds (VOCs) from equine faeces using HS-SPME.

    Science.gov (United States)

    Hough, Rachael; Archer, Debra; Probert, Christopher

    2018-01-01

    Disturbance to the hindgut microbiota can be detrimental to equine health. Metabolomics provides a robust approach to studying the functional aspect of hindgut microorganisms. Sample preparation is an important step towards achieving optimal results in the later stages of analysis. The preparation of samples is unique depending on the technique employed and the sample matrix to be analysed. Gas chromatography mass spectrometry (GCMS) is one of the most widely used platforms for the study of metabolomics and until now an optimised method has not been developed for equine faeces. To compare a sample preparation method for extracting volatile organic compounds (VOCs) from equine faeces. Volatile organic compounds were determined by headspace solid phase microextraction gas chromatography mass spectrometry (HS-SPME-GCMS). Factors investigated were the mass of equine faeces, type of SPME fibre coating, vial volume and storage conditions. The resultant method was unique to those developed for other species. Aliquots of 1000 or 2000 mg in 10 ml or 20 ml SPME headspace were optimal. From those tested, the extraction of VOCs should ideally be performed using a divinylbenzene-carboxen-polydimethysiloxane (DVB-CAR-PDMS) SPME fibre. Storage of faeces for up to 12 months at - 80 °C shared a greater percentage of VOCs with a fresh sample than the equivalent stored at - 20 °C. An optimised method for extracting VOCs from equine faeces using HS-SPME-GCMS has been developed and will act as a standard to enable comparisons between studies. This work has also highlighted storage conditions as an important factor to consider in experimental design for faecal metabolomics studies.

  9. Fast quantitation of opioid isomers in human plasma by differential mobility spectrometry/mass spectrometry via SPME/open-port probe sampling interface.

    Science.gov (United States)

    Liu, Chang; Gómez-Ríos, Germán Augusto; Schneider, Bradley B; Le Blanc, J C Yves; Reyes-Garcés, Nathaly; Arnold, Don W; Covey, Thomas R; Pawliszyn, Janusz

    2017-10-23

    Mass spectrometry (MS) based quantitative approaches typically require a thorough sample clean-up and a decent chromatographic step in order to achieve needed figures of merit. However, in most cases, such processes are not optimal for urgent assessments and high-throughput determinations. The direct coupling of solid phase microextraction (SPME) to MS has shown great potential to shorten the total sample analysis time of complex matrices, as well as to diminish potential matrix effects and instrument contamination. In this study, we demonstrate the use of the open-port probe (OPP) as a direct and robust sampling interface to couple biocompatible-SPME (Bio-SPME) fibres to MS for the rapid quantitation of opioid isomers (i.e. codeine and hydrocodone) in human plasma. In place of chromatography, a differential mobility spectrometry (DMS) device was implemented to provide the essential selectivity required to quantify these constitutional isomers. Taking advantage of the simplified sample preparation process based on Bio-SPME and the fast separation with DMS-MS coupling via OPP, a high-throughput assay (10-15 s per sample) with limits of detection in the sub-ng/mL range was developed. Succinctly, we demonstrated that by tuning adequate ion mobility separation conditions, SPME-OPP-MS can be employed to quantify non-resolved compounds or those otherwise hindered by co-extracted isobaric interferences without further need of coupling to other separation platforms. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Sampling atmospheric pesticides with SPME: Laboratory developments and field study

    International Nuclear Information System (INIS)

    Wang Junxia; Tuduri, Ludovic; Mercury, Maud; Millet, Maurice; Briand, Olivier; Montury, Michel

    2009-01-01

    To estimate the atmospheric exposure of the greenhouse workers to pesticides, solid phase microextraction (SPME) was used under non-equilibrium conditions. Using Fick's law of diffusion, the concentrations of pesticides in the greenhouse can be calculated using pre-determined sampling rates (SRs). Thus the sampling rates (SRs) of two modes of SPME in the lab and in the field were determined and compared. The SRs for six pesticides in the lab were 20.4-48.3 mL min -1 for the exposed fiber and 0.166-0.929 mL min -1 for the retracted fiber. In field sampling, two pesticides, dichlorvos and cyprodinil were detected with exposed SPME. SR with exposed SPME for dichlorvos in the field (32.4 mL min -1 ) was consistent with that in the lab (34.5 mL min -1 ). SR for dichlorvos in the field (32.4 mL min -1 ) was consistent with that in the lab (34.5 mL min -1 ). The trends of temporal concentration and the inhalation exposure were also obtained. - SPME was proved to be a powerful and simple tool for determining pesticides' atmospheric concentration

  11. Optimization of Biochemical Screening Methods for Volatile and Unstable Sesquiterpenoids Using HS-SPME-GC-MS

    Directory of Open Access Journals (Sweden)

    Trine Bundgaard Andersen

    2015-06-01

    Full Text Available HS-SPME-GC-MS has been suggested as a fast and robust analytical platform for the product characterization of sesquiterpene synthases. The choice of fiber and injection temperature can have a significant effect on the observed product profile, due to the chemical rearrangements that can occur on the fiber material. Here we present a systematic study on the effects of fiber choice and injection port temperature on the observed sesquiterpenoid profile of four sesquiterpene synthases expressed in Nicotiana benthamiana. We found that the absorbent material PDMS was much less likely to support acid-induced rearrangement of sesquiterpenoids when compared to the adsorbent materials PDMS/DVB, PDMS/CAR, and PDMS/CAR/DVB. Furthermore, utilizing an injection port temperature at 160 °C almost eliminated the inherent thermal instability of germacrene sesquiterpenoids. Thus, for fast screening of sesquiterpene synthases, the results suggest that PDMS fibers and an injection temperature of 160 °C provide a fast and reproducible HS-SPME GC-MS method when using H2 as carrier gas.

  12. Further research on the photo-SPME of triclosan

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Prado, Lucia; Llompart, Maria; Lores, Marta; Fernandez-Alvarez, Maria; Garcia-Jares, Carmen; Cela, Rafael [Universidad de Santiago de Compostela, Departamento de Quimica Analitica, Nutricion y Bromatologia. Facultad de Quimica, Instituto de Investigacion y Analisis Alimentario, Santiago de Compostela (Spain)

    2006-04-15

    In this study the photoinduced degradation of triclosan has been investigated by photo-solid-phase microextraction (photo-SPME). In photo-SPME, photodegradation is carried out on the SPME fibre containing the target compound. Triclosan was extracted from aqueous solutions by use of polydimethylsiloxane SPME fibres and these were subsequently exposed to UV irradiation (power 8 W, wavelength 254 nm) for different times (from 2 to 60 min). The photodegradation kinetics of triclosan were investigated, the photoproducts generated were tentatively identified, and the photochemical behaviour of these products was studied by use of this on-fibre approach followed by gas chromatographic-mass spectrometric analysis. Eight photoproducts were tentatively identified, including chlorinated phenols, chlorohydroxydiphenyl ethers, 2,8-dichlorodibenzo-p-dioxin, and a possible dichlorodibenzodioxin isomer or dichlorohydroxydibenzofuran. The main photodegradation mechanisms were postulated and photodegradation pathways proposed. The effect of pH on triclosan degradation and on triclosan-to-dioxin conversion was also investigated. Triclosan degradation occurred, and generation of 2,8-dichlorodibenzo-p-dioxin was confirmed, throughout the pH range studied (from 3 to 9). (orig.)

  13. Role of nanoparticles in analytical solid phase microextraction (SPME)

    NARCIS (Netherlands)

    Zielinska, K.; Leeuwen, van H.P.

    2013-01-01

    Solid phase microextraction (SPME) is commonly used to measure the free concentration of fairly hydrophobic substances in aqueous media on the basis of their partitioning between sample solution and a solid phase. Here we study the role of nanoparticles that may sorb the analyte in the sample

  14. Microextração por fase sólida SPME, Solid Phase Micro-Extration

    Directory of Open Access Journals (Sweden)

    Antonio Luiz Pires Valente

    2000-08-01

    Full Text Available Fundamental aspects of Solid Phase Micro-Extraction (SPME are discussed in the present paper. The application of SPME as a microtechnique of sample preparation for gas chromatographic analysis is considered and related to existing theoretical models. Both research prototypes and commercial SPME devices are considered.

  15. A home-made SPME fiber coating for Arson Analysis

    International Nuclear Information System (INIS)

    Umi Khairul Ahmad; Abdul Rahim Yacob; Selvaraju, Geetha

    2008-01-01

    A number of adsorbents are available commercially as coatings for SPME fibers but some analytical methodologies might demand specific properties for the extraction of selected compounds, special coatings that have particular volume and a selectivity towards particular analytes. This paper presents a simple, fast, effective and environmental friendly methodology for the determination of accelerants in arson samples using headspace solid-phase micro extraction coupled to gas chromatography. A new fiber prepared by sol-gel method, containing 1:1 molar ratio of octyltriethoxysilane (C 8 -TEOS): methyltrimethoxysilane (MTMOS) was employed in this technique. The efficiency of the new fiber coating prepared by sol-gel technology for the determination of accelerants was compared to that of commercial PDMS/ DVB fibers. Poly dimethylsiloxane divinylbenzene (PDMS/ DVB) is the most common fiber coating for the extraction of hydrocarbon compounds. Compared with commercial PDMS/ DVB fiber, the new homemade fiber exhibited higher extraction capability and good selectivity for accelerants. The homemade fiber was also applied for the simulated arson samples. The home-made SPME adsorbent was shown to be a good alternative to commercially available fiber for the determination of accelerants in arson cases. (author)

  16. HS-SPME-GC-MS Analysis of onion (Allium cepa L. and shallot (Allium ascalonicum L.

    Directory of Open Access Journals (Sweden)

    D’Auria, M.

    2017-06-01

    Full Text Available The volatile organic compounds of onion and shallot were determined via HS-SPME-GC-MS. The main components were dipropyldisulphide and allylpropyldisulphide. Thiopropanal S-oxide were detected only in onion volatiles. In shallot is interesting the presence of 2-methyl-2-pentenal, a compound with an intense fruity aroma, that can characterize the different aroma between onion and shallot. The SPME-GC-MS analysis of shallot after absorption on the SPME fiber at 50°C showed the presence of new compounds, whose structures have been discussed.

  17. Nuevos desarrollos metodológicos en SPME

    OpenAIRE

    Ríos Acevedo, John Jairo

    2016-01-01

    La Microextracción en fase sólida (SPME) ha experimentado un rápido desarrollo desde su introducción hace más de 20 años teniendo un gran impacto sobre las prácticas de muestreo y preparación de muestra en áreas como análisis químico, bioanálisis, los alimentos y las ciencias ambientales. Sin embargo, en otras áreas como análisis clínico, ciencias farmacéuticas y médicas, se espera un crecimiento en sus aplicaciones. El objetivo fundamental de la presente investigación ha sido la implementaci...

  18. Development and Validation of a SPME-GC-MS Method for In situ Passive Sampling of Root Volatiles from Glasshouse-Grown Broccoli Plants Undergoing Below-Ground Herbivory by Larvae of Cabbage Root Fly, Delia radicum L.

    Science.gov (United States)

    Deasy, William; Shepherd, Tom; Alexander, Colin J; Birch, A Nicholas E; Evans, K Andrew

    2016-11-01

    Research on plant root chemical ecology has benefited greatly from recent developments in analytical chemistry. Numerous reports document techniques for sampling root volatiles, although only a limited number describe in situ collection. To demonstrate a new method for non-invasive in situ passive sampling using solid phase micro extraction (SPME), from the immediate vicinity of growing roots. SPME fibres inserted into polyfluorotetrafluoroethylene (PTFE) sampling tubes located in situ which were either perforated, covered with stainless steel mesh or with microporous PTFE tubing, were used for non-invasive sub-surface sampling of root volatiles from glasshouse-grown broccoli. Sampling methods were compared with above surface headspace collection using Tenax TA. The roots were either mechanically damaged or infested with Delia radicum larvae. Principal component analysis (PCA) was used to investigate the effect of damage on the composition of volatiles released by broccoli roots. Analyses by gas chromatography-mass spectrometry (GC-MS) with SPME and automated thermal desorption (ATD) confirmed that sulphur compounds, showing characteristic temporal emission patterns, were the principal volatiles released by roots following insect larval damage. Use of SPME with in situ perforated PTFE sampling tubes was the most robust method for out-of-lab sampling. This study describes a new method for non-invasive passive sampling of volatiles in situ from intact and insect damaged roots using SPME. The method is highly suitable for remote sampling and has potential for wide application in chemical ecology/root/soil research. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  19. Determination of fatty acids and volatile compounds in fruits of rosehip(Rosa L.) species by HS-SPME/GC-MS and Im-SPME/GC-MS techniques

    OpenAIRE

    MURATHAN, ZEHRA TUĞBA; ZARIFIKHOSROSHAHI, MOZGAN; KAFKAS, NESİBE EBRU

    2016-01-01

    In this study, we aimed to compare fatty acid and volatile compound compositions of four rosehip species, namely Rosa pimpinellifolia, R. Villosa, R. Canina, and R. Dumalis, by gas chromatography with flame ionization detector (GC/FID) and headspace and immersion solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME/GC-MS and Im-SPME/GC-MS) techniques. The total lipid contents in fruits of the rosehip species varied from 5.83% (R. Villosa) to 7.84% (R. Dumalis). A total of...

  20. Modified application of HS-SPME for quality evaluation of essential oil plant materials.

    Science.gov (United States)

    Dawidowicz, Andrzej L; Szewczyk, Joanna; Dybowski, Michal P

    2016-01-01

    The main limitation in the standard application of head space analysis employing solid phase microextraction (HS-SPME) for the evaluation of plants as sources of essential oils (EOs) are different quantitative relations of EO components from those obtained by direct analysis of EO which was got in the steam distillation (SD) process from the same plant (EO/SD). The results presented in the paper for thyme, mint, sage, basil, savory, and marjoram prove that the quantitative relations of EO components established by HS-SPME procedure and direct analysis of EO/SD are similar when the plant material in the HS-SPME process is replaced by its suspension in oil of the same physicochemical character as that of SPME fiber coating. The observed differences in the thyme EO composition estimated by both procedures are insignificant (F(exp)SPME procedure proposed in this paper substantially shortens the evaluation time of plant material quality and thus may improve the efficiency of analytical laboratories. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Application of solid phase micro extraction (SPME) in profiling hydrocarbons in oil spill cases

    International Nuclear Information System (INIS)

    Zuraidah Abdullah Munir; Norashikin Saim; Nurul Huda Mamat Ghani

    2008-01-01

    In environmental forensic, it is extremely important to have a fast and reliable method in identifying sources of spilled oil and petroleum products. In this study, solid phase micro extraction (SPME) method coupled to gas chromatography-mass spectrometry was developed for the analysis of hydrocarbons in diesel and petroleum contaminated soil samples. Optimization of SPME parameters such as extraction time, extraction temperature and desorption time, was performed using 100-μm poly dimethylsiloxane (PDMS) fiber. These parameters were studied at three levels by means of a central composite experimental design and the optimum experimental conditions were determined using response surface method. The developed SPME method was applied to determine the profiles of hydrocarbons in several oil contaminated soil sample. The SPME method was also used to study the effects of weathering on the profiles of hydrocarbons in unleaded gasoline, diesel and kerosene contaminated soil samples. After several days, significant losses of the lighter hydrocarbons were observed compared to the heavier ones. From these data, SPME method can be used to differentiate possible candidate sources in oil spill cases. (author)

  2. JV Task 92 - Alcoa/Retec SFE and SPME

    Energy Technology Data Exchange (ETDEWEB)

    Steven Hawthorne

    2009-02-15

    This report summarizes the work performed by the Energy & Environmental Research Center (EERC) under the U.S. Department of Energy Jointly Sponsored Research Program JV Task 92, which is a continuation of JV9. Successful studies performed in 1999 through the end of 2008 demonstrated the potential for using selective supercritical fluid extraction (SFE) and a solid-phase microextraction (SPME) method for measuring sediment pore water polycyclic aromatic hydrocarbons (PAHs) to mimic the bioavailability of PAHs from manufactured gas plant and aluminum smelter soils and sediments both in freshwater and saltwater locations. The studies that the EERC has performed with the commercial partners have continued to generate increased interest in both the regulatory communities and in the industries that have historically produced or utilized coal tar products. Both ASTM International and the U.S. Environmental Protection Agency (EPA) have accepted the pore water method developed at the EERC as standard methods. The studies have demonstrated the effectiveness of our techniques in predicting bioavailability of PAHs from ca. 250 impacted and background field sediments and soils. The field demonstrations from the final years of the project continued to build the foundation data for acceptance of our methods by the regulatory communities. The JV92 studies provide the single largest database in the world that includes measures of PAH bioavailability along with biological end points. These studies clearly demonstrated that present regulatory paradigms based on equilibrium partitioning greatly overpredict bioavailability. These investigations also laid the foundation for present (non-JV) studies being applied to PAHs and polychlorinated biphenyls (PCBs) at EPA Superfund sites, investigations into PAH and PCB bioavailability at U.S Department of Defense sites, and the application of the techniques to investigating the bioavailability of chlorinated dioxins and furans from impacted

  3. Application of Microextraction Techniques Including SPME and MESI to the Thermal Degradation of Polymers: A Review.

    Science.gov (United States)

    Kaykhaii, Massoud; Linford, Matthew R

    2017-03-04

    Here, we discuss the newly developed micro and solventless sample preparation techniques SPME (Solid Phase Microextraction) and MESI (Membrane Extraction with a Sorbent Interface) as applied to the qualitative and quantitative analysis of thermal oxidative degradation products of polymers and their stabilizers. The coupling of these systems to analytical instruments is also described. Our comprehensive literature search revealed that there is no previously published review article on this topic. It is shown that these extraction techniques are valuable sample preparation tools for identifying complex series of degradation products in polymers. In general, the number of products identified by traditional headspace (HS-GC-MS) is much lower than with SPME-GC-MS. MESI is particularly well suited for the detection of non-polar compounds, therefore number of products identified by this technique is not also to the same degree of SPME. Its main advantage, however, is its ability of (semi-) continuous monitoring, but it is more expensive and not yet commercialized.

  4. SPME GC/MS Analysis of Three Ornithogalum L. species from Turkey

    Directory of Open Access Journals (Sweden)

    Gülin Renda

    2016-01-01

    Full Text Available In this study, a solid phase micro extraction (SPME method with gas chromatography-mass spectrometry (GC-MS was used for analysis of volatile compounds in flowers and bulbs of three Ornithogalum species. The samples of flowers and bulbs of Ornithogalum sigmoideum, Ornithogalum orthophyllum, Ornithogalum oligophyllum was separately analyzed by SPME-GC-MS. A comparison of volatile compounds was made between species and the parts studied. A total of 70 compounds were identified and different volatile compounds were determined in distinct parts of the species. The major volatile organic compound of the flowers of O. sigmoideum and O. ornithogalum was furan (54.5% and 57.0% respectively. For O. oligophyllum the major volatile organic compound was nonanal (19.2%. Analyses revealed that SPME-GC-MS method is appropriate for the analysis of volatile compounds of Ornithogalum species.

  5. Comparative analysis of the aroma chemicals of Melissa officinalis using hydrodistillation and HS-SPME techniques

    Directory of Open Access Journals (Sweden)

    Shakeel-u- Rehman

    2017-05-01

    Full Text Available Headspace solid-phase micro extraction (HS-SPME coupled with gas chromatography–mass spectrometry (GC–MS has been used for the chemical analysis of Melissa officinalis (leaves cultivated in Institute Germplasm. The HS-SPME analysis led to the identification of 22 components constituting 99.1% of the total volatile constituents present in the leaves whereas its hydrodistillate led to the identification of 24 volatile constituents constituting 98.1% of the volatile material. The chemical composition of the SPME and hydrodistilled extract of M. officinalis leaves comprised mainly of oxygenated monoterpenes (78.5% and 57.8% respectively and sesquiterpene hydrocarbons (14.9% and 29.7% respectively. The major components identified in the HS-SPME extract were citronellal (31.1%, citronellol (18.3%, β-caryophyllene (12.0%, (E-citral (11.9%, (Z-citral (9.6%, geraniol (3.6%, (Z-β-ocimene (3.1% and 1-octen-3-ol (2.0% whereas hydrodistilled essential oil was rich in (Z-citral (19.6%, β-caryophyllene (13.2%, (E-citral (11.2%, citronellal (10.2%, germacrene-d (8.3%, δ-3-carene (5.0%, 6-methyl-5-hepten-2-one (3.7% and citronellyl acetate (3.7%. The comparative analysis of volatile constituents of M. officinalis leaf extract using HS-SPME and hydrodistillation techniques shows both qualitative as well as quantitative differences. The current study is the first report involving rapid analysis of volatile components of M. officinalis by HS-SPME.

  6. Is Solid Phase Microextraction (SPME) an appropriate method for extraction of volatile oxidation products from complex food systems

    DEFF Research Database (Denmark)

    Jacobsen, Charlotte; Horn, Anna Frisenfeldt; Lu, Henna Fung Sieng

    Volatile secondary lipid oxidation products can be identified and quantified by GC-FID or GC-MS. An extraction step is, however, needed before GC analysis. A range of different extraction methods are available such as static headspace, dynamic headspace and SPME. Each of these methods has its...... advantages and drawbacks. Among the advantages of the SPME method are its high sensitivity compared to static headspace and that it is less laborious than the dynamic headspace method. For these reasons, the use of SPME has increased in both academia and industry during the last decade. The extraction...... for analysis of lipid oxidation during storage of complex food matrices. Examples on how uncontrollable factors have affected results obtained with the SPME method in the authors’ lab will be given and the appropriateness of the SPME method for the analysis of volatile oxidation products in selected food...

  7. Solid phase microextraction (SPME) for extraction of volatile oxidation products from complex food systems – Pros and cons

    DEFF Research Database (Denmark)

    Jacobsen, Charlotte; Horn, Anna Frisenfeldt; Lu, Henna Fung Sieng

    Volatile secondary lipid oxidation products can be identified and quantified by GC-FID or GC-MS. An extraction step is, however, needed before GC analysis. A range of different extraction methods are available such as static headspace, dynamic headspace and SPME. Each of these methods has its...... advantages and drawbacks. Among the advantages of the SPME method are its high sensitivity compared to static headspace and that it is less laborious than the dynamic headspace method. For these reasons, the use of SPME has increased in both academia and industry during the last decade. The extraction...... for analysis of lipid oxidation during storage of complex food matrices. Examples on how uncontrollable factors have affected results obtained with the SPME method in the authors’ lab will be given and the appropriateness of the SPME method for the analysis of volatile oxidation products in selected food...

  8. Prediction of Partition Coefficients of Organic Compounds for SPME/PDMS

    Directory of Open Access Journals (Sweden)

    Liao Hsuan-Yu

    2016-01-01

    Full Text Available The partition coefficients of 51 organic compounds between SPME/PDMS and gas were compiled from the literature sources in this study. The effect of physicochemical properties and descriptors on the partitioning process of partition coefficients was explicated by the correlation analysis. The PDMS-gas partition coefficients were well correlated to the molecular weight of organic compounds (r = 0.832, p < 0.05. An empirical model, consisting of the molecular weight and the polarizability, was developed to appropriately predict the partition coefficients of organic compounds. The empirical model for estimating the PDMS-gas partition coefficient will contribute to the practical applications of the SPME technique.

  9. Robust Scientists

    DEFF Research Database (Denmark)

    Gorm Hansen, Birgitte

    their core i nterests, 2) developing a selfsupply of industry interests by becoming entrepreneurs and thus creating their own compliant industry partner and 3) balancing resources within a larger collective of researchers, thus countering changes in the influx of funding caused by shifts in political...... knowledge", Danish research policy seems to have helped develop politically and economically "robust scientists". Scientific robustness is acquired by way of three strategies: 1) tasting and discriminating between resources so as to avoid funding that erodes academic profiles and push scientists away from...

  10. A rapid screening procedure for the analysis of proliferation compounds in complex matrices using solid phase microextraction (SPME) and SPME with in-situ derivatization

    International Nuclear Information System (INIS)

    Alcaraz, A.; Hulsey, S.S.; Andresen, B.D.

    1995-01-01

    A variety of methods have been established using advanced chromatographic techniques and new detection systems for the analysis of chemical signatures associated with nuclear and chemical weapon (CW) proliferation. Most of these analytical methods are used in the laboratory and seldom applied in the field. The Chemical Weapons Convention (an international treaty to ban chemical weapons) may require the rapid on-site analysis of environmental samples which contain CW agents, their precursors, and/or their degradation products. In addition to the fact that certain countries are involved in CW non-compliance, there is a current uncertainty regarding nuclear proliferation. This also creates new demands on sample work-up and analytical instrumentation use in the field. The isolation and identification of unique chemical signatures in complex samples such as soils, waste tanks, and decontamination solutions would determine non-compliance. However, a primary area of detection research continues to be sample preparation. Most of the established sample cleanup technologies involve liquid/liquid, Soxhlet, or most recently, solid phase extraction (SPE). Despite the success of these traditional sample preparation techniques, they are time consuming and require multi-step procedures (especially when preparing samples for gas chromatographic mass-spectrometric analysis). The goal of this work is to demonstrate the advantages of utilizing SPME and SPME in-situ derivatization techniques to eliminate time consuming steps necessary to prepare a sample for on-site GC-MS. The authors' approach was to compare two SPME fibers and to develop methods to facilitate the isolation of polar and moderately polar proliferation compounds from complex environmental samples. This work will help to evaluate current SPME technologies for use during on-site environmental monitoring analysis

  11. Quantitative and enantioselective analysis of monoterpenes from plant chambers and in ambient air using SPME

    Science.gov (United States)

    Yassaa, N.; Custer, T.; Song, W.; Pech, F.; Kesselmeier, J.; Williams, J.

    2010-11-01

    A headspace solid-phase microextraction (HS-SPME) and gas chromatography/mass spectrometry (GC/MS) system has been developed for quantifying enantiomeric and nonenantiomeric monoterpenes in plant chamber studies and ambient air. Performance of this system was checked using a capillary diffusion system to produce monoterpene standards. The adsorption efficiency, competitive adsorption and chromatographic peak resolution of monoterpene enantiomer pairs were compared for three SPME fibre coatings: 75 μm Carboxen-PDMS (CAR-PDMS), 50/30 μm divinylbenzene-carboxen-polydimethylsiloxane (DVB-CAR-PDMS) and 65 μm divinylbenzene-polydimethylsiloxane (DVB-PDMS). Key parameters such as the linearity and reproducibility of the SPME system have been investigated in this work. The best compromise between the enantiomeric separation of monoterpenes and competitive adsorption of the isoprenoids on the solid SPME fibre coating was found for DVB-PDMS fibres. The optimum conditions using DVB-PDMS fibres were applied to measure the exchange rates of monoterpenes in the emission of Quercus ilex using a laboratory whole plant enclosure under light and dark conditions, as well as in ambient air. With 592 and 223 ng m-2 s-1 respectively, β-myrcene and limonene were the predominant monoterpenes in the emission of Q. ilex. These values were closely comparable to those obtained using a zNose and cartridge GC-FID systems.

  12. Direct determination of anabolic steroids in pig urine by a new SPME-GC-MS method.

    Science.gov (United States)

    Zhang, Zhuomin; Duan, Hongbin; Zhang, Lan; Chen, Xi; Liu, Wei; Chen, Guonan

    2009-05-15

    A new solid phase microextraction (SPME) method coupled with gas chromatography-mass spectrometry (GC-MS) was developed for rapid determination of four anabolic steroids such as 3alpha-hydroxy-5alpha-androstane-17-one (HA), dihydrotestosterone (DHT), androstenedione (AD) and methyltestosterone (MT) in pig urine. SPME was used to extract the four anabolic compounds directly without derivatization. The optimum SPME sampling conditions were based on the home-made carbowax-divinylbenzene (CW-DVB) fiber coating during extraction at 40 degrees C for 50 min with 0.18 g/mL NaCl solution and 750 rpm stirring speed. The linear ranges of the proposed method were in the range of 8-640 pg/mL for HA and DHT and 16-510 pg/mL for AD and MT, respectively. The detection limits (S/N=3) were from 2 to 8 pg/mL for the four anabolic steroids. This SPME method provided very high enrichment factors for the four anabolic steroids, which were 1063-fold and 965-fold for HA and DHT at the concentration of 8 pg/mL and 207-fold and 451-fold for AD and MT at the concentration of 16 pg/mL, respectively. The recoveries ranged from 71.3 to 121%, and the RSDs were lower than 12.9%. The method was sensitive and reliable for determination of trace anabolic steroids in biological samples.

  13. Using SPME fibers and Tenax to predict the bioavailability of pyrethroids and chlorpyrifos in field sediments

    International Nuclear Information System (INIS)

    Harwood, Amanda D.; Landrum, Peter F.; Weston, Donald P.; Lydy, Michael J.

    2013-01-01

    The presence of pyrethroids in both urban and agricultural sediments at levels lethal to invertebrates has been well documented. However, variations in bioavailability among sediments make accurate predictions of toxicity based on whole sediment concentrations difficult. A proposed solution to this problem is the use of bioavailability-based estimates, such as solid phase microextraction (SPME) fibers and Tenax beads. This study compared three methods to assess the bioavailability and ultimately toxicity of pyrethroid pesticides including field-deployed SPME fibers, laboratory-exposed SPME fibers, and a 24-h Tenax extraction. The objective of the current study was to compare the ability of these methods to quantify the bioavailable fraction of pyrethroids in contaminated field sediments that were toxic to benthic invertebrates. In general, Tenax proved a more sensitive method than SPME fibers and a correlation between Tenax extractable concentrations and mortality was observed. - Highlights: ► Can use bioavailability-based methods for pyrethroids in sediments. ► Tenax was a more sensitive technique. ► Tenax extractable concentrations relate to invertebrate mortality. - This research provides an important first step in using bioavailability-based techniques for estimating the bioavailability and toxicity of hydrophobic pesticides in field sediments.

  14. SPME as a tool in WEA - CONCAWE Contribution to OSPAR Demonstration Project 2005 - 2006

    NARCIS (Netherlands)

    Leslie, H.A.

    2006-01-01

    This document represents a compilation of various data and deliverables from the study programme. An executive summary is followed by the presentation of data generated in an interlaboratory study of effluents assessed using both EGOM-LLE and biomimetic SPME methods.

  15. Quantitative and enantioselective analysis of monoterpenes from plant chambers and in ambient air using SPME

    Directory of Open Access Journals (Sweden)

    N. Yassaa

    2010-11-01

    Full Text Available A headspace solid-phase microextraction (HS-SPME and gas chromatography/mass spectrometry (GC/MS system has been developed for quantifying enantiomeric and nonenantiomeric monoterpenes in plant chamber studies and ambient air. Performance of this system was checked using a capillary diffusion system to produce monoterpene standards. The adsorption efficiency, competitive adsorption and chromatographic peak resolution of monoterpene enantiomer pairs were compared for three SPME fibre coatings: 75 μm Carboxen-PDMS (CAR-PDMS, 50/30 μm divinylbenzene-carboxen-polydimethylsiloxane (DVB-CAR-PDMS and 65 μm divinylbenzene-polydimethylsiloxane (DVB-PDMS. Key parameters such as the linearity and reproducibility of the SPME system have been investigated in this work. The best compromise between the enantiomeric separation of monoterpenes and competitive adsorption of the isoprenoids on the solid SPME fibre coating was found for DVB-PDMS fibres. The optimum conditions using DVB-PDMS fibres were applied to measure the exchange rates of monoterpenes in the emission of Quercus ilex using a laboratory whole plant enclosure under light and dark conditions, as well as in ambient air. With 592 and 223 ng m−2 s−1 respectively, β-myrcene and limonene were the predominant monoterpenes in the emission of Q. ilex. These values were closely comparable to those obtained using a zNose and cartridge GC-FID systems.

  16. Development of a GC-MS-SPME Method for the Determination of Amines in Meteorites

    Science.gov (United States)

    Hilts, R. W.; Skelhorne, A. W.; Simkus, D.; Herd, C. D. K.

    2016-08-01

    A GC-MS-SPME analytical method for the direct determination of amines in aqueous solution has been developed. The key step in the procedure is the conversion of the amines into their non-volatile ammonium salts by protonation with HCl.

  17. SDE and SPME Analysis of Flavor Compounds in Jin Xuan Oolong Tea.

    Science.gov (United States)

    Sheibani, Ershad; Duncan, Susan E; Kuhn, David D; Dietrich, Andrea M; O'Keefe, Sean F

    2016-02-01

    Simultaneous distillation-extraction (SDE) and solid phase micro extraction (SPME) are procedures used for the isolation of flavor compounds in foods. The purpose of this study was to optimize SDE conditions (solvent and time) and to compare SDE with SPME for the isolation of flavor compounds in Jin Xuan oolong tea using GC-MS and GC-O. The concentration of volatile compounds isolated with diethyl ether was higher (P < 0.05) than for dichloromethane and concentration was higher at 40 min (P < 0.05) than 20 or 60 min extractions. For SDE, 128 volatiles were identified using GC-MS and 45 aroma active compounds using GC-O. Trans-nerolidol was the most abundant compound in oolong tea. The number of volatiles identified using GC-MS was lower in SPME than SDE. For SPME, 59 volatiles and 41 aroma active compounds were identified. The composition of the volatiles isolated by the 2 methods differed considerably but provided complementary information. © 2016 Institute of Food Technologists®

  18. Dynamic speciation analysis of atrazine in aqueous latex nanoparticle dispersions using solid phase microextraction (SPME)

    NARCIS (Netherlands)

    Benhabib, K.; Town, R.M.; Leeuwen, van H.P.

    2009-01-01

    Solid phase microextraction (SPME) is applied in the dynamic speciation analysis of the pesticide atrazine in an aqueous medium containing sorbing latex nanoparticles. It is found that the overall rate of extraction of the analyte is faster than in the absence of nanoparticles and governed by the

  19. HS-SPME GC/MS characterization of volatiles in raw and dry-roasted almonds (Prunus dulcis).

    Science.gov (United States)

    Xiao, Lu; Lee, Jihyun; Zhang, Gong; Ebeler, Susan E; Wickramasinghe, Niramani; Seiber, James; Mitchell, Alyson E

    2014-05-15

    A robust HS-SPME and GC/MS method was developed for analyzing the composition of volatiles in raw and dry-roasted almonds. Almonds were analyzed directly as ground almonds extracted at room temperature. In total, 58 volatiles were identified in raw and roasted almonds. Straight chain aldehydes and alcohols demonstrated significant but minimal increases, while the levels of branch-chain aldehydes, alcohols, heterocyclic and sulfur containing compounds increased significantly (500-fold) in response to roasting (palmonds) to 315.8±70.0 ng/g (averaged across the roasting treatments evaluated i.e. 28, 33 and 38 min at 138 °C) after roasting. Pyrazines were detected in only the roasted almonds, with the exception of 2,5-dimethylpyrazine, which was also found in raw almonds. The concentration of most alcohols increased in the roasted samples with the exception of 2-methyl-1-propanol, 3-methyl-1-butanol and 2-phenylethyl alcohol, which decreased 68%, 80%, and 86%, respectively. Copyright © 2013 Elsevier Ltd. All rights reserved.

  20. Evaluation of the volatile profile of Tuber liyuanum by HS-SPME with GC-MS.

    Science.gov (United States)

    Liu, Changjiao; Li, Yu

    2017-04-01

    The volatile components of Tuber liyuanum were determined by HS-SPME with GC-MS for the first time. The effects of different fibre coating, extraction time, extraction temperature and sample amount were studied to get optimal extraction conditions. The optimal conditions were SPME fibre of Carboxen/PDMS, extraction time of 40 min, extraction temperature of 80 °C, sample amount of 2 g. Under these conditions 57 compounds in volatile of T. liyuanum were detected with a resemblance percentage above 80%. Aldehydes and aromatics were the main chemical families identified. The contribution of 3-Octanone(11.67%), phenylethyl alcohol (10.60%), isopentana (9.29%) and methylbutana (8.06%) for the total volatile profile were more significant in T. liyuanum than other compounds.

  1. Solid Phase Microextraction (SPME in Determination of Pesticide Residues in Soil Samples

    Directory of Open Access Journals (Sweden)

    Rada Đurović

    2011-01-01

    Full Text Available The basic principles and application possibilities of the methods based on solid phase microextraction (SPME in the analysis of pesticide residues in soil samples are presented in the paper. The most important experimental parameters which affect SPME efficacy inpesticide determination (type and thickness of microextraction fiber, duration of microextraction,temperature at which it is conducted, effect of addition of salts (the effect of efflorescence,temperature and time of desorption, the choice of optimal solvent for pesticide exctraction from the soil and the optimal number of extraction steps, as well as general guidelines for their optimization are also shown. In the end, current applications of SPMEmethods in the analysis of pesticide residues in soil samples are presented.

  2. Comparison of SPME Methods for Determining Volatile Compounds in Milk, Cheese, and Whey Powder

    Directory of Open Access Journals (Sweden)

    Michael H. Tunick

    2013-11-01

    Full Text Available Solid phase microextraction and gas chromatography-mass spectrometry (SPME-GC-MS are commonly used for qualitative and quantitative analysis of volatile compounds in various dairy products, but conditions have to be adjusted to maximize release while not generating new compounds that are absent in the original sample. Queso Fresco, a fresh non-melting cheese, may be heated at 60 °C for 30 min; in contrast, compounds are produced in milk when exposed to light and elevated temperatures, so milk samples are heated as little as possible. Products such as dehydrated whey protein are more stable and can be exposed to longer periods (60 min of warming at lower temperature (40 °C without decomposition, allowing for capture and analysis of many minor components. The techniques for determining the volatiles in dairy products by SPME and GC-MS have to be optimized to produce reliable results with minimal modifications and analysis times.

  3. Polycyclic aromatic hydrocarbons bioavailability in industrial and agricultural soils: Linking SPME and Tenax extraction with bioassays.

    Science.gov (United States)

    Guo, Meixia; Gong, Zongqiang; Li, Xiaojun; Allinson, Graeme; Rookes, James; Cahill, David

    2017-06-01

    The aims of this study were to evaluate the bioavailability of polycyclic aromatic hydrocarbons (PAHs) in industrial and agricultural soils using chemical methods and a bioassay, and to study the relationships between the methods. This was conducted by comparing the quantities of PAHs extracted from two manufactured gas plant (MGP) soils and an agricultural soil with low level contamination by solid-phase micro-extraction (SPME) and Tenax-TA extraction with the quantities taken up by the earthworm (Eisenia fetida). In addition, a biodegradation experiment was conducted on one MGP soil (MGP-A) to clarify the relationship between PAH removal by biodegradation and the variation in PAH concentrations in soil pore water. Results demonstrated that the earthworm bioassay could not be used to examine PAH bioavailability in the tested MGP soils; which was the case even in the diluted MGP-A soils after biodegradation. However, the bioassay was successfully applied to the agricultural soil. These results suggest that earthworms can only be used for bioassays in soils with low toxicity. In general, rapidly desorbing concentrations extracted by Tenax-TA could predict PAH concentrations accumulated in earthworms (R 2 =0.66), while SPME underestimated earthworm concentrations by a factor of 2.5. Both SPME and Tenax extraction can provide a useful tool to predict PAH bioavailability for earthworms, but Tenax-TA extraction was proven to be a more sensitive and precise method than SPME for the prediction of earthworm exposure in the agricultural soil. Copyright © 2017. Published by Elsevier Inc.

  4. Determination of Sesquiterpenes in Wines by HS-SPME Coupled with GC-MS

    OpenAIRE

    Cincotta, Fabrizio; Verzera, Antonella; Tripodi, Gianluca; Condurso, Concetta

    2015-01-01

    The sesquiterpene compounds present in red wines were characterized and quantified by Headspace Solid-Phase Microextraction in combination with Gas Chromatography–Mass Spectrometry (HS-SPME-GC-MS). Sixteen sesquiterpenes were identified, mainly hydrocarbons but also derived oxygenated compounds. Sesquiterpenes were acyclic, monocyclic, byciclic and tryciclic. Sesquiterpenes were detected in SIM (selected ion monitoring) mode using their characteristics ions. All the sesquiterpenes were identi...

  5. Optimization of Solid Phase Micro-Extraction (SPME for Monitoring Occupational Exposure to Ethyl Benzene

    Directory of Open Access Journals (Sweden)

    H. Heidari

    2009-08-01

    Full Text Available AbstractBackground and Objectives: Analytical methods for volatile organic compounds (VOCs in different samples need extraction of compounds, by applying hazardous solvents. Solid phase micro-extraction (SPME is a solvent-free equilibrium extraction method, in which proper calibration can allow quantitative determinations of VOCs at a very good sensitivity without the use of any organic solvent. VOCs are generally present in urine only at trace levels, therefore, a sensitive procedure is needed for their trace determinations. Throughout this study, headspace solid phase micro-extraction (HS-SPME was followed by GC-FID for ethyl benzene in spiked urine was optimized.Methods: In this study, the parameters influencing SPME and gas chromatography of ethyl benzene, including extraction time, temperature, desorption temperature, desorption time, salt addition, sample pH, sample volume and sample agitation were investigated. Results: Extraction procedure was performed at 30°C for 6 min, using 0.2 gml-1 of NaCl in the sample solution. The sample volume and sample pH were optimized at 5 ml and 7 (neutral pH, respectively. Desorption of the ethyl benzene was carried out for 60 sec. at 250°C. The method was also validated with three different spiked urine samples and illustrated an appropriate reproducibility over six consecutive days as well as six within-day experiments. During this investigation, parameters of accuracy, linearity, and detection limits of the procedure were also evaluated.Conclusion: The developed method of HS- SPME-GC-FID proved to be a simple, convenient, and practical procedure, and was successfully used for measuring of ethyl benzene in spiked urine.

  6. Prediction of Partition Coefficients of Organic Compounds for SPME/PDMS

    OpenAIRE

    Liao Hsuan-Yu; Huang Miao-Ling; Lu Yu-Ting; Chao Keh-Ping

    2016-01-01

    The partition coefficients of 51 organic compounds between SPME/PDMS and gas were compiled from the literature sources in this study. The effect of physicochemical properties and descriptors on the partitioning process of partition coefficients was explicated by the correlation analysis. The PDMS-gas partition coefficients were well correlated to the molecular weight of organic compounds (r = 0.832, p < 0.05). An empirical model, consisting of the molecular weight and the polarizability, was ...

  7. SPME as a promising tool in translational medicine and drug discovery: From bench to bedside.

    Science.gov (United States)

    Goryński, Krzysztof; Goryńska, Paulina; Górska, Agnieszka; Harężlak, Tomasz; Jaroch, Alina; Jaroch, Karol; Lendor, Sofia; Skobowiat, Cezary; Bojko, Barbara

    2016-10-25

    Solid phase microextraction (SPME) is a technology where a small amount of an extracting phase dispersed on a solid support is exposed to the sample for a well-defined period of time. The open-bed geometry and biocompatibility of the materials used for manufacturing of the devices makes it very convenient tool for direct extraction from complex biological matrices. The flexibility of the formats permits tailoring the method according the needs of the particular application. Number of studies concerning monitoring of drugs and their metabolites, analysis of metabolome of volatile as well as non-volatile compounds, determination of ligand-protein binding, permeability and compound toxicity was already reported. All these applications were performed in different matrices including biological fluids and tissues, cell cultures, and in living animals. The low invasiveness of in vivo SPME, ability of using very small sample volumes and analysis of cell cultures permits to address the rule of 3R, which is currently acknowledged ethical standard in R&D labs. In the current review systematic evaluation of the applicability of SPME to studies required to be conduct at different stages of drug discovery and development and translational medicine is presented. The advantages and challenges are discussed based on the examples directly showing given experimental design or on the studies, which could be translated to the models routinely used in drug development process. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. SPME GC/MS determination of organochlorine pesticides in water samples

    Directory of Open Access Journals (Sweden)

    Yerbolat Sailaukhanuly

    2013-05-01

    Full Text Available Headspace solid phase microextraction (HS-SPME in combination with gas chromatography and mass-spectrometry (GC/MS was studied for analysis of water samples. The organochlorine pesticides (OCPs, p,p'-DDT, p,p'-DDD, and p,p'-DDE were collected and analyzed by GC/MS. To select of effective fiber coatings four types of SPME fibers were examined and compared. The parameters effecting the efficiency of HS-SPME such as extraction and pre-incubation time and extraction temperature, effect of solvent nature, ionic strength were studied to obtain optimal parameters. The method was developed using spiked water samples in a concentration range  10 - 500 ng/L. The calibration curve was linear over the studied concentration range with r≥0.9925. The detection limits varied from 1.57 to 2.08 ng/L. An authentic water samples from contaminated lake with OCPs were analyzed by developed method.

  9. Headspace-SPME-GC/MS as a simple cleanup tool for sensitive 2,6-diisopropylphenol analysis from lipid emulsions and adaptable to other matrices.

    Science.gov (United States)

    Pickl, Karin E; Adamek, Viktor; Gorges, Roland; Sinner, Frank M

    2011-07-15

    Due to increased regulatory requirements, the interaction of active pharmaceutical ingredients with various surfaces and solutions during production and storage is gaining interest in the pharmaceutical research field, in particular with respect to development of new formulations, new packaging material and the evaluation of cleaning processes. Experimental adsorption/absorption studies as well as the study of cleaning processes require sophisticated analytical methods with high sensitivity for the drug of interest. In the case of 2,6-diisopropylphenol - a small lipophilic drug which is typically formulated as lipid emulsion for intravenous injection - a highly sensitive method in the concentration range of μg/l suitable to be applied to a variety of different sample matrices including lipid emulsions is needed. We hereby present a headspace-solid phase microextraction (HS-SPME) approach as a simple cleanup procedure for sensitive 2,6-diisopropylphenol quantification from diverse matrices choosing a lipid emulsion as the most challenging matrix with regard to complexity. By combining the simple and straight forward HS-SPME sample pretreatment with an optimized GC-MS quantification method a robust and sensitive method for 2,6-diisopropylphenol was developed. This method shows excellent sensitivity in the low μg/l concentration range (5-200μg/l), good accuracy (94.8-98.8%) and precision (intraday-precision 0.1-9.2%, inter-day precision 2.0-7.7%). The method can be easily adapted to other, less complex, matrices such as water or swab extracts. Hence, the presented method holds the potential to serve as a single and simple analytical procedure for 2,6-diisopropylphenol analysis in various types of samples such as required in, e.g. adsorption/absorption studies which typically deal with a variety of different surfaces (steel, plastic, glass, etc.) and solutions/matrices including lipid emulsions. Copyright © 2011 Elsevier B.V. All rights reserved.

  10. Screening for γ-Nonalactone in the Headspace of Freshly Cooked Non-Scented Rice Using SPME/GC-O and SPME/GC-MS

    Directory of Open Access Journals (Sweden)

    Jie Yu Chen

    2009-08-01

    Full Text Available The determination of γ-nonalactone as one of the important odor-active compounds in freshly cooked non-scented rice is reported. It was evaluated by gas chromatography-olfactometry (GC-O analysis and identified by gas chromatography-mass spectrometry (GC-MS analysis in the headspace above the freshly cooked non-scented rice samples extracted by using a modified headspace solid-phase microextraction (SPME method. This component had a mass spectrum with a characteristic ion peak at m/z 85 (100% and a linear retention index (RI of 2,023 on a DB Wax column, consistent with those of an authentic sample of γ-nonalactone. The odor characterization of a strong, sweet, coconut-like aroma of this compound was also validated by GC-O comparison with the authentic compound.

  11. Optimization of Solid Phase Micro-Extraction (SPME for Monitoring Occupational Exposure to Ethyl Benzene

    Directory of Open Access Journals (Sweden)

    H Heidari

    2012-05-01

    Full Text Available

    Background and Objectives: Analytical methods for volatile organic compounds (VOCs in different samples need extraction of compounds, by applying hazardous solvents. Solid phase micro-extraction (SPME is a solvent-free equilibrium extraction method, in which proper calibration can allow quantitative determinations of VOCs at a very good sensitivity without the use of any organic solvent. VOCs are generally present in urine only at trace levels, therefore, a sensitive procedure is needed for their trace determinations. Throughout this study, headspace solid phase micro-extraction (HS-SPME was followed by GC-FID for ethyl benzene in spiked urine was optimized.

    Methods: In this study, the parameters influencing SPME and gas chromatography of ethyl benzene, including extraction time, temperature, desorption temperature, desorption time, salt addition, sample pH, sample volume and sample agitation were investigated.

    Results: Extraction procedure was performed at 30°C for 6 min, using 0.2 gml-1 of NaCl in the sample solution. The sample volume and sample pH were optimized at 5 ml and 7 (neutral pH, respectively. Desorption of the ethyl benzene was carried out for 60 sec. at 250°C. The method was also validated with three different spiked urine samples and illustrated an appropriate reproducibility over six consecutive days as well as six within-day experiments. During this investigation, parameters of accuracy, linearity, and detection limits of the procedure were also evaluated.

    Conclusion: The developed method of HS- SPME-GC-FID proved to be a simple, convenient, and practical procedure, and was successfully used for measuring of ethyl benzene in spiked urine.

  12. VOLATILE COMPOUNDS OF LITHRAEA CAUSTICA (LITRE) DETERMINATED BY SOLID PHASE MICRO-EXTRACTION (SPME)

    OpenAIRE

    GARBARINO, JUAN A; SALVATORE, GIUSEPPE; PIVANOVO, MARISA; CHAMY, MARÍA CRISTINA; NICOLETTI, MARCELLO; DE IOANNES, ALFREDO

    2002-01-01

    The head space of the aerial parts of Lithraea caustica was analyzed by Solid Phase Micro-Extraction (SPME) technique, obtaining as main volatile compounds the monoterpenes, myrcene, a -pinene, , p-cymene and limonene, as well as the sesquiterpene caryophylene. De las partes áereas de Lithraea caustica y usando la técnica de Micro-Extracción en Fase Sólida (MEFS), fueron identificados y cuantificados los principales compuestos volátiles: los monoterpenos, mirceno, a -pineno, p-cimeno y lim...

  13. Analysis of flavor-related compounds from tabacco using SPME-GC-MS

    Energy Technology Data Exchange (ETDEWEB)

    Park, G.B.; Lee, S.G. [Korea Research Institute of Chemical Technology, Taejeon (Korea)

    2001-04-01

    The flavor-related compounds contained in tobacco were analyzed by selected ion monitoring (SIM) method using headspace SPME gas chromatography-mass spectrometry (GC-MS). Flavor-related compounds were estragole, pulegone, trans-anethole, safrole, piperonal, eugenol, methyleugenol, coumarin, trans-isoeugenol, trans-methyleugenol and myristicin More than one of the flavor-related compounds were detected in the range of 0.001-1.3 {mu}g/g from all brands of tobacco studied. The recovery was ranged from 89.1 to 102.9% and relative standard deviation was ranged from 2.6 to 25.2%. (author). 19 refs., 4 tabs., 2 figs.

  14. Improving Student Understanding of Qualitative and Quantitative Analysis via GC/MS Using a Rapid SPME-Based Method for Determination of Trihalomethanes in Drinking Water

    Science.gov (United States)

    Huang, Shu Rong; Palmer, Peter T.

    2017-01-01

    This paper describes a method for determination of trihalomethanes (THMs) in drinking water via solid-phase microextraction (SPME) GC/MS as a means to develop and improve student understanding of the use of GC/MS for qualitative and quantitative analysis. In the classroom, students are introduced to SPME, GC/MS instrumentation, and the use of MS…

  15. Analysis of aldehydes in human exhaled breath condensates by in-tube SPME-HPLC.

    Science.gov (United States)

    Wang, ShuLing; Hu, Sheng; Xu, Hui

    2015-11-05

    In this paper, polypyrrole/graphene (PPy/G) composite coating was prepared by a facile electrochemical polymerization strategy on the inner surface of a stainless steel (SS) tube. Based on the coating tube, a novel online in-tube solid-phase microextraction -high performance liquid chromatography (IT-SPME-HPLC) was developed and applied for the extraction of aldehydes in the human exhaled breath condensates (EBC). The hybrid PPy/G nanocomposite exhibits remarkable chemical and mechanical stability, high selectivity, and satisfactory extraction performance toward aldehyde compounds. Moreover, the proposed online IT-SPME-HPLC method possesses numerous superiorities, such as time and cost saving, process simplicity, high precision and sensitivity. Some parameters related to extraction efficiency were optimized systematically. Under the optimal conditions, the recoveries of the aldehyde compounds at three spiked concentration levels varied in the range of 85%-117%. Good linearity was obtained with excellent correlation coefficients (R(2)) being larger than 0.994. The relative standard deviations (n = 5) of the method ranged from 1.8% to 11.3% and the limits of detection were between 2.3 and 3.3 nmol L(-1). The successful application of the proposed method in human EBC indicated that it is a promising approach for the determination of trace aldehyde metabolites in complex EBC samples. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Polyelectrolyte coatings prevent interferences from charged nanoparticles in SPME speciation analysis

    International Nuclear Information System (INIS)

    Zielińska, Katarzyna; Leeuwen, Herman P. van

    2014-01-01

    Highlights: • For the first time SPME fiber is coated with polyelectrolyte layer. • Sorption of nanoparticles on the solid phase surface is prevented. • Polyelectrolyte-modified fiber enables extraction of free analyte in presence of sorbing nanoparticles. - Abstract: In this work we present a new approach for protection of the fiber in solid phase microextraction (SPME) from interfering charged particles present in the sample medium. It involves coating of commercial poly(dimethylsiloxane) extraction phase with polyelectrolyte layer composed of poly(diallyldimethylammonium chloride), and poly(sodium 4-styrenesulfonate). The modified fiber provides reproducible, convenient and fast extraction capabilities toward the model analyte, triclosan (TCS). A negatively charged polyelectrolyte coating prevents sorbing oxidic nanoparticles from both partitioning into the PDMS phase and aggregation at its surface. The results for the TCS/nanoparticle sample show that the polyelectrolyte layer-modified solid phase extracts just the free form of the organic compound and enables dynamic speciation analysis of the nanoparticulate target analyte complex

  17. Analysis of Organic Volatile Flavor Compounds in Fermented Stinky Tofu Using SPME with Different Fiber Coatings

    Directory of Open Access Journals (Sweden)

    Wei Guan

    2012-03-01

    Full Text Available The organic volatile flavor compounds in fermented stinky tofu (FST were studied using SPME-GC/MS. A total of 39 volatile compounds were identified, including nine esters, seven alcohols, five alkenes, four sulfides, three heterocycles, three carboxylic acids, three ketones, two aldehydes, one phenol, one amine and one ether. These compounds were determined by MS, and conformed by comparison of the retention times of the separated constituents with those of authentic samples and by comparison of retention indexes (RIs of separated constituents with the RIs reported in the literature. The predominant volatile compound in FST was indole, followed by dimethyl trisulfide, phenol, dimethyl disulfide and dimethyl tetrasulfide. In order to find a better extraction time, the extraction times was optimized for each type of SPME fiber; the results show that the best extraction time for Carboxen/PDMS is 60 min, for PDMS/DVB 30 min, for DVB/CAR/PDMS 60 min and for PDMS 75 min. Of the four fibers used in this work, Carboxen/PDMS is found to be the most suitable to extract the organic volatile flavor compounds in fermented stinky tofu.

  18. Quantification of Polyfunctional Thiols in Wine by HS-SPME-GC-MS Following Extractive Alkylation.

    Science.gov (United States)

    Musumeci, Lauren E; Ryona, Imelda; Pan, Bruce S; Loscos, Natalia; Feng, Hui; Cleary, Michael T; Sacks, Gavin L

    2015-07-06

    Analyses of key odorous polyfunctional volatile thiols in wines (3-mercaptohexanol (3-MH), 3-mercaptohexylacetate (3-MHA), and 4-mercapto-4-methyl-2-pentanone (4-MMP)) are challenging due to their high reactivity and ultra-trace concentrations, especially when using conventional gas-chromatography electron impact mass spectrometry (GC-EI-MS). We describe a method in which thiols are converted to pentafluorobenzyl (PFB) derivatives by extractive alkylation and the organic layer is evaporated prior to headspace solid phase microextraction (HS-SPME) and GC-EI-MS analysis. Optimal parameters were determined by response surface area modeling. The addition of NaCl solution to the dried SPME vials prior to extraction resulted in up to less than fivefold improvement in detection limits. Using 40 mL wine samples, limits of detection for 4-MMP, 3-MH, and 3-MHA were 0.9 ng/L, 1 ng/L, and 17 ng/L, respectively. Good recovery (90%-109%) and precision (5%-11% RSD) were achieved in wine matrices. The new method was used to survey polyfunctional thiol concentrations in 61 commercial California and New York State wines produced from V. vinifera (Riesling, Gewürztraminer, Cabernet Sauvignon, Sauvignon blanc and non-varietal rosé wines), V. labruscana (Niagara), and Vitis spp. (Cayuga White). Mean 4-MMP concentrations in New York Niagara (17 ng/L) were not significantly different from concentrations in Sauvignon blanc, but were significantly higher than 4-MMP in other varietal wines.

  19. Analysis of organic micropollutants in drinking water using SPME and GC-MS

    International Nuclear Information System (INIS)

    Guidotti, M.; Ravaioli, G.

    1999-01-01

    In this work the purpose was to develop accurate and reproducible methods for the qualitative and quantitative analysis of pesticides/herbicides, phthalates, chlorinated solvents, trihalomethanes, polycyclic aromatic hydrocarbons (PAHs) and chlorophenols in drinking waters, using solid-phase micro extraction and GC-MS techniques. The SPME developed by J. Pawliszyn and co-workers, consists of an fused silica fibre, coated with an appropriate absorbent phase, hosted inside the needle of a holder that looks like a GC-syringe; the needle pierces the septum of a sealed vial and the fibre is lowered, by depressing the plunger of the holder, into the liquid (or in the headspace, if that is the case) that contains the analytes of interest. After a set period of time, necessary to reach the partitioning equilibrium, the fibre is retracted inside the needle, the needle is inserted into the GC injector port and the fibre pushed in the heated injector. Here the compounds of interest (that have adsorbed onto the fibre) are thermally desorbed and analysed by GC-MS. After three minutes the fibre is extracted and is ready for a new analysis. The SPME technique has already found many applications in food and environmental analysis. Many of the analytes investigated in this research are listed Italian legislation as possible pollutants of drinking waters and their presence and concentrations require monitoring. The list of compounds included in this work is reported in Table 1

  20. SPME-Based Ca-History Method for Measuring SVOC Diffusion Coefficients in Clothing Material.

    Science.gov (United States)

    Cao, Jianping; Liu, Ningrui; Zhang, Yinping

    2017-08-15

    Clothes play an important role in dermal exposure to indoor semivolatile organic compounds (SVOCs). The diffusion coefficient of SVOCs in clothing material (D m ) is essential for estimating SVOC sorption by clothing material and subsequent dermal exposure to SVOCs. However, few studies have reported the measured D m for clothing materials. In this paper, we present the solid-phase microextraction (SPME) based C a -history method. To the best of our knowledge, this is the first try to measure D m with known relative standard deviation (RSD). A thin sealed chamber is formed by a circular ring and two pieces of flat SVOC source materials that are tightly covered by the targeted clothing materials. D m is obtained by applying an SVOC mass transfer model in the chamber to the history of gas-phase SVOC concentrations (C a ) in the chamber measured by SPME. D m 's of three SVOCs, di-iso-butyl phthalate (DiBP), di-n-butyl phthalate (DnBP), and tris(1-chloro-2-propyl) phosphate (TCPP), in a cotton T-shirt can be obtained within 16 days, with RSD less than 3%. This study should prove useful for measuring SVOC D m in various sink materials. Further studies are expected to facilitate application of this method and investigate the effects of temperature, relative humidity, and clothing material on D m .

  1. Methods for robustness programming

    NARCIS (Netherlands)

    Olieman, N.J.

    2008-01-01

    Robustness of an object is defined as the probability that an object will have properties as required. Robustness Programming (RP) is a mathematical approach for Robustness estimation and Robustness optimisation. An example in the context of designing a food product, is finding the best composition

  2. Robustness in laying hens

    NARCIS (Netherlands)

    Star, L.

    2008-01-01

    The aim of the project ‘The genetics of robustness in laying hens’ was to investigate nature and regulation of robustness in laying hens under sub-optimal conditions and the possibility to increase robustness by using animal breeding without loss of production. At the start of the project, a robust

  3. Characterization of Fish Sauce Aroma Impact Compounds Using GC-MS, SPME-Osme-GCO, and Stevens' Power Law Exponents

    Science.gov (United States)

    The objectives of this study were to characterize volatile compounds and to determine the characteristic aromas associated with impact compounds in 4 fish sauces using solid-phase micro-extraction, gas chromatography-mass spectrometry, Osme, and gas chromatography olfactometry (SPME-Osme-GCO) couple...

  4. HS-SPME-GC-MS ANALYSIS OF VOLATILE AND SEMI-VOLATILE COMPOUNDS FROM DRIED LEAVES OF Mikania glomerata Sprengel

    Directory of Open Access Journals (Sweden)

    Esmeraldo A. Cappelaro

    2015-03-01

    Full Text Available This paper reports on the identification of volatile and semi-volatile compounds and a comparison of the chromatographic profiles obtained by Headspace Solid-Phase Microextraction/Gas Chromatography with Mass Spectrometry detection (HS-SPME-GC-MS of dried leaves of Mikania glomerata Sprengel (Asteraceae, also known as 'guaco.' Three different types of commercial SPME fibers were tested: polydimethylsiloxane (PDMS, polydimethylsiloxane/divinylbenzene (PDMS/DVB and polyacrylate (PA. Fifty-nine compounds were fully identified by HS-SPME-HRGC-MS, including coumarin, a marker for the quality control of guaco-based phytomedicines; most of the other identified compounds were mono- and sesquiterpenes. PA fibers performed better in the analysis of coumarin, while PDMS-DVB proved to be the best choice for a general and non-selective analysis of volatile and semi-volatile guaco-based compounds. The SPME method is faster and requires a smaller sample than conventional hydrodistillation of essential oils, providing a general overview of the volatile and semi-volatile compounds of M. glomerata.

  5. Screening of transformation products in soils contaminated with unsymmetrical dimethylhydrazine using headspace SPME and GC-MS

    NARCIS (Netherlands)

    Kenessov, B.N.; Koziel, J.A.; Grotenhuis, J.T.C.; Carlsen, L.

    2010-01-01

    The paper describes a novel SPME-based approach for sampling and analysis of transformation products of highly reactive and toxic unsymmetrical dimethylhydrazine (UDMH) which is used as a fuel in many Russian, European, Indian, and Chinese heavy cargo carrier rockets. The effects of several

  6. Determination of benzene, toluene, ethylbenzene and xylene in field and laboratory by means of cold fiber SPME equipped with thermoelectric cooler and GC/FID method

    Directory of Open Access Journals (Sweden)

    Tajik Leila

    2017-09-01

    Full Text Available A simple and effective cooling device based on a thermoelectric cooler was applied to cool the SPME fiber. The device was used for quantitative extraction of aromatic hydrocarbons in the air. Several factors such as coating temperature, extraction temperature and relative humidity in the laboratory setting were optimized. Comparison of the results between the cold fiber SPME (CF-SPME and NIOSH 1501 method on standard test atmosphere indicated a satisfactory agreement. The CF-SPME and SPME method were also compared. The results revealed that CF-SPME has the most appropriate outcome for the extraction of aromatic hydrocarbons from the ambient air. The cold fiber SPME technique showed good results for several validation parameters. Under the optimized conditions, the limits of detection (LOD and the limits of quantification (LOQ ranged from 0.00019 to 0.00033 and 0.0006 to 0.001 ng ml−1, respectively. The intra-day relative standard deviation (RSD showed ranging from 4.8 to 10.5%.

  7. Optimization of HS-SPME/GC-MS analysis and its use in the profiling of illicit ecstasy tablets (Part 1).

    Science.gov (United States)

    Bonadio, Federica; Margot, Pierre; Delémont, Olivier; Esseiva, Pierre

    2009-05-30

    A headspace solid-phase microextraction procedure (HS-SPME) was developed for the profiling of traces present in 3,4-methylenedioxymethylampethamine (MDMA). Traces were first extracted using HS-SPME and then analyzed by gas chromatography-mass spectroscopy (GC-MS). The HS-SPME conditions were optimized using varying conditions. Optimal results were obtained when 40 mg of crushed MDMA sample was heated at 80 degrees C for 15 min, followed by extraction at 80 degrees C for 15 min with a polydimethylsiloxane/divinylbenzene coated fibre. A total of 31 compounds were identified as traces related to MDMA synthesis, namely precursors, intermediates or by-products. In addition some fatty acids used as tabletting materials and caffeine used as adulterant, were also detected. The use of a restricted set of 10 target compounds was also proposed for developing a screening tool for clustering samples having close profile. 114 seizures were analyzed using an SPME auto-sampler (MultiPurpose Samples MPS2), purchased from Gerstel GMBH & Co. (Germany), and coupled to GC-MS. The data was handled using various pre-treatment methods, followed by the study of similarities between sample pairs based on the Pearson correlation. The results show that HS-SPME, coupled with the suitable statistical method is a powerful tool for distinguishing specimens coming from the same seizure and specimens coming from different seizures. This information can be used by law enforcement personnel to visualize the ecstasy distribution network as well as the clandestine tablet manufacturing.

  8. HS-SPME analysis of volatile organic compounds of coniferous needle litter

    Science.gov (United States)

    Isidorov, V. A.; Vinogorova, V. T.; Rafałowski, K.

    The composition of volatile emission of Scots pine ( Pinus sylvestris) and spruce ( Picea exelsa) litter was studied by gas chromatography-mass spectrometry (GC-MS) and samples were collected by solid-phase microextraction (SPME) method. The list of identified compounds includes over 60 organic substances of different classes. It was established that volatile emission contain not only components of essential oils of pine and spruce needles but also a large number of organic compounds which are probably secondary metabolites of litter-decomposing fungi. They include lower carbonyl compounds and alcohols as well as products of terpene dehydration and oxidation. These data show that the processes of litter decomposition are an important source of reactive organic compounds under canopy of coniferous forests.

  9. Differentiation of Toxic Molds via Headspace SPME-GC/MS and Canine Detection

    Directory of Open Access Journals (Sweden)

    Kenneth G. Furton

    2007-08-01

    Full Text Available Indoor mold growth has recently become a concern in the legal world in regards to insurance litigation. Hazardous mold exposure to humans has been linked to many acute and chronic adverse health effects including death. As it grows, mold produces several types of primary and secondary metabolites, including microbial volatile organic compounds (MVOCs. Microbial volatile organic compound emission may be used as a preliminary indication of a mold infestation that is invisible to the unaided eye. The objective of the study is to identify the unique odor signatures of three species of molds, Aspergillus versicolor, Penicillium chrysogenum, and Stachybotrys chartarum by SPME-GC/MS analysis. Determining the compounds that are emitted by the selected species has made it possible to conduct validation studies of canine detection of these mold species through a series of field tests.

  10. Authenticity of raspberry flavor in food products using SPME-chiral-GC-MS

    DEFF Research Database (Denmark)

    Hansen, Anne-Mette Sølvbjerg; Frandsen, Henrik Lauritz; Fromberg, Arvid

    2015-01-01

    A fast and simple method for authenticating raspberry flavors from food products was developed. The two enantiomers of the compound (E)-α-ionone from raspberry flavor were separated on a chiral gas chromatographic column. Based on the ratio of these two enantiomers the naturalness of a raspberry...... flavor can be evaluated due to the fact that a natural flavor will consist almost exclusively of the R enantiomer, while a chemical synthesis of the same compound will result in a racemic mixture. 27 food products containing raspberry flavors where investigated using SPME-chiral-GC-MS. We found raspberry...... distribution of the R and S isomer. Two products were labelled to contain natural raspberry flavors but were found to contain almost equal amounts of both enantiomers indicating a presence of synthetic raspberry flavors only. Additionally, two products labelled to contain both raspberry juice and flavor showed...

  11. Use of solid phase microextraction (SPME) for profiling the volatile metabolites produced by Glomerella cingulata.

    Science.gov (United States)

    Miyazawa, Mitsuo; Kimura, Minako; Yabe, Yoshito; Tsukamoto, Daisuke; Sakamoto, Masaya; Horibe, Isao; Okuno, Yoshiharu

    2008-01-01

    The profile of volatile organic compounds (VOCs) released from Glomerella cingulata using solid phase microextraction (SPME) with different fibers, Polydimethylsiloxane (PDMS), Polydimethylsiloxane/Divinylbenzene (PDMS/DVB), Carboxen/Polydimethylsiloxane (CAR/PDMS) and Divinylbenzene/Carboxen/Polydimethylsiloxane (DVB/CAR/PDMS), was investigated. C4-C6 aliphatic alcohols were the predominant fraction of VOCs isolated by CAR/PDMS fiber. Sesquiterpene hydrocarbons represented 20.3% of VOCs isolated by PDMS fiber. During the growth phase, Ochracin was produced in the large majority of VOCs. 3-Methylbutanol and phenylethyl alcohol were found in the log phase of it. Alcohols were found in cultures of higher age, while sesquiterpenes were found to be characteristic of initial growth stage of G. cingulata.

  12. Simple and accurate quantification of BTEX in ambient air by SPME and GC-MS.

    Science.gov (United States)

    Baimatova, Nassiba; Kenessov, Bulat; Koziel, Jacek A; Carlsen, Lars; Bektassov, Marat; Demyanenko, Olga P

    2016-07-01

    Benzene, toluene, ethylbenzene and xylenes (BTEX) comprise one of the most ubiquitous and hazardous groups of ambient air pollutants of concern. Application of standard analytical methods for quantification of BTEX is limited by the complexity of sampling and sample preparation equipment, and budget requirements. Methods based on SPME represent simpler alternative, but still require complex calibration procedures. The objective of this research was to develop a simpler, low-budget, and accurate method for quantification of BTEX in ambient air based on SPME and GC-MS. Standard 20-mL headspace vials were used for field air sampling and calibration. To avoid challenges with obtaining and working with 'zero' air, slope factors of external standard calibration were determined using standard addition and inherently polluted lab air. For polydimethylsiloxane (PDMS) fiber, differences between the slope factors of calibration plots obtained using lab and outdoor air were below 14%. PDMS fiber provided higher precision during calibration while the use of Carboxen/PDMS fiber resulted in lower detection limits for benzene and toluene. To provide sufficient accuracy, the use of 20mL vials requires triplicate sampling and analysis. The method was successfully applied for analysis of 108 ambient air samples from Almaty, Kazakhstan. Average concentrations of benzene, toluene, ethylbenzene and o-xylene were 53, 57, 11 and 14µgm(-3), respectively. The developed method can be modified for further quantification of a wider range of volatile organic compounds in air. In addition, the new method is amenable to automation. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Changes in SPME-extracted volatile compounds from Iberian ham during ripening

    Directory of Open Access Journals (Sweden)

    García, Carmen

    2009-07-01

    Full Text Available A headspace SPME procedure was tested to study the evolution of volatile compounds during the ripening of Iberian hams from pigs reared in a Montanera system (outdoorbased, with acorn and pasture available and a HO-Pienso system (indoor-based, with a high oleic acid concentrate. The effect of the ripening time on volatile compounds was more marked than the effect of feeding system. Most volatile compounds affected by the ripening time were compounds that come from Strecker and Maillard reactions, which increased significantly ( p Un procedimiento de microextración en fase sólida (SPME en espacio de cabeza fue ensayado para estudiar la evolución de los compuestos volátiles durante la curación de Jamones Ibéricos de cerdos criados en régimen de montanera (en libertad, con bellotas y pasto disponible y un sistema OH-Pienso (estabulados, con un pienso alto en ácido oléico. El efecto del tiempo de curación en los compuestos volátiles fue más marcado que el efecto de la alimentación. La mayoría de los compuestos volátiles afectados por el tiempo de curación fueron compuestos que proceden de la reacción de Strecker y Maillard, que se incrementaron significativamente (p p < 0.05. Algunos de ellos (ácido butanoico, 2,6- dimetilpiracina y 1-octen-3-ol fueron más abundantes en jamones de Montanera que en jamones de Pienso. Estas pequeñas diferencias podrían ser importantes porque los compuestos involucrados han sido identificados como aromas del jamón Ibérico.

  14. Quantification of Polyfunctional Thiols in Wine by HS-SPME-GC-MS Following Extractive Alkylation

    Directory of Open Access Journals (Sweden)

    Lauren E. Musumeci

    2015-07-01

    Full Text Available Analyses of key odorous polyfunctional volatile thiols in wines (3-mercaptohexanol (3-MH, 3-mercaptohexylacetate (3-MHA, and 4-mercapto-4-methyl-2-pentanone (4-MMP are challenging due to their high reactivity and ultra-trace concentrations, especially when using conventional gas-chromatography electron impact mass spectrometry (GC-EI-MS. We describe a method in which thiols are converted to pentafluorobenzyl (PFB derivatives by extractive alkylation and the organic layer is evaporated prior to headspace solid phase microextraction (HS-SPME and GC-EI-MS analysis. Optimal parameters were determined by response surface area modeling. The addition of NaCl solution to the dried SPME vials prior to extraction resulted in up to less than fivefold improvement in detection limits. Using 40 mL wine samples, limits of detection for 4-MMP, 3-MH, and 3-MHA were 0.9 ng/L, 1 ng/L, and 17 ng/L, respectively. Good recovery (90%–109% and precision (5%–11% RSD were achieved in wine matrices. The new method was used to survey polyfunctional thiol concentrations in 61 commercial California and New York State wines produced from V. vinifera (Riesling, Gewürztraminer, Cabernet Sauvignon, Sauvignon blanc and non-varietal rosé wines, V. labruscana (Niagara, and Vitis spp. (Cayuga White. Mean 4-MMP concentrations in New York Niagara (17 ng/L were not significantly different from concentrations in Sauvignon blanc, but were significantly higher than 4-MMP in other varietal wines.

  15. Perceptual Robust Design

    DEFF Research Database (Denmark)

    Pedersen, Søren Nygaard

    The research presented in this PhD thesis has focused on a perceptual approach to robust design. The results of the research and the original contribution to knowledge is a preliminary framework for understanding, positioning, and applying perceptual robust design. Product quality is a topic...... been presented. Therefore, this study set out to contribute to the understanding and application of perceptual robust design. To achieve this, a state-of-the-art and current practice review was performed. From the review two main research problems were identified. Firstly, a lack of tools...... for perceptual robustness was found to overlap with the optimum for functional robustness and at most approximately 2.2% out of the 14.74% could be ascribed solely to the perceptual robustness optimisation. In conclusion, the thesis have offered a new perspective on robust design by merging robust design...

  16. Robustness of Structural Systems

    DEFF Research Database (Denmark)

    Canisius, T.D.G.; Sørensen, John Dalsgaard; Baker, J.W.

    2007-01-01

    The importance of robustness as a property of structural systems has been recognised following several structural failures, such as that at Ronan Point in 1968,where the consequenceswere deemed unacceptable relative to the initiating damage. A variety of research efforts in the past decades have...... attempted to quantify aspects of robustness such as redundancy and identify design principles that can improve robustness. This paper outlines the progress of recent work by the Joint Committee on Structural Safety (JCSS) to develop comprehensive guidance on assessing and providing robustness in structural...... systems. Guidance is provided regarding the assessment of robustness in a framework that considers potential hazards to the system, vulnerability of system components, and failure consequences. Several proposed methods for quantifying robustness are reviewed, and guidelines for robust design...

  17. Robust multivariate analysis

    CERN Document Server

    J Olive, David

    2017-01-01

    This text presents methods that are robust to the assumption of a multivariate normal distribution or methods that are robust to certain types of outliers. Instead of using exact theory based on the multivariate normal distribution, the simpler and more applicable large sample theory is given.  The text develops among the first practical robust regression and robust multivariate location and dispersion estimators backed by theory.   The robust techniques  are illustrated for methods such as principal component analysis, canonical correlation analysis, and factor analysis.  A simple way to bootstrap confidence regions is also provided. Much of the research on robust multivariate analysis in this book is being published for the first time. The text is suitable for a first course in Multivariate Statistical Analysis or a first course in Robust Statistics. This graduate text is also useful for people who are familiar with the traditional multivariate topics, but want to know more about handling data sets with...

  18. Validace HPLC metody stanovení piroxikamu v plasmě s využitím SPME a deproteinace

    OpenAIRE

    Kuželová, Kristýna

    2015-01-01

    Validation of HPLC evaluatoin of piroxicam in plasma using SPME and precipitation Rigorous Thesis Mgr. Kristýna Kuželová Charles University in Prague, Faculty of Pharmacy in Hradec Kralove, Department of Pharmaceutical Chemistry and Drug Control, Heyrovského 1203, Hradec Králové The purpose of this thesis was bioanalytical evalution of piroxicam using High Performance Liquid Chromatagraphy (HPLC). Piroxicam was isolated from plasma using SPME and protein precipitacion. Plasma was adjusted to ...

  19. HS-SPME AS AN EFFICIENT TOOL FOR DISCRIMINATING CHEMOTYPES OF Lippia alba (Mill. N. E. Brown

    Directory of Open Access Journals (Sweden)

    Aiêrta C. C. da Silva

    Full Text Available Lippia alba (Mill. N. E. Brown (Verbenaceae is a medicinal plant for which several biological activities are reported, such as sedative, anxiolytic, anti-ulcer, antifungal, antimicrobial, antioxidant, antispasmodic, anti-nociceptive and anti-inflammatory. It is characterized by the production of essential oils which have been used to classify the plant in different chemotypes. In the Northeast region of Brazil, the presence of three chemotypes are reported: myrcene-citral (chemotype I, limonene-citral (chemotype II and carvone-limonene (chemotype III. In this work, headspace-solid phase microextraction (HS-SPME was used on the analysis of the volatile organic compounds (VOCs of three chemotypes of L. alba from the Northeast region of Brazil, and compared to the essential oils of the plants extracted by hydrodistillation. Volatile compounds from each chemotype were more effectively differentiated when extracted by HS-SPME than by hydrodistillation.

  20. Extraction with SPME and Synthesis of 2-Methyl-6-vinylpyrazine by a ‘One Pot’ Reaction Using Microwaves

    Directory of Open Access Journals (Sweden)

    René Arzuffi

    2009-06-01

    Full Text Available A synthesis of 2-methyl-6-vinylpyrazine was carried out by way of a ‘one pot’ reaction. In order to establish the efficiency of this synthesis the extraction of the volatiles released by male papaya fruit flies was performed by SPME (solid phase micro-extraction. The compound was separated and identified using GC/MSD (gas chromatography/mass spectrometry detector.

  1. Elucidating the sorption mechanism of “mixed-mode” SPME using the basic drug amphetamine as a model compound

    International Nuclear Information System (INIS)

    Peltenburg, Hester; Groothuis, Floris A.; Droge, Steven T.J.; Bosman, Ingrid J.; Hermens, Joop L.M.

    2013-01-01

    Graphical abstract: -- Highlights: •C18/propylsulfonic acid “mixed-mode” SPME fiber is efficient in sampling amphetamine. •Both protonated and neutral species of amphetamine sorb to the mixed-mode fiber. •Sorption of organic cations to this mixed-mode fiber depends on pH and salinity. •Amphetamine has a 20× higher affinity to the mixed-mode coating than to polyacrylate. -- Abstract: We studied the sorption of amphetamine as a model drug to represent small, polar organic cations to a new SPME coating combining C18 and propylsulfonic acid. This combination of hydrophobic and strong cation exchange (SCX) groups was compared to conventional SPME fibers with polyacrylate (PA) or C18 coating. The affinity of amphetamine at physiological pH (PBS) was 20 to 180 times greater for the new C18/SCX coating than for C18 alone and PA of different coating thickness. As amphetamine is a base and >99% protonated at physiological pH, this enhanced affinity is attributed to the ion-exchange phase in the coating. Tests at pH above the pK a of amphetamine show that, when normalized to the coating volume, neutral amphetamine also has a higher affinity compared to PA. As ion-exchange groups are not unlimitedly present in the coating, amphetamine isotherms level off to a saturation concentration on the C18/SCX fiber at the highest tested aqueous concentrations. Also, other cations (Na + , K + , Ca 2+ ) compete for the SCX sites and decrease the sorption coefficients, e.g. by 1.7 log units when comparing Milli-Q water with PBS. The C18/SCX fiber provides improved sensitivity over some of the classic SPME fibers. However, care should be taken near the cation exchange capacity of the fiber and the fiber should be calibrated in an appropriate matrix so as to eliminate competition effects

  2. Robustness of Structures

    DEFF Research Database (Denmark)

    Faber, Michael Havbro; Vrouwenvelder, A.C.W.M.; Sørensen, John Dalsgaard

    2011-01-01

    In 2005, the Joint Committee on Structural Safety (JCSS) together with Working Commission (WC) 1 of the International Association of Bridge and Structural Engineering (IABSE) organized a workshop on robustness of structures. Two important decisions resulted from this workshop, namely...... ‘COST TU0601: Robustness of Structures’ was initiated in February 2007, aiming to provide a platform for exchanging and promoting research in the area of structural robustness and to provide a basic framework, together with methods, strategies and guidelines enhancing robustness of structures...... the development of a joint European project on structural robustness under the COST (European Cooperation in Science and Technology) programme and the decision to develop a more elaborate document on structural robustness in collaboration between experts from the JCSS and the IABSE. Accordingly, a project titled...

  3. A Headspace Solid Phase Microextraction (HS-SPME method for the chromatographic determination of alkylpyrazines in cocoa samples

    Directory of Open Access Journals (Sweden)

    Pini Gláucia F.

    2004-01-01

    Full Text Available A Headspace Solid Phase Microextraction (HS-SPME procedure for isolation and determination of alkylpyrazines in cocoa liquor, using Gas Chromatography with Flame Ionization Detection (GC-FID for the separation and detection of the analytes, is presented here. The HS-SPME operational conditions were optimized using extractions of samples spiked with known amounts of alkylpyrazines typically found on cocoa products. The maximum extraction efficiency was obtained using SPME fibers coated with 65 µm Carbowax/divinylbenzene. Additionally, the best results were achieved with extraction temperature of 60 ºC, 15 min of sample/headspace equilibration time and 45 min extraction time. It was also observed that suspending the samples in saturated aqueous NaCl solution during extractions resulted in a significant increment on the peak areas. This procedure was found to be effective to determine the so-called pyrazinic ratios (quotient between peak areas of alkylpyrazines, which are useful as quality parameters for cocoa liquor.

  4. Analysis of Volatile Markers for Virgin Olive Oil Aroma Defects by SPME-GC/FID: Possible Sources of Incorrect Data.

    Science.gov (United States)

    Oliver-Pozo, Celia; Aparicio-Ruiz, Ramón; Romero, Inmaculada; García-González, Diego L

    2015-12-09

    The need to explain virgin olive oil (VOO) aroma descriptors by means of volatiles has raised interest in applying analytical techniques for trapping and quantitating volatiles. Static headspace sampling with solid phase microextraction (SPME) as trapping material is one of the most applied solutions for analyzing volatiles. The use of an internal standard and the determination of the response factors of the main volatiles seem to guarantee the correct determination of volatile concentrations in VOOs by SPME-GC/FID. This paper, however, shows that the competition phenomena between volatiles in their adsorption to the SPME fiber, inherent in static headspace sampling, may affect the quantitation. These phenomena are more noticeable in the particular case of highly odorant matrices, such as rancid and vinegary VOOs with high intensity of defect. The competition phenomena can modify the measurement sensitivity, which can be observed in volatile quantitation as well as in the recording of internal standard areas in different matrices. This paper analyzes the bias of the peak areas and concentrations of those volatiles that are markers for each sensory defect of VOOs (rancid, vinegary, musty, and fusty) when the intensity and complexity of aroma are increased. Of the 17 volatile markers studied in this work, 10 presented some anomalies in the quantitation in highly odorant matrices due the competition phenomena. However, quantitation was not affected in the concentration ranges at which each volatile marker is typically found in the defective oils they were characteristic of, validating their use as markers.

  5. Essential oil from Rhaponticum acaule L. roots: Comparative study using HS-SPME/GC/GC–MS and hydrodistillation techniques

    Directory of Open Access Journals (Sweden)

    Batoul Benyelles

    2014-12-01

    Full Text Available The composition of essential oil extracted from Rhaponticum acaule L. roots growing wild in Algeria was studied by hydrodistillation (HD and by Head-Space Solid Phase Micro-Extraction (HS-SPME. Quantitative but not qualitative differences have been found in the chemical composition of both analysed samples depending on the extraction method. However, the oil obtained from R. acaule roots shows that aliphatic alcohols were found to be the major class (69.2%, followed by the terpenes (5.5%, alkenes (5.2% and alkynes (4.0%. In both cases the analysis were carried out using Gas Chromatography (GC and Gas Chromatography–Mass Spectrometry (GC–MS. Our study shows that HS-SPME extraction could be considered as an alternative technique for the isolation of volatiles from plant. 25 components were identified in oil vs. 39 in the HS-SPME. However the oil composition of roots was mainly represented by a variety of aliphatic hydrocarbons (alcohols, aldehydes and ketones and terpenes which are known for their antimicrobial activities.

  6. Development of a Direct Headspace Collection Method from Arabidopsis Seedlings Using HS-SPME-GC-TOF-MS Analysis

    Directory of Open Access Journals (Sweden)

    Kazuki Saito

    2013-04-01

    Full Text Available Plants produce various volatile organic compounds (VOCs, which are thought to be a crucial factor in their interactions with harmful insects, plants and animals. Composition of VOCs may differ when plants are grown under different nutrient conditions, i.e., macronutrient-deficient conditions. However, in plants, relationships between macronutrient assimilation and VOC composition remain unclear. In order to identify the kinds of VOCs that can be emitted when plants are grown under various environmental conditions, we established a conventional method for VOC profiling in Arabidopsis thaliana (Arabidopsis involving headspace-solid-phase microextraction-gas chromatography-time-of-flight-mass spectrometry (HS-SPME-GC-TOF-MS. We grew Arabidopsis seedlings in an HS vial to directly perform HS analysis. To maximize the analytical performance of VOCs, we optimized the extraction method and the analytical conditions of HP-SPME-GC-TOF-MS. Using the optimized method, we conducted VOC profiling of Arabidopsis seedlings, which were grown under two different nutrition conditions, nutrition-rich and nutrition-deficient conditions. The VOC profiles clearly showed a distinct pattern with respect to each condition. This study suggests that HS-SPME-GC-TOF-MS analysis has immense potential to detect changes in the levels of VOCs in not only Arabidopsis, but other plants grown under various environmental conditions.

  7. Determination of tetrachloroethylene and other volatile halogenated organic compounds in oil wastes by headspace SPME GC-MS

    Energy Technology Data Exchange (ETDEWEB)

    Fabbri, D.; Bezzi, R.; Torri, C.; Galletti, P.; Tagliavini, E. [Bologna Univ., Ravenna (Italy). Lab. of Chemistry, C.I.R.S.A

    2007-09-15

    Oil wastes and slops are complex mixtures of hydrocarbons, which may contain a variety of contaminants including tetrachloroethylene (perchloroethylene, PCE) and other volatile halogenated organic compounds (VHOCs). The analytical determination of PCE at trace levels in petroleum-derived matrices is difficult to carry out in the presence of large amounts of hydrocarbon matrix components. In the following study, we demonstrate that headspace solid-phase microextraction (HS-SPME) combined with GC-MS analysis can be applied for the rapid measurement of PCE concentration in oil samples. The HS-SPME method was developed using liquid paraffin as matrix matching reference material for external and internal calibration and optimisation of experimental parameters. The limit of quantitation was 0.05 mg kg{sup -1}, and linearity was established up to 25 mg kg{sup -1}. The HS-SPME method was extended to several VHOCs, including trichloroethylene (TCE) in different matrices and was applied to the quantitative analysis of PCE and TCE in real samples.

  8. Nanoparticle-Incorporated PDMS Film as an Improved Performance SPME Fiber for Analysis of Volatile Components of Eucalyptus Leaf

    Directory of Open Access Journals (Sweden)

    Parviz Aberoomand Azar

    2013-01-01

    Full Text Available A new fabrication strategy was proposed to prepare polydimethylsiloxane (PDMS- coated solid-phase microextraction (SPME on inexpensive and unbreakable Cu fiber. PDMS was covalently bonded to the Cu substrate using self-assembled monolayer (SAM of (3-mercaptopropyltrimethoxysilane (3MPTS as binder. To increase the performance of the fiber, the incorporation effect of some nanomaterials including silica nanoparticles (NPs, carbon nanotubes (CNTs, and carboxylated carbon nanotubes (CNT-COOH to PDMS coating was compared. The surface morphology of the prepared fibers was characterized by scanning electron microscopy (SEM, and their applicability was evaluated through the extraction of some volatile organic compounds (VOCs of Eucalyptus leaf in headspace mode, and parameters affecting the extraction efficiency including extraction temperature and extraction time were optimized. Extracted compounds were analyzed by GC-MS instrument. The results obtained indicated that prepared fibers have some advantages relative to previously prepared SPME fibers, such as higher thermal stability and improved performance of the fiber. Also, results showed that SPME is a fast, simple, quick, and sensitive technique for sampling and sample introduction of Eucalyptus VOCs.

  9. Robust Growth Determinants

    OpenAIRE

    Doppelhofer, Gernot; Weeks, Melvyn

    2011-01-01

    This paper investigates the robustness of determinants of economic growth in the presence of model uncertainty, parameter heterogeneity and outliers. The robust model averaging approach introduced in the paper uses a flexible and parsi- monious mixture modeling that allows for fat-tailed errors compared to the normal benchmark case. Applying robust model averaging to growth determinants, the paper finds that eight out of eighteen variables found to be significantly related to economic growth ...

  10. Robust Programming by Example

    OpenAIRE

    Bishop , Matt; Elliott , Chip

    2011-01-01

    Part 2: WISE 7; International audience; Robust programming lies at the heart of the type of coding called “secure programming”. Yet it is rarely taught in academia. More commonly, the focus is on how to avoid creating well-known vulnerabilities. While important, that misses the point: a well-structured, robust program should anticipate where problems might arise and compensate for them. This paper discusses one view of robust programming and gives an example of how it may be taught.

  11. SPME-GC-MS analysis of commercial henna samples (Lawsonia inermis L.).

    Science.gov (United States)

    Mengoni, Tamara; Peregrina, Dolores Vargas; Censi, Roberta; Cortese, Manuela; Ricciutelli, Massimo; Maggi, Filippo; Di Martino, Piera

    2016-01-01

    The aim of this work was to provide a characterisation of volatile constituents from different commercial batches of henna (Lawsonia inermis) leaves of different geographic origin. Headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was used for the purpose. A total of 72 components were identified by GC-MS in the headspace of different henna samples which proved to differ considerably from each other, because they were characterised by different classes of components, mainly aliphatic compounds (9.0-64.7%), terpenoids (5.8-45.5%) and aromatics (7.9-45.2%), with alkanes (0.9-18.5%), aldehydes (2.1-18.8%) and carboxylic acids (3.1-29.3%), monoterpenes (3.4-30.0%) and sesquiterpenes (0.8-23.7%) and phenyl propanoids (0.6-43.1%), being the most abundant, respectively. Major representatives of these groups were n-hexadecane (0.5-4.7%), (2E)-hexenal (0.5-11.7%) and acetic acid (2.8-24.5%), limonene (0.8-14.7%), carvol (3.8-7.1%), geranyl acetone (1.4-7.9%) and (E)-caryophyllene (3.3-8.4%), and (E)-anethole (0.6-35.0%), respectively. We assume that factors such as the manufacturing process, the storage conditions and the different geographic origin of the samples may contribute to such variability.

  12. Determination of Sesquiterpenes in Wines by HS-SPME Coupled with GC-MS

    Directory of Open Access Journals (Sweden)

    Fabrizio Cincotta

    2015-07-01

    Full Text Available The sesquiterpene compounds present in red wines were characterized and quantified by Headspace Solid-Phase Microextraction in combination with Gas Chromatography–Mass Spectrometry (HS-SPME-GC-MS. Sixteen sesquiterpenes were identified, mainly hydrocarbons but also derived oxygenated compounds. Sesquiterpenes were acyclic, monocyclic, byciclic and tryciclic. Sesquiterpenes were detected in SIM (selected ion monitoring mode using their characteristics ions. All the sesquiterpenes were identified by mass spectral data, linear retention indices (LRI, literature data and injection of standards where available. Quantitative results were obtained using the method of standard additions. The method showed an average LOD = 0.05 µg L−1 and LOQ = 0.15 µg L−1. The monocyclic sesquiterpene with the germacrene skeleton, Germacrene D and the bicyclic sesquiterpene with the muurolane skeleton, α-muurolene were present in all the wine samples analysed. Syrah wines were the samples richest in sesquiterpenes in agreement with their typical spicy and woody notes. The results evidenced the possibility to use sesquiterpenes for wine authenticity and traceability.

  13. Analysis of Five Earthy-Musty Odorants in Environmental Water by HS-SPME/GC-MS

    Directory of Open Access Journals (Sweden)

    Zhen Ding

    2014-01-01

    Full Text Available The pressing issue of earthy and musty odor compounds in natural waters, which can affect the organoleptic properties of drinking water, makes it a public health concern. A simple and sensitive method for simultaneous analysis of five odorants in environmental water was developed by headspace solid-phase microextraction (HS-SPME coupled to chromatography-mass spectrometry (GC-MS, including geosmin (GSM and 2-methylisoborneol (2-MIB, as well as dimethyl trisulfide (DMTS, β-cyclocitral, and β-ionone. Based on the simple modification of original magnetic stirrer purchased from CORNING (USA, the five target compounds can be separated within 23 min, and the calibration curves show good linearity with a correlation coefficient above 0.999 (levels = 5. The limits of detection (LOD are all below 1.3 ng L−1, and the relative standard deviation (%RSD is between 4.4% and 9.9% (n = 7 and recoveries of the analytes from water samples are between 86.2% and 112.3%. In addition, the storage time experiment indicated that the concentrations did not change significantly for GSM and 2-MIB if they were stored in canonical environment. In conclusion, the method in this study could be applied for monitoring these five odorants in natural waters.

  14. Fingerprint of volatiles from plant extracts based on SPME-GC-MS

    Directory of Open Access Journals (Sweden)

    Ezequias P. Siqueira

    Full Text Available The Laboratory of Chemistry of Natural Products has an ex situ collection of extracts from organisms of the biodiversity aiming at bioprospecting. Nowadays the collection has about 4000 extracts from 1000 different species. Extracts are used to identify new bioactive compounds that could be useful for developing new drugs against neglected diseases like leishmaniosis, Chagas disease, malaria and tuberculosis. After biologic assays, the bioactive extracts need to be prepared in larger quantity to allow isolation and characterization of the bioactive component. At this time, it is important to not only confirm the bioactivity of new extract but also check if its composition is similar to the old one. It was evaluated the ability of Solid Phase Microextraction and Gas Chromatography-Mass Spectrometry analysis (SPME-GC-MS. It was used the AMDIS (Automatic Mass Spectral Deconvolution and Identification System software as tools to collect and to compare the chromatographic profiles of each extract (fingerprint. Forty six samples were analyzed, it was possible to infer from the composition of each sample and common compounds. Nine groups of samples, collected at different time, were analyzed and seasonal modifications between then could be elucidated. The results showed that this methodology can be used to monitor the composition of extracts, allowing to monitor chemical changes that may occur during storage periods and to investigate the occurrence of a determined component in different extracts.

  15. ANALYTICAL APPROACH OF THE VOLATILE FRACTION OF Solanum quitoense BY HS-SPME/GC-MS

    Directory of Open Access Journals (Sweden)

    EDUARDO CORPAS IGUARÁN

    2017-07-01

    Full Text Available The species of lulo fruit (Solanum quitoense, predominant in Colombia, is a promising fruit for both national and international market due to its flavor and nutritional characteristics, which generated the interest to know the volatile composition of its pulp. After adjusting, the chromatographic conditions necessary to analyze volatile fraction of this fruit, the effect of the temperature and time of adsorption was measured through the headspace - solid phase microextraction (HS-SPME and gas chromatography - mass spectrometry (GC-MS, on the area of volatile compounds of S. quitoense, by applying the experimental design of a factor. The descriptive analysis suggested that the adsorption at 60°C and 30 minutes promoted optimal recovery of volatiles as well as internal standard (1-Octanol, with recovery of 99,66% at 60ºC, while the non-parametric test Kruskal-Wallis showed statistical differences in the effect of time (P= 0,018, but not of the temperature adsorption (P= 0,058 upon the volatiles compounds area. A predominance of esters (48,98%, aldehydes (18,37%, and alcohols (14,29% was observed and also were found compounds of greatest area such as 3-hexen-1-ol acetate, acetic acid methyl ester, and acetic acid hexyl ester. These metabolites determine the characteristic aroma from lulo pulp and influence the consumer preference.

  16. Volatile emerging contaminants in melon fruits, analysed by HS-SPME-GC-MS.

    Science.gov (United States)

    Cincotta, Fabrizio; Verzera, Antonella; Tripodi, Gianluca; Condurso, Concetta

    2018-03-01

    The aim of this research was to develop and validate a headspace-solid phase micro-extraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) method for the determination of volatile emerging contaminants in fruit. The method showed good precision (RSD ≤ 14%) and satisfactory recoveries (99.1-101.7%) and LOD and LOQ values ranging between 0.011-0.033 μg kg -1 and 0.037-0.098 μg kg -1 , respectively. The method was applied to investigate the content of volatile emerging contaminants in two varieties of melon fruit (Cucumis melo L.) cultivated adjoining high-risk areas. Glycol ethers, BHT, BHA and BTEX (benzene, toluene, ethylbenzene and xylene) were determined in melon fruit pulps for the first time, with different sensitivities depending on sample and variety. Although the amount of the volatile contaminants in the melon samples were in the order of µg kg -1 , the safety of vegetable crops cultivated near risk areas should be more widely considered. The results showed that this accurate and reproducible method can be useful for routine safety control of fruits and vegetables.

  17. Authenticity of raspberry flavor in food products using SPME-chiral-GC-MS.

    Science.gov (United States)

    Hansen, Anne-Mette S; Frandsen, Henrik L; Fromberg, Arvid

    2016-05-01

    A fast and simple method for authenticating raspberry flavors from food products was developed. The two enantiomers of the compound (E)-α-ionone from raspberry flavor were separated on a chiral gas chromatographic column. Based on the ratio of these two enantiomers, the naturalness of a raspberry flavor can be evaluated due to the fact that a natural flavor will consist almost exclusively of the R enantiomer, while a chemical synthesis of the same compound will result in a racemic mixture. Twenty-seven food products containing raspberry flavors where investigated using SPME-chiral-GC-MS. We found raspberry jam, dried raspberries, and sodas declared to contain natural aroma all contained almost only R-(E)-α-ionone supporting the content of natural raspberry aroma. Six out of eight sweets tested did not indicate a content of natural aroma on the labeling which was in agreement with the almost equal distribution of the R and S isomer. Two products were labeled to contain natural raspberry flavors but were found to contain almost equal amounts of both enantiomers indicating a presence of synthetic raspberry flavors only. Additionally, two products that were labeled to contain both raspberry juice and flavor showed equal amounts of both enantiomers, indicating the presence of synthetic flavor.

  18. Study of flavour compounds from orange juices by HS-SPME and GC-MS

    Science.gov (United States)

    Schmutzer, G.; Avram, V.; Covaciu, F.; Feher, I.; Magdas, A.; David, L.; Moldovan, Z.

    2013-11-01

    The flavour of the orange juices, which gives the taste and odour of the product, is an important criterion about the products quality for consumers. A fresh single strength and two commercial orange juices (obtained from concentrate) flavour profile were studied using a selective and sensitive gas chromatography - mass spectrometry (GC-MS) analytical system, after a solvent free, single step preconcentration and extraction technique, the headspace solid phase microextraction (HP-SPME). In the studied orange juices 55 flavour compounds were detected and classified as belonging to the esters, alcohols, ketones, monoterpenes and sesquiterpenes chemical families. The fresh single strength orange juice was characterized by high amount of esters, monoterpenes and sesquiterpenes. Limonene and valencene were the most abundant flavours in this fresh natural orange juice. Alcohols and ketones were found in higher concentration in the commercial orange juices made from concentrate, than in the single strength products. Nevertheless, in commercial juices the most abundant flavour was limonene and α-terpineol. The results highlight clear differences between fresh singles strength orange juice and juice from concentrate. The orange juices reconstructed from concentrate, made in Romania, present low quantity of flavour compounds, suggesting the absence or a low rearomatization process, but extraneous components were not detected.

  19. Robust procedures in chemometrics

    DEFF Research Database (Denmark)

    Kotwa, Ewelina

    properties of the analysed data. The broad theoretical background of robust procedures was given as a very useful supplement to the classical methods, and a new tool, based on robust PCA, aiming at identifying Rayleigh and Raman scatters in excitation-mission (EEM) data was developed. The results show...

  20. Robustness Beamforming Algorithms

    Directory of Open Access Journals (Sweden)

    Sajad Dehghani

    2014-04-01

    Full Text Available Adaptive beamforming methods are known to degrade in the presence of steering vector and covariance matrix uncertinity. In this paper, a new approach is presented to robust adaptive minimum variance distortionless response beamforming make robust against both uncertainties in steering vector and covariance matrix. This method minimize a optimization problem that contains a quadratic objective function and a quadratic constraint. The optimization problem is nonconvex but is converted to a convex optimization problem in this paper. It is solved by the interior-point method and optimum weight vector to robust beamforming is achieved.

  1. Robustness Metrics: Consolidating the multiple approaches to quantify Robustness

    DEFF Research Database (Denmark)

    Göhler, Simon Moritz; Eifler, Tobias; Howard, Thomas J.

    2016-01-01

    robustness metrics; 3) Functional expectancy and dispersion robustness metrics; and 4) Probability of conformance robustness metrics. The goal was to give a comprehensive overview of robustness metrics and guidance to scholars and practitioners to understand the different types of robustness metrics...

  2. Robustness of Structures

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard

    2008-01-01

    This paper describes the background of the robustness requirements implemented in the Danish Code of Practice for Safety of Structures and in the Danish National Annex to the Eurocode 0, see (DS-INF 146, 2003), (DS 409, 2006), (EN 1990 DK NA, 2007) and (Sørensen and Christensen, 2006). More...... frequent use of advanced types of structures with limited redundancy and serious consequences in case of failure combined with increased requirements to efficiency in design and execution followed by increased risk of human errors has made the need of requirements to robustness of new structures essential....... According to Danish design rules robustness shall be documented for all structures in high consequence class. The design procedure to document sufficient robustness consists of: 1) Review of loads and possible failure modes / scenarios and determination of acceptable collapse extent; 2) Review...

  3. Robustness of structures

    DEFF Research Database (Denmark)

    Vrouwenvelder, T.; Sørensen, John Dalsgaard

    2009-01-01

    After the collapse of the World Trade Centre towers in 2001 and a number of collapses of structural systems in the beginning of the century, robustness of structural systems has gained renewed interest. Despite many significant theoretical, methodical and technological advances, structural...... of robustness for structural design such requirements are not substantiated in more detail, nor have the engineering profession been able to agree on an interpretation of robustness which facilitates for its uantification. A European COST action TU 601 on ‘Robustness of structures' has started in 2007...... by a group of members of the CSS. This paper describes the ongoing work in this action, with emphasis on the development of a theoretical and risk based quantification and optimization procedure on the one side and a practical pre-normative guideline on the other....

  4. Robust Approaches to Forecasting

    OpenAIRE

    Jennifer Castle; David Hendry; Michael P. Clements

    2014-01-01

    We investigate alternative robust approaches to forecasting, using a new class of robust devices, contrasted with equilibrium correction models. Their forecasting properties are derived facing a range of likely empirical problems at the forecast origin, including measurement errors, implulses, omitted variables, unanticipated location shifts and incorrectly included variables that experience a shift. We derive the resulting forecast biases and error variances, and indicate when the methods ar...

  5. Robustness - theoretical framework

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Rizzuto, Enrico; Faber, Michael H.

    2010-01-01

    More frequent use of advanced types of structures with limited redundancy and serious consequences in case of failure combined with increased requirements to efficiency in design and execution followed by increased risk of human errors has made the need of requirements to robustness of new struct...... of this fact sheet is to describe a theoretical and risk based framework to form the basis for quantification of robustness and for pre-normative guidelines....

  6. Qualitative Robustness in Estimation

    Directory of Open Access Journals (Sweden)

    Mohammed Nasser

    2012-07-01

    Full Text Available Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Times New Roman","serif";} Qualitative robustness, influence function, and breakdown point are three main concepts to judge an estimator from the viewpoint of robust estimation. It is important as well as interesting to study relation among them. This article attempts to present the concept of qualitative robustness as forwarded by first proponents and its later development. It illustrates intricacies of qualitative robustness and its relation with consistency, and also tries to remove commonly believed misunderstandings about relation between influence function and qualitative robustness citing some examples from literature and providing a new counter-example. At the end it places a useful finite and a simulated version of   qualitative robustness index (QRI. In order to assess the performance of the proposed measures, we have compared fifteen estimators of correlation coefficient using simulated as well as real data sets.

  7. Comparison of Spot and Time Weighted Averaging (TWA Sampling with SPME-GC/MS Methods for Trihalomethane (THM Analysis

    Directory of Open Access Journals (Sweden)

    Don-Roger Parkinson

    2016-02-01

    Full Text Available Water samples were collected and analyzed for conductivity, pH, temperature and trihalomethanes (THMs during the fall of 2014 at two monitored municipal drinking water source ponds. Both spot (or grab and time weighted average (TWA sampling methods were assessed over the same two day sampling time period. For spot sampling, replicate samples were taken at each site and analyzed within 12 h of sampling by both Headspace (HS- and direct (DI- solid phase microextraction (SPME sampling/extraction methods followed by Gas Chromatography/Mass Spectrometry (GC/MS. For TWA, a two day passive on-site TWA sampling was carried out at the same sampling points in the ponds. All SPME sampling methods undertaken used a 65-µm PDMS/DVB SPME fiber, which was found optimal for THM sampling. Sampling conditions were optimized in the laboratory using calibration standards of chloroform, bromoform, bromodichloromethane, dibromochloromethane, 1,2-dibromoethane and 1,2-dichloroethane, prepared in aqueous solutions from analytical grade samples. Calibration curves for all methods with R2 values ranging from 0.985–0.998 (N = 5 over the quantitation linear range of 3–800 ppb were achieved. The different sampling methods were compared for quantification of the water samples, and results showed that DI- and TWA- sampling methods gave better data and analytical metrics. Addition of 10% wt./vol. of (NH42SO4 salt to the sampling vial was found to aid extraction of THMs by increasing GC peaks areas by about 10%, which resulted in lower detection limits for all techniques studied. However, for on-site TWA analysis of THMs in natural waters, the calibration standard(s ionic strength conditions, must be carefully matched to natural water conditions to properly quantitate THM concentrations. The data obtained from the TWA method may better reflect actual natural water conditions.

  8. Quantification of transformation products of rocket fuel unsymmetrical dimethylhydrazine in soils using SPME and GC-MS.

    Science.gov (United States)

    Bakaikina, Nadezhda V; Kenessov, Bulat; Ul'yanovskii, Nikolay V; Kosyakov, Dmitry S

    2018-07-01

    Determination of transformation products (TPs) of rocket fuel unsymmetrical dimethylhydrazine (UDMH) in soil is highly important for environmental impact assessment of the launches of heavy space rockets from Kazakhstan, Russia, China and India. The method based on headspace solid-phase microextraction (HS SPME) and gas chromatography-mass spectrometry is advantageous over other known methods due to greater simplicity and cost efficiency. However, accurate quantification of these analytes using HS SPME is limited by the matrix effect. In this research, we proposed using internal standard and standard addition calibrations to achieve proper combination of accuracies of the quantification of key TPs of UDMH and cost efficiency. 1-Trideuteromethyl-1H-1,2,4-triazole (MTA-d3) was used as the internal standard. Internal standard calibration allowed controlling matrix effects during quantification of 1-methyl-1H-1,2,4-triazole (MTA), N,N-dimethylformamide (DMF), and N-nitrosodimethylamine (NDMA) in soils with humus content < 1%. Using SPME at 60 °C for 15 min by 65 µm Carboxen/polydimethylsiloxane fiber, recoveries of MTA, DMF and NDMA for sandy and loamy soil samples were 91-117, 85-123 and 64-132%, respectively. For improving the method accuracy and widening the range of analytes, standard addition and its combination with internal standard calibration were tested and compared on real soil samples. The combined calibration approach provided greatest accuracies for NDMA, DMF, N-methylformamide, formamide, 1H-pyrazole, 3-methyl-1H-pyrazole and 1H-pyrazole. For determination of 1-formyl-2,2-dimethylhydrazine, 3,5-dimethylpyrazole, 2-ethyl-1H-imidazole, 1H-imidazole, 1H-1,2,4-triazole, pyrazines and pyridines, standard addition calibration is more suitable. However, the proposed approach and collected data allow using both approaches simultaneously. Copyright © 2018 Elsevier B.V. All rights reserved.

  9. A quantitative approach for pesticide analysis in grape juice by direct interfacing of a matrix compatible SPME phase to dielectric barrier discharge ionization-mass spectrometry.

    Science.gov (United States)

    Mirabelli, Mario F; Gionfriddo, Emanuela; Pawliszyn, Janusz; Zenobi, Renato

    2018-02-12

    We evaluated the performance of a dielectric barrier discharge ionization (DBDI) source for pesticide analysis in grape juice, a fairly complex matrix due to the high content of sugars (≈20% w/w) and pigments. A fast sample preparation method based on direct immersion solid-phase microextraction (SPME) was developed, and novel matrix compatible SPME fibers were used to reduce in-source matrix suppression effects. A high resolution LTQ Orbitrap mass spectrometer allowed for rapid quantification in full scan mode. This direct SPME-DBDI-MS approach was proven to be effective for the rapid and direct analysis of complex sample matrices, with limits of detection in the parts-per-trillion (ppt) range and inter- and intra-day precision below 30% relative standard deviation (RSD) for samples spiked at 1, 10 and 10 ng ml -1 , with overall performance comparable or even superior to existing chromatographic approaches.

  10. Headspace solid-phase microextraction (HS-SPME) and liquid-liquid extraction (LLE): comparison of the performance in classification of ecstasy tablets. Part 2.

    Science.gov (United States)

    Bonadio, Federica; Margot, Pierre; Delémont, Olivier; Esseiva, Pierre

    2008-11-20

    Headspace solid-phase microextraction (HS-SPME) is assessed as an alternative to liquid-liquid extraction (LLE) currently used for 3,4-methylenedioxymethampethamine (MDMA) profiling. Both methods were compared evaluating their performance in discriminating and classifying samples. For this purpose 62 different seizures were analysed using both extraction techniques followed by gas chromatography-mass spectroscopy (GC-MS). A previously validated method provided data for HS-SPME, whereas LLE data were collected applying a harmonized methodology developed and used in the European project CHAMP. After suitable pre-treatment, similarities between sample pairs were studied using the Pearson correlation. Both methods enable to distinguish between samples coming from the same pre-tabletting batches and samples coming from different pre-tabletting batches. This finding emphasizes the use of HS-SPME as an effective alternative to LLE, with additional advantages such as sample preparation and a solvent-free process.

  11. Quantitation of (R)- and (S)-linalool in beer using solid phase microextraction (SPME) in combination with a stable isotope dilution assay (SIDA).

    Science.gov (United States)

    Steinhaus, Martin; Fritsch, Helge T; Schieberle, Peter

    2003-11-19

    A stable isotope dilution assay (SIDA) was developed for the quantitation of both linalool enantiomers using synthesized [2H(2)]R/S-linalool as the internal standard. For enrichment of the target compound from beer, a solid phase microextraction method (SPME) was developed. In comparison to the more time-consuming extraction/distillation cleanup of the beer samples, the results obtained by SPME/SIDA were very similar, even under nonequilibration conditions. Analysis of five different types of beer showed significant differences in the linalool concentrations, which were clearly correlated with the intensity of the hoppy aroma note as evaluated by a sensory panel. In addition, significant differences in the R/S ratios were measured in the beers. The SPME/SIDA yielded exact data independently from headspace sampling parameters, such as exposure time or ionic strength of the solution.

  12. Solid-phase microextraction (SPME) as a tool to predict the bioavailability and toxicity of pyrene to the springtail, Folsomia candida, under various soil conditions

    DEFF Research Database (Denmark)

    Styrishave, Bjarne; Mortensen, Mads; Krogh, Paul Henning

    2008-01-01

    The porewater concentrations of pyrene were estimated by a negligible depletive solid-phase microextraction (SPME) method. The effects of organic matter (OM) and soil aging on the bioavailability of pyrene in soil were investigated by generation of reproductive effect concentrations (EC50...... increased with increasing OM and aging of the soil. The increase of the OM content in the soil reduced the extractability of pyrene by SPME, as well as the toxicity of pyrene. An aging effect was demonstrated in Askov soil, EC50 values increased with increased contact time. The amounts of pyrene extracted...

  13. Robustness in econometrics

    CERN Document Server

    Sriboonchitta, Songsak; Huynh, Van-Nam

    2017-01-01

    This book presents recent research on robustness in econometrics. Robust data processing techniques – i.e., techniques that yield results minimally affected by outliers – and their applications to real-life economic and financial situations are the main focus of this book. The book also discusses applications of more traditional statistical techniques to econometric problems. Econometrics is a branch of economics that uses mathematical (especially statistical) methods to analyze economic systems, to forecast economic and financial dynamics, and to develop strategies for achieving desirable economic performance. In day-by-day data, we often encounter outliers that do not reflect the long-term economic trends, e.g., unexpected and abrupt fluctuations. As such, it is important to develop robust data processing techniques that can accommodate these fluctuations.

  14. Robust Manufacturing Control

    CERN Document Server

    2013-01-01

    This contributed volume collects research papers, presented at the CIRP Sponsored Conference Robust Manufacturing Control: Innovative and Interdisciplinary Approaches for Global Networks (RoMaC 2012, Jacobs University, Bremen, Germany, June 18th-20th 2012). These research papers present the latest developments and new ideas focusing on robust manufacturing control for global networks. Today, Global Production Networks (i.e. the nexus of interconnected material and information flows through which products and services are manufactured, assembled and distributed) are confronted with and expected to adapt to: sudden and unpredictable large-scale changes of important parameters which are occurring more and more frequently, event propagation in networks with high degree of interconnectivity which leads to unforeseen fluctuations, and non-equilibrium states which increasingly characterize daily business. These multi-scale changes deeply influence logistic target achievement and call for robust planning and control ...

  15. Robust plasmonic substrates

    DEFF Research Database (Denmark)

    Kostiučenko, Oksana; Fiutowski, Jacek; Tamulevicius, Tomas

    2014-01-01

    Robustness is a key issue for the applications of plasmonic substrates such as tip-enhanced Raman spectroscopy, surface-enhanced spectroscopies, enhanced optical biosensing, optical and optoelectronic plasmonic nanosensors and others. A novel approach for the fabrication of robust plasmonic...... substrates is presented, which relies on the coverage of gold nanostructures with diamond-like carbon (DLC) thin films of thicknesses 25, 55 and 105 nm. DLC thin films were grown by direct hydrocarbon ion beam deposition. In order to find the optimum balance between optical and mechanical properties...

  16. Robust Self Tuning Controllers

    DEFF Research Database (Denmark)

    Poulsen, Niels Kjølstad

    1985-01-01

    The present thesis concerns robustness properties of adaptive controllers. It is addressed to methods for robustifying self tuning controllers with respect to abrupt changes in the plant parameters. In the thesis an algorithm for estimating abruptly changing parameters is presented. The estimator...... has several operation modes and a detector for controlling the mode. A special self tuning controller has been developed to regulate plant with changing time delay.......The present thesis concerns robustness properties of adaptive controllers. It is addressed to methods for robustifying self tuning controllers with respect to abrupt changes in the plant parameters. In the thesis an algorithm for estimating abruptly changing parameters is presented. The estimator...

  17. Partitioning of the pesticide trifluralin between dissolved organic matter and water using automated SPME-GC/MS

    KAUST Repository

    Caupos, Emilie

    2014-10-04

    Solid-phase microextraction (SPME) was used to determine the equilibrium association constant for a pesticide, trifluralin (TFR), with dissolved organic matter (DOM). After optimization of the SPME method for the analysis of TFR, partition coefficients (K DOM) with three different sources of DOM were determined in buffered solutions at pH 7. Commercial humic acids and DOM fractions isolated from two surface waters were used. The values of log K DOMvaried from 4.3 to 5.8, depending on the nature of the organic material. A good correlation was established between log K DOMand DOM properties (as measured with the H/O atomic ratio and UV absorbance), in agreement with literature data. This is consistent with the effect of polarity and aromaticity for governing DOM-pollutant associations, regardless of the origin of DOM. This association phenomenon is relevant to better understand the behavior of pesticides in the environment since it controls part of pesticide leaching and fate in aquatic systems.

  18. Modified HS-SPME for determination of quantitative relations between low-molecular oxygen compounds in various matrices.

    Science.gov (United States)

    Dawidowicz, Andrzej L; Szewczyk, Joanna; Dybowski, Michal P

    2016-09-07

    Similar quantitative relations between individual constituents of the liquid sample established by its direct injection can be obtained applying Polydimethylsiloxane (PDMS) fiber in the headspace solid phase microextraction (HS-SPME) system containing the examined sample suspended in methyl silica oil. This paper proves that the analogous system composed of sample suspension/emulsion in polyethylene glycol (PEG) and Carbowax fiber allows to get similar quantitative relations between components of the mixture as those established by its direct analysis, but only for polar constituents. It is demonstrated for essential oil (EO) components of savory, sage, mint and thyme, and of artificial liquid mixture of polar constituents. The observed differences in quantitative relations between polar constituents estimated by both applied procedures are insignificant (Fexp < Fcrit). The presented results indicates that wider applicability of the system composed of a sample suspended in the oil of the same physicochemical character as that of used SPME fiber coating strongly depends on the character of interactions between analytes-suspending liquid and analytes-fiber coating. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. A sensitive method using SPME pre-concentration for the quantification of aromatic amines in indoor air.

    Science.gov (United States)

    Lucaire, Vincent; Schwartz, Jean-Jacques; Delhomme, Olivier; Ocampo-Torres, Ruben; Millet, Maurice

    2018-03-01

    Monitoring the levels of aliphatic and aromatic amines (AA) in indoor air is important to protect human health because of exposure to these compounds through diet and inhalation. A sampling and analytical method using XAD-2 cartridges and gas chromatography coupled to mass spectrometry used for assessing 25 AA in different smoking and non-smoking indoor environment was developed. After sampling and delivering 1 m 3 of air (6-8 h sampling), an adsorbent was ultrasonically extracted with acetonitrile, concentrated to 1 mL and diluted in 25 mL of water (pH = 9; 5% NaCl), and then extracted for 40 min at 80 °C using a divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber and injected in a GC/MS system. With this method, 22 of the 25 AA can be analyzed with detection limits up to five times lower than that of classic liquid injection. Benzylamine, 3-aminophenol, and 4-aminophenol were not detected with the solid-phase micro-extraction (SPME) method. It can be assumed that aminophenols required a derivatization step for their analysis by GC as these molecules were not detected regardless of the injection mode used. Graphical abstract Analysis of aromatic amines in indoor air by SPME-GC/MS.

  20. Using disposable solid-phase microextraction (SPME) to determine the freely dissolved concentration of polybrominated diphenyl ethers (PBDEs) in sediments

    International Nuclear Information System (INIS)

    Jia Fang; Cui Xinyi; Wang Wei; Delgado-Moreno, Laura; Gan, Jay

    2012-01-01

    Polybrominated diphenyl ethers (PBDEs) are brominated flame retardants (BFRs). The ubiquity and persistence of PBDEs in sediment have raised concerns over their environmental fate and ecological risks. Due to strong affinity for sediment organic matter, environmental fate and bioavailability of PBDEs closely depend on their phase distribution. In this study, disposable polydimethylsiloxane (PDMS) fiber was used to derive the freely dissolved concentration (C free ) of PBDEs in sediment porewater as a measurement of bioavailability. The PDMS-to-water partition coefficient (log K PDMS ) was 5.46–5.83 for BDE 47, 99, and 153. In sediments, PBDEs were predominantly sorbed to the sediment phase, with C free accounting for free of PBDEs decreased as their bromination or sediment organic carbon content increased. The strong association with dissolved organic matter (DOM) implies a potential for facilitated offsite transport and dispersion in the environment that depends closely on the stability of sediment aggregates. - Highlights: ► A disposable SPME method was developed for measuring C free of PBDEs in sediment. ► C free decreased with increasing congener bromination or sediment OC content. ► C free of PBDEs accounted for DOC values suggest a high probability for DOM-facilitated offsite transport. - A SPME method based on disposable PDMS fibers was developed for measuring the freely dissolved concentration of PBDEs (C free ) in sediment porewater.

  1. Development of an SPME-GC-MS/MS method for the determination of pesticides in rainwater: Laboratory and field experiments

    International Nuclear Information System (INIS)

    Sauret-Szczepanski, Nathalie; Mirabel, Philippe; Wortham, Henri

    2006-01-01

    A solid-phase microextraction - coupled to a gas chromatography - ion trap tandem mass spectrometry (SPME-GC-MS/MS) method was developed for the quantitative determination in rainwater of 8 pesticides amongst the most used in France and 3 triazines metabolites. The main factors affecting the SPME process were studied. Using a 3 mL sample, the method developed showed good linearity for concentrations ranging from 0.05 to 50 μg L -1 with correlation coefficients between 0.997 and 0.9999 and relative standard deviations (% RSD) below 14%. The study of matrix effects showed that rainwater was too diluted to have any significant influence on the extraction efficiency. To validate the method, a field campaign was carried out on the rain events, which occurred in Strasbourg during a one-year period. The rain concentrations showed patterns of high pesticide concentrations during spring months, which were correlated to the spraying periods of most of these substances. - Solid-phase microextraction efficiency of pesticides in rainwater was optimized

  2. Experimental design-based isotope-dilution SPME-GC/MS method development for the analysis of smoke flavouring products.

    Science.gov (United States)

    Giri, Anupam; Zelinkova, Zuzana; Wenzl, Thomas

    2017-12-01

    For the implementation of Regulation (EC) No 2065/2003 related to smoke flavourings used or intended for use in or on foods a method based on solid-phase micro extraction (SPME) GC/MS was developed for the characterisation of liquid smoke products. A statistically based experimental design (DoE) was used for method optimisation. The best general conditions to quantitatively analyse the liquid smoke compounds were obtained with a polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibre, 60°C extraction temperature, 30 min extraction time, 250°C desorption temperature, 180 s desorption time, 15 s agitation time, and 250 rpm agitation speed. Under the optimised conditions, 119 wood pyrolysis products including furan/pyran derivatives, phenols, guaiacol, syringol, benzenediol, and their derivatives, cyclic ketones, and several other heterocyclic compounds were identified. The proposed method was repeatable (RSD% <5) and the calibration functions were linear for all compounds under study. Nine isotopically labelled internal standards were used for improving quantification of analytes by compensating matrix effects that might affect headspace equilibrium and extractability of compounds. The optimised isotope dilution SPME-GC/MS based analytical method proved to be fit for purpose, allowing the rapid identification and quantification of volatile compounds in liquid smoke flavourings.

  3. Determination of Pyrethroids in Tea Brew by GC-MS Combined with SPME with Multiwalled Carbon Nanotube Coated Fiber

    Directory of Open Access Journals (Sweden)

    Dongxia Ren

    2018-01-01

    Full Text Available A new method has been developed to simultaneously determine 7 pyrethroid residues in tea brew using gas chromatography-mass spectrometry (GC-MS combined with solid phase microextraction (SPME with multiwalled carbon nanotubes (MWCNTs coated fiber. The MWCNTs coated fiber of SPME was homemade by using stainless steel wire as coating carrier and polyacrylonitrile (PAN solution as adhesive glue. Under the optimized conditions, a good linearity was shown for bifenthrin, fenpropathrin, permethrin, and cyfluthrin in 1–50 ng mL−1 and for cypermethrin, fenvalerate, and deltamethrin in 5–50 ng mL−1. The correlation coefficients were in the range of 0.9948–0.9999. The average recoveries of 7 pyrethroids were 94.2%–107.3% and the relative standard deviations (RSDs were less than 15%. The detection limit of the method ranged from 0.12 to 1.65 ng mL−1. The tea brew samples made from some commercial tea samples were analyzed. Among them, bifenthrin, fenpropathrin, and permethrin were found. The results show that the method is rapid and sensitive and requires low organic reagent consumption, which can be well used for the detection of the pyrethroids in tea brew.

  4. Determination of Pyrethroids in Tea Brew by GC-MS Combined with SPME with Multiwalled Carbon Nanotube Coated Fiber.

    Science.gov (United States)

    Ren, Dongxia; Sun, Chengjun; Ma, Guanqun; Yang, Danni; Zhou, Chen; Xie, Jiayu; Li, Yongxin

    2018-01-01

    A new method has been developed to simultaneously determine 7 pyrethroid residues in tea brew using gas chromatography-mass spectrometry (GC-MS) combined with solid phase microextraction (SPME) with multiwalled carbon nanotubes (MWCNTs) coated fiber. The MWCNTs coated fiber of SPME was homemade by using stainless steel wire as coating carrier and polyacrylonitrile (PAN) solution as adhesive glue. Under the optimized conditions, a good linearity was shown for bifenthrin, fenpropathrin, permethrin, and cyfluthrin in 1-50 ng mL -1 and for cypermethrin, fenvalerate, and deltamethrin in 5-50 ng mL -1 . The correlation coefficients were in the range of 0.9948-0.9999. The average recoveries of 7 pyrethroids were 94.2%-107.3% and the relative standard deviations (RSDs) were less than 15%. The detection limit of the method ranged from 0.12 to 1.65 ng mL -1 . The tea brew samples made from some commercial tea samples were analyzed. Among them, bifenthrin, fenpropathrin, and permethrin were found. The results show that the method is rapid and sensitive and requires low organic reagent consumption, which can be well used for the detection of the pyrethroids in tea brew.

  5. Characterization of the volatile components in green tea by IRAE-HS-SPME/GC-MS combined with multivariate analysis.

    Science.gov (United States)

    Yang, Yan-Qin; Yin, Hong-Xu; Yuan, Hai-Bo; Jiang, Yong-Wen; Dong, Chun-Wang; Deng, Yu-Liang

    2018-01-01

    In the present work, a novel infrared-assisted extraction coupled to headspace solid-phase microextraction (IRAE-HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS) was developed for rapid determination of the volatile components in green tea. The extraction parameters such as fiber type, sample amount, infrared power, extraction time, and infrared lamp distance were optimized by orthogonal experimental design. Under optimum conditions, a total of 82 volatile compounds in 21 green tea samples from different geographical origins were identified. Compared with classical water-bath heating, the proposed technique has remarkable advantages of considerably reducing the analytical time and high efficiency. In addition, an effective classification of green teas based on their volatile profiles was achieved by partial least square-discriminant analysis (PLS-DA) and hierarchical clustering analysis (HCA). Furthermore, the application of a dual criterion based on the variable importance in the projection (VIP) values of the PLS-DA models and on the category from one-way univariate analysis (ANOVA) allowed the identification of 12 potential volatile markers, which were considered to make the most important contribution to the discrimination of the samples. The results suggest that IRAE-HS-SPME/GC-MS technique combined with multivariate analysis offers a valuable tool to assess geographical traceability of different tea varieties.

  6. Passive Sampling and Analysis of Naphthalene in Internal Combustion Engine Exhaust with Retracted SPME Device and GC-MS

    Directory of Open Access Journals (Sweden)

    Nassiba Baimatova

    2017-07-01

    Full Text Available Exhaust gases from internal combustion engines are the main source of urban air pollution. Quantification of Polycyclic aromatic hydrocarbons (PAHs in the exhaust gases is needed for emissions monitoring, enforcement, development, and testing of control technologies. The objective was to develop quantification of gaseous naphthalene in diesel engine exhaust based on diffusion-controlled extraction onto a retracted solid-phase microextraction (SPME fiber coating and analysis on gas chromatography-mass spectrometry (GC-MS. Extraction of naphthalene with retracted fibers followed Fick’s law of diffusion. Extracted mass of naphthalene was proportional to Cg, t, Dg, T and inversely proportional to Z. Method detection limit (p = 0.95 was 11.5 ppb (0.06 mg·m−3 at t = 9 h, Z = 10 mm and T = 40 °C, respectively. It was found that the % mass extracted of naphthalene by SPME needle assembly depended on the type of fiber. Storage time at different temperatures did not affect analyte losses extracted by polydimethylsiloxane (PDMS 100 µm fiber. The developed method was tested on exhaust gases from idling pickup truck and tractor, and compared side-by-side with a direct injection of sampled exhaust gas method. Time-weighted average (TWA concentrations of naphthalene in exhaust gases from idling pickup truck and a tractor ranged from 0.08 to 0.3 mg·m−3 (15.3–53.7 ppb.

  7. Characterization of the volatile components in green tea by IRAE-HS-SPME/GC-MS combined with multivariate analysis.

    Directory of Open Access Journals (Sweden)

    Yan-Qin Yang

    Full Text Available In the present work, a novel infrared-assisted extraction coupled to headspace solid-phase microextraction (IRAE-HS-SPME followed by gas chromatography-mass spectrometry (GC-MS was developed for rapid determination of the volatile components in green tea. The extraction parameters such as fiber type, sample amount, infrared power, extraction time, and infrared lamp distance were optimized by orthogonal experimental design. Under optimum conditions, a total of 82 volatile compounds in 21 green tea samples from different geographical origins were identified. Compared with classical water-bath heating, the proposed technique has remarkable advantages of considerably reducing the analytical time and high efficiency. In addition, an effective classification of green teas based on their volatile profiles was achieved by partial least square-discriminant analysis (PLS-DA and hierarchical clustering analysis (HCA. Furthermore, the application of a dual criterion based on the variable importance in the projection (VIP values of the PLS-DA models and on the category from one-way univariate analysis (ANOVA allowed the identification of 12 potential volatile markers, which were considered to make the most important contribution to the discrimination of the samples. The results suggest that IRAE-HS-SPME/GC-MS technique combined with multivariate analysis offers a valuable tool to assess geographical traceability of different tea varieties.

  8. Improving the On-Line Extraction of Polar Compounds by IT-SPME with Silica Nanoparticles Modified Phases

    Directory of Open Access Journals (Sweden)

    Pascual Serra-Mora

    2018-02-01

    Full Text Available In the present work the extraction efficiency of in-tube solid-phase microextraction (IT-SPME for polar herbicides has been evaluated using extractive capillaries coated with different polymeric sorbents. For this purpose, aqueous solutions of herbicides with a wide range of polarities, including some highly polar compounds (log Kow < 1, have been directly processed by IT-SPME coupled on-line to capillary liquid chromatography with UV-diode array detection. For extraction, commercially available capillary columns coated with polydimethylsiloxane (PDMS and polyetilenglicol (PEG-based phases have been used, and the results have been compared with those obtained with a synthesized tetraethyl orthosilicate (TEOS-trimethoxyethylsilane (MTEOS polymer, as well as the same polymer reinforced with silica nanoparticles (SiO2 NPs. The SiO2 NPs functionalized TEOS-MTEOS coating provided the best results for most herbicides, especially for the most polar compounds. On the basis of the results obtained, conditions for the quantification of the herbicides tested are described using a SiO2 NPs reinforced TEOS-MTEOS coated capillary. The proposed method provided satisfactory linearity up to concentrations of 200 μg/L. The precision was also suitable, with relative standard deviations (RSDs values ≤9% (n = 3, and the limits of detection (LODs were within the 0.5–7.5 µg/L range. The method has been applied to different water samples and the extract obtained from an agricultural soil.

  9. Application of HS-SPME and GC-MS to characterization of volatile compounds emitted from Osmanthus flowers.

    Science.gov (United States)

    Deng, Chunhui; Song, Guoxin; Hu, Yaoming

    2004-12-01

    Headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) was developed for characterization of volatile compounds emitted from two varieties Osmanthus flowers of O. fragrans var. latifolius and O. fragrans var. thunbergii. The SPME parameters were studied, the optimum conditions of a 65 microm carbowax/divinylbenzene (CW/DVB), extraction temperature of 22 degrees C and extraction time of 10 min were obtained and applied to extraction of the volatile emissions. Fourteen compounds released from both varieties of Osmanthus flowers were separated and identified by GC-MS, which mainly included alpha-linalool, beta-linalool, trans-linalool oxide, cis-linalool oxide, alpha-lonone, beta-lonone, capraldehyde and decalactone. By comparing their peak areas, we found that the sums of the fourteen compounds from the two Osmanthus flowers were very close, while the relative contents of individual volatile compounds in the two emissions were very different. The relative content of alpha-linalool and beta-linalool in O. fragrans var. latifolius were 39.46% and 0.51%, while in O. fragrans var. thunbergii were 9.53% and 27.71%. Due to their different relative contents, the two varieties of flower have different fragrances.

  10. Characterisation of the volatile profile of coconut water from five varieties using an optimised HS-SPME-GC analysis.

    Science.gov (United States)

    Prades, Alexia; Assa, Rebecca Rachel Ablan; Dornier, Manuel; Pain, Jean-Pierre; Boulanger, Renaud

    2012-09-01

    Coconut (Cocos nucifera L.) water is a refreshing tropical drink whose international market has recently been growing. However, little is yet known about its physicochemical composition, particularly its aroma. This study set out to characterise the volatile profile of water from five coconut varieties. Aroma compounds were characterised by headspace solid phase microextraction gas chromatography (HS-SPME-GC) analysis. An experimental design was established to optimise SPME conditions, leading to an equilibration time of 10 min followed by an extraction time of 60 min at 50 °C. Accordingly, immature coconut water from WAT (West African Tall), PB121 (MYD × WAT Hybrid), MYD (Malayan Yellow Dwarf), EGD (Equatorial Guinea Green Dwarf) and THD (Thailand Aromatic Green Dwarf) palms was analysed and described. Ketones were mainly present in the Tall and Hybrid varieties, whereas aldehydes were most abundant in the Dwarf palms. Tall coconut water was characterised by a high lactone content. THD exhibited a high ethyl octanoate level. The cluster analysis of the volatile fraction from the five coconut cultivars was found to be related to their genetic classification. The volatile compounds of immature coconut water from five varieties were characterised for the first time. Volatile profile analysis could be a useful tool for the selection of Dwarf coconut varieties, which are mainly consumed as a beverage. Copyright © 2012 Society of Chemical Industry.

  11. Robust surgery loading

    NARCIS (Netherlands)

    Hans, Elias W.; Wullink, Gerhard; van Houdenhoven, Mark; Kazemier, Geert

    2008-01-01

    We consider the robust surgery loading problem for a hospital’s operating theatre department, which concerns assigning surgeries and sufficient planned slack to operating room days. The objective is to maximize capacity utilization and minimize the risk of overtime, and thus cancelled patients. This

  12. Robustness Envelopes of Networks

    NARCIS (Netherlands)

    Trajanovski, S.; Martín-Hernández, J.; Winterbach, W.; Van Mieghem, P.

    2013-01-01

    We study the robustness of networks under node removal, considering random node failure, as well as targeted node attacks based on network centrality measures. Whilst both of these have been studied in the literature, existing approaches tend to study random failure in terms of average-case

  13. Quantitative Analysis of Bisphenol A Leached from Household Plastics by Solid-Phase Microextraction and Gas Chromatography-Mass Spectrometry (SPME-GC-MS)

    Science.gov (United States)

    Johnson, Bettie Obi; Burke, Fernanda M.; Harrison, Rebecca; Burdette, Samantha

    2012-01-01

    The measurement of trace levels of bisphenol A (BPA) leached out of household plastics using solid-phase microextraction (SPME) with gas chromatography-mass spectrometry (GC-MS) is reported here. BPA is an endocrine-disrupting compound used in the industrial manufacture of polycarbonate plastic bottles and epoxy resin can liners. This experiment…

  14. Monitoring of persistent organic pollutants in seawater of the Pearl River Estuary with rapid on-site active SPME sampling technique

    International Nuclear Information System (INIS)

    Huang, Siming; He, Shuming; Xu, Hao; Wu, Peiyan; Jiang, Ruifen; Zhu, Fang; Luan, Tiangang; Ouyang, Gangfeng

    2015-01-01

    An on-site active solid-phase microextraction (SPME) sampling technique coupled with gas chromatography-mass spectrometry (GC–MS) for sampling and monitoring 16 polycyclic aromatic hydrocarbons (PAHs) and 8 organochlorine pesticides (OCPs) in seawater was developed. Laboratory experiments demonstrated that the sampling-rate calibration method was practical and could be used for the quantification of on-site sampling. The proposed method was employed for field tests which covered large amounts of water samples in the Pearl River Estuary in rainy and dry seasons. The on-site SPME sampling method can avoid the contamination of sample, the losses of analytes during sample transportation, as well as the usage of solvent and time-consuming sample preparation process. Results indicated that the technique with the designed device can address the requirement of modern environment water analysis. In addition, the sources, bioaccumulation and potential risk to human of the PAHs and OCPs in seawater of the Pearl River Estuary were discussed. - Highlights: • SPME on-site active sampling technique was developed and validated. • The technique was employed for field tests in the Pearl River Estuary. • 16 PAHs and 8 OCPs in the seawater of Pearl River Estuary were monitored. • The potential risk of the PAHs and OCPs in Pearl River Estuary were discussed. - An on-site active SPME sampling technique was developed and successfully applied for sampling and monitoring 16 PAHs and 8 OCPs in the Pearl River Estuary

  15. Sol-gel-based SPME fiber as a reliable sampling technique for studying biogenic volatile organic compounds released from Clostridium tetani.

    Science.gov (United States)

    Ghader, Masoud; Shokoufi, Nader; Es-Haghi, Ali; Kargosha, Kazem

    2017-11-01

    A novel and efficient headspace solid-phase microextraction (HS-SPME) method, followed by gas chromatography mass spectrometry (GC-MS), was developed to study volatile organic compounds (VOCs) emerging from microorganisms. Two homemade SPME fibers, a semi-polar poly (dimethylsiloxane) (PDMS) fiber, and a polar polyethylene glycol (PEG) fiber, along with two commercial fibers (PDMS and PDMS/DVB) were used to collect VOCs emerging from Clostridium tetani which was cultured in different media. The adsorbed VOCs were desorbed and identified, in vitro, using GC-MS. The adsorption efficiency was improved by optimizing the time duration of adsorption and desorption. About 50 components were identified by the proposed method. The main detected compounds appeared to be sulfur containing compounds such as butanethioic acid S-methyl ester, dimethyl trisulfide, and dimethyl tetrasulfide. These volatile sulfur containing compounds are derived from amino acids containing the sulfur element, which probably coexist in the mentioned bacterium or are added to the culture media. The developed HS-SPME-GC-MS method allowed the determination of the chemical fingerprint of Clostridium tetani volatile constituents, and thus provides a new, simple, and reliable tool for studying the growth of microorganisms. Graphical abstract Investigation of biogenic VOCs released from Clostridium tetani using SPME-GC-MS.

  16. Rapid sampling of BTEX in air by SPME in the city of Nice and at the Nice-Cote d'Azur airport

    International Nuclear Information System (INIS)

    Tumbiolo, S.; Gal, J.F.; Maria, P.Ch.; Laborde, P.; Teton, S.

    2006-01-01

    This article presents the results of a tentative application of Solid Phase Micro Extraction (SPME) to the analysis of BTEX (benzene, toluene, ethyl-benzene and xylenes) at the μg/m 3 level in indoor and outdoor air. The salient features of the method validation are reported. Sampling by QUALITAIR using Radiello passive samplers, was carried out from 2001 to 2004 in the city of Nice and its airport. Urban traffic impact was proved, but a link between BTX concentrations and the variations of airport activities was not clearly established. During the same period, several samplings were performed using SPME. Taking into account the short (30 minutes) sampling time, rapid changes of BTEX concentrations were evidenced, as for example the start of airplane engines. As field studies have shown, SPME technique appears as a method of choice for fast qualitative analysis and quantitative determination of Volatile Organic Compounds (VOC). The small dimensions of the SPME sampling system and the short sampling time let envisage its utilisation for the rapid diagnostic and the monitoring of indoor air quality. (author)

  17. Multivariate statistical analysis of hemlock (Tsuga) volatiles by SPME/GC/MS: insights into the phytochemistry of the hemlock woolly adelgid (Adelges tsugae Annand)

    Science.gov (United States)

    Anthony Lagalante; Frank Calvosa; Michael Mirzabeigi; Vikram Iyengar; Michael Montgomery; Kathleen Shields

    2007-01-01

    A previously developed single-needle, SPME/GC/MS technique was used to measure the terpenoid content of T. canadensis growing in a hemlock forest at Lake Scranton, PA (Lagalante and Montgomery 2003). The volatile terpenoid composition was measured over a 1-year period from June 2003 to May 2004 to follow the annual cycle of foliage development from...

  18. Selective molecularly imprinted polymer combined with restricted access material for in-tube SPME/UHPLC-MS/MS of parabens in breast milk samples

    International Nuclear Information System (INIS)

    Souza, Israel D.; Melo, Lidervan P.; Jardim, Isabel C.S.F.; Monteiro, Juliana C.S.; Nakano, Ana Marcia S.; Queiroz, Maria Eugênia C.

    2016-01-01

    A new molecularly imprinted polymer modified with restricted access material (a hydrophilic external layer), (MIP-RAM) was synthesized via polymerization in situ in an open fused silica capillary. This stationary phase was used as sorbent for in-tube solid phase microextraction (in-tube SPME) to determine parabens in breast milk samples by ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Scanning electron micrographs (SEM) illustrate MIP surface modification after glycerol dimethacrylate (hydrophilic monomer) incorporation. The interaction between parabens and MIP-RAM was investigated by Fourier-transform infrared (FTIR) spectroscopy. The Scatchard plot for MIP-RAM presented two linear parts with different slopes, illustrating binding sites with high- and low-affinity. Endogenous compounds exclusion from the MIP-RAM capillary was demonstrated by in-tube SPME/LC-UV assays carried out with blank milk samples. The in-tube SPME/UHPLC-MS/MS method presented linear range from 10 ng mL"−"1 (LLOQ) to 400 ng mL"−"1 with coefficients of determination higher than 0.99, inter-assay precision with coefficient of variation (CV) values ranging from 2 to 15%, and inter-assay accuracy with relative standard deviation (RSD) values ranging from −1% to 19%. Analytical validation parameters attested that in-tube SPME/UHPLC-MS/MS is an appropriate method to determine parabens in human milk samples to assess human exposure to these compounds. Analysis of breast milk samples from lactating women demonstrated that the proposed method is effective. - Highlights: • Molecularly imprinted polymer modified with a hydrophilic external layer (RAM-MIP) was synthesized in a silica capillary. • RAM-MIP capillary, used as sorbent for in-tube SPME, established specific interaction with parabens present in milk samples. • The matrix components that interacted only with the hydrophilic external layer (non-adsorptive network) were excluded. • The

  19. Selective molecularly imprinted polymer combined with restricted access material for in-tube SPME/UHPLC-MS/MS of parabens in breast milk samples

    Energy Technology Data Exchange (ETDEWEB)

    Souza, Israel D.; Melo, Lidervan P. [Departamento de Química, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP (Brazil); Jardim, Isabel C.S.F. [Instituto de Química, Universidade Estadual de Campinas, Campinas, SP (Brazil); Monteiro, Juliana C.S.; Nakano, Ana Marcia S. [Escola de Enfermagem de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP (Brazil); Queiroz, Maria Eugênia C., E-mail: mariaeqn@ffclrp.usp.br [Departamento de Química, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP (Brazil)

    2016-08-17

    A new molecularly imprinted polymer modified with restricted access material (a hydrophilic external layer), (MIP-RAM) was synthesized via polymerization in situ in an open fused silica capillary. This stationary phase was used as sorbent for in-tube solid phase microextraction (in-tube SPME) to determine parabens in breast milk samples by ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Scanning electron micrographs (SEM) illustrate MIP surface modification after glycerol dimethacrylate (hydrophilic monomer) incorporation. The interaction between parabens and MIP-RAM was investigated by Fourier-transform infrared (FTIR) spectroscopy. The Scatchard plot for MIP-RAM presented two linear parts with different slopes, illustrating binding sites with high- and low-affinity. Endogenous compounds exclusion from the MIP-RAM capillary was demonstrated by in-tube SPME/LC-UV assays carried out with blank milk samples. The in-tube SPME/UHPLC-MS/MS method presented linear range from 10 ng mL{sup −1} (LLOQ) to 400 ng mL{sup −1} with coefficients of determination higher than 0.99, inter-assay precision with coefficient of variation (CV) values ranging from 2 to 15%, and inter-assay accuracy with relative standard deviation (RSD) values ranging from −1% to 19%. Analytical validation parameters attested that in-tube SPME/UHPLC-MS/MS is an appropriate method to determine parabens in human milk samples to assess human exposure to these compounds. Analysis of breast milk samples from lactating women demonstrated that the proposed method is effective. - Highlights: • Molecularly imprinted polymer modified with a hydrophilic external layer (RAM-MIP) was synthesized in a silica capillary. • RAM-MIP capillary, used as sorbent for in-tube SPME, established specific interaction with parabens present in milk samples. • The matrix components that interacted only with the hydrophilic external layer (non-adsorptive network) were excluded.

  20. A robust classic.

    Science.gov (United States)

    Kutzner, Florian; Vogel, Tobias; Freytag, Peter; Fiedler, Klaus

    2011-01-01

    In the present research, we argue for the robustness of illusory correlations (ICs, Hamilton & Gifford, 1976) regarding two boundary conditions suggested in previous research. First, we argue that ICs are maintained under extended experience. Using simulations, we derive conflicting predictions. Whereas noise-based accounts predict ICs to be maintained (Fielder, 2000; Smith, 1991), a prominent account based on discrepancy-reducing feedback learning predicts ICs to disappear (Van Rooy et al., 2003). An experiment involving 320 observations with majority and minority members supports the claim that ICs are maintained. Second, we show that actively using the stereotype to make predictions that are met with reward and punishment does not eliminate the bias. In addition, participants' operant reactions afford a novel online measure of ICs. In sum, our findings highlight the robustness of ICs that can be explained as a result of unbiased but noisy learning.

  1. Robust Airline Schedules

    OpenAIRE

    Eggenberg, Niklaus; Salani, Matteo; Bierlaire, Michel

    2010-01-01

    Due to economic pressure industries, when planning, tend to focus on optimizing the expected profit or the yield. The consequence of highly optimized solutions is an increased sensitivity to uncertainty. This generates additional "operational" costs, incurred by possible modifications of the original plan to be performed when reality does not reflect what was expected in the planning phase. The modern research trend focuses on "robustness" of solutions instead of yield or profit. Although ro...

  2. The Crane Robust Control

    Directory of Open Access Journals (Sweden)

    Marek Hicar

    2004-01-01

    Full Text Available The article is about a control design for complete structure of the crane: crab, bridge and crane uplift.The most important unknown parameters for simulations are burden weight and length of hanging rope. We will use robustcontrol for crab and bridge control to ensure adaptivity for burden weight and rope length. Robust control will be designed for current control of the crab and bridge, necessary is to know the range of unknown parameters. Whole robust will be splitto subintervals and after correct identification of unknown parameters the most suitable robust controllers will be chosen.The most important condition at the crab and bridge motion is avoiding from burden swinging in the final position. Crab and bridge drive is designed by asynchronous motor fed from frequency converter. We will use crane uplift with burden weightobserver in combination for uplift, crab and bridge drive with cooperation of their parameters: burden weight, rope length and crab and bridge position. Controllers are designed by state control method. We will use preferably a disturbance observerwhich will identify burden weight as a disturbance. The system will be working in both modes at empty hook as well asat maximum load: burden uplifting and dropping down.

  3. Determinação do coeficiente de atividade em diluição infinita de hidrocarbonetos em furfural a 298,15 K por SPME-GC/FID

    Directory of Open Access Journals (Sweden)

    Filipe Arantes Furtado

    2010-01-01

    Full Text Available In this work a new method (SPME-GC/FID was developed to analyze the activity of binary liquid mixtures. The purpose is to demonstrate that SPME is capable to be used to determinate activity coefficients at infinite dilution knowing the fiber properties, with a lower cost than the conventional methods encountered in literature such as GLC. The activity coefficients at infinite dilution in furfural for n-hexane, n-heptane and cyclohexane at 298.15 K was determined using SPME and deviations of literature data was about 7%.

  4. Measurement of the isotope ratio of acetic acid in vinegar by HS-SPME-GC-TC/C-IRMS.

    Science.gov (United States)

    Hattori, Ryota; Yamada, Keita; Shibata, Hiroki; Hirano, Satoshi; Tajima, Osamu; Yoshida, Naohiro

    2010-06-23

    Acetic acid is the main ingredient of vinegar, and the worth of vinegar often depends on the fermentation of raw materials. In this study, we have developed a simple and rapid method for discriminating the fermentation of the raw materials of vinegar by measuring the hydrogen and carbon isotope ratio of acetic acid using head space solid-phase microextraction (HS-SPME) combined with gas chromatography-high temperature conversion or combustion-isotope ratio mass spectrometry (GC-TC/C-IRMS). The measurement of acetic acid in vinegar by this method was possible with repeatabilities (1sigma) of +/-5.0 per thousand for hydrogen and +/-0.4 per thousand for carbon, which are sufficient to discriminate the origin of acetic acid. The fermentation of raw materials of several vinegars was evaluated by this method.

  5. Caracterización de los compuestos del aroma en rones colombianos por HS-SPME-GC-MS-O

    Directory of Open Access Journals (Sweden)

    Jazmín Osorio Monsalve

    2016-11-01

    Full Text Available Se identificaron por primera vez 46 compuestos volátiles olfativamente activos con actividad aromática significativa presentes en rones comerciales de Colombia. Lo anterior, mediante microextracción en fase sólida en modo espacio de cabeza (HS-SPME, acoplada a cromatografía de gases con detectores de espectrometría de masas y olfatometría (GC-MS-O. Dentro de los compuestos identificados se encuentran ésteres, compuestos aromáticos, alcoholes, acetales, lactonas y furfural. De esos 46 compuestos, nueve están presentes en todos los rones estudiados y algunos otros son característicos solo de la marca.

  6. An Innovative Rapid Method for Analysis of 10 Organophosphorus Pesticide Residues in Wheat by HS-SPME-GC-FPD/MSD.

    Science.gov (United States)

    Du, Xin; Ren, YongLin; Beckett, Stephen J

    2016-01-01

    The rapid detection of pesticide residues in wheat has become a top food security priority. A solvent-free headspace solid-phase microextraction (HS-SPME) has been evaluated for rapid screening of organophosphorus pesticide (OPP) residues in wheat with high sensitivity. Individual wheat samples (1.7 g), spiked with 10 OPPs, were placed in a 4 mL sealed amber glass vial and heated at 60°C for 45 min. During this time, the OPP residues were extracted with a 50 μm/30 μm divinylbenzene (DVB)/carboxen (CAR)/plasma desorption mass spectroscopy polydimethylsiloxane (PDMS) fiber from the headspace above the sample. The fiber was then removed and injected into the GC injection port at 250°C for desorption of the extracted chemicals. The multiple residues were identified by a GC mass spectrometer detector (GC-MSD) and quantified with a GC flame photometric detector (GC-FPD). Seven spiked levels of 10 OPPs on wheat were analyzed. The GC responses for a 50 μm/30 μm DVB/CAR/PDMS fiber increased with increasing spiking levels, yielding significant (R(2) > 0.98) linear regressions. The lowest LODs of the multiple pesticide standards were evaluated under the conditions of the validation study in a range of levels from 0 (control) to 100 ng of pesticide residue per g of wheat that separated on a low-polar GC capillary column (Agilent DB-35UI). The results of the HS-SPME method were compared with the QuEChERS AOAC 2007.01 method and they showed several advantages over the latter. These included improved sensitivity, selectivity, and simplicity.

  7. A screening method for polycyclic aromatic hydrocarbons determination in water by headspace SPME with GC-FID

    Energy Technology Data Exchange (ETDEWEB)

    Zuazagoitia, D.; Millan, E.; Garcia, R. [Univ. of Pais Vasco, Donostia-San Sebastian (Spain). Dept. of Applied Chemistry

    2007-11-15

    A simple method for determination of polycyclic aromatic hydrocarbons (PAHs) in water using headspace solid-phase microextraction (HS-SPME) with gas chromatography-flame ionisation detector (GC-FID) was developed. In order to obtain the convenient experimental conditions for HS-SPME extraction an experimental design with two steps was accomplished. A 2{sup 6-2} fractional factorial design and central composite design (CCD) considering three significant factors were used. Naphthalene, anthracene and fluoranthene were chosen as representatives of two, three and four aromatic rings, and the global response of three PAHs was used for the results, evaluation. The chosen extraction conditions were: 85 {mu}m polyacrylate fibre; 50 C temperature; 60 min time; 20 mL-dissolution volume (in 40 mL glass vial); without salt addition; and 2 min desorption time. The procedure was extended to other seven PAHs (acenaphthylene, acenaphthene, fluorene, phenanthrene, pyrene, chrysene and benzo(a)anthracene) and the analytical characteristics were checked. The limit of detection (LOD) was from 0.08 (anthracene) to 0.20 {mu}g L{sup -1} (naphthalene). The precision expressed as relative standard deviation (RSD in %) using 50 {mu}g L{sup -1} of each analyte ranged from 6.8 to 17 %. The method was applied to the analysis of the surface waters and leaching waters of contaminated soils from Gipuzkoa (North Spain). The PAHs were not detected in surface water samples. Most of the PAHs were found in the leachates from contaminated soils showing a maximum global value of 75.5 {mu}g L{sup -1}. (orig.)

  8. Phytoscreening for chlorinated solvents using rapid in vitro SPME sampling: Application to urban plume in Verl, Germany

    Science.gov (United States)

    Limmer, M.A.; Balouet, J.-C.; Karg, F.; Vroblesky, D.A.; Burken, J.G.

    2011-01-01

    Rapid detection and delineation of contaminants in urban settings is critically important in protecting human health. Cores from trees growing above a plume of contaminated groundwater in Verl, Germany, were collected in 1 day, with subsequent analysis and plume mapping completed over several days. Solid-phase microextraction (SPME) analysis was applied to detect tetrachloroethene (PCE) and trichloroethene (TCE) to below nanogram/liter levels in the transpiration stream of the trees. The tree core concentrations showed a clear areal correlation to the distribution of PCE and TCE in the groundwater. Concentrations in tree cores were lower than the underlying groundwater, as anticipated; however, the tree core water retained the PCE:TCE signature of the underlying groundwater in the urban, populated area. The PCE:TCE ratio can indicate areas of differing degradation activity. Therefore, the phytoscreening analysis was capable not only of mapping the spatial distribution of groundwater contamination but also of delineating zones of potentially differing contaminant sources and degradation. The simplicity of tree coring and the ability to collect a large number of samples in a day with minimal disruption or property damage in the urban setting demonstrates that phytoscreening can be a powerful tool for gaining reconnaissance-level information on groundwater contaminated by chlorinated solvents. The use of SPME decreases the detection level considerably and increases the sensitivity of phytoscreening as an assessment, monitoring, and phytoforensic tool. With rapid, inexpensive, and noninvasive methods of detecting and delineating contaminants underlying homes, as in this case, human health can be better protected through screening of broader areas and with far faster response times. ?? 2011 American Chemical Society.

  9. Robust efficient video fingerprinting

    Science.gov (United States)

    Puri, Manika; Lubin, Jeffrey

    2009-02-01

    We have developed a video fingerprinting system with robustness and efficiency as the primary and secondary design criteria. In extensive testing, the system has shown robustness to cropping, letter-boxing, sub-titling, blur, drastic compression, frame rate changes, size changes and color changes, as well as to the geometric distortions often associated with camcorder capture in cinema settings. Efficiency is afforded by a novel two-stage detection process in which a fast matching process first computes a number of likely candidates, which are then passed to a second slower process that computes the overall best match with minimal false alarm probability. One key component of the algorithm is a maximally stable volume computation - a three-dimensional generalization of maximally stable extremal regions - that provides a content-centric coordinate system for subsequent hash function computation, independent of any affine transformation or extensive cropping. Other key features include an efficient bin-based polling strategy for initial candidate selection, and a final SIFT feature-based computation for final verification. We describe the algorithm and its performance, and then discuss additional modifications that can provide further improvement to efficiency and accuracy.

  10. Robust automated knowledge capture.

    Energy Technology Data Exchange (ETDEWEB)

    Stevens-Adams, Susan Marie; Abbott, Robert G.; Forsythe, James Chris; Trumbo, Michael Christopher Stefan; Haass, Michael Joseph; Hendrickson, Stacey M. Langfitt

    2011-10-01

    This report summarizes research conducted through the Sandia National Laboratories Robust Automated Knowledge Capture Laboratory Directed Research and Development project. The objective of this project was to advance scientific understanding of the influence of individual cognitive attributes on decision making. The project has developed a quantitative model known as RumRunner that has proven effective in predicting the propensity of an individual to shift strategies on the basis of task and experience related parameters. Three separate studies are described which have validated the basic RumRunner model. This work provides a basis for better understanding human decision making in high consequent national security applications, and in particular, the individual characteristics that underlie adaptive thinking.

  11. Passion, Robustness and Perseverance

    DEFF Research Database (Denmark)

    Lim, Miguel Antonio; Lund, Rebecca

    2016-01-01

    Evaluation and merit in the measured university are increasingly based on taken-for-granted assumptions about the “ideal academic”. We suggest that the scholar now needs to show that she is passionate about her work and that she gains pleasure from pursuing her craft. We suggest that passion...... and pleasure achieve an exalted status as something compulsory. The scholar ought to feel passionate about her work and signal that she takes pleasure also in the difficult moments. Passion has become a signal of robustness and perseverance in a job market characterised by funding shortages, increased pressure...... way to demonstrate their potential and, crucially, their passion for their work. Drawing on the literature on technologies of governance, we reflect on what is captured and what is left out by these two evaluation instruments. We suggest that bibliometric analysis at the individual level is deeply...

  12. Robust Optical Flow Estimation

    Directory of Open Access Journals (Sweden)

    Javier Sánchez Pérez

    2013-10-01

    Full Text Available n this work, we describe an implementation of the variational method proposed by Brox etal. in 2004, which yields accurate optical flows with low running times. It has several benefitswith respect to the method of Horn and Schunck: it is more robust to the presence of outliers,produces piecewise-smooth flow fields and can cope with constant brightness changes. Thismethod relies on the brightness and gradient constancy assumptions, using the information ofthe image intensities and the image gradients to find correspondences. It also generalizes theuse of continuous L1 functionals, which help mitigate the effect of outliers and create a TotalVariation (TV regularization. Additionally, it introduces a simple temporal regularizationscheme that enforces a continuous temporal coherence of the flow fields.

  13. Robust Multimodal Dictionary Learning

    Science.gov (United States)

    Cao, Tian; Jojic, Vladimir; Modla, Shannon; Powell, Debbie; Czymmek, Kirk; Niethammer, Marc

    2014-01-01

    We propose a robust multimodal dictionary learning method for multimodal images. Joint dictionary learning for both modalities may be impaired by lack of correspondence between image modalities in training data, for example due to areas of low quality in one of the modalities. Dictionaries learned with such non-corresponding data will induce uncertainty about image representation. In this paper, we propose a probabilistic model that accounts for image areas that are poorly corresponding between the image modalities. We cast the problem of learning a dictionary in presence of problematic image patches as a likelihood maximization problem and solve it with a variant of the EM algorithm. Our algorithm iterates identification of poorly corresponding patches and re-finements of the dictionary. We tested our method on synthetic and real data. We show improvements in image prediction quality and alignment accuracy when using the method for multimodal image registration. PMID:24505674

  14. Robust snapshot interferometric spectropolarimetry.

    Science.gov (United States)

    Kim, Daesuk; Seo, Yoonho; Yoon, Yonghee; Dembele, Vamara; Yoon, Jae Woong; Lee, Kyu Jin; Magnusson, Robert

    2016-05-15

    This Letter describes a Stokes vector measurement method based on a snapshot interferometric common-path spectropolarimeter. The proposed scheme, which employs an interferometric polarization-modulation module, can extract the spectral polarimetric parameters Ψ(k) and Δ(k) of a transmissive anisotropic object by which an accurate Stokes vector can be calculated in the spectral domain. It is inherently strongly robust to the object 3D pose variation, since it is designed distinctly so that the measured object can be placed outside of the interferometric module. Experiments are conducted to verify the feasibility of the proposed system. The proposed snapshot scheme enables us to extract the spectral Stokes vector of a transmissive anisotropic object within tens of msec with high accuracy.

  15. International Conference on Robust Statistics

    CERN Document Server

    Filzmoser, Peter; Gather, Ursula; Rousseeuw, Peter

    2003-01-01

    Aspects of Robust Statistics are important in many areas. Based on the International Conference on Robust Statistics 2001 (ICORS 2001) in Vorau, Austria, this volume discusses future directions of the discipline, bringing together leading scientists, experienced researchers and practitioners, as well as younger researchers. The papers cover a multitude of different aspects of Robust Statistics. For instance, the fundamental problem of data summary (weights of evidence) is considered and its robustness properties are studied. Further theoretical subjects include e.g.: robust methods for skewness, time series, longitudinal data, multivariate methods, and tests. Some papers deal with computational aspects and algorithms. Finally, the aspects of application and programming tools complete the volume.

  16. Robustness Analyses of Timber Structures

    DEFF Research Database (Denmark)

    Kirkegaard, Poul Henning; Sørensen, John Dalsgaard; Hald, Frederik

    2013-01-01

    The robustness of structural systems has obtained a renewed interest arising from a much more frequent use of advanced types of structures with limited redundancy and serious consequences in case of failure. In order to minimise the likelihood of such disproportionate structural failures, many mo...... with respect to robustness of timber structures and will discuss the consequences of such robustness issues related to the future development of timber structures.......The robustness of structural systems has obtained a renewed interest arising from a much more frequent use of advanced types of structures with limited redundancy and serious consequences in case of failure. In order to minimise the likelihood of such disproportionate structural failures, many...... modern building codes consider the need for the robustness of structures and provide strategies and methods to obtain robustness. Therefore, a structural engineer may take necessary steps to design robust structures that are insensitive to accidental circumstances. The present paper summaries issues...

  17. Measurement of Activity Coefficients at Infinite Dilution for Alcohols in [BMIM][CH3SO4] using HS-SPME/GC-FID

    Directory of Open Access Journals (Sweden)

    A. M. Elias

    Full Text Available ABSTRACT The activity coefficient at infinite dilution (&IN1 and distribution ratios at infinite dilution (&IN2 were determined for alkanols (methanol, ethanol, 1-propanol, 1-butanol, 2-butanol, and 2-methyl-2-propanol in the ionic liquid (IL 1-butyl-3-methylimidazolium methyl sulfate ([BMIM][CH3SO4] by HS-SPME (Headspace - Solid Phase Micro Extraction at four temperatures (298.15, 313.15, 333.15, and 353.15K using headspace - solid phase microextraction (SPME-HS. The results showed significant agreement with literature data. In addition, partial molar excess enthalpies at infinite dilution (&IN3, excess Gibbs energies (&IN4, and excess entropies (&IN5 were calculated from the (&IN6 values.

  18. Applications of Solid-Phase Microextraction and Gas Chromatography/Mass Spectrometry (SPME-GC/MS in the Study of Grape and Wine Volatile Compounds

    Directory of Open Access Journals (Sweden)

    Annarita Panighel

    2014-12-01

    Full Text Available Volatile compounds are responsible for the wine “bouquet”, which is perceived by sniffing the headspace of a glass, and of the aroma component (palate-aroma of the overall flavor, which is perceived on drinking. Grape aroma compounds are transferred to the wine and undergo minimal alteration during fermentation (e.g., monoterpenes and methoxypyrazines; others are precursors of aroma compounds which form in winemaking and during wine aging (e.g., glycosidically-bound volatile compounds and C13-norisoprenoids. Headspace solid phase microextraction (HS-SPME is a fast and simple technique which was developed for analysis of volatile compounds. This review describes some SPME methods coupled with gas chromatography/mass spectrometry (GC/MS used to study the grape and wine volatiles.

  19. Fast and robust direct immersion solid phase microextraction coupled with gas chromatography-time-of-flight mass spectrometry method employing a matrix compatible fiber for determination of triazole fungicides in fruits.

    Science.gov (United States)

    Silva, Érica A Souza; Lopez-Avila, Viorica; Pawliszyn, Janusz

    2013-10-25

    A fast and robust method was developed for the determination of ten triazole fungicides in fruit samples using direct immersion solid-phase microextraction coupled to gas chromatography with time-of-flight mass spectrometry detection (DI-SPME-GC-ToFMS). In this work, a newly developed concept of solid-phase microextraction (SPME) sorbent, which allows for direct immersion extraction in complex food matrices, has been applied in the analysis of 10 triazole fungicides in grapes and strawberries pulps. Potential factors affecting the extraction efficiency were investigated and optimized, including extraction temperature, sample pH, and ionic strength, agitation speed, extraction and desorption times. Under optimized conditions, the method was linear for over 4 orders of magnitude in concentration, with linear regression coefficients (R(2)) greater than 0.99 for all test compounds in both matrices. Method reproducibility, as determined by analysis of spiked grapes and strawberries, was better than ±20%. The limits of quantitation objective (LOQs) ranged from 0.25 to 5 ng g(-1) for both matrices, well below the maximum residues levels allowed for those compounds in both matrices. The method was successfully applied in the analysis of commercial samples of grapes and strawberries. Finally, the new SPME method was compared to a modified version of t QuEChERS AOAC method: the limits of quantitation reached by SPME were at least one order of magnitude lower than those achieved by the QuEChERS method, whereas precision and accuracy were comparable for both methods. Copyright © 2013 Elsevier B.V. All rights reserved.

  20. Dynamics robustness of cascading systems.

    Directory of Open Access Journals (Sweden)

    Jonathan T Young

    2017-03-01

    Full Text Available A most important property of biochemical systems is robustness. Static robustness, e.g., homeostasis, is the insensitivity of a state against perturbations, whereas dynamics robustness, e.g., homeorhesis, is the insensitivity of a dynamic process. In contrast to the extensively studied static robustness, dynamics robustness, i.e., how a system creates an invariant temporal profile against perturbations, is little explored despite transient dynamics being crucial for cellular fates and are reported to be robust experimentally. For example, the duration of a stimulus elicits different phenotypic responses, and signaling networks process and encode temporal information. Hence, robustness in time courses will be necessary for functional biochemical networks. Based on dynamical systems theory, we uncovered a general mechanism to achieve dynamics robustness. Using a three-stage linear signaling cascade as an example, we found that the temporal profiles and response duration post-stimulus is robust to perturbations against certain parameters. Then analyzing the linearized model, we elucidated the criteria of when signaling cascades will display dynamics robustness. We found that changes in the upstream modules are masked in the cascade, and that the response duration is mainly controlled by the rate-limiting module and organization of the cascade's kinetics. Specifically, we found two necessary conditions for dynamics robustness in signaling cascades: 1 Constraint on the rate-limiting process: The phosphatase activity in the perturbed module is not the slowest. 2 Constraints on the initial conditions: The kinase activity needs to be fast enough such that each module is saturated even with fast phosphatase activity and upstream changes are attenuated. We discussed the relevance of such robustness to several biological examples and the validity of the above conditions therein. Given the applicability of dynamics robustness to a variety of systems, it

  1. Selective molecularly imprinted polymer combined with restricted access material for in-tube SPME/UHPLC-MS/MS of parabens in breast milk samples.

    Science.gov (United States)

    Souza, Israel D; Melo, Lidervan P; Jardim, Isabel C S F; Monteiro, Juliana C S; Nakano, Ana Marcia S; Queiroz, Maria Eugênia C

    2016-08-17

    A new molecularly imprinted polymer modified with restricted access material (a hydrophilic external layer), (MIP-RAM) was synthesized via polymerization in situ in an open fused silica capillary. This stationary phase was used as sorbent for in-tube solid phase microextraction (in-tube SPME) to determine parabens in breast milk samples by ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Scanning electron micrographs (SEM) illustrate MIP surface modification after glycerol dimethacrylate (hydrophilic monomer) incorporation. The interaction between parabens and MIP-RAM was investigated by Fourier-transform infrared (FTIR) spectroscopy. The Scatchard plot for MIP-RAM presented two linear parts with different slopes, illustrating binding sites with high- and low-affinity. Endogenous compounds exclusion from the MIP-RAM capillary was demonstrated by in-tube SPME/LC-UV assays carried out with blank milk samples. The in-tube SPME/UHPLC-MS/MS method presented linear range from 10 ng mL(-1) (LLOQ) to 400 ng mL(-1) with coefficients of determination higher than 0.99, inter-assay precision with coefficient of variation (CV) values ranging from 2 to 15%, and inter-assay accuracy with relative standard deviation (RSD) values ranging from -1% to 19%. Analytical validation parameters attested that in-tube SPME/UHPLC-MS/MS is an appropriate method to determine parabens in human milk samples to assess human exposure to these compounds. Analysis of breast milk samples from lactating women demonstrated that the proposed method is effective. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Headspace solid-phase microextraction (HS-SPME) combined with GC-MS as a process analytical technology (PAT) tool for monitoring the cultivation of C. tetani.

    Science.gov (United States)

    Ghader, Masoud; Shokoufi, Nader; Es-Haghi, Ali; Kargosha, Kazem

    2018-04-15

    Vaccine production is a biological process in which variation in time and output is inevitable. Thus, the application of Process Analytical Technologies (PAT) will be important in this regard. Headspace solid - phase microextraction (HS-SPME) coupled with GC-MS can be used as a PAT for process monitoring. This method is suitable to chemical profiling of volatile organic compounds (VOCs) emitted from microorganisms. Tetanus is a lethal disease caused by Clostridium tetani (C. tetani) bacterium and vaccination is an ultimate way to prevent this disease. In this paper, SPME fiber was used for the investigation of VOCs emerging from C. tetani during cultivation. Different types of VOCs such as sulfur-containing compounds were identified and some of them were selected as biomarkers for bioreactor monitoring during vaccine production. In the second step, the portable dynamic air sampling (PDAS) device was used as an interface for sampling VOCs by SPME fibers. The sampling procedure was optimized by face-centered central composite design (FC-CCD). The optimized sampling time and inlet gas flow rates were 10 min and 2 m L s -1 , respectively. PDAS was mounted in exhausted gas line of bioreactor and 42 samples of VOCs were prepared by SPME fibers in 7 days during incubation. Simultaneously, pH and optical density (OD) were evaluated to cultivation process which showed good correlations with the identified VOCs (>80%). This method could be used for VOCs sampling from off-gas of a bioreactor to monitoring of the cultivation process. Copyright © 2018. Published by Elsevier B.V.

  3. Analysis of the volatiles in the headspace above the plasmodium and sporangia of the slime mould (Physarum polycephalum) by SPME-GCMS

    OpenAIRE

    Kateb, Huda al; Costello, Ben de Lacy

    2013-01-01

    Solid phase micro-extraction (SPME) coupled with Gas Chromatography Mass Spectrometry (GC-MS) was used to extract and analyse the volatiles in the headspace above the plasmodial and sporulating stages of the slime mould Physarum Polycephalum. In total 115 compounds were identified from across a broad range of chemical classes. Although more (87) volatile organic compounds (VOCs) were identified when using a higher incubation temperature of 75oC, a large number of compounds (79) were still ide...

  4. Robust continuous clustering.

    Science.gov (United States)

    Shah, Sohil Atul; Koltun, Vladlen

    2017-09-12

    Clustering is a fundamental procedure in the analysis of scientific data. It is used ubiquitously across the sciences. Despite decades of research, existing clustering algorithms have limited effectiveness in high dimensions and often require tuning parameters for different domains and datasets. We present a clustering algorithm that achieves high accuracy across multiple domains and scales efficiently to high dimensions and large datasets. The presented algorithm optimizes a smooth continuous objective, which is based on robust statistics and allows heavily mixed clusters to be untangled. The continuous nature of the objective also allows clustering to be integrated as a module in end-to-end feature learning pipelines. We demonstrate this by extending the algorithm to perform joint clustering and dimensionality reduction by efficiently optimizing a continuous global objective. The presented approach is evaluated on large datasets of faces, hand-written digits, objects, newswire articles, sensor readings from the Space Shuttle, and protein expression levels. Our method achieves high accuracy across all datasets, outperforming the best prior algorithm by a factor of 3 in average rank.

  5. Determination of volatile organic compounds (VOCs) using tedlar bag/solid-phase microextraction/gas chromatography/mass spectrometry (SPME/GC/MS) in ambient and workplace air

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jae Hwan; Lee, Dai Woon [Yonsei Univ., Seoul (Korea, Republic of); Hwang, Seung Man; Heo, Gwi Suk [Korea Research Institute of Standards and Science, Taejon (Korea, Republic of)

    2002-03-01

    SPME techniques have proven to be very useful tools in the analysis of wide VOCs in the air. In this study, we estimated VOCs in ambient and workplace air using a Tedlar ba/SPME/GC/MS system. The calibration curve was set to be linear over the range of 1-30 ppbv. The detection limits ranged from 10 pptv 0.93 ppbv for all VOCs. Reproducibility of TO-14 target gas mixtures by SPME/GC/MS averaged at 8.8 R.S.D (%). Air toxic VOCs (hazardous air pollutants, HAPs) containing a total of forty halohydrocarbons, aromatics, and haloaro-matic carbons could be analyzed with significant accuracy, detection limit and linearity at low ppbv level. Only reactive VOCs with low molecular weight, such as chloromethane, vinylchloride, ethylchloride and 1,2-dichloro-ethane, yielded relatively poor results using this technique. In ambient air samples, ten VOCs were identified and quantified after external calibration. VOC concentration in ambient and workplace air ranged from 0.04 to 1.85 ppbv. The overall process was successfully applied to identify and quantify VOCs in ambient/workplace air.

  6. Ultra trace analysis of PAHs by designing simple injection of large amounts of analytes through the sample reconcentration on SPME fiber after magnetic solid phase extraction.

    Science.gov (United States)

    Khodaee, Nader; Mehdinia, Ali; Esfandiarnejad, Reyhaneh; Jabbari, Ali

    2016-01-15

    A simple solventless injection method was introduced based on the using of a solid-phase microextraction (SPME) fiber for injection of large amounts of the analytes extracted by the magnetic solid phase extraction (MSPE) procedure. The resulted extract from MSPE procedure was loaded on a G-coated SPME fiber, and then the fiber was injected into the gas chromatography (GC) injection port. This method combines the advantages of exhaustive extraction property of MSPE and the solvent-less injection of SPME to improve the sensitivity of the analysis. In addition, the analytes were re-concentrated prior to inject into the gas chromatography (GC) inlet because of the organic solvent removing from the remaining extract of MSPE technique. Injection of the large amounts of analytes was made possible by using the introduced procedure. Fourteen polycyclic aromatic hydrocarbons (PAHs) with different volatility were used as model compounds to investigate the method performance for volatile and semi-volatile compounds. The introduced method resulted in the higher enhancement factors (5097-59376), lower detection limits (0.29-3.3pgmL(-1)), and higher sensitivity for the semi-volatile compounds compared with the conventional direct injection method. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Method for sampling and analysis of volatile biomarkers in process gas from aerobic digestion of poultry carcasses using time-weighted average SPME and GC-MS.

    Science.gov (United States)

    Koziel, Jacek A; Nguyen, Lam T; Glanville, Thomas D; Ahn, Heekwon; Frana, Timothy S; Hans van Leeuwen, J

    2017-10-01

    A passive sampling method, using retracted solid-phase microextraction (SPME) - gas chromatography-mass spectrometry and time-weighted averaging, was developed and validated for tracking marker volatile organic compounds (VOCs) emitted during aerobic digestion of biohazardous animal tissue. The retracted SPME configuration protects the fragile fiber from buffeting by the process gas stream, and it requires less equipment and is potentially more biosecure than conventional active sampling methods. VOC concentrations predicted via a model based on Fick's first law of diffusion were within 6.6-12.3% of experimentally controlled values after accounting for VOC adsorption to the SPME fiber housing. Method detection limits for five marker VOCs ranged from 0.70 to 8.44ppbv and were statistically equivalent (p>0.05) to those for active sorbent-tube-based sampling. The sampling time of 30min and fiber retraction of 5mm were found to be optimal for the tissue digestion process. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Determination of different recreational drugs in sweat by headspace solid-phase microextraction gas chromatography mass spectrometry (HS-SPME GC/MS): Application to drugged drivers.

    Science.gov (United States)

    Gentili, Stefano; Mortali, Claudia; Mastrobattista, Luisa; Berretta, Paolo; Zaami, Simona

    2016-09-10

    A procedure based on headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography/mass spectrometry (GC/MS) has been developed for the determination of most commonly used drugs of abuse in sweat of drivers stopped during roadside controls. DrugWipe 5A sweat screening device was used to collect sweat by a specific pad rubbed gently over forehead skin surface. The procedure involved an acid hydrolysis, a HS-SPME extraction for drugs of abuse but Δ(9)-tetrahydrocannabinol, which was directly extracted in alkaline medium HS-SPME conditions, a GC separation of analytes by a capillary column and MS detection by electron impact ionisation. The method was linear from the limit of quantification (LOQ) to 50ng drug per pad (r(2)≥0.99), with an intra- and inter-assay precision and accuracy always less than 15% and an analytical recovery between 95.1% and 102.8%, depending on the considered analyte. Using the validated method, sweat from 60 apparently intoxicated drivers were found positive to one or more drugs of abuse, showing sweat patches testing as a viable economic and simple alternative to conventional (blood and/or urine) and non conventional (oral fluid) testing of drugs of abuse in drugged drivers. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Determination of organotin compounds by headspace solid-phase microextraction-gas chromatography-pulsed flame-photometric detection (HS-SPME-GC-PFPD)

    Energy Technology Data Exchange (ETDEWEB)

    Bravo, Manuel [Universite de Pau et des Pays de L' Adour, Laboratoire de Chimie Analytique, LCABIE, UMR CNRS 5034, Pau (France); Pontificia Universidad Catolica de Valparaiso, Laboratorio de Quimica Analitica y Ambiental, Instituto de Quimica, Valparaiso (Chile); Lespes, Gaetane; Gautier, Martine Potin [Pontificia Universidad Catolica de Valparaiso, Laboratorio de Quimica Analitica y Ambiental, Instituto de Quimica, Valparaiso (Chile); Gregori, Ida de; Pinochet, Hugo [Universite de Pau et des Pays de L' Adour, Laboratoire de Chimie Analytique, LCABIE, UMR CNRS 5034, Pau (France)

    2005-12-01

    A method based on Headspace solid-phase microextraction (HS-SPME, with a 100 {mu}m PDMS-fiber) in combination with gas-chromatography and pulsed flame-photometric detection (GC-PFPD) has been investigated for simultaneous determination of eight organotin compounds. Monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), monophenyltin (MPhT), and the semi-volatile diphenyltin (DPhT), triphenyltin (TPhT), monooctyltin (MOcT), and dioctyltin (DOcT) were determined after derivatization with sodium tetraethylborate. The conditions used for the extraction and preconcentration step were optimised by experimental design methodology. Tripropyltin (TPrT) and diheptyltin (DHepT) were used as internal standards for quantification of volatile and semi-volatile organotin compounds, respectively. The analytical precision (RSD) for ten successive injections of a standard mixture containing all the organic tin compounds ranged between 2 and 11%. The limits of detection for all the organotin compounds were sub ng (Sn) L{sup -1} in water and close to ng (Sn) kg{sup -1} in sediments. The accuracy of the method was evaluated by analysis of two certified reference material (CRM) sediment samples. The HS-SPME-GC-PFPD was then applied to the analysis of three harbour sediment samples. The results showed that headspace SPME is an attractive tool for analysis of organotin compounds in solid environmental matrices. (orig.)

  10. Analysis of High Quality Agar wood Oil Chemical Compounds By Means Of SPME/ GC-MS and Z-Score Technique

    International Nuclear Information System (INIS)

    Nurlaila Ismail; Mohd Ali Nor Azah; Mailina Jamil; Saiful Nizam Tajuddin; Mohd Nasir Taib

    2013-01-01

    Currently, the grading of the agar wood oil to the high and low quality is done using manually such as human trained grader. It was performed based on the agar wood oil physical properties such as human experience and perception and the oil colour, odor and long lasting aroma. Several researchers found that chemical profiles of the oil should be utilized to overcome the problem facing by manual techniques for example human nose cannot tolerate with the many oils at the same time, so that accurate result can be obtained in grading the agar wood oil. The analysis involved of SPME/ GC-MS and Z-score techniques have been proposed in this study to analyze the chemical compounds especially from the high quality samples of agar wood oil (Aquilariamalaccensis) from Malaysia. Two SPME fibers were used such as divinylbenzene-carbogen-polydimethylsiloxane (DVB-CAR-PDMS) and polydimethylsiloxane (PDMS) in extracting the oils compound under three different sampling temperature conditions such as 40, 60 and 80 degree Celsius. The chemical compounds extracted by SPME/ GC-MS were analyzed. The chemical compounds as identified by Z-score as significant compounds were discussed before the conclusion is made. It was found that 10-epi-γ-eudesmol, aromadendrene, β-agar ofuran, α-agar ofuran and γ-eudesmol were highlighted as significant for high quality agar wood oil and can be used as a marker compounds in classifying the agar wood oil. (author)

  11. Development of a simple and sensitive method for the characterization of odorous waste gas emissions by means of solid-phase microextraction (SPME) and GC-MS/olfactometry.

    Science.gov (United States)

    Kleeberg, K K; Liu, Y; Jans, M; Schlegelmilch, M; Streese, J; Stegmann, R

    2005-01-01

    A solid-phase microextraction (SPME) method has been developed for the extraction of odorous compounds from waste gas. The enriched compounds were characterized by gas chromatography-mass spectrometry (GC-MS) and gas chromatography followed by simultaneous flame ionization detection and olfactometry (GC-FID/O). Five different SPME fiber coatings were tested, and the carboxen/polydimethylsiloxane (CAR/PDMS) fiber showed the highest ability to extract odorous compounds from the waste gas. Furthermore, parameters such as exposure time, desorption temperature, and desorption time have been optimized. The SPME method was successfully used to characterize an odorous waste gas from a fat refinery prior to and after waste gas treatment in order to describe the treatment efficiency of the used laboratory scale plant which consisted of a bioscrubber/biofilter combination and an activated carbon adsorber. The developed method is a valuable approach to provide detailed information of waste gas composition and complements existing methods for the determination of odors. However, caution should be exercised if CAR/PDMS fibers are used for the quantification of odorous compounds in multi-component matrices like waste gas emissions since the relative affinity of each analyte was shown to differ according to the total amount of analytes present in the sample.

  12. Determination of volatile organic compounds (VOCs) using tedlar bag/solid-phase microextraction/gas chromatography/mass spectrometry (SPME/GC/MS) in ambient and workplace air

    International Nuclear Information System (INIS)

    Lee, Jae Hwan; Lee, Dai Woon; Hwang, Seung Man; Heo, Gwi Suk

    2002-01-01

    SPME techniques have proven to be very useful tools in the analysis of wide VOCs in the air. In this study, we estimated VOCs in ambient and workplace air using a Tedlar ba/SPME/GC/MS system. The calibration curve was set to be linear over the range of 1-30 ppbv. The detection limits ranged from 10 pptv 0.93 ppbv for all VOCs. Reproducibility of TO-14 target gas mixtures by SPME/GC/MS averaged at 8.8 R.S.D (%). Air toxic VOCs (hazardous air pollutants, HAPs) containing a total of forty halohydrocarbons, aromatics, and haloaro-matic carbons could be analyzed with significant accuracy, detection limit and linearity at low ppbv level. Only reactive VOCs with low molecular weight, such as chloromethane, vinylchloride, ethylchloride and 1,2-dichloro-ethane, yielded relatively poor results using this technique. In ambient air samples, ten VOCs were identified and quantified after external calibration. VOC concentration in ambient and workplace air ranged from 0.04 to 1.85 ppbv. The overall process was successfully applied to identify and quantify VOCs in ambient/workplace air

  13. Establishment of Exposure to Organophosphorus Warfare Agents by Means of SPME-GSMS Analysis of Bodily Fluids

    International Nuclear Information System (INIS)

    Saveleva, E. I.; Koryagina, N. L.; Radilov, A. S.; Khlebnikova, N. S.; Khrustaleva, V. S.; Feld, V. E.

    2007-01-01

    Reliable chemical analytical procedures for revealing an exposure to toxic chemicals, identifying the active substance, and assessing the degree of exposure are necessary as a component of medical and forensic activities in cases of the possible use of highly toxic chemicals in war conflicts and terrorism acts, as well as emergency situations in chemical industry, specifically at chemical weapons storage and destruction facilities. According to Chemical Weapons Convention, Part XI, Appendix 4, e-17, 'samples of importance in the investigation of alleged use include biomedical samples from human or animal sources (blood, urine, excreta, tissue etc.)'. Urinary metabolites, O-alkyl esters of methylphosphic acid, offer one of the simplest means of confirming an exposure to organophosphorus warfare agents (OPWA). Urine, unlike blood or tissues, does not require invasive collection demanding in terms of sterility. Excretion with urine is the major route of elimination of OPWA from an organism. According to published data, 90% of OPWA metabolites are excreted within 48-72 h after intoxication. We developed an SPME-GCMS procedure for the determination of O-alkyl esters methylphosphonic acid in urine, with the following detection limits,: isopropyl and isobutyl esters 5 ng/ml and pinacolyl ester 1 ng/ml. The procedure involves derivatization of the target compounds directly on the microfiber. The total analysis time is 1-1.5 h. In animal experiments in vivo we could establish the exposure to OPWA at a half-LD50 level within no less than 48 h after intoxication. In principle, OPWA metabolites could be detected in urine within two weeks after intoxication but at higher doses. Retrospective analysis of urinary metabolites in cases of the exposure to low doses of OPWA requires lower detection limits (0.1-1 ng/ml). Optimal objects for the retrospective analysis of OPWA in an organism are long-lived blood protein adducts. We developed a procedure for revealing an exposure to

  14. Robust Trust in Expert Testimony

    Directory of Open Access Journals (Sweden)

    Christian Dahlman

    2015-05-01

    Full Text Available The standard of proof in criminal trials should require that the evidence presented by the prosecution is robust. This requirement of robustness says that it must be unlikely that additional information would change the probability that the defendant is guilty. Robustness is difficult for a judge to estimate, as it requires the judge to assess the possible effect of information that the he or she does not have. This article is concerned with expert witnesses and proposes a method for reviewing the robustness of expert testimony. According to the proposed method, the robustness of expert testimony is estimated with regard to competence, motivation, external strength, internal strength and relevance. The danger of trusting non-robust expert testimony is illustrated with an analysis of the Thomas Quick Case, a Swedish legal scandal where a patient at a mental institution was wrongfully convicted for eight murders.

  15. Characterization of Volatile Compounds with HS-SPME from Oxidized n-3 PUFA Rich Oils via Rancimat Tests.

    Science.gov (United States)

    Yang, Kai-Min; Cheng, Ming-Ching; Chen, Chih-Wei; Tseng, Chin-Yin; Lin, Li-Yun; Chiang, Po-Yuan

    2017-02-01

    Algae oil and fish oil are n-3 PUFA mainstream commercial products. The various sources for the stability of n-3 PUFA oxidation are influenced by the fatty acid composition, extraction and refined processing. In this study, the oil stability index (OSI) occurs within 2.3 to 7.6 hours with three different n-3 PUFA rich oil. To set the OSI in the Rancimat test as the oil stability limit and observed various degrees of oxidation (0, 25, 50, 75, 100 and 125%). The volatile oxidation compounds were analyzed via headspace-solid phase microextraction (HS-SPME) and GC/MS. We detected 51 volatile compound variations during the oxidation, which were composed of aldehydes, hydrocarbons, cyclic compounds, alcohols, benzene compounds, ketones, furans, ester and pyrrolidine. The off-flavor characteristics can be strongly influenced by the synergy effects of volatile oxidation compounds. Chemometric analysis (PCA and AHC) was applied to identify the sensitive oxidation marker compounds, which included a (E,E)-2,4-heptadienal appropriate marker, via lipid oxidation in the n-3 PUFA rich oil.

  16. Optimisation of recovery protocols for double-base smokeless powder residues analysed by total vaporisation (TV) SPME/GC-MS.

    Science.gov (United States)

    Sauzier, Georgina; Bors, Dana; Ash, Jordan; Goodpaster, John V; Lewis, Simon W

    2016-09-01

    The investigation of explosive events requires appropriate evidential protocols to recover and preserve residues from the scene. In this study, a central composite design was used to determine statistically validated optimum recovery parameters for double-base smokeless powder residues on steel, analysed using total vaporisation (TV) SPME/GC-MS. It was found that maximum recovery was obtained using isopropanol-wetted swabs stored under refrigerated conditions, then extracted for 15min into acetone on the same day as sample collection. These parameters were applied to the recovery of post-blast residues deposited on steel witness surfaces following a PVC pipe bomb detonation, resulting in detection of all target components across the majority of samples. Higher overall recoveries were obtained from plates facing the sides of the device, consistent with the point of first failure occurring in the pipe body as observed in previous studies. The methodology employed here may be readily applied to a variety of other explosive compounds, and thus assist in establishing 'best practice' procedures for explosive investigations. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Farmed and wild sea bass (Dicentrarchus labrax) volatile metabolites: a comparative study by SPME-GC/MS.

    Science.gov (United States)

    Vidal, Natalia P; Manzanos, María J; Goicoechea, Encarnación; Guillén, María D

    2016-03-15

    Farmed and wild European sea bass (Dicentrarchus labrax) could be distinguished by its volatile metabolites, an issue not addressed until now. The aim of this work was to study these metabolites by solid-phase microextraction followed by gas chromatography/mass spectrometry (SPME-GC/MS). Both farmed and wild sea bass have a great number of volatile metabolites, most of them being in low concentrations. These include alcohols, aldehydes, ketones, alkylfurans, acids, aliphatic and aromatic hydrocarbons, terpenes, sulfur and nitrogen derivatives, 2,6-di-tert-butyl-4-methylphenol and one derived compound, as well as 2,4,7,9-tetramethyl-5-decyne-4,7-diol, this latter compound presumably resulting from environmental contamination. Important differences have been detected between both types of sea bass, and also among individuals inside each group. Farmed specimens are richer in volatile metabolites than the wild counterparts; however, these latter, in general, contain a high number and abundance of metabolites resulting from microbial and enzymatic non-oxidative activity than the former. Clear differences in the volatile metabolites of wild and farmed sea bass have been found. A great deal of valuable information on sea bass volatile metabolites has been obtained, which can be useful in understanding certain aspects of the quality and safety of raw and processed sea bass. © 2015 Society of Chemical Industry.

  18. A SPME-based method for rapidly and accurately measuring the characteristic parameter for DEHP emitted from PVC floorings.

    Science.gov (United States)

    Cao, J; Zhang, X; Little, J C; Zhang, Y

    2017-03-01

    Semivolatile organic compounds (SVOCs) are present in many indoor materials. SVOC emissions can be characterized with a critical parameter, y 0 , the gas-phase SVOC concentration in equilibrium with the source material. To reduce the required time and improve the accuracy of existing methods for measuring y 0 , we developed a new method which uses solid-phase microextraction (SPME) to measure the concentration of an SVOC emitted by source material placed in a sealed chamber. Taking one typical indoor SVOC, di-(2-ethylhexyl) phthalate (DEHP), as the example, the experimental time was shortened from several days (even several months) to about 1 day, with relative errors of less than 5%. The measured y 0 values agree well with the results obtained by independent methods. The saturated gas-phase concentration (y sat ) of DEHP was also measured. Based on the Clausius-Clapeyron equation, a correlation that reveals the effects of temperature, the mass fraction of DEHP in the source material, and y sat on y 0 was established. The proposed method together with the correlation should be useful in estimating and controlling human exposure to indoor DEHP. The applicability of the present approach for other SVOCs and other SVOC source materials requires further study. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  19. Application of HS-SPME-GC-MS method for the detection of active moulds on historical parchment.

    Science.gov (United States)

    Sawoszczuk, Tomasz; Syguła-Cholewińska, Justyna; Del Hoyo-Meléndez, Julio M

    2017-03-01

    The goal of this work was to analyse the profile of microbial volatile organic compounds (MVOCs) emitted by moulds growing on parchment samples, in search of particular volatiles mentioned in the literature as indicators of active mould growth. First, the growth of various moulds on samples of parchment was assessed. Those species that showed collagenolytic activity were then inoculated on two types of media: samples of parchment placed on media and on media containing amino acids that are elements of the structure of collagen. All samples were prepared inside 20-ml vials (closed system). In the first case, the media did not contain any sources of organic carbon, nitrogen, or sulphur, i.e. parchment was the only nutrient for the moulds. A third type of sample was historical parchment prepared in a Petri dish without a medium and inoculated with a collagenolytically active mould (open system). The MVOCs emitted by moulds were sampled with the headspace-SPME method. Volatiles extracted on DVB/CAR/PDMS fibres were analysed in a gas chromatography-mass spectrometry system. Qualitative and quantitative analyses of chromatograms were carried out in search of indicators of metabolic activity. The results showed that there are three groups of volatiles that can be used for the detection of active forms of moulds on parchment objects. To the best of our knowledge, this is the first work to measure MVOCs emitted by moulds growing on parchment.

  20. Metabolome based volatiles profiling in 13 date palm fruit varieties from Egypt via SPME GC-MS and chemometrics.

    Science.gov (United States)

    Khalil, Mohammed N A; Fekry, Mostafa I; Farag, Mohamed A

    2017-02-15

    Dates (Phoenix dactylifera L.) are distributed worldwide as major food complement providing a source of sugars and dietary fiber as well as macro- and micronutrients. Although phytochemical analyses of date fruit non-volatile metabolites have been reported, much less is known about the aroma given off by the fruit, which is critical for dissecting sensory properties and quality traits. Volatile constituents from 13 date varieties grown in Egypt were profiled using SPME-GCMS coupled to multivariate data analysis to explore date fruit aroma composition and investigate potential future uses by food industry. A total of 89 volatiles were identified where lipid-derived volatiles and phenylpropanoid derivatives were the major components of date fruit aroma. Multivariate data analyses revealed that 2,3-butanediol, hexanal, hexanol and cinnamaldehyde contributed the most to classification of different varieties. This study provides the most complete map of volatiles in Egyptian date fruit, with Siwi and Sheshi varieties exhibiting the most distinct aroma among studied date varieties. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. Natural Variation of Volatile Compounds in Virgin Olive Oil Analyzed by HS-SPME/GC-MS-FID

    Directory of Open Access Journals (Sweden)

    Carlos Sanz

    2018-04-01

    Full Text Available Virgin olive oil is unique among plant oils for its high levels of oleic acid, and the presence of a wide range of minor components, which are responsible for both its health-promoting properties and characteristic aroma, and only produced when olives are crushed during the industrial process used for oil production. The genetic variability of the major volatile compounds comprising the oil aroma was studied in a representative sample of olive cultivars from the World Olive Germplasm Collection (IFAPA, Cordoba, Spain, by means of the headspace solid-phase microextraction/gas chromatography–mass spectrometry–flame ionization detection (HS-SPME/GC-MS-FID. The analytical data demonstrated that a high variability is found for the content of volatile compounds in olive species, and that most of the volatile compounds found in the oils were synthesized by the enzymes included in the so-called lipoxygenase pathway. Multivariate analysis allowed the identification of cultivars that are particularly interesting, in terms of volatile composition and presumed organoleptic quality, which can be used both to identify old olive cultivars that give rise to oils with a high organoleptic quality, and in parent selection for olive breeding programs.

  2. NMR, HS-SPME-GC/MS, and HPLC/MSn Analyses of Phytoconstituents and Aroma Profile of Rosmarinus eriocalyx.

    Science.gov (United States)

    Bendif, Hamdi; Miara, Mohamed Djamel; Peron, Gregorio; Sut, Stefania; Dall'Acqua, Stefano; Flamini, Guido; Maggi, Filippo

    2017-10-01

    In this work, a comprehensive study on the chemical constituents of the aerial parts of Rosmarinus eriocalyx (Lamiaceae), an aromatic shrub traditionally consumed as a food and herbal remedy in Algeria, is presented. The aroma profile was analysed by headspace solid phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC/MS), whereas the crude extract constituents were analyzed by 1 H-NMR and by high performance liquid chromatography coupled with mass spectrometry (HPLC/MS n ). Thirty-nine volatile compounds, most of them being monoterpenes, have been identified, with camphor, camphene, and α-pinene as the most abundant constituents. 1 H-NMR analysis revealed the presence of phenolic compounds and betulinic acid while HPLC/MS n allowed the identification of glycosilated and aglyconic flavonoids as well as phenylpropanoid derivatives. Some of these constituents, namely as betulinic acid, rosmanol, and cirsimaritin were reported for the first time in R. eriocalyx. © 2017 Wiley-VHCA AG, Zurich, Switzerland.

  3. Analysis of volatile compounds in gluten-free bread crusts with an optimised and validated SPME-GC/QTOF methodology.

    Science.gov (United States)

    Pico, Joana; Antolín, Beatriz; Román, Laura; Gómez, Manuel; Bernal, José

    2018-04-01

    The aroma of bread crust, as one of the first characteristics perceived, is essential for bread acceptance. However, gluten-free bread crusts exhibit weak aroma. A SPME-GC/QTOF methodology was optimised with PCA and RSM and validated for the quantification of 44 volatile compounds in bread crust, extracting 0.75 g of crust at 60 °C for 51 min. LODs ranged between 3.60 and 1760 μg Kg -1 , all the R 2 were higher than 0.99 and %RSD for precision and %Er for accuracy were lower than 9% and 12%, respectively. A commercial wheat bread crust was quantified, and furfural was the most abundant compound. Bread crusts of wheat starch and of japonica rice, basmati rice and teff flours were also quantified. Teff flour and wheat starch crusts were very suitable for improving gluten-free bread crust aroma, due to their similar content in 2-acetyl-1-pyrroline and 4-hydroxy-2,5-dimethyl-3(2H)-furanone compared to wheat flour crust and also for their high content in pyrazines. Copyright © 2018 Elsevier Ltd. All rights reserved.

  4. Analytic escrutineo for plaguicidas organofosforados in blood in forensic cases by means of SPME-GC/NPD

    International Nuclear Information System (INIS)

    Fernandez Quesada, K.; Saenz Ugalde, M. F.

    2003-01-01

    The plaguicidas organophosphorus represent one of the most important causes of intoxication in Costa Rica; 20% of the cases received in the Section of Toxicology of the Department of Forensic Sciences of the Organism of Judicial Investigation (OIJ) are related to these plaguicidas. At the present time, the employed techniques in this institution to carry out the organophosphorus analyses in blood, present important limitations in their analytic potential. As a consequence, it is necessary to look for new methodologies, with the purpose to obtain a great specificity, and to diminish the limits of detection. This would allow a more qualified service that assures the validity and reliability of the results. Besides, it is an ideal instrument for the correct administration of justice of the Judicial Authorities. In this final work of graduation, it develops a methodology for the scrutiny of pesticides organophosphorus, in which a sample of biological origin of forensic importance is used. This employs a technique of quick, simple and clean extraction, using a separation method of detection of high analytic sensibility. In the methodology's development, samples of total blood, and the microextraccion techniques in solid phase will be used (SPME), and detection with gas chromatography by a specific instrumental detector of match and nitrogen (GCINPD) [es

  5. Robust and distributed hypothesis testing

    CERN Document Server

    Gül, Gökhan

    2017-01-01

    This book generalizes and extends the available theory in robust and decentralized hypothesis testing. In particular, it presents a robust test for modeling errors which is independent from the assumptions that a sufficiently large number of samples is available, and that the distance is the KL-divergence. Here, the distance can be chosen from a much general model, which includes the KL-divergence as a very special case. This is then extended by various means. A minimax robust test that is robust against both outliers as well as modeling errors is presented. Minimax robustness properties of the given tests are also explicitly proven for fixed sample size and sequential probability ratio tests. The theory of robust detection is extended to robust estimation and the theory of robust distributed detection is extended to classes of distributions, which are not necessarily stochastically bounded. It is shown that the quantization functions for the decision rules can also be chosen as non-monotone. Finally, the boo...

  6. Robustness of IPTV business models

    NARCIS (Netherlands)

    Bouwman, H.; Zhengjia, M.; Duin, P. van der; Limonard, S.

    2008-01-01

    The final stage in the STOF method is an evaluation of the robustness of the design, for which the method provides some guidelines. For many innovative services, the future holds numerous uncertainties, which makes evaluating the robustness of a business model a difficult task. In this chapter, we

  7. Robustness Evaluation of Timber Structures

    DEFF Research Database (Denmark)

    Kirkegaard, Poul Henning; Sørensen, John Dalsgaard

    2009-01-01

    Robustness of structural systems has obtained a renewed interest due to a much more frequent use of advanced types of structures with limited redundancy and serious consequences in case of failure.......Robustness of structural systems has obtained a renewed interest due to a much more frequent use of advanced types of structures with limited redundancy and serious consequences in case of failure....

  8. Robust statistical methods with R

    CERN Document Server

    Jureckova, Jana

    2005-01-01

    Robust statistical methods were developed to supplement the classical procedures when the data violate classical assumptions. They are ideally suited to applied research across a broad spectrum of study, yet most books on the subject are narrowly focused, overly theoretical, or simply outdated. Robust Statistical Methods with R provides a systematic treatment of robust procedures with an emphasis on practical application.The authors work from underlying mathematical tools to implementation, paying special attention to the computational aspects. They cover the whole range of robust methods, including differentiable statistical functions, distance of measures, influence functions, and asymptotic distributions, in a rigorous yet approachable manner. Highlighting hands-on problem solving, many examples and computational algorithms using the R software supplement the discussion. The book examines the characteristics of robustness, estimators of real parameter, large sample properties, and goodness-of-fit tests. It...

  9. Robust loss functions for boosting.

    Science.gov (United States)

    Kanamori, Takafumi; Takenouchi, Takashi; Eguchi, Shinto; Murata, Noboru

    2007-08-01

    Boosting is known as a gradient descent algorithm over loss functions. It is often pointed out that the typical boosting algorithm, Adaboost, is highly affected by outliers. In this letter, loss functions for robust boosting are studied. Based on the concept of robust statistics, we propose a transformation of loss functions that makes boosting algorithms robust against extreme outliers. Next, the truncation of loss functions is applied to contamination models that describe the occurrence of mislabels near decision boundaries. Numerical experiments illustrate that the proposed loss functions derived from the contamination models are useful for handling highly noisy data in comparison with other loss functions.

  10. Theoretical Framework for Robustness Evaluation

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard

    2011-01-01

    This paper presents a theoretical framework for evaluation of robustness of structural systems, incl. bridges and buildings. Typically modern structural design codes require that ‘the consequence of damages to structures should not be disproportional to the causes of the damages’. However, although...... the importance of robustness for structural design is widely recognized the code requirements are not specified in detail, which makes the practical use difficult. This paper describes a theoretical and risk based framework to form the basis for quantification of robustness and for pre-normative guidelines...

  11. Robustness of airline route networks

    Science.gov (United States)

    Lordan, Oriol; Sallan, Jose M.; Escorihuela, Nuria; Gonzalez-Prieto, David

    2016-03-01

    Airlines shape their route network by defining their routes through supply and demand considerations, paying little attention to network performance indicators, such as network robustness. However, the collapse of an airline network can produce high financial costs for the airline and all its geographical area of influence. The aim of this study is to analyze the topology and robustness of the network route of airlines following Low Cost Carriers (LCCs) and Full Service Carriers (FSCs) business models. Results show that FSC hubs are more central than LCC bases in their route network. As a result, LCC route networks are more robust than FSC networks.

  12. EVALUACIÓN DE DES, FSC Y SPME/CG-MS PARA LA EXTRACCIÓN Y DETERMINACIÓN DE COMPUESTOS RESPONSABLES DEL AROMA DE CAFÉ TOSTADO DE VILCABAMBA - ECUADOR

    Directory of Open Access Journals (Sweden)

    Jorge G. Figueroa

    2016-07-01

    Full Text Available The aim of this study was to compare the usefulness of three extraction methods: solid-phase microextraction (SPME with four different coating (PDMS, PDMS/DVB, DVB/CAR/PDMS and PA, supercritical fluid extraction with carbon dioxide (SCF and simultaneous distillation and extraction (SDE for isolation of flavor compounds from roasted ground coffee (Coffea arabica L. var. Typica of Vilcabamba (Ecuador. Identification and characterization of volatile compounds were achieved using gas chromatography / mass spectrometry (GC-MS. Analysis of variance and principal components analysis was done. For the SPME method the coating material affect the amount and concentration of compounds extracted, the DVB/CAR/PDMS coating provided the most representative aroma extract (44 compounds were identified. The SCF method allowed extracting a higher amount of compounds and also their identification by GC-MS (72 that SDE (64 and SPME (57, in addition provide higher extractions. The acetic acid, caffeine, furfuryl alcohol, furfural, 5-methylfurfural, butylated hydroxytoluene and maltol were the compounds with higher concentrations found with SPME and SDE, with SCF were found higher concentration to compounds with high molecular weights (> 194 g mol-1. Preferably SPME-DVB/CAR/PDMS method should be used for a characterization of coffee aroma compounds.

  13. Robust Portfolio Optimization Using Pseudodistances.

    Science.gov (United States)

    Toma, Aida; Leoni-Aubin, Samuela

    2015-01-01

    The presence of outliers in financial asset returns is a frequently occurring phenomenon which may lead to unreliable mean-variance optimized portfolios. This fact is due to the unbounded influence that outliers can have on the mean returns and covariance estimators that are inputs in the optimization procedure. In this paper we present robust estimators of mean and covariance matrix obtained by minimizing an empirical version of a pseudodistance between the assumed model and the true model underlying the data. We prove and discuss theoretical properties of these estimators, such as affine equivariance, B-robustness, asymptotic normality and asymptotic relative efficiency. These estimators can be easily used in place of the classical estimators, thereby providing robust optimized portfolios. A Monte Carlo simulation study and applications to real data show the advantages of the proposed approach. We study both in-sample and out-of-sample performance of the proposed robust portfolios comparing them with some other portfolios known in literature.

  14. Head Space Solid Phase Micro-Extraction (HS - SPME of volatile organic compounds produced by Sporidiobolus salmonicolor (CBS 2636

    Directory of Open Access Journals (Sweden)

    Eunice Valduga

    2010-12-01

    Full Text Available The aim of the present study was the assessment of volatile organic compounds produced by Sporidiobolus salmonicolor (CBS 2636 using methyl and ethyl ricinoleate, ricinoleic acid and castor oil as precursors. The analysis of the volatile organic compounds was carried out using Head Space Solid Phase Micro-Extraction (HS - SPME. Factorial experimental design was used for investigating extraction conditions, verifying stirring rate (0-400 rpm, temperature (25-60 ºC, extraction time (10-30 minutes, and sample volume (2-3 mL. The identification of volatile organic compounds was carried out by Gas Chromatography with Mass Spectrum Detector (GC/MSD. The conditions that resulted in maximum extraction were: 60 ºC, 10 minutes extraction, no stirring, sample volume of 2.0 mL, and addition of saturated KCl (1:10 v/v. In the bio-production of volatile organic compounds the effect of stirring rate (120-200 rpm, temperature (23-33 ºC, pH (4.0-8.0, precursor concentration (0.02-0.1%, mannitol (0-6%, and asparagine concentration (0-0.2% was investigated. The bio-production at 28 ºC, 160 rpm, pH 6,0 and with the addition of 0.02% ricinoleic acid to the medium yielded the highest production of VOCs, identified as 1,4-butanediol, 1,2,2-trimethylciclopropilamine, beta-ionone; 2,3-butanodione, pentanal, tetradecane, 2-isononenal, 4-octen-3-one, propanoic acid, and octadecane.

  15. Oxidative Stress Biomarkers in Exhaled Breath of Workers Exposed to Crystalline Silica Dust by SPME-GC-MS.

    Science.gov (United States)

    Jalali, Mahdi; Zare Sakhvidi, Mohammad Javad; Bahrami, Abdulrahman; Berijani, Nima; Mahjub, Hussein

    2016-01-01

    Silicosis is considered an oxidative stress related disease that can lead to the development of lung cancer. In this study, our purpose was to analysis of volatile organic compounds (VOCs) in the exhaled breath of workers exposed to silica containing dust and compare peak area of these compounds with silicosis patients and healthy volunteers (smokers and nonsmokers) groups. In this cross sectional case-control study, the exhaled breath of 69 subjects including workers exposed to silica (n=20), silicosis patient (n=4), healthy non-smoker (n=20) and healthy smoker (n=25) were analyzed. We collected breath samples using 3-liter Tedlar bags. The VOCs were extracted with solid phase micro-extraction (SPME) and analyzed by gas chromatography-mass spectrometry (GC-MS). Personal exposure intensity was measured according to NIOSH 7601 method. Respiratory parameters were measured using spirometry. Seventy percent and 100% of the exposures to crystalline silica dust exceeded from 8 h TWA ACGIH TLVs in case and positive control groups, respectively. A significant negative correlation was found between dust exposure intensity and FEV1/FVC when exposure and positive control groups were studied in a group (r2=-0.601, P<0.001). Totally, forty VOCs were found in all exhaled breath samples. Among the VOCs, the mean of peak area acetaldehyde, hexanal, nonanal, decane, pentad cane, 2-propanol and 3-hydroxy-2-butanone were higher in exhaled breath of the workers exposed to silica and silicosis patient compared to the healthy smoker and nonsmoker controls. In some cases the difference was significant (P<0.05). The analysis of some VOCs in exhaled breath of subjects is appropriate biomarker to determine of exposure to silica.

  16. An approach to determination of phenolic compounds in seawater using SPME-GC-MS based on SWCNTs coating

    Science.gov (United States)

    Zhu, Jia; Wang, Ying; Zeng, Lin

    2016-08-01

    Phenolic compounds have become one kind of the important pollutants of the marine environment. Single-walled Carbon nanotubes, as one-dimensional nano materials, have light weight and perfect hexagonal structure of connections, with many unusual mechanical, chemical and electrical properties. In recent years, with the research of carbon nanotubes and other nano materials, the application prospect is also constantly discussed. In this paper, homemade single-walled carbon nanotubes (SWCNTs) coating was used for establishing an analytical approach to the determination of five kinds of phenolic compounds in seawater using SPME-GC-MS. Optimal conditions: After saturation was conducted with NaCl, and pH was adjusted to 2.0 with H2SO4, the extract was immersed in a water bath at 40°C for GC-MS determination through 40-min agitating extraction at 500 rmin-1 and 3-min desorption at 280°C. The liniearities ranged between 0.01-100 μg L-1, and the determination limits ranged between 1.5-10 ng L-1. The relative standard deviation (RSD, n = 5) was less than 6.5%. For the phenolic compounds obtained from the spiked recovery test for actual seawater samples, the rates of recovery were 87.5%-101.7%, and the RSDs were less than 8.8%, which met the requirements of determination. Due to its simplicity, high efficiency and low consumption, this approach is suitable for the analysis of trace amounts of phenolic compounds in marine waters.

  17. Usefulness of a PARAFAC decomposition in the fiber selection procedure to determine chlorophenols by means SPME-GC-MS.

    Science.gov (United States)

    Morales, Rocío; Cruz Ortiz, M; Sarabia, Luis A

    2012-05-01

    In this work, a procedure based on solid-phase microextraction and gas chromatography coupled with mass spectrometry is proposed to determine chlorophenols in water without derivatization. The following chlorophenols are studied: 2,4-dichlorophenol; 2,4,6-trichlorophenol; 2,3,4,6-tetrachlorophenol and pentachlorophenol. Three kinds of SPME fibers, polyacrylate, polydimethylsiloxane, and polydimethylsiloxane/divinylbenzene are compared to identify the most suitable one for the extraction process on the basis of two criteria: (a) to select the equilibrium time studying the kinetics of the extraction, and (b) to obtain the best values of the figures of merit. In both cases, a three-way PARAllel FACtor analysis decomposition is used. For the first step, the three-way experimental data are arranged as follows: if I extraction times are considered, the tensor of data, X, of dimensions I × J × K is generated by concatenating the I matrices formed by the abundances of the J m/z ions recorded in K elution times around the retention time for each chlorophenol. The second-order property of PARAFAC (or PARAFAC2) assesses the unequivocal identification of each chlorophenol, as consequence, the loadings in the first mode estimated by the PARAFAC decomposition are the kinetic profile. For the second step, a calibration based on a PARAFAC decomposition is used for each fiber. The best figures of merit were obtained with PDMS/DVB fiber. The values of decision limit, CCα, achieved are between 0.29 and 0.67 μg L(-1) for the four chlorophenols. The accuracy (trueness and precision) of the procedure was assessed. This procedure has been applied to river water samples.

  18. Volatiles and primary metabolites profiling in two Hibiscus sabdariffa (roselle) cultivars via headspace SPME-GC-MS and chemometrics.

    Science.gov (United States)

    Farag, Mohamed A; Rasheed, Dalia M; Kamal, Islam M

    2015-12-01

    Hibiscus sabdariffa (roselle) is a plant of considerable commercial importance worldwide as functional food due to its organic acids, mucilage, anthocyanins, macro and micro-nutrients content. Although Hibiscus flowers are emerging as very competitive targets for phytochemical studies, very little is known about their volatile composition and or aroma, such knowledge can be suspected to be relevant for understanding its olfactory and taste properties. To provide insight into Hibiscus flower aroma composition and for its future use in food and or pharmaceutical industry, volatile constituents from 2 cultivars grown in Egypt, viz. Aswan and Sudan-1 were profiled using solid-phase microextraction (SPME) coupled to GCMS. A total of 104 volatiles were identified with sugar and fatty acid derived volatiles amounting for the major volatile classes. To reveal for cultivar effect on volatile composition in an untargeted manner, multivariate data analysis was applied. Orthogonal projection to latent structures-discriminant analysis (OPLS-DA) revealed for 1-octen-3-ol versus furfural/acetic acid enrichment in Aswan and Sudan-1 cvs., respectively. Primary metabolites contributing to roselle taste and nutritional value viz. sugars and organic acids were profiled using GC-MS after silylation. The impact of probiotic bacteria on roselle infusion aroma profile was further assessed and revealed for the increase in furfural production with Lactobacillus plantarum inoculation and without affecting its anthocyanin content. This study provides the most complete map for volatiles, sugars and organic acids distribution in two Hibiscus flower cultivars and its fermented product. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. Robust methods for data reduction

    CERN Document Server

    Farcomeni, Alessio

    2015-01-01

    Robust Methods for Data Reduction gives a non-technical overview of robust data reduction techniques, encouraging the use of these important and useful methods in practical applications. The main areas covered include principal components analysis, sparse principal component analysis, canonical correlation analysis, factor analysis, clustering, double clustering, and discriminant analysis.The first part of the book illustrates how dimension reduction techniques synthesize available information by reducing the dimensionality of the data. The second part focuses on cluster and discriminant analy

  20. Optimization of total vaporization solid-phase microextraction (TV-SPME) for the determination of lipid profiles of Phormia regina, a forensically important blow fly species.

    Science.gov (United States)

    Kranz, William; Carroll, Clinton; Dixon, Darren; Picard, Christine; Goodpaster, John

    2017-11-01

    A new method has been developed for the determination of fatty acids, sterols, and other lipids which naturally occur within pupae of the blow fly Phormia regina. The method relies upon liquid extraction in non-polar solvent, followed by derivatization using N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) w/ 1% trimethylchlorsilane (TMCS) carried out inside the sample vial. The analysis is facilitated by total vaporization solid-phase microextraction (TV-SPME), with gas chromatography-mass spectrometry (GC-MS) serving as the instrumentation for analysis. The TV-SPME delivery technique is approximately a factor of five more sensitive than traditional liquid injection, which may alleviate the need for rotary evaporation, reconstitution, collection of high performance liquid chromatography fractions, and many of the other pre-concentration steps that are commonplace in the current literature. Furthermore, the ability to derivatize the liquid extract in a single easy step while increasing sensitivity represents an improvement over current derivatization methods. The most common lipids identified in fly pupae were various saturated and unsaturated fatty acids ranging from lauric acid (12:0) to arachinoic acid (20:4), as well as cholesterol. The concentrations of myristic acid (14:0), palmitelaidic acid (16:2), and palmitoleic acid (16:1) were the most reliable indicators of the age of the pupae. Graphical abstract Blow fly pupae were extracted prior to emerging as adults. The extracts were analyzed via total vaporization solid-phase microextraction (TV-SPME), revealing a complex mixture of lipids that could be associated with the age of the insect. This information may assist in determining a post-mortum interval (PMI) in a death investigation.

  1. Why do Ladybugs Smell Bad? In-vivo Quantification of Odorous Insect Kairomones with SPME and Multidimensional GC-MS-Olfactometry

    International Nuclear Information System (INIS)

    Cai Lingshuang; Koziel, Jacek A.; O'Neal, Matthew E.

    2009-01-01

    Winemakers, small fruit growers, and homeowners are concerned with noxious compounds released by multicolored Asian ladybird beetles (Harmonia axyridis, Coleoptera: Coccinellidae). New method based on headspace solid phase microextraction (HS-SPME) coupled with multidimensional gas chromatography mass spectrometry--olfactometry (MDGC-MS-O) system was developed for extraction, isolation and simultaneous identification of compounds responsible for the characteristic odor of live H. axyridis. Four methoxypyrazines (MPs) were identified in headspace volatiles of live H. axyridis as those responsible for the characteristic odor: 2, 5-dimethy1-3-methoxypyrazine (DMMP), 2-isopropy1-3-methoxypyrazine (IPMP), 2-sec-buty1-3-methoxypyrazine (SBMP), and 2-isobuty1-3-methoxypyrazine (IBMP). To the best of our knowledge this is the first report of H. axyridis releasing DMMP and the first report of this compound being a component of the H. axyridis characteristic odor. Quantification of three MPs (IPMP, SBMP and IBMP) emitted from live H. axyridis were performed using external calibration with HS-SPME and direct injections. A linear relationship (R 2 >0.9958 for all 3 MPs) between MS response and concentration of standard was observed over a concentration range from 0.1 ng L -1 to 0.05 μg L -1 for HS-SPME-GC-MS. The method detection limits (MDL) based on multidimensional GC-MS approach for three MPs were estimated to be between 0.020 ng L -1 . to 0.022 ng L -1 . This methodology is applicable for in vivo determination of odor-causing chemicals associated with emissions of volatiles from insects.

  2. pH-dependent equilibrium isotope fractionation associated with the compound specific nitrogen and carbon isotope analysis of substituted anilines by SPME-GC/IRMS.

    Science.gov (United States)

    Skarpeli-Liati, Marita; Turgeon, Aurora; Garr, Ashley N; Arnold, William A; Cramer, Christopher J; Hofstetter, Thomas B

    2011-03-01

    Solid-phase microextraction (SPME) coupled to gas chromatography/isotope ratio mass spectrometry (GC/IRMS) was used to elucidate the effects of N-atom protonation on the analysis of N and C isotope signatures of selected aromatic amines. Precise and accurate isotope ratios were measured using polydimethylsiloxane/divinylbenzene (PDMS/DVB) as the SPME fiber material at solution pH-values that exceeded the pK(a) of the substituted aniline's conjugate acid by two pH-units. Deviations of δ(15)N and δ(13)C-values from reference measurements by elemental analyzer IRMS were small (IRMS. Under these conditions, the detection limits for accurate isotope ratio measurements were between 0.64 and 2.1 mg L(-1) for δ(15)N and between 0.13 and 0.54 mg L(-1) for δ(13)C, respectively. Substantial inverse N isotope fractionation was observed by SPME-GC/IRMS as the fraction of protonated species increased with decreasing pH leading to deviations of -20‰ while the corresponding δ(13)C-values were largely invariant. From isotope ratio analysis at different solution pHs and theoretical calculations by density functional theory, we derived equilibrium isotope effects, EIEs, pertinent to aromatic amine protonation of 0.980 and 1.001 for N and C, respectively, which were very similar for all compounds investigated. Our work shows that N-atom protonation can compromise accurate compound-specific N isotope analysis of aromatic amines.

  3. SOLID PHASE MICRO EXTRACTION (SPME) FLAVOR ANALYSIS OF APPLE JUICE AND COFFEE MIXTURES USING GAS CHROMATOGRAPHY-MASS SPECTROMETRY (GC-MS)

    OpenAIRE

    Mi Ja Kim; Jeehyun Lee; Jaeyoung Byun; Sunmi Choi; Wonsik Choi

    2016-01-01

    This research was conducted to evaluate the flavor of apple juice and coffee mixtures and the sensory quality of SPME extracts using gas chromatography-mass spectrometry (GC-MS). Three samples with different compositions were examined. Sample A1 contained85% apple juiceand 15% coffee, sample A2 had87.5% apple and 12.5% coffee, and sample A3 had90% apple juiceand 10% coffee. The sensory analysis involved 100 panelists and a sequential monadic test. Sample presentation orders were balanced in ...

  4. Cannabinoids determination in oral fluid by SPME-GC/MS and UHPLC-MS/MS and its application on suspected drivers.

    Science.gov (United States)

    Anzillotti, Luca; Castrignanò, Erika; Strano Rossi, Sabina; Chiarotti, Marcello

    2014-12-01

    The confirmation of Δ9-tetrahydrocannabinol (THC) in oral fluid (OF) is an important issue for assessing Driving Under the Influence of Drugs (DUID). The aim of this research was to develop a highly sensitive method with minimal sample pre-treatment suitable for the analysis of small OF volumes (100 μL) for the confirmation of cannabinoids in DUID cases. Two methods were compared for the confirmation of THC in residual OF samples, obtained from a preliminary on-site screening with commercial devices. An ultra high performance LC-MS (UHPLC-MS/MS) method and an SPME-GC/MS method were hence developed. 100 μL of the residual mixture OF/preservative buffer or neat OF was simply added to 10 μL of THC-D3 (1 μg/mL) and submitted to the two different analyses: A - direct injection of 10 μL in UHPLC-MS/MS in positive electrospray ionisation (ESI) mode and B - sampling for 30 min with SPME (100 μm polydimethylsiloxane or PDMS fibre) and direct injection by desorption of the fibre in the GC injection port. The lowest limit of detection (LLOD) of THC was 2 ng/mL in UHPLC-MS/MS and 0.5 ng/mL in SPME-GC/MS. In addition, cannabidiol (CBD) and cannabinol (CBN) could be detected in GC/MS equipment at 2 ng/mL, whilst in UHPLC-MS/MS the LLOD was 20 ng/mL. Both methods were applied to 70 samples coming from roadside tests. By SPME-GC/MS analysis, THC was confirmed in 42 samples, whilst CBD was detected in 21 of them, along with CBN in 14 samples. THC concentrations ranged from traces below the lowest limit of quantification or LLOQ (2 ng/mL) up to 690 ng/mL. Copyright © 2014 Forensic Science Society. Published by Elsevier Ireland Ltd. All rights reserved.

  5. Robust design optimization using the price of robustness, robust least squares and regularization methods

    Science.gov (United States)

    Bukhari, Hassan J.

    2017-12-01

    In this paper a framework for robust optimization of mechanical design problems and process systems that have parametric uncertainty is presented using three different approaches. Robust optimization problems are formulated so that the optimal solution is robust which means it is minimally sensitive to any perturbations in parameters. The first method uses the price of robustness approach which assumes the uncertain parameters to be symmetric and bounded. The robustness for the design can be controlled by limiting the parameters that can perturb.The second method uses the robust least squares method to determine the optimal parameters when data itself is subjected to perturbations instead of the parameters. The last method manages uncertainty by restricting the perturbation on parameters to improve sensitivity similar to Tikhonov regularization. The methods are implemented on two sets of problems; one linear and the other non-linear. This methodology will be compared with a prior method using multiple Monte Carlo simulation runs which shows that the approach being presented in this paper results in better performance.

  6. A comparison study on a sulfonated graphene-polyaniline nanocomposite coated fiber for analysis of nicotine in solid samples through the traditional and vacuum-assisted HS-SPME.

    Science.gov (United States)

    Ghiasvand, Alireza; Koonani, Samira; Yazdankhah, Fatemeh; Farhadi, Saeid

    2018-02-05

    A simple, rapid, and reliable headspace solid-phase microextraction (HS-SPME) procedure, reinforced by applying vacuum in the extraction vial, was developed. It was applied for the extraction of nicotine in solid samples prior to determination by gas chromatography-flame ionization detection (GC-FID). First, the surface of a narrow stainless steel wire was made porous and adhesive by platinization to obtain a durable, higher surface area, and resistant fiber. Then, a thin film of sulfonated graphene/polyaniline (Sulf-G/PANI) nanocomposite was synthesized and simultaneously coated on the platinized fiber using the electrophoretic deposition (EPD) method. It was demonstrated that the extraction efficiency remarkably increased by applying the reduced-pressure condition in the extraction vial. To evaluate the conventional HS-SPME and vacuum-assisted HS-SPME (VA-HS-SPME) platforms, all experimental parameters affecting the extraction efficiency including desorption time and temperature, extraction time and temperature and moisture content of sample matrix were optimized. The highest extraction efficiency was obtained at 60°C, 10min (extraction temperature and time) and 280°C, 2min (desorption condition), for VA-HS-SPME strategy, while for conventional HS-SPME the extraction and desorption conditions found to be 100°C, 30min and 280°C, 2min, respectively. The Sulf-G/PANI coated fiber showed high thermal stability, good chemical/mechanical resistance, and long lifetime. For analysis of nicotine in solid samples using VA-HS-SPME-GC-FID, linear dynamic range (LDR) was 0.01-30μgg -1 (R 2 =0.996), the relative standard deviation (RSD%, n=6), for analyses of 1μgg -1 nicotine was calculated 3.4% and limit of detection (LOD) found to be 0.002μgg -1 . The VA-HS-SPME-GC-FID strategy was successfully carried out for quantitation of nicotine in hair and tobacco real samples. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Advances in robust fractional control

    CERN Document Server

    Padula, Fabrizio

    2015-01-01

    This monograph presents design methodologies for (robust) fractional control systems. It shows the reader how to take advantage of the superior flexibility of fractional control systems compared with integer-order systems in achieving more challenging control requirements. There is a high degree of current interest in fractional systems and fractional control arising from both academia and industry and readers from both milieux are catered to in the text. Different design approaches having in common a trade-off between robustness and performance of the control system are considered explicitly. The text generalizes methodologies, techniques and theoretical results that have been successfully applied in classical (integer) control to the fractional case. The first part of Advances in Robust Fractional Control is the more industrially-oriented. It focuses on the design of fractional controllers for integer processes. In particular, it considers fractional-order proportional-integral-derivative controllers, becau...

  8. Robustness of digital artist authentication

    DEFF Research Database (Denmark)

    Jacobsen, Robert; Nielsen, Morten

    In many cases it is possible to determine the authenticity of a painting from digital reproductions of the paintings; this has been demonstrated for a variety of artists and with different approaches. Common to all these methods in digital artist authentication is that the potential of the method...... is in focus, while the robustness has not been considered, i.e. the degree to which the data collection process influences the decision of the method. However, in order for an authentication method to be successful in practice, it needs to be robust to plausible error sources from the data collection....... In this paper we investigate the robustness of the newly proposed authenticity method introduced by the authors based on second generation multiresolution analysis. This is done by modelling a number of realistic factors that can occur in the data collection....

  9. Attractive ellipsoids in robust control

    CERN Document Server

    Poznyak, Alexander; Azhmyakov, Vadim

    2014-01-01

    This monograph introduces a newly developed robust-control design technique for a wide class of continuous-time dynamical systems called the “attractive ellipsoid method.” Along with a coherent introduction to the proposed control design and related topics, the monograph studies nonlinear affine control systems in the presence of uncertainty and presents a constructive and easily implementable control strategy that guarantees certain stability properties. The authors discuss linear-style feedback control synthesis in the context of the above-mentioned systems. The development and physical implementation of high-performance robust-feedback controllers that work in the absence of complete information is addressed, with numerous examples to illustrate how to apply the attractive ellipsoid method to mechanical and electromechanical systems. While theorems are proved systematically, the emphasis is on understanding and applying the theory to real-world situations. Attractive Ellipsoids in Robust Control will a...

  10. Robustness of holonomic quantum gates

    International Nuclear Information System (INIS)

    Solinas, P.; Zanardi, P.; Zanghi, N.

    2005-01-01

    Full text: If the driving field fluctuates during the quantum evolution this produces errors in the applied operator. The holonomic (and geometrical) quantum gates are believed to be robust against some kind of noise. Because of the geometrical dependence of the holonomic operators can be robust against this kind of noise; in fact if the fluctuations are fast enough they cancel out leaving the final operator unchanged. I present the numerical studies of holonomic quantum gates subject to this parametric noise, the fidelity of the noise and ideal evolution is calculated for different noise correlation times. The holonomic quantum gates seem robust not only for fast fluctuating fields but also for slow fluctuating fields. These results can be explained as due to the geometrical feature of the holonomic operator: for fast fluctuating fields the fluctuations are canceled out, for slow fluctuating fields the fluctuations do not perturb the loop in the parameter space. (author)

  11. Robust estimation and hypothesis testing

    CERN Document Server

    Tiku, Moti L

    2004-01-01

    In statistical theory and practice, a certain distribution is usually assumed and then optimal solutions sought. Since deviations from an assumed distribution are very common, one cannot feel comfortable with assuming a particular distribution and believing it to be exactly correct. That brings the robustness issue in focus. In this book, we have given statistical procedures which are robust to plausible deviations from an assumed mode. The method of modified maximum likelihood estimation is used in formulating these procedures. The modified maximum likelihood estimators are explicit functions of sample observations and are easy to compute. They are asymptotically fully efficient and are as efficient as the maximum likelihood estimators for small sample sizes. The maximum likelihood estimators have computational problems and are, therefore, elusive. A broad range of topics are covered in this book. Solutions are given which are easy to implement and are efficient. The solutions are also robust to data anomali...

  12. Robustness in Railway Operations (RobustRailS)

    DEFF Research Database (Denmark)

    Jensen, Jens Parbo; Nielsen, Otto Anker

    This study considers the problem of enhancing railway timetable robustness without adding slack time, hence increasing the travel time. The approach integrates a transit assignment model to assess how passengers adapt their behaviour whenever operations are changed. First, the approach considers...

  13. A Robust Design Applicability Model

    DEFF Research Database (Denmark)

    Ebro, Martin; Lars, Krogstie; Howard, Thomas J.

    2015-01-01

    to be applicable in organisations assigning a high importance to one or more factors that are known to be impacted by RD, while also experiencing a high level of occurrence of this factor. The RDAM supplements existing maturity models and metrics to provide a comprehensive set of data to support management......This paper introduces a model for assessing the applicability of Robust Design (RD) in a project or organisation. The intention of the Robust Design Applicability Model (RDAM) is to provide support for decisions by engineering management considering the relevant level of RD activities...

  14. Ins-Robust Primitive Words

    OpenAIRE

    Srivastava, Amit Kumar; Kapoor, Kalpesh

    2017-01-01

    Let Q be the set of primitive words over a finite alphabet with at least two symbols. We characterize a class of primitive words, Q_I, referred to as ins-robust primitive words, which remain primitive on insertion of any letter from the alphabet and present some properties that characterizes words in the set Q_I. It is shown that the language Q_I is dense. We prove that the language of primitive words that are not ins-robust is not context-free. We also present a linear time algorithm to reco...

  15. Gas chromatographic-mass spectrometric analysis of urinary volatile organic metabolites: Optimization of the HS-SPME procedure and sample storage conditions.

    Science.gov (United States)

    Živković Semren, Tanja; Brčić Karačonji, Irena; Safner, Toni; Brajenović, Nataša; Tariba Lovaković, Blanka; Pizent, Alica

    2018-01-01

    Non-targeted metabolomics research of human volatile urinary metabolome can be used to identify potential biomarkers associated with the changes in metabolism related to various health disorders. To ensure reliable analysis of urinary volatile organic metabolites (VOMs) by gas chromatography-mass spectrometry (GC-MS), parameters affecting the headspace-solid phase microextraction (HS-SPME) procedure have been evaluated and optimized. The influence of incubation and extraction temperatures and times, coating fibre material and salt addition on SPME efficiency was investigated by multivariate optimization methods using reduced factorial and Doehlert matrix designs. The results showed optimum values for temperature to be 60°C, extraction time 50min, and incubation time 35min. The proposed conditions were applied to investigate urine samples' stability regarding different storage conditions and freeze-thaw processes. The sum of peak areas of urine samples stored at 4°C, -20°C, and -80°C up to six months showed a time dependent decrease over time although storage at -80°C resulted in a slight non-significant reduction comparing to the fresh sample. However, due to the volatile nature of the analysed compounds, more than two cycles of freezing/thawing of the sample stored for six months at -80°C should be avoided whenever possible. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Optimization of the Extraction of the Volatile Fraction from Honey Samples by SPME-GC-MS, Experimental Design, and Multivariate Target Functions

    Directory of Open Access Journals (Sweden)

    Elisa Robotti

    2017-01-01

    Full Text Available Head space (HS solid phase microextraction (SPME followed by gas chromatography with mass spectrometry detection (GC-MS is the most widespread technique to study the volatile profile of honey samples. In this paper, the experimental SPME conditions were optimized by a multivariate strategy. Both sensitivity and repeatability were optimized by experimental design techniques considering three factors: extraction temperature (from 50°C to 70°C, time of exposition of the fiber (from 20 min to 60 min, and amount of salt added (from 0 to 27.50%. Each experiment was evaluated by Principal Component Analysis (PCA that allows to take into consideration all the analytes at the same time, preserving the information about their different characteristics. Optimal extraction conditions were identified independently for signal intensity (extraction temperature: 70°C; extraction time: 60 min; salt percentage: 27.50% w/w and repeatability (extraction temperature: 50°C; extraction time: 60 min; salt percentage: 27.50% w/w and a final global compromise (extraction temperature: 70°C; extraction time: 60 min; salt percentage: 27.50% w/w was also reached. Considerations about the choice of the best internal standards were also drawn. The whole optimized procedure was than applied to the analysis of a multiflower honey sample and more than 100 compounds were identified.

  17. Development of an SPME-GC-MS method for the specific quantification of dimethylamine and trimethylamine: use of a new ratio for the freshness monitoring of cod fillets.

    Science.gov (United States)

    Dehaut, Alexandre; Duthen, Simon; Grard, Thierry; Krzewinski, Frédéric; N'Guessan, Assi; Brisabois, Anne; Duflos, Guillaume

    2016-08-01

    Fish is a highly perishable food, so it is important to be able to estimate its freshness to ensure optimum quality for consumers. The present study describes the development of an SPME-GC-MS technique capable of quantifying both trimethylamine (TMA) and dimethylamine (DMA), components of what has been defined as partial volatile basic nitrogen (PVB-N). This method was used, together with other reference methods, to monitor the storage of cod fillets (Gadus morhua) conserved under melting ice. Careful optimisation enabled definition of the best parameters for extracting and separating targeted amines and an internal standard. The study of cod spoilage by sensory analysis and TVB-N assay led to the conclusion that the shelf-life of cod fillet was between 6 and 7 days. Throughout the study, TMA and DMA were specifically quantified by SPME-GC-MS; the first was found to be highly correlated with the values returned by steam distillation assays. Neither TMA-N nor DMA-N were able to successfully characterise the decrease in early freshness, unlike dimethylamine/trimethylamine ratio (DTR), whose evolution is closely related to the results of sensory analysis until the stage where fillets need to be rejected. DTR was proposed as a reliable indicator for the early decrease of freshness until fish rejection. © 2015 Society of Chemical Industry. © 2015 Society of Chemical Industry.

  18. High-throughput analysis using non-depletive SPME: challenges and applications to the determination of free and total concentrations in small sample volumes.

    Science.gov (United States)

    Boyacı, Ezel; Bojko, Barbara; Reyes-Garcés, Nathaly; Poole, Justen J; Gómez-Ríos, Germán Augusto; Teixeira, Alexandre; Nicol, Beate; Pawliszyn, Janusz

    2018-01-18

    In vitro high-throughput non-depletive quantitation of chemicals in biofluids is of growing interest in many areas. Some of the challenges facing researchers include the limited volume of biofluids, rapid and high-throughput sampling requirements, and the lack of reliable methods. Coupled to the above, growing interest in the monitoring of kinetics and dynamics of miniaturized biosystems has spurred the demand for development of novel and revolutionary methodologies for analysis of biofluids. The applicability of solid-phase microextraction (SPME) is investigated as a potential technology to fulfill the aforementioned requirements. As analytes with sufficient diversity in their physicochemical features, nicotine, N,N-Diethyl-meta-toluamide, and diclofenac were selected as test compounds for the study. The objective was to develop methodologies that would allow repeated non-depletive sampling from 96-well plates, using 100 µL of sample. Initially, thin film-SPME was investigated. Results revealed substantial depletion and consequent disruption in the system. Therefore, new ultra-thin coated fibers were developed. The applicability of this device to the described sampling scenario was tested by determining the protein binding of the analytes. Results showed good agreement with rapid equilibrium dialysis. The presented method allows high-throughput analysis using small volumes, enabling fast reliable free and total concentration determinations without disruption of system equilibrium.

  19. HP-SPME of volatile polycyclic aromatic hydrocarbons from water using multiwalled carbon nanotubes coated on a steel fiber through electrophoretic deposition

    Energy Technology Data Exchange (ETDEWEB)

    Maghsoudi, S.; Noroozian, E. [Shahid Bahonar Univ., Kerman (Iran, Islamic Republic of). Dept. of Chemistry

    2012-08-15

    A headspace solid-phase microextraction (SPME) method using a stainless steel wire electrophoretically coated with dodecylsulfate modified multiwalled carbon nanotubes was used for the gas chromatographic (GC) determination of polycyclic aromatic hydrocarbons (PAHs) in aqueous samples. Electrophoretic deposition was easily carried out from an aqueous sodium dodecylsulfate medium. The effects of various parameters on the efficiency of SPME process, such as extraction time, extraction temperature, ionic strength, desorption time, and desorption temperature were studied. Under optimized conditions, the detection limits for the various PAHs studied varied from 0.03 to 0.07 ng mL{sup -1}. The inter-day and intra-day relative standard deviations at a 10 ng mL{sup -1} concentration level (n = 7) using a single-fiber were from 5.5 to 9.7 and 4.1 to 8.5 %, respectively. The fiber-to-fiber RSD% (n = 3) was between 7.3 and 11.1 %. The linear ranges were between 0.1 and 100 ng mL{sup -1}. The method was successfully applied to the analysis of a real sample with the recoveries from 88 to 105 % for 5 ng mL{sup -1} and 89 to 101 % for 0.5 ng mL{sup -1} samples. (orig.)

  20. Scalable improvement of SPME multipolar electrostatics in anisotropic polarizable molecular mechanics using a general short-range penetration correction up to quadrupoles.

    Science.gov (United States)

    Narth, Christophe; Lagardère, Louis; Polack, Étienne; Gresh, Nohad; Wang, Qiantao; Bell, David R; Rackers, Joshua A; Ponder, Jay W; Ren, Pengyu Y; Piquemal, Jean-Philip

    2016-02-15

    We propose a general coupling of the Smooth Particle Mesh Ewald SPME approach for distributed multipoles to a short-range charge penetration correction modifying the charge-charge, charge-dipole and charge-quadrupole energies. Such an approach significantly improves electrostatics when compared to ab initio values and has been calibrated on Symmetry-Adapted Perturbation Theory reference data. Various neutral molecular dimers have been tested and results on the complexes of mono- and divalent cations with a water ligand are also provided. Transferability of the correction is adressed in the context of the implementation of the AMOEBA and SIBFA polarizable force fields in the TINKER-HP software. As the choices of the multipolar distribution are discussed, conclusions are drawn for the future penetration-corrected polarizable force fields highlighting the mandatory need of non-spurious procedures for the obtention of well balanced and physically meaningful distributed moments. Finally, scalability and parallelism of the short-range corrected SPME approach are addressed, demonstrating that the damping function is computationally affordable and accurate for molecular dynamics simulations of complex bio- or bioinorganic systems in periodic boundary conditions. Copyright © 2016 Wiley Periodicals, Inc.

  1. Development and validation of automatic HS-SPME with a gas chromatography-ion trap/mass spectrometry method for analysis of volatiles in wines.

    Science.gov (United States)

    Paula Barros, Elisabete; Moreira, Nathalie; Elias Pereira, Giuliano; Leite, Selma Gomes Ferreira; Moraes Rezende, Claudia; Guedes de Pinho, Paula

    2012-11-15

    An automated headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-ion trap/mass spectrometry (GC-IT/MS) was developed in order to quantify a large number of volatile compounds in wines such as alcohols, ester, norisoprenoids and terpenes. The procedures were optimized for SPME fiber selection, pre-incubation temperature and time, extraction temperature and time, and salt addition. A central composite experimental design was used in the optimization of the extraction conditions. The volatile compounds showed optimal extraction using a DVB/CAR/PDMS fiber, incubation of 5 ml of wine with 2g NaCl at 45 °C during 5 min, and subsequent extraction of 30 min at the same temperature. The method allowed the identification of 64 volatile compounds. Afterwards, the method was validated successfully for the most significant compounds and was applied to study the volatile composition of different white wines. Copyright © 2012 Elsevier B.V. All rights reserved.

  2. Essays on robust asset pricing

    NARCIS (Netherlands)

    Horváth, Ferenc

    2017-01-01

    The central concept of this doctoral dissertation is robustness. I analyze how model and parameter uncertainty affect financial decisions of investors and fund managers, and what their equilibrium consequences are. Chapter 1 gives an overview of the most important concepts and methodologies used in

  3. Robust visual hashing via ICA

    International Nuclear Information System (INIS)

    Fournel, Thierry; Coltuc, Daniela

    2010-01-01

    Designed to maximize information transmission in the presence of noise, independent component analysis (ICA) could appear in certain circumstances as a statistics-based tool for robust visual hashing. Several ICA-based scenarios can attempt to reach this goal. A first one is here considered.

  4. Robustness of raw quantum tomography

    Science.gov (United States)

    Asorey, M.; Facchi, P.; Florio, G.; Man'ko, V. I.; Marmo, G.; Pascazio, S.; Sudarshan, E. C. G.

    2011-01-01

    We scrutinize the effects of non-ideal data acquisition on the tomograms of quantum states. The presence of a weight function, schematizing the effects of a finite window or equivalently noise, only affects the state reconstruction procedure by a normalization constant. The results are extended to a discrete mesh and show that quantum tomography is robust under incomplete and approximate knowledge of tomograms.

  5. Robustness of raw quantum tomography

    Energy Technology Data Exchange (ETDEWEB)

    Asorey, M. [Departamento de Fisica Teorica, Facultad de Ciencias, Universidad de Zaragoza, 50009 Zaragoza (Spain); Facchi, P. [Dipartimento di Matematica, Universita di Bari, I-70125 Bari (Italy); INFN, Sezione di Bari, I-70126 Bari (Italy); MECENAS, Universita Federico II di Napoli and Universita di Bari (Italy); Florio, G. [Dipartimento di Fisica, Universita di Bari, I-70126 Bari (Italy); INFN, Sezione di Bari, I-70126 Bari (Italy); MECENAS, Universita Federico II di Napoli and Universita di Bari (Italy); Man' ko, V.I., E-mail: manko@lebedev.r [P.N. Lebedev Physical Institute, Leninskii Prospect 53, Moscow 119991 (Russian Federation); Marmo, G. [Dipartimento di Scienze Fisiche, Universita di Napoli ' Federico II' , I-80126 Napoli (Italy); INFN, Sezione di Napoli, I-80126 Napoli (Italy); MECENAS, Universita Federico II di Napoli and Universita di Bari (Italy); Pascazio, S. [Dipartimento di Fisica, Universita di Bari, I-70126 Bari (Italy); INFN, Sezione di Bari, I-70126 Bari (Italy); MECENAS, Universita Federico II di Napoli and Universita di Bari (Italy); Sudarshan, E.C.G. [Department of Physics, University of Texas, Austin, TX 78712 (United States)

    2011-01-31

    We scrutinize the effects of non-ideal data acquisition on the tomograms of quantum states. The presence of a weight function, schematizing the effects of a finite window or equivalently noise, only affects the state reconstruction procedure by a normalization constant. The results are extended to a discrete mesh and show that quantum tomography is robust under incomplete and approximate knowledge of tomograms.

  6. Aspects of robust linear regression

    NARCIS (Netherlands)

    Davies, P.L.

    1993-01-01

    Section 1 of the paper contains a general discussion of robustness. In Section 2 the influence function of the Hampel-Rousseeuw least median of squares estimator is derived. Linearly invariant weak metrics are constructed in Section 3. It is shown in Section 4 that $S$-estimators satisfy an exact

  7. Manipulation Robustness of Collaborative Filtering

    OpenAIRE

    Benjamin Van Roy; Xiang Yan

    2010-01-01

    A collaborative filtering system recommends to users products that similar users like. Collaborative filtering systems influence purchase decisions and hence have become targets of manipulation by unscrupulous vendors. We demonstrate that nearest neighbors algorithms, which are widely used in commercial systems, are highly susceptible to manipulation and introduce new collaborative filtering algorithms that are relatively robust.

  8. Robustness Regions for Dichotomous Decisions.

    Science.gov (United States)

    Vijn, Pieter; Molenaar, Ivo W.

    1981-01-01

    In the case of dichotomous decisions, the total set of all assumptions/specifications for which the decision would have been the same is the robustness region. Inspection of this (data-dependent) region is a form of sensitivity analysis which may lead to improved decision making. (Author/BW)

  9. Theoretical Framework for Robustness Evaluation

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard

    2011-01-01

    This paper presents a theoretical framework for evaluation of robustness of structural systems, incl. bridges and buildings. Typically modern structural design codes require that ‘the consequence of damages to structures should not be disproportional to the causes of the damages’. However, althou...

  10. Robust control design with MATLAB

    CERN Document Server

    Gu, Da-Wei; Konstantinov, Mihail M

    2013-01-01

    Robust Control Design with MATLAB® (second edition) helps the student to learn how to use well-developed advanced robust control design methods in practical cases. To this end, several realistic control design examples from teaching-laboratory experiments, such as a two-wheeled, self-balancing robot, to complex systems like a flexible-link manipulator are given detailed presentation. All of these exercises are conducted using MATLAB® Robust Control Toolbox 3, Control System Toolbox and Simulink®. By sharing their experiences in industrial cases with minimum recourse to complicated theories and formulae, the authors convey essential ideas and useful insights into robust industrial control systems design using major H-infinity optimization and related methods allowing readers quickly to move on with their own challenges. The hands-on tutorial style of this text rests on an abundance of examples and features for the second edition: ·        rewritten and simplified presentation of theoretical and meth...

  11. Robust Portfolio Optimization Using Pseudodistances

    Science.gov (United States)

    2015-01-01

    The presence of outliers in financial asset returns is a frequently occurring phenomenon which may lead to unreliable mean-variance optimized portfolios. This fact is due to the unbounded influence that outliers can have on the mean returns and covariance estimators that are inputs in the optimization procedure. In this paper we present robust estimators of mean and covariance matrix obtained by minimizing an empirical version of a pseudodistance between the assumed model and the true model underlying the data. We prove and discuss theoretical properties of these estimators, such as affine equivariance, B-robustness, asymptotic normality and asymptotic relative efficiency. These estimators can be easily used in place of the classical estimators, thereby providing robust optimized portfolios. A Monte Carlo simulation study and applications to real data show the advantages of the proposed approach. We study both in-sample and out-of-sample performance of the proposed robust portfolios comparing them with some other portfolios known in literature. PMID:26468948

  12. Facial Symmetry in Robust Anthropometrics

    Czech Academy of Sciences Publication Activity Database

    Kalina, Jan

    2012-01-01

    Roč. 57, č. 3 (2012), s. 691-698 ISSN 0022-1198 R&D Projects: GA MŠk(CZ) 1M06014 Institutional research plan: CEZ:AV0Z10300504 Keywords : forensic science * anthropology * robust image analysis * correlation analysis * multivariate data * classification Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 1.244, year: 2012

  13. Sparse and Robust Factor Modelling

    NARCIS (Netherlands)

    C. Croux (Christophe); P. Exterkate (Peter)

    2011-01-01

    textabstractFactor construction methods are widely used to summarize a large panel of variables by means of a relatively small number of representative factors. We propose a novel factor construction procedure that enjoys the properties of robustness to outliers and of sparsity; that is, having

  14. Robust distributed cognitive relay beamforming

    KAUST Repository

    Pandarakkottilil, Ubaidulla; Aissa, Sonia

    2012-01-01

    design takes into account a parameter of the error in the channel state information (CSI) to render the performance of the beamformer robust in the presence of imperfect CSI. Though the original problem is non-convex, we show that the proposed design can

  15. Approximability of Robust Network Design

    NARCIS (Netherlands)

    Olver, N.K.; Shepherd, F.B.

    2014-01-01

    We consider robust (undirected) network design (RND) problems where the set of feasible demands may be given by an arbitrary convex body. This model, introduced by Ben-Ameur and Kerivin [Ben-Ameur W, Kerivin H (2003) New economical virtual private networks. Comm. ACM 46(6):69-73], generalizes the

  16. Comparison of the atmospheric- and reduced-pressure HS-SPME strategies for analysis of residual solvents in commercial antibiotics using a steel fiber coated with a multiwalled carbon nanotube/polyaniline nanocomposite.

    Science.gov (United States)

    Ghiasvand, Ali Reza; Nouriasl, Kolsoum; Yazdankhah, Fatemeh

    2018-01-01

    A low-cost, sensitive and reliable reduced-pressure headspace solid-phase microextraction (HS-SPME) setup was developed and evaluated for direct extraction of residual solvents in commercial antibiotics, followed by determination by gas chromatography with flame ionization detection (GC-FID). A stainless steel narrow wire was made porous and adhesive by platinization by a modified electrophoretic deposition method and coated with a polyaniline/multiwalled carbon nanotube nanocomposite. All experimental variables affecting the extraction efficiency were investigated for both atmospheric-pressure and reduced-pressure conditions. Comparison of the optimal experimental conditions and the results demonstrated that the reduced-pressure strategy leads to a remarkable increase in the extraction efficiency and reduction of the extraction time and temperature (10 min, 25 °Ϲ vs 20 min, 40 °Ϲ). Additionally, the reduced-pressure strategy showed better analytical performances compared with those obtained by the conventional HS-SPME-GC-FID method. Limit of detections, linear dynamic ranges, and relative standard deviations of the reduced-pressure HS-SPME procedure for benzene, toluene, ethylbenzene, and xylene (BTEX) in injectable solid drugs were obtained over the ranges of 20-100 pg g -1 , 0.02-40 μg g -1 , and 2.8-10.2%, respectively. The procedure developed was successful for the analysis of BTEX in commercial containers of penicillin, ampicillin, ceftriaxone, and cefazolin. Graphical abstract Schematic representation of the developed RP-HS-SPME setup.

  17. Comparative Analyses of the Volatile Components of Citrus Aurantium L. Flowers Using Ultrasonic-Assisted Headspace SPME and Hydrodistillation Combined with GC-MS and Evaluation of their Antimicrobial Activities

    Directory of Open Access Journals (Sweden)

    Akram Rahimi

    2014-12-01

    Full Text Available The volatile components of Citrus aurantium L. flowers were characterized by GC-MS with two different extraction techniques, hydrodistillation (HD and ultrasonic-assisted headspace solid phase microextraction (UA-HS-SPME. In the SPME method, the volatile components of the samples, irradiated by ultrasonic radiation, were collected on a polydimethyl siloxane (PDMS commercial fiber as well as some manually prepared nanoporous fibers from the samples headspace. To reach the better results, the extraction conditions were carefully optimized for the PDMS fiber. Under the optimized conditions (i.e. sonication time 15 min, extraction time 30 min and extraction temperature 55 ºC, 54 compounds were identified by the UA-HS-SPME-GC/MS method. The essential oil components of Citrus aurantium L. flower samples from two different regions of Iran and new and old samples from the same region were compared to one another. The major components identified for the samples with both the SPME and HD methods were linalool, linalyl acetate, limonene, β-myrcene, geranyl acetate, and neryl acetate, respectively. However, a substantial variation in the percentages of the components was identified for different samples and different extraction methods. The antimicrobial activities of the oil were also examined against six standard bacteria. There was some activity against Enterococcus fecalis, Escherichia coli, and Bacillus cereus, indicating important biological activities of the oil.

  18. Robust Reliability or reliable robustness? - Integrated consideration of robustness and reliability aspects

    DEFF Research Database (Denmark)

    Kemmler, S.; Eifler, Tobias; Bertsche, B.

    2015-01-01

    products are and vice versa. For a comprehensive understanding and to use existing synergies between both domains, this paper discusses the basic principles of Reliability- and Robust Design theory. The development of a comprehensive model will enable an integrated consideration of both domains...

  19. Robust Watermarking of Video Streams

    Directory of Open Access Journals (Sweden)

    T. Polyák

    2006-01-01

    Full Text Available In the past few years there has been an explosion in the use of digital video data. Many people have personal computers at home, and with the help of the Internet users can easily share video files on their computer. This makes possible the unauthorized use of digital media, and without adequate protection systems the authors and distributors have no means to prevent it.Digital watermarking techniques can help these systems to be more effective by embedding secret data right into the video stream. This makes minor changes in the frames of the video, but these changes are almost imperceptible to the human visual system. The embedded information can involve copyright data, access control etc. A robust watermark is resistant to various distortions of the video, so it cannot be removed without affecting the quality of the host medium. In this paper I propose a video watermarking scheme that fulfills the requirements of a robust watermark. 

  20. Robust Decentralized Formation Flight Control

    Directory of Open Access Journals (Sweden)

    Zhao Weihua

    2011-01-01

    Full Text Available Motivated by the idea of multiplexed model predictive control (MMPC, this paper introduces a new framework for unmanned aerial vehicles (UAVs formation flight and coordination. Formulated using MMPC approach, the whole centralized formation flight system is considered as a linear periodic system with control inputs of each UAV subsystem as its periodic inputs. Divided into decentralized subsystems, the whole formation flight system is guaranteed stable if proper terminal cost and terminal constraints are added to each decentralized MPC formulation of the UAV subsystem. The decentralized robust MPC formulation for each UAV subsystem with bounded input disturbances and model uncertainties is also presented. Furthermore, an obstacle avoidance control scheme for any shape and size of obstacles, including the nonapriorily known ones, is integrated under the unified MPC framework. The results from simulations demonstrate that the proposed framework can successfully achieve robust collision-free formation flights.

  1. Inefficient but robust public leadership.

    OpenAIRE

    Matsumura, Toshihiro; Ogawa, Akira

    2014-01-01

    We investigate endogenous timing in a mixed duopoly in a differentiated product market. We find that private leadership is better than public leadership from a social welfare perspective if the private firm is domestic, regardless of the degree of product differentiation. Nevertheless, the public leadership equilibrium is risk-dominant, and it is thus robust if the degree of product differentiation is high. We also find that regardless of the degree of product differentiation, the public lead...

  2. Testing Heteroscedasticity in Robust Regression

    Czech Academy of Sciences Publication Activity Database

    Kalina, Jan

    2011-01-01

    Roč. 1, č. 4 (2011), s. 25-28 ISSN 2045-3345 Grant - others:GA ČR(CZ) GA402/09/0557 Institutional research plan: CEZ:AV0Z10300504 Keywords : robust regression * heteroscedasticity * regression quantiles * diagnostics Subject RIV: BB - Applied Statistics , Operational Research http://www.researchjournals.co.uk/documents/Vol4/06%20Kalina.pdf

  3. Robust power system frequency control

    CERN Document Server

    Bevrani, Hassan

    2014-01-01

    This updated edition of the industry standard reference on power system frequency control provides practical, systematic and flexible algorithms for regulating load frequency, offering new solutions to the technical challenges introduced by the escalating role of distributed generation and renewable energy sources in smart electric grids. The author emphasizes the physical constraints and practical engineering issues related to frequency in a deregulated environment, while fostering a conceptual understanding of frequency regulation and robust control techniques. The resulting control strategi

  4. Development of a Microfluidic Open Interface with Flow Isolated Desorption Volume for the Direct Coupling of SPME Devices to Mass Spectrometry.

    Science.gov (United States)

    Tascon, Marcos; Alam, Md Nazmul; Gómez-Ríos, Germán Augusto; Pawliszyn, Janusz

    2018-02-20

    Technologies that efficiently integrate the sampling and sample preparation steps with direct introduction to mass spectrometry (MS), providing simple and sensitive analytical workflows as well as capabilities for automation, can generate a great impact in a vast variety of fields, such as in clinical, environmental, and food-science applications. In this study, a novel approach that facilitates direct coupling of Bio-SPME devices to MS using a microfluidic design is presented. This technology, named microfluidic open interface (MOI), which operates under the concept of flow-isolated desorption volume, consists of an open-to-ambient desorption chamber (V ≤ 7 μL) connected to an ionization source. Subsequently, compounds of interest are transported to the ionization source by means of the self-aspiration process intrinsic of these interfaces. Thus, any ionization technology that provides a reliable and constant suction, such as electrospray ionization (ESI), atmospheric-pressure chemical ionization (APCI), or inductively coupled plasma ionization (ICP), can be hyphenated to MOI. Using this setup, the desorption chamber is used to release target compounds from the coating, while the isolation of the flow enables the ionization source to be continuously fed with solvent, all without the necessity of employment of additional valves. As a proof of concept, the design was applied to an ESI-MS/MS system for experimental validation. Furthermore, numerical simulations were undertaken to provide a detailed understanding of the fluid flow pattern inside the interface, then used to optimize the system for better efficiency. The analytical workflow of the developed Bio-SPME-MOI-MS setup consists of the direct immersion of SPME fibers into the matrix to extract/enrich analytes of interest within a short period of time, followed by a rinsing step with water to remove potentially adhering proteins, salts, and/or other interfering compounds. Next, the fiber is inserted into the

  5. Comparison of common components analysis with principal components analysis and independent components analysis: Application to SPME-GC-MS volatolomic signatures.

    Science.gov (United States)

    Bouhlel, Jihéne; Jouan-Rimbaud Bouveresse, Delphine; Abouelkaram, Said; Baéza, Elisabeth; Jondreville, Catherine; Travel, Angélique; Ratel, Jérémy; Engel, Erwan; Rutledge, Douglas N

    2018-02-01

    The aim of this work is to compare a novel exploratory chemometrics method, Common Components Analysis (CCA), with Principal Components Analysis (PCA) and Independent Components Analysis (ICA). CCA consists in adapting the multi-block statistical method known as Common Components and Specific Weights Analysis (CCSWA or ComDim) by applying it to a single data matrix, with one variable per block. As an application, the three methods were applied to SPME-GC-MS volatolomic signatures of livers in an attempt to reveal volatile organic compounds (VOCs) markers of chicken exposure to different types of micropollutants. An application of CCA to the initial SPME-GC-MS data revealed a drift in the sample Scores along CC2, as a function of injection order, probably resulting from time-related evolution in the instrument. This drift was eliminated by orthogonalization of the data set with respect to CC2, and the resulting data are used as the orthogonalized data input into each of the three methods. Since the first step in CCA is to norm-scale all the variables, preliminary data scaling has no effect on the results, so that CCA was applied only to orthogonalized SPME-GC-MS data, while, PCA and ICA were applied to the "orthogonalized", "orthogonalized and Pareto-scaled", and "orthogonalized and autoscaled" data. The comparison showed that PCA results were highly dependent on the scaling of variables, contrary to ICA where the data scaling did not have a strong influence. Nevertheless, for both PCA and ICA the clearest separations of exposed groups were obtained after autoscaling of variables. The main part of this work was to compare the CCA results using the orthogonalized data with those obtained with PCA and ICA applied to orthogonalized and autoscaled variables. The clearest separations of exposed chicken groups were obtained by CCA. CCA Loadings also clearly identified the variables contributing most to the Common Components giving separations. The PCA Loadings did not

  6. Determinação do coeficiente de atividade na diluição infinita (g¥ através da micro-extração em fase sólida (SPME Determination of activity coefficients at infinite dilution through solid phase microextraction (SPME

    Directory of Open Access Journals (Sweden)

    Douglas B. Fonseca

    2007-01-01

    Full Text Available In this study a new approach, solid phase micro extraction (SPME, is used in the evaluation of the infinite dilution activity coefficient of the solute in a given solvent. It is the purpose of the current work to demonstrate a different approach to obtain the data needed for studying the solution thermodynamics of binary liquid mixtures as well as for designing multi-component separations. The solutes investigated at the temperature 298.15 K were toluene, ethyl benzene and xylene in the solvent methanol.

  7. Comparative study of volatile components from male and female flower buds of Populus × tomentosa by HS-SPME-GC-MS.

    Science.gov (United States)

    Xu, Liang; Liu, Haiping; Ma, Yucui; Wu, Cui; Li, Ruiqi; Chao, Zhimao

    2018-06-13

    The differences of volatile components in male (MFB) and female flower buds (FFB) of Populus × tomentosa were analysed and compared by HS-SPME with GC-MS for the first time. A total of 34 compounds were identified. Two clusters were clearly divided into male and female by hierarchical clustering analysis. Both the male and female flower buds showed methyl salicylate (22.83 and 24.09%, respectively) and 2-hydroxy-benzaldehyde (10.05 and 12.41%, respectively) as the main volatile constituents. The content of 2-cyclohexen-1-one, benzyl benzoate, and methyl benzoate in FFB was remarkably higher than in MFB. In contrast, the content of ethyl benzoate in MFB was greater than that in FFB. The phenomena showed the characteristic differences between MFB and FFB of P. × tomentosa, which enriched the basic studies on dioecious plant.

  8. Quantitative Profiling of Ester Compounds Using HS-SPME-GC-MS and Chemometrics for Assessing Volatile Markers of the Second Fermentation in Bottle.

    Science.gov (United States)

    Muñoz-Redondo, José Manuel; Cuevas, Francisco Julián; León, Juan Manuel; Ramírez, Pilar; Moreno-Rojas, José Manuel; Ruiz-Moreno, María José

    2017-04-05

    A quantitative approach using HS-SPME-GC-MS was performed to investigate the ester changes related to the second fermentation in bottle. The contribution of the type of base wine to the final wine style is detailed. Furthermore, a discriminant model was developed based on ester changes according to the second fermentation (with 100% sensitivity and specificity values). The application of a double-check criteria according to univariate and multivariate analyses allowed the identification of potential volatile markers related to the second fermentation. Some of them presented a synthesis-ratio around 3-fold higher after this period and they are known to play a key role in wine aroma. Up to date, this is the first study reporting the role of esters as markers of the second fermentation. The methodology described in this study confirmed its suitability for the wine aroma field. The results contribute to enhance our understanding of this fermentative step.

  9. Differentiation of Commercial PDO Wines Produced in Istria (Croatia According to Variety and Harvest Year Based on HS-SPME-GC/MS Volatile Aroma Compound Profiling

    Directory of Open Access Journals (Sweden)

    Igor Lukić

    2017-01-01

    Full Text Available To differentiate monovarietal wines made from native and introduced varieties in Istria (Croatia, samples of Malvazija istarska, Chardonnay and Muscat yellow from two harvest years (2013 and 2014 were subjected to headspace solid-phase microextraction and gas chromatographic/mass spectrometric analysis (HS-SPME-GC/MS of volatile aroma compounds. Significant effects of variety and harvest year were determined, but their interaction complicated the differentiation. Particular compounds were consistent as markers of variety in both years: nerol for Malvazija, ethyl cinnamate and a tentatively identified isomer of dimethylbenzaldehyde for Chardonnay, and terpenes for Muscat yellow. Wines from 2013 contained higher concentrations of the majority of important volatiles. A 100 % correct differentiation of Malvazija istarska and Chardonnay wines according to both variety and harvest year was achieved by stepwise linear discriminant analysis.

  10. Optimization of the HS-SPME-GC/MS technique for the analysis of volatile compounds in caprine Coalho cheese using response surface methodology

    Directory of Open Access Journals (Sweden)

    Taliana Kênia Alves BEZERRA

    2016-03-01

    Full Text Available Abstract Caprine Coalho cheese presents great potential for a typical protected designation of origin, considering that this traditional Brazilian cheese presents a slightly salty and acid flavor, combined with a unique texture. This study optimized the HS-SPME-GC-MS methodology for volatile analysis of Coalho cheese, which can be used as a tool to help in the identification of the distinctive aroma profile of this cheese. The conditions of equilibrium time, extraction temperature and time were optimized using the statistical tool factorial experimental design 23, and applying the desirability function. After the evaluation, it was concluded that the optimum extraction conditions comprised equilibrium and extraction time of 20 and 40 minutes, respectively; and ideal extraction temperature of 45 °C. The optimum extraction of volatile compounds in goat Coalho cheese captured 32 volatile compounds: 5 alcohols, 5 esters, 3 ketones, 6 acids, 3 aldehydes, 3 terpenes, and 7 hydrocarbons.

  11. Characterisation of volatile profiles in 50 native Peruvian chili pepper using solid phase microextraction-gas chromatography mass spectrometry (SPME-GCMS).

    Science.gov (United States)

    Patel, Kirti; Ruiz, Candy; Calderon, Rosa; Marcelo, Mavel; Rojas, Rosario

    2016-11-01

    The volatiles were characterised by headspace solid phase micro extraction (HS-SPME), gas chromatography mass spectrometry (GC-FID/MS). A total of 127 compounds were identified with terpenes (including mono terpenes and sesquiterpenes - a total of 45 compounds), esters (31 compounds) and hydrocarbons (20 compounds) were the predominant volatile compounds. Principal component analysis (PCA) of the volatile compounds yielded 2 significant PC's, which together accounted for 90.3% of the total variance in the data set and the scatter plot generated between PC1 and PC2 successfully segregated the 50 chili pepper samples into 7 groups. Clusters of hydrocarbons, esters, terpenes, aldehyde and ketones formed the major determinants of the difference. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Greek Salvia sclarea L. Essential Oils: Effect of Hydrodistillation Time, Comparison of the Aroma Chemicals Using Hydrodistillation and HS-SPME Techniques

    Directory of Open Access Journals (Sweden)

    Aikaterini Koutsaviti

    2016-05-01

    Full Text Available Since the essential oil of Salvia sclarea is used as a flavouring agent, the effect of different extraction techniques (hydrodistillation & HS-SPME and duration of hydrodistillation (2, 3 and 4 h with respect to yield, composition and identification rate of extracted essential oils from Greek cultivated S. sclarea aerial blooming parts were investigated. Linalool and linalyl acetate levels seemed to decrease with increasing duration of hydrodistillation, while diterpenes increased dramatically, while the head space analysis showed significantly lower levels of linalool in comparison to its ester. Thus, linalool (5.1-35.8%, linalyl acetate (11.3-37.6% and sclareol (0.0-41.8%, concerning the oils obtained by hydrodistillation, were the most important metabolites. Solid-phase microextraction yielded mainly oxygenated monoterpenes, especially linalyl acetate (59.3%, followed by cis-linalool oxide (8.6% and linalool (7.8%.

  13. Microextraction by Packed Sorbent (MEPS and Solid-Phase Microextraction (SPME as Sample Preparation Procedures for the Metabolomic Profiling of Urine

    Directory of Open Access Journals (Sweden)

    Catarina Silva

    2014-01-01

    Full Text Available For a long time, sample preparation was unrecognized as a critical issue in the analytical methodology, thus limiting the performance that could be achieved. However, the improvement of microextraction techniques, particularly microextraction by packed sorbent (MEPS and solid-phase microextraction (SPME, completely modified this scenario by introducing unprecedented control over this process. Urine is a biological fluid that is very interesting for metabolomics studies, allowing human health and disease characterization in a minimally invasive form. In this manuscript, we will critically review the most relevant and promising works in this field, highlighting how the metabolomic profiling of urine can be an extremely valuable tool for the early diagnosis of highly prevalent diseases, such as cardiovascular, oncologic and neurodegenerative ones.

  14. Assessing a traceability technique in fresh oranges (Citrus sinensis L. Osbeck) with an HS-SPME-GC-MS method. Towards a volatile characterisation of organic oranges.

    Science.gov (United States)

    Cuevas, Francisco Julián; Moreno-Rojas, José Manuel; Ruiz-Moreno, María José

    2017-04-15

    A targeted approach using HS-SPME-GC-MS was performed to compare flavour compounds of 'Navelina' and 'Salustiana' orange cultivars from organic and conventional management systems. Both varieties of conventional oranges showed higher content of ester compounds. On the other hand, higher content of some compounds related with the geranyl-diphosphate pathway (neryl and geranyl acetates) and some terpenoids were found in the organic samples. Furthermore, the partial least square discriminant analysis (PLS-DA) achieved an effective classification for oranges based on the farming system using their volatile profiles (90 and 100% correct classification). To our knowledge, it is the first time that a comparative study dealing with farming systems and orange aroma profile has been performed. These new insights, taking into account local databases, cultivars and advanced analytical tools, highlight the potential of volatile composition for organic orange discrimination. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Comparison and characterization of volatile compounds as markers of oils stability during frying by HS-SPME-GC/MS and Chemometric analysis.

    Science.gov (United States)

    Ben Hammouda, Ibtissem; Freitas, Flavia; Ammar, Sonda; Da Silva, M D R Gomes; Bouaziz, Mohamed

    2017-11-15

    The formation and emission of volatile compounds, including the aldehydes and some toxic compounds of oil samples, ROPO pure (100%) and the blended ROPO/RCO (80-20%), were carried out during deep frying at 180°C. The volatile profile of both oil samples was evaluated by an optimized HS-SPME-GC/MS method, before and after 20, 40 and 60 successive sessions of deep-frying. Actually, from 100 detected compounds, aldehydes were found to be the main group formed. In addition, the oil degradation under thermal treatment regarding the volatile compounds were evaluated and compared. Consequently, the blended ROPO/RCO revealed fewer formations of unsaturated aldehydes, including toxic ones, such as acrolein, and showed a greater stability against oxidative thermal degradation compared to ROPO pure. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Differentiation of Commercial PDO Wines Produced in Istria (Croatia) According to Variety and Harvest Year Based on HS-SPME-GC/MS Volatile Aroma Compound Profiling.

    Science.gov (United States)

    Lukić, Igor; Horvat, Ivana

    2017-03-01

    To differentiate monovarietal wines made from native and introduced varieties in Istria (Croatia), samples of Malvazija istarska, Chardonnay and Muscat yellow from two harvest years (2013 and 2014) were subjected to headspace solid-phase microextraction and gas chromatographic/mass spectrometric analysis (HS-SPME-GC/MS) of volatile aroma compounds. Significant effects of variety and harvest year were determined, but their interaction complicated the differentiation. Particular compounds were consistent as markers of variety in both years: nerol for Malvazija, ethyl cinnamate and a tentatively identified isomer of dimethylbenzaldehyde for Chardonnay, and terpenes for Muscat yellow. Wines from 2013 contained higher concentrations of the majority of important volatiles. A 100% correct differentiation of Malvazija istarska and Chardonnay wines according to both variety and harvest year was achieved by stepwise linear discriminant analysis.

  17. Estudio analítico de MTA-Angelus® y Biodentine® con técnicas SPME-GCMS y AFM

    OpenAIRE

    Díaz-Flores García, Víctor; Martínez Pérez, Lucía; Escribano Otero, Amparo; Kayali Sayadi, Nour

    2016-01-01

    Introducción: El objetivo del estudio fue obtener información analítica sobre la pureza química y homogeneidad de los materiales de uso endodóntico MTA-Angelus® y Biodentine®. Material y métodos: Se analizaron ambos materiales mediante la técnica de microextracción en fase sólida (SPME), combinada con cromatografía de gases acoplada a espectrómetro de masas (GC-MS) para separar e identificar los compuestos orgánicos volátiles (COVs) contenidos. Por otro lado, utilizando microscopía de f...

  18. Characterization of French and Spanish dry-cured hams: influence of the volatiles from the muscles and the subcutaneous fat quantified by SPME-GC.

    Science.gov (United States)

    Sánchez-Peña, Carolina M; Luna, Guadalupe; García-González, Diego L; Aparicio, Ramón

    2005-04-01

    The influence of the volatile compounds on the characterization of Spanish and French dry-cured hams was studied. Thirty volatiles were quantified in each one of four locations (biceps femoris, semimembranosus and semitendinosus muscles and subcutaneous fat) of 29 dry-cured hams by solid-phase microextraction gas-chromatography (SPME-GC). The Brown-Forsythe univariate test allowed determination of the volatiles that individually could characterize (p0.95), then selected the most remarkable volatile compounds. Four compounds from the subcutaneous fat (methyl benzene and octanol) and the semitendinosus muscle (2-butanone and 2-octanone) allowed 100% correct classifications by geographic origin. On the other hand, only two compounds from the subcutaneous fat (octanol) and the biceps femoris muscle (3-methyl 1-butanol) correctly classified all the samples by the breed type. The ability of these variables to classify the samples was checked by the unsupervised procedure of principal components.

  19. Odor Profile of Different Varieties of Extra-Virgin Olive Oil During Deep Frying Using an Electronic Nose and SPME-GC-FID

    Science.gov (United States)

    Messina, Valeria; Biolatto, Andrea; Sancho, Ana; Descalzo, Adriana; Grigioni, Gabriela; de Reca, Noemí Walsöe

    2011-09-01

    The aim of the performed work was to evaluate with an electronic nose changes in odor profile of Arauco and Arbequina varieties of extra-virgin olive oil during deep-frying. Changes in odor were analyzed using an electronic nose composed of 16 sensors. Volatile compounds were analyzed by SPME-GC-FID. Principal Component Analysis was applied for electronic results. Arauco variety showed the highest response for sensors. Statistical analysis for volatile compounds indicated a significant (P<0.001) interaction between variety and time of frying processes. Arauco variety showed the highest production of volatile compounds at 60 min of deep frying. The two varieties presented distinct patterns of volatile products, being clearly identified with the electronic nose.

  20. Robustness Analysis of Timber Truss Structure

    DEFF Research Database (Denmark)

    Rajčić, Vlatka; Čizmar, Dean; Kirkegaard, Poul Henning

    2010-01-01

    The present paper discusses robustness of structures in general and the robustness requirements given in the codes. Robustness of timber structures is also an issues as this is closely related to Working group 3 (Robustness of systems) of the COST E55 project. Finally, an example of a robustness...... evaluation of a widespan timber truss structure is presented. This structure was built few years ago near Zagreb and has a span of 45m. Reliability analysis of the main members and the system is conducted and based on this a robustness analysis is preformed....

  1. Multiple internal standard normalization for improving HS-SPME-GC-MS quantitation in virgin olive oil volatile organic compounds (VOO-VOCs) profile.

    Science.gov (United States)

    Fortini, Martina; Migliorini, Marzia; Cherubini, Chiara; Cecchi, Lorenzo; Calamai, Luca

    2017-04-01

    The commercial value of virgin olive oils (VOOs) strongly depends on their classification, also based on the aroma of the oils, usually evaluated by a panel test. Nowadays, a reliable analytical method is still needed to evaluate the volatile organic compounds (VOCs) and support the standard panel test method. To date, the use of HS-SPME sampling coupled to GC-MS is generally accepted for the analysis of VOCs in VOOs. However, VOO is a challenging matrix due to the simultaneous presence of: i) compounds at ppm and ppb concentrations; ii) molecules belonging to different chemical classes and iii) analytes with a wide range of molecular mass. Therefore, HS-SPME-GC-MS quantitation based upon the use of external standard method or of only a single internal standard (ISTD) for data normalization in an internal standard method, may be troublesome. In this work a multiple internal standard normalization is proposed to overcome these problems and improving quantitation of VOO-VOCs. As many as 11 ISTDs were used for quantitation of 71 VOCs. For each of them the most suitable ISTD was selected and a good linearity in a wide range of calibration was obtained. Except for E-2-hexenal, without ISTD or with an unsuitable ISTD, the linear range of calibration was narrower with respect to that obtained by a suitable ISTD, confirming the usefulness of multiple internal standard normalization for the correct quantitation of VOCs profile in VOOs. The method was validated for 71 VOCs, and then applied to a series of lampante virgin olive oils and extra virgin olive oils. In light of our results, we propose the application of this analytical approach for routine quantitative analyses and to support sensorial analysis for the evaluation of positive and negative VOOs attributes. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Assessment of Volatile Chemical Composition of the Essential Oil of Jatropha ribifolia (Pohl Baill by HS-SPME-GC-MS Using Different Fibers

    Directory of Open Access Journals (Sweden)

    Celia Eliane de Lara da Silva

    2013-01-01

    Full Text Available The chemical composition of essential oil and volatile obtained from the roots of Jatropha ribifolia (Pohl Baill was performed in this work. The Clevenger extractor was utilized in hydrodistillation of oil and chemical composition determined by gas chromatography coupled with mass spectrometry detector (GC-MS. The identification of compounds was confirmed by retention index (Kovats index obtained from a series of straight chain alkanes (C7–C30 and by comparison with NIST and ADAMS library. A total of 61 compounds were identified in essential oil by GC-MS. The extraction of volatile was performed also by the use of the solid phase microextraction (SPME with four different fibers. The essential oil extraction was extremely rapid (15 s to avoid saturation of the fiber and the MS detector. The majority of the composition of essential oil is the terpenes: β-pinene (major compound 9.16%, β-vatirene (8.34%, α-gurjunene (6.98%, α-pinene (6.35%, camphene (4.34%, tricyclene (3.79% and dehydro aromadendrene (3.52% it and aldehydes and alcohols. Through the SPME it was possible to determine the nine volatile compounds not identified in oil 2,3,4-trimethyl-2-cyclopenten-1-one, α-phellandrene, 3-carene, trans-p-mentha-2,8-dienol, pinocamphone, D-verbenon, 1,3,3-trimethyl-2-(2-methyl-cyclopropyl-cyclohexene, 2,4-diisocyanato-1-methylbenzene, and (6-hydroxymethyl-2,3-dimethylehenyl methanol.

  3. Optimization of biological and instrumental detection of explosives and ignitable liquid residues including canines, SPME/ITMS and GC/MSn

    Science.gov (United States)

    Furton, Kenneth G.; Harper, Ross J.; Perr, Jeannette M.; Almirall, Jose R.

    2003-09-01

    A comprehensive study and comparison is underway using biological detectors and instrumental methods for the rapid detection of ignitable liquid residues (ILR) and high explosives. Headspace solid phase microextraction (SPME) has been demonstrated to be an effective sampling method helping to identify active odor signature chemicals used by detector dogs to locate forensic specimens as well as a rapid pre-concentration technique prior to instrumental detection. Common ignitable liquids and common military and industrial explosives have been studied including trinitrotoluene, tetryl, RDX, HMX, EGDN, PETN and nitroglycerine. This study focuses on identifying volatile odor signature chemicals present, which can be used to enhance the level and reliability of detection of ILR and explosives by canines and instrumental methods. While most instrumental methods currently in use focus on particles and on parent organic compounds, which are often involatile, characteristic volatile organics are generally also present and can be exploited to enhance detection particularly for well-concealed devices. Specific examples include the volatile odor chemicals 2-ethyl-1-hexanol and cyclohexanone, which are readily available in the headspace of the high explosive composition C-4; whereas, the active chemical cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX) is not. The analysis and identification of these headspace 'fingerprint' organics is followed by double-blind dog trials of the individual components using certified teams in an attempt to isolate and understand the target compounds to which dogs are sensitive. Studies to compare commonly used training aids with the actual target explosive have also been undertaken to determine their suitability and effectiveness. The optimization of solid phase microextraction (SPME) combined with ion trap mobility spectrometry (ITMS) and gas chromatography/mass spectrometry/mass spectrometry (GC/MSn) is detailed including interface development

  4. Use of solid-phase microextraction (SPME) for the determination of methadone and EDDP in human hair by GC-MS.

    Science.gov (United States)

    Lucas, A C; Bermejo, A M; Tabernero, M J; Fernández, P; Strano-Rossi, S

    2000-01-10

    Solid-phase microextraction (SPME) is a new extraction technique with many advantages: small sample volume, simplicity, quickness and solvent-free. It is mainly applied to environmental analysis, but is also useful for the extraction of drugs from biological samples. In this paper the use of SPME is proposed for the determination of methadone and its main metabolite EDDP in hair by GC-MS. The hair samples were washed, cut into 1-mm segments, and incubated with Pronase E for 12 h. A 100-micron polydimethylsiloxane (PDMS) film fibre was submerged for 30 min in a diluted solution of the hydrolysis liquid (1:4 with borax buffer) containing methadone-d3 and EDDP-d3 as internal standards. Once the microextraction was concluded the fibre was directly inserted into the CG injection port. Linearity was found for methadone and EDDP in the range studied, 1.0-50 ng/mg hair, with correlation coefficients higher than 0.99. Interassay relative standard deviation (R.S.D) was determined to be less than 13.30% for methadone and less than 8.94% for EDDP, at 3.0 and 30.0 ng/mg. Analytical recoveries were close to 100% for both compounds on spiked samples. The method was applied to the analysis of real hair samples from eight patients of a methadone maintenance programme. The concentration of methadone in hair ranged from 2.45 to 78.10 ng/mg, and for EDDP from 0.98 to 7.76 ng/mg of hair.

  5. NMR investigation of acrolein stability in hydroalcoholic solution as a foundation for the valid HS-SPME/GC–MS quantification of the unsaturated aldehyde in beverages

    International Nuclear Information System (INIS)

    Kächele, Martin; Monakhova, Yulia B.; Kuballa, Thomas; Lachenmeier, Dirk W.

    2014-01-01

    Highlights: • Acrolein in hydroalcoholic solution degrades to 1,3,3-propanetriol and 3-hydroxypropionaldehyde. • Hydroquinone (0.2%) at pH 3.0 stabilizes acrolein solutions. • Quantitative HS-SPME/GC–MS determination of acrolein in alcoholic beverages was developed (LOD 14 μg L −1 ). • 6 of 117 samples had acrolein levels above the WHO threshold (1500 μg L −1 ). - Abstract: Acrolein (propenal) is found in many foods and beverages and may pose a health hazard due to its cytotoxicity. Considerable knowledge gaps regarding human exposure to acrolein exist, and there is a lack of reliable analytical methods. Hydroalcoholic dilutions prepared for calibration purposes from pure acrolein show considerable degradation of the compound and nuclear magnetic resonance (NMR) spectroscopy showed that 1,3,3-propanetriol and 3-hydroxypropionaldehyde are formed. The degradation can be prevented by addition of hydroquinone as stabilizer to the calibration solutions, which then show linear concentration-response behaviour required for quantitative analysis. The stabilized calibration solutions were used for quantitative headspace solid-phase microextraction/gas chromatography–mass spectrometry (HS-SPME/GC–MS) determination of acrolein in alcoholic beverages with a detection limit of 14 μg L −1 . Of 117 tested alcoholic beverages, 64 were tested positive with the highest incidence in grape marc spirits and whiskey (100%, mean 252 μg L −1 ), followed by fruit spirits (86%, mean 591 μg/L −1 ), tequila (86%, mean 404 μg L −1 ), Asian spirits (43%, mean 54 μg L −1 ) and wine (9%, mean 0.7 μg L −1 ). Acrolein could not be detected in beer, vodka, absinthe and bottled water. Six of the fruit and grape marc spirits had acrolein levels above the World Health Organization (WHO) provisional tolerable concentration of 1.5 mg L −1

  6. NMR investigation of acrolein stability in hydroalcoholic solution as a foundation for the valid HS-SPME/GC–MS quantification of the unsaturated aldehyde in beverages

    Energy Technology Data Exchange (ETDEWEB)

    Kächele, Martin [Chemisches und Veterinäruntersuchungsamt (CVUA) Karlsruhe, Weissenburger Strasse 3, D-76187 Karlsruhe (Germany); Hochschule Mannheim, Paul-Wittsack-Strasse 10, D-68163 Mannheim (Germany); Monakhova, Yulia B. [Chemisches und Veterinäruntersuchungsamt (CVUA) Karlsruhe, Weissenburger Strasse 3, D-76187 Karlsruhe (Germany); Bruker Biospin GmbH, Silbersteifen, 76287 Rheinstetten (Germany); Department of Chemistry, Saratov State University, Astrakhanskaya Street 83, 410012 Saratov (Russian Federation); Kuballa, Thomas [Chemisches und Veterinäruntersuchungsamt (CVUA) Karlsruhe, Weissenburger Strasse 3, D-76187 Karlsruhe (Germany); Lachenmeier, Dirk W., E-mail: lachenmeier@web.de [Chemisches und Veterinäruntersuchungsamt (CVUA) Karlsruhe, Weissenburger Strasse 3, D-76187 Karlsruhe (Germany); Ministry of Rural Affairs and Consumer Protection, Kernerplatz 10, 70182 Stuttgart (Germany)

    2014-04-01

    Highlights: • Acrolein in hydroalcoholic solution degrades to 1,3,3-propanetriol and 3-hydroxypropionaldehyde. • Hydroquinone (0.2%) at pH 3.0 stabilizes acrolein solutions. • Quantitative HS-SPME/GC–MS determination of acrolein in alcoholic beverages was developed (LOD 14 μg L⁻¹. • 6 of 117 samples had acrolein levels above the WHO threshold (1500 μg L⁻¹). Abstract: Acrolein (propenal) is found in many foods and beverages and may pose a health hazard due to its cytotoxicity. Considerable knowledge gaps regarding human exposure to acrolein exist, and there is a lack of reliable analytical methods. Hydroalcoholic dilutions prepared for calibration purposes from pure acrolein show considerable degradation of the compound and nuclear magnetic resonance (NMR) spectroscopy showed that 1,3,3-propanetriol and 3-hydroxypropionaldehyde are formed. The degradation can be prevented by addition of hydroquinone as stabilizer to the calibration solutions, which then show linear concentration-response behaviour required for quantitative analysis. The stabilized calibration solutions were used for quantitative headspace solid-phase microextraction/gas chromatography–mass spectrometry (HS-SPME/GC–MS) determination of acrolein in alcoholic beverages with a detection limit of 14 μg L⁻¹. Of 117 tested alcoholic beverages, 64 were tested positive with the highest incidence in grape marc spirits and whiskey (100%, mean 252 μg L⁻¹), followed by fruit spirits (86%, mean 591 μg/L⁻¹), tequila (86%, mean 404 μg L⁻¹), Asian spirits (43%, mean 54 μg L⁻¹) and wine (9%, mean 0.7 μg L⁻¹). Acrolein could not be detected in beer, vodka, absinthe and bottled water. Six of the fruit and grape marc spirits had acrolein levels above the World Health Organization (WHO) provisional tolerable concentration of 1.5 mg L⁻¹.

  7. Soliton robustness in optical fibers

    International Nuclear Information System (INIS)

    Menyuk, C.R.

    1993-01-01

    Simulations and experiments indicate that solitons in optical fibers are robust in the presence of Hamiltonian deformations such as higher-order dispersion and birefringence but are destroyed in the presence of non-Hamiltonian deformations such as attenuation and the Raman effect. Two hypotheses are introduced that generalize these observations and give a recipe for when deformations will be Hamiltonian. Concepts from nonlinear dynamics are used to make these two hypotheses plausible. Soliton stabilization with frequency filtering is also briefly discussed from this point of view

  8. Robust and Sparse Factor Modelling

    DEFF Research Database (Denmark)

    Croux, Christophe; Exterkate, Peter

    Factor construction methods are widely used to summarize a large panel of variables by means of a relatively small number of representative factors. We propose a novel factor construction procedure that enjoys the properties of robustness to outliers and of sparsity; that is, having relatively few...... nonzero factor loadings. Compared to the traditional factor construction method, we find that this procedure leads to a favorable forecasting performance in the presence of outliers and to better interpretable factors. We investigate the performance of the method in a Monte Carlo experiment...

  9. Robustness Evaluation of Timber Structures

    DEFF Research Database (Denmark)

    Kirkegaard, Poul Henning; Sørensen, John Dalsgaard; čizmar, D.

    2010-01-01

    The present paper outlines results from working group 3 (WG3) in the EU COST Action E55 – ‘Modelling of the performance of timber structures’. The objectives of the project are related to the three main research activities: the identification and modelling of relevant load and environmental...... exposure scenarios, the improvement of knowledge concerning the behaviour of timber structural elements and the development of a generic framework for the assessment of the life-cycle vulnerability and robustness of timber structures....

  10. Sustainable Resilient, Robust & Resplendent Enterprises

    DEFF Research Database (Denmark)

    Edgeman, Rick

    to their impact. Resplendent enterprises are introduced with resplendence referring not to some sort of public or private façade, but instead refers to organizations marked by dual brilliance and nobility of strategy, governance and comportment that yields superior and sustainable triple bottom line performance....... Herein resilience, robustness, and resplendence (R3) are integrated with sustainable enterprise excellence (Edgeman and Eskildsen, 2013) or SEE and social-ecological innovation (Eskildsen and Edgeman, 2012) to aid progress of a firm toward producing continuously relevant performance that proceed from...

  11. Robust Instrumentation[Water treatment for power plant]; Robust Instrumentering

    Energy Technology Data Exchange (ETDEWEB)

    Wik, Anders [Vattenfall Utveckling AB, Stockholm (Sweden)

    2003-08-01

    Cementa Slite Power Station is a heat recovery steam generator (HRSG) with moderate steam data; 3.0 MPa and 420 deg C. The heat is recovered from Cementa, a cement industry, without any usage of auxiliary fuel. The Power station commenced operation in 2001. The layout of the plant is unusual, there are no similar in Sweden and very few world-wide, so the operational experiences are limited. In connection with the commissioning of the power plant a R and D project was identified with the objective to minimise the manpower needed for chemistry management of the plant. The lean chemistry management is based on robust instrumentation and chemical-free water treatment plant. The concept with robust instrumentation consists of the following components; choice of on-line instrumentation with a minimum of O and M and a chemical-free water treatment. The parameters are specific conductivity, cation conductivity, oxygen and pH. In addition to that, two fairly new on-line instruments were included; corrosion monitors and differential pH calculated from specific and cation conductivity. The chemical-free water treatment plant consists of softening, reverse osmosis and electro-deionisation. The operational experience shows that the cycle chemistry is not within the guidelines due to major problems with the operation of the power plant. These problems have made it impossible to reach steady state and thereby not viable to fully verify and validate the concept with robust instrumentation. From readings on the panel of the online analysers some conclusions may be drawn, e.g. the differential pH measurements have fulfilled the expectations. The other on-line analysers have been working satisfactorily apart from contamination with turbine oil, which has been noticed at least twice. The corrosion monitors seem to be working but the lack of trend curves from the mainframe computer system makes it hard to draw any clear conclusions. The chemical-free water treatment has met all

  12. Perspective: Evolution and detection of genetic robustness

    NARCIS (Netherlands)

    Visser, de J.A.G.M.; Hermisson, J.; Wagner, G.P.; Ancel Meyers, L.; Bagheri-Chaichian, H.; Blanchard, J.L.; Chao, L.; Cheverud, J.M.; Elena, S.F.; Fontana, W.; Gibson, G.; Hansen, T.F.; Krakauer, D.; Lewontin, R.C.; Ofria, C.; Rice, S.H.; Dassow, von G.; Wagner, A.; Whitlock, M.C.

    2003-01-01

    Robustness is the invariance of phenotypes in the face of perturbation. The robustness of phenotypes appears at various levels of biological organization, including gene expression, protein folding, metabolic flux, physiological homeostasis, development, and even organismal fitness. The mechanisms

  13. Robust lyapunov controller for uncertain systems

    KAUST Repository

    Laleg-Kirati, Taous-Meriem; Elmetennani, Shahrazed

    2017-01-01

    Various examples of systems and methods are provided for Lyapunov control for uncertain systems. In one example, a system includes a process plant and a robust Lyapunov controller configured to control an input of the process plant. The robust

  14. Robust distributed cognitive relay beamforming

    KAUST Repository

    Pandarakkottilil, Ubaidulla

    2012-05-01

    In this paper, we present a distributed relay beamformer design for a cognitive radio network in which a cognitive (or secondary) transmit node communicates with a secondary receive node assisted by a set of cognitive non-regenerative relays. The secondary nodes share the spectrum with a licensed primary user (PU) node, and each node is assumed to be equipped with a single transmit/receive antenna. The interference to the PU resulting from the transmission from the cognitive nodes is kept below a specified limit. The proposed robust cognitive relay beamformer design seeks to minimize the total relay transmit power while ensuring that the transceiver signal-to-interference- plus-noise ratio and PU interference constraints are satisfied. The proposed design takes into account a parameter of the error in the channel state information (CSI) to render the performance of the beamformer robust in the presence of imperfect CSI. Though the original problem is non-convex, we show that the proposed design can be reformulated as a tractable convex optimization problem that can be solved efficiently. Numerical results are provided and illustrate the performance of the proposed designs for different network operating conditions and parameters. © 2012 IEEE.

  15. Robust canonical correlations: A comparative study

    OpenAIRE

    Branco, JA; Croux, Christophe; Filzmoser, P; Oliveira, MR

    2005-01-01

    Several approaches for robust canonical correlation analysis will be presented and discussed. A first method is based on the definition of canonical correlation analysis as looking for linear combinations of two sets of variables having maximal (robust) correlation. A second method is based on alternating robust regressions. These methods axe discussed in detail and compared with the more traditional approach to robust canonical correlation via covariance matrix estimates. A simulation study ...

  16. Robust adaptive synchronization of general dynamical networks ...

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 86; Issue 6. Robust ... A robust adaptive synchronization scheme for these general complex networks with multiple delays and uncertainties is established and raised by employing the robust adaptive control principle and the Lyapunov stability theory. We choose ...

  17. Robust portfolio selection under norm uncertainty

    Directory of Open Access Journals (Sweden)

    Lei Wang

    2016-06-01

    Full Text Available Abstract In this paper, we consider the robust portfolio selection problem which has a data uncertainty described by the ( p , w $(p,w$ -norm in the objective function. We show that the robust formulation of this problem is equivalent to a linear optimization problem. Moreover, we present some numerical results concerning our robust portfolio selection problem.

  18. A robust standard deviation control chart

    NARCIS (Netherlands)

    Schoonhoven, M.; Does, R.J.M.M.

    2012-01-01

    This article studies the robustness of Phase I estimators for the standard deviation control chart. A Phase I estimator should be efficient in the absence of contaminations and resistant to disturbances. Most of the robust estimators proposed in the literature are robust against either diffuse

  19. Methodology in robust and nonparametric statistics

    CERN Document Server

    Jurecková, Jana; Picek, Jan

    2012-01-01

    Introduction and SynopsisIntroductionSynopsisPreliminariesIntroductionInference in Linear ModelsRobustness ConceptsRobust and Minimax Estimation of LocationClippings from Probability and Asymptotic TheoryProblemsRobust Estimation of Location and RegressionIntroductionM-EstimatorsL-EstimatorsR-EstimatorsMinimum Distance and Pitman EstimatorsDifferentiable Statistical FunctionsProblemsAsymptotic Representations for L-Estimators

  20. Container Materials, Fabrication And Robustness

    International Nuclear Information System (INIS)

    Dunn, K.; Louthan, M.; Rawls, G.; Sindelar, R.; Zapp, P.; Mcclard, J.

    2009-01-01

    The multi-barrier 3013 container used to package plutonium-bearing materials is robust and thereby highly resistant to identified degradation modes that might cause failure. The only viable degradation mechanisms identified by a panel of technical experts were pressurization within and corrosion of the containers. Evaluations of the container materials and the fabrication processes and resulting residual stresses suggest that the multi-layered containers will mitigate the potential for degradation of the outer container and prevent the release of the container contents to the environment. Additionally, the ongoing surveillance programs and laboratory studies should detect any incipient degradation of containers in the 3013 storage inventory before an outer container is compromised.

  1. Robust matching for voice recognition

    Science.gov (United States)

    Higgins, Alan; Bahler, L.; Porter, J.; Blais, P.

    1994-10-01

    This paper describes an automated method of comparing a voice sample of an unknown individual with samples from known speakers in order to establish or verify the individual's identity. The method is based on a statistical pattern matching approach that employs a simple training procedure, requires no human intervention (transcription, work or phonetic marketing, etc.), and makes no assumptions regarding the expected form of the statistical distributions of the observations. The content of the speech material (vocabulary, grammar, etc.) is not assumed to be constrained in any way. An algorithm is described which incorporates frame pruning and channel equalization processes designed to achieve robust performance with reasonable computational resources. An experimental implementation demonstrating the feasibility of the concept is described.

  2. Robustness Assessment of Spatial Timber Structures

    DEFF Research Database (Denmark)

    Kirkegaard, Poul Henning

    2012-01-01

    Robustness of structural systems has obtained a renewed interest due to a much more frequent use of advanced types of structures with limited redundancy and serious consequences in case of failure. In order to minimise the likelihood of such disproportionate structural failures many modern buildi...... to robustness of spatial timber structures and will discuss the consequences of such robustness issues related to the future development of timber structures.......Robustness of structural systems has obtained a renewed interest due to a much more frequent use of advanced types of structures with limited redundancy and serious consequences in case of failure. In order to minimise the likelihood of such disproportionate structural failures many modern building...... codes consider the need for robustness of structures and provide strategies and methods to obtain robustness. Therefore a structural engineer may take necessary steps to design robust structures that are insensitive to accidental circumstances. The present paper summaries issues with respect...

  3. Simultaneous analysis of organochlorine pesticides and polychlorinated biphenyls in air samples by using accelerated solvent extraction (ASE) and solid-phase micro-extraction (SPME) coupled to gas chromatography dual electron capture detection.

    Science.gov (United States)

    Mokbel, Haifaa; Al Dine, Enaam Jamal; Elmoll, Ahmad; Liaud, Céline; Millet, Maurice

    2016-04-01

    An analytical method associating accelerated solvent extraction (ASE) and solid-phase micro-extraction (SPME) in immersion mode combined with gas chromatography dual electrons capture detectors (SPME-GC-2ECD) has been developed and studied for the simultaneous determination of 19 organochlorine pesticides (OCPs) and 22 polychlorinated biphenyls (PCBs) in air samples (active and XAD-2 passive samplers). Samples were extracted with ASE with acetonitrile using the following conditions: temperature, 150 °C; pressure, 1500 psi; static, 15 min; cycles, 3; purge, 300 s; flush, 100 %. Extracts were reduced to 1 mL, and 500 μL of this extract, filled with deionised water, was subject to SPME extraction. Experimental results indicated that the proposed method attained the best extraction efficiency under the optimised conditions: extraction of PCB-OCP mixture using 100-μm PDMS fibre at 80 °C for 40 min with no addition of salt. The performance of the proposed ASE-SPME-GC-2ECD methodology with respect to linearity, limit of quantification and detection was evaluated by spiking of XAD-2 resin with target compounds. The regression coefficient (R (2)) of most compounds was found to be high of 0.99. limits of detection (LODs) are between 0.02 and 4.90 ng m(-3), and limits of quantification (LOQs) are between 0.05 and 9.12 ng m(-3) and between 0.2 and 49 ng/sampler and 0.52 and 91 ng/sampler, respectively, for XAD-2 passive samplers. Finally, a developed procedure was applied to determine selected PCBs and OCPs in the atmosphere.

  4. Determination of infinite dilution activity coefficients using HS-SPME/GC/FID for hydrocarbons in furfural at temperatures of (298.15, 308.15, and 318.15) K

    International Nuclear Information System (INIS)

    Arantes Furtado, Filipe; Vieira Coelho, Gerson Luiz

    2012-01-01

    Highlights: ► Two approaches were proposed using SPME on determination of infinite dilution activity coefficients. ► Infinite dilution activity coefficients of nine solutes in solvent furfural at T = (298.15, 308.15, and 318.15) K. ► Fiber–gas partition coefficients of nine solutes on PDMS at T = (298.15, 308.15, and 318.15) K. ► Optical microscopy analysis and statistical tests to measure possible damages on fiber coating. ► Advantages and limitations of methodology proposed were discussed. - Abstract: A new methodology using the headspace solid phase microextraction (HS-SPME) technique has been used to evaluate the infinite dilution activity coefficient (γ 12 ∞ ) of nine hydrocarbons (alkanes, cycloalkanes, and aromatics) in furfural solvent. The main objective of this study was to validate a faster and lower cost methodology expanding the use of HS-SPME to determine infinite dilution activity of solutes in organic solvents. Two approaches were proposed for the determination of γ 12 ∞ in order to use this technique (HS-SPME). In addition, the fiber–gas partition coefficients (K fg ) for each analyte at each of the studied temperatures were determined. The activity and partition coefficients have been reported at temperatures of (298.15, 308.15, and 318.15) K. The data were compared with the literature infinite dilution data determined by other methods such as liquid–gas chromatography (GLC) and gas stripping. Partial molar excess enthalpies of mixing at infinite dilution for each solute have been determined. The fibers were tested before and after each experiment, using statistical methods to ensure that their properties do not change during the experiments. The fibers were also analyzed by optical microscopy to evaluate possible surface damage by comparing them with new fibers. The activity coefficient values correlated well with the data in the literature and showed average deviations less than 10%.

  5. A high area, porous and resistant platinized stainless steel fiber coated by nanostructured polypyrrole for direct HS-SPME of nicotine in biological samples prior to GC-FID quantification.

    Science.gov (United States)

    Abdolhosseini, Sana; Ghiasvand, Alireza; Heidari, Nahid

    2017-09-01

    The surface of a stainless steel fiber was made porous, resistant and cohesive using electrophoretic deposition and coated by the nanostructured polypyrrole using an amended in-situ electropolymerization method. The coated fiber was applied for direct extraction of nicotine in biological samples through a headspace solid-phase microextraction (HS-SPME) method followed by GC-FID determination. The effects of the important experimental variables on the efficiency of the developed HS-SPME-GC-FID method, including pH of sample solution, extraction temperature and time, stirring rate, and ionic strength were evaluated and optimized. Under the optimal experimental conditions, the calibration curve was linear over the range of 0.1-20μgmL -1 and the detection limit was obtained 20ngmL -1 . Relative standard deviation (RSD, n=6) was calculated 7.6%. The results demonstrated the superiority of the proposed fiber compared with the most used commercial types. The proposed HS-SPME-GC-FID method was successfully used for the analysis of nicotine in urine and human plasma samples. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Robust holographic storage system design.

    Science.gov (United States)

    Watanabe, Takahiro; Watanabe, Minoru

    2011-11-21

    Demand is increasing daily for large data storage systems that are useful for applications in spacecraft, space satellites, and space robots, which are all exposed to radiation-rich space environment. As candidates for use in space embedded systems, holographic storage systems are promising because they can easily provided the demanded large-storage capability. Particularly, holographic storage systems, which have no rotation mechanism, are demanded because they are virtually maintenance-free. Although a holographic memory itself is an extremely robust device even in a space radiation environment, its associated lasers and drive circuit devices are vulnerable. Such vulnerabilities sometimes engendered severe problems that prevent reading of all contents of the holographic memory, which is a turn-off failure mode of a laser array. This paper therefore presents a proposal for a recovery method for the turn-off failure mode of a laser array on a holographic storage system, and describes results of an experimental demonstration. © 2011 Optical Society of America

  7. Efficient robust conditional random fields.

    Science.gov (United States)

    Song, Dongjin; Liu, Wei; Zhou, Tianyi; Tao, Dacheng; Meyer, David A

    2015-10-01

    Conditional random fields (CRFs) are a flexible yet powerful probabilistic approach and have shown advantages for popular applications in various areas, including text analysis, bioinformatics, and computer vision. Traditional CRF models, however, are incapable of selecting relevant features as well as suppressing noise from noisy original features. Moreover, conventional optimization methods often converge slowly in solving the training procedure of CRFs, and will degrade significantly for tasks with a large number of samples and features. In this paper, we propose robust CRFs (RCRFs) to simultaneously select relevant features. An optimal gradient method (OGM) is further designed to train RCRFs efficiently. Specifically, the proposed RCRFs employ the l1 norm of the model parameters to regularize the objective used by traditional CRFs, therefore enabling discovery of the relevant unary features and pairwise features of CRFs. In each iteration of OGM, the gradient direction is determined jointly by the current gradient together with the historical gradients, and the Lipschitz constant is leveraged to specify the proper step size. We show that an OGM can tackle the RCRF model training very efficiently, achieving the optimal convergence rate [Formula: see text] (where k is the number of iterations). This convergence rate is theoretically superior to the convergence rate O(1/k) of previous first-order optimization methods. Extensive experiments performed on three practical image segmentation tasks demonstrate the efficacy of OGM in training our proposed RCRFs.

  8. Robust boosting via convex optimization

    Science.gov (United States)

    Rätsch, Gunnar

    2001-12-01

    In this work we consider statistical learning problems. A learning machine aims to extract information from a set of training examples such that it is able to predict the associated label on unseen examples. We consider the case where the resulting classification or regression rule is a combination of simple rules - also called base hypotheses. The so-called boosting algorithms iteratively find a weighted linear combination of base hypotheses that predict well on unseen data. We address the following issues: o The statistical learning theory framework for analyzing boosting methods. We study learning theoretic guarantees on the prediction performance on unseen examples. Recently, large margin classification techniques emerged as a practical result of the theory of generalization, in particular Boosting and Support Vector Machines. A large margin implies a good generalization performance. Hence, we analyze how large the margins in boosting are and find an improved algorithm that is able to generate the maximum margin solution. o How can boosting methods be related to mathematical optimization techniques? To analyze the properties of the resulting classification or regression rule, it is of high importance to understand whether and under which conditions boosting converges. We show that boosting can be used to solve large scale constrained optimization problems, whose solutions are well characterizable. To show this, we relate boosting methods to methods known from mathematical optimization, and derive convergence guarantees for a quite general family of boosting algorithms. o How to make Boosting noise robust? One of the problems of current boosting techniques is that they are sensitive to noise in the training sample. In order to make boosting robust, we transfer the soft margin idea from support vector learning to boosting. We develop theoretically motivated regularized algorithms that exhibit a high noise robustness. o How to adapt boosting to regression problems

  9. Development of a HS-SPME-GC/MS protocol assisted by chemometric tools to study herbivore-induced volatiles in Myrcia splendens.

    Science.gov (United States)

    Souza Silva, Érica A; Saboia, Giovanni; Jorge, Nina C; Hoffmann, Camila; Dos Santos Isaias, Rosy Mary; Soares, Geraldo L G; Zini, Claudia A

    2017-12-01

    A headspace solid phase microextraction (HS-SPME) method combined with gas chromatography-mass spectrometry (GC/MS) was developed and optimized for extraction and analysis of volatile organic compounds (VOC) of leaves and galls of Myrcia splendens. Through a process of optimization of main factors affecting HS-SPME efficiency, the coating divivnilbenzene-carboxen-polydimethylsiloxane (DVB/Car/PDMS) was chosen as the optimum extraction phase, not only in terms of extraction efficiency, but also for its broader analyte coverage. Optimum extraction temperature was 30°C, while an extraction time of 15min provided the best compromise between extraction efficiencies of lower and higher molecular weight compounds. The optimized protocol was demonstrated to be capable of sampling plant material with high reproducibility, considering that most classes of analytes met the 20% RSD FDA criterion. The optimized method was employed for the analysis of three classes of M. splendens samples, generating a final list of 65 tentatively identified VOC, including alcohols, aldehydes, esters, ketones, phenol derivatives, as well as mono and sesquiterpenes. Significant differences were evident amongst the volatile profiles obtained from non-galled leaves (NGL) and leaf-folding galls (LFG) of M. splendens. Several differences pertaining to amounts of alcohols and aldehydes were detected between samples, particularly regarding quantities of green leaf volatiles (GLV). Alcohols represented about 14% of compounds detected in gall samples, whereas in non-galled samples, alcohol content was below 5%. Phenolic derived compounds were virtually absent in reference samples, while in non-galled leaves and galls their content ranged around 0.2% and 0.4%, respectively. Likewise, methyl salicylate, a well-known signal of plant distress, amounted for 1.2% of the sample content of galls, whereas it was only present in trace levels in reference samples. Chemometric analysis based on Heatmap associated

  10. Discrimination of cherry wines based on their sensory properties and aromatic fingerprinting using HS-SPME-GC-MS and multivariate analysis.

    Science.gov (United States)

    Xiao, Zuobing; Liu, Shengjiang; Gu, Yongbo; Xu, Na; Shang, Yi; Zhu, Jiancai

    2014-03-01

    Volatiles of cherry wines were extracted by headspace solid phase microextraction (HS-SPME) and analyzed by gas chromatography mass spectrometry (GC-MS), multivariate statistical techniques (such as principal component analysis (PCA) and cluster analysis (CA) and correlation analysis) to differentiate sensory attributes of 3 groups of the wines through characterization of volatiles of cherry wine. Seventy-five volatiles were identified in 9 samples, including 29 esters, 22 alcohols, 8 acids, 3 ketones, 5 aldehydes, and 8 miscellaneous compounds. The PCA results showed that the cherry wines were mainly differentiated by 8 sensory attributes. The samples W2, W4, and W7 were grouped around sweet aromatic and the samples W1, W5, and W9 were highly associated with the sweet, esters, green, bitter, and fermented. Nevertheless, the samples W3, W6, and W8 were located close to the sour, alcoholic, and fruity. The final result of correlation analysis was in conformity with the conclusion of PCA. The CA results showed that the group of W2, W4, and W7, and the group of W1, W5, and W9 had less difference than the group of W3, W6, and W8. The reason should be that esterification reactions and fermentation process during the ageing period was more extended. The results of analyzing revealed that HS-SPME-GC-MS coupled with chemometrics could give an appropriate way of characterizing and classifying the cherry wines. Attributes that represent and discriminate among cherry wines might be made use of a better comprehending of the wines and for being utilized in future work. In addition, several chemometrics were used to classify the type of wines and try to install the relationship between volatiles and sensory property. Especially, PCA clearly revealed that the most contributing compounds for sensory attributes of cherry wines, CA was a more applicable way to distinguish types of cherry wines. Therefore, a feasible method that would be helpful to promote the quality of the wines by

  11. Robust AIC with High Breakdown Scale Estimate

    Directory of Open Access Journals (Sweden)

    Shokrya Saleh

    2014-01-01

    Full Text Available Akaike Information Criterion (AIC based on least squares (LS regression minimizes the sum of the squared residuals; LS is sensitive to outlier observations. Alternative criterion, which is less sensitive to outlying observation, has been proposed; examples are robust AIC (RAIC, robust Mallows Cp (RCp, and robust Bayesian information criterion (RBIC. In this paper, we propose a robust AIC by replacing the scale estimate with a high breakdown point estimate of scale. The robustness of the proposed methods is studied through its influence function. We show that, the proposed robust AIC is effective in selecting accurate models in the presence of outliers and high leverage points, through simulated and real data examples.

  12. Multimodel Robust Control for Hydraulic Turbine

    OpenAIRE

    Osuský, Jakub; Števo, Stanislav

    2014-01-01

    The paper deals with the multimodel and robust control system design and their combination based on M-Δ structure. Controller design will be done in the frequency domain with nominal performance specified by phase margin. Hydraulic turbine model is analyzed as system with unstructured uncertainty, and robust stability condition is included in controller design. Multimodel and robust control approaches are presented in detail on hydraulic turbine model. Control design approaches are compared a...

  13. Forecasting exchange rates: a robust regression approach

    OpenAIRE

    Preminger, Arie; Franck, Raphael

    2005-01-01

    The least squares estimation method as well as other ordinary estimation method for regression models can be severely affected by a small number of outliers, thus providing poor out-of-sample forecasts. This paper suggests a robust regression approach, based on the S-estimation method, to construct forecasting models that are less sensitive to data contamination by outliers. A robust linear autoregressive (RAR) and a robust neural network (RNN) models are estimated to study the predictabil...

  14. Robustness: confronting lessons from physics and biology.

    Science.gov (United States)

    Lesne, Annick

    2008-11-01

    The term robustness is encountered in very different scientific fields, from engineering and control theory to dynamical systems to biology. The main question addressed herein is whether the notion of robustness and its correlates (stability, resilience, self-organisation) developed in physics are relevant to biology, or whether specific extensions and novel frameworks are required to account for the robustness properties of living systems. To clarify this issue, the different meanings covered by this unique term are discussed; it is argued that they crucially depend on the kind of perturbations that a robust system should by definition withstand. Possible mechanisms underlying robust behaviours are examined, either encountered in all natural systems (symmetries, conservation laws, dynamic stability) or specific to biological systems (feedbacks and regulatory networks). Special attention is devoted to the (sometimes counterintuitive) interrelations between robustness and noise. A distinction between dynamic selection and natural selection in the establishment of a robust behaviour is underlined. It is finally argued that nested notions of robustness, relevant to different time scales and different levels of organisation, allow one to reconcile the seemingly contradictory requirements for robustness and adaptability in living systems.

  15. Robustness of Long Span Reciprocal Timber Structures

    DEFF Research Database (Denmark)

    Balfroid, Nathalie; Kirkegaard, Poul Henning

    2011-01-01

    engineer may take necessary steps to design robust structures that are insensitive to accidental circumstances. The present paper makes a discussion of such robustness issues related to the future development of reciprocal timber structures. The paper concludes that these kind of structures can have...... a potential as long span timber structures in real projects if they are carefully designed with respect to the overall robustness strategies.......Robustness of structural systems has obtained a renewed interest due to a much more frequent use of advanced types of structures with limited redundancy and serious consequences in case of failure. The interest has also been facilitated due to recently severe structural failures...

  16. Determinação de herbicidas usados no cultivo de arroz irrigado na região sul do estado de Santa Catarina através da SPME-GC-ECD Determination of herbicides used in irrigated rice cultivation in the south of Santa Catarina using SPME-GC-ECD

    Directory of Open Access Journals (Sweden)

    Léa L. F. Costa

    2008-01-01

    Full Text Available Evaluation of the pollution by the herbicides alachlor, propanil and atrazine in water samples from four rivers in the cities of Turvo and Meleiro, south of Santa Catarina State, was made using the SPME-GC-ECD method. The proposed method was optimized and validated. The correlation coefficients were higher than 0.997 and linear ranges of the analytical curves were 0.1-4; 0.1-2.5 and 0.1-5 µg L-1 for atrazine, alachlor and propanil, respectively. The herbicides were quantified by GC-ECD and identified by GC-MS. Both of the selected rivers presented contamination by at least one of the studied herbicides.

  17. Stable isotope dilution assay (SIDA) and HS-SPME-GCMS quantification of key aroma volatiles for fruit and sap of Australian mango cultivars.

    Science.gov (United States)

    San, Anh T; Joyce, Daryl C; Hofman, Peter J; Macnish, Andrew J; Webb, Richard I; Matovic, Nicolas J; Williams, Craig M; De Voss, James J; Wong, Siew H; Smyth, Heather E

    2017-04-15

    Reported herein is a high throughput method to quantify in a single analysis the key volatiles that contribute to the aroma of commercially significant mango cultivars grown in Australia. The method constitutes stable isotope dilution analysis (SIDA) in conjunction with headspace (HS) solid-phase microextraction (SPME) coupled with gas-chromatography mass spectrometry (GCMS). Deuterium labelled analogues of the target analytes were either purchased commercially or synthesised for use as internal standards. Seven volatiles, hexanal, 3-carene, α-terpinene, p-cymene, limonene, α-terpinolene and ethyl octanoate, were targeted. The resulting calibration functions had determination coefficients (R 2 ) ranging from 0.93775 to 0.99741. High recovery efficiencies for spiked mango samples were also achieved. The method was applied to identify the key aroma volatile compounds produced by 'Kensington Pride' and 'B74' mango fruit and by 'Honey Gold' mango sap. This method represents a marked improvement over current methods for detecting and measuring concentrations of mango fruit and sap volatiles. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Rapid evaluation technique to differentiate mushroom disease-related moulds by detecting microbial volatile organic compounds using HS-SPME-GC-MS.

    Science.gov (United States)

    Radványi, Dalma; Gere, Attila; Jókai, Zsuzsa; Fodor, Péter

    2015-01-01

    Headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was used to analyse microbial volatile organic compounds (MVOCs) of mushroom disease-related microorganisms. Mycogone perniciosa, Lecanicillum fungicola var. fungicola, and Trichoderma aggressivum f. europaeum species, which are typically harmful in mushroom cultivation, were examined, and Agaricus bisporus (bisporic button mushroom) was also examined as a control. For internal standard, a mixture of alkanes was used; these were introduced as the memory effect of primed septa in the vial seal. Several different marker compounds were found in each sample, which enabled us to distinguish the different moulds and the mushroom mycelium from each other. Monitoring of marker compounds enabled us to investigate the behaviour of moulds. The records of the temporal pattern changes were used to produce partial least squares regression (PLS-R) models that enabled determination of the exact time of contamination (the infection time of the media). Using these evaluation techniques, the presence of mushroom disease-related fungi can be easily detected and monitored via their emitted MVOCs.

  19. Impact of Microbial Composition of Cambodian Traditional Dried Starters (Dombea on Flavor Compounds of Rice Wine: Combining Amplicon Sequencing With HP-SPME-GCMS

    Directory of Open Access Journals (Sweden)

    Sokny Ly

    2018-05-01

    Full Text Available Dombae is a traditional ferment starter which has been used for starchy based wine production in Cambodia. However, the production technology of rice wine in Cambodia is not optimized. The current study aimed to investigate the microbiota associated in five ferment starters and the effect of a traditional fermentation process using a metagenomics sequencing analysis and HS-SPME-GCMS for the characterization of the aromatic profiles at the end of fermentation. Most of bacteria identified in this study were lactic acid bacteria including Weissella cibaria, Pediococcus sp. MMZ60A, Lactobacillus fermentum, and Lactobacillus plantarum. Saccharomyces cerevisiae and Saccharomycopsis fibuligera were found to be abundant yeasts while the only amylolytic filamentous fungus was Rhizopus oryzae. A total of 25 aromatic compounds were detected and identified as esters, alcohols, acids, ketones and aldehydes. The alcohol group was dominant in each rice wine. Significant changes were observed at the level of microbial communities during fermentation, suggesting microbial succession for the assimilation of starch and subsequently assimilation of fermentation by-products leading to the production of flavor compounds. At this level, the presence of Weissella, Pediococcus, and Lactobacillus genus was strongly correlated with most of the flavor compounds detected.

  20. Impact of Microbial Composition of Cambodian Traditional Dried Starters (Dombea) on Flavor Compounds of Rice Wine: Combining Amplicon Sequencing With HP-SPME-GCMS

    Science.gov (United States)

    Ly, Sokny; Mith, Hasika; Tarayre, Cédric; Taminiau, Bernard; Daube, Georges; Fauconnier, Marie-Laure; Delvigne, Frank

    2018-01-01

    Dombae is a traditional ferment starter which has been used for starchy based wine production in Cambodia. However, the production technology of rice wine in Cambodia is not optimized. The current study aimed to investigate the microbiota associated in five ferment starters and the effect of a traditional fermentation process using a metagenomics sequencing analysis and HS-SPME-GCMS for the characterization of the aromatic profiles at the end of fermentation. Most of bacteria identified in this study were lactic acid bacteria including Weissella cibaria, Pediococcus sp. MMZ60A, Lactobacillus fermentum, and Lactobacillus plantarum. Saccharomyces cerevisiae and Saccharomycopsis fibuligera were found to be abundant yeasts while the only amylolytic filamentous fungus was Rhizopus oryzae. A total of 25 aromatic compounds were detected and identified as esters, alcohols, acids, ketones and aldehydes. The alcohol group was dominant in each rice wine. Significant changes were observed at the level of microbial communities during fermentation, suggesting microbial succession for the assimilation of starch and subsequently assimilation of fermentation by-products leading to the production of flavor compounds. At this level, the presence of Weissella, Pediococcus, and Lactobacillus genus was strongly correlated with most of the flavor compounds detected. PMID:29867806

  1. Effect of water content on thermal oxidation of oleic acid investigated by combination of EPR spectroscopy and SPME-GC-MS/MS.

    Science.gov (United States)

    Chen, Hongjian; Cao, Peirang; Li, Bo; Sun, Dewei; Wang, Yong; Li, Jinwei; Liu, Yuanfa

    2017-04-15

    Promotion of water to the thermal oxidation of oleic acid was detected by the combination of EPR, SPME-GC-MS/MS and GC. Spin-trapping technique was used to identify and quantify the radical species formed during thermal oxidation of oleic acid by using DMPO as electron spin trap. The most abundant radical species were identified as DMPO-alkyl radical adducts. EPR intensity plateau of the samples with 5% water content was 140% higher than the samples without water. It implies oleic acid samples with high water content had high level of oxidation rates. The proportion of aldehydes of the samples with 2% water content was the maximum about 59.97%. Among the formed products, (E,E)-2,4-decadienal has genotoxic and cytotoxic effects, whose percentage was nearly twice comparing with that of 5-0% water content. This study demonstrated that higher water content in frying systems would contribute to seriously oxidation and degradation of oleic acids. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Chemical composition analysis of the essential oil of Solanumn nigrum L. by HS/SPME method and calculation of the biochemical coefficients of the components

    Directory of Open Access Journals (Sweden)

    Avat (Arman Taherpour

    2017-05-01

    Full Text Available The volatile constituents of the essential oil of wild Solanumn nigrum L. obtained from the Kurdistan of Iraq were extracted by head-space/solid-phase micro-extraction (HS/SPME and were analyzed by gas chromatography (GC and gas chromatography/mass spectrometry (GC/MS. Of a total of twenty compounds in the oil, all of them were identified. The main components were as follows: Dillapiole (22.22%, α-Cadinol (16.47%, para-Cymene (10.01%, (E-1-(2,6,6-Trimethyl-1,3-cyclohexadien-1-yl-2-buten-1-one or β-damascenone (9.08%, α-Phellandrene (8.48%, β-Pinene (5.93%, α-Bisabolol acetate (4.53%, (Z,E-4,6,8-Megastigmatriene (4.09%, Phytol (2.49%, Linalyl butanoate (2.13%, 8-methylene-tricyclo[3.2.1.0(2,4]octane (2.60% and Limonene (2.03%. Some physicochemical properties, such as the logarithm of calculated octanol–water partitioning coefficients (logKow and total biodegradation (TBd in mol/h were calculated for compounds 1–20 from S. nigrum L.

  3. Raman spectroscopy, electronic microscopy and SPME-GC-MS to elucidate the mode of action of a new antimicrobial food packaging material.

    Science.gov (United States)

    Clemente, Isabel; Aznar, Margarita; Salafranca, Jesús; Nerín, Cristina

    2017-02-01

    One critical challenge when developing a new antimicrobial packaging material is to demonstrate the mode of action of the antimicrobials incorporated into the packaging. For this task, several analytical techniques as well as microbiology are required. In this work, the antimicrobial properties of benzyl isothiocyanate, allyl isothiocyanate and essential oils of cinnamon and oregano against several moulds and bacteria have been evaluated. Benzyl isothiocyanate showed the highest antimicrobial activity and it was selected for developing the new active packaging material. Scanning electron microscopy and Raman spectroscopy were successfully used to demonstrate the mode of action of benzyl isothiocyanate on Escherichia coli. Bacteria exhibited external modifications such as oval shape and the presence of septum surface, but they did not show any disruption or membrane damage. To provide data on the in vitro action of benzyl isothiocyanate and the presence of inhibition halos, the transfer mechanism to the cells was assessed using solid-phase microextraction-gas chromatography-mass spectrometry. Based on the transfer system, action mechanism and its stronger antimicrobial activity, benzyl isothiocyanate was incorporated to two kinds of antimicrobial labels. The labels were stable and active for 140 days against two mould producers of ochratoxin A; Penicillium verrucosum is more sensitive than Aspergillus ochraceus. Details about the analytical techniques and the results obtained are shown and discussed. Graphical Abstract Antimicrobial evaluation of pure compounds, incorporation in the packaging and study for mode of action on S. coli by Raman, SEM and SPME-GC-MS.

  4. Sensitive multiresidue method by HS-SPME/GC-MS for 10 volatile organic compounds in urine matrix: a new tool for biomonitoring studies on children.

    Science.gov (United States)

    Antonucci, Arianna; Vitali, Matteo; Avino, Pasquale; Manigrasso, Maurizio; Protano, Carmela

    2016-08-01

    A HS-SPME method coupled with GC-MS analysis has been developed for simultaneously measuring the concentration of 10 volatile organic compounds (VOCs) (benzene, toluene, ethylbenzene, o-, m-, and p-xylene, methyl tert-butyl ether, ethyl tert-butyl ether, 2-methyl-2-butyl methyl ether, and diisopropyl ether) in urine matrix as a biomonitoring tool for populations at low levels of exposure to such VOCs. These compounds, potentially toxic for human health, are common contaminants of both outdoor and indoor air, as they are released by autovehicular traffic; some of them are also present in environmental tobacco smoke (ETS). Thus, the exposure to these pollutants cannot be neglected and should be assessed. The low limits of detection and quantification (LODs and LOQs <6.5 and 7.5 ng L(-1), respectively) and the high reproducibility (CVs <4 %) make the developed method suited for biomonitoring populations exposed at low levels such as children. Further, the method is cost-effective and low in time-consumption; therefore, it is useful for investigating large populations. It has been applied to children exposed to traffic pollution and/or ETS; the relevant results are reported, and the relevant implications are discussed.

  5. Non-destructive profiling of volatile organic compounds using HS-SPME/GC-MS and its application for the geographical discrimination of white rice.

    Science.gov (United States)

    Lim, Dong Kyu; Mo, Changyeun; Lee, Dong-Kyu; Long, Nguyen Phuoc; Lim, Jongguk; Kwon, Sung Won

    2018-01-01

    The authenticity determination of white rice is crucial to prevent deceptive origin labeling and dishonest trading. However, a non-destructive and comprehensive method for rapidly discriminating the geographical origins of white rice between countries is still lacking. In the current study, we developed a volatile organic compound based geographical discrimination method using headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME/GC-MS) to discriminate rice samples from Korea and China. A partial least squares discriminant analysis (PLS-DA) model exhibited a good classification of white rice between Korea and China (accuracy = 0.958, goodness of fit = 0.937, goodness of prediction = 0.831, and permutation test p-value = 0.043). Combining the PLS-DA based feature selection with the differentially expressed features from the unpaired t-test and significance analysis of microarrays, 12 discriminatory biomarkers were found. Among them, hexanal and 1-hexanol have been previously known to be associated with the cultivation environment and storage conditions. Other hydrocarbon biomarkers are novel, and their impact on rice production and storage remains to be elucidated. In conclusion, our findings highlight the ability to rapidly discriminate white rice from Korea and China. The developed method maybe useful for the authenticity and quality control of white rice. Copyright © 2017. Published by Elsevier B.V.

  6. Aroma volatiles obtained at harvest by HS-SPME/GC-MS and INDEX/MS-E-nose fingerprint discriminate climacteric behaviour in melon fruit.

    Science.gov (United States)

    Chaparro-Torres, Libia A; Bueso, María C; Fernández-Trujillo, Juan P

    2016-05-01

    Melon aroma volatiles were extracted at harvest from juice of a climacteric near-isogenic line (NIL) SC3-5-1 with two quantitative trait loci (QTLs) introgressed which produced climacteric behaviour and its non-climacteric parental (PS) using two methodologies of analysis: static headspace solid phase micro-extraction (HS-SPME) by gas chromatography-mass spectrometry (GC-MS) and inside needle dynamic extraction (INDEX) by MS-based electronic nose (MS-E-nose). Of the 137 volatiles compounds identified, most were found at significantly higher concentrations in SC3-5-1 than in PS in both seasons. These volatiles were mostly esters, alcohols, sulfur-derived esters and even some aldehydes and others. The number of variables with high correlation values was reduced by using correlation network analysis. Partial least squares-discriminant analysis (PLS-DA) achieved the correct classification of PS and SC3-5-1. The ions m/z 74, 91, 104, 105, 106 and 108, mainly volatile derivatives precursor phenylalanine, were the most discriminant in SC3-5-1 and PS. As many as 104 QTLs were mapped in season 1 and at least 78 QTLs in each season with an effect above the PS mean. GC-MS gave better discrimination than E-nose. Most of the QTLs that mapped in both seasons enhanced aroma volatiles associated with climacteric behaviour. © 2015 Society of Chemical Industry.

  7. HS-SPME optimization and extraction of volatile compounds from soursop (Annona muricata L. pulp with emphasis on their characteristic impact compounds

    Directory of Open Access Journals (Sweden)

    Karen Leticia de SANTANA

    Full Text Available Abstract Aroma and taste are decisive factors in the selection of any food. The aim of this study was to extract the volatile compounds present in soursop (Annona muricata L. pulp by Solid-phase microextraction (SPME technique using 3 different fibers (DVB/CAR/ PDMS, CAR/PDMS and PDMS/DVB. An experimental design was set up to evaluate the best extraction conditions wherein the variables were adsorption temperature, ionic strength and pulp concentration. The separation of volatiles was performed in chromatographic columns of different polarity (polar and non-polar while volatile compounds were identified by analysis in high resolution gas chromatography system coupled with mass spectrometry. The results obtained using 3 different fibers revealed the capture of about 40 compounds. The CAR/PDMS fiber was more efficient for the capture of esters and DVB/CAR/PDMS fiber for terpenes. The optimum conditions for capture of higher number of volatiles for polar column were 45 °C for extraction, 15% of ionic strength and 50% of pulp concentration which resulted in separation of 87 compounds. Among the principal character impact compounds from soursop are (E-2-hexenoate, methyl hexenoate and linalool.

  8. Determination of Hazardous VOCs and Nicotine Released from Mainstream Smoke by the Combination of the SPME and GC-MS Methods

    Directory of Open Access Journals (Sweden)

    Sudhir Kumar Pandey

    2010-01-01

    Full Text Available In this study, the contents of nicotine and volatile organic compounds (VOCs in mainstream smoke (MSS were analyzed using samples of four cigarette types consisting of two common brands (R and E with full (F and light (L flavor, coded with R-F, R-L, E-F, and E-L. These cigarettes were also analyzed after removing the filter portions with the assignment of a new sample code of (N as the third letter (e.g., R-L-N. A total of 44 VOCs (including nicotine were quantified by the combination of the SPME and GC-MS methods. Out of the 44 VOCs, 10 were identified as hazardous air pollutants listed by the U.S. EPA, while their concentrations exceeded the reference exposure limits set by various agencies. A clear distinction was apparent in the concentration levels of VOCs between different brands or between full and light flavors. Nicotine concentrations varied greatly between different cigarettes types of the R brand, whereas such changes were insignificant in the counterpart E brand. This thus suggests that light-flavor cigarettes do not necessarily guarantee low doses of carcinogens (and tar than regular cigarettes, as their differences can be balanced by the inhaling behavior of the smoker.

  9. HS-SPME-GC-MS/MS Method for the Rapid and Sensitive Quantitation of 2-Acetyl-1-pyrroline in Single Rice Kernels.

    Science.gov (United States)

    Hopfer, Helene; Jodari, Farman; Negre-Zakharov, Florence; Wylie, Phillip L; Ebeler, Susan E

    2016-05-25

    Demand for aromatic rice varieties (e.g., Basmati) is increasing in the US. Aromatic varieties typically have elevated levels of the aroma compound 2-acetyl-1-pyrroline (2AP). Due to its very low aroma threshold, analysis of 2AP provides a useful screening tool for rice breeders. Methods for 2AP analysis in rice should quantitate 2AP at or below sensory threshold level, avoid artifactual 2AP generation, and be able to analyze single rice kernels in cases where only small sample quantities are available (e.g., breeding trials). We combined headspace solid phase microextraction with gas chromatography tandem mass spectrometry (HS-SPME-GC-MS/MS) for analysis of 2AP, using an extraction temperature of 40 °C and a stable isotopologue as internal standard. 2AP calibrations were linear between the concentrations of 53 and 5380 pg/g, with detection limits below the sensory threshold of 2AP. Forty-eight aromatic and nonaromatic, milled rice samples from three harvest years were screened with the method for their 2AP content, and overall reproducibility, observed for all samples, ranged from 5% for experimental aromatic lines to 33% for nonaromatic lines.

  10. Effect of hot air drying on volatile compounds of Flammulina velutipes detected by HS-SPME-GC-MS and electronic nose.

    Science.gov (United States)

    Yang, Wenjian; Yu, Jie; Pei, Fei; Mariga, Alfred Mugambi; Ma, Ning; Fang, Yong; Hu, Qiuhui

    2016-04-01

    Volatile compounds are important factors that affect the flavor quality of Flammulina velutipes, but the changes occurring during hot air drying is still unclear. To clarify the dynamic changes of flavor components during hot air drying, comprehensive flavor characterization and volatile compounds of F. velutipes were evaluated using electronic nose technology and headspace solid phase micro-extraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS), respectively. Results showed that volatile components in F. velutipes significantly changed during hot air drying according to the principal component analysis and radar fingerprint chart of electronic nose. Volatile compounds of fresh F. velutipes consisted mainly of ketones, aldehydes and alcohols, and 3-octanone was the dominant compound. Drying process could significantly decrease the relative content of ketones and promoted the generation of alcohols, acids, and esters, which became the main volatile compounds of dried F. velutipes. These may provide a theoretical basis for the formation mechanism of flavor substances in dried F. velutipes. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Study of aroma formation and transformation during the manufacturing process of Biluochun green tea in Yunnan Province by HS-SPME and GC-MS.

    Science.gov (United States)

    Wang, Chen; Lv, Shidong; Wu, Yuanshuang; Lian, Ming; Gao, Xuemei; Meng, Qingxiong

    2016-10-01

    Biluochun is a typical non-fermented tea and is also famous for its unique aroma in China. Few studies have been performed to evaluate the effect of the manufacturing process on the formation and content of its aroma. The volatile components were extracted at different manufacturing process steps of Biluochun green tea using fully automated headspace solid-phase microextraction (HS-SPME) and further characterised by gas chromatography-mass spectrometry (GC-MS). Among 67 volatile components collected, the fractions of linalool oxides, β-ionone, phenylacetaldehyde, aldehydes, ketones, and nitrogen compounds were increased while alcohols and hydrocarbons declined during the manufacturing process. The aroma compounds decreased the most during the drying steps. We identified a number of significantly changed components that can be used as markers and quality control during the producing process of Biluochun. The drying step played a major role in the aroma formation of green tea products and should be the most important step for quality control. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  12. Non-destructive profiling of volatile organic compounds using HS-SPME/GC–MS and its application for the geographical discrimination of white rice

    Directory of Open Access Journals (Sweden)

    Dong Kyu Lim

    2018-01-01

    Full Text Available The authenticity determination of white rice is crucial to prevent deceptive origin labeling and dishonest trading. However, a non-destructive and comprehensive method for rapidly discriminating the geographical origins of white rice between countries is still lacking. In the current study, we developed a volatile organic compound based geographical discrimination method using headspace solid-phase microextraction coupled to gas chromatography–mass spectrometry (HS-SPME/GC–MS to discriminate rice samples from Korea and China. A partial least squares discriminant analysis (PLS-DA model exhibited a good classification of white rice between Korea and China (accuracy = 0.958, goodness of fit = 0.937, goodness of prediction = 0.831, and permutation test p-value = 0.043. Combining the PLS-DA based feature selection with the differentially expressed features from the unpaired t-test and significance analysis of microarrays, 12 discriminatory biomarkers were found. Among them, hexanal and 1-hexanol have been previously known to be associated with the cultivation environment and storage conditions. Other hydrocarbon biomarkers are novel, and their impact on rice production and storage remains to be elucidated. In conclusion, our findings highlight the ability to rapidly discriminate white rice from Korea and China. The developed method maybe useful for the authenticity and quality control of white rice.

  13. Characterization of volatile profile from ten different varieties of Chinese jujubes by HS-SPME/GC-MS coupled with E-nose.

    Science.gov (United States)

    Chen, Qinqin; Song, Jianxin; Bi, Jinfeng; Meng, Xianjun; Wu, Xinye

    2018-03-01

    Volatile profile of ten different varieties of fresh jujubes was characterized by HS-SPME/GC-MS (headspace solid phase micro-extraction combined with gas chromatography-mass spectrometry) and E-nose (electronic nose). GC-MS results showed that a total of 51 aroma compounds were identified in jujubes, hexanoic acid, hexanal, (E)-2-hexenal, (Z)-2-heptenal, benzaldehyde and (E)-2-nonenal were the main aroma components with contributions that over 70%. Differentiation of jujube varieties was conducted by cluster analysis of GC-MS data and principal component analysis & linear discriminant analysis of E-nose data. Both results showed that jujubes could be mainly divided into two groups: group A (JZ, PDDZ, JSXZ and LWZZ) and group B (BZ, YZ, MZ, XZ and DZ). There were significant differences in contents of alcohols, acids and aromatic compounds between group A and B. GC-MS coupled with E-nose could be a fast and accurate method to identify the general flavor difference in different varieties of jujubes. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Effect of the type of frying culinary fat on volatile compounds isolated in fried pork loin chops by using SPME-GC-MS.

    Science.gov (United States)

    Ramírez, María Rosario; Estévez, Mario; Morcuende, David; Cava, Ramón

    2004-12-15

    The effect of the type of frying culinary fat (olive oil, sunflower oil, butter, and pig lard) on volatile compounds isolated from fried pork loin chops (m. Longissimus dorsi) was measured by SPME-GC-MS. Frying modified the fatty acid composition of lipids from pork loin chops, which tended to be similar to that of the culinary fat used to fry. Volatile compounds formed from the oxidation of fatty acids increased, such as aldehydes, ketones, alcohols, and hydrocarbons. Besides, each culinary fat used modified the volatile profiles in fried meat differently. Sunflower oil-fried pork loin chops presented the highest aldehyde aliphatic content, probably due to their highest content of polyunsaturated acids. Hexanal, the most abundant aldehyde in fried samples, presented the most elevated content in sunflower oil-fried pork loin chops. In addition, these samples presented more heterocyclic compounds from the Maillard reaction than other fried samples. Volatiles detected in olive oil-fried pork loin chops were mainly lipid-derived compounds such as pentan-1-ol, hexanal, hept-2-enal, nonanal, decanal, benzaldehyde, and nonan-2-one. Butter-fried pork loins were abundant in ketones with a high number of carbons (heptan-2-one, nonan-2-one, undecan-2-one, tridecanone, and heptadecan-2-one). Pig lard-fried pork loin chops presented some Strecker aldehydes isolated in only these samples, such as 2-methylbutanal and 3-(methylthio)propanal, and a sulfur compound (dimethyl disulfide) related to Strecker aldehydes.

  15. Degradation product emission from historic and modern books by headspace SPME/GC-MS: evaluation of lipid oxidation and cellulose hydrolysis.

    Science.gov (United States)

    Clark, Andrew J; Calvillo, Jesse L; Roosa, Mark S; Green, David B; Ganske, Jane A

    2011-04-01

    Volatile organic compounds emitted from a several decade series of bound periodicals (1859-1939) printed on ground wood paper, as well as historical books dating from the 1500s to early 1800s made from cotton/linen rag, were studied using an improved headspace SPME/GC-MS method. The headspace over the naturally aging books, stored upright in glass chambers, was monitored over a 24-h period, enabling the identification of a wide range of organic compounds emanating from the whole of the book. The detection of particular straight chain aldehydes, as well as characteristic alcohols, alkenes and ketones is correlated with oxidative degradation of the C(18) fatty acid constituency of paper. The relative importance of hydrolytic and oxidative chemistry involved in paper aging in books published between 1560 and 1939 was examined by comparing the relative abundances of furfural (FUR) a known cellulose hydrolysis product, and straight chain aldehydes (SCA) produced from the oxidation of fatty acids in paper. The relative abundance of furfural is shown to increase across the 379-year publication time span. A comparison of relative SCA peak areas across the series of books examined reveals that SCA emission is more important in the cotton/linen rag books than in the ground wood books.

  16. Implicitly Weighted Methods in Robust Image Analysis

    Czech Academy of Sciences Publication Activity Database

    Kalina, Jan

    2012-01-01

    Roč. 44, č. 3 (2012), s. 449-462 ISSN 0924-9907 R&D Projects: GA MŠk(CZ) 1M06014 Institutional research plan: CEZ:AV0Z10300504 Keywords : robustness * high breakdown point * outlier detection * robust correlation analysis * template matching * face recognition Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 1.767, year: 2012

  17. What is it to be sturdy (robust)?

    DEFF Research Database (Denmark)

    Nielsen, Niss Skov; Zwisler, Lars Pagter; Bojsen, Ann Kristina Mikkelsen

    Purpose: This paper intends to give a first insight into the concept of being "sturdy/robust"; To develop and test a Danish model of how to measure sturdi-ness/robustness; To test the scale's ability to identify people in emergency situa-tions who have high risk of developing psychological illness....

  18. Structural Robustness Evaluation of Offshore Wind Turbines

    DEFF Research Database (Denmark)

    Giuliani, Luisa; Bontempi, Franco

    2010-01-01

    in the framework of a safe design: it depends on different factors, like exposure, vulnerability and robustness. Particularly, the requirement of structural vulnerability and robustness are discussed in this paper and a numerical application is presented, in order to evaluate the effects of a ship collision...

  19. In Silico Design of Robust Bolalipid Membranes

    NARCIS (Netherlands)

    Bulacu, Monica; Periole, Xavier; Marrink, Siewert J.; Périole, Xavier

    The robustness of microorganisms used in industrial fermentations is essential for the efficiency and yield of the production process. A viable tool to increase the robustness is through engineering of the cell membrane and especially by incorporating lipids from species that survive under harsh

  20. Assessment of Process Robustness for Mass Customization

    DEFF Research Database (Denmark)

    Nielsen, Kjeld; Brunø, Thomas Ditlev

    2013-01-01

    robustness and their capability to develop it. Through literature study and analysis of robust process design characteristics a number of metrics are described which can be used for assessment. The metrics are evaluated and analyzed to be applied as KPI’s to help MC companies prioritize efforts in business...

  1. Applying Robust Design in an Industrial Context

    DEFF Research Database (Denmark)

    Christensen, Martin Ebro

    mechanical architectures. Furthermore a set of 15 robust design principles for reducing the variation in functional performance is compiled in a format directly supporting the work of the design engineer. With these foundational methods in place, the existing tools, methods and KPIs of Robust Design...

  2. The importance of robust design methodology

    DEFF Research Database (Denmark)

    Eifler, Tobias; Howard, Thomas J.

    2018-01-01

    infamous recalls in automotive history, that of the GM ignition switch, from the perspective of Robust Design. It is investigated if available Robust Design methods such as sensitivity analysis, tolerance stack-ups, design clarity, etc. would have been suitable to account for the performance variation...

  3. Robust Control Charts for Time Series Data

    NARCIS (Netherlands)

    Croux, C.; Gelper, S.; Mahieu, K.

    2010-01-01

    This article presents a control chart for time series data, based on the one-step- ahead forecast errors of the Holt-Winters forecasting method. We use robust techniques to prevent that outliers affect the estimation of the control limits of the chart. Moreover, robustness is important to maintain

  4. Efficient reanalysis techniques for robust topology optimization

    DEFF Research Database (Denmark)

    Amir, Oded; Sigmund, Ole; Lazarov, Boyan Stefanov

    2012-01-01

    efficient robust topology optimization procedures based on reanalysis techniques. The approach is demonstrated on two compliant mechanism design problems where robust design is achieved by employing either a worst case formulation or a stochastic formulation. It is shown that the time spent on finite...

  5. Extending the Scope of Robust Quadratic Optimization

    NARCIS (Netherlands)

    Marandi, Ahmadreza; Ben-Tal, A.; den Hertog, Dick; Melenberg, Bertrand

    In this paper, we derive tractable reformulations of the robust counterparts of convex quadratic and conic quadratic constraints with concave uncertainties for a broad range of uncertainty sets. For quadratic constraints with convex uncertainty, it is well-known that the robust counterpart is, in

  6. Security and robustness for collaborative monitors

    NARCIS (Netherlands)

    Testerink, Bas; Bulling, Nils; Dastani, Mehdi

    2016-01-01

    Decentralized monitors can be subject to robustness and security risks. Robustness risks include attacks on the monitor’s infrastructure in order to disable parts of its functionality. Security risks include attacks that try to extract information from the monitor and thereby possibly leak sensitive

  7. How Robust is Your System Resilience?

    Science.gov (United States)

    Homayounfar, M.; Muneepeerakul, R.

    2017-12-01

    Robustness and resilience are concepts in system thinking that have grown in importance and popularity. For many complex social-ecological systems, however, robustness and resilience are difficult to quantify and the connections and trade-offs between them difficult to study. Most studies have either focused on qualitative approaches to discuss their connections or considered only one of them under particular classes of disturbances. In this study, we present an analytical framework to address the linkage between robustness and resilience more systematically. Our analysis is based on a stylized dynamical model that operationalizes a widely used concept framework for social-ecological systems. The model enables us to rigorously define robustness and resilience and consequently investigate their connections. The results reveal the tradeoffs among performance, robustness, and resilience. They also show how the nature of the such tradeoffs varies with the choices of certain policies (e.g., taxation and investment in public infrastructure), internal stresses and external disturbances.

  8. A Survey on Robustness in Railway Planning

    DEFF Research Database (Denmark)

    Lusby, Richard Martin; Larsen, Jesper; Bull, Simon Henry

    2018-01-01

    Planning problems in passenger railway range from long term strategic decision making to the detailed planning of operations.Operations research methods have played an increasing role in this planning process. However, recently more attention has been given to considerations of robustness...... in the quality of solutions to individual planning problems, and of operations in general. Robustness in general is the capacity for some system to absorb or resist changes. In the context of railway robustness it is often taken to be the capacity for operations to continue at some level when faced...... with a disruption such as delay or failure. This has resulted in more attention given to the inclusion of robustness measures and objectives in individual planning problems, and to the providing of tools to ensure operations continue under disrupted situations. In this paper we survey the literature on robustness...

  9. International Conference on Robust Statistics 2015

    CERN Document Server

    Basu, Ayanendranath; Filzmoser, Peter; Mukherjee, Diganta

    2016-01-01

    This book offers a collection of recent contributions and emerging ideas in the areas of robust statistics presented at the International Conference on Robust Statistics 2015 (ICORS 2015) held in Kolkata during 12–16 January, 2015. The book explores the applicability of robust methods in other non-traditional areas which includes the use of new techniques such as skew and mixture of skew distributions, scaled Bregman divergences, and multilevel functional data methods; application areas being circular data models and prediction of mortality and life expectancy. The contributions are of both theoretical as well as applied in nature. Robust statistics is a relatively young branch of statistical sciences that is rapidly emerging as the bedrock of statistical analysis in the 21st century due to its flexible nature and wide scope. Robust statistics supports the application of parametric and other inference techniques over a broader domain than the strictly interpreted model scenarios employed in classical statis...

  10. Defining robustness protocols: a method to include and evaluate robustness in clinical plans

    International Nuclear Information System (INIS)

    McGowan, S E; Albertini, F; Lomax, A J; Thomas, S J

    2015-01-01

    We aim to define a site-specific robustness protocol to be used during the clinical plan evaluation process. Plan robustness of 16 skull base IMPT plans to systematic range and random set-up errors have been retrospectively and systematically analysed. This was determined by calculating the error-bar dose distribution (ebDD) for all the plans and by defining some metrics used to define protocols aiding the plan assessment. Additionally, an example of how to clinically use the defined robustness database is given whereby a plan with sub-optimal brainstem robustness was identified. The advantage of using different beam arrangements to improve the plan robustness was analysed. Using the ebDD it was found range errors had a smaller effect on dose distribution than the corresponding set-up error in a single fraction, and that organs at risk were most robust to the range errors, whereas the target was more robust to set-up errors. A database was created to aid planners in terms of plan robustness aims in these volumes. This resulted in the definition of site-specific robustness protocols. The use of robustness constraints allowed for the identification of a specific patient that may have benefited from a treatment of greater individuality. A new beam arrangement showed to be preferential when balancing conformality and robustness for this case. The ebDD and error-bar volume histogram proved effective in analysing plan robustness. The process of retrospective analysis could be used to establish site-specific robustness planning protocols in proton therapy. These protocols allow the planner to determine plans that, although delivering a dosimetrically adequate dose distribution, have resulted in sub-optimal robustness to these uncertainties. For these cases the use of different beam start conditions may improve the plan robustness to set-up and range uncertainties. (paper)

  11. Defining robustness protocols: a method to include and evaluate robustness in clinical plans

    Science.gov (United States)

    McGowan, S. E.; Albertini, F.; Thomas, S. J.; Lomax, A. J.

    2015-04-01

    We aim to define a site-specific robustness protocol to be used during the clinical plan evaluation process. Plan robustness of 16 skull base IMPT plans to systematic range and random set-up errors have been retrospectively and systematically analysed. This was determined by calculating the error-bar dose distribution (ebDD) for all the plans and by defining some metrics used to define protocols aiding the plan assessment. Additionally, an example of how to clinically use the defined robustness database is given whereby a plan with sub-optimal brainstem robustness was identified. The advantage of using different beam arrangements to improve the plan robustness was analysed. Using the ebDD it was found range errors had a smaller effect on dose distribution than the corresponding set-up error in a single fraction, and that organs at risk were most robust to the range errors, whereas the target was more robust to set-up errors. A database was created to aid planners in terms of plan robustness aims in these volumes. This resulted in the definition of site-specific robustness protocols. The use of robustness constraints allowed for the identification of a specific patient that may have benefited from a treatment of greater individuality. A new beam arrangement showed to be preferential when balancing conformality and robustness for this case. The ebDD and error-bar volume histogram proved effective in analysing plan robustness. The process of retrospective analysis could be used to establish site-specific robustness planning protocols in proton therapy. These protocols allow the planner to determine plans that, although delivering a dosimetrically adequate dose distribution, have resulted in sub-optimal robustness to these uncertainties. For these cases the use of different beam start conditions may improve the plan robustness to set-up and range uncertainties.

  12. EVALUACIÓN DE PLAGUICIDAS 0RGAN0CL0RAD0S POR HS-SPME - GC/ECD EN LECHE PASTEURIZADA COMERCIALIZADA EN LA CIUDAD DE CARTAGENA (COLOMBIA A AVALIAQÁO DOS PESTICIDAS ORGANOCLORADOS POR HS-SPME - GC/ECD EM LEITE PASTEURIZADO COMERCIALIZADAS NA CIDADE CARTAGENA (COLOMBIA EVALUATION OF PESTICIDES BY HS-SPME ORGANOCHLORINE - GC / ECD IN PASTEURIZED MILK MARKETED IN THE CITY CARTAGENA (COLOMBIA

    Directory of Open Access Journals (Sweden)

    DENILES DEL CARMEN DE ARCO R

    2011-12-01

    Full Text Available Los plaguicidas han sido utilizados en todo el mundo desde mediados del siglo XX, en campañas de Salud Pública y en prácticas agrícolas. Los Plaguicidas Organoclorados (POCs presentan mayor impacto sobre el ambiente porque no son biodegradables, son lipofílicos, tienen gran movilidad por todo el planeta y gran tendencia a la bioacumulación, através de la cadena trófica. Con el objetivo de identificar y cuantificar plaguicidas organoclorados en leche entera pasteurizada de dos marcas (A y B, que se comercializan en la ciudad de Cartagena de Indias, se realizó la presente investigación, utilizando Microextracción en Fase Sólida en Espacio de Cabeza y Cromatografía de Gases con Detector de Captura de Electrones (HS-SPME-GC/ECD. Fueron analizadas 36 muestras (n=36, 18 de cada marca. El 100% de las muestras (n=36 resultaron positivas para el plaguicida lindano (γ-HCH, superando el Límite Máximo Residual (LMR de 0,01 mg/kg, establecido por la Food and Agriculture Organization y la Organización Mundial de la Salud (FAO/OMS. Las concentraciones promedio de lindano obtenidas para la marca A fueron de 0,042 mg/kg ± 0,003 y 0,062 ± 0,0016 mg/kg (base grasa para la marca B, no superando la Ingesta Diaria Admisible (IDA de 0,001 mg/kg de peso corporal.Os pesticidas têm sido usados em todo o mundo desde meados do século XX, as campanhas de saúde pública e práticas agrícolas. Os inseticidas organoclorados (AP têm maior impacto sobre o meio ambiente porque não são biodegradáveis, são lipofílicas, têm grande mobilidade ao redor do mundo e maior tendencia para a bioacumulação através da cadeia alimentar. A fim de identificar e quantificar pesticidas organoclorados em leite integral, duas marcas (A e B, comercializada na cidade de Cartagena das Índias, a presente investigação foi realizada por cromatografia em Fase Sólida, Microextração Headspace Gás com Detector de Captura de Elétrons(HS-SPME-GC/ECD. 36 amostras foram

  13. Robust recognition via information theoretic learning

    CERN Document Server

    He, Ran; Yuan, Xiaotong; Wang, Liang

    2014-01-01

    This Springer Brief represents a comprehensive review of information theoretic methods for robust recognition. A variety of information theoretic methods have been proffered in the past decade, in a large variety of computer vision applications; this work brings them together, attempts to impart the theory, optimization and usage of information entropy.The?authors?resort to a new information theoretic concept, correntropy, as a robust measure and apply it to solve robust face recognition and object recognition problems. For computational efficiency,?the brief?introduces the additive and multip

  14. Robust statistics and geochemical data analysis

    International Nuclear Information System (INIS)

    Di, Z.

    1987-01-01

    Advantages of robust procedures over ordinary least-squares procedures in geochemical data analysis is demonstrated using NURE data from the Hot Springs Quadrangle, South Dakota, USA. Robust principal components analysis with 5% multivariate trimming successfully guarded the analysis against perturbations by outliers and increased the number of interpretable factors. Regression with SINE estimates significantly increased the goodness-of-fit of the regression and improved the correspondence of delineated anomalies with known uranium prospects. Because of the ubiquitous existence of outliers in geochemical data, robust statistical procedures are suggested as routine procedures to replace ordinary least-squares procedures

  15. Design Robust Controller for Rotary Kiln

    Directory of Open Access Journals (Sweden)

    Omar D. Hernández-Arboleda

    2013-11-01

    Full Text Available This paper presents the design of a robust controller for a rotary kiln. The designed controller is a combination of a fractional PID and linear quadratic regulator (LQR, these are not used to control the kiln until now, in addition robustness criteria are evaluated (gain margin, phase margin, strength gain, rejecting high frequency noise and sensitivity applied to the entire model (controller-plant, obtaining good results with a frequency range of 0.020 to 90 rad/s, which contributes to the robustness of the system.

  16. Towards distortion-free robust image authentication

    International Nuclear Information System (INIS)

    Coltuc, D

    2007-01-01

    This paper investigates a general framework for distortion-free robust image authentication by multiple marking. First, by robust watermarking a subsampled version of image edges is embedded. Then, by reversible watermarking the information needed to recover the original image is inserted, too. The hiding capacity of the reversible watermarking is the essential requirement for this approach. Thus in case of no attacks not only image is authenticated but also the original is exactly recovered. In case of attacks, reversibility is lost, but image can still be authenticated. Preliminary results providing very good robustness against JPEG compression are presented

  17. An Overview of the Adaptive Robust DFT

    Directory of Open Access Journals (Sweden)

    Djurović Igor

    2010-01-01

    Full Text Available Abstract This paper overviews basic principles and applications of the robust DFT (RDFT approach, which is used for robust processing of frequency-modulated (FM signals embedded in non-Gaussian heavy-tailed noise. In particular, we concentrate on the spectral analysis and filtering of signals corrupted by impulsive distortions using adaptive and nonadaptive robust estimators. Several adaptive estimators of location parameter are considered, and it is shown that their application is preferable with respect to non-adaptive counterparts. This fact is demonstrated by efficiency comparison of adaptive and nonadaptive RDFT methods for different noise environments.

  18. A robust interpretation of duration calculus

    DEFF Research Database (Denmark)

    Franzle, M.; Hansen, Michael Reichhardt

    2005-01-01

    We transfer the concept of robust interpretation from arithmetic first-order theories to metric-time temporal logics. The idea is that the interpretation of a formula is robust iff its truth value does not change under small variation of the constants in the formula. Exemplifying this on Duration...... Calculus (DC), our findings are that the robust interpretation of DC is equivalent to a multi-valued interpretation that uses the real numbers as semantic domain and assigns Lipschitz-continuous interpretations to all operators of DC. Furthermore, this continuity permits approximation between discrete...

  19. REINA at CLEF 2007 Robust Task

    OpenAIRE

    Zazo Rodríguez, Ángel Francisco; Figuerola, Carlos G.; Alonso Berrocal, José Luis

    2007-01-01

    This paper describes our work at CLEF 2007 Robust Task. We have participated in the monolingual (English, French and Portuguese) and the bilingual (English to French) subtask. At CLEF 2006 our research group obtained very good results applying local query expansion using windows of terms in the robust task. This year we have used the same expansion technique, but taking into account some criteria of robustness: MAP, GMAP, MMR, GS@10, P@10, number of failed topics, number of topics bellow 0.1 ...

  20. REINA at CLEF 2007 Robust Track (2007)

    OpenAIRE

    Zazo, Ángel F.; G.-Figuerola, Carlos; Alonso-Berrocal, José-Luis

    2007-01-01

    This paper describes our work at CLEF 2007 Robust Task. We have participated in the monolingual (English, French and Portuguese) and the bilingual (English to French) subtask. At CLEF 2006 our research group obtained very good results applying local query expansion using windows of terms in the robust task. This year we have used the same expansion technique, but taking into account some criteria of robustness: MAP, GMAP, MMR, GS@10, P@10, number of failed topics, number of topics bellow 0.1 ...

  1. Danish Requirements for Robustness of Structures

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Christensen, H. H.

    2006-01-01

    . This paper describes the background of the revised robustness requirements implemented in the Danish Code of Practice for Safety of Structures in 2003 [1, 2, 3]. According to the Danish design rules robustness shall be documented for all structures where consequences of failure are serious. This paper...... describes the background of the design procedure in the Danish codes, which shall be followed in order to document sufficient robustness in the following steps: Step 1: review of loads and possible failure modes/scenarios and determination of acceptable collapse extent. Step 2: review of the structural...

  2. Robustness-related issues in speaker recognition

    CERN Document Server

    Zheng, Thomas Fang

    2017-01-01

    This book presents an overview of speaker recognition technologies with an emphasis on dealing with robustness issues. Firstly, the book gives an overview of speaker recognition, such as the basic system framework, categories under different criteria, performance evaluation and its development history. Secondly, with regard to robustness issues, the book presents three categories, including environment-related issues, speaker-related issues and application-oriented issues. For each category, the book describes the current hot topics, existing technologies, and potential research focuses in the future. The book is a useful reference book and self-learning guide for early researchers working in the field of robust speech recognition.

  3. Robustness and structure of complex networks

    Science.gov (United States)

    Shao, Shuai

    This dissertation covers the two major parts of my PhD research on statistical physics and complex networks: i) modeling a new type of attack -- localized attack, and investigating robustness of complex networks under this type of attack; ii) discovering the clustering structure in complex networks and its influence on the robustness of coupled networks. Complex networks appear in every aspect of our daily life and are widely studied in Physics, Mathematics, Biology, and Computer Science. One important property of complex networks is their robustness under attacks, which depends crucially on the nature of attacks and the structure of the networks themselves. Previous studies have focused on two types of attack: random attack and targeted attack, which, however, are insufficient to describe many real-world damages. Here we propose a new type of attack -- localized attack, and study the robustness of complex networks under this type of attack, both analytically and via simulation. On the other hand, we also study the clustering structure in the network, and its influence on the robustness of a complex network system. In the first part, we propose a theoretical framework to study the robustness of complex networks under localized attack based on percolation theory and generating function method. We investigate the percolation properties, including the critical threshold of the phase transition pc and the size of the giant component Pinfinity. We compare localized attack with random attack and find that while random regular (RR) networks are more robust against localized attack, Erdoḧs-Renyi (ER) networks are equally robust under both types of attacks. As for scale-free (SF) networks, their robustness depends crucially on the degree exponent lambda. The simulation results show perfect agreement with theoretical predictions. We also test our model on two real-world networks: a peer-to-peer computer network and an airline network, and find that the real-world networks

  4. Robust Structured Control Design via LMI Optimization

    DEFF Research Database (Denmark)

    Adegas, Fabiano Daher; Stoustrup, Jakob

    2011-01-01

    This paper presents a new procedure for discrete-time robust structured control design. Parameter-dependent nonconvex conditions for stabilizable and induced L2-norm performance controllers are solved by an iterative linear matrix inequalities (LMI) optimization. A wide class of controller...... structures including decentralized of any order, fixed-order dynamic output feedback, static output feedback can be designed robust to polytopic uncertainties. Stability is proven by a parameter-dependent Lyapunov function. Numerical examples on robust stability margins shows that the proposed procedure can...

  5. Determination of Volatile Organic Compounds (VOCs from Wrapping Films and Wrapped PDO Italian Cheeses by Using HS-SPME and GC/MS

    Directory of Open Access Journals (Sweden)

    Sara Panseri

    2014-06-01

    Full Text Available Nowadays food wrapping assures attractive presentation and simplifies self-service shopping. Polyvinylchloride (PVC- and polyethylene (PE-based cling-films are widely used worldwide for wrapping cheeses. For this purpose, films used in retail possess suitable technical properties such as clinginess and unrolling capacity, that are achieved by using specific plasticizers during their manufacturing process. In the present study, the main VOCs of three cling-films (either PVC-based or PE-based for retail use were characterized by means of Solid-Phase Micro-Extraction and GC/MS. In addition, the effects of cling film type and contact time on the migration of VOCs from the films to four different PDO Italian cheeses during cold storage under light or dark were also investigated. Among the VOCs isolated from cling-films, PVC released 2-ethylhexanol and triacetin. These compounds can likely be considered as a “non-intentionally added substance”. These same compounds were also detected in cheeses wrapped in PVC films with the highest concentration found after 20 days storage. The PE cling-film was shown to possess a simpler VOC profile, lacking some molecules peculiar to PVC films. The same conclusions can be drawn for cheeses wrapped in the PE cling-film. Other VOCs found in wrapped cheeses were likely to have been released either by direct transfer from the materials used for the manufacture of cling-films or from contamination of the films. Overall, HS-SPME is shown to be a rapid and solvent free technique to screen the VOCs profile of cling-films, and to detect VOCs migration from cling-films to cheese under real retail storage conditions.

  6. Determination of Selected Aromas in Marquette and Frontenac Wine Using Headspace-SPME Coupled with GC-MS and Simultaneous Olfactometry

    Directory of Open Access Journals (Sweden)

    Somchai Rice

    2018-03-01

    Full Text Available Understanding the aroma profile of wines made from cold climate grapes is needed to help winemakers produce quality aromatic wines. The current study aimed to add to the very limited knowledge of aroma-imparting compounds in wines made from the lesser-known Frontenac and Marquette cultivars. Headspace solid-phase microextraction (SPME and gas chromatography-mass spectrometry (GC-MS with simultaneous olfactometry was used to identify and quantify selected, aroma-imparting volatile organic compounds (VOC in wines made from grapes harvested at two sugar levels (22° Brix and 24° Brix. Aroma-imparting compounds were determined by aroma dilution analysis (ADA. Odor activity values (OAV were also used to aid the selection of aroma-imparting compounds. Principal component analysis and hierarchical clustering analysis indicated that VOCs in wines produced from both sugar levels of Marquette grapes are similar to each other, and more similar to wines produced from Frontenac grapes harvested at 24° Brix. Selected key aroma compounds in Frontenac and Marquette wines were ethyl hexanoate, ethyl isobutyrate, ethyl octanoate, and ethyl butyrate. OAVs >1000 were reported for three aroma compounds that impart fruity aromas to the wines. This study provides evidence that aroma profiles in Frontenac wines can be influenced by timing of harvesting the berries at different Brix. Future research should focus on whether this is because of berry development or accumulation of aroma precursors and sugar due to late summer dehydration. Simultaneous chemical and sensory analyses can be useful for the understanding development of aroma profile perceptions for wines produced from cold-climate grapes.

  7. Volatile Compound Profiling by HS-SPME/GC-MS-FID of a Core Olive Cultivar Collection as a Tool for Aroma Improvement of Virgin Olive Oil

    Directory of Open Access Journals (Sweden)

    Lourdes García-Vico

    2017-01-01

    Full Text Available Virgin olive oil (VOO is the only food product requiring official sensory analysis to be classified in commercial categories, in which the evaluation of the aroma plays a very important role. The selection of parents, with the aim of obtaining new cultivars with improved oil aroma, is of paramount importance in olive breeding programs. We have assessed the volatile fraction by headspace-solid-phase microextraction/gas chromatography-mass spectrometry-flame ionization detection (HS-SPME/GC-MS-FID and the deduced aroma properties of VOO from a core set of olive cultivars (Core-36 which possesses most of the genetic diversity found in the World Olive Germplasm Collection (IFAPA Alameda del Obispo located in Cordoba, Spain. The VOO volatile fractions of Core-36 cultivars display a high level of variability. It is mostly made of compounds produced from polyunsaturated fatty acids through the lipoxygenase pathway, which confirms to be a general characteristic of the olive species (Olea europaea L.. The main group of volatile compounds in the oils was six straight-chain carbon compounds derived from linolenic acid, some of them being the main contributors to the aroma of the olive oils according to their odor activity values (OAV. The high level of variability found for the volatile fraction of the oils from Core-36 and, therefore, for the aroma odor notes, suggest that this core set may be a very useful tool for the choice of optimal parents in olive breeding programs in order to raise new cultivars with improved VOO aroma.

  8. Identification of Volatile Components of Liverwort (Porella cordaeana Extracts Using GC/MS-SPME and Their Antimicrobial Activity

    Directory of Open Access Journals (Sweden)

    Maria Elisabetta Guerzoni

    2012-06-01

    Full Text Available Chemical constituents of liverwort (Porella cordaeana extracts have been identified using solid-phase microextraction-gas chromatography mass spectrometry (SPME-GC/MS. The methanol, ethanol and ethyl acetate extracts were rich in terpenoids such as sesquiterpene hydrocarbons (53.12%, 51.68%, 23.16%, and monoterpene hydrocarbons (22.83%, 18.90%, 23.36%, respectively. The dominant compounds in the extracts were β-phellandrene (15.54%, 13.66%, 12.10% and β-caryophyllene (10.72%, 8.29%, 7.79%, respectively. The antimicrobial activity of the extracts was evaluated against eleven food microorganisms using the microdilution and disc diffusion methods. The minimum inhibitory concentration (MIC varied from 0.50 to 2.00 mg/mL for yeast strains (Saccharomyces cerevisiae 635, Zygosacharomyces bailii 45, Aerobasidium pullulans L6F, Pichia membranaefaciens OC 71, Pichia membranaefaciens OC 70, Pichia anomala CBS 5759, Pichia anomala DBVPG 3003 and Yarrowia lipolytica RO13, and from 1.00 to 3.00 mg/mL for bacterial strains (Salmonella enteritidis 155, Escherichia coli 555 and Listeria monocytogenes 56Ly. Methanol extract showed better activity in comparison with ethanol and ethyl acetate extracts. High percentages of monoterpene and sesquiterpene hydrocarbons could be responsible for the better antimicrobial activity.

  9. Methodical evaluation and improvement of matrix compatible PDMS-overcoated coating for direct immersion solid phase microextraction gas chromatography (DI-SPME-GC)-based applications.

    Science.gov (United States)

    Souza-Silva, Érica A; Gionfriddo, Emanuela; Shirey, Robert; Sidisky, Len; Pawliszyn, Janusz

    2016-05-12

    The main quest for the implementation of direct SPME to complex matrices has been the development of matrix compatible coatings that provide sufficient sensitivity towards the target analytes. In this context, we present here a thorough evaluation of PDMS-overcoated fibers suitable for simultaneous extraction of different polarities analytes, while maintaining adequate matrix compatibility. For this, eleven analytes were selected, from various application classes (pesticides, industrial chemicals and pharmaceuticals) and with a wide range of log P values (ranging from 1.43 to 6). The model matrix chosen was commercial Concord grape juice, which is rich in pigments such as anthocyanins, and contains approximately 20% of sugar (w/w). Two types of PDMS, as well as other intrinsic factors associated with the PDMS-overcoated fiber fabrication are studied. The evaluation showed that the PDMS-overcoated fibers considerably slowed down the coating fouling process during direct immersion in complex matrices of high sugar content. Longevity differences could be seen between the two types of PDMS tested, with a proprietary Sylgard(®) giving superior performance because of lesser amount of reactive groups and enhanced hydrophobicity. Conversely, the thickness of the outer layer did not seem to have a significant effect on the fiber lifetime. We also demonstrate that the uniformity of the overcoated PDMS layer is paramount to the achievement of reliable data and extended fiber lifetime. Employing the optimum overcoated fiber, limits of detection (LOD) in the range of 0.2-1.3 ng/g could be achieved. Additional improvement is attainable by introducing washing of the coatings after desorption, so that any carbon build-up (fouling) left on the coating surface after thermal desorption can be removed. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. The study of fingerprint characteristics of Dayi Pu-Erh tea using a fully automatic HS-SPME/GC-MS and combined chemometrics method.

    Directory of Open Access Journals (Sweden)

    Shidong Lv

    Full Text Available The quality of tea is presently evaluated by the sensory assessment of professional tea tasters, however, this approach is both inconsistent and inaccurate. A more standardized and efficient method is urgently needed to objectively evaluate tea quality. In this study, the chemical fingerprint of 7 different Dayi Pu-erh tea brands and 3 different Ya'an tea brands on the market were analyzed using fully automatic headspace solid-phase microextraction (HS-SPME combined with gas chromatography-mass spectrometry (GC-MS. A total of 78 volatiles were separated, among 75 volatiles were identified by GC-MS in seven Dayi Pu-erh teas, and the major chemical components included methoxyphenolic compounds, hydrocarbons, and alcohol compounds, such as 1,2,3-trimethoxybenzene, 1,2,4-trimethoxybenzene, 2,6,10,14-tetramethyl-pentadecane, linalool and its oxides, α-terpineol, and phytol. The overlapping ratio of peaks (ORP of the chromatogram in the seven Dayi Pu-erh tea samples was greater than 89.55%, whereas the ORP of Ya'an tea samples was less than 79.10%. The similarity and differences of the Dayi Pu-erh tea samples were also characterized using correlation coefficient similarity and principal component analysis (PCA. The results showed that the correlation coefficient of similarity of the seven Dayi Pu-erh tea samples was greater than 0.820 and was gathered in a specific area, which showed that samples from different brands were basically the same, despite have some slightly differences of chemical indexes was found. These results showed that the GC-MS fingerprint combined with the PCA approach can be used as an effective tool for the quality assessment and control of Pu-erh tea.

  11. Development of SPME-LC-MS method for screening of eight beta-blockers and bronchodilators in plasma and urine samples.

    Science.gov (United States)

    Goryński, Krzysztof; Kiedrowicz, Alicja; Bojko, Barbara

    2016-08-05

    The current work describes the development and validation of a simple, efficient, and fast method using solid phase microextraction coupled to liquid chromatography-tandem mass spectrometry (SPME-LC-MS/MS) for the concomitant measurement of eight beta-blockers and bronchodilators in plasma and urine. The presented assay enables quantitative determination of acebutolol, atenolol, fenoterol, nadolol, pindolol, procaterol, sotalol, and timolol. In this work, samples were prepared on a high-throughput platform using the 96-well plate format of the thin film solid phase microextraction (TFME) system, and a biocompatible extraction phase made of hydrophilic-lipophilic balance particles. Analytes were separated on a pentafluorophenyl column (100mm×2.1mm, 3μm) by gradient elution using an UPLC Nexera coupled with an LCMS-8060 mass spectrometer. The mobile phase consisted of water-acetonitrile (0.1% formic acid) at a flow rate of 0.4mLmin(-1). The linearity of the method was checked within therapeutic blood-plasma concentrations, and shown to adequately reflect typically expected concentrations of future study samples. Post-extraction addition experiments showed that the matrix effect ranged in plasma from 98% for procaterol to 115% for nadolol, and in urine, from 85% for nadolol and pindolol to 119% for atenolol. The method was successfully validated using Food and Drug Administration (FDA) guidelines, and met all acceptance criteria for bioanalytical assays at five concentration levels for all selected drugs. The final protocol can be successfully applied for monitoring concentrations of the selected drugs in both plasma and urine matrices obtained from patients or athletes. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Simultaneous determination of salicylic, 3-methyl salicylic, 4-methyl salicylic, acetylsalicylic and benzoic acids in fruit, vegetables and derived beverages by SPME-LC-UV/DAD.

    Science.gov (United States)

    Aresta, Antonella; Zambonin, Carlo

    2016-03-20

    Salicylic and benzoic acid are phenolic acids occurring in plant cells, thus they can be present in fruit and vegetables at various levels. They possess anti-inflammatory and antimicrobial properties, however they may induce symptoms and health problems in a small percentage of the population. Therefore, a low phenolic acid diet may be of clinical benefit to such individuals. In order to achieve this goal, the concentration of these substances in different food and beverages should be assessed. The present work describes for the first time a new method, based on solid phase microextraction (polydimethylsiloxane-divinylbenzene fiber) coupled to liquid chromatography with UV diode array detection, for the simultaneous determination of salicylic acid, 3-methyl salicylic acid, 4-methyl salicylic acid, acetylsalicylic acid and benzoic acid in selected fruit, vegetables and beverages. All the aspects influencing fiber adsorption (time, temperature, pH, salt addition) and desorption (desorption and injection time, desorption solvent mixture composition) of the analytes have been investigated. An isocratic separation was performed using an acetonitrile-phosphate buffer (pH 2.8; 2 mM) mixture (70:30, v/v) as the mobile phase. The estimated LOD and LOQ values (μg/mL) were in the range 0.002-0.028 and 0.007-0.095. The within-day and day-to-day precision values (RSD%) were between 4.7-6.1 and 6.6-9.4, respectively. The method has been successfully applied to the analysis of fava beans, blueberries, kiwi, tangerines, lemons, oranges and fruit juice (lemon and blueberry) samples. The major advantage of the method is that it only requires simple homogenization and/or centrifugation and dilution steps prior to SPME and injection in the LC system. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Volatile Compound Profiling by HS-SPME/GC-MS-FID of a Core Olive Cultivar Collection as a Tool for Aroma Improvement of Virgin Olive Oil.

    Science.gov (United States)

    García-Vico, Lourdes; Belaj, Angjelina; Sánchez-Ortiz, Araceli; Martínez-Rivas, José M; Pérez, Ana G; Sanz, Carlos

    2017-01-14

    Virgin olive oil (VOO) is the only food product requiring official sensory analysis to be classified in commercial categories, in which the evaluation of the aroma plays a very important role. The selection of parents, with the aim of obtaining new cultivars with improved oil aroma, is of paramount importance in olive breeding programs. We have assessed the volatile fraction by headspace-solid-phase microextraction/gas chromatography-mass spectrometry-flame ionization detection (HS-SPME/GC-MS-FID) and the deduced aroma properties of VOO from a core set of olive cultivars (Core-36) which possesses most of the genetic diversity found in the World Olive Germplasm Collection (IFAPA Alameda del Obispo) located in Cordoba, Spain. The VOO volatile fractions of Core-36 cultivars display a high level of variability. It is mostly made of compounds produced from polyunsaturated fatty acids through the lipoxygenase pathway, which confirms to be a general characteristic of the olive species ( Olea europaea L.). The main group of volatile compounds in the oils was six straight-chain carbon compounds derived from linolenic acid, some of them being the main contributors to the aroma of the olive oils according to their odor activity values (OAV). The high level of variability found for the volatile fraction of the oils from Core-36 and, therefore, for the aroma odor notes, suggest that this core set may be a very useful tool for the choice of optimal parents in olive breeding programs in order to raise new cultivars with improved VOO aroma.

  14. Investigation of a Quantitative Method for the Analysis of Chiral Monoterpenes in White Wine by HS-SPME-MDGC-MS of Different Wine Matrices

    Directory of Open Access Journals (Sweden)

    Mei Song

    2015-04-01

    Full Text Available A valid quantitative method for the analysis of chiral monoterpenes in white wine using head-space solid phase micro-extraction-MDGC-MS (HS-SPME-MDGC-MS with stable isotope dilution analysis was established. Fifteen compounds: (S-(−-limonene, (R-(+-limonene, (+-(2R,4S-cis-rose oxide, (−-(2S,4R-cis-rose oxide, (−-(2R,4R-trans-rose oxide, (+-(2S,4S-cis-rose oxide, furanoid (+-trans-linalool oxide, furanoid (−-cis-linalool oxide, furanoid (−-trans-linalool oxide, furanoid (+-cis-linalool oxide, (−-linalool, (+-linalool, (−-α-terpineol, (+-α-terpineol and (R-(+-β-citronellol were quantified. Two calibration curves were plotted for different wine bases, with varying residual sugar content, and three calibration curves for each wine base were investigated during a single fiber’s lifetime. This was needed as both sugar content and fiber life impacted the quantification of the chiral terpenes. The chiral monoterpene content of six Pinot Gris wines and six Riesling wines was then analyzed using the verified method. ANOVA with Tukey multiple comparisons showed significant differences for each of the detected chiral compounds in all 12 wines. PCA score plots showed a clear separation between the Riesling and Pinot Gris wines. Riesling wines had greater number of chiral terpenes in comparison to Pinot Gris wines. Beyond total terpene content it is possible that the differences in chiral terpene content may be driving the aromatic differences in white wines.

  15. Characterization of fish sauce aroma-impact compounds using GC-MS, SPME-Osme-GCO, and Stevens' power law exponents.

    Science.gov (United States)

    Pham, A J; Schilling, M W; Yoon, Y; Kamadia, V V; Marshall, D L

    2008-05-01

    The objectives of this study were to characterize volatile compounds and to determine the characteristic aromas associated with impact compounds in 4 fish sauces using solid-phase micro-extraction, gas chromatography-mass spectrometry, Osme, and gas chromatography olfactometry (SPME-Osme-GCO) coupled with Stevens' Power Law. Compounds were separated using GCMS and GCO and were identified with the mass spectral database, aroma perceived at the sniffing port, retention indices, and verification of compounds by authentic standards in the GCMS and GCO. Aromas that were isolated and present in all 4 fish sauce samples at all concentrations included fishy (trimethylamine), pungent and dirty socks (combination of butanoic, pentanoic, hexanoic, and heptanoic acids), cooked rice and buttery popcorn (2,6-dimethyl pyrazine), and sweet and cotton candy (benzaldehyde). All fish sauces contained the same aromas as determined by GCO and GCMS (verified using authentic standard compounds), but the odor intensity associated with each compound or group of compounds was variable for different fish sauce samples. Stevens' Power Law exponents were also determined using this analytical technique, but exponents were not consistent for the same compounds that were found in all fish sauces. Stevens' Power Law exponents ranged from 0.14 to 0.37, 0.24 to 0.34, 0.09 to 0.21, and 0.10 to 0.35 for dirty socks, fishy, buttery popcorn, and sweet aromas, respectively. This demonstrates that there is variability in Stevens' Power Law exponents for odorants within fish sauce samples.

  16. Volatile compound changes during shelf life of dried Boletus edulis: comparison between SPME-GC-MS and PTR-ToF-MS analysis.

    Science.gov (United States)

    Aprea, Eugenio; Romano, Andrea; Betta, Emanuela; Biasioli, Franco; Cappellin, Luca; Fanti, Marco; Gasperi, Flavia

    2015-01-01

    Drying process is commonly used to allow long time storage of valuable porcini mushrooms (Boletus edulis). Although considered a stable product dried porcini flavour changes during storage. Monitoring of volatile compounds during shelf life may help to understand the nature of the observed changes. In the present work two mass spectrometric techniques were used to monitor the evolution of volatile compounds during commercial shelf life of dried porcini. Solid phase microextraction (SPME) coupled to gas chromatography - mass spectrometry (GC-MS) allowed the identification of 66 volatile compounds, 36 of which reported for the first time, monitored during the commercial shelf life of dried porcini. Proton transfer reaction - time of flight - mass spectrometry (PTR-ToF-MS) , a direct injection mass spectrometric technique, was shown to be a fast and sensitive instrument for the general monitoring of volatile compound evolution during storage of dried porcini. Furthermore, PTR-ToF-MS grants access to compounds whose determination would otherwise require lengthy pre-concentration and/or derivatization steps such as ammonia and small volatile amines. The two techniques, both used for the first time to study dried porcini, provided detailed description of time evolution of volatile compounds during shelf life. Alcohols, aldehydes, ketones and monoterpenes diminish during the storage while carboxylic acids, pyrazines, lactones and amines increase. The storage temperature modifies the rate of the observed changes influencing the final quality of the dried porcini. We showed the advantages of both techniques, suggesting a strategy to be adopted to follow time evolution of volatile compounds in food products during shelf life, based on the identification of compounds by GC-MS and the rapid time monitoring by PTR-ToF-MS measurements in order to maximize the advantages of both techniques. Copyright © 2015 John Wiley & Sons, Ltd.

  17. Tequila authenticity assessment by headspace SPME-HRGC-IRMS analysis of 13C/12C and 18O/16O ratios of ethanol.

    Science.gov (United States)

    Aguilar-Cisneros, Blanca O; López, Mercedes G; Richling, Elke; Heckel, Frank; Schreier, Peter

    2002-12-18

    By use of headspace SPME sampling and a PLOT column, on-line capillary gas chromatography-isotope ratio mass spectrometry was employed in the combustion (C) and the pyrolysis (P) modes (HRGC-C/P-IRMS) to determine the delta(13)C(VPDB) and delta(18)O(VSMOW) values of ethanol in authentic (n = 14) and commercial tequila samples (n = 15) as well as a number of other spirits (n = 23). Whereas with delta(13)C(VPDB) values ranging from -12.1 to -13.2 per thousand and from -12.5 to -14.8 per thousand similar variations were found for 100% agave and mixed tequilas, respectively, the delta(18)O(VSMOW) data differed slightly within these categories: ranges from +22.1 to +22.8 per thousand and +20.8 to +21.7 per thousand were determined for both the authentic 100% agave and mixed products, respectively. The data recorded for commercial tequilas were less homogeneous; delta(13)C(VPDB) data from -10.6 to -13.9 per thousand and delta(18)O(VSMOW) values from +15.5 to +22.7 per thousand were determined in tequilas of both categories. Owing to overlapping data, attempts to differentiate between white, rested, and aged tequilas within each of the two categories failed. In addition, discrimination of tequila samples from other spirits by means of delta(13)C(VPDB) and delta(18)O(VSMOW) data of ethanol was restricted to the products originating from C(3) as well as C(4)/CAM raw materials.

  18. NMR investigation of acrolein stability in hydroalcoholic solution as a foundation for the valid HS-SPME/GC-MS quantification of the unsaturated aldehyde in beverages.

    Science.gov (United States)

    Kächele, Martin; Monakhova, Yulia B; Kuballa, Thomas; Lachenmeier, Dirk W

    2014-04-11

    Acrolein (propenal) is found in many foods and beverages and may pose a health hazard due to its cytotoxicity. Considerable knowledge gaps regarding human exposure to acrolein exist, and there is a lack of reliable analytical methods. Hydroalcoholic dilutions prepared for calibration purposes from pure acrolein show considerable degradation of the compound and nuclear magnetic resonance (NMR) spectroscopy showed that 1,3,3-propanetriol and 3-hydroxypropionaldehyde are formed. The degradation can be prevented by addition of hydroquinone as stabilizer to the calibration solutions, which then show linear concentration-response behaviour required for quantitative analysis. The stabilized calibration solutions were used for quantitative headspace solid-phase microextraction/gas chromatography-mass spectrometry (HS-SPME/GC-MS) determination of acrolein in alcoholic beverages with a detection limit of 14 μg L(-1). Of 117 tested alcoholic beverages, 64 were tested positive with the highest incidence in grape marc spirits and whiskey (100%, mean 252 μg L(-1)), followed by fruit spirits (86%, mean 591 μg/L(-1)), tequila (86%, mean 404 μg L(-1)), Asian spirits (43%, mean 54 μg L(-1)) and wine (9%, mean 0.7 μg L(-1)). Acrolein could not be detected in beer, vodka, absinthe and bottled water. Six of the fruit and grape marc spirits had acrolein levels above the World Health Organization (WHO) provisional tolerable concentration of 1.5 mg L(-1). Copyright © 2014 Elsevier B.V. All rights reserved.

  19. Optimization of an analytical methodology for the determination of alkyl- and methoxy-phenolic compounds by HS-SPME in biomass smoke

    Energy Technology Data Exchange (ETDEWEB)

    Conde, Francisco J.; Afonso, Ana M.; Gonzalez, Venerando; Ayala, Juan H. [University of La Laguna, Campus de Anchieta, Department of Analytical Chemistry, Nutrition and Food Science, La Laguna (Spain)

    2006-08-15

    A sampling and analysis method for the determination of 21 phenolic compounds in smoke samples from biomass combustion has been developed. The smoke is used to make smoked foods, following an artisanal procedure used in some parts of the Canary Islands. The sampling system consists of a Bravo H air sampler, two impingers, each one containing an aqueous solution of sodium hydroxide 0.1 mol L{sup -1}, followed by a silica gel trap. The variables optimized to reach the best sampling conditions were volume of absorbent solution and sampling flow. Under the optimum conditions, 100 mL of absorbent solution of NaOH 0.10 mol L{sup -1} and 2 L min{sup -1} for the sampling flow, sampling efficiencies are higher than 80%. Analysis of phenolic compounds was carried out by headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography-mass spectrometry (GC-MS). Five different fiber coatings were employed in this study. By means of a central composite design, extraction time, salt concentration, and pH of the solution were optimized: 65-{mu}m carbowax-divinylbenzene, extraction time 90 min, concentration in NaCl of 35% (m/v), and pH 2 yielded the highest response. Detection limits of phenol and their alkyl derivatives, guaiacol and eugenol, are between 1.13 and 4.60 ng mL{sup -1}. 3-Methoxyphenol, 2,6-dimethoxyphenol, and vanillin have detection limits considerably higher. Good linearity (R {sup 2}{>=}0.98) was observed for all calibration curves in the established ranges. The reproducibility of the method (RSD, relative standard deviation) was found to oscillate between 7 and 18% (generally close or lower than 10%). (orig.)

  20. Detection of DDT and its metabolites in two estuaries of South China using a SPME-based device: First report of p,p'-DDMU in water column

    International Nuclear Information System (INIS)

    Xing Yuanna; Guo Ying; Xie Mei; Shen Rulang; Zeng, Eddy Y.

    2009-01-01

    A solid-phase microextration-based sampling method was employed to determine the concentrations of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and its metabolites, 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (DDD), 1,1-dichloro-2,2-bis(p-chlorophenyl)ethene (DDE) and 1-chloro-2,2-bis(p-chlorophenyl)ethene (DDMU), in two estuarine bays, Daya Bay and Hailing Bay, of South China. Six DDT components including p,p'-DDT, o,p'-DDD, p,p'-DDD, o,p'-DDE, p,p'-DDE, and p,p'-DDMU were detected in Hailing Bay, while only p,p'-DDD was found in Daya Bay. p,p'-DDD was the most abundant DDT component in both bays, sharply different from the previous finding in the water column of the Palos Verdes Shelf, California, USA that p,p'-DDE was prevalent. In addition, the occurrence of p,p'-DDMU (with a range of 0.047-0.21 ng/L in Hailing Bay) has not been reported around the globe, and its presence in our study region appeared to stem from dehydrochlorination of p,p'-DDD, favored under aerobic conditions, but further investigations are clearly needed to confirm the mechanism for generation of DDMU in estuarine environments. - DDT and its metabolites, particularly p,p'-DDMU, are detected in the water column of two estuarine bays in South China using a SPME-based sampler

  1. Robust synthesis for real-time systems

    DEFF Research Database (Denmark)

    Larsen, Kim Guldstrand; Legay, Axel; Traonouez, Luois-Marie

    2014-01-01

    Specification theories for real-time systems allow reasoning about interfaces and their implementation models, using a set of operators that includes satisfaction, refinement, logical and parallel composition. To make such theories applicable throughout the entire design process from an abstract...... of introducing small perturbations into formal models. We address this problem of robust implementations in timed specification theories. We first consider a fixed perturbation and study the robustness of timed specifications with respect to the operators of the theory. To this end we synthesize robust...... specification to an implementation, we need to reason about the possibility to effectively implement the theoretical specifications on physical systems, despite their limited precision. In the literature, this implementation problem has been linked to the robustness problem that analyzes the consequences...

  2. Robust adaptive synchronization of general dynamical networks ...

    Indian Academy of Sciences (India)

    Robust adaptive synchronization; dynamical network; multiple delays; multiple uncertainties. ... Networks such as neural networks, communication transmission networks, social rela- tionship networks etc. ..... a very good effect. Pramana – J.

  3. Technical Challenges Hindering Development of Robust Wireless ...

    African Journals Online (AJOL)

    PROF. OLIVER OSUAGWA

    2015-12-01

    Dec 1, 2015 ... challenges remain to be resolved, in designing robust wireless networks that can deliver the performance ... demonstrated the first radio transmission from the Isle of ... distances with better quality, less power, and smaller ...

  4. Multifidelity Robust Aeroelastic Design, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Nielsen Engineering & Research (NEAR) proposes a new method to generate mathematical models of wind-tunnel models and flight vehicles for robust aeroelastic...

  5. The structural robustness of multiprocessor computing system

    Directory of Open Access Journals (Sweden)

    N. Andronaty

    1996-03-01

    Full Text Available The model of the multiprocessor computing system on the base of transputers which permits to resolve the question of valuation of a structural robustness (viability, survivability is described.

  6. Design principles for robust oscillatory behavior.

    Science.gov (United States)

    Castillo-Hair, Sebastian M; Villota, Elizabeth R; Coronado, Alberto M

    2015-09-01

    Oscillatory responses are ubiquitous in regulatory networks of living organisms, a fact that has led to extensive efforts to study and replicate the circuits involved. However, to date, design principles that underlie the robustness of natural oscillators are not completely known. Here we study a three-component enzymatic network model in order to determine the topological requirements for robust oscillation. First, by simulating every possible topological arrangement and varying their parameter values, we demonstrate that robust oscillators can be obtained by augmenting the number of both negative feedback loops and positive autoregulations while maintaining an appropriate balance of positive and negative interactions. We then identify network motifs, whose presence in more complex topologies is a necessary condition for obtaining oscillatory responses. Finally, we pinpoint a series of simple architectural patterns that progressively render more robust oscillators. Together, these findings can help in the design of more reliable synthetic biomolecular networks and may also have implications in the understanding of other oscillatory systems.

  7. Robust and Efficient Parametric Face Alignment

    NARCIS (Netherlands)

    Tzimiropoulos, Georgios; Zafeiriou, Stefanos; Pantic, Maja

    2011-01-01

    We propose a correlation-based approach to parametric object alignment particularly suitable for face analysis applications which require efficiency and robustness against occlusions and illumination changes. Our algorithm registers two images by iteratively maximizing their correlation coefficient

  8. Framework for Robustness Assessment of Timber Structures

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard

    2011-01-01

    This paper presents a theoretical framework for the design and analysis of robustness of timber structures. This is actualized by a more4 frequent use of advanced types of timber structures with limited redundancy and serious consequences in the case of failure. Combined with increased requirements...... to efficiency in design and execution followed by increased risk of human errors has made the need of requirements to robustness of new structures essential. Further, the collapse of the Ballerup Super Arena, the bad Reichenhall Ice-Arena and a number of other structural systems during the last 10 years has...... increased the interest in robustness. Typically, modern structural design codes require that ‘the consequence of damages to structures should not be disproportional to the causes of the damages’. However, although the importance of robustness for structural design is widely recognized, the code requirements...

  9. Robust Analysis and Design of Multivariable Systems

    National Research Council Canada - National Science Library

    Tannenbaum, Allen

    1998-01-01

    In this Final Report, we will describe the work we have performed in robust control theory and nonlinear control, and the utilization of techniques in image processing and computer vision for problems in visual tracking...

  10. Robust Tracking Control for a Piezoelectric Actuator

    National Research Council Canada - National Science Library

    Salah, M; McIntyre, M; Dawson, D; Wagner, J

    2006-01-01

    In this paper, a hysteresis model-based nonlinear robust controller is developed for a piezoelectric actuator, utilizing a Lyapunov-based stability analysis, which ensures that a desired displacement...

  11. Robustness studies on coal gasification process variables

    African Journals Online (AJOL)

    coal before feeding to the gasification process [1]. .... to-control variables will make up the terms in the response surface model for the ... Montgomery (1999) explained that all the Taguchi engineering objectives for a robust ..... software [3].

  12. Antecedents and Dimensions of Supply Chain Robustness

    OpenAIRE

    Durach, Christian F.; Wieland, Andreas; Machuca, Jose A.D.

    2015-01-01

    Purpose – The purpose of this paper is to provide groundwork for an emerging theory of supply chain robustness – which has been conceptualized as a dimension of supply chain resilience – through reviewing and synthesizing related yet disconnected studies. The paper develops a formal definition of supply chain robustness to build a framework that captures the dimensions, antecedents and moderators of the construct as discussed in the literature. Design/methodology/approach – The...

  13. A Unifying Mathematical Framework for Genetic Robustness, Environmental Robustness, Network Robustness and their Trade-offs on Phenotype Robustness in Biological Networks. Part III: Synthetic Gene Networks in Synthetic Biology

    Science.gov (United States)

    Chen, Bor-Sen; Lin, Ying-Po

    2013-01-01

    Robust stabilization and environmental disturbance attenuation are ubiquitous systematic properties that are observed in biological systems at many different levels. The underlying principles for robust stabilization and environmental disturbance attenuation are universal to both complex biological systems and sophisticated engineering systems. In many biological networks, network robustness should be large enough to confer: intrinsic robustness for tolerating intrinsic parameter fluctuations; genetic robustness for buffering genetic variations; and environmental robustness for resisting environmental disturbances. Network robustness is needed so phenotype stability of biological network can be maintained, guaranteeing phenotype robustness. Synthetic biology is foreseen to have important applications in biotechnology and medicine; it is expected to contribute significantly to a better understanding of functioning of complex biological systems. This paper presents a unifying mathematical framework for investigating the principles of both robust stabilization and environmental disturbance attenuation for synthetic gene networks in synthetic biology. Further, from the unifying mathematical framework, we found that the phenotype robustness criterion for synthetic gene networks is the following: if intrinsic robustness + genetic robustness + environmental robustness ≦ network robustness, then the phenotype robustness can be maintained in spite of intrinsic parameter fluctuations, genetic variations, and environmental disturbances. Therefore, the trade-offs between intrinsic robustness, genetic robustness, environmental robustness, and network robustness in synthetic biology can also be investigated through corresponding phenotype robustness criteria from the systematic point of view. Finally, a robust synthetic design that involves network evolution algorithms with desired behavior under intrinsic parameter fluctuations, genetic variations, and environmental

  14. Field-based Evaluation of a Novel SPME-GC-MS Method for Investigation of Below-ground Interaction between Brassica Roots and Larvae of Cabbage Root Fly, Delia radicum L.

    Science.gov (United States)

    Deasy, William; Shepherd, Tom; Alexander, Colin J; Birch, A Nicholas E; Evans, K Andrew

    2016-11-01

    Collection of volatiles from plant roots poses technical challenges due to difficulties accessing the soil environment without damaging the roots. To validate a new non-invasive method for passive sampling of root volatiles in situ, from plants grown under field conditions, using solid phase micro-extraction (SPME). SPME fibres were inserted into perforated polytetrafluoroethene (PTFE) tubes positioned in the soil next to broccoli plants for collection of root volatiles pre- and post-infestation with Delia radicum larvae. After sample analysis by gas chromatography-mass spectrometry (GC-MS), principal component analysis (PCA) was applied to determine differences in the profiles of volatiles between samples. GC-MS analysis revealed that this method can detect temporal changes in root volatiles emitted before and after Delia radicum damage. PCA showed that samples collected pre- and post-infestation were compositionally different due to the presence of root volatiles induced by D. radicum feeding. Sulphur containing compounds, in particular, accounted for the differences observed. Root volatiles emission patterns post-infestation are thought to follow the feeding and developmental progress of larvae. This study shows that volatiles released by broccoli roots can be collected in situ using SPME fibres within perforated PTFE tubes under field conditions. Plants damaged by Delia radicum larvae could be distinguished from plants sampled pre-infestation and soil controls on the basis of larval feeding-induced sulphur-containing volatiles. These results show that this new method is a powerful tool for non-invasive sampling of root volatiles below-ground. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  15. Sampling and analytical procedures for the determination of VOCs released into air from natural and anthropogenic sources: A comparison between SPME (Solid Phase Micro Extraction) and ST (Solid Trap) methods

    International Nuclear Information System (INIS)

    Tassi, F.; Capecchiacci, F.; Buccianti, A.; Vaselli, O.

    2012-01-01

    In the present study, two sampling and analytical methods for VOC determination in fumarolic exhalations related to hydrothermal-magmatic reservoirs in volcanic and geothermal areas and biogas released from waste landfills were compared: (a) Solid Traps (STs), consisting of three phase (Carboxen B, Carboxen C and Carbosieve S111) absorbent stainless steel tubes and (b) Solid Phase Micro Extraction (SPME) fibers, composed of DiVinylBenzene (DVB), Carboxen and PolyDimethylSiloxane. These techniques were applied to pre-concentrate VOCs discharged from: (i) low-to-high temperature fumaroles collected at Vulcano Island, Phlegrean Fields (Italy), and Nisyros Island (Greece), (ii) recovery wells in a solid waste disposal site located near Florence (Italy). A glass condensing system cooled with water was used to collect the dry fraction of the fumarolic gases, in order to allow more efficient VOC absorption avoiding any interference by water vapor and acidic gases, such as SO 2 , H 2 S, HF and HCl, typically present at relatively high concentrations in these fluids. Up to 37 organic species, in the range of 40–400 m/z, were determined by coupling gas chromatography to mass spectrometry (GC–MS). This study shows that the VOC compositions of fumaroles and biogas determined via SPME and ST are largely consistent and can be applied to the analysis of VOCs in gases released from different natural and anthropogenic environments. The SPME method is rapid and simple and more appropriate for volcanic and geothermal emissions, where VOCs are present at relatively high concentrations and prolonged gas sampling may be hazardous for the operator. The ST method, allowing the collection of large quantities of sample, is to be preferred to analyze the VOC composition of fluids from diffuse emissions and air, where these compounds are present at relatively low concentrations.

  16. Adaptive Critic Nonlinear Robust Control: A Survey.

    Science.gov (United States)

    Wang, Ding; He, Haibo; Liu, Derong

    2017-10-01

    Adaptive dynamic programming (ADP) and reinforcement learning are quite relevant to each other when performing intelligent optimization. They are both regarded as promising methods involving important components of evaluation and improvement, at the background of information technology, such as artificial intelligence, big data, and deep learning. Although great progresses have been achieved and surveyed when addressing nonlinear optimal control problems, the research on robustness of ADP-based control strategies under uncertain environment has not been fully summarized. Hence, this survey reviews the recent main results of adaptive-critic-based robust control design of continuous-time nonlinear systems. The ADP-based nonlinear optimal regulation is reviewed, followed by robust stabilization of nonlinear systems with matched uncertainties, guaranteed cost control design of unmatched plants, and decentralized stabilization of interconnected systems. Additionally, further comprehensive discussions are presented, including event-based robust control design, improvement of the critic learning rule, nonlinear H ∞ control design, and several notes on future perspectives. By applying the ADP-based optimal and robust control methods to a practical power system and an overhead crane plant, two typical examples are provided to verify the effectiveness of theoretical results. Overall, this survey is beneficial to promote the development of adaptive critic control methods with robustness guarantee and the construction of higher level intelligent systems.

  17. Aplicação de SPME (Solid Phase Micro-Extraction na análise de águas potáveis de três localidades do estado de São Paulo

    Directory of Open Access Journals (Sweden)

    Valente Antonio Luiz Pires

    1998-01-01

    Full Text Available The technique of solid phase microextraction (SPME was used for the extraction of halogenated contaminants of water samples from three cities of the State of São Paulo and the extracts were submitted to gas chromatographic analysis with electron capture detection (GC-ECD. In the samples of water collected at the city of São Paulo the detected level of trihalomethanes (THM expressed as the sum of chloroform, dibromochloromethane and dichlorobromomethane, were higher than the permissible limit established by the Brazilian regulation. In the samples collected at the two other cities the level of any of the three THM remained below the sensitivity of the ECD.

  18. Determinação de pesticidas organofosforados em água usando microextração em fase sólida e CGAR-EM Determination of organophosphorus pesticides in water using SPME-GC-MS

    Directory of Open Access Journals (Sweden)

    Fernando Carvalho Silva

    1999-04-01

    Full Text Available Solid-phase microextraction (SPME has been applied to direct extraction of 11 organophosphorus pesticides in water using a 100 mm fiber polydimethylsiloxane. The method was evaluated with respect time of exposure, detection limits (LODs, linearity and precision. The detection limits (S/N = 3 depend of each pesticide and varie about ng/L levels. The linearity was satisfactory with coefficients of correlation usually greater than 0.993. The precision of the method was determined by extraction from 4.0 mg/L aqueous standard with coefficients of variation between 5.7 to 17.2%.

  19. Extração em fase sólida (SPE e micro extração em fase sólida (SPME de piretróides em água Solid-phase extraction (SPE and solid-phase microextraction of pyrethroids in water

    Directory of Open Access Journals (Sweden)

    Wilma Regina Barrionuevo

    2001-04-01

    Full Text Available The pyrethroids bifenthrin, permethrin, cypermethrin and deltamethrin were extracted by solid phase extraction (SPE and solid phase microextraction (SPME. The analysis were performed on a gas chromatograph with electron capture detection (GC-ECD. Octadecil Silano-C18, Florisil and Silica stationary phases were studied for SPE. Better results were obtained for Florisil which gave recoveries from 80% to 108%. Pyrethroids extraction by SPME showed a linear response and a detection limit of 10 pg ml-1. Although the data showed that the two extraction methods were able to isolate the pesticide residues from water samples, the best results were obtained by using SPME which is more sensitive, faster, cheeper, being a more useful technique for the analysis of pyrethroids in drinking water.

  20. Measure of robustness for complex networks

    Science.gov (United States)

    Youssef, Mina Nabil

    Critical infrastructures are repeatedly attacked by external triggers causing tremendous amount of damages. Any infrastructure can be studied using the powerful theory of complex networks. A complex network is composed of extremely large number of different elements that exchange commodities providing significant services. The main functions of complex networks can be damaged by different types of attacks and failures that degrade the network performance. These attacks and failures are considered as disturbing dynamics, such as the spread of viruses in computer networks, the spread of epidemics in social networks, and the cascading failures in power grids. Depending on the network structure and the attack strength, every network differently suffers damages and performance degradation. Hence, quantifying the robustness of complex networks becomes an essential task. In this dissertation, new metrics are introduced to measure the robustness of technological and social networks with respect to the spread of epidemics, and the robustness of power grids with respect to cascading failures. First, we introduce a new metric called the Viral Conductance (VCSIS ) to assess the robustness of networks with respect to the spread of epidemics that are modeled through the susceptible/infected/susceptible (SIS) epidemic approach. In contrast to assessing the robustness of networks based on a classical metric, the epidemic threshold, the new metric integrates the fraction of infected nodes at steady state for all possible effective infection strengths. Through examples, VCSIS provides more insights about the robustness of networks than the epidemic threshold. In addition, both the paradoxical robustness of Barabasi-Albert preferential attachment networks and the effect of the topology on the steady state infection are studied, to show the importance of quantifying the robustness of networks. Second, a new metric VCSIR is introduced to assess the robustness of networks with respect

  1. A Comparative Theoretical and Computational Study on Robust Counterpart Optimization: I. Robust Linear Optimization and Robust Mixed Integer Linear Optimization

    Science.gov (United States)

    Li, Zukui; Ding, Ran; Floudas, Christodoulos A.

    2011-01-01

    Robust counterpart optimization techniques for linear optimization and mixed integer linear optimization problems are studied in this paper. Different uncertainty sets, including those studied in literature (i.e., interval set; combined interval and ellipsoidal set; combined interval and polyhedral set) and new ones (i.e., adjustable box; pure ellipsoidal; pure polyhedral; combined interval, ellipsoidal, and polyhedral set) are studied in this work and their geometric relationship is discussed. For uncertainty in the left hand side, right hand side, and objective function of the optimization problems, robust counterpart optimization formulations induced by those different uncertainty sets are derived. Numerical studies are performed to compare the solutions of the robust counterpart optimization models and applications in refinery production planning and batch process scheduling problem are presented. PMID:21935263

  2. Robustness analysis of chiller sequencing control

    International Nuclear Information System (INIS)

    Liao, Yundan; Sun, Yongjun; Huang, Gongsheng

    2015-01-01

    Highlights: • Uncertainties with chiller sequencing control were systematically quantified. • Robustness of chiller sequencing control was systematically analyzed. • Different sequencing control strategies were sensitive to different uncertainties. • A numerical method was developed for easy selection of chiller sequencing control. - Abstract: Multiple-chiller plant is commonly employed in the heating, ventilating and air-conditioning system to increase operational feasibility and energy-efficiency under part load condition. In a multiple-chiller plant, chiller sequencing control plays a key role in achieving overall energy efficiency while not sacrifices the cooling sufficiency for indoor thermal comfort. Various sequencing control strategies have been developed and implemented in practice. Based on the observation that (i) uncertainty, which cannot be avoided in chiller sequencing control, has a significant impact on the control performance and may cause the control fail to achieve the expected control and/or energy performance; and (ii) in current literature few studies have systematically addressed this issue, this paper therefore presents a study on robustness analysis of chiller sequencing control in order to understand the robustness of various chiller sequencing control strategies under different types of uncertainty. Based on the robustness analysis, a simple and applicable method is developed to select the most robust control strategy for a given chiller plant in the presence of uncertainties, which will be verified using case studies

  3. Information theory perspective on network robustness

    International Nuclear Information System (INIS)

    Schieber, Tiago A.; Carpi, Laura; Frery, Alejandro C.; Rosso, Osvaldo A.; Pardalos, Panos M.; Ravetti, Martín G.

    2016-01-01

    A crucial challenge in network theory is the study of the robustness of a network when facing a sequence of failures. In this work, we propose a dynamical definition of network robustness based on Information Theory, that considers measurements of the structural changes caused by failures of the network's components. Failures are defined here as a temporal process defined in a sequence. Robustness is then evaluated by measuring dissimilarities between topologies after each time step of the sequence, providing a dynamical information about the topological damage. We thoroughly analyze the efficiency of the method in capturing small perturbations by considering different probability distributions on networks. In particular, we find that distributions based on distances are more consistent in capturing network structural deviations, as better reflect the consequences of the failures. Theoretical examples and real networks are used to study the performance of this methodology. - Highlights: • A novel methodology to measure the robustness of a network to component failure or targeted attacks is proposed. • The use of the network's distance PDF allows a precise analysis. • The method provides a dynamic robustness profile showing the response of the topology to each failure event. • The measure is capable to detect network's critical elements.

  4. On the robustness of Herlihy's hierarchy

    Science.gov (United States)

    Jayanti, Prasad

    1993-01-01

    A wait-free hierarchy maps object types to levels in Z(+) U (infinity) and has the following property: if a type T is at level N, and T' is an arbitrary type, then there is a wait-free implementation of an object of type T', for N processes, using only registers and objects of type T. The infinite hierarchy defined by Herlihy is an example of a wait-free hierarchy. A wait-free hierarchy is robust if it has the following property: if T is at level N, and S is a finite set of types belonging to levels N - 1 or lower, then there is no wait-free implementation of an object of type T, for N processes, using any number and any combination of objects belonging to the types in S. Robustness implies that there are no clever ways of combining weak shared objects to obtain stronger ones. Contrary to what many researchers believe, we prove that Herlihy's hierarchy is not robust. We then define some natural variants of Herlihy's hierarchy, which are also infinite wait-free hierarchies. With the exception of one, which is still open, these are not robust either. We conclude with the open question of whether non-trivial robust wait-free hierarchies exist.

  5. Replication and robustness in developmental research.

    Science.gov (United States)

    Duncan, Greg J; Engel, Mimi; Claessens, Amy; Dowsett, Chantelle J

    2014-11-01

    Replications and robustness checks are key elements of the scientific method and a staple in many disciplines. However, leading journals in developmental psychology rarely include explicit replications of prior research conducted by different investigators, and few require authors to establish in their articles or online appendices that their key results are robust across estimation methods, data sets, and demographic subgroups. This article makes the case for prioritizing both explicit replications and, especially, within-study robustness checks in developmental psychology. It provides evidence on variation in effect sizes in developmental studies and documents strikingly different replication and robustness-checking practices in a sample of journals in developmental psychology and a sister behavioral science-applied economics. Our goal is not to show that any one behavioral science has a monopoly on best practices, but rather to show how journals from a related discipline address vital concerns of replication and generalizability shared by all social and behavioral sciences. We provide recommendations for promoting graduate training in replication and robustness-checking methods and for editorial policies that encourage these practices. Although some of our recommendations may shift the form and substance of developmental research articles, we argue that they would generate considerable scientific benefits for the field. (PsycINFO Database Record (c) 2014 APA, all rights reserved).

  6. Emergence of robustness in networks of networks

    Science.gov (United States)

    Roth, Kevin; Morone, Flaviano; Min, Byungjoon; Makse, Hernán A.

    2017-06-01

    A model of interdependent networks of networks (NONs) was introduced recently [Proc. Natl. Acad. Sci. (USA) 114, 3849 (2017), 10.1073/pnas.1620808114] in the context of brain activation to identify the neural collective influencers in the brain NON. Here we investigate the emergence of robustness in such a model, and we develop an approach to derive an exact expression for the random percolation transition in Erdös-Rényi NONs of this kind. Analytical calculations are in agreement with numerical simulations, and highlight the robustness of the NON against random node failures, which thus presents a new robust universality class of NONs. The key aspect of this robust NON model is that a node can be activated even if it does not belong to the giant mutually connected component, thus allowing the NON to be built from below the percolation threshold, which is not possible in previous models of interdependent networks. Interestingly, the phase diagram of the model unveils particular patterns of interconnectivity for which the NON is most vulnerable, thereby marking the boundary above which the robustness of the system improves with increasing dependency connections.

  7. Primal and dual approaches to adjustable robust optimization

    NARCIS (Netherlands)

    de Ruiter, Frans

    2018-01-01

    Robust optimization has become an important paradigm to deal with optimization under uncertainty. Adjustable robust optimization is an extension that deals with multistage problems. This thesis starts with a short but comprehensive introduction to adjustable robust optimization. Then the two

  8. Robust Object Tracking Using Valid Fragments Selection.

    Science.gov (United States)

    Zheng, Jin; Li, Bo; Tian, Peng; Luo, Gang

    Local features are widely used in visual tracking to improve robustness in cases of partial occlusion, deformation and rotation. This paper proposes a local fragment-based object tracking algorithm. Unlike many existing fragment-based algorithms that allocate the weights to each fragment, this method firstly defines discrimination and uniqueness for local fragment, and builds an automatic pre-selection of useful fragments for tracking. Then, a Harris-SIFT filter is used to choose the current valid fragments, excluding occluded or highly deformed fragments. Based on those valid fragments, fragment-based color histogram provides a structured and effective description for the object. Finally, the object is tracked using a valid fragment template combining the displacement constraint and similarity of each valid fragment. The object template is updated by fusing feature similarity and valid fragments, which is scale-adaptive and robust to partial occlusion. The experimental results show that the proposed algorithm is accurate and robust in challenging scenarios.

  9. Occupant behaviour and robustness of building design

    DEFF Research Database (Denmark)

    Buso, Tiziana; Fabi, Valentina; Andersen, Rune Korsholm

    2015-01-01

    in a dynamic building energy simulation tool (IDA ICE). The analysis was carried out by simulating 15 building envelope designs in different thermal zones of an Office Reference Building in 3 climates: Stockholm, Frankfurt and Athens.In general, robustness towards changes in occupants' behaviour increased......Occupant behaviour can cause major discrepancies between the designed and the real total energy use in buildings. A possible solution to reduce the differences between predictions and actual performances is designing robust buildings, i.e. buildings whose performances show little variations...... with alternating occupant behaviour patterns. The aim of this work was to investigate how alternating occupant behaviour patterns impact the performance of different envelope design solutions in terms of building robustness. Probabilistic models of occupants' window opening and use of shading were implemented...

  10. Robust Mediation Analysis Based on Median Regression

    Science.gov (United States)

    Yuan, Ying; MacKinnon, David P.

    2014-01-01

    Mediation analysis has many applications in psychology and the social sciences. The most prevalent methods typically assume that the error distribution is normal and homoscedastic. However, this assumption may rarely be met in practice, which can affect the validity of the mediation analysis. To address this problem, we propose robust mediation analysis based on median regression. Our approach is robust to various departures from the assumption of homoscedasticity and normality, including heavy-tailed, skewed, contaminated, and heteroscedastic distributions. Simulation studies show that under these circumstances, the proposed method is more efficient and powerful than standard mediation analysis. We further extend the proposed robust method to multilevel mediation analysis, and demonstrate through simulation studies that the new approach outperforms the standard multilevel mediation analysis. We illustrate the proposed method using data from a program designed to increase reemployment and enhance mental health of job seekers. PMID:24079925

  11. Robustness of Distance-to-Default

    DEFF Research Database (Denmark)

    Jessen, Cathrine; Lando, David

    2013-01-01

    Distance-to-default is a remarkably robust measure for ranking firms according to their risk of default. The ranking seems to work despite the fact that the Merton model from which the measure is derived produces default probabilities that are far too small when applied to real data. We use...... simulations to investigate the robustness of the distance-to-default measure to different model specifications. Overall we find distance-to-default to be robust to a number of deviations from the simple Merton model that involve different asset value dynamics and different default triggering mechanisms....... A notable exception is a model with stochastic volatility of assets. In this case both the ranking of firms and the estimated default probabilities using distance-to-default perform significantly worse. We therefore propose a volatility adjustment of the distance-to-default measure, that significantly...

  12. Handling Occlusions for Robust Augmented Reality Systems

    Directory of Open Access Journals (Sweden)

    Maidi Madjid

    2010-01-01

    Full Text Available Abstract In Augmented Reality applications, the human perception is enhanced with computer-generated graphics. These graphics must be exactly registered to real objects in the scene and this requires an effective Augmented Reality system to track the user's viewpoint. In this paper, a robust tracking algorithm based on coded fiducials is presented. Square targets are identified and pose parameters are computed using a hybrid approach based on a direct method combined with the Kalman filter. An important factor for providing a robust Augmented Reality system is the correct handling of targets occlusions by real scene elements. To overcome tracking failure due to occlusions, we extend our method using an optical flow approach to track visible points and maintain virtual graphics overlaying when targets are not identified. Our proposed real-time algorithm is tested with different camera viewpoints under various image conditions and shows to be accurate and robust.

  13. Robust Portfolio Optimization using CAPM Approach

    Directory of Open Access Journals (Sweden)

    mohsen gharakhani

    2013-08-01

    Full Text Available In this paper, a new robust model of multi-period portfolio problem has been developed. One of the key concerns in any asset allocation problem is how to cope with uncertainty about future returns. There are some approaches in the literature for this purpose including stochastic programming and robust optimization. Applying these techniques to multi-period portfolio problem may increase the problem size in a way that the resulting model is intractable. In this paper, a novel approach has been proposed to formulate multi-period portfolio problem as an uncertain linear program assuming that asset return follows the single-index factor model. Robust optimization technique has been also used to solve the problem. In order to evaluate the performance of the proposed model, a numerical example has been applied using simulated data.

  14. Robustness of quantum correlations against linear noise

    International Nuclear Information System (INIS)

    Guo, Zhihua; Cao, Huaixin; Qu, Shixian

    2016-01-01

    Relative robustness of quantum correlations (RRoQC) of a bipartite state is firstly introduced relative to a classically correlated state. Robustness of quantum correlations (RoQC) of a bipartite state is then defined as the minimum of RRoQC of the state relative to all classically correlated ones. It is proved that as a function on quantum states, RoQC is nonnegative, lower semi-continuous and neither convex nor concave; especially, it is zero if and only if the state is classically correlated. Thus, RoQC not only quantifies the endurance of quantum correlations of a state against linear noise, but also can be used to distinguish between quantum and classically correlated states. Furthermore, the effects of local quantum channels on the robustness are explored and characterized. (paper)

  15. Parametric uncertainty modeling for robust control

    DEFF Research Database (Denmark)

    Rasmussen, K.H.; Jørgensen, Sten Bay

    1999-01-01

    The dynamic behaviour of a non-linear process can often be approximated with a time-varying linear model. In the presented methodology the dynamics is modeled non-conservatively as parametric uncertainty in linear lime invariant models. The obtained uncertainty description makes it possible...... to perform robustness analysis on a control system using the structured singular value. The idea behind the proposed method is to fit a rational function to the parameter variation. The parameter variation can then be expressed as a linear fractional transformation (LFT), It is discussed how the proposed...... point changes. It is shown that a diagonal PI control structure provides robust performance towards variations in feed flow rate or feed concentrations. However including both liquid and vapor flow delays robust performance specifications cannot be satisfied with this simple diagonal control structure...

  16. Incentive-Compatible Robust Line Planning

    Science.gov (United States)

    Bessas, Apostolos; Kontogiannis, Spyros; Zaroliagis, Christos

    The problem of robust line planning requests for a set of origin-destination paths (lines) along with their frequencies in an underlying railway network infrastructure, which are robust to fluctuations of real-time parameters of the solution. In this work, we investigate a variant of robust line planning stemming from recent regulations in the railway sector that introduce competition and free railway markets, and set up a new application scenario: there is a (potentially large) number of line operators that have their lines fixed and operate as competing entities issuing frequency requests, while the management of the infrastructure itself remains the responsibility of a single entity, the network operator. The line operators are typically unwilling to reveal their true incentives, while the network operator strives to ensure a fair (or socially optimal) usage of the infrastructure, e.g., by maximizing the (unknown to him) aggregate incentives of the line operators.

  17. Competition improves robustness against loss of information

    Directory of Open Access Journals (Sweden)

    Arash eKermani Kolankeh

    2015-03-01

    Full Text Available A substantial number of works aimed at modeling the receptive field properties of the primary visual cortex (V1. Their evaluation criterion is usually the similarity of the model response properties to the recorded responses from biological organisms. However, as several algorithms were able to demonstrate some degree of similarity to biological data based on the existing criteria, we focus on the robustness against loss of information in the form of occlusions as an additional constraint for better understanding the algorithmic level of early vision in the brain. We try to investigate the influence of competition mechanisms on the robustness. Therefore, we compared four methods employing different competition mechanisms, namely, independent component analysis, non-negative matrix factorization with sparseness constraint, predictive coding/biased competition, and a Hebbian neural network with lateral inhibitory connections. Each of those methods is known to be capable of developing receptive fields comparable to those of V1 simple-cells. Since measuring the robustness of methods having simple-cell like receptive fields against occlusion is difficult, we measure the robustness using the classification accuracy on the MNIST hand written digit dataset. For this we trained all methods on the training set of the MNIST hand written digits dataset and tested them on a MNIST test set with different levels of occlusions. We observe that methods which employ competitive mechanisms have higher robustness against loss of information. Also the kind of the competition mechanisms plays an important role in robustness. Global feedback inhibition as employed in predictive coding/biased competition has an advantage compared to local lateral inhibition learned by an anti-Hebb rule.

  18. Development of the HS-SPME-GC-MS/MS method for analysis of chemical warfare agent and their degradation products in environmental samples.

    Science.gov (United States)

    Nawała, Jakub; Czupryński, Krzysztof; Popiel, Stanisław; Dziedzic, Daniel; Bełdowski, Jacek

    2016-08-24

    After World War II approximately 50,000 tons of chemical weapons were dumped in the Baltic Sea by the Soviet Union under the provisions of the Potsdam Conference on Disarmament. These dumped chemical warfare agents still possess a major threat to the marine environment and to human life. Therefore, continue monitoring of these munitions is essential. In this work, we present the application of new solid phase microextraction fibers in analysis of chemical warfare agents and their degradation products. It can be concluded that the best fiber for analysis of sulfur mustard and its degradation products is butyl acrylate (BA), whereas for analysis of organoarsenic compounds and chloroacetophenone, the best fiber is a co-polymer of methyl acrylate and methyl methacrylate (MA/MMA). In order to achieve the lowest LOD and LOQ the samples should be divided into two subsamples. One of them should be analyzed using a BA fiber, and the second one using a MA/MMA fiber. When the fast analysis is required, the microextraction should be performed by use of a butyl acrylate fiber because the extraction efficiency of organoarsenic compounds for this fiber is acceptable. Next, we have elaborated of the HS-SPME-GC-MS/MS method for analysis of CWA degradation products in environmental samples using laboratory obtained fibers The analytical method for analysis of organosulfur and organoarsenic compounds was optimized and validated. The LOD's for all target chemicals were between 0.03 and 0.65 ppb. Then, the analytical method developed by us, was used for the analysis of sediment and pore water samples from the Baltic Sea. During these studies, 80 samples were analyzed. It was found that 25 sediments and 5 pore water samples contained CWA degradation products such as 1,4-dithiane, 1,4-oxathiane or triphenylarsine, the latter being a component of arsine oil. The obtained data is evidence that the CWAs present in the Baltic Sea have leaked into the general marine environment. Copyright

  19. New insight on biological interaction analysis: new nanocrystalline mixed metal oxide SPME fiber for GC-FID analysis of BTEX and its application in human hemoglobin-benzene interaction studies.

    Directory of Open Access Journals (Sweden)

    Reza Hosseinzadeh

    Full Text Available Nanocrystalline mixed metal oxides (MMO of various metal cations were synthesized and were used for coating a piece of copper wire as a new high sensitive solid phase micro extraction (SPME fiber in extraction and determination of BTEX compounds from the headspace of aqueous samples prior to GC-FID analysis. Under optimum extraction conditions, the proposed fiber exhibited low detection limits, and quantification limits, good reproducibility, simple and fast preparation method, high fiber capacity and high thermal and mechanical durability. These are some of the most important advantages of the new fiber. The proposed fiber was used for human hemoglobin upon interaction with benzene. Binding isotherm, Scatchard and Klotz logarithmic plots were constructed using HS-SPME-GC data, accurately. The obtained binding isotherm analyzed using Hill method. The Hill parameters have been obtained by calculating saturation parameter from the ratio of measured chromatographic peak areas in the presence and absence of hemoglobin. In this interaction, Hill coefficient and Hill constant determined as (nH = 6.14 and log KH = 6.47 respectively. These results reveal the cooperativity of hemoglobin upon interaction with benzene.

  20. The Use of Headspace Solid-Phase Microextraction (HS-SPME to Assess the Quality and Stability of Fruit Products: An Example Using Red Mombin Pulp (Spondias purpurea L.

    Directory of Open Access Journals (Sweden)

    Katieli Martins Todisco

    2014-10-01

    Full Text Available The present study aimed to evaluate the volatiles profile of red mombin (Spondias purpurea pulp and its powder produced by spray-drying (SD as an example to show utility of headspace solid-phase microextraction (HS-SPME in the analysis of parameters such as the quality and stability of fruit products. Volatiles profiles of the pulp were identified by gas chromatography-mass spectrometry (GC-MS, quantified by gas chromatography-flame ionization detector (GC-FID and compared to the profile of the powder stored at 0, 60 and 120 days in plastic (PP or laminated packages (LP. The results showed that the technique was able to identify 36 compounds in the red mombin pulp, 17 out of which have been described for the first time in this fruit, showing that red mombin fresh pulp appears to be unique in terms of volatiles composition. However, only 24 compounds were detected in the powder. This decrease is highly correlated (r2 = 0.99, at least for the majority of compounds, to the degree of volatility of compounds. Furthermore, the powder stored in PP or LP showed no statistical differences in the amounts of its components for a period of 120 days of storage. Finally, this work shows how HS-SPME analysis can be a valuable tool to assess the quality and stability of fruit products.

  1. Utilization of long duration high-volume sampling coupled to SPME-GC-MS/MS for the assessment of airborne pesticides variability in an urban area (Strasbourg, France) during agricultural application.

    Science.gov (United States)

    Liaud, Céline; Brucher, Michel; Schummer, Claude; Coscollà, Clara; Wolff, Hélène; Schwartz, Jean-Jacques; Yusà, Vicent; Millet, Maurice

    2016-10-02

    Atmospheric samples have been collected between 14 March and 12 September 2012 on a 2-week basis (15 days of sampling and exchange of traps each 7 days) in Strasbourg (east of France) for the analysis of 43 pesticides. Samples (particle and gas phases) were separately extracted using Accelerated Solvent Extraction (ASE) and pre-concentrated by Solid Phase Micro-Extraction (SPME) before analysis by gas chromatography coupled to tandem mass spectrometry (GC-MS/MS). Four SPME consecutive injections at distinct temperatures were made in order to increase the sensitivity of detection for the all monitored pesticides. Currently used detected pesticides can be grouped in four classes; those used in maize crops (acetochlor, benoxacor, dicamba, s-metolachlor, pendimethalin, and bromoxynil), in cereal crops (benoxacor, chlorothalonil, fenpropimorph, and propiconazole), in vineyards (tebuconazole), and as herbicides for orchards, meadows of green spaces (2,4-MCPA, trichlopyr). This is in accordance with the diversity of crops found in the Alsace region and trends observed are in accordance with the period of application of these pesticides. Variations observed permit also to demonstrate that the long time sampling duration used in this study is efficient to visualize temporal variations of airborne pesticides concentrations. Then, long time high-volume sampling could be a simple method permitting atmospheric survey of atmospheric contamination without any long analysis time and consequently low cost.

  2. 1H NMR and SPME-GC/MS study of hydrolysis, oxidation and other reactions occurring during in vitro digestion of non-oxidized and oxidized sunflower oil. Formation of hydroxy-octadecadienoates.

    Science.gov (United States)

    Nieva-Echevarría, Bárbara; Goicoechea, Encarnación; Manzanos, María J; Guillén, María D

    2017-01-01

    Both fresh and slightly oxidized sunflower oils, as models of omega-6 rich lipids, were submitted to in vitro gastrointestinal digestion and studied by 1 H NMR and SPME-GC/MS. Changes in lipolysis degree, lipid composition and oxidative level were studied by 1 H NMR. Three quantitative approaches were used and several equations were newly developed. In oxidized oil digestates slightly lower hydrolysis and a higher advance of oxidation took place during digestion. This latter was evidenced by a greater decrease of lipid unsaturation degree and enhanced generation of oxidation products (cis,trans-hydroperoxy-octadecadienoates, cis,trans- and trans,trans-hydroxy-octadecadienoates). For the first time, the generation of hydroxy-octadecadienoates during in vitro digestion is reported. Furthermore, SPME-GC/MS study of non-digested and digested samples headspaces confirmed that lipid oxidation occurred: abundances of volatile markers increased (including potentially toxic alpha,beta-unsaturated aldehydes), especially in oxidized oils digestates. Markers of Maillard-type and esterification reactions were also detected in the digestates. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Development and validation of an SPME-GC method for a degradation kinetics study of propiconazole I, propiconazole II and tebuconazole in blueberries in Concordia, the main production area of Argentina.

    Science.gov (United States)

    Munitz, Martín S; Medina, María B; Montti, María I T

    2017-05-01

    An analytical method for the simultaneous determination of propiconazole isomers and tebuconazole residues in blueberries was developed using solid-phase microextraction (SPME) coupled to gas chromatography. Confirmation was performed by gas chromatography-mass spectrometry in selected-ion monitoring mode. The SPME fibre coating selected was CWX-DVB, and the pH was adjusted to 7 with NaOH. The method is selective with adequate precision and high accuracy and sensitivity. Recoveries ranged between 97.4% and 98.9% for all compounds; and detection and quantification limits were respectively 0.21 and 0.49 μg kg -1 for propiconazole I; 0.16 and 0.22 μg kg -1 for propiconazole II; and 0.16 and 0.48 μg kg -1 for tebuconazole. The degradation of these fungicides in blueberries followed first-order rate kinetics. The half-life times for flowering and fruit set applications were respectively 4.0 and 10.3 days for propiconazole I, 4.0 and 11.4 days for propiconazole II, and 3.5 and 12.4 days for tebuconazole.

  4. Ultrafast Screening and Quantitation of Pesticides in Food and Environmental Matrices by Solid-Phase Microextraction-Transmission Mode (SPME-TM) and Direct Analysis in Real Time (DART).

    Science.gov (United States)

    Gómez-Ríos, Germán Augusto; Gionfriddo, Emanuela; Poole, Justen; Pawliszyn, Janusz

    2017-07-05

    The direct interface of microextraction technologies to mass spectrometry (MS) has unquestionably revolutionized the speed and efficacy at which complex matrices are analyzed. Solid Phase Micro Extraction-Transmission Mode (SPME-TM) is a technology conceived as an effective synergy between sample preparation and ambient ionization. Succinctly, the device consists of a mesh coated with polymeric particles that extracts analytes of interest present in a given sample matrix. This coated mesh acts as a transmission-mode substrate for Direct Analysis in Real Time (DART), allowing for rapid and efficient thermal desorption/ionization of analytes previously concentrated on the coating, and dramatically lowering the limits of detection attained by sole DART analysis. In this study, we present SPME-TM as a novel tool for the ultrafast enrichment of pesticides present in food and environmental matrices and their quantitative determination by MS via DART ionization. Limits of quantitation in the subnanogram per milliliter range can be attained, while total analysis time does not exceed 2 min per sample. In addition to target information obtained via tandem MS, retrospective studies of the same sample via high-resolution mass spectrometry (HRMS) were accomplished by thermally desorbing a different segment of the microextraction device.

  5. Analysis of enantiomeric and non-enantiomeric monoterpenes in plant emissions using portable dynamic air sampling/solid-phase microextraction (PDAS-SPME) and chiral gas chromatography/mass spectrometry

    Science.gov (United States)

    Yassaa, Noureddine; Williams, Jonathan

    A portable dynamic air sampler (PDAS) using a porous polymer solid-phase microextraction (SPME) fibre has been validated for the determination of biogenic enantiomeric and non-enantiomeric monoterpenes in air. These compounds were adsorbed in the field, and then thermally desorbed at 250 °C in a gas chromatograph injector port connected via a β-cyclodextrin capillary separating column to a mass spectrometer. The optimized method has been applied for investigating the emissions of enantiomeric monoterpenes from Pseudotsuga menziesii (Douglas-fir), Rosmarinus officinalis (Rosemary) and Lavandula lanata (Lavender) which were selected as representative of coniferous trees and aromatic plants, respectively. The enantiomers of α-pinene, sabinene, camphene, δ-3-carene, β-pinene, limonene, β-phellandrene, 4-carene and camphor were successfully determined in the emissions from the three plants. While Douglas-fir showed a strong predominance toward (-)-enantiomers, Rosemary and Lavender demonstrated a large variation in enantiomeric distribution of monoterpenes. The simplicity, rapidity and sensitivity of dynamic sampling with porous polymer coated SPME fibres coupled to chiral capillary gas chromatography/mass spectrometry (GC/MS) makes this method potentially useful for in-field investigations of atmosphere-biosphere interactions and studies of optically explicit atmospheric chemistry.

  6. Return Predictability, Model Uncertainty, and Robust Investment

    DEFF Research Database (Denmark)

    Lukas, Manuel

    Stock return predictability is subject to great uncertainty. In this paper we use the model confidence set approach to quantify uncertainty about expected utility from investment, accounting for potential return predictability. For monthly US data and six representative return prediction models, we...... find that confidence sets are very wide, change significantly with the predictor variables, and frequently include expected utilities for which the investor prefers not to invest. The latter motivates a robust investment strategy maximizing the minimal element of the confidence set. The robust investor...... allocates a much lower share of wealth to stocks compared to a standard investor....

  7. Three Contributions to Robust Regression Diagnostics

    Czech Academy of Sciences Publication Activity Database

    Kalina, Jan

    2015-01-01

    Roč. 11, č. 2 (2015), s. 69-78 ISSN 1336-9180 Grant - others:GA ČR(CZ) GA13-01930S; Nadační fond na podporu vědy(CZ) Neuron Institutional support: RVO:67985807 Keywords : robust regression * robust econometrics * hypothesis test ing Subject RIV: BA - General Mathematics http://www.degruyter.com/view/j/jamsi.2015.11.issue-2/jamsi-2015-0013/jamsi-2015-0013.xml?format=INT

  8. Robust Inference with Multi-way Clustering

    OpenAIRE

    A. Colin Cameron; Jonah B. Gelbach; Douglas L. Miller; Doug Miller

    2009-01-01

    In this paper we propose a variance estimator for the OLS estimator as well as for nonlinear estimators such as logit, probit and GMM. This variance estimator enables cluster-robust inference when there is two-way or multi-way clustering that is non-nested. The variance estimator extends the standard cluster-robust variance estimator or sandwich estimator for one-way clustering (e.g. Liang and Zeger (1986), Arellano (1987)) and relies on similar relatively weak distributional assumptions. Our...

  9. Robust control synthesis for uncertain dynamical systems

    Science.gov (United States)

    Byun, Kuk-Whan; Wie, Bong; Sunkel, John

    1989-01-01

    This paper presents robust control synthesis techniques for uncertain dynamical systems subject to structured parameter perturbation. Both QFT (quantitative feedback theory) and H-infinity control synthesis techniques are investigated. Although most H-infinity-related control techniques are not concerned with the structured parameter perturbation, a new way of incorporating the parameter uncertainty in the robust H-infinity control design is presented. A generic model of uncertain dynamical systems is used to illustrate the design methodologies investigated in this paper. It is shown that, for a certain noncolocated structural control problem, use of both techniques results in nonminimum phase compensation.

  10. Robustness of multiparty nonlocality to local decoherence

    International Nuclear Information System (INIS)

    Jang, Sung Soon; Cheong, Yong Wook; Kim, Jaewan; Lee, Hai-Woong

    2006-01-01

    We investigate the robustness of multiparty nonlocality under local decoherence, acting independently and equally on each subsystem. To be specific, we consider an N-qubit Greenberger-Horne-Zeilinger (GHZ) state under a depolarization, dephasing, or dissipation channel, and examine nonlocality by testing violation of the Mermin-Klyshko inequality, which is one of Bell's inequalities for multiqubit systems. The results show that the robustness of nonlocality increases with the number of qubits, and that the nonlocality of an N-qubit GHZ state with even N is extremely persistent against dephasing

  11. Robust speaker recognition in noisy environments

    CERN Document Server

    Rao, K Sreenivasa

    2014-01-01

    This book discusses speaker recognition methods to deal with realistic variable noisy environments. The text covers authentication systems for; robust noisy background environments, functions in real time and incorporated in mobile devices. The book focuses on different approaches to enhance the accuracy of speaker recognition in presence of varying background environments. The authors examine: (a) Feature compensation using multiple background models, (b) Feature mapping using data-driven stochastic models, (c) Design of super vector- based GMM-SVM framework for robust speaker recognition, (d) Total variability modeling (i-vectors) in a discriminative framework and (e) Boosting method to fuse evidences from multiple SVM models.

  12. Robust Parametric Control of Spacecraft Rendezvous

    Directory of Open Access Journals (Sweden)

    Dake Gu

    2014-01-01

    Full Text Available This paper proposes a method to design the robust parametric control for autonomous rendezvous of spacecrafts with the inertial information with uncertainty. We consider model uncertainty of traditional C-W equation to formulate the dynamic model of the relative motion. Based on eigenstructure assignment and model reference theory, a concise control law for spacecraft rendezvous is proposed which could be fixed through solving an optimization problem. The cost function considers the stabilization of the system and other performances. Simulation results illustrate the robustness and effectiveness of the proposed control.

  13. Robust cluster analysis and variable selection

    CERN Document Server

    Ritter, Gunter

    2014-01-01

    Clustering remains a vibrant area of research in statistics. Although there are many books on this topic, there are relatively few that are well founded in the theoretical aspects. In Robust Cluster Analysis and Variable Selection, Gunter Ritter presents an overview of the theory and applications of probabilistic clustering and variable selection, synthesizing the key research results of the last 50 years. The author focuses on the robust clustering methods he found to be the most useful on simulated data and real-time applications. The book provides clear guidance for the varying needs of bot

  14. Robust median estimator in logisitc regression

    Czech Academy of Sciences Publication Activity Database

    Hobza, T.; Pardo, L.; Vajda, Igor

    2008-01-01

    Roč. 138, č. 12 (2008), s. 3822-3840 ISSN 0378-3758 R&D Projects: GA MŠk 1M0572 Grant - others:Instituto Nacional de Estadistica (ES) MPO FI - IM3/136; GA MŠk(CZ) MTM 2006-06872 Institutional research plan: CEZ:AV0Z10750506 Keywords : Logistic regression * Median * Robustness * Consistency and asymptotic normality * Morgenthaler * Bianco and Yohai * Croux and Hasellbroeck Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 0.679, year: 2008 http://library.utia.cas.cz/separaty/2008/SI/vajda-robust%20median%20estimator%20in%20logistic%20regression.pdf

  15. Introduction to Robust Estimation and Hypothesis Testing

    CERN Document Server

    Wilcox, Rand R

    2012-01-01

    This revised book provides a thorough explanation of the foundation of robust methods, incorporating the latest updates on R and S-Plus, robust ANOVA (Analysis of Variance) and regression. It guides advanced students and other professionals through the basic strategies used for developing practical solutions to problems, and provides a brief background on the foundations of modern methods, placing the new methods in historical context. Author Rand Wilcox includes chapter exercises and many real-world examples that illustrate how various methods perform in different situations.Introduction to R

  16. Robust-mode analysis of hydrodynamic flows

    Science.gov (United States)

    Roy, Sukesh; Gord, James R.; Hua, Jia-Chen; Gunaratne, Gemunu H.

    2017-04-01

    The emergence of techniques to extract high-frequency high-resolution data introduces a new avenue for modal decomposition to assess the underlying dynamics, especially of complex flows. However, this task requires the differentiation of robust, repeatable flow constituents from noise and other irregular features of a flow. Traditional approaches involving low-pass filtering and principle components analysis have shortcomings. The approach outlined here, referred to as robust-mode analysis, is based on Koopman decomposition. Three applications to (a) a counter-rotating cellular flame state, (b) variations in financial markets, and (c) turbulent injector flows are provided.

  17. Robust giant magnetoresistive effect type multilayer sensor

    NARCIS (Netherlands)

    Lenssen, K.M.H.; Kuiper, A.E.T.; Roozeboom, F.

    2002-01-01

    A robust Giant Magneto Resistive effect type multilayer sensor comprising a free and a pinned ferromagnetic layer, which can withstand high temperatures and strong magnetic fields as required in automotive applications. The GMR multi-layer has an asymmetric magneto-resistive curve and enables

  18. New solutions for NPP robustness improvement

    International Nuclear Information System (INIS)

    Wolski, Alexander

    2013-01-01

    Fukushima accident has triggered a major re-assessment of robustness of nuclear stations. First round of evaluations has been Finished. Improvement areas and strategies have been identified. Implementation of upgrades has started world-wide. New solutions can provide substantial benefits

  19. Robust inference in sample selection models

    KAUST Repository

    Zhelonkin, Mikhail; Genton, Marc G.; Ronchetti, Elvezio

    2015-01-01

    The problem of non-random sample selectivity often occurs in practice in many fields. The classical estimators introduced by Heckman are the backbone of the standard statistical analysis of these models. However, these estimators are very sensitive to small deviations from the distributional assumptions which are often not satisfied in practice. We develop a general framework to study the robustness properties of estimators and tests in sample selection models. We derive the influence function and the change-of-variance function of Heckman's two-stage estimator, and we demonstrate the non-robustness of this estimator and its estimated variance to small deviations from the model assumed. We propose a procedure for robustifying the estimator, prove its asymptotic normality and give its asymptotic variance. Both cases with and without an exclusion restriction are covered. This allows us to construct a simple robust alternative to the sample selection bias test. We illustrate the use of our new methodology in an analysis of ambulatory expenditures and we compare the performance of the classical and robust methods in a Monte Carlo simulation study.

  20. Robust inference in sample selection models

    KAUST Repository

    Zhelonkin, Mikhail

    2015-11-20

    The problem of non-random sample selectivity often occurs in practice in many fields. The classical estimators introduced by Heckman are the backbone of the standard statistical analysis of these models. However, these estimators are very sensitive to small deviations from the distributional assumptions which are often not satisfied in practice. We develop a general framework to study the robustness properties of estimators and tests in sample selection models. We derive the influence function and the change-of-variance function of Heckman\\'s two-stage estimator, and we demonstrate the non-robustness of this estimator and its estimated variance to small deviations from the model assumed. We propose a procedure for robustifying the estimator, prove its asymptotic normality and give its asymptotic variance. Both cases with and without an exclusion restriction are covered. This allows us to construct a simple robust alternative to the sample selection bias test. We illustrate the use of our new methodology in an analysis of ambulatory expenditures and we compare the performance of the classical and robust methods in a Monte Carlo simulation study.

  1. Highly Robust Methods in Data Mining

    Czech Academy of Sciences Publication Activity Database

    Kalina, Jan

    2013-01-01

    Roč. 8, č. 1 (2013), s. 9-24 ISSN 1452-4864 Institutional support: RVO:67985807 Keywords : data mining * robust statistics * high-dimensional data * cluster analysis * logistic regression * neural networks Subject RIV: BB - Applied Statistics, Operational Research

  2. Robust Utility Maximization Under Convex Portfolio Constraints

    International Nuclear Information System (INIS)

    Matoussi, Anis; Mezghani, Hanen; Mnif, Mohamed

    2015-01-01

    We study a robust maximization problem from terminal wealth and consumption under a convex constraints on the portfolio. We state the existence and the uniqueness of the consumption–investment strategy by studying the associated quadratic backward stochastic differential equation. We characterize the optimal control by using the duality method and deriving a dynamic maximum principle

  3. Robust diamond meshes with unique wettability properties.

    Science.gov (United States)

    Yang, Yizhou; Li, Hongdong; Cheng, Shaoheng; Zou, Guangtian; Wang, Chuanxi; Lin, Quan

    2014-03-18

    Robust diamond meshes with excellent superhydrophobic and superoleophilic properties have been fabricated. Superhydrophobicity is observed for water with varying pH from 1 to 14 with good recyclability. Reversible superhydrophobicity and hydrophilicity can be easily controlled. The diamond meshes show highly efficient water-oil separation and water pH droplet transference.

  4. Robustness of dynamic systems with parameter uncertainties

    CERN Document Server

    Balemi, S; Truöl, W

    1992-01-01

    Robust Control is one of the fastest growing and promising areas of research today. In many practical systems there exist uncertainties which have to be considered in the analysis and design of control systems. In the last decade methods were developed for dealing with dynamic systems with unstructured uncertainties such as HOO_ and £I-optimal control. For systems with parameter uncertainties, the seminal paper of V. L. Kharitonov has triggered a large amount of very promising research. An international workshop dealing with all aspects of robust control was successfully organized by S. P. Bhattacharyya and L. H. Keel in San Antonio, Texas, USA in March 1991. We organized the second international workshop in this area in Ascona, Switzer­ land in April 1992. However, this second workshop was restricted to robust control of dynamic systems with parameter uncertainties with the objective to concentrate on some aspects of robust control. This book contains a collection of papers presented at the International W...

  5. Robust predictions of the interacting boson model

    International Nuclear Information System (INIS)

    Casten, R.F.; Koeln Univ.

    1994-01-01

    While most recognized for its symmetries and algebraic structure, the IBA model has other less-well-known but equally intrinsic properties which give unavoidable, parameter-free predictions. These predictions concern central aspects of low-energy nuclear collective structure. This paper outlines these ''robust'' predictions and compares them with the data

  6. Robust keyword retrieval method for OCRed text

    Science.gov (United States)

    Fujii, Yusaku; Takebe, Hiroaki; Tanaka, Hiroshi; Hotta, Yoshinobu

    2011-01-01

    Document management systems have become important because of the growing popularity of electronic filing of documents and scanning of books, magazines, manuals, etc., through a scanner or a digital camera, for storage or reading on a PC or an electronic book. Text information acquired by optical character recognition (OCR) is usually added to the electronic documents for document retrieval. Since texts generated by OCR generally include character recognition errors, robust retrieval methods have been introduced to overcome this problem. In this paper, we propose a retrieval method that is robust against both character segmentation and recognition errors. In the proposed method, the insertion of noise characters and dropping of characters in the keyword retrieval enables robustness against character segmentation errors, and character substitution in the keyword of the recognition candidate for each character in OCR or any other character enables robustness against character recognition errors. The recall rate of the proposed method was 15% higher than that of the conventional method. However, the precision rate was 64% lower.

  7. Robust Algebraic Multilevel Methods and Algorithms

    CERN Document Server

    Kraus, Johannes

    2009-01-01

    This book deals with algorithms for the solution of linear systems of algebraic equations with large-scale sparse matrices, with a focus on problems that are obtained after discretization of partial differential equations using finite element methods. Provides a systematic presentation of the recent advances in robust algebraic multilevel methods. Can be used for advanced courses on the topic.

  8. Replication and Robustness in Developmental Research

    Science.gov (United States)

    Duncan, Greg J.; Engel, Mimi; Claessens, Amy; Dowsett, Chantelle J.

    2014-01-01

    Replications and robustness checks are key elements of the scientific method and a staple in many disciplines. However, leading journals in developmental psychology rarely include explicit replications of prior research conducted by different investigators, and few require authors to establish in their articles or online appendices that their key…

  9. A Robust Alternative to the Normal Distribution.

    Science.gov (United States)

    1982-07-07

    for any Purpose of the United States Governuent DEPARTMENT OF STATISTICS t -, STANFORD UIVERSITY I STANFORD, CALIFORNIA A Robust Alternative to the...Stanford University Technical Report No. 3. [5] Bhattacharya, S. K. (1966). A Modified Bessel Function lodel in Life Testing. Metrika 10, 133-144

  10. Robust bayesian inference of generalized Pareto distribution ...

    African Journals Online (AJOL)

    En utilisant une etude exhaustive de Monte Carlo, nous prouvons que, moyennant une fonction perte generalisee adequate, on peut construire un estimateur Bayesien robuste du modele. Key words: Bayesian estimation; Extreme value; Generalized Fisher information; Gener- alized Pareto distribution; Monte Carlo; ...

  11. Robust balance shift control with posture optimization

    NARCIS (Netherlands)

    Kavafoglu, Z.; Kavafoglu, Ersan; Egges, J.

    2015-01-01

    In this paper we present a control framework which creates robust and natural balance shifting behaviours during standing. Given high-level features such as the position of the center of mass projection and the foot configurations, a kinematic posture satisfying these features is synthesized using

  12. Finite Algorithms for Robust Linear Regression

    DEFF Research Database (Denmark)

    Madsen, Kaj; Nielsen, Hans Bruun

    1990-01-01

    The Huber M-estimator for robust linear regression is analyzed. Newton type methods for solution of the problem are defined and analyzed, and finite convergence is proved. Numerical experiments with a large number of test problems demonstrate efficiency and indicate that this kind of approach may...

  13. Robust network design for multispecies conservation

    Science.gov (United States)

    Ronan Le Bras; Bistra Dilkina; Yexiang Xue; Carla P. Gomes; Kevin S. McKelvey; Michael K. Schwartz; Claire A. Montgomery

    2013-01-01

    Our work is motivated by an important network design application in computational sustainability concerning wildlife conservation. In the face of human development and climate change, it is important that conservation plans for protecting landscape connectivity exhibit certain level of robustness. While previous work has focused on conservation strategies that result...

  14. Neuromorphic Configurable Architecture for Robust Motion Estimation

    Directory of Open Access Journals (Sweden)

    Guillermo Botella

    2008-01-01

    Full Text Available The robustness of the human visual system recovering motion estimation in almost any visual situation is enviable, performing enormous calculation tasks continuously, robustly, efficiently, and effortlessly. There is obviously a great deal we can learn from our own visual system. Currently, there are several optical flow algorithms, although none of them deals efficiently with noise, illumination changes, second-order motion, occlusions, and so on. The main contribution of this work is the efficient implementation of a biologically inspired motion algorithm that borrows nature templates as inspiration in the design of architectures and makes use of a specific model of human visual motion perception: Multichannel Gradient Model (McGM. This novel customizable architecture of a neuromorphic robust optical flow can be constructed with FPGA or ASIC device using properties of the cortical motion pathway, constituting a useful framework for building future complex bioinspired systems running in real time with high computational complexity. This work includes the resource usage and performance data, and the comparison with actual systems. This hardware has many application fields like object recognition, navigation, or tracking in difficult environments due to its bioinspired and robustness properties.

  15. Robust control charts in statistical process control

    NARCIS (Netherlands)

    Nazir, H.Z.

    2014-01-01

    The presence of outliers and contaminations in the output of the process highly affects the performance of the design structures of commonly used control charts and hence makes them of less practical use. One of the solutions to deal with this problem is to use control charts which are robust

  16. Some Diagnostic Tools in Robust Econometrics

    Czech Academy of Sciences Publication Activity Database

    Kalina, Jan

    2011-01-01

    Roč. 50, č. 2 (2011), s. 55-67 ISSN 0231-9721 Grant - others:GA ČR(CZ) GA402/09/0557 Institutional research plan: CEZ:AV0Z10300504 Keywords : robust regression * autocorrelated errors * heteroscedastic regression * instrumental variables * least weighted squares Subject RIV: BB - Applied Statistics, Operational Research http://dml.cz/handle/10338.dmlcz/141754

  17. Robust estimation for ordinary differential equation models.

    Science.gov (United States)

    Cao, J; Wang, L; Xu, J

    2011-12-01

    Applied scientists often like to use ordinary differential equations (ODEs) to model complex dynamic processes that arise in biology, engineering, medicine, and many other areas. It is interesting but challenging to estimate ODE parameters from noisy data, especially when the data have some outliers. We propose a robust method to address this problem. The dynamic process is represented with a nonparametric function, which is a linear combination of basis functions. The nonparametric function is estimated by a robust penalized smoothing method. The penalty term is defined with the parametric ODE model, which controls the roughness of the nonparametric function and maintains the fidelity of the nonparametric function to the ODE model. The basis coefficients and ODE parameters are estimated in two nested levels of optimization. The coefficient estimates are treated as an implicit function of ODE parameters, which enables one to derive the analytic gradients for optimization using the implicit function theorem. Simulation studies show that the robust method gives satisfactory estimates for the ODE parameters from noisy data with outliers. The robust method is demonstrated by estimating a predator-prey ODE model from real ecological data. © 2011, The International Biometric Society.

  18. Chromatin regulators, phenotypic robustness and autism risk

    Directory of Open Access Journals (Sweden)

    Reut eSuliman

    2014-04-01

    Full Text Available Though extensively characterized clinically, the causes of autism spectrum disorder (ASD remain a mystery. ASD is known to have a strong genetic basis, but it is genetically very heterogeneous. Recent studies have estimated that de novo disruptive mutations in hundreds of genes may contribute to ASD. However, it is unclear how it is possible for mutations in so many different genes to contribute to ASD. Recent findings suggest that many of the mutations disrupt genes involved in transcription regulation that are expressed prenatally in the developing brain. De novo disruptive mutations are also more frequent in girls with ASD, despite the fact that ASD is more prevalent in boys. In this paper, we hypothesize that loss of robustness may contribute to ASD. Loss of phenotypic robustness may be caused by mutations that disrupt capacitors that operate in the developing brain. This may lead to the release of cryptic genetic variation that contributes to ASD. Reduced robustness is consistent with the observed variability in expressivity and incomplete penetrance. It is also consistent with the hypothesis that the development of the female brain is more robust, and it may explain the higher rate and severity of disruptive de novo mutations in girls with ASD.

  19. Robust and Adaptive Control With Aerospace Applications

    CERN Document Server

    Lavretsky, Eugene

    2013-01-01

    Robust and Adaptive Control shows the reader how to produce consistent and accurate controllers that operate in the presence of uncertainties and unforeseen events. Driven by aerospace applications the focus of the book is primarily on continuous-dynamical systems.  The text is a three-part treatment, beginning with robust and optimal linear control methods and moving on to a self-contained presentation of the design and analysis of model reference adaptive control (MRAC) for nonlinear uncertain dynamical systems. Recent extensions and modifications to MRAC design are included, as are guidelines for combining robust optimal and MRAC controllers. Features of the text include: ·         case studies that demonstrate the benefits of robust and adaptive control for piloted, autonomous and experimental aerial platforms; ·         detailed background material for each chapter to motivate theoretical developments; ·         realistic examples and simulation data illustrating key features ...

  20. Robust Pedestrian Navigation for Challenging Applications

    OpenAIRE

    Gilliéron, PY; Renaudin, V

    2009-01-01

    Presentation of a concept for robust indoor navigation. The concept is based on three key elements: - the use of an absolute geographical reference - the hybridisation of complementary technologies - specific motion models. This concept is illustrated by the means of two applications: the urban displacement of blind people and the indoor guidance of fire-fighters

  1. Robust online face tracking-by-detection

    NARCIS (Netherlands)

    Comaschi, F.; Stuijk, S.; Basten, T.; Corporaal, H.

    2016-01-01

    The problem of online face tracking from unconstrained videos is still unresolved. Challenges range from coping with severe online appearance variations to coping with occlusion. We propose RFTD (Robust Face Tracking-by-Detection), a system which combines tracking and detection into a single

  2. Robust control investigations for equipment loaded panels

    DEFF Research Database (Denmark)

    Aglietti, G.S.; Langley, R.S.; Rogers, E.

    1998-01-01

    This paper develops a modelling technique for equipment load panels which directly produces (adequate) models of the underlying dynamics on which to base robust controller design/evaluations. This technique is based on the use of the Lagrange's equations of motion and the resulting models...

  3. Robust Design of Sounds in Mechanical Mechanisms

    DEFF Research Database (Denmark)

    Boegedal Jensen, Annemette; Munch, Natasja; Howard, Thomas J.

    2015-01-01

    mechanism consisting of a toothed rack and a click arm. First several geometries of the teeth and the click arm’s head were investigated to identify the most robust and repeatable design. It was found that a flat surface in the valleys between the teeth is very beneficial in relation to repeatability...

  4. Robust glint detection through homography normalization

    DEFF Research Database (Denmark)

    Hansen, Dan Witzner; Roholm, Lars; García Ferreiros, Iván

    2014-01-01

    A novel normalization principle for robust glint detection is presented. The method is based on geometric properties of corneal reflections and allows for simple and effective detection of glints even in the presence of several spurious and identically appearing reflections. The method is tested...

  5. Robust power spectral estimation for EEG data.

    Science.gov (United States)

    Melman, Tamar; Victor, Jonathan D

    2016-08-01

    Typical electroencephalogram (EEG) recordings often contain substantial artifact. These artifacts, often large and intermittent, can interfere with quantification of the EEG via its power spectrum. To reduce the impact of artifact, EEG records are typically cleaned by a preprocessing stage that removes individual segments or components of the recording. However, such preprocessing can introduce bias, discard available signal, and be labor-intensive. With this motivation, we present a method that uses robust statistics to reduce dependence on preprocessing by minimizing the effect of large intermittent outliers on the spectral estimates. Using the multitaper method (Thomson, 1982) as a starting point, we replaced the final step of the standard power spectrum calculation with a quantile-based estimator, and the Jackknife approach to confidence intervals with a Bayesian approach. The method is implemented in provided MATLAB modules, which extend the widely used Chronux toolbox. Using both simulated and human data, we show that in the presence of large intermittent outliers, the robust method produces improved estimates of the power spectrum, and that the Bayesian confidence intervals yield close-to-veridical coverage factors. The robust method, as compared to the standard method, is less affected by artifact: inclusion of outliers produces fewer changes in the shape of the power spectrum as well as in the coverage factor. In the presence of large intermittent outliers, the robust method can reduce dependence on data preprocessing as compared to standard methods of spectral estimation. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Chance constrained uncertain classification via robust optimization

    NARCIS (Netherlands)

    Ben-Tal, A.; Bhadra, S.; Bhattacharayya, C.; Saketha Nat, J.

    2011-01-01

    This paper studies the problem of constructing robust classifiers when the training is plagued with uncertainty. The problem is posed as a Chance-Constrained Program (CCP) which ensures that the uncertain data points are classified correctly with high probability. Unfortunately such a CCP turns out

  7. Robust Geometric Control of a Distillation Column

    DEFF Research Database (Denmark)

    Kymmel, Mogens; Andersen, Henrik Weisberg

    1987-01-01

    A frequency domain method, which makes it possible to adjust multivariable controllers with respect to both nominal performance and robustness, is presented. The basic idea in the approach is that the designer assigns objectives such as steady-state tracking, maximum resonance peaks, bandwidth, m...... is used to examine and improve geometric control of a binary distillation column....

  8. Quantifying the robustness of metro networks

    NARCIS (Netherlands)

    Wang, X.; Koç, Y.; Derrible, S.; Nasir Ahmad, Sk.; Kooij, R.E.

    2015-01-01

    Metros (heavy rail transit systems) are integral parts of urban transportation systems. Failures in their operations can have serious impacts on urban mobility, and measuring their robustness is therefore critical. Moreover, as physical networks, metros can be viewed as network topological entities,

  9. Robust Refinement as Implemented in TOPAS

    Energy Technology Data Exchange (ETDEWEB)

    Stone, K.; Stephens, P

    2010-01-01

    A robust refinement procedure is implemented in the program TOPAS through an iterative reweighting of the data. Examples are given of the procedure as applied to fitting partially overlapped peaks by full and partial models and also of the structures of ibuprofen and acetaminophen in the presence of unmodeled impurity contributions

  10. Robust Satisfiability of Systems of Equations

    Czech Academy of Sciences Publication Activity Database

    Franek, Peter; Krčál, M.

    2015-01-01

    Roč. 62, č. 4 (2015), Article 26 ISSN 0004-5411 R&D Projects: GA ČR GBP202/12/G061 Grant - others:GA MŠk(CZ) LL1201 Institutional support: RVO:67985807 Keywords : nonlinear equations * satisfability * undecibility * topological extensions * uncertainty * robustness Subject RIV: IN - Informatics, Computer Science Impact factor: 1.803, year: 2015

  11. Robust fitting of diurnal brightness temperature cycle

    CSIR Research Space (South Africa)

    Udahemuka, G

    2007-11-01

    Full Text Available for a pixel concerned. Robust fitting of observed Diurnal Temperature Cycle (DTC) taken over a day of a given pixel without cloud cover and other abnormally conditions such as fire can give a data based brightness temperature model for a given pixel...

  12. Robustness of Linear Systems towards Multi-Dissipative Pertubations

    DEFF Research Database (Denmark)

    Thygesen, Uffe Høgsbro; Poulsen, Niels Kjølstad

    1997-01-01

    We consider the question of robust stability of a linear time invariant plant subject to dynamic perturbations, which are dissipative in the sense of Willems with respect to several quadratic supply rates. For instance, parasitic dynamics are often both small gain and passive. We reduce several...... robustness analysis questions to linear matrix inequalities: robust stability, robust H2 performance and robust performance in presence of disturbances with finite signal-to-noise ratios...

  13. Robust Parameter Coordination for Multidisciplinary Design

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper introduced a robust parameter coordination method to analyze parameter uncertainties so as to predict conflicts and coordinate parameters in multidisciplinary design. The proposed method is based on constraints network, which gives a formulated model to analyze the coupling effects between design variables and product specifications. In this model, interval boxes are adopted to describe the uncertainty of design parameters quantitatively to enhance the design robustness. To solve this constraint network model, a general consistent algorithm framework is designed and implemented with interval arithmetic and the genetic algorithm, which can deal with both algebraic and ordinary differential equations. With the help of this method, designers could infer the consistent solution space from the given specifications. A case study involving the design of a bogie dumping system demonstrates the usefulness of this approach.

  14. Robust lyapunov controller for uncertain systems

    KAUST Repository

    Laleg-Kirati, Taous-Meriem

    2017-02-23

    Various examples of systems and methods are provided for Lyapunov control for uncertain systems. In one example, a system includes a process plant and a robust Lyapunov controller configured to control an input of the process plant. The robust Lyapunov controller includes an inner closed loop Lyapunov controller and an outer closed loop error stabilizer. In another example, a method includes monitoring a system output of a process plant; generating an estimated system control input based upon a defined output reference; generating a system control input using the estimated system control input and a compensation term; and adjusting the process plant based upon the system control input to force the system output to track the defined output reference. An inner closed loop Lyapunov controller can generate the estimated system control input and an outer closed loop error stabilizer can generate the system control input.

  15. Communicating via robust synchronization of chaotic lasers

    International Nuclear Information System (INIS)

    Lopez-Gutierrez, R.M.; Posadas-Castillo, C.; Lopez-Mancilla, D.; Cruz-Hernandez, C.

    2009-01-01

    In this paper, the robust synchronization problem for coupled chaotic Nd:YAG lasers is addressed. We resort to complex systems theory to achieve chaos synchronization. Based on stability theory, it is shown that the state trajectories of the perturbed error synchronization are ultimately bounded, provided the unperturbed synchronization error system is exponentially stable, and some conditions on the bounds of the perturbation terms are satisfied. So that, encoding, transmission, and decoding in chaotic optical communications are presented. We analyze the transmission and recovery of encrypted information when parameter mismatches are considered. Computer simulations are provided to show the effectiveness of this robustness synchronization property, we present the encrypted transmission of image messages, and we show that, the transmitted image is faithfully recovered.

  16. Communicating via robust synchronization of chaotic lasers

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Gutierrez, R.M. [Engineering Faculty, Baja California Autonomous University (UABC), Km. 103 Carret. Tij-Ens., 22860 Ensenada, B.C. (Mexico); Posadas-Castillo, C. [Engineering Faculty, Baja California Autonomous University (UABC), Km. 103 Carret. Tij-Ens., 22860 Ensenada, B.C. (Mexico); FIME, Autonomous University of Nuevo Leon (UANL), Pedro de Alba, S.N., Cd. Universitaria, San Nicolas de los Garza, NL (Mexico); Lopez-Mancilla, D. [Departamento de Ciencias Exactas y Tecnologicas, Centro Universitario de los Lagos, Universidad de Guadalajara (CULagos-UdeG), Enrique Diaz de Leon s/n, 47460 Lagos de Moreno, Jal. (Mexico); Cruz-Hernandez, C. [Electronics and Telecommunications Department, Scientific Research and Advanced Studies of Ensenada (CICESE), Km. 107 Carret. Tij-Ens., 22860 Ensenada, B.C. (Mexico)], E-mail: ccruz@cicese.mx

    2009-10-15

    In this paper, the robust synchronization problem for coupled chaotic Nd:YAG lasers is addressed. We resort to complex systems theory to achieve chaos synchronization. Based on stability theory, it is shown that the state trajectories of the perturbed error synchronization are ultimately bounded, provided the unperturbed synchronization error system is exponentially stable, and some conditions on the bounds of the perturbation terms are satisfied. So that, encoding, transmission, and decoding in chaotic optical communications are presented. We analyze the transmission and recovery of encrypted information when parameter mismatches are considered. Computer simulations are provided to show the effectiveness of this robustness synchronization property, we present the encrypted transmission of image messages, and we show that, the transmitted image is faithfully recovered.

  17. Robust small area prediction for counts.

    Science.gov (United States)

    Tzavidis, Nikos; Ranalli, M Giovanna; Salvati, Nicola; Dreassi, Emanuela; Chambers, Ray

    2015-06-01

    A new semiparametric approach to model-based small area prediction for counts is proposed and used for estimating the average number of visits to physicians for Health Districts in Central Italy. The proposed small area predictor can be viewed as an outlier robust alternative to the more commonly used empirical plug-in predictor that is based on a Poisson generalized linear mixed model with Gaussian random effects. Results from the real data application and from a simulation experiment confirm that the proposed small area predictor has good robustness properties and in some cases can be more efficient than alternative small area approaches. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

  18. Robust quantum optimizer with full connectivity.

    Science.gov (United States)

    Nigg, Simon E; Lörch, Niels; Tiwari, Rakesh P

    2017-04-01

    Quantum phenomena have the potential to speed up the solution of hard optimization problems. For example, quantum annealing, based on the quantum tunneling effect, has recently been shown to scale exponentially better with system size than classical simulated annealing. However, current realizations of quantum annealers with superconducting qubits face two major challenges. First, the connectivity between the qubits is limited, excluding many optimization problems from a direct implementation. Second, decoherence degrades the success probability of the optimization. We address both of these shortcomings and propose an architecture in which the qubits are robustly encoded in continuous variable degrees of freedom. By leveraging the phenomenon of flux quantization, all-to-all connectivity with sufficient tunability to implement many relevant optimization problems is obtained without overhead. Furthermore, we demonstrate the robustness of this architecture by simulating the optimal solution of a small instance of the nondeterministic polynomial-time hard (NP-hard) and fully connected number partitioning problem in the presence of dissipation.

  19. Robust haptic large distance telemanipulation for ITER

    International Nuclear Information System (INIS)

    Heck, D.J.F.; Heemskerk, C.J.M.; Koning, J.F.; Abbasi, A.; Nijmeijer, H.

    2013-01-01

    Highlights: • ITER remote handling maintenance can be controlled safely over a large distance. • Bilateral teleoperation experiments were performed in a local network. • Wave variables make the controller robust against constant communication delays. • Master and slave position synchronization guaranteed by proportional action. -- Abstract: During shutdowns, maintenance crews are expected to work in 24/6 shifts to perform critical remote handling maintenance tasks on the ITER system. In this article, we investigate the possibility to safely perform these haptic maintenance tasks remotely from control stations located anywhere around the world. To guarantee stability in time delayed bilateral teleoperation, the symmetric position tracking controller using wave variables is selected. This algorithm guarantees robustness against communication delays, can eliminate wave reflections and provide position synchronization of the master and slave devices. Experiments have been conducted under realistic local network bandwidth, latency and jitter constraints. They show sufficient transparency even for substantial communication delays

  20. Design of Robust Neural Network Classifiers

    DEFF Research Database (Denmark)

    Larsen, Jan; Andersen, Lars Nonboe; Hintz-Madsen, Mads

    1998-01-01

    This paper addresses a new framework for designing robust neural network classifiers. The network is optimized using the maximum a posteriori technique, i.e., the cost function is the sum of the log-likelihood and a regularization term (prior). In order to perform robust classification, we present...... a modified likelihood function which incorporates the potential risk of outliers in the data. This leads to the introduction of a new parameter, the outlier probability. Designing the neural classifier involves optimization of network weights as well as outlier probability and regularization parameters. We...... suggest to adapt the outlier probability and regularisation parameters by minimizing the error on a validation set, and a simple gradient descent scheme is derived. In addition, the framework allows for constructing a simple outlier detector. Experiments with artificial data demonstrate the potential...

  1. Robustness and modular structure in networks

    DEFF Research Database (Denmark)

    Bagrow, James P.; Lehmann, Sune; Ahn, Yong-Yeol

    2015-01-01

    -12]. Many complex systems, from power grids and the Internet to the brain and society [13-15], can be modeled using modular networks comprised of small, densely connected groups of nodes [16, 17]. These modules often overlap, with network elements belonging to multiple modules [18, 19]. Yet existing work...... on robustness has not considered the role of overlapping, modular structure. Here we study the robustness of these systems to the failure of elements. We show analytically and empirically that it is possible for the modules themselves to become uncoupled or non-overlapping well before the network disintegrates....... If overlapping modular organization plays a role in overall functionality, networks may be far more vulnerable than predicted by conventional percolation theory....

  2. Track filtering by robust neural network

    International Nuclear Information System (INIS)

    Baginyan, S.A.; Kisel', I.V.; Konotopskaya, E.V.; Ososkov, G.A.

    1993-01-01

    In the present paper we study the following problems of track information extraction by the artificial neural network (ANN) rotor model: providing initial ANN configuration by an algorithm general enough to be applicable for any discrete detector in- or out of a magnetic field; robustness to heavy contaminated raw data (up to 100% signal-to-noise ratio); stability to the growing event multiplicity. These problems were carried out by corresponding innovations of our model, namely: by a special one-dimensional histogramming, by multiplying weights by a specially designed robust multiplier, and by replacing the simulated annealing schedule by ANN dynamics with an optimally fixed temperature. Our approach is valid for both circular and straight (non-magnetic) tracks and tested on 2D simulated data contaminated by 100% noise points distributed uniformly. To be closer to some reality in our simulation, we keep parameters of the cylindrical spectrometer ARES. 12 refs.; 9 figs

  3. Robustness analysis method for orbit control

    Science.gov (United States)

    Zhang, Jingrui; Yang, Keying; Qi, Rui; Zhao, Shuge; Li, Yanyan

    2017-08-01

    Satellite orbits require periodical maintenance due to the presence of perturbations. However, random errors caused by inaccurate orbit determination and thrust implementation may lead to failure of the orbit control strategy. Therefore, it is necessary to analyze the robustness of the orbit control methods. Feasible strategies which are tolerant to errors of a certain magnitude can be developed to perform reliable orbit control for the satellite. In this paper, first, the orbital dynamic model is formulated by Gauss' form of the planetary equation using the mean orbit elements; the atmospheric drag and the Earth's non-spherical perturbations are taken into consideration in this model. Second, an impulsive control strategy employing the differential correction algorithm is developed to maintain the satellite trajectory parameters in given ranges. Finally, the robustness of the impulsive control method is analyzed through Monte Carlo simulations while taking orbit determination error and thrust error into account.

  4. The Robustness of High Danish National Happiness

    DEFF Research Database (Denmark)

    Hussain, M. Azhar

    2014-01-01

    Denmark’s top position in various rankings of country happiness is well-documented. This study goes beyond the national average comparisons and investigates whether Denmark’s top position is also found when we disaggregate data in line with social categories often used within the social sciences....... The central measure is the empirical probability that a given population subgroup in Denmark has significantly higher happiness compared to another country’s similar subgroup in a given year. All five rounds of the European Social Survey are used but only the sixteen countries that were surveyed in each...... of the five rounds are included in this study. The results show that Denmark’s position at the top of the happiness scale is also robust when we look at population subgroups, but not in the sense that Denmark dominates all countries for all years. Instead, a modified version of robustness is necessary...

  5. Reliability and Robustness Evaluation of Timber Structures

    DEFF Research Database (Denmark)

    Cizmar, Dean; Sørensen, John Dalsgaard; Kirkegaard, Poul Henning

    In the last few decades there have been intensely research concerning reliability of timber structures. This is primarily because there is an increased focus on society on sustainability and environmental aspects. Modern timber as a building material is also being competitive compared to concrete...... and steel. However, reliability models applied to timber were always related to individual components but not the systems. as any real structure is a complex system, system behaviour must be of a particular interest. In the chapter 1 of this document an overview of stochastic models for strength and loads...... (deterministic, probabilistic and risk based approaches) of the robustness are given. Chapter 3 deals more detailed with the robustness of timber structures....

  6. Robust haptic large distance telemanipulation for ITER

    Energy Technology Data Exchange (ETDEWEB)

    Heck, D.J.F., E-mail: d.j.f.heck@tue.nl [Eindhoven University of Technology, Department of Mechanical Engineering, Eindhoven (Netherlands); Heemskerk, C.J.M.; Koning, J.F. [Heemskerk Innovative Technologies, Sassenheim (Netherlands); Abbasi, A.; Nijmeijer, H. [Eindhoven University of Technology, Department of Mechanical Engineering, Eindhoven (Netherlands)

    2013-10-15

    Highlights: • ITER remote handling maintenance can be controlled safely over a large distance. • Bilateral teleoperation experiments were performed in a local network. • Wave variables make the controller robust against constant communication delays. • Master and slave position synchronization guaranteed by proportional action. -- Abstract: During shutdowns, maintenance crews are expected to work in 24/6 shifts to perform critical remote handling maintenance tasks on the ITER system. In this article, we investigate the possibility to safely perform these haptic maintenance tasks remotely from control stations located anywhere around the world. To guarantee stability in time delayed bilateral teleoperation, the symmetric position tracking controller using wave variables is selected. This algorithm guarantees robustness against communication delays, can eliminate wave reflections and provide position synchronization of the master and slave devices. Experiments have been conducted under realistic local network bandwidth, latency and jitter constraints. They show sufficient transparency even for substantial communication delays.

  7. Robust blood-glucose control using Mathematica.

    Science.gov (United States)

    Kovács, Levente; Paláncz, Béla; Benyó, Balázs; Török, László; Benyó, Zoltán

    2006-01-01

    A robust control design on frequency domain using Mathematica is presented for regularization of glucose level in type I diabetes persons under intensive care. The method originally proposed under Mathematica by Helton and Merino, --now with an improved disturbance rejection constraint inequality--is employed, using a three-state minimal patient model. The robustness of the resulted high-order linear controller is demonstrated by nonlinear closed loop simulation in state-space, in case of standard meal disturbances and is compared with H infinity design implemented with the mu-toolbox of Matlab. The controller designed with model parameters represented the most favorable plant dynamics from the point of view of control purposes, can operate properly even in case of parameter values of the worst-case scenario.

  8. Model predictive control classical, robust and stochastic

    CERN Document Server

    Kouvaritakis, Basil

    2016-01-01

    For the first time, a textbook that brings together classical predictive control with treatment of up-to-date robust and stochastic techniques. Model Predictive Control describes the development of tractable algorithms for uncertain, stochastic, constrained systems. The starting point is classical predictive control and the appropriate formulation of performance objectives and constraints to provide guarantees of closed-loop stability and performance. Moving on to robust predictive control, the text explains how similar guarantees may be obtained for cases in which the model describing the system dynamics is subject to additive disturbances and parametric uncertainties. Open- and closed-loop optimization are considered and the state of the art in computationally tractable methods based on uncertainty tubes presented for systems with additive model uncertainty. Finally, the tube framework is also applied to model predictive control problems involving hard or probabilistic constraints for the cases of multiplic...

  9. Robust facility location: Hedging against failures

    International Nuclear Information System (INIS)

    Hernandez, Ivan; Emmanuel Ramirez-Marquez, Jose; Rainwater, Chase; Pohl, Edward; Medal, Hugh

    2014-01-01

    While few companies would be willing to sacrifice day-to-day operations to hedge against disruptions, designing for robustness can yield solutions that perform well before and after failures have occurred. Through a multi-objective optimization approach this paper provides decision makers the option to trade-off total weighted distance before and after disruptions in the Facility Location Problem. Additionally, this approach allows decision makers to understand the impact on the opening of facilities on total distance and on system robustness (considering the system as the set of located facilities). This approach differs from previous studies in that hedging against failures is done without having to elicit facility failure probabilities concurrently without requiring the allocation of additional hardening/protections resources. The approach is applied to two datasets from the literature

  10. Robust photometric stereo using structural light sources

    Science.gov (United States)

    Han, Tian-Qi; Cheng, Yue; Shen, Hui-Liang; Du, Xin

    2014-05-01

    We propose a robust photometric stereo method by using structural arrangement of light sources. In the arrangement, light sources are positioned on a planar grid and form a set of collinear combinations. The shadow pixels are detected by adaptive thresholding. The specular highlight and diffuse pixels are distinguished according to their intensity deviations of the collinear combinations, thanks to the special arrangement of light sources. The highlight detection problem is cast as a pattern classification problem and is solved using support vector machine classifiers. Considering the possible misclassification of highlight pixels, the ℓ1 regularization is further employed in normal map estimation. Experimental results on both synthetic and real-world scenes verify that the proposed method can robustly recover the surface normal maps in the case of heavy specular reflection and outperforms the state-of-the-art techniques.

  11. Robust gates for holonomic quantum computation

    International Nuclear Information System (INIS)

    Florio, Giuseppe; Pascazio, Saverio; Facchi, Paolo; Fazio, Rosario; Giovannetti, Vittorio

    2006-01-01

    Non-Abelian geometric phases are attracting increasing interest because of possible experimental application in quantum computation. We study the effects of the environment (modeled as an ensemble of harmonic oscillators) on a holonomic transformation and write the corresponding master equation. The solution is analytically and numerically investigated and the behavior of the fidelity analyzed: fidelity revivals are observed and an optimal finite operation time is determined at which the gate is most robust against noise

  12. Heteroscedasticity resistant robust covariance matrix estimator

    Czech Academy of Sciences Publication Activity Database

    Víšek, Jan Ámos

    2010-01-01

    Roč. 17, č. 27 (2010), s. 33-49 ISSN 1212-074X Grant - others:GA UK(CZ) GA402/09/0557 Institutional research plan: CEZ:AV0Z10750506 Keywords : Regression * Covariance matrix * Heteroscedasticity * Resistant Subject RIV: BB - Applied Statistics, Operational Research http://library.utia.cas.cz/separaty/2011/SI/visek-heteroscedasticity resistant robust covariance matrix estimator.pdf

  13. Robust motion estimation using connected operators

    OpenAIRE

    Salembier Clairon, Philippe Jean; Sanson, H

    1997-01-01

    This paper discusses the use of connected operators for robust motion estimation The proposed strategy involves a motion estimation step extracting the dominant motion and a ltering step relying on connected operators that remove objects that do not fol low the dominant motion. These two steps are iterated in order to obtain an accurate motion estimation and a precise de nition of the objects fol lowing this motion This strategy can be applied on the entire frame or on individual connected c...

  14. Muscle Synergy-Driven Robust Motion Control.

    Science.gov (United States)

    Min, Kyuengbo; Iwamoto, Masami; Kakei, Shinji; Kimpara, Hideyuki

    2018-04-01

    Humans are able to robustly maintain desired motion and posture under dynamically changing circumstances, including novel conditions. To accomplish this, the brain needs to optimize the synergistic control between muscles against external dynamic factors. However, previous related studies have usually simplified the control of multiple muscles using two opposing muscles, which are minimum actuators to simulate linear feedback control. As a result, they have been unable to analyze how muscle synergy contributes to motion control robustness in a biological system. To address this issue, we considered a new muscle synergy concept used to optimize the synergy between muscle units against external dynamic conditions, including novel conditions. We propose that two main muscle control policies synergistically control muscle units to maintain the desired motion against external dynamic conditions. Our assumption is based on biological evidence regarding the control of multiple muscles via the corticospinal tract. One of the policies is the group control policy (GCP), which is used to control muscle group units classified based on functional similarities in joint control. This policy is used to effectively resist external dynamic circumstances, such as disturbances. The individual control policy (ICP) assists the GCP in precisely controlling motion by controlling individual muscle units. To validate this hypothesis, we simulated the reinforcement of the synergistic actions of the two control policies during the reinforcement learning of feedback motion control. Using this learning paradigm, the two control policies were synergistically combined to result in robust feedback control under novel transient and sustained disturbances that did not involve learning. Further, by comparing our data to experimental data generated by human subjects under the same conditions as those of the simulation, we showed that the proposed synergy concept may be used to analyze muscle synergy

  15. Optimal interdependence enhances robustness of complex systems

    OpenAIRE

    Singh, R. K.; Sinha, Sitabhra

    2017-01-01

    While interdependent systems have usually been associated with increased fragility, we show that strengthening the interdependence between dynamical processes on different networks can make them more robust. By coupling the dynamics of networks that in isolation exhibit catastrophic collapse with extinction of nodal activity, we demonstrate system-wide persistence of activity for an optimal range of interdependence between the networks. This is related to the appearance of attractors of the g...

  16. Stability Constraints for Robust Model Predictive Control

    Directory of Open Access Journals (Sweden)

    Amanda G. S. Ottoni

    2015-01-01

    Full Text Available This paper proposes an approach for the robust stabilization of systems controlled by MPC strategies. Uncertain SISO linear systems with box-bounded parametric uncertainties are considered. The proposed approach delivers some constraints on the control inputs which impose sufficient conditions for the convergence of the system output. These stability constraints can be included in the set of constraints dealt with by existing MPC design strategies, in this way leading to the “robustification” of the MPC.

  17. Automatic Mode Transition Enabled Robust Triboelectric Nanogenerators.

    Science.gov (United States)

    Chen, Jun; Yang, Jin; Guo, Hengyu; Li, Zhaoling; Zheng, Li; Su, Yuanjie; Wen, Zhen; Fan, Xing; Wang, Zhong Lin

    2015-12-22

    Although the triboelectric nanogenerator (TENG) has been proven to be a renewable and effective route for ambient energy harvesting, its robustness remains a great challenge due to the requirement of surface friction for a decent output, especially for the in-plane sliding mode TENG. Here, we present a rationally designed TENG for achieving a high output performance without compromising the device robustness by, first, converting the in-plane sliding electrification into a contact separation working mode and, second, creating an automatic transition between a contact working state and a noncontact working state. The magnet-assisted automatic transition triboelectric nanogenerator (AT-TENG) was demonstrated to effectively harness various ambient rotational motions to generate electricity with greatly improved device robustness. At a wind speed of 6.5 m/s or a water flow rate of 5.5 L/min, the harvested energy was capable of lighting up 24 spot lights (0.6 W each) simultaneously and charging a capacitor to greater than 120 V in 60 s. Furthermore, due to the rational structural design and unique output characteristics, the AT-TENG was not only capable of harvesting energy from natural bicycling and car motion but also acting as a self-powered speedometer with ultrahigh accuracy. Given such features as structural simplicity, easy fabrication, low cost, wide applicability even in a harsh environment, and high output performance with superior device robustness, the AT-TENG renders an effective and practical approach for ambient mechanical energy harvesting as well as self-powered active sensing.

  18. Matlab as a robust control design tool

    Science.gov (United States)

    Gregory, Irene M.

    1994-01-01

    This presentation introduces Matlab as a tool used in flight control research. The example used to illustrate some of the capabilities of this software is a robust controller designed for a single stage to orbit air breathing vehicles's ascent to orbit. The global requirements of the controller are to stabilize the vehicle and follow a trajectory in the presence of atmospheric disturbances and strong dynamic coupling between airframe and propulsion.

  19. Adding query privacy to robust DHTs

    DEFF Research Database (Denmark)

    Backes, Michael; Goldberg, Ian; Kate, Aniket

    2012-01-01

    intermediate peers that (help to) route the queries towards their destinations. In this paper, we satisfy this requirement by presenting an approach for providing privacy for the keys in DHT queries. We use the concept of oblivious transfer (OT) in communication over DHTs to preserve query privacy without...... privacy over robust DHTs. Finally, we compare the performance of our privacy-preserving protocols with their more privacy-invasive counterparts. We observe that there is no increase in the message complexity...

  20. Sparse alignment for robust tensor learning.

    Science.gov (United States)

    Lai, Zhihui; Wong, Wai Keung; Xu, Yong; Zhao, Cairong; Sun, Mingming

    2014-10-01

    Multilinear/tensor extensions of manifold learning based algorithms have been widely used in computer vision and pattern recognition. This paper first provides a systematic analysis of the multilinear extensions for the most popular methods by using alignment techniques, thereby obtaining a general tensor alignment framework. From this framework, it is easy to show that the manifold learning based tensor learning methods are intrinsically different from the alignment techniques. Based on the alignment framework, a robust tensor learning method called sparse tensor alignment (STA) is then proposed for unsupervised tensor feature extraction. Different from the existing tensor learning methods, L1- and L2-norms are introduced to enhance the robustness in the alignment step of the STA. The advantage of the proposed technique is that the difficulty in selecting the size of the local neighborhood can be avoided in the manifold learning based tensor feature extraction algorithms. Although STA is an unsupervised learning method, the sparsity encodes the discriminative information in the alignment step and provides the robustness of STA. Extensive experiments on the well-known image databases as well as action and hand gesture databases by encoding object images as tensors demonstrate that the proposed STA algorithm gives the most competitive performance when compared with the tensor-based unsupervised learning methods.

  1. Distributed redundancy and robustness in complex systems

    KAUST Repository

    Randles, Martin

    2011-03-01

    The uptake and increasing prevalence of Web 2.0 applications, promoting new large-scale and complex systems such as Cloud computing and the emerging Internet of Services/Things, requires tools and techniques to analyse and model methods to ensure the robustness of these new systems. This paper reports on assessing and improving complex system resilience using distributed redundancy, termed degeneracy in biological systems, to endow large-scale complicated computer systems with the same robustness that emerges in complex biological and natural systems. However, in order to promote an evolutionary approach, through emergent self-organisation, it is necessary to specify the systems in an \\'open-ended\\' manner where not all states of the system are prescribed at design-time. In particular an observer system is used to select robust topologies, within system components, based on a measurement of the first non-zero Eigen value in the Laplacian spectrum of the components\\' network graphs; also known as the algebraic connectivity. It is shown, through experimentation on a simulation, that increasing the average algebraic connectivity across the components, in a network, leads to an increase in the variety of individual components termed distributed redundancy; the capacity for structurally distinct components to perform an identical function in a particular context. The results are applied to a specific application where active clustering of like services is used to aid load balancing in a highly distributed network. Using the described procedure is shown to improve performance and distribute redundancy. © 2010 Elsevier Inc.

  2. Effect of smoothing on robust chaos.

    Science.gov (United States)

    Deshpande, Amogh; Chen, Qingfei; Wang, Yan; Lai, Ying-Cheng; Do, Younghae

    2010-08-01

    In piecewise-smooth dynamical systems, situations can arise where the asymptotic attractors of the system in an open parameter interval are all chaotic (e.g., no periodic windows). This is the phenomenon of robust chaos. Previous works have established that robust chaos can occur through the mechanism of border-collision bifurcation, where border is the phase-space region where discontinuities in the derivatives of the dynamical equations occur. We investigate the effect of smoothing on robust chaos and find that periodic windows can arise when a small amount of smoothness is present. We introduce a parameter of smoothing and find that the measure of the periodic windows in the parameter space scales linearly with the parameter, regardless of the details of the smoothing function. Numerical support and a heuristic theory are provided to establish the scaling relation. Experimental evidence of periodic windows in a supposedly piecewise linear dynamical system, which has been implemented as an electronic circuit, is also provided.

  3. Robustness of inflation to inhomogeneous initial conditions

    Energy Technology Data Exchange (ETDEWEB)

    Clough, Katy; Lim, Eugene A. [Theoretical Particle Physics and Cosmology Group, Physics Department, Kings College London, Strand, London WC2R 2LS (United Kingdom); DiNunno, Brandon S.; Fischler, Willy; Flauger, Raphael; Paban, Sonia, E-mail: katy.clough@kcl.ac.uk, E-mail: eugene.a.lim@gmail.com, E-mail: bsd86@physics.utexas.edu, E-mail: fischler@physics.utexas.edu, E-mail: flauger@physics.utexas.edu, E-mail: paban@physics.utexas.edu [Department of Physics, The University of Texas at Austin, Austin, TX, 78712 (United States)

    2017-09-01

    We consider the effects of inhomogeneous initial conditions in both the scalar field profile and the extrinsic curvature on different inflationary models. In particular, we compare the robustness of small field inflation to that of large field inflation, using numerical simulations with Einstein gravity in 3+1 dimensions. We find that small field inflation can fail in the presence of subdominant gradient energies, suggesting that it is much less robust to inhomogeneities than large field inflation, which withstands dominant gradient energies. However, we also show that small field inflation can be successful even if some regions of spacetime start out in the region of the potential that does not support inflation. In the large field case, we confirm previous results that inflation is robust if the inflaton occupies the inflationary part of the potential. Furthermore, we show that increasing initial scalar gradients will not form sufficiently massive inflation-ending black holes if the initial hypersurface is approximately flat. Finally, we consider the large field case with a varying extrinsic curvature K , such that some regions are initially collapsing. We find that this may again lead to local black holes, but overall the spacetime remains inflationary if the spacetime is open, which confirms previous theoretical studies.

  4. Mutational robustness of gene regulatory networks.

    Directory of Open Access Journals (Sweden)

    Aalt D J van Dijk

    Full Text Available Mutational robustness of gene regulatory networks refers to their ability to generate constant biological output upon mutations that change network structure. Such networks contain regulatory interactions (transcription factor-target gene interactions but often also protein-protein interactions between transcription factors. Using computational modeling, we study factors that influence robustness and we infer several network properties governing it. These include the type of mutation, i.e. whether a regulatory interaction or a protein-protein interaction is mutated, and in the case of mutation of a regulatory interaction, the sign of the interaction (activating vs. repressive. In addition, we analyze the effect of combinations of mutations and we compare networks containing monomeric with those containing dimeric transcription factors. Our results are consistent with available data on biological networks, for example based on evolutionary conservation of network features. As a novel and remarkable property, we predict that networks are more robust against mutations in monomer than in dimer transcription factors, a prediction for which analysis of conservation of DNA binding residues in monomeric vs. dimeric transcription factors provides indirect evidence.

  5. TAO-robust backpropagation learning algorithm.

    Science.gov (United States)

    Pernía-Espinoza, Alpha V; Ordieres-Meré, Joaquín B; Martínez-de-Pisón, Francisco J; González-Marcos, Ana

    2005-03-01

    In several fields, as industrial modelling, multilayer feedforward neural networks are often used as universal function approximations. These supervised neural networks are commonly trained by a traditional backpropagation learning format, which minimises the mean squared error (mse) of the training data. However, in the presence of corrupted data (outliers) this training scheme may produce wrong models. We combine the benefits of the non-linear regression model tau-estimates [introduced by Tabatabai, M. A. Argyros, I. K. Robust Estimation and testing for general nonlinear regression models. Applied Mathematics and Computation. 58 (1993) 85-101] with the backpropagation algorithm to produce the TAO-robust learning algorithm, in order to deal with the problems of modelling with outliers. The cost function of this approach has a bounded influence function given by the weighted average of two psi functions, one corresponding to a very robust estimate and the other to a highly efficient estimate. The advantages of the proposed algorithm are studied with an example.

  6. Engineering Robustness of Microbial Cell Factories.

    Science.gov (United States)

    Gong, Zhiwei; Nielsen, Jens; Zhou, Yongjin J

    2017-10-01

    Metabolic engineering and synthetic biology offer great prospects in developing microbial cell factories capable of converting renewable feedstocks into fuels, chemicals, food ingredients, and pharmaceuticals. However, prohibitively low production rate and mass concentration remain the major hurdles in industrial processes even though the biosynthetic pathways are comprehensively optimized. These limitations are caused by a variety of factors unamenable for host cell survival, such as harsh industrial conditions, fermentation inhibitors from biomass hydrolysates, and toxic compounds including metabolic intermediates and valuable target products. Therefore, engineered microbes with robust phenotypes is essential for achieving higher yield and productivity. In this review, the recent advances in engineering robustness and tolerance of cell factories is described to cope with these issues and briefly introduce novel strategies with great potential to enhance the robustness of cell factories, including metabolic pathway balancing, transporter engineering, and adaptive laboratory evolution. This review also highlights the integration of advanced systems and synthetic biology principles toward engineering the harmony of overall cell function, more than the specific pathways or enzymes. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. A robust nonlinear filter for image restoration.

    Science.gov (United States)

    Koivunen, V

    1995-01-01

    A class of nonlinear regression filters based on robust estimation theory is introduced. The goal of the filtering is to recover a high-quality image from degraded observations. Models for desired image structures and contaminating processes are employed, but deviations from strict assumptions are allowed since the assumptions on signal and noise are typically only approximately true. The robustness of filters is usually addressed only in a distributional sense, i.e., the actual error distribution deviates from the nominal one. In this paper, the robustness is considered in a broad sense since the outliers may also be due to inappropriate signal model, or there may be more than one statistical population present in the processing window, causing biased estimates. Two filtering algorithms minimizing a least trimmed squares criterion are provided. The design of the filters is simple since no scale parameters or context-dependent threshold values are required. Experimental results using both real and simulated data are presented. The filters effectively attenuate both impulsive and nonimpulsive noise while recovering the signal structure and preserving interesting details.

  8. UNIX-based operating systems robustness evaluation

    Science.gov (United States)

    Chang, Yu-Ming

    1996-01-01

    Robust operating systems are required for reliable computing. Techniques for robustness evaluation of operating systems not only enhance the understanding of the reliability of computer systems, but also provide valuable feed- back to system designers. This thesis presents results from robustness evaluation experiments on five UNIX-based operating systems, which include Digital Equipment's OSF/l, Hewlett Packard's HP-UX, Sun Microsystems' Solaris and SunOS, and Silicon Graphics' IRIX. Three sets of experiments were performed. The methodology for evaluation tested (1) the exception handling mechanism, (2) system resource management, and (3) system capacity under high workload stress. An exception generator was used to evaluate the exception handling mechanism of the operating systems. Results included exit status of the exception generator and the system state. Resource management techniques used by individual operating systems were tested using programs designed to usurp system resources such as physical memory and process slots. Finally, the workload stress testing evaluated the effect of the workload on system performance by running a synthetic workload and recording the response time of local and remote user requests. Moderate to severe performance degradations were observed on the systems under stress.

  9. Interlinked bistable mechanisms generate robust mitotic transitions.

    Science.gov (United States)

    Hutter, Lukas H; Rata, Scott; Hochegger, Helfrid; Novák, Béla

    2017-10-18

    The transitions between phases of the cell cycle have evolved to be robust and switch-like, which ensures temporal separation of DNA replication, sister chromatid separation, and cell division. Mathematical models describing the biochemical interaction networks of cell cycle regulators attribute these properties to underlying bistable switches, which inherently generate robust, switch-like, and irreversible transitions between states. We have recently presented new mathematical models for two control systems that regulate crucial transitions in the cell cycle: mitotic entry and exit, 1 and the mitotic checkpoint. 2 Each of the two control systems is characterized by two interlinked bistable switches. In the case of mitotic checkpoint control, these switches are mutually activating, whereas in the case of the mitotic entry/exit network, the switches are mutually inhibiting. In this Perspective we describe the qualitative features of these regulatory motifs and show that having two interlinked bistable mechanisms further enhances robustness and irreversibility. We speculate that these network motifs also underlie other cell cycle transitions and cellular transitions between distinct biochemical states.

  10. Tension and robustness in multitasking cellular networks.

    Directory of Open Access Journals (Sweden)

    Jeffrey V Wong

    Full Text Available Cellular networks multitask by exhibiting distinct, context-dependent dynamics. However, network states (parameters that generate a particular dynamic are often sub-optimal for others, defining a source of "tension" between them. Though multitasking is pervasive, it is not clear where tension arises, what consequences it has, and how it is resolved. We developed a generic computational framework to examine the source and consequences of tension between pairs of dynamics exhibited by the well-studied RB-E2F switch regulating cell cycle entry. We found that tension arose from task-dependent shifts in parameters associated with network modules. Although parameter sets common to distinct dynamics did exist, tension reduced both their accessibility and resilience to perturbation, indicating a trade-off between "one-size-fits-all" solutions and robustness. With high tension, robustness can be preserved by dynamic shifting of modules, enabling the network to toggle between tasks, and by increasing network complexity, in this case by gene duplication. We propose that tension is a general constraint on the architecture and operation of multitasking biological networks. To this end, our work provides a framework to quantify the extent of tension between any network dynamics and how it affects network robustness. Such analysis would suggest new ways to interfere with network elements to elucidate the design principles of cellular networks.

  11. Hyperspectral Unmixing with Robust Collaborative Sparse Regression

    Directory of Open Access Journals (Sweden)

    Chang Li

    2016-07-01

    Full Text Available Recently, sparse unmixing (SU of hyperspectral data has received particular attention for analyzing remote sensing images. However, most SU methods are based on the commonly admitted linear mixing model (LMM, which ignores the possible nonlinear effects (i.e., nonlinearity. In this paper, we propose a new method named robust collaborative sparse regression (RCSR based on the robust LMM (rLMM for hyperspectral unmixing. The rLMM takes the nonlinearity into consideration, and the nonlinearity is merely treated as outlier, which has the underlying sparse property. The RCSR simultaneously takes the collaborative sparse property of the abundance and sparsely distributed additive property of the outlier into consideration, which can be formed as a robust joint sparse regression problem. The inexact augmented Lagrangian method (IALM is used to optimize the proposed RCSR. The qualitative and quantitative experiments on synthetic datasets and real hyperspectral images demonstrate that the proposed RCSR is efficient for solving the hyperspectral SU problem compared with the other four state-of-the-art algorithms.

  12. Robustness of airline alliance route networks

    Science.gov (United States)

    Lordan, Oriol; Sallan, Jose M.; Simo, Pep; Gonzalez-Prieto, David

    2015-05-01

    The aim of this study is to analyze the robustness of the three major airline alliances' (i.e., Star Alliance, oneworld and SkyTeam) route networks. Firstly, the normalization of a multi-scale measure of vulnerability is proposed in order to perform the analysis in networks with different sizes, i.e., number of nodes. An alternative node selection criterion is also proposed in order to study robustness and vulnerability of such complex networks, based on network efficiency. And lastly, a new procedure - the inverted adaptive strategy - is presented to sort the nodes in order to anticipate network breakdown. Finally, the robustness of the three alliance networks are analyzed with (1) a normalized multi-scale measure of vulnerability, (2) an adaptive strategy based on four different criteria and (3) an inverted adaptive strategy based on the efficiency criterion. The results show that Star Alliance has the most resilient route network, followed by SkyTeam and then oneworld. It was also shown that the inverted adaptive strategy based on the efficiency criterion - inverted efficiency - shows a great success in quickly breaking networks similar to that found with betweenness criterion but with even better results.

  13. A modified multiscale peak alignment method combined with trilinear decomposition to study the volatile/heat-labile components in Ligusticum chuanxiong Hort - Cyperus rotundus rhizomes by HS-SPME-GC/MS.

    Science.gov (United States)

    He, Min; Yan, Pan; Yang, Zhi-Yu; Zhang, Zhi-Min; Yang, Tian-Biao; Hong, Liang

    2018-03-15

    Head Space/Solid Phase Micro-Extraction (HS-SPME) coupled with Gas Chromatography/Mass Spectrometer (GC/MS) was used to determine the volatile/heat-labile components in Ligusticum chuanxiong Hort - Cyperus rotundus rhizomes. Facing co-eluting peaks in k samples, a trilinear structure was reconstructed to obtain the second-order advantage. The retention time (RT) shift with multi-channel detection signals for different samples has been vital in maintaining the trilinear structure, thus a modified multiscale peak alignment (mMSPA) method was proposed in this paper. The peak position and peak width of representative ion profile were firstly detected by mMSPA using Continuous Wavelet Transform with Haar wavelet as the mother wavelet (Haar CWT). Then, the raw shift was confirmed by Fast Fourier Transform (FFT) cross correlation calculation. To obtain the optimal shift, Haar CWT was again used to detect the subtle deviations and be amalgamated in calculation. Here, to ensure there is no peaks shape alternation, the alignment was performed in local domains of data matrices, and all data points in the peak zone were moved via linear interpolation in non-peak parts. Finally, chemical components of interest in Ligusticum chuanxiong Hort - Cyperus rotundus rhizomes were analyzed by HS-SPME-GCMS and mMSPA-alternating trilinear decomposition (ATLD) resolution. As a result, the concentration variation between herbs and their pharmaceutical products can provide a scientific basic for the quality standard establishment of traditional Chinese medicines. Copyright © 2018 Elsevier B.V. All rights reserved.

  14. Robustness Recipes for Minimax Robust Optimization in Intensity Modulated Proton Therapy for Oropharyngeal Cancer Patients

    Energy Technology Data Exchange (ETDEWEB)

    Voort, Sebastian van der [Department of Radiation Oncology, Erasmus MC Cancer Institute, Rotterdam (Netherlands); Section of Nuclear Energy and Radiation Applications, Department of Radiation, Science and Technology, Delft University of Technology, Delft (Netherlands); Water, Steven van de [Department of Radiation Oncology, Erasmus MC Cancer Institute, Rotterdam (Netherlands); Perkó, Zoltán [Section of Nuclear Energy and Radiation Applications, Department of Radiation, Science and Technology, Delft University of Technology, Delft (Netherlands); Heijmen, Ben [Department of Radiation Oncology, Erasmus MC Cancer Institute, Rotterdam (Netherlands); Lathouwers, Danny [Section of Nuclear Energy and Radiation Applications, Department of Radiation, Science and Technology, Delft University of Technology, Delft (Netherlands); Hoogeman, Mischa, E-mail: m.hoogeman@erasmusmc.nl [Department of Radiation Oncology, Erasmus MC Cancer Institute, Rotterdam (Netherlands)

    2016-05-01

    Purpose: We aimed to derive a “robustness recipe” giving the range robustness (RR) and setup robustness (SR) settings (ie, the error values) that ensure adequate clinical target volume (CTV) coverage in oropharyngeal cancer patients for given gaussian distributions of systematic setup, random setup, and range errors (characterized by standard deviations of Σ, σ, and ρ, respectively) when used in minimax worst-case robust intensity modulated proton therapy (IMPT) optimization. Methods and Materials: For the analysis, contoured computed tomography (CT) scans of 9 unilateral and 9 bilateral patients were used. An IMPT plan was considered robust if, for at least 98% of the simulated fractionated treatments, 98% of the CTV received 95% or more of the prescribed dose. For fast assessment of the CTV coverage for given error distributions (ie, different values of Σ, σ, and ρ), polynomial chaos methods were used. Separate recipes were derived for the unilateral and bilateral cases using one patient from each group, and all 18 patients were included in the validation of the recipes. Results: Treatment plans for bilateral cases are intrinsically more robust than those for unilateral cases. The required RR only depends on the ρ, and SR can be fitted by second-order polynomials in Σ and σ. The formulas for the derived robustness recipes are as follows: Unilateral patients need SR = −0.15Σ{sup 2} + 0.27σ{sup 2} + 1.85Σ − 0.06σ + 1.22 and RR=3% for ρ = 1% and ρ = 2%; bilateral patients need SR = −0.07Σ{sup 2} + 0.19σ{sup 2} + 1.34Σ − 0.07σ + 1.17 and RR=3% and 4% for ρ = 1% and 2%, respectively. For the recipe validation, 2 plans were generated for each of the 18 patients corresponding to Σ = σ = 1.5 mm and ρ = 0% and 2%. Thirty-four plans had adequate CTV coverage in 98% or more of the simulated fractionated treatments; the remaining 2 had adequate coverage in 97.8% and 97.9%. Conclusions: Robustness recipes were derived that can

  15. Robust estimation of hydrological model parameters

    Directory of Open Access Journals (Sweden)

    A. Bárdossy

    2008-11-01

    Full Text Available The estimation of hydrological model parameters is a challenging task. With increasing capacity of computational power several complex optimization algorithms have emerged, but none of the algorithms gives a unique and very best parameter vector. The parameters of fitted hydrological models depend upon the input data. The quality of input data cannot be assured as there may be measurement errors for both input and state variables. In this study a methodology has been developed to find a set of robust parameter vectors for a hydrological model. To see the effect of observational error on parameters, stochastically generated synthetic measurement errors were applied to observed discharge and temperature data. With this modified data, the model was calibrated and the effect of measurement errors on parameters was analysed. It was found that the measurement errors have a significant effect on the best performing parameter vector. The erroneous data led to very different optimal parameter vectors. To overcome this problem and to find a set of robust parameter vectors, a geometrical approach based on Tukey's half space depth was used. The depth of the set of N randomly generated parameters was calculated with respect to the set with the best model performance (Nash-Sutclife efficiency was used for this study for each parameter vector. Based on the depth of parameter vectors, one can find a set of robust parameter vectors. The results show that the parameters chosen according to the above criteria have low sensitivity and perform well when transfered to a different time period. The method is demonstrated on the upper Neckar catchment in Germany. The conceptual HBV model was used for this study.

  16. Robust transient dynamics and brain functions

    Directory of Open Access Journals (Sweden)

    Mikhail I Rabinovich

    2011-06-01

    Full Text Available In the last few decades several concepts of Dynamical Systems Theory (DST have guided psychologists, cognitive scientists, and neuroscientists to rethink about sensory motor behavior and embodied cognition. A critical step in the progress of DST application to the brain (supported by modern methods of brain imaging and multi-electrode recording techniques has been the transfer of its initial success in motor behavior to mental function, i.e., perception, emotion, and cognition. Open questions from research in genetics, ecology, brain sciences, etc. have changed DST itself and lead to the discovery of a new dynamical phenomenon, i.e., reproducible and robust transients that are at the same time sensitive to informational signals. The goal of this review is to describe a new mathematical framework -heteroclinic sequential dynamics- to understand self-organized activity in the brain that can explain certain aspects of robust itinerant behavior. Specifically, we discuss a hierarchy of coarse-grain models of mental dynamics in the form of kinetic equations of modes. These modes compete for resources at three levels: (i within the same modality, (ii among different modalities from the same family (like perception, and (iii among modalities from different families (like emotion and cognition. The analysis of the conditions for robustness, i.e., the structural stability of transient (sequential dynamics, give us the possibility to explain phenomena like the finite capacity of our sequential working memory -a vital cognitive function-, and to find specific dynamical signatures -different kinds of instabilities- of several brain functions and mental diseases.

  17. Robust Short-Lag Spatial Coherence Imaging.

    Science.gov (United States)

    Nair, Arun Asokan; Tran, Trac Duy; Bell, Muyinatu A Lediju

    2018-03-01

    Short-lag spatial coherence (SLSC) imaging displays the spatial coherence between backscattered ultrasound echoes instead of their signal amplitudes and is more robust to noise and clutter artifacts when compared with traditional delay-and-sum (DAS) B-mode imaging. However, SLSC imaging does not consider the content of images formed with different lags, and thus does not exploit the differences in tissue texture at each short-lag value. Our proposed method improves SLSC imaging by weighting the addition of lag values (i.e., M-weighting) and by applying robust principal component analysis (RPCA) to search for a low-dimensional subspace for projecting coherence images created with different lag values. The RPCA-based projections are considered to be denoised versions of the originals that are then weighted and added across lags to yield a final robust SLSC (R-SLSC) image. Our approach was tested on simulation, phantom, and in vivo liver data. Relative to DAS B-mode images, the mean contrast, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) improvements with R-SLSC images are 21.22 dB, 2.54, and 2.36, respectively, when averaged over simulated, phantom, and in vivo data and over all lags considered, which corresponds to mean improvements of 96.4%, 121.2%, and 120.5%, respectively. When compared with SLSC images, the corresponding mean improvements with R-SLSC images were 7.38 dB, 1.52, and 1.30, respectively (i.e., mean improvements of 14.5%, 50.5%, and 43.2%, respectively). Results show great promise for smoothing out the tissue texture of SLSC images and enhancing anechoic or hypoechoic target visibility at higher lag values, which could be useful in clinical tasks such as breast cyst visualization, liver vessel tracking, and obese patient imaging.

  18. Robust and accurate vectorization of line drawings.

    Science.gov (United States)

    Hilaire, Xavier; Tombre, Karl

    2006-06-01

    This paper presents a method for vectorizing the graphical parts of paper-based line drawings. The method consists of separating the input binary image into layers of homogeneous thickness, skeletonizing each layer, segmenting the skeleton by a method based on random sampling, and simplifying the result. The segmentation method is robust with a best bound of 50 percent noise reached for indefinitely long primitives. Accurate estimation of the recognized vector's parameters is enabled by explicitly computing their feasibility domains. Theoretical performance analysis and expression of the complexity of the segmentation method are derived. Experimental results and comparisons with other vectorization systems are also provided.

  19. Robustness of Populations in Stochastic Environments

    DEFF Research Database (Denmark)

    Gießen, Christian; Kötzing, Timo

    2016-01-01

    We consider stochastic versions of OneMax and LeadingOnes and analyze the performance of evolutionary algorithms with and without populations on these problems. It is known that the (1+1) EA on OneMax performs well in the presence of very small noise, but poorly for higher noise levels. We extend...... the abilities of the (1+1) EA. Larger population sizes are even more beneficial; we consider both parent and offspring populations. In this sense, populations are robust in these stochastic settings....

  20. Integrated robust controller for vehicle path following

    Energy Technology Data Exchange (ETDEWEB)

    Mashadi, Behrooz; Ahmadizadeh, Pouyan, E-mail: p-ahmadizadeh@iust.ac.ir; Majidi, Majid, E-mail: m-majidi@iust.ac.ir [Iran University of Science and Technology, School of Automotive Engineering (Iran, Islamic Republic of); Mahmoodi-Kaleybar, Mehdi, E-mail: m-mahmoodi-k@iust.ac.ir [Iran University of Science and Technology, School of Mechanical Engineering (Iran, Islamic Republic of)

    2015-02-15

    The design of an integrated 4WS+DYC control system to guide a vehicle on a desired path is presented. The lateral dynamics of the path follower vehicle is formulated by considering important parameters. To reduce the effect of uncertainties in vehicle parameters, a robust controller is designed based on a μ-synthesis approach. Numerical simulations are performed using a nonlinear vehicle model in MATLAB environment in order to investigate the effectiveness of the designed controller. Results of simulations show that the controller has a profound ability to making the vehicle track the desired path in the presence of uncertainties.