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Sample records for volatile isoprenoids oxygenated

  1. Emissions of isoprenoids and oxygenated biogenic volatile organic compounds from a New England mixed forest

    Directory of Open Access Journals (Sweden)

    K. A. McKinney

    2011-05-01

    Full Text Available Fluxes of biogenic volatile organic compounds, including isoprene, monoterpenes, and oxygenated VOCs measured above a mixed forest canopy in central Massachusetts during the 2005 and 2007 growing seasons are reported. Mixing ratios were measured using proton transfer reaction mass spectrometry (PTR-MS and fluxes computed by the disjunct eddy covariance technique. Isoprene was by far the predominant BVOC emitted at this site, with summer mid-day average fluxes of 5.3 and 4.4 mg m−2 hr−1 in 2005 and 2007, respectively. In comparison, mid-day average fluxes of monoterpenes were 0.21 and 0.15 mg m−2 hr−1 in each of these years. On short times scales (days, the diel pattern in emission rate compared well with a standard emission algorithm for isoprene. The general shape of the seasonal cycle and the observed decrease in isoprene emission rate in early September was, however, not well captured by the model. Monoterpene emission rates exhibited dependence on light as well as temperature, as determined from the improved fit to the observations obtained by including a light-dependent term in the model. The mid-day average flux of methanol from the canopy was 0.14 mg m−2 hr−1 in 2005 and 0.19 mg m−2 hr−1 in 2007, but the maximum flux was observed in spring (29 May 2007, when the flux reached 1.0 mg m−2 hr−1. This observation is consistent with enhanced methanol production during leaf expansion. Summer mid-day fluxes of acetone were 0.15 mg m−2 hr−1 during a short period in 2005, but only 0.03 mg m−2 h−1 averaged over 2007. Episodes of negative fluxes of oxygenated VOCs, particularly acetone, were observed periodically, especially in 2007. Thus, deposition within the canopy could help explain the low season-averaged flux of acetone in 2007. Fluxes of species of biogenic origin

  2. Emissions of isoprenoids and oxygenated biogenic volatile organic compounds from a New England mixed forest

    Directory of Open Access Journals (Sweden)

    K. A. McKinney

    2010-11-01

    Full Text Available Fluxes of biogenic volatile organic compounds, including isoprene, monoterpenes, and oxygenated VOCs measured above a mixed forest canopy in western Massachusetts during the 2005 and 2007 growing seasons are reported. Measurements were made using proton transfer reaction mass spectrometry (PTR-MS and converted to fluxes using the disjunct eddy covariance technique. Isoprene was by far the predominant BVOC emitted at this site, with summer mid-day average fluxes of 5.3 and 4.4 mg m−2 h−1 in 2005 and 2007, respectively. In comparison, mid-day average fluxes of monoterpenes were 0.21 and 0.15 mg m−2 h−1 in each of these years. On short times scales (days, the diel pattern in emission rate compared well with a standard emission algorithm for isoprene. The general shape of the seasonal cycle and the observed decrease in isoprene emission rate in early September was, however, not well captured by the model. Monoterpene emission rates exhibited dependence on light as well as temperature, as determined from the improved fit to the observations obtained by including a light-dependent term in the model. The mid-day average flux of methanol from the canopy was 0.14 mg m−2 h−1 in 2005 and 0.19 mg m−2 h−1 in 2007, but the maximum flux was observed in spring (29 May 2007, when the flux reached 1.0 mg m−2 h−1. This observation is consistent with enhanced methanol production during leaf expansion. Summer mid-day fluxes of acetone were 0.15 mg m−2 h−1 during a short period in 2005, but only 0.03 mg m−2 h−1 averaged over 2007. Episodes of negative fluxes of oxygenated VOCs, particularly acetone, were observed periodically, especially in 2007. Thus, deposition within the canopy could help explain the low season-averaged flux of acetone in 2007. Fluxes of species of biogenic origin at

  3. Metabolic engineering of volatile isoprenoids in plants and microbes

    NARCIS (Netherlands)

    Vickers, C.; Bongers, M.; Liu, Q.; Delatte, T.L.; Bouwmeester, H.J.

    2014-01-01

    The chemical properties and diversity of volatile isoprenoids lends them to a broad variety of biological roles. It also lends them to a host of biotechnological applications, both by taking advantage of their natural functions and by using them as industrial chemicals/chemical feedstocks. Natural

  4. Volatile isoprenoids as defense compounds during abiotic stress in tropical plants

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    Jardine, K.

    2015-12-01

    Emissions of volatile isoprenoids from tropical forests play central roles in atmospheric processes by fueling atmospheric chemistry resulting in modified aerosol and cloud lifecycles and their associated feedbacks with the terrestrial biosphere. However, the identities of tropical isoprenoids, their biological and environmental controls, and functions within plants and ecosystems remain highly uncertain. As part of the DOE ARM program's GoAmazon 2014/15 campaign, extensive field and laboratory observations of volatile isoprenoids are being conducted in the central Amazon. Here we report the results of our completed and ongoing activities at the ZF2 forest reserve in the central Amazon. Among the results of the research are the suprisingly high abundance of light-dependent volatile isoprenoid emissions across abundant tree genera in the Amazon in both primary and secondary forests, the discovery of highly reactive monoterpene emissions from Amazon trees, and evidence for the importance of volatile isoprenoids in protecting photosynthesis during oxidative stress under elevated temperatures including energy consumption and direct antioxidant functions and a tight connection betwen volatile isoprenoid emissions, photorespiration, and CO2 recycling within leaves. The results highlight the need to model allocation of carbon to isoprenoids during elevated temperature stress in the tropics.

  5. The leaf-level emission factor of volatile isoprenoids: caveats, model algorithms, response shapes and scaling

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    Ü. Niinemets

    2010-06-01

    Full Text Available In models of plant volatile isoprenoid emissions, the instantaneous compound emission rate typically scales with the plant's emission potential under specified environmental conditions, also called as the emission factor, ES. In the most widely employed plant isoprenoid emission models, the algorithms developed by Guenther and colleagues (1991, 1993, instantaneous variation of the steady-state emission rate is described as the product of ES and light and temperature response functions. When these models are employed in the atmospheric chemistry modeling community, species-specific ES values and parameter values defining the instantaneous response curves are often taken as initially defined. In the current review, we argue that ES as a characteristic used in the models importantly depends on our understanding of which environmental factors affect isoprenoid emissions, and consequently need standardization during experimental ES determinations. In particular, there is now increasing consensus that in addition to variations in light and temperature, alterations in atmospheric and/or within-leaf CO2 concentrations may need to be included in the emission models. Furthermore, we demonstrate that for less volatile isoprenoids, mono- and sesquiterpenes, the emissions are often jointly controlled by the compound synthesis and volatility. Because of these combined biochemical and physico-chemical drivers, specification of ES as a constant value is incapable of describing instantaneous emissions within the sole assumptions of fluctuating light and temperature as used in the standard algorithms. The definition of ES also varies depending on the degree of aggregation of ES values in different parameterization schemes (leaf- vs. canopy- or region-scale, species vs. plant functional type levels and various

  6. The emission factor of volatile isoprenoids: stress, acclimation, and developmental responses

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    Ü. Niinemets

    2010-07-01

    Full Text Available The rate of constitutive isoprenoid emissions from plants is driven by plant emission capacity under specified environmental conditions (ES, the emission factor and by responsiveness of the emissions to instantaneous variations in environment. In models of isoprenoid emission, ES has been often considered as intrinsic species-specific constant invariable in time and space. Here we analyze the variations in species-specific values of ES under field conditions focusing on abiotic stresses, past environmental conditions and developmental processes. The reviewed studies highlight strong stress-driven, adaptive (previous temperature and light environment and growth CO2 concentration and developmental (leaf age variations in ES values operating at medium to long time scales. These biological factors can alter species-specific ES values by more than an order of magnitude. While the majority of models based on early concepts still ignore these important sources of variation, recent models are including some of the medium- to long-term controls. However, conceptually different strategies are being used for incorporation of these longer-term controls with important practical implications for parameterization and application of these models. This analysis emphasizes the need to include more biological realism in the isoprenoid emission models and also highlights the gaps in knowledge that require further experimental work to reduce the model uncertainties associated with biological sources of variation.

  7. Remote sensing of plant emissions of volatile isoprenoids with PRI. Prospects for upscaling (Invited)

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    Penuelas, J.

    2013-12-01

    Josep Peñuelas*1,2, Giovanni Marino1,2,3,4, Joan LLusia1,2, Catherine Morfopoulos1,2,5, Gerard Farre-Armengol1,2, Shawn Kefauver, Alex Guenther6 , Francesca Rapparini7 , Roger Seco1,2,6, Marc Estiarte1,2, Mónica Mejia-Chang1,2, Romà Ogaya1,2, Jordi Sardans1,2 , Andrew Turnipseed6, Peter Harley6, Osvaldo Facini7, Rita Baraldi7, Jim Greenberg6 , Iolanda Filella1,2 1 CSIC, Global Ecology Unit CREAF-CEAB-UAB, Cerdanyola del Vallés 08193, Catalonia, Spain 2 CREAF, Cerdanyola del Vallés 08193, Catalonia, Spain 3 Dipartimento di Bioscienze e Territorio, Università degli Studi del Molise, Contrada Fonte Lappone, 86090 Pesche (IS), Italy 4 Institute for Plant Protection, National Research Council, Via Madonna del Piano 10, 50019 Sesto Fiorentino (FI), Italy 5 Division of Ecology and Evolution, Imperial College, Silwood Park, Ascot, SL5 7PY, UK 6 Atmospheric Chemistry Division, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000, USA 7 Biometeorology Institute, IBIMET-CNR, Via P. Gobetti 101, Bologna, Italy Abstract Terrestrial plants re-emit around 1-2% of the carbon they fix as isoprene and monoterpenes. These emissions play major roles in the ecological relationships among living organisms and in atmospheric chemistry and climate, and yet their actual quantification at the ecosystem level in different regions is far from being resolved. Phenomenological models are used to estimate the emission rates, but the limited understanding of the function and regulation of these emissions leads to large uncertainties in such estimations. Many measurements have been made at the foliar but few at the ecosystem level, and those that do exist are limited in space and time. We here provide evidence that a simple remote sensing index, the photochemical reflectance index (PRI), which is indicative of light use efficiency (LUE), is a good indirect estimator of foliar isoprenoid emissions and therefore can be used to sense them remotely. These results open

  8. Tomato carotenoid cleavage dioxygenases 1A and 1B: Relaxed double bond specificity leads to a plenitude of dialdehydes, mono-apocarotenoids and isoprenoid volatiles

    KAUST Repository

    Ilg, Andrea

    2014-06-25

    The biosynthetic processes leading to many of the isoprenoid volatiles released by tomato fruits are still unknown, though previous reports suggested a clear correlation with the carotenoids contained within the fruit. In this study, we investigated the activity of the tomato (Solanum lycopersicum) carotenoid cleavage dioxygenase (SlCCD1B), which is highly expressed in fruits, and of its homolog SlCCD1A. Using in vitro assays performed with purified recombinant enzymes and by analyzing products formed by the two enzymes in carotene-accumulating Escherichia coli strains, we demonstrate that SlCCD1A and, to a larger extent, SlCCD1B, have a very relaxed specificity for both substrate and cleavage site, mediating the oxidative cleavage of cis- and all-. trans-carotenoids as well as of different apocarotenoids at many more double bonds than previously reported. This activity gives rise to a plenitude of volatiles, mono-apocarotenoids and dialdehyde products, including cis-pseudoionone, neral, geranial, and farnesylacetone. Our results provide a direct evidence for a carotenoid origin of these compounds and point to CCD1s as the enzymes catalyzing the formation of the vast majority of tomato isoprenoid volatiles, many of which are aroma constituents. © 2014 The Authors.

  9. Do geostable polycyclic isoprenoids record the rise of oxygen in the ancient atmosphere?

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    Bosak, T.; Losick, R.; Pearson, A.

    2007-12-01

    Polycyclic terpenoids are among the most stable and abundant lipid compounds in sediments of all ages. They may record the composition of microbial communities and environmental conditions in the past, including the rise of molecular oxygen 2.7 billion years ago. A great deal is known about how some of these lipids are produced by the enzymatic cyclization of linear terpenoids by a family of triterpene cyclases, but whether and how specific polycyclic compounds reflect certain metabolisms or physiologies of modern microbes is not well understood. Here we demonstrate that a novel class of tetracyclic terpenoids is present in the spores of B. subtilis. These compounds are derived from the enzymatic cyclization of regular linear terpenoids by a protein homologous to known triterpenoid cyclases. The cyclization of regular linear terpenoids is thought to have produced the most ancient polycyclic terpenoids but, until now, there have not been any known modern microbial sources of such compounds. The presence of tetracyclic terpenoids increases the resistance of spores to hydrogen peroxide, a reactive oxygen species, establishing for the first time a physiological function of bacterial polycyclic terpenoids in vivo. Our work demonstrates that some polycyclic terpenoids play a direct role in protecting modern bacteria from reactive oxygen species. Similarly, their geostable derivatives in the rock record may imply the presence of oxidative stress related to the oxygenation of Earth's surface in the past.

  10. Volatile hydrocarbons and fuel oxygenates: Chapter 12

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    Cozzarelli, Isabelle M.

    2014-01-01

    Petroleum hydrocarbons and fuel oxygenates are among the most commonly occurring and widely distributed contaminants in the environment. This chapter presents a summary of the sources, transport, fate, and remediation of volatile fuel hydrocarbons and fuel additives in the environment. Much research has focused on the transport and transformation processes of petroleum hydrocarbons and fuel oxygenates, such as benzene, toluene, ethylbenzene, and xylenes and methyl tert‐butyl ether, in groundwater following release from underground storage tanks. Natural attenuation from biodegradation limits the movement of these contaminants and has received considerable attention as an environmental restoration option. This chapter summarizes approaches to environmental restoration, including those that rely on natural attenuation, and also engineered or enhanced remediation. Researchers are increasingly combining several microbial and molecular-based methods to give a complete picture of biodegradation potential and occurrence at contaminated field sites. New insights into the fate of petroleum hydrocarbons and fuel additives have been gained by recent advances in analytical tools and approaches, including stable isotope fractionation, analysis of metabolic intermediates, and direct microbial evidence. However, development of long-term detailed monitoring programs is required to further develop conceptual models of natural attenuation and increase our understanding of the behavior of contaminant mixtures in the subsurface.

  11. AM fungi root colonization increases the production of essential isoprenoids vs. nonessential isoprenoids especially under drought stress conditions or after jasmonic acid application.

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    Asensio, Dolores; Rapparini, Francesca; Peñuelas, Josep

    2012-05-01

    Previous studies have shown that root colonization by arbuscular mycorrhiza (AM) fungi enhances plant resistance to abiotic and biotic stressors and finally plant growth. However, little is known about the effect of AM on isoprenoid foliar and root content. In this study we tested whether the AM symbiosis affects carbon resource allocation to different classes of isoprenoids such as the volatile nonessential isoprenoids (monoterpenes and sesquiterpenes) and the non-volatile essential isoprenoids (abscisic acid, chlorophylls and carotenoids). By subjecting the plants to stressors such as drought and to exogenous application of JA, we wanted to test their interaction with AM symbiosis in conditions where isoprenoids usually play a role in resistance to stress and in plant defence. Root colonization by AM fungi favoured the leaf production of essential isoprenoids rather than nonessential ones, especially under drought stress conditions or after JA application. The increased carbon demand brought on by AM fungi might thus influence not only the amount of carbon allocated to isoprenoids, but also the carbon partitioning between the different classes of isoprenoids, thus explaining the not previously shown decrease of root volatile isoprenoids in AM plants. We propose that since AM fungi are a nutrient source for the plant, other carbon sinks normally necessary to increase nutrient uptake can be avoided and therefore the plant can devote more resources to synthesize essential isoprenoids for plant growth. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

  12. The Oxygen and Volatile Extraction Node (OVEN) Subsystem for Resource Prospector

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    Paz, Aaron; Oryshchyn, Lara

    2014-01-01

    The OVEN (Oxygen and Volatile Extraction Node) Subsystem is part of the RESOLVE (Regolith and Environment Science & Oxygen and Lunar Volatile Extraction) Payload, whose main objective is to verify the presence of water and other volatiles on the lunar surface. The RESOLVE payload is scheduled to fly to the moon as part of the Resource Prospector (RP) in 2019. The OVEN Subsystem accepts regolith (soil) and evolves the volatiles contained in the sample by heating the segment to a temperature of at least 150oC for volatile analysis and as high as 900oC for hydrogen reduction. In general, a regolith segment is deposited into a crucible; the crucible is heated and evolved gases flow to a gas analyzer.

  13. Substrate analogues for isoprenoid enzymes

    Energy Technology Data Exchange (ETDEWEB)

    Stremler, K.E.

    1987-01-01

    Diphosphonate analogues of geranyl diphosphate, resistant to degradation by phosphatases, were found to be alternate substrates for the reaction with farnesyl diphosphate synthetase isolated from avian liver. The difluoromethane analogue was shown to be the better alternate substrate, in agreement with solvolysis results which indicate that the electronegativity of the difluoromethylene unit more closely approximates that of the normal bridging oxygen. The usefulness of the C/sub 10/ difluoro analogue, for detecting low levels of isoprenoid enzymes in the presence of high levels of phosphatase activity, was demonstrated with a cell-free preparation from lemon peel. A series of C/sub 5/ through C/sub 15/ homoallylic and allylic diphosphonates, as well as two 5'-nucleotide diphosphonates, was prepared in high overall yield using the activation-displacement sequence. Radiolabeled samples of several of the allylic diphosphonates were prepared with tritium located at C1. A series of geraniols, stereospecifically deuterated at C1, was prepared. The enantiomeric purities and absolute configurations were determined by derivatization as the mandelate esters for analysis by /sup 1/H NMR. The stereochemistry of the activation-displacement sequence was examined using C1-deuterated substrates.

  14. RESOLVE (Regolith & Environmental Science Oxygen & Lunar Volatile Extraction) Project

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    Parker, Ray; Coan, Mary; Captain, Janine; Cryderman, Kate; Quinn, Jacqueline

    2015-01-01

    The RESOLVE Project is a lunar prospecting mission whose primary goal is to characterize water and other volatiles in lunar regolith. The Lunar Advanced Volatiles Analysis (LAVA) subsystem is comprised of a fluid subsystem that transports flow to the gas chromatograph - mass spectrometer (GC-MS) instruments that characterize volatiles and the Water Droplet Demonstration (WDD) that will capture and display water condensation in the gas stream. The LAVA Engineering Test Unit (ETU) is undergoing risk reduction testing this summer and fall within a vacuum chamber to understand and characterize component and integrated system performance. Testing of line heaters, printed circuit heaters, pressure transducers, temperature sensors, regulators, and valves in atmospheric and vacuum environments was done. Test procedures were developed to guide experimental tests and test reports to analyze and draw conclusions from the data. In addition, knowledge and experience was gained with preparing a vacuum chamber with fluid and electrical connections. Further testing will include integrated testing of the fluid subsystem with the gas supply system, near-infrared spectrometer for the Surge Tank (NIRST), WDD, Sample Delivery System, and GC-MS in the vacuum chamber. Since LAVA is a scientific subsystem, the near infrared spectrometer and GC-MS instruments will be tested during the ETU testing phase.

  15. Method for measurement of volatile oxygenated hydrocarbons in ambient air

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    Leibrock, E.; Slemr, J.

    An automated gas chromatographic method for the quantitative determination of oxygenated (C 2C 5 carbonyls and C 1C 2 alcohols) and some non-oxygenated (C 5C 8) hydrocarbons in ambient air has been developed. The analytical system consists of a gas chromatograph with a cryogenic sampling trap, a precolumn for the separation of water and other interfering compounds, a cryogenic focusing trap and two analytical columns connected in series. Substances are detected either by flame ionization or by a mass spectrometer. Ozone is removed by a potassium iodide scrubber placed upstream the sampling trap. External gas standards generated by a permeation device are used for calibration. The detection limits range between 0.03 and 0.08 ng (depending on the compound), equivalent to 5 to 56 ppt in 1 l of sampled air. The method was tested by an intercomparison with a different gas chromatographic technique for the determination of NMHC. The system has been applied since 1994 for measurements in ambient air. Data obtained during an intensive campaign in summer 1995 at the field station Wank (1778 m a.s.l.) near Garmisch-Partenkirchen, Germany, are reported and compared with NMHC mixing ratios measured simultaneously in the same air masses.

  16. Simulating the oxygen content of ambient organic aerosol with the 2D volatility basis set

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    Murphy, B. N.; Donahue, N. M.; Fountoukis, C.; Pandis, S. N.

    2011-08-01

    A module predicting the oxidation state of organic aerosol (OA) has been developed using the two-dimensional volatility basis set (2D-VBS) framework. This model is an extension of the 1D-VBS framework and tracks saturation concentration and oxygen content of organic species during their atmospheric lifetime. The host model, a one-dimensional Lagrangian transport model, is used to simulate air parcels arriving at Finokalia, Greece during the Finokalia Aerosol Measurement Experiment in May 2008 (FAME-08). Extensive observations were collected during this campaign using an aerosol mass spectrometer (AMS) and a thermodenuder to determine the chemical composition and volatility, respectively, of the ambient OA. Although there are several uncertain model parameters, the consistently high oxygen content of OA measured during FAME-08 (O:C = 0.8) can help constrain these parameters and elucidate OA formation and aging processes that are necessary for achieving the high degree of oxygenation observed. The base-case model reproduces observed OA mass concentrations (measured mean = 3.1 μg m-3, predicted mean = 3.3 μg m-3) and O:C (predicted O:C = 0.78) accurately. A suite of sensitivity studies explore uncertainties due to (1) the anthropogenic secondary OA (SOA) aging rate constant, (2) assumed enthalpies of vaporization, (3) the volatility change and number of oxygen atoms added for each generation of aging, (4) heterogeneous chemistry, (5) the oxidation state of the first generation of compounds formed from SOA precursor oxidation, and (6) biogenic SOA aging. Perturbations in most of these parameters do impact the ability of the model to predict O:C well throughout the simulation period. By comparing measurements of the O:C from FAME-08, several sensitivity cases including a high oxygenation case, a low oxygenation case, and biogenic SOA aging case are found to unreasonably depict OA aging, keeping in mind that this study does not consider possibly important processes

  17. Simulating the oxygen content of ambient organic aerosol with the 2D volatility basis set

    Directory of Open Access Journals (Sweden)

    B. N. Murphy

    2011-08-01

    Full Text Available A module predicting the oxidation state of organic aerosol (OA has been developed using the two-dimensional volatility basis set (2D-VBS framework. This model is an extension of the 1D-VBS framework and tracks saturation concentration and oxygen content of organic species during their atmospheric lifetime. The host model, a one-dimensional Lagrangian transport model, is used to simulate air parcels arriving at Finokalia, Greece during the Finokalia Aerosol Measurement Experiment in May 2008 (FAME-08. Extensive observations were collected during this campaign using an aerosol mass spectrometer (AMS and a thermodenuder to determine the chemical composition and volatility, respectively, of the ambient OA. Although there are several uncertain model parameters, the consistently high oxygen content of OA measured during FAME-08 (O:C = 0.8 can help constrain these parameters and elucidate OA formation and aging processes that are necessary for achieving the high degree of oxygenation observed. The base-case model reproduces observed OA mass concentrations (measured mean = 3.1 μg m−3, predicted mean = 3.3 μg m−3 and O:C (predicted O:C = 0.78 accurately. A suite of sensitivity studies explore uncertainties due to (1 the anthropogenic secondary OA (SOA aging rate constant, (2 assumed enthalpies of vaporization, (3 the volatility change and number of oxygen atoms added for each generation of aging, (4 heterogeneous chemistry, (5 the oxidation state of the first generation of compounds formed from SOA precursor oxidation, and (6 biogenic SOA aging. Perturbations in most of these parameters do impact the ability of the model to predict O:C well throughout the simulation period. By comparing measurements of the O:C from FAME-08, several sensitivity cases including a high oxygenation case, a low oxygenation case, and biogenic SOA aging case are found to unreasonably depict OA aging, keeping in mind that this study does not consider

  18. Increased ratio of electron transport to net assimilation rate supports elevated isoprenoid emission rate in eucalypts under drought.

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    Dani, Kaidala Ganesha Srikanta; Jamie, Ian McLeod; Prentice, Iain Colin; Atwell, Brian James

    2014-10-01

    Plants undergoing heat and low-CO2 stresses emit large amounts of volatile isoprenoids compared with those in stress-free conditions. One hypothesis posits that the balance between reducing power availability and its use in carbon assimilation determines constitutive isoprenoid emission rates in plants and potentially even their maximum emission capacity under brief periods of stress. To test this, we used abiotic stresses to manipulate the availability of reducing power. Specifically, we examined the effects of mild to severe drought on photosynthetic electron transport rate (ETR) and net carbon assimilation rate (NAR) and the relationship between estimated energy pools and constitutive volatile isoprenoid emission rates in two species of eucalypts: Eucalyptus occidentalis (drought tolerant) and Eucalyptus camaldulensis (drought sensitive). Isoprenoid emission rates were insensitive to mild drought, and the rates increased when the decline in NAR reached a certain species-specific threshold. ETR was sustained under drought and the ETR-NAR ratio increased, driving constitutive isoprenoid emission until severe drought caused carbon limitation of the methylerythritol phosphate pathway. The estimated residual reducing power unused for carbon assimilation, based on the energetic status model, significantly correlated with constitutive isoprenoid emission rates across gradients of drought (r(2) > 0.8) and photorespiratory stress (r(2) > 0.9). Carbon availability could critically limit emission rates under severe drought and photorespiratory stresses. Under most instances of moderate abiotic stress levels, increased isoprenoid emission rates compete with photorespiration for the residual reducing power not invested in carbon assimilation. A similar mechanism also explains the individual positive effects of low-CO2, heat, and drought stresses on isoprenoid emission.

  19. Regolith and Environment Science and Oxygen and Lunar Volatile Extraction (RESOLVE): Lunar Advanced Volatile Analysis (LAVA) Integration and Testing - Evaluation of Lee Valve

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    Bower, Hannah; Cryderman, Kate; Captain, Janine

    2016-01-01

    The Resource Prospector (RP) mission with the Regolith and Environment Science and Oxygen and Lunar Volatile Extraction (RESOLVE) payload will prospect for water within the lunar regolith and provide a proof of concept for In-Situ Resource Utilization (ISRU) techniques, which could be used on future lunar and Martian missions. One system within the RESOLVE payload is the Lunar Advanced Volatiles Analysis (LAVA) subsystem, which consists of a Fluid Sub System (FSS) that transports volatiles to the Gas Chromatograph-Mass Spectrometer (GC-MS) instrument. In order for the FSS to transport precise and accurate amounts of volatiles to the GC-MS instrumentation, high performance valves are used within the system. The focus of this investigation is to evaluate the redesigned Lee valve. Further work is needed to continue to evaluate the Lee valve. Initial data shows that the valve could meet our requirements however further work is required to raise the TRL to an acceptable level to be included in the flight design of the system. At this time the risk is too high to change our baseline design to include these non-latching Lee solenoid valves.

  20. Microlayer source of oxygenated volatile organic compounds in the summertime marine Arctic boundary layer

    Science.gov (United States)

    Mungall, Emma L.; Abbatt, Jonathan P. D.; Wentzell, Jeremy J. B.; Lee, Alex K. Y.; Thomas, Jennie L.; Blais, Marjolaine; Gosselin, Michel; Miller, Lisa A.; Papakyriakou, Tim; Willis, Megan D.; Liggio, John

    2017-06-01

    Summertime Arctic shipboard observations of oxygenated volatile organic compounds (OVOCs) such as organic acids, key precursors of climatically active secondary organic aerosol (SOA), are consistent with a novel source of OVOCs to the marine boundary layer via chemistry at the sea surface microlayer. Although this source has been studied in a laboratory setting, organic acid emissions from the sea surface microlayer have not previously been observed in ambient marine environments. Correlations between measurements of OVOCs, including high levels of formic acid, in the atmosphere (measured by an online high-resolution time-of-flight mass spectrometer) and dissolved organic matter in the ocean point to a marine source for the measured OVOCs. That this source is photomediated is indicated by correlations between the diurnal cycles of the OVOC measurements and solar radiation. In contrast, the OVOCs do not correlate with levels of isoprene, monoterpenes, or dimethyl sulfide. Results from box model calculations are consistent with heterogeneous chemistry as the source of the measured OVOCs. As sea ice retreats and dissolved organic carbon inputs to the Arctic increase, the impact of this source on the summer Arctic atmosphere is likely to increase. Globally, this source should be assessed in other marine environments to quantify its impact on OVOC and SOA burdens in the atmosphere, and ultimately on climate.

  1. Contribution of understorey vegetation and soil processes to boreal forest isoprenoid exchange

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    Mäki, Mari; Heinonsalo, Jussi; Hellén, Heidi; Bäck, Jaana

    2017-03-01

    Boreal forest floor emits biogenic volatile organic compounds (BVOCs) from the understorey vegetation and the heterogeneous soil matrix, where the interactions of soil organisms and soil chemistry are complex. Earlier studies have focused on determining the net exchange of VOCs from the forest floor. This study goes one step further, with the aim of separately determining whether the photosynthesized carbon allocation to soil affects the isoprenoid production by different soil organisms, i.e., decomposers, mycorrhizal fungi, and roots. In each treatment, photosynthesized carbon allocation through roots for decomposers and mycorrhizal fungi was controlled by either preventing root ingrowth (50 µm mesh size) or the ingrowth of roots and fungi (1 µm mesh) into the soil volume, which is called the trenching approach. Isoprenoid fluxes were measured using dynamic (steady-state flow-through) chambers from the different treatments. This study aimed to analyze how important the understorey vegetation is as a VOC sink. Finally, a statistical model was constructed based on prevailing temperature, seasonality, trenching treatments, understory vegetation cover, above canopy photosynthetically active radiation (PAR), soil water content, and soil temperature to estimate isoprenoid fluxes. The final model included parameters with a statistically significant effect on the isoprenoid fluxes. The results show that the boreal forest floor emits monoterpenes, sesquiterpenes, and isoprene. Monoterpenes were the most common group of emitted isoprenoids, and the average flux from the non-trenched forest floor was 23 µg m-2 h-1. The results also show that different biological factors, including litterfall, carbon availability, biological activity in the soil, and physico-chemical processes, such as volatilization and absorption to the surfaces, are important at various times of the year. This study also discovered that understorey vegetation is a strong sink of monoterpenes. The

  2. Thermodynamics of Volatile Species in the Silicon-Oxygen-Hydrogen System Studied

    Science.gov (United States)

    Jacobson, Nathan S.; Opila, Elizabeth J.; Copland, Evan H.; Myers, Dwight

    2005-01-01

    The volatilization of silica (SiO2) to silicon hydroxides and oxyhydroxides because of reaction with water vapor is important in a variety of high-temperature corrosion processes. For example, the lifetimes of silicon carbide (SiC) and silicon nitride (Si3N4) - based components in combustion environments are limited by silica volatility. To understand and model this process, it is essential to have accurate thermodynamic data for the formation of volatile silicon hydroxides and oxyhydroxides.

  3. Double bond stereochemistry influences the susceptibility of short-chain isoprenoids and polyprenols to decomposition by thermo-oxidation.

    Science.gov (United States)

    Molińska, Ewa; Klimczak, Urszula; Komaszyło, Joanna; Derewiaka, Dorota; Obiedziński, Mieczysław; Kania, Magdalena; Danikiewicz, Witold; Swiezewska, Ewa

    2015-04-01

    Isoprenoid alcohols are common constituents of living cells. They are usually assigned a role in the adaptation of the cell to environmental stimuli, and this process might give rise to their oxidation by reactive oxygen species. Moreover, cellular isoprenoids may also undergo various chemical modifications resulting from the physico-chemical treatment of the tissues, e.g., heating during food processing. Susceptibility of isoprenoid alcohols to heat treatment has not been studied in detail so far. In this study, isoprenoid alcohols differing in the number of isoprene units and geometry of the double bonds, β-citronellol, geraniol, nerol, farnesol, solanesol and Pren-9, were subjected to thermo-oxidation at 80 °C. Thermo-oxidation resulted in the decomposition of the tested short-chain isoprenoids as well as medium-chain polyprenols with simultaneous formation of oxidized derivatives, such as hydroperoxides, monoepoxides, diepoxides and aldehydes, and possible formation of oligomeric derivatives. Oxidation products were monitored by GC-FID, GC-MS, ESI-MS and spectrophotometric methods. Interestingly, nerol, a short-chain isoprenoid with a double bond in the cis (Z) configuration, was more oxidatively stable than its trans (E) isomer, geraniol. However, the opposite effect was observed for medium-chain polyprenols, since Pren-9 (di-trans-poly-cis-prenol) was more susceptible to thermo-oxidation than its all-trans isomer, solanesol. Taken together, these results experimentally confirm that both short- and long-chain polyisoprenoid alcohols are prone to thermo-oxidation.

  4. Regolith and Environment Science and Oxygen and Lunar Volatile Extraction (RESOLVE): Lunar Advanced Volatile Analysis (LAVA) Capillary Fluid Dynamic Restriction Effects on Gas Chromatography

    Science.gov (United States)

    Gonzalez, Marianne; Quinn, Jacqueline; Captain, Janine; Santiago-Bond, Josephine; Starr, Stanley

    2015-01-01

    The Resource Prospector (RP) mission with the Regolith and Environment Science and Oxygen Lunar Volatile Extraction (RESOLVE) payload aims to show the presence of water in lunar regolith, and establish a proving ground for NASAs mission to Mars. One of the analysis is performed by the Lunar Advanced Volatiles Analysis (LAVA) subsystem, which consists of a fluid network that facilitates the transport of volatile samples to a gas chromatograph and mass spectrometer (GC-MS) instrument. The understanding of fluid dynamics directed from the GC to the MS is important due to the influence of flow rates and pressures that affect the accuracy of and prevent the damage to the overall GC-MS instrument. The micro-scale capillary fluid network within the GC alone has various lengths and inner-diameters; therefore, determination of pressure differentials and flow rates are difficult to model computationally, with additional complexity from the vacuum conditions in space and lack of a lunar atmosphere. A series of tests were performed on an experimental set-up of the system where the inner diameters of the GC transfer line connecting to the MS were varied. The effect on chromatography readings were also studied by applying these lines onto a GC instrument. It was found that a smaller inner diameter transfer line resulted in a lower flow rate, as well as a lower pressure differential across the thermal conductivity detector (TCD) unit of the GC and a negligible pressure drop across the mock-up capillary column. The chromatography was affected with longer retention times and broader peak integrations. It was concluded that a 0.050 mm inner diameter line still proved most suitable for the systems flow rate preferences. In addition, it was evident that this small transfer line portrayed some expense to GC signal characteristics and the wait time for steady-state operation.

  5. Process based inventory of isoprenoid emissions from European forests: model comparisons, current knowledge and uncertainties

    Directory of Open Access Journals (Sweden)

    T. Keenan

    2009-03-01

    Full Text Available Large uncertainties exist in our knowledge of regional emissions of non-methane biogenic volatile organic compounds (BVOC. We address these uncertainties through a two-pronged approach by compiling a state of the art database of the emissions potentials for 80 European forest species, and by a model assessment and inter-comparison, both at the local and regional scale, under present and projected future climatic conditions. We coupled three contrasting isoprenoid models with the ecophysiological forest model GOTILWA+ to explore the interactive effects of climate, vegetation distribution, and productivity, on leaf and ecosystem isoprenoid emissions, and to consider model behaviour in present climate and under projected future climate change conditions. Hourly, daily and annual isoprene emissions as simulated by the models were evaluated against flux measurements. The validation highlighted a general model capacity to capture gross fluxes but inefficiencies in capturing short term variability. A regional inventory of isoprenoid emissions for European forests was created using each of the three modelling approaches. The models agreed on an average European emissions budget of 1.03 TgC a−1 for isoprene and 0.97 TgC a−1 for monoterpenes for the period 1960–1990, which was dominated by a few species with largest aerial coverage. Species contribution to total emissions depended both on species emission potential and geographical distribution. For projected future climate conditions, however, emissions budgets proved highly model dependent, illustrating the current uncertainty associated with isoprenoid emissions responses to potential future conditions. These results suggest that current model estimates of isoprenoid emissions concur well, but future estimates are highly uncertain. We conclude that development of reliable models is highly urgent, but for the time being, future BVOC emission scenario estimates should consider

  6. Complex Ancestries of Isoprenoid Synthesis in Dinoflagellates.

    Science.gov (United States)

    Bentlage, Bastian; Rogers, Travis S; Bachvaroff, Tsvetan R; Delwiche, Charles F

    2016-01-01

    Isoprenoid metabolism occupies a central position in the anabolic metabolism of all living cells. In plastid-bearing organisms, two pathways may be present for de novo isoprenoid synthesis, the cytosolic mevalonate pathway (MVA) and nuclear-encoded, plastid-targeted nonmevalonate pathway (DOXP). Using transcriptomic data we find that dinoflagellates apparently make exclusive use of the DOXP pathway. Using phylogenetic analyses of all DOXP genes we inferred the evolutionary origins of DOXP genes in dinoflagellates. Plastid replacements led to a DOXP pathway of multiple evolutionary origins. Dinoflagellates commonly referred to as dinotoms due to their relatively recent acquisition of a diatom plastid, express two completely redundant DOXP pathways. Dinoflagellates with a tertiary plastid of haptophyte origin, by contrast, express a hybrid pathway of dual evolutionary origin. Here, changes in the targeting motif of signal/transit peptide likely allow for targeting the new plastid by the proteins of core isoprenoid metabolism proteins. Parasitic dinoflagellates of the Amoebophyra species complex appear to have lost the DOXP pathway, suggesting that they may rely on their host for sterol synthesis.

  7. Volatilization of elemental mercury from fresh blast furnace sludge mixed with basic oxygen furnace sludge under different temperatures.

    Science.gov (United States)

    Földi, Corinna; Dohrmann, Reiner; Mansfeldt, Tim

    2015-11-01

    Blast furnace sludge (BFS) is a waste with elevated mercury (Hg) content due to enrichment during the production process of pig iron. To investigate the volatilization potential of Hg, fresh samples of BFS mixed with basic oxygen furnace sludge (BOFS; a residue of gas purification from steel making, processed simultaneously in the cleaning devices of BFS and hence mixed with BFS) were studied in sealed column experiments at different temperatures (15, 25, and 35 °C) for four weeks (total Hg: 0.178 mg kg(-1)). The systems were regularly flushed with ambient air (every 24 h for the first 100 h, followed by every 72 h) for 20 min at a flow rate of 0.25 ± 0.03 L min(-1) and elemental Hg vapor was trapped on gold coated sand. Volatilization was 0.276 ± 0.065 ng (x m: 0.284 ng) at 15 °C, 5.55 ± 2.83 ng (x m: 5.09 ng) at 25 °C, and 2.37 ± 0.514 ng (x m: 2.34 ng) at 35 °C. Surprisingly, Hg fluxes were lower at 35 than 25 °C. For all temperature variants, an elevated Hg flux was observed within the first 100 h followed by a decrease of volatilization thereafter. However, the background level of ambient air was not achieved at the end of the experiments indicating that BFS mixed with BOFS still possessed Hg volatilization potential.

  8. Observations of nonmethane hydrocarbons and oxygenated volatile organic compounds at a rural site in the southeastern United States

    Science.gov (United States)

    Riemer, Daniel; Pos, Willer; Milne, Peter; Farmer, Charles; Zika, Rod; Apel, Eric; Olszyna, Ken; Kliendienst, Tad; Lonneman, William; Bertman, Steve; Shepson, Paul; Starn, Tim

    1998-11-01

    Measurements of an extensive range of nonmethane hydrocarbons (NMHCs) including alkanes, alkenes, and aromatics, and oxygenated volatile organic compounds (OVOCs) including alcohols, ketones, and aldehydes were conducted for several weeks during the summer of 1995 as part of the Southern Oxidants Study (SOS) at a rural experimental site (Youth, Inc.) 32 km southeast of Nashville, Tennessee, in the southeastern United States. These measurements were conducted to (1) determine the absolute magnitude and variability of oxygenated compounds found in a contemporary rural region; (2) assess the importance of the measured ambient levels of OVOCs on a photochemical reactivity basis relative to the more commonly determined NMHCs; and (3) to evaluate our ability to accurately measure oxygenates by the current techniques employed under a field study scenario. Several other physical (temperature, insolation, etc.), meteorological (wind velocity, wind direction, atmospheric structure, and boundary layer height), and chemical (criterion pollutants, NOx, SO2, CO, O3, etc.) parameters were measured concurrently with the NMHC and OVOC measurements. During the study period, OVOCs were consistently the dominant compounds present, and methanol and acetone had the highest mixing ratios. Although OVOCs made up the majority of the volatile organic compound component on a mass basis, a substantial sink for OH was isoprene and its immediate oxidation products, methacrolein and methyl vinyl ketone. In combination with CO and formaldehyde, these compounds comprised about 85% of the observed OH reactivity at the site. Acetaldehyde and methanol were responsible for an additional 10%, with the NMHCs and remaining OVOCs making up the final 5% of the measured OH reactivity at the site. These observed patterns reinforce recent studies which find OVOCs to be an important component of the rural troposphere.

  9. Isoprenoid Pathway And Neurological And Psychiatric Disorders

    Directory of Open Access Journals (Sweden)

    Ravikumar A

    1999-01-01

    Full Text Available The coexistence of neuronal degeneration, psychiatric manifestation, immune activation and malignant transformation has been documented in literature, suggesting a central dysfunction in the pathophysiology of these disorders. The isoprenoid pathway may be candidate in this respect, in view of the changes in the concentration of some products of this pathway in many of these disorders, however, no detailed study has been carried out in this respect. In view of this, a study was undertaken on the isoprenoid pathway in some of these disorders - primary generalized epilepsy, Parkinson’s disease (PD, schizophrenia, manic depressive psychosis (MDP, CNS glioma, multiple sclerosis, subacute sclerosing panencephalitis (SSPEand a familial group with familial coexistence of schizophrenia, PD, primary generalized epilepsy, malignant neoplasia, rheumatoid arthritis and syndrome-X over three generations. The following parameters were studied in the patients of these disorders as compared to age and sex matched control subjects - ubiquinone dolichol, digoxin, activity of HMG CoA reductase in the plasma and erthyorcyte membrane Na -K--ATpase. Increase in the activity of HMG CoA reductase and in the concentration of plasma digoxin and dolichol was observed in most of these cases. On the other hand, there was decrease in the concentration of plasma ubiquinone. Decrease in the activity of erythrocyte membrane Na-K- ATpase activity for which digoxin is an inhibitor was also observed in all the cases studied. These results indicate an upregulation of the isoprenoid pathway in the neurological and psychiatric disorders studied. The implications of this change is discussed in details.

  10. Sensitivity of global biogenic isoprenoid emissions to climate variability and atmospheric CO2

    Science.gov (United States)

    Naik, Vaishali; Delire, Christine; Wuebbles, Donald J.

    2004-03-01

    Isoprenoids (isoprene and monoterpenes) are the most dominant class of biogenic volatile organic compounds (BVOCs) and have been shown to significantly affect global tropospheric chemistry and composition, climate, and the global carbon cycle. In this study we assess the sensitivity of biogenic isoprene and monoterpene emissions to combined and isolated fluctuations in observed global climate and atmospheric carbon dioxide (CO2) concentration during the period 1971-1990. We integrate surface emission algorithms within the framework of a dynamic global ecosystem model, the Integrated Biospheric Simulator (IBIS), to simulate biogenic fluxes of isoprenoids as a component of the climate-vegetation dynamics. IBIS predicts global land surface isoprene emissions of 454 Tg C and monoterpenes of 72 Tg C annually and captures the spatial and temporal patterns well. The combined fluctuations in climate and atmospheric CO2 during 1971-1990 caused significant interannual and seasonal variability in global biogenic isoprenoid fluxes that was somewhat related to the El Niño-Southern Oscillation. Furthermore, an increasing trend in the simulated emissions was seen during this period that is attributed partly to the warming trend and partly to CO2 fertilization effect. The isolated effect of increasing CO2 during this period was to steadily increase emissions as a result of increases in foliar biomass. These fluctuations in biogenic emissions could have significant impacts on regional and global atmospheric chemistry and the global carbon budget.

  11. Volatile Release and Ignition Behaviors of Single Coal Particles at Different Oxygen Concentrations Under Microgravity

    Science.gov (United States)

    Liu, Bing; Zhang, Zhezi; Zhang, Hai; Zhang, Dongke

    2016-05-01

    An experimental study on ignition and combustion of single coal particles under different O 2 concentrations was conducted at both normal (1-g) and microgravity ( μ-g) in the first time. The surface and centre temperatures of the bituminous coal particle with initial diameter of ˜ 2.0mm were measured by the monochromatic imaging technique using a short wavelength infrared (SWIR) camera and an embedded fine thermocouple respectively. Results revealed that at μ-g, ignition of the tested coal particles was homogeneous. O 2 concentration significantly affects the shape, ignition temperature and ignition delay time of the volatile flames. A mathematical model considering thermal conduction inside the coal particle was developed to describe the ignition process of single particle, adopting the volatile matter flammability limit as the homogeneous ignition criterion. The predicted ignition temperatures were slightly lower but closer to μ-g data. And the predicted variation trends of ignition temperature and delay time under different O 2 concentrations agreed well with the μ-g experimental results.

  12. Identification of oxygen containing volatiles in cephalic secretions of workers of Brazilian stingless bees

    Directory of Open Access Journals (Sweden)

    Francke Wittko

    2000-01-01

    Full Text Available The volatile constituents of cephalic secrections of 11 Brazilian social stingless bee species of the Tetragonisca - Tetragona line have been analysed. By gas chromatography/mass spectrometry 145 compounds could be identified which include 72 esters, 22 alcohols, 16 carboxylic acids, 13 terpenoids, 8 aldehydes, 7 ketones, 4 aromatic compounds, 2 lactones and 1 dihydropyran. Structural relations, origin, and distribution of these compounds are discussed. With respect to qualitative and quantitative composition, each species shows a specific odour pattern which is made up by less specific components. To a certain extent, closely related species show some similarities in the odour bouquets. The mass spectrometric fragmentation patterns of typical wax type esters and DMDS derivatives of unsaturated esters are discussed in detail.

  13. Formation of highly oxygenated low-volatility products from cresol oxidation

    Science.gov (United States)

    Schwantes, Rebecca H.; Schilling, Katherine A.; McVay, Renee C.; Lignell, Hanna; Coggon, Matthew M.; Zhang, Xuan; Wennberg, Paul O.; Seinfeld, John H.

    2017-03-01

    Hydroxyl radical (OH) oxidation of toluene produces ring-retaining products: cresol and benzaldehyde, and ring-opening products: bicyclic intermediate compounds and epoxides. Here, first- and later-generation OH oxidation products from cresol and benzaldehyde are identified in laboratory chamber experiments. For benzaldehyde, first-generation ring-retaining products are identified, but later-generation products are not detected. For cresol, low-volatility (saturation mass concentration, C* ˜ 3.5 × 104 - 7.7 × 10-3 µg m-3), first- and later-generation ring-retaining products are identified. Subsequent OH addition to the aromatic ring of o-cresol leads to compounds such as hydroxy, dihydroxy, and trihydroxy methyl benzoquinones and dihydroxy, trihydroxy, tetrahydroxy, and pentahydroxy toluenes. These products are detected in the gas phase by chemical ionization mass spectrometry (CIMS) and in the particle phase using offline direct analysis in real-time mass spectrometry (DART-MS). Our data suggest that the yield of trihydroxy toluene from dihydroxy toluene is substantial. While an exact yield cannot be reported as authentic standards are unavailable, we find that a yield for trihydroxy toluene from dihydroxy toluene of ˜ 0.7 (equal to the reported yield of dihydroxy toluene from o-cresol; Olariu et al., 2002) is consistent with experimental results for o-cresol oxidation under low-NO conditions. These results suggest that even though the cresol pathway accounts for only ˜ 20 % of the oxidation products of toluene, it is the source of a significant fraction (˜ 20-40 %) of toluene secondary organic aerosol (SOA) due to the formation of low-volatility products.

  14. Structure and Dynamics of the Isoprenoid Pathway Network

    Institute of Scientific and Technical Information of China (English)

    Eva Vranová; Diana Coman; Wilhelm Gruissem

    2012-01-01

    Isoprenoids are functionally and structurally the most diverse group of plant metabolites reported to date.They can function as primary metabolites,participating in essential plant cellular processes,and as secondary metabolites,of which many have substantial commercial,pharmacological,and agricultural value.Isoprenoid end products participate in plants in a wide range of physiological processes acting in them both synergistically,such as chlorophyll and carotenoids during photosynthesis,or antagonistically,such as gibberellic acid and abscisic acid during seed germination.It is therefore expected that fluxes via isoprenoid metabolic network are tightly controlled both temporally and spatially,and that this control occurs at different levels of regulation and in an orchestrated manner over the entire isoprenoid metabolic network.In this review,we summarize our current knowledge of the topology of the plant isoprenoid pathway network and its regulation at the gene expression level following diverse stimuli.We conclude by discussing agronomical and biotechnological applications emerging from the plant isoprenoid metabolism and provide an outlook on future directions in the systems analysis of the plant isoprenoid pathway network.

  15. Isoprenoid drugs, biofuels, and chemicals--artemisinin, farnesene, and beyond.

    Science.gov (United States)

    George, Kevin W; Alonso-Gutierrez, Jorge; Keasling, Jay D; Lee, Taek Soon

    2015-01-01

    Isoprenoids have been identified and used as natural pharmaceuticals, fragrances, solvents, and, more recently, advanced biofuels. Although isoprenoids are most commonly found in plants, researchers have successfully engineered both the eukaryotic and prokaryotic isoprenoid biosynthetic pathways to produce these valuable chemicals in microorganisms at high yields. The microbial synthesis of the precursor to artemisinin--an important antimalarial drug produced from the sweet wormwood Artemisia annua--serves as perhaps the most successful example of this approach. Through advances in synthetic biology and metabolic engineering, microbial-derived semisynthetic artemisinin may soon replace plant-derived artemisinin as the primary source of this valuable pharmaceutical. The richness and diversity of isoprenoid structures also make them ideal candidates for advanced biofuels that may act as "drop-in" replacements for gasoline, diesel, and jet fuel. Indeed, the sesquiterpenes farnesene and bisabolene, monoterpenes pinene and limonene, and hemiterpenes isopentenol and isopentanol have been evaluated as fuels or fuel precursors. As in the artemisinin project, these isoprenoids have been produced microbially through synthetic biology and metabolic engineering efforts. Here, we provide a brief review of the numerous isoprenoid compounds that have found use as pharmaceuticals, flavors, commodity chemicals, and, most importantly, advanced biofuels. In each case, we highlight the metabolic engineering strategies that were used to produce these compounds successfully in microbial hosts. In addition, we present a current outlook on microbial isoprenoid production, with an eye towards the many challenges that must be addressed to achieve higher yields and industrial-scale production.

  16. A Comparison of the Volatile Carbon-Oxygen Chemistry in Several Oort Cloud Comets

    Science.gov (United States)

    DiSanti, M. A.; Dello Russo, N.; Magee-Sauer, K.; Gibb, E. L.; Reuter, D. C.; Xu, L.-H.; Mumma, M. J.

    2002-09-01

    Since 1996, we have conducted detailed studies of the abundances of parent volatiles in 8 Oort Cloud comets using modern long-slit echelle spectrometers having sensitivity in the 1 - 5 μ m spectral region. These instruments (CSHELL at the NASA-IRTF, and NIRSPEC at Keck 2) have sufficiently high spectral resolution ( ν / Δ ν ~ 2 x 104 ) to resolve individual cometary emission lines. Their small pixel sizes provide the high angular resolution necessary for detailed study of the spatial distribution of emissions in the coma. Here we inter-compare our results for the chemically-linked molecules carbon monoxide (CO), formaldehyde (H2CO), and methyl alcohol (CH3OH) among our sample of comets. Such a study can provide clues as to the processing history of the ice. Measuring the relative abundances of these molecules can provide a test of the efficiency of conversion of CO, for example through hydrogen addition on icy grain mantles or by radiation processing in the dense cloud core. Comparisons with fluorescence models and/or laboratory measurements will also be presented where appropriate. This work is supported by NASA Planetary Astronomy Program grants NAG5-7905 and NAG5-12208 to M. A. DiSanti, and RTOP 693-344-32-30-07 to M. J. Mumma.

  17. Metabolic engineering for isoprenoid-based biofuel production.

    Science.gov (United States)

    Gupta, P; Phulara, S C

    2015-09-01

    Sustainable economic and industrial growth is the need of the hour and it requires renewable energy resources having better performance and compatibility with existing fuel infrastructure from biological routes. Isoprenoids (C ≥ 5) can be a potential alternative due to their diverse nature and physiochemical properties similar to that of petroleum based fuels. In the past decade, extensive research has been done to utilize metabolic engineering strategies in micro-organisms primarily, (i) to overcome the limitations associated with their natural and non-natural production and (ii) to develop commercially competent microbial strain for isoprenoid-based biofuel production. This review briefly describes the engineered isoprenoid biosynthetic pathways in well-characterized microbial systems for the production of several isoprenoid-based biofuels and fuel precursors.

  18. Directed Evolution towards Increased Isoprenoid Production in Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Carlsen, Simon; Nielsen, Michael Lynge; Kielland-Brandt, Morten

    population of S. cerevisiae clones will afterwards be screened using the isoprenoid molecule lycopene as a model compound, hereby enabling the isolation of phenotypes producing higher amounts of isoprenoid. The property making lycopene ideal for screening is its system of 11 conjugated double bonds, which...... absorbs light within the visible range resulting in the red color of lycopene. This feature is the cause for the orange/red phenotype of S. cerevisiae strains transformed with the genes encoding lycopene and enables visual screening of yeast colonies, by searching for colonies with more intense red colony...... coloration which is the result of higher amount of lycopene is being produced and hence high amount of isoprenoid precursor being available. This will elucidate novel genetic targets for increasing isoprenoid production in S. cerevisiae...

  19. Combined effects of reduced malaxation oxygen levels and storage time on extra-virgin olive oil volatiles investigated by a novel chemometric approach.

    Science.gov (United States)

    Raffo, Antonio; Bucci, Remo; D'Aloise, Antonio; Pastore, Gianni

    2015-09-01

    Combined effects of oxygen level reduction in the malaxation headspace and storage time up to 6 months on the volatile composition of a monovarietal extra-virgin olive oil (EVOO), obtained from cv. Carboncella olives, were investigated by applying a full factorial design approach (4 oxygen levels × 4 storage times) on EVOOs extracted on an industrial scale in two mills, equipped with "two-phase" and "three-phase" centrifugation systems, respectively. The outcoming data were analysed by the chemometric technique called ANOVA-simultaneous component analysis (ASCA). Both reduction of oxygen malaxation levels and storage time significantly affected the volatile profile of the extracted EVOOs. Reduction of oxygen malaxation levels hindered the formation of lipoxygenase derived volatiles (hexanal, 1-hexanol, (Z)-2-hexenal, (E)-2-hexen-1-ol, (Z)-2-penten-1-ol, 2,4-hexadienals), whereas prolonged storage times were associated with increased levels of autoxidation products (octane, hexanal, C10 hydrocarbons) and other compounds that could originate from exogenous microbial activity (1-octen-3-ol, 6-methyl-5-hepten-2-one, benzaldehyde, methyl salicylate).

  20. Feed-derived volatile basic nitrogen increases reactive oxygen species production of blood leukocytes in lactating dairy cows.

    Science.gov (United States)

    Tsunoda, Ei; Gross, Josef J; Kawashima, Chiho; Bruckmaier, Rupert M; Kida, Katsuya; Miyamoto, Akio

    2017-01-01

    The present study investigated over 9 months the changes of fermentative quality of total mixed rations (TMR) containing grass silage (GS) as a major component, associated with changes in the volatile basic nitrogen (VBN) levels in an experimental dairy farm. Effects of VBN levels in TMR on metabolic parameters, reactive oxygen species (ROS) production by blood polymorphonuclear leukocytes (PMNs) and conception rates for dairy cows were analyzed. According to VBN levels in TMR during survey periods, three distinct phases were identified; phase A with low VBN; phase B with high VBN; and phase C with mid-VBN. Metabolic parameters in blood were all within normal range. However, during phases B and C, nitrogen metabolic indices such as blood urea nitrogen and milk urea nitrogen showed higher levels compared to those in phase A, and a simultaneous increase in ROS production by blood PMNs and the load on hepatic function in metabolic parameters was observed in the cows with a lower conception rate. This suggests that feeding TMR with elevated VBN levels due to poor fermented GS results in stimulation of ROS production by PMNs by ammonia, and negatively affects metabolism and reproductive performance in lactating dairy cow.

  1. Synthetic Routes to Methylerythritol Phosphate Pathway Intermediates and Downstream Isoprenoids

    Science.gov (United States)

    Jarchow-Choy, Sarah K; Koppisch, Andrew T; Fox, David T

    2014-01-01

    Isoprenoids constitute the largest class of natural products with greater than 55,000 identified members. They play essential roles in maintaining proper cellular function leading to maintenance of human health, plant defense mechanisms against predators, and are often exploited for their beneficial properties in the pharmaceutical and nutraceutical industries. Most impressively, all known isoprenoids are derived from one of two C5-precursors, isopentenyl diphosphate (IPP) or dimethylallyl diphosphate (DMAPP). In order to study the enzyme transformations leading to the extensive structural diversity found within this class of compounds there must be access to the substrates. Sometimes, intermediates within a biological pathway can be isolated and used directly to study enzyme/pathway function. However, the primary route to most of the isoprenoid intermediates is through chemical catalysis. As such, this review provides the first exhaustive examination of synthetic routes to isoprenoid and isoprenoid precursors with particular emphasis on the syntheses of intermediates found as part of the 2C-methylerythritol 4-phosphate (MEP) pathway. In addition, representative syntheses are presented for the monoterpenes (C10), sesquiterpenes (C15), diterpenes (C20), triterpenes (C30) and tetraterpenes (C40). Finally, in some instances, the synthetic routes to substrate analogs found both within the MEP pathway and downstream isoprenoids are examined. PMID:25009443

  2. Variation in short-term and long-term responses of photosynthesis and isoprenoid-mediated photoprotection to soil water availability in four Douglas-fir provenances.

    Science.gov (United States)

    Junker, Laura Verena; Kleiber, Anita; Jansen, Kirstin; Wildhagen, Henning; Hess, Moritz; Kayler, Zachary; Kammerer, Bernd; Schnitzler, Jörg-Peter; Kreuzwieser, Jürgen; Gessler, Arthur; Ensminger, Ingo

    2017-01-10

    For long-lived forest tree species, the understanding of intraspecific variation among populations and their response to water availability can reveal their ability to cope with and adapt to climate change. Dissipation of excess excitation energy, mediated by photoprotective isoprenoids, is an important defense mechanism against drought and high light when photosynthesis is hampered. We used 50-year-old Douglas-fir trees of four provenances at two common garden experiments to characterize provenance-specific variation in photosynthesis and photoprotective mechanisms mediated by essential and non-essential isoprenoids in response to soil water availability and solar radiation. All provenances revealed uniform photoprotective responses to high solar radiation, including increased de-epoxidation of photoprotective xanthophyll cycle pigments and enhanced emission of volatile monoterpenes. In contrast, we observed differences between provenances in response to drought, where provenances sustaining higher CO2 assimilation rates also revealed increased water-use efficiency, carotenoid-chlorophyll ratios, pools of xanthophyll cycle pigments, β-carotene and stored monoterpenes. Our results demonstrate that local adaptation to contrasting habitats affected chlorophyll-carotenoid ratios, pool sizes of photoprotective xanthophylls, β-carotene, and stored volatile isoprenoids. We conclude that intraspecific variation in isoprenoid-mediated photoprotective mechanisms contributes to the adaptive potential of Douglas-fir provenances to climate change.

  3. Variation in short-term and long-term responses of photosynthesis and isoprenoid-mediated photoprotection to soil water availability in four Douglas-fir provenances

    Science.gov (United States)

    Junker, Laura Verena; Kleiber, Anita; Jansen, Kirstin; Wildhagen, Henning; Hess, Moritz; Kayler, Zachary; Kammerer, Bernd; Schnitzler, Jörg-Peter; Kreuzwieser, Jürgen; Gessler, Arthur; Ensminger, Ingo

    2017-01-01

    For long-lived forest tree species, the understanding of intraspecific variation among populations and their response to water availability can reveal their ability to cope with and adapt to climate change. Dissipation of excess excitation energy, mediated by photoprotective isoprenoids, is an important defense mechanism against drought and high light when photosynthesis is hampered. We used 50-year-old Douglas-fir trees of four provenances at two common garden experiments to characterize provenance-specific variation in photosynthesis and photoprotective mechanisms mediated by essential and non-essential isoprenoids in response to soil water availability and solar radiation. All provenances revealed uniform photoprotective responses to high solar radiation, including increased de-epoxidation of photoprotective xanthophyll cycle pigments and enhanced emission of volatile monoterpenes. In contrast, we observed differences between provenances in response to drought, where provenances sustaining higher CO2 assimilation rates also revealed increased water-use efficiency, carotenoid-chlorophyll ratios, pools of xanthophyll cycle pigments, β-carotene and stored monoterpenes. Our results demonstrate that local adaptation to contrasting habitats affected chlorophyll-carotenoid ratios, pool sizes of photoprotective xanthophylls, β-carotene, and stored volatile isoprenoids. We conclude that intraspecific variation in isoprenoid-mediated photoprotective mechanisms contributes to the adaptive potential of Douglas-fir provenances to climate change. PMID:28071755

  4. Growth regulating properties of isoprene and isoprenoid-based essential oils.

    Science.gov (United States)

    Jones, Andrew Maxwell P; Shukla, Mukund R; Sherif, Sherif M; Brown, Paula B; Saxena, Praveen K

    2016-01-01

    Essential oils have growth regulating properties comparable to the well-documented methyl jasmonate and may be involved in localized and/or airborne plant communication. Aromatic plants employ large amounts of resources to produce essential oils. Some essential oils are known to contain compounds with plant growth regulating activities. However, the potential capacity of essential oils as airborne molecules able to modulate plant growth/development has remained uninvestigated. Here, we demonstrate that essential oils from eight taxonomically diverse plants applied in their airborne state inhibited auxin-induced elongation of Pisum sativum hypocotyls and Avena sativa coleoptiles. This response was also observed using five monoterpenes commonly found in essential oils as well as isoprene, the basic building block of terpenes. Upon transfer to ambient conditions, A. sativa coleoptiles resumed elongation, demonstrating an antagonistic relationship rather than toxicity. Inclusion of essential oils, monoterpenes, or isoprene into the headspace of culture vessels induced abnormal cellular growth along hypocotyls of Arabidopsis thaliana. These responses were also elicited by methyl jasmonate (MeJA); however, where methyl jasmonate inhibited root growth essential oils did not. Gene expression studies in A. thaliana also demonstrated differences between the MeJA and isoprenoid responses. This series of experiments clearly demonstrate that essential oils and their isoprenoid components interact with endogenous plant growth regulators when applied directly or as volatile components in the headspace. The similarities between isoprenoid and MeJA responses suggest that they may act in plant defence signalling. While further studies are needed to determine the ecological and evolutionary significance, the results of this study and the specialized anatomy associated with aromatic plants suggest that essential oils may act as airborne signalling molecules.

  5. Hydrogen peroxide enhances the oxidation of oxygenated volatile organic compounds on mineral dust particles: a case study of methacrolein.

    Science.gov (United States)

    Zhao, Yue; Huang, Dao; Huang, Liubin; Chen, Zhongming

    2014-09-16

    Heterogeneous oxidation of oxygenated volatile organic compounds (OVOCs) serves as an important sink of OVOCs as well as a source of secondary organic material. However, the roles of gas phase oxidants in these reactions are poorly understood. In this work, we present the first laboratory study of the heterogeneous reactions of methacrolein (MACR) on various mineral dust particles in the presence of gaseous H2O2. It is found that the presence of gaseous H2O2 significantly promotes both the uptake and oxidation of MACR on kaolinite, α-Al2O3, α-Fe2O3, and TiO2, but not on CaCO3. The oxidation of MACR produces organic acids as its major low-molecular-weight product, whose yields are enhanced by a factor of 2-6 in the presence of H2O2. In addition, organic peroxides such as methyl hydroperoxide, peroxyformic acid, and peroxyacetic acid are only formed in the presence of H2O2, and the formation of methyl hydroperoxide indicates that MACR oxidation on the surface involves reaction with OH radicals. A probe reaction using salicylic acid verifies the production of OH radicals from H2O2 decomposition on kaolinite, α-Al2O3, α-Fe2O3, and TiO2, which rationalizes the enhanced MACR oxidation observed on these particles. The uptake coefficients of MACR on kaolinite, α-Fe2O3, and TiO2 in the presence of H2O2 are on the order of 10(-5)-10(-4). Our results provide new insights into the formation and chemical evolution of organic species in the atmosphere.

  6. Investigations into the effects of volatile biomass tar on the performance of Fe-based CLC oxygen carrier materials

    Science.gov (United States)

    Boot-Handford, Matthew E.; Florin, Nick; Fennell, Paul S.

    2016-11-01

    In this study we present findings from investigations into interactions between biomass tar and two iron based oxygen carrier materials (OCMs) designed for chemical-looping applications: a 100% Fe2O3 (100Fe) OCM and a 60 wt% Fe2O3/40 wt% Al2O3 (60Fe40Al) OCM. A novel 6 kWe two-stage, fixed-bed reactor was designed and constructed to simulate a chemical-looping combustion (CLC) process with ex situ gasification of biomass. Beech wood was pyrolysed in the first stage of the reactor at 773 K to produce a tar-containing fuel gas that was used to reduce the OCM loaded into the 2nd stage at 973 K. The presence of either OCM was found to significantly reduce the amount of biomass tars exiting the reactor by up to 71 wt% compared with analogous experiments in which the biomass tar compounds were exposed to an inert bed of sand. The tar cracking effect of the 60Fe40Al OCM was slightly greater than the 100Fe OCM although the reduction in the tar yield was roughly equivalent to the increase in carbon deposition observed for the 60Fe40Al OCM compared with the 100Fe OCM. In both cases, the tar cracking effect of the OCMs appeared to be independent of the oxidation state in which the OCM was exposed to the volatile biomass pyrolysis products (i.e. Fe2O3 or Fe3O4). Exposing the pyrolysis vapours to the OCMs in their oxidised (Fe2O3) form favoured the production of CO2. The production of CO was favoured when the OCMs were in their reduced (Fe3O4) form. Carbon deposition was removed in the subsequent oxidation phase with no obvious deleterious effects on the reactivity in subsequent CLC cycles with reduction by 3 mol% CO.

  7. Oxygenated volatile organic carbon in the western Pacific convective center: ocean cycling, air–sea gas exchange and atmospheric transport

    Directory of Open Access Journals (Sweden)

    C. Schlundt

    2017-09-01

    Full Text Available A suite of oxygenated volatile organic compounds (OVOCs – acetaldehyde, acetone, propanal, butanal and butanone were measured concurrently in the surface water and atmosphere of the South China Sea and Sulu Sea in November 2011. A strong correlation was observed between all OVOC concentrations in the surface seawater along the entire cruise track, except for acetaldehyde, suggesting similar sources and sinks in the surface ocean. Additionally, several phytoplankton groups, such as haptophytes or pelagophytes, were also correlated to all OVOCs, indicating that phytoplankton may be an important source of marine OVOCs in the South China and Sulu seas. Humic- and protein-like fluorescent dissolved organic matter (FDOM components seemed to be additional precursors for butanone and acetaldehyde. The measurement-inferred OVOC fluxes generally showed an uptake of atmospheric OVOCs by the ocean for all gases, except for butanal. A few important exceptions were found along the Borneo coast, where OVOC fluxes from the ocean to the atmosphere were inferred. The atmospheric OVOC mixing ratios over the northern coast of Borneo were relatively high compared with literature values, suggesting that this coastal region is a local hotspot for atmospheric OVOCs. The calculated amount of OVOCs entrained into the ocean seemed to be an important source of OVOCs to the surface ocean. When the fluxes were out of the ocean, marine OVOCs were found to be enough to control the locally measured OVOC distribution in the atmosphere. Based on our model calculations, at least 0.4 ppb of marine-derived acetone and butanone can reach the upper troposphere, where they may have an important influence on hydrogen oxide radical formation over the western Pacific Ocean.

  8. Stereochemical studies of acyclic isoprenoids-XII. Lipids of methanogenic bacteria and possible contributions to sediments

    Science.gov (United States)

    Risatti, J.B.; Rowland, S.J.; Yon, D.A.; Maxwell, J.R.

    1984-01-01

    Abundant volatile lipids of Methanobacterium thermoautotrophicum and Methanosarcina barkeri include isoprenoid hydrocarbons (??? C30), and C15, C20 and C25 isoprenoid alcohols. M. barkeri contains 2,6,10,15,19-pentamethyleicosane, whose relative stereochemistry is the same as found in marine sediments, indicating that it is a marker of methanogenic activity. The C20, C30 and C25 alkenes in M. thermoautotrophicum also have a preferred sterochemistry; the latter have the 2,6,10,14,18-pentamethyleicosanyl skeleton, suggesting that the alkane in marine sediments may derive from methanogens. The stereochemistry of squalane in a marine sediment is also compatible with an origin in methanogens; in contrast, the stereochemistry of pristane in M. thermoautotrophicum indicates a fossil fuel contaminant origin, suggesting that this and certain other alkanes reported in archaebacteria might also be of contaminant origin. There is, therefore, little evidence at present that the pristane in immature marine sediments originates in methanogens. The C15 and C20 saturated alcohols in M. thermoautotrophicum have mainly the all-R configuration. If this is generally true for methanogens, the C20 alcohol in the Messel shale may originate mainly from methanogens, whereas that in the Green River shale may originate mainly from photosynthetic organisms. ?? 1984.

  9. Inhibition of volatile compounds derived from fatty acid oxygenation with chilling and heating treatments and their influences on the oxylipin pathawy gene expression and enzyme activity levels in tomato (Solanum lycopersicon

    Science.gov (United States)

    Hexanal, Z-3-hexenal, E-2-hexenal, hexanol and Z-3-hexenol are major tomato (Solanum Lycopersicon) volatile aromas derived from oxygenation of unsaturated fatty acids. Chilling or heating treatments suppress production of these C6 volatiles. The objective of this research was to determine the respon...

  10. An enzymatic platform for the synthesis of isoprenoid precursors.

    Directory of Open Access Journals (Sweden)

    Sofia B Rodriguez

    Full Text Available The isoprenoid family of compounds is estimated to contain ∼ 65,000 unique structures including medicines, fragrances, and biofuels. Due to their structural complexity, many isoprenoids can only be obtained by extraction from natural sources, an inherently risky and costly process. Consequently, the biotechnology industry is attempting to genetically engineer microorganisms that can produce isoprenoid-based drugs and fuels on a commercial scale. Isoprenoid backbones are constructed from two, five-carbon building blocks, isopentenyl 5-pyrophosphate and dimethylallyl 5-pyrophosphate, which are end-products of either the mevalonate or non-mevalonate pathways. By linking the HMG-CoA reductase pathway (which produces mevalonate to the mevalonate pathway, these building block can be synthesized enzymatically from acetate, ATP, NAD(PH and CoA. Here, the enzymes in these pathways are used to produce pathway intermediates and end-products in single-pot reactions and in remarkably high yield, ∼ 85%. A strategy for the regio-specific incorporation of isotopes into isoprenoid backbones is developed and used to synthesize a series of isotopomers of diphosphomevalonate, the immediate end-product of the mevalonate pathway. The enzymatic system is shown to be robust and capable of producing quantities of product in aqueous solutions that meet or exceed the highest levels achieved using genetically engineered organisms in high-density fermentation.

  11. A highly spatially resolved GIS-based model to assess the isoprenoid emissions from key Italian ecosystems

    Science.gov (United States)

    Pacheco, Claudia Kemper; Fares, Silvano; Ciccioli, Paolo

    2014-10-01

    The amount of Biogenic Volatile Organic Compounds (BVOC) emitted from terrestrial vegetation is of great importance in atmospheric reactivity, particularly for ozone-forming reactions and as condensation nuclei in aerosol formation and growth. This work presents a detailed inventory of isoprenoid emissions from vegetation in Italy using an original approach which combines state of the art models to estimate the species-specific isoprenoid emissions and a Geographic Information System (GIS) where emissions are spatially represented. Isoprenoid species and basal emission factors were obtained by combining results from laboratory experiments with those published in literature. For the first time, our investigation was not only restricted to isoprene and total monoterpenes, but our goal was to provide maps of isoprene and individual monoterpenes at a high-spatial (˜1 km2) and temporal resolution (daily runs, monthly trends in emissions are discussed in the text). Another novelty in our research was the inclusion of the effects of phenology on plant emissions. Our results show that: a) isoprene, a-pinene, sabinene and b-pinene are the most important compounds emitted from vegetation in Italy; b) annual biogenic isoprene and monoterpene fluxes for the year 2006 were ˜31.30 Gg and ˜37.70 Gg, respectively; and c) Quercus pubescens + Quercus petrea + Quercus robur, Quercus ilex, Quercus suber and Fagus sylvatica are the principal isoprenoid emitting species in the country. The high spatial and temporal resolution, combined with the species-specific emission output, makes the model particularly suitable for assessing local budgets, and for modeling photochemical pollution in Italy.

  12. Isoprenoid biosynthesis in Archaea - Biochemical and evolutionary implications

    NARCIS (Netherlands)

    Matsumi, Rie; Atomi, Haruyuki; Driessen, Arnold J. M.; van der Oost, John

    Isoprenoids are indispensable for all types of cellular life in the Archaea, Bacteria, and Eucarya. These membrane-associated molecules are involved in a wide variety of vital biological functions, ranging from compartmentalization and stability, to protection and energy-transduction. In Archaea,

  13. The isoprenoid-precursor dependence of Plasmodium spp

    NARCIS (Netherlands)

    van der Meer, Jan-Ytzen; Hirsch, Anna K. H.

    2012-01-01

    Due to the increase in resistance of Plasmodium spp. against available antimalarials, there is a need for new, effective and innovative drugs. The non-mevalonate pathway for the biosynthesis of the universal isoprenoid precursors, which is absent in humans, is suggested as an attractive source of

  14. Isoprenoid biosynthesis in Archaea - Biochemical and evolutionary implications

    NARCIS (Netherlands)

    Matsumi, Rie; Atomi, Haruyuki; Driessen, Arnold J. M.; van der Oost, John

    2011-01-01

    Isoprenoids are indispensable for all types of cellular life in the Archaea, Bacteria, and Eucarya. These membrane-associated molecules are involved in a wide variety of vital biological functions, ranging from compartmentalization and stability, to protection and energy-transduction. In Archaea, is

  15. The isoprenoid-precursor dependence of Plasmodium spp

    NARCIS (Netherlands)

    van der Meer, Jan-Ytzen; Hirsch, Anna K. H.

    2012-01-01

    Due to the increase in resistance of Plasmodium spp. against available antimalarials, there is a need for new, effective and innovative drugs. The non-mevalonate pathway for the biosynthesis of the universal isoprenoid precursors, which is absent in humans, is suggested as an attractive source of ta

  16. Negative Feedbacks by Isoprenoids on a Mevalonate Kinase Expressed in the Corpora Allata of Mosquitoes.

    Directory of Open Access Journals (Sweden)

    Pratik Nyati

    Full Text Available Juvenile hormones (JH regulate development and reproductive maturation in insects. JHs are synthesized through the mevalonate pathway (MVAP, an ancient metabolic pathway present in the three domains of life. Mevalonate kinase (MVK is a key enzyme in the MVAP. MVK catalyzes the synthesis of phosphomevalonate (PM by transferring the γ-phosphoryl group from ATP to the C5 hydroxyl oxygen of mevalonic acid (MA. Despite the importance of MVKs, these enzymes have been poorly characterized in insects.We functionally characterized an Aedes aegypti MVK (AaMVK expressed in the corpora allata (CA of the mosquito. AaMVK displayed its activity in the presence of metal cofactors. Different nucleotides were used by AaMVK as phosphoryl donors. In the presence of Mg(2+, the enzyme has higher affinity for MA than ATP. The activity of AaMVK was regulated by feedback inhibition from long-chain isoprenoids, such as geranyl diphosphate (GPP and farnesyl diphosphate (FPP.AaMVK exhibited efficient inhibition by GPP and FPP (Ki less than 1 μM, and none by isopentenyl pyrophosphate (IPP and dimethyl allyl pyrophosphate (DPPM. These results suggest that GPP and FPP might act as physiological inhibitors in the synthesis of isoprenoids in the CA of mosquitoes. Changing MVK activity can alter the flux of precursors and therefore regulate juvenile hormone biosynthesis.

  17. Advances in the Plant Isoprenoid Biosynthesis Pathway and Its Metabolic Engineering

    Institute of Scientific and Technical Information of China (English)

    Yan LIU; Hong WANG; He-Chun YE; Guo-Feng LI

    2005-01-01

    Although the cytosolic isoprenoid biosynthetic pathway, mavolonate pathway, in plants has been known for many years, a new plastidial 1-deoxyxylulose-5-phosphate (DXP) pathway was identified in the past few years and its related intermediates, enzymes, and genes have been characterized quite recently.With a deep insight into the biosynthetic pathway of isoprenoids, investigations into the metabolic engineering of isoprenoid biosynthesis have started to prosper. In the present article, recent advances in the discoveries and regulatory roles of new genes and enzymes in the plastidial isoprenoid biosynthesis path way are reviewed and examples of the metabolic engineering of cytosolic and plastidial isoprenoids biosnthesis are discussed.

  18. Metabolic engineering and synthetic biology approaches driving isoprenoid production in Escherichia coli.

    Science.gov (United States)

    Wang, Chonglong; Zada, Bakht; Wei, Gongyuan; Kim, Seon-Won

    2017-10-01

    Isoprenoids comprise the largest family of natural organic compounds with many useful applications in the pharmaceutical, nutraceutical, and industrial fields. Rapid developments in metabolic engineering and synthetic biology have facilitated the engineering of isoprenoid biosynthetic pathways in Escherichia coli to induce high levels of production of many different isoprenoids. In this review, the stem pathways for synthesizing isoprene units as well as the branch pathways deriving diverse isoprenoids from the isoprene units have been summarized. The review also highlights the metabolic engineering efforts made for the biosynthesis of hemiterpenoids, monoterpenoids, sesquiterpenoids, diterpenoids, carotenoids, retinoids, and coenzyme Q10 in E. coli. Perspectives and future directions for the synthesis of novel isoprenoids, decoration of isoprenoids using cytochrome P450 enzymes, and secretion or storage of isoprenoids in E. coli have also been included. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. On-line derivatization for hourly measurements of gas- and particle-phase Semi-Volatile oxygenated organic compounds by Thermal desorption Aerosol Gas chromatography (SV-TAG

    Directory of Open Access Journals (Sweden)

    G. Isaacman

    2014-07-01

    Full Text Available Laboratory oxidation studies have identified a large number of oxygenated organic compounds that can be used as tracers to understand sources and oxidation chemistry of atmospheric particulate matter. Quantification of these compounds in ambient environments has traditionally relied on low time-resolution collection of filter samples followed by offline sample treatment with a derivatizing agent to allow analysis by gas chromatography of otherwise non-elutable organic chemicals with hydroxyl groups. We present here an automated in situ instrument for the measurement of highly polar organic semi-volatile and low-volatility compounds in both the gas- and particle-phase with hourly time-resolution. The dual-cell Semi-Volatile Thermal desorption Aerosol Gas chromatograph (SV-TAG with derivatization collects particle-only and combined particle-plus-vapor samples on two parallel sampling cells that are analyzed in series by thermal desorption into helium saturated with derivatizing agent. Introduction of MSTFA, a silylating agent, yields complete derivatization of all tested compounds, including alkanoic acids, polyols, diacids, sugars, and multifunctional compounds. In laboratory tests, derivatization is found to be highly reproducible (< 3% variability. During field deployment, a regularly injected internal standard is used to correct for variability in detector response, derivatization efficiency, desorption efficiency, and transfer efficiency. Error in quantification from instrument fluctuations is found to be less than 10% for hydrocarbons and less than 15% for all oxygenates for which a functionally similar internal standard is available. After internal standard corrections, calibration curves are found to be linear for all compounds over the span of one month with comparable response on both of the parallel sampling cells.

  20. Online derivatization for hourly measurements of gas- and particle-phase semi-volatile oxygenated organic compounds by thermal desorption aerosol gas chromatography (SV-TAG)

    Science.gov (United States)

    Isaacman, G.; Kreisberg, N. M.; Yee, L. D.; Worton, D. R.; Chan, A. W. H.; Moss, J. A.; Hering, S. V.; Goldstein, A. H.

    2014-12-01

    Laboratory oxidation studies have identified a large number of oxygenated organic compounds that can be used as tracers to understand sources and oxidation chemistry of atmospheric particulate matter. Quantification of these compounds in ambient environments has traditionally relied on low-time-resolution collection of filter samples followed by offline sample treatment with a derivatizing agent to allow analysis by gas chromatography of otherwise non-elutable organic chemicals with hydroxyl groups. We present here an automated in situ instrument for the measurement of highly polar organic semi-volatile and low-volatility compounds in both the gas- and particle-phase with hourly quantification of mass concentrations and gas-particle partitioning. The dual-cell semi-volatile thermal desorption aerosol gas chromatograph (SV-TAG) with derivatization collects particle-only and combined particle-plus-vapor samples on two parallel sampling cells that are analyzed in series by thermal desorption into helium saturated with derivatizing agent. Introduction of MSTFA (N-methyl-N-(trimethylsilyl)trifluoroacetamide), a silylating agent, yields complete derivatization of all tested compounds, including alkanoic acids, polyols, diacids, sugars, and multifunctional compounds. In laboratory tests, derivatization is found to be highly reproducible (regularly injected internal standard is used to correct for variability in detector response, consumption of the derivatization agent, desorption efficiency, and transfer losses. Error in quantification from instrument fluctuations is found to be less than 10% for hydrocarbons and less than 15% for all oxygenates for which a functionally similar internal standard is available, with an uncertainty of 20-25% in measurements of particle fraction. After internal standard corrections, calibration curves are found to be linear for all compounds over the span of 1 month, with comparable response on both of the parallel sampling cells.

  1. On-line derivatization for hourly measurements of gas- and particle-phase Semi-Volatile oxygenated organic compounds by Thermal desorption Aerosol Gas chromatography (SV-TAG)

    Science.gov (United States)

    Isaacman, G.; Kreisberg, N. M.; Yee, L. D.; Worton, D. R.; Chan, A. W. H.; Moss, J. A.; Hering, S. V.; Goldstein, A. H.

    2014-07-01

    Laboratory oxidation studies have identified a large number of oxygenated organic compounds that can be used as tracers to understand sources and oxidation chemistry of atmospheric particulate matter. Quantification of these compounds in ambient environments has traditionally relied on low time-resolution collection of filter samples followed by offline sample treatment with a derivatizing agent to allow analysis by gas chromatography of otherwise non-elutable organic chemicals with hydroxyl groups. We present here an automated in situ instrument for the measurement of highly polar organic semi-volatile and low-volatility compounds in both the gas- and particle-phase with hourly time-resolution. The dual-cell Semi-Volatile Thermal desorption Aerosol Gas chromatograph (SV-TAG) with derivatization collects particle-only and combined particle-plus-vapor samples on two parallel sampling cells that are analyzed in series by thermal desorption into helium saturated with derivatizing agent. Introduction of MSTFA, a silylating agent, yields complete derivatization of all tested compounds, including alkanoic acids, polyols, diacids, sugars, and multifunctional compounds. In laboratory tests, derivatization is found to be highly reproducible (regularly injected internal standard is used to correct for variability in detector response, derivatization efficiency, desorption efficiency, and transfer efficiency. Error in quantification from instrument fluctuations is found to be less than 10% for hydrocarbons and less than 15% for all oxygenates for which a functionally similar internal standard is available. After internal standard corrections, calibration curves are found to be linear for all compounds over the span of one month with comparable response on both of the parallel sampling cells.

  2. Application of dispersive liquid-liquid microextraction and gas chromatography with mass spectrometry for the determination of oxygenated volatile organic compounds in effluents from the production of petroleum bitumen.

    Science.gov (United States)

    Boczkaj, Grzegorz; Makoś, Patrycja; Przyjazny, Andrzej

    2016-07-01

    We present a new procedure for the determination of oxygenated volatile organic compounds in samples of postoxidative effluents from the production of petroleum bitumens using dispersive liquid-liquid microextraction and gas chromatography with mass spectrometry. The eight extraction parameters were optimized for 43 oxygenated volatile organic compounds. The detection limits obtained ranged from 0.07 to 0.82 μg/mL for most of the analytes, the precision was good (relative standard deviation below 2.91% at the 5 μg/mL level and 4.75% at the limit of quantification), the recoveries for the majority of compounds varied from 70.6 to 118.9%, and the linear range was wide, which demonstrates the usefulness of the procedure. The developed procedure was used for the determination of oxygenated volatile organic compounds in samples of raw postoxidative effluents and in effluents after chemical treatment. In total, 23 compounds at concentration levels from 0.37 to 32.95 μg/mL were identified in real samples. The same samples were also analyzed in the SCAN mode, which resulted in four more phenol derivatives being identified and tentatively determined. The studies demonstrated the need for monitoring volatile organic compounds content in effluents following various treatments due to the formation of secondary oxygenated volatile organic compounds.

  3. Isoprenoid hydrocarbons in oil shales from the Aleksinac deposit

    Energy Technology Data Exchange (ETDEWEB)

    Saban, M.; Tesic, Z.; Vitorovic, D.

    1983-01-01

    It is established that the basic components of the fraction of branched and cyclic alkanes, isolated from shale bitumens, are aliphatic and polycyclic isoprenoid compounds. All members of the homological C15 to C20 series are identified among the aliphatic compounds, except for C17; C27 to C29 stearines and methyl to C29 styrene are discovered among the polycyclic compounds and C27 to C29 triterpenes and bicyclic tetraterpenes are identified among the pentacyclic compounds.

  4. Chemical composition, aroma evaluation, and oxygen radical absorbance capacity of volatile oil extracted from Brassica rapa cv. "yukina" used in Japanese traditional food.

    Science.gov (United States)

    Usami, Atsushi; Motooka, Ryota; Takagi, Ayumi; Nakahashi, Hiroshi; Okuno, Yoshiharu; Miyazawa, Mitsuo

    2014-01-01

    The chemical composition of the volatile oil extracted from the aerial parts of Brassica rapa cv. "yukina" was analyzed using GC-MS, GC-PFPD, and GC-O. A total of 50 compounds were identified. The most prominent constituents were (E)-1,5-heptadiene (40.27%), 3-methyl-3-butenenitrile (25.97%) and 3-phenylpropanenitrile (12.41%). With regard to aroma compounds, 12 compounds were identified by GC-O analysis. The main aroma-active compounds were dimethyl tetrasulfide (sulphury-cabbage, FD = 64), 3-phenylpropanenitrile (nutty, FD = 64), 3-methylindole (pungent, FD = 64), and methional (potato, FD = 32). The antioxidant activity of the aroma-active compounds of the oil was determined using an oxygen radical absorbance capacity (ORAC) assay using fluorescein as the fluorescent probe. The ORAC values were found to be 785 ± 67 trolox equivalents (μmol TE/g) for B. rapa cv. "yukina" oil. The results obtained showed that the volatile oil extracted from the aerial parts is a good dietary source of antioxidants.

  5. Influence of activated carbon porosity and surface oxygen functionalities' presence on adsorption of acetonitrile as a simple polar volatile organic compound.

    Science.gov (United States)

    Furmaniak, Sylwester

    2015-01-01

    Based on series of porous carbon models, systematic Monte Carlo studies on the adsorption of acetonitrile (as a simple representative of polar volatile organic compounds) were performed. The influence of porosity and chemical composition of the carbon surface on CH3CN adsorption was studied and it was shown that both the factors influenced the adsorption mechanism. A decrease in the pore size and the introduction of oxygen surface groups led to a rise in adsorption energy and to an increase in the filling of accessible volume in the low-pressure part of the isotherm. However, from a practical point of view, it is easier to increase the adsorption by introducing polar groups on the carbon surface than by modifying the porosity.

  6. Influence of oxygen and long term storage on the profile of volatile compounds released from polymeric multilayer food contact materials sterilized by gamma irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Salafranca, Jesús, E-mail: fjsl@unizar.es [Aragón Institute of Engineering Research (I3A), EINA, Department of Analytical Chemistry, University of Zaragoza, María de Luna 3 (Torres Quevedo Bldg.), 50018 Zaragoza (Spain); Clemente, Isabel, E-mail: isabelclemente1984@gmail.com [Aragón Institute of Engineering Research (I3A), EINA, Department of Analytical Chemistry, University of Zaragoza, María de Luna 3 (Torres Quevedo Bldg.), 50018 Zaragoza (Spain); Isella, Francesca, E-mail: Francesca.Isella@goglio.it [Goglio S.p.A. Packaging Division, Via dell' Industria 7, 21020 Daverio (Italy); Nerín, Cristina, E-mail: cnerin@unizar.es [Aragón Institute of Engineering Research (I3A), EINA, Department of Analytical Chemistry, University of Zaragoza, María de Luna 3 (Torres Quevedo Bldg.), 50018 Zaragoza (Spain); Bosetti, Osvaldo, E-mail: Osvaldo.Bosetti@goglio.it [Goglio S.p.A. Packaging Division, Via dell' Industria 7, 21020 Daverio (Italy)

    2015-06-09

    Highlights: • 13 different food-use multilayers unirradiated and gamma-irradiated were studied. • 60–80 compounds/sample were identified by SPME–GC–MS even after 8-month storage. • Volatile profile of air- and N{sub 2}-filled bags greatly differed after irradiation. • Principal component analysis classified the samples into 4 groups. • Migration from irradiated materials to vapor phase was much lower than EU limits. - Abstract: The profile of volatile compounds released from 13 different multilayer polymeric materials for food use, before and after their exposure to gamma radiation, has been assessed by solid-phase microextraction–gas chromatography–mass spectrometry. Thermosealed bags of different materials were filled with either air or nitrogen to evaluate the oxygen influence. One-third of the samples were analyzed without irradiation, whereas the rest were irradiated at 15 and 25 kGy. Half of the samples were processed just after preparation and the other half was stored for 8 months at room temperature prior to analysis. Very significant differences between unirradiated and irradiated bags were found. About 60–80 compounds were released and identified per sample. A huge peak of 1,3-ditertbutylbenzene was present in most of the irradiated samples. An outstanding reproducibility in all the variables evaluated (chromatograms, oxygen percentage, volume of bags) was noticed. Independently of filling gas, the results of unirradiated materials were almost identical. In contrast, the chromatographic profile and the odor of irradiated bags filled with nitrogen were completely different to those filled with air. Principal component analysis was performed and 86.9% of the accumulated variance was explained with the first two components. The migration of compounds from irradiated materials to the vapor phase was much lower than the limits established in the Commission Regulation (EU) No 10/2011.

  7. Hartmut Lichtenthaler: an authority on chloroplast structure and isoprenoid biochemistry.

    Science.gov (United States)

    Sharkey, Thomas D; Govindjee

    2016-05-01

    We pay tribute to Hartmut Lichtenthaler for making important contributions to the field of photosynthesis research. He was recently recognized for ground-breaking discoveries in chloroplast structure and isoprenoid biochemistry by the Rebeiz Foundation for Basic Research (RFBR; http://vlpbp.org/ ), receiving a 2014 Lifetime Achievement Award for Photosynthesis. The ceremony, held in Champaign, Illinois, was attended by many prominent researchers in the photosynthesis field. We provide below a brief note on his education, and then describe some of the areas in which Hartmut Lichtenthaler has been a pioneer.

  8. Distribution and evolution of isoprenoid in crude oil

    Energy Technology Data Exchange (ETDEWEB)

    Shanfa, F.; Shanchun, J.; Fenfang, X.

    1981-12-01

    By means of chromatography-mass spectrography and gas chromatography, isoprenoids (i15-i20) have been identified in 49 crude oil samples and 3 rock samples from oil fields in Shengli, Huabei, Subei, Dagang, Liaohe and Daqing and also from Sichuan, Gueizhou etc. The relative contents, in percentage of phytane (Ph), pristane (Pr), norpristane (i18), 2.6.10-trimethyl-tridecane (i16) and farnesane (i15) are determined, as well as the ratios of Pr/Ph, Pr/nC/sub 17/, Ph/nC/sub 18/ and i18 + i16 + i15/Ph + Pr. The curves of the relative contents of Ph, Pr, i18, i16 and i15 may show the character of different oils, useful for correlation purposes. The evolution of isoprenoids in crude oils is divided into sub-mature stage (Pr/Ph < 0.8, i18 + i16 + i15/Ph + Pr = 0.2 - 0.5); mature stage (Pr/Ph > 0.8, i18 + i16 + i15/Ph + Pr = 0.3 - 0.6) and highly mature stage (Pr/Ph > 1.0, i18 + i16 + i15/Ph + Pr > 0.6). 4 figures, 5 tables.

  9. Detection of non-sterol isoprenoids by HPLC-MS/MS

    Science.gov (United States)

    Henneman, Linda; van Cruchten, Arno G.; Denis, Simone W.; Amolins, Michael W.; Placzek, Andrew T.; Gibbs, Richard A.; Kulik, Willem; Waterham, Hans R.

    2012-01-01

    Isoprenoids constitute an important class of biomolecules that participate in many different cellular processes. Most available detection methods only allow the identification of one or two specific non-sterol isoprenoid intermediates following radioactive or fluorescent labeling. We here report a rapid, non-radioactive and sensitive procedure for the simultaneous detection and quantification of the 8 main non-sterol intermediates of the isoprenoid biosynthesis pathway by means of tandem mass spectrometry. Intermediates were analyzed by HPLC-MS/MS in the multiple reaction monitoring mode using a silica-based C18 HPLC column. For quantification, their stable-isotope-labeled analogues were used as internal standards. HepG2 cells were used to validate the method. Mevalonate, phosphomevalonate and the 6 subsequent isoprenoid-pyrophosphates were readily determined with detection limits ranging from 0.03 to 1.0 μmol/L. The intra- and interassay variations for HepG2 cell homogenates supplemented with isoprenoid intermediates were 3.6–10.9% and 4.4–11.9%, respectively. Under normal culturing conditions, isoprenoid intermediates in HepG2 cells were below detection limits. However, incubation of the cells with pamidronate, an inhibitor of farnesyl pyrophosphate synthase, resulted in increased levels of MVA, IPP/DMAPP and GPP. This method will be suitable to measure profiles of isoprenoid intermediates in cells with compromised isoprenoid biosynthesis, and to determine the specificity of potential inhibitors of the pathway. PMID:18782552

  10. The Non-Mevalonate Pathway to Isoprenoid Biosynthesis : A Potential Source of New Drug Targets

    NARCIS (Netherlands)

    Hirsch, Anna K.H.; Diederich, François

    2008-01-01

    Isoprenoids are an essential class of natural products with a myriad of biological functions. All isoprenoids are assembled using two common five-carbon precursors, isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) that are biosynthesized via two completely independent routes: the

  11. Volatile abundances and oxygen isotopes in basaltic to dacitic lavas on mid-ocean ridges: The role of assimilation at spreading centers

    Science.gov (United States)

    Wanless, V.D.; Perfit, M.R.; Ridley, W.I.; Wallace, P.J.; Grimes, Craig B.; Klein, E.M.

    2011-01-01

    Most geochemical variability in MOR basalts is consistent with low- to moderate-pressure fractional crystallization of various mantle-derived parental melts. However, our geochemical data from MOR high-silica glasses, including new volatile and oxygen isotope data, suggest that assimilation of altered crustal material plays a significant role in the petrogenesis of dacites and may be important in the formation of basaltic lavas at MOR in general. MOR high-silica andesites and dacites from diverse areas show remarkably similar major element trends, incompatible trace element enrichments, and isotopic signatures suggesting similar processes control their chemistry. In particular, very high Cl and elevated H2O concentrations and relatively light oxygen isotope ratios (~ 5.8‰ vs. expected values of ~ 6.8‰) in fresh dacite glasses can be explained by contamination of magmas from a component of ocean crust altered by hydrothermal fluids. Crystallization of silicate phases and Fe-oxides causes an increase in δ18O in residual magma, but assimilation of material initially altered at high temperatures results in lower δ18O values. The observed geochemical signatures can be explained by extreme fractional crystallization of a MOR basalt parent combined with partial melting and assimilation (AFC) of amphibole-bearing altered oceanic crust. The MOR dacitic lavas do not appear to be simply the extrusive equivalent of oceanic plagiogranites. The combination of partial melting and assimilation produces a distinct geochemical signature that includes higher incompatible trace element abundances and distinct trace element ratios relative to those observed in plagiogranites.

  12. Hybrid isoprenoid secondary metabolite production in terrestrial and marine actinomycetes.

    Science.gov (United States)

    Gallagher, Kelley A; Fenical, William; Jensen, Paul R

    2010-12-01

    Terpenoids are among the most ubiquitous and diverse secondary metabolites observed in nature. Although actinomycete bacteria are one of the primary sources of microbially derived secondary metabolites, they rarely produce compounds in this biosynthetic class. The terpenoid secondary metabolites that have been discovered from actinomycetes are often in the form of biosynthetic hybrids called hybrid isoprenoids (HIs). HIs include significant structural diversity and biological activity and thus are important targets for natural product discovery. Recent screening of marine actinomycetes has led to the discovery of a new lineage that is enriched in the production of biologically active HI secondary metabolites. These strains represent a promising resource for natural product discovery and provide unique opportunities to study the evolutionary history and ecological functions of an unusual group of secondary metabolites. Copyright © 2010 Elsevier Ltd. All rights reserved.

  13. Regulation of Isoprenoid Pheromone Biosynthesis in Bumblebee Males.

    Science.gov (United States)

    Prchalová, Darina; Buček, Aleš; Brabcová, Jana; Žáček, Petr; Kindl, Jiří; Valterová, Irena; Pichová, Iva

    2016-02-02

    Males of the closely related species Bombus terrestris and Bombus lucorum attract conspecific females by completely different marking pheromones. MP of B. terrestris and B. lucorum pheromones contain mainly isoprenoid (ISP) compounds and fatty acid derivatives, respectively. Here, we studied the regulation of ISP biosynthesis in both bumblebees. RNA-seq and qRT-PCR analyses indicated that acetoacetyl-CoA thiolase (AACT), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR), and farnesyl diphosphate synthase (FPPS) transcripts are abundant in the B. terrestris labial gland. Maximal abundance of these transcripts correlated well with AACT enzymatic activity detected in the LG extracts. In contrast, transcript abundances of AACT, HMGR, and FPPS in B. lucorum were low, and AACT activity was not detected in LGs. These results suggest that transcriptional regulation plays a key role in the control of ISP biosynthetic gene expression and ISP pheromone biosynthesis in bumblebee males.

  14. Technical Note: Performance of Chemical Ionization Reaction Time-of-Flight Mass Spectrometry (CIR-TOF-MS for the measurement of atmospherically significant oxygenated volatile organic compounds

    Directory of Open Access Journals (Sweden)

    K. P. Wyche

    2007-01-01

    Full Text Available The performance of a new chemical ionization reaction time-of-flight mass spectrometer (CIR-TOF-MS utilising the environment chamber SAPHIR (Simulation of Atmospheric Photochemistry In a large Reaction Chamber- Forschungzentrum Jülich, Germany is described. The work took place as part of the ACCENT (Atmospheric Composition and Change the European NeTwork for excellence supported oxygenated volatile organic compound (OVOC measurement intercomparison during January 2005. The experiment entailed the measurement of 14 different atmospherically significant OVOCs at various mixing ratios in the approximate range 10.0–0.6 ppbV. The CIR-TOF-MS operated throughout the exercise with the hydronium ion (H3O+ as the primary chemical ionization (CI reagent in order to facilitate proton transfer to the analyte OVOCs. The results presented show that the CIR time-of-flight mass spectrometer is capable of detecting a wide range of atmospheric OVOCs at mixing ratios of around 10 ppbV in "real-time" (i.e. detection on the one-minute time scale, with sub-ppbV measurement also achieved following an increase in averaging time to tens of minutes. It is shown that in general OVOC measurement is made with high accuracy and precision, with integration time, mixing ratio and compound dependent values as good as 4–13% and 3–15% respectively. It is demonstrated that CIR-TOF-MS has rapid multi-channel response at the required sensitivity, accuracy and precision for atmospheric OVOC measurement.

  15. Development of a parallel sampling and analysis method for the elucidation of gas/particle partitioning of oxygenated semi-volatile organics: a limonene ozonolysis study

    Directory of Open Access Journals (Sweden)

    S. Rossignol

    2012-06-01

    Full Text Available The gas/particle partitioning behaviour of the semi-volatile fraction of secondary organic matter and the associated multiphase chemistry are key features to accurately evaluate climate and health impacts of secondary organic aerosol (SOA. However, today, the partitioning of oxygenated secondary species is rarely assessed in experimental SOA studies and SOA modelling is still largely based on estimated partitioning data. This paper describes a new analytical approach, solvent-free and easy to use, to explore the chemical composition of the secondary organic matter at a molecular scale in both gas and particulate phases. The method is based on thermal desorption (TD of gas and particulate samples, coupled with gas chromatography (GC and mass spectrometry (MS, with derivatisation on sampling supports. Gaseous compounds were trapped on Tenax TA adsorbent tubes pre-coated with pentafluorobenzylhydroxylamine (PFBHA or N-Methyl-N-(t-butyldimethylsilyltrifluoroacetamide (MTBSTFA. Particulate samples were collected onto quartz or Teflon-quartz filters and subsequently subjected to derivatisation with PFBHA or MTBSTFA before TD-GC/MS analysis. Method development and validation are presented for an atmospherically relevant range of organic acids and carbonyl and hydroxyl compounds. Application of the method to a limonene ozonolysis experiment conducted in the EUPHORE simulation chamber under simulated atmospheric conditions of low concentrations of limonene precursor and relative humidity, provides an overview of the method capabilities. Twenty-five compounds were positively or tentatively identified, nine being in both gaseous and particulate phases; and twelve, among them tricarboxylic acids, hydroxyl dicarboxylic acids and oxodicarboxylic acids, being detected for the first time.

  16. Metabolic engineering by plastid transformation as a strategy to modulate isoprenoid yield in plants.

    Science.gov (United States)

    Hasunuma, Tomohisa; Kondo, Akihiko; Miyake, Chikahiro

    2010-01-01

    Plants synthesize a large number of isoprenoid compounds that have diverse structures and functions. All isoprenoids are synthesized through consecutive condensation of five-carbon precursors, isopentenyl diphosphate (IPP) and its allyl isomer dimethylallyl diphosphate (DMAPP). With recent success in the cloning of genes that encode the enzymes of isoprenoid biosynthesis, genetic engineering strategies for the improvement of plant isoprenoid metabolism have emerged. Plastid transformation technology offers attractive features in plant genetic engineering. It has many advantages over nuclear genome transformation: high-level foreign protein expression, no need for a transit peptide, absence of gene silencing, and convenient transgene stacking in operons. We demonstrated that this technology is a remarkable tool for the production of isoprenoids in plants through metabolic engineering. The expression of bacterial genes encoding CrtW (beta-carotene ketolase) and CrtZ (beta-carotene hydroxylase) or cyanobacterial genes encoding DXR (1-deoxy-D-xylulose-5-phosphate reductoisomerase) in the plastid genome leads to alteration in isoprenoid content of tobacco leaves.

  17. Volatile organic compound emissions from Larrea tridentata (creosotebush)

    Science.gov (United States)

    Jardine, K.; Abrell, L.; Kurc, S. A.; Huxman, T.; Ortega, J.; Guenther, A.

    2010-12-01

    We present results from the CREosote ATmosphere Interactions through Volatile Emissions (CREATIVE 2009) field study in southern Arizona aimed at quantifying emission rates of VOCs from creosotebush (Larrea tridentata) during the summer 2009 monsoon season. This species was chosen because of its vast distribution in North and South American deserts and because its resins have been reported to contain a rich set of volatile organic compounds (VOC). While a variety of ecosystems have been investigated for VOC emissions, deserts remain essentially unstudied, partially because of their low biomass densities and water limitations. However, during the North American monsoon, a pronounced increase in rainfall from an extremely dry June (80 mm) occurs over large areas of the Sonoran desert in the southwestern United States and northwestern Mexico. We observed a strong diurnal pattern of branch emissions and ambient concentrations of an extensive suite of VOCs with maxima in early afternoon. These include VOCs typically observed in forest sites (oxygenated VOCs and volatile isoprenoids) as well as a large number of other compounds, some of which have not been previously described from any plant including 1-chloro-2-methoxy-benzene and isobutyronitrile. Although generally considered to be derived from anthropogenic sources, we observed emissions of aromatic compounds including benzene, and a broad range of phenolics. Dimethyl sulfide emissions from creosotebush were higher than reported from any previously studied plant suggesting that terrestrial ecosystems should be reconsidered as an important source of this climatically important gas. We also present direct, primary emission measurements of isoprene and its apparent oxidation products methyl vinyl ketone, methacrolein, and 3-methyl furan (the later three compounds are typically assumed to form from secondary reactions within the atmosphere), as well as a group of compounds considered to be fatty acid oxidation products

  18. Volatile organic compound emissions from Larrea tridentata (creosotebush

    Directory of Open Access Journals (Sweden)

    J. Ortega

    2010-07-01

    Full Text Available The emission of Volatile Organic Compounds (VOCs from plants impacts both climate and air quality by fueling atmospheric chemistry and by contributing to aerosol particles. While a variety of ecosystems have been investigated for VOC emissions, deserts remain essentially unstudied, partially because of their low biomass densities and water limitations. However, during the North American monsoon, a pronounced increase in rainfall from an extremely dry June (<5 mm precipitation to a rainy July (>80 mm occurs over large areas of the Sonoran desert in the Southwestern United States and Northwestern Mexico. We present results from the CREosote ATmosphere Interactions through Volatile Emissions (CREATIVE 2009 field study in Southern Arizona aimed at quantifying emission rates of VOCs from creosotebush (Larrea tridentata during the summer 2009 monsoon season. This species was chosen because of its vast distribution in North and South American deserts and because its resins have been reported to contain a rich set of VOCs. We observed a strong diurnal pattern with branch emissions and ambient concentrations of an extensive suite of VOCs with maxima in early afternoon. These include VOCs typically observed in forest sites (oxygenated VOCs and volatile isoprenoids as well as a large number of other compounds, some of which have not been previously described from any plant including 1-chloro-2-methoxy-benzene and isobutyronitrile. Although generally considered to be derived from anthropogenic sources, we observed emissions of aromatic compounds including benzene, and a broad range of phenolics. Dimethyl sulfide emissions from creosotebush were higher than reported from any previously studied plant suggesting that terrestrial ecosystems should be reconsidered as an important source of this climatically important gas. We also present direct, primary emission measurements of isoprene and its apparent oxidation products methyl vinyl ketone, methacrolein, and 3

  19. Volatile organic compound emissions from Larrea tridentata (creosotebush

    Directory of Open Access Journals (Sweden)

    A. Guenther

    2010-12-01

    Full Text Available We present results from the CREosote ATmosphere Interactions through Volatile Emissions (CREATIVE 2009 field study in southern Arizona aimed at quantifying emission rates of VOCs from creosotebush (Larrea tridentata during the summer 2009 monsoon season. This species was chosen because of its vast distribution in North and South American deserts and because its resins have been reported to contain a rich set of volatile organic compounds (VOC. While a variety of ecosystems have been investigated for VOC emissions, deserts remain essentially unstudied, partially because of their low biomass densities and water limitations. However, during the North American monsoon, a pronounced increase in rainfall from an extremely dry June (80 mm occurs over large areas of the Sonoran desert in the southwestern United States and northwestern Mexico. We observed a strong diurnal pattern of branch emissions and ambient concentrations of an extensive suite of VOCs with maxima in early afternoon. These include VOCs typically observed in forest sites (oxygenated VOCs and volatile isoprenoids as well as a large number of other compounds, some of which have not been previously described from any plant including 1-chloro-2-methoxy-benzene and isobutyronitrile. Although generally considered to be derived from anthropogenic sources, we observed emissions of aromatic compounds including benzene, and a broad range of phenolics. Dimethyl sulfide emissions from creosotebush were higher than reported from any previously studied plant suggesting that terrestrial ecosystems should be reconsidered as an important source of this climatically important gas. We also present direct, primary emission measurements of isoprene and its apparent oxidation products methyl vinyl ketone, methacrolein, and 3-methyl furan (the later three compounds are typically assumed to form from secondary reactions within the atmosphere, as well as a group of compounds considered to be fatty acid

  20. Volatility Discovery

    DEFF Research Database (Denmark)

    Dias, Gustavo Fruet; Scherrer, Cristina; Papailias, Fotis

    The price discovery literature investigates how homogenous securities traded on different markets incorporate information into prices. We take this literature one step further and investigate how these markets contribute to stochastic volatility (volatility discovery). We formally show...... that the realized measures from homogenous securities share a fractional stochastic trend, which is a combination of the price and volatility discovery measures. Furthermore, we show that volatility discovery is associated with the way that market participants process information arrival (market sensitivity...

  1. Volatile Metabolites

    Directory of Open Access Journals (Sweden)

    Daryl D. Rowan

    2011-11-01

    Full Text Available Volatile organic compounds (volatiles comprise a chemically diverse class of low molecular weight organic compounds having an appreciable vapor pressure under ambient conditions. Volatiles produced by plants attract pollinators and seed dispersers, and provide defense against pests and pathogens. For insects, volatiles may act as pheromones directing social behavior or as cues for finding hosts or prey. For humans, volatiles are important as flavorants and as possible disease biomarkers. The marine environment is also a major source of halogenated and sulfur-containing volatiles which participate in the global cycling of these elements. While volatile analysis commonly measures a rather restricted set of analytes, the diverse and extreme physical properties of volatiles provide unique analytical challenges. Volatiles constitute only a small proportion of the total number of metabolites produced by living organisms, however, because of their roles as signaling molecules (semiochemicals both within and between organisms, accurately measuring and determining the roles of these compounds is crucial to an integrated understanding of living systems. This review summarizes recent developments in volatile research from a metabolomics perspective with a focus on the role of recent technical innovation in developing new areas of volatile research and expanding the range of ecological interactions which may be mediated by volatile organic metabolites.

  2. Impact of pollution controls in Beijing on atmospheric oxygenated volatile organic compounds (OVOCs during the 2008 Olympic Games: observation and modeling implications

    Directory of Open Access Journals (Sweden)

    Y. Liu

    2014-10-01

    Full Text Available Oxygenated volatile organic compounds (OVOCs are important products of the photo-oxidation of hydrocarbons. They influence the oxidizing capacity and the ozone forming potential of the atmosphere. In the summer of 2008 two months' emission restrictions were enforced in Beijing to improve air quality during the Olympic Games. Observation evidence has been reported in related studies that these control measures were efficient in reducing the concentrations of primary anthropogenic pollutants (CO, NOx and non-methane hydrocarbons, i.e. NMHCs by 30–40%. In this study, the influence of the emission restrictions on ambient levels of OVOCs was explored using a neural network analysis with consideration of meteorological conditions. Statistically significant reductions in formaldehyde (HCHO, acetaldehyde (CH3CHO, methyl ethyl ketone (MEK and methanol were found to be 12.9, 15.8, 17.1 and 19.6%, respectively, when the restrictions were in place. The effect of emission control on acetone was not detected in neural network simulations, probably due to pollution transport from surrounding areas outside Beijing. Although the ambient levels of most NMHCs were decreased by ~35% during the full control period, the emission ratios of reactive hydrocarbons attributed to vehicular emissions did not present obvious difference. A zero-dimensional box model based on Master Chemical Mechanism version 3.2 (MCM3.2 was applied to evaluate how OVOCs productions respond to the reduced precursors during the emission controlled period. On average, secondary HCHO was produced from the oxidation of anthropogenic alkenes (54%, isoprene (30% and aromatics (15%. The importance of biogenic source for the total HCHO formation was almost on a par with that of anthropogenic alkenes during the daytime. Anthropogenic alkenes and alkanes dominated the photochemical production of other OVOCs such as acetaldehyde, acetone and MEK. The relative changes of modelled aldehydes, methyl vinyl

  3. Volatile organic compounds from Italian vegetation and their interaction with ozone.

    Science.gov (United States)

    Calfapietra, Carlo; Fares, Silvano; Loreto, Francesco

    2009-05-01

    Volatile Organic Compounds (VOCs) emitted from vegetation (particularly isoprenoids) represent an important source of atmospheric hydrocarbons almost double the anthropogenic source. When biogenic VOC mix with NO(x) in the presence of UV radiation, ozone (O(3)) is formed. In Italy, optimal conditions for O(3) formation in terms of VOC/NO(x) ratios and abundance of UV radiation occur for long periods of the year. Moreover, Italian vegetation includes several species that are strong and evergreen isoprenoid emitters, and high temperatures for part of the year further stimulate these temperature-dependent emissions. We review emission of isoprenoids from Italian vegetation, current knowledge on the impact of rising O(3) levels on isoprenoid emission, and evidence showing that isoprenoids can increase both the O(3) flux to the plant and protection against oxidative stress because of their antioxidant functions. This trait not only influences plant tolerance to O(3) but also may substantially alter the flux of O(3) between atmosphere and biosphere.

  4. Isoprenoids and phenylpropanoids are part of the antioxidant defense orchestrated daily by drought-stressed Platanus × acerifolia plants during Mediterranean summers.

    Science.gov (United States)

    Tattini, Massimiliano; Loreto, Francesco; Fini, Alessio; Guidi, Lucia; Brunetti, Cecilia; Velikova, Violeta; Gori, Antonella; Ferrini, Francesco

    2015-08-01

    The hypothesis was tested that isoprenoids and phenylpropanoids play a prominent role in countering photooxidative stress, following the depletion of antioxidant enzyme activity in plants exposed to severe drought stress under high solar irradiance and high temperatures. Platanus × acerifolia, a high isoprene-emitting species, was drought-stressed during summer (WS) and compared with unstressed controls (WW). Water relations and photosynthetic parameters were measured under mild, moderate, and severe drought stress conditions. Volatile and nonvolatile isoprenoids, antioxidant enzymes, and phenylpropanoids were measured with the same time course, but in four different periods of the day. Drought severely inhibited photosynthesis, whereas it did not markedly affect the photochemical machinery. Isoprene emission and zeaxanthin concentration were higher in WS than in WW leaves, particularly at mild and moderate stresses, and during the hottest hours of the day. The activities of catalase and ascorbate peroxidase steeply declined during the day, while the activity of guaiacol peroxidase and the concentration of quercetin increased during the day, peaking in the hottest hours in both WW and WS plants. Our experiment reveals a sequence of antioxidants that were used daily by plants to orchestrate defense against oxidative stress induced by drought and associated high light and high temperature. Secondary metabolites seem valuable complements of antioxidant enzymes to counter oxidative stress during the hottest daily hours.

  5. A photoactive isoprenoid diphosphate analogue containing a stable phosphonate linkage: synthesis and biochemical studies with prenyltransferases

    Science.gov (United States)

    DeGraw, Amanda J.; Zhao, Zongbao; Strickland, Corey L.; Taban, A. Huma; Hsieh, John; Michael, Jefferies; Xie, Wenshuang; Shintani, David; McMahan, Colleen; Cornish, Katrina; Distefano, Mark D.

    2008-01-01

    A number of biochemical processes rely on isoprenoids, including the post-translational modification of signaling proteins and the biosynthesis of a wide array of compounds. Photoactivatable analogues have been developed to study isoprenoid utilizing enzymes such as the isoprenoid synthases and prenyltransferases. While these initial analogues proved to be excellent structural analogues with good cross linking capability, they lack the stability needed when the goals include isolation of cross-linked species, tryptic digestion, and subsequent peptide sequencing. Here, the synthesis of a benzophenone-based farnesyl diphosphate analogue containing a stable phosphonophosphate group is described. Inhibition kinetics, photolabeling experiments, as well as x-ray crystallographic analysis with a protein prenyltransferase are described, verifying this compound as a good isoprenoid mimetic. In addition, the utility of this new analogue was explored by using it to photoaffinity label crude protein extracts obtained from Hevea brasiliensis latex. Those experiments suggest that a small protein, Rubber Elongation Factor, interacts directly with farnesyl diphosphate during rubber biosynthesis. These results indicate that this benzophenone-based isoprenoid analogue will be useful for identifying enzymes that utilize farnesyl diphosphate as a substrate. PMID:17477573

  6. Block of the Mevalonate Pathway Triggers Oxidative and Inflammatory Molecular Mechanisms Modulated by Exogenous Isoprenoid Compounds

    Directory of Open Access Journals (Sweden)

    Paola Maura Tricarico

    2014-04-01

    Full Text Available Deregulation of the mevalonate pathway is known to be involved in a number of diseases that exhibit a systemic inflammatory phenotype and often neurological involvements, as seen in patients suffering from a rare disease called mevalonate kinase deficiency (MKD. One of the molecular mechanisms underlying this pathology could depend on the shortage of isoprenoid compounds and the subsequent mitochondrial damage, leading to oxidative stress and pro-inflammatory cytokines’ release. Moreover, it has been demonstrated that cellular death results from the balance between apoptosis and pyroptosis, both driven by mitochondrial damage and the molecular platform inflammasome. In order to rescue the deregulated pathway and decrease inflammatory markers, exogenous isoprenoid compounds were administered to a biochemical model of MKD obtained treating a murine monocytic cell line with a compound able to block the mevalonate pathway, plus an inflammatory stimulus. Our results show that isoprenoids acted in different ways, mainly increasing the expression of the evaluated markers [apoptosis, mitochondrial dysfunction, nucleotide-binding oligomerization-domain protein-like receptors 3 (NALP3, cytokines and nitric oxide (NO]. Our findings confirm the hypothesis that inflammation is triggered, at least partially, by the shortage of isoprenoids. Moreover, although further studies are necessary, the achieved results suggest a possible role for exogenous isoprenoids in the treatment of MKD.

  7. Block of the mevalonate pathway triggers oxidative and inflammatory molecular mechanisms modulated by exogenous isoprenoid compounds.

    Science.gov (United States)

    Tricarico, Paola Maura; Kleiner, Giulio; Valencic, Erica; Campisciano, Giuseppina; Girardelli, Martina; Crovella, Sergio; Knowles, Alessandra; Marcuzzi, Annalisa

    2014-04-22

    Deregulation of the mevalonate pathway is known to be involved in a number of diseases that exhibit a systemic inflammatory phenotype and often neurological involvements, as seen in patients suffering from a rare disease called mevalonate kinase deficiency (MKD). One of the molecular mechanisms underlying this pathology could depend on the shortage of isoprenoid compounds and the subsequent mitochondrial damage, leading to oxidative stress and pro-inflammatory cytokines' release. Moreover, it has been demonstrated that cellular death results from the balance between apoptosis and pyroptosis, both driven by mitochondrial damage and the molecular platform inflammasome. In order to rescue the deregulated pathway and decrease inflammatory markers, exogenous isoprenoid compounds were administered to a biochemical model of MKD obtained treating a murine monocytic cell line with a compound able to block the mevalonate pathway, plus an inflammatory stimulus. Our results show that isoprenoids acted in different ways, mainly increasing the expression of the evaluated markers [apoptosis, mitochondrial dysfunction, nucleotide-binding oligomerization-domain protein-like receptors 3 (NALP3), cytokines and nitric oxide (NO)]. Our findings confirm the hypothesis that inflammation is triggered, at least partially, by the shortage of isoprenoids. Moreover, although further studies are necessary, the achieved results suggest a possible role for exogenous isoprenoids in the treatment of MKD.

  8. Virtual volatility

    Science.gov (United States)

    Silva, A. Christian; Prange, Richard E.

    2007-03-01

    We introduce the concept of virtual volatility. This simple but new measure shows how to quantify the uncertainty in the forecast of the drift component of a random walk. The virtual volatility also is a useful tool in understanding the stochastic process for a given portfolio. In particular, and as an example, we were able to identify mean reversion effect in our portfolio. Finally, we briefly discuss the potential practical effect of the virtual volatility on an investor asset allocation strategy.

  9. Virtual volatility

    OpenAIRE

    A. Christian Silva; Prange, Richard E.

    2006-01-01

    We introduce the concept of virtual volatility. This simple but new measure shows how to quantify the uncertainty in the forecast of the drift component of a random walk. The virtual volatility also is a useful tool in understanding the stochastic process for a given portfolio. In particular, and as an example, we were able to identify mean reversion effect in our portfolio. Finally, we briefly discuss the potential practical effect of the virtual volatility on an investor asset allocation st...

  10. Plant volatiles.

    Science.gov (United States)

    Baldwin, Ian T

    2010-05-11

    Plant volatiles are the metabolites that plants release into the air. The quantities released are not trivial. Almost one-fifth of the atmospheric CO2 fixed by land plants is released back into the air each day as volatiles. Plants are champion synthetic chemists; they take advantage of their anabolic prowess to produce volatiles, which they use to protect themselves against biotic and abiotic stresses and to provide information - and potentially disinformation - to mutualists and competitors alike. As transferors of information, volatiles have provided plants with solutions to the challenges associated with being rooted in the ground and immobile.

  11. Microbial isoprenoid production: an example of green chemistry through metabolic engineering.

    Science.gov (United States)

    Maury, Jérôme; Asadollahi, Mohammad A; Møller, Kasper; Clark, Anthony; Nielsen, Jens

    2005-01-01

    Saving energy, cost efficiency, producing less waste, improving the biodegradability of products, potential for producing novel and complex molecules with improved properties, and reducing the dependency on fossil fuels as raw materials are the main advantages of using biotechnological processes to produce chemicals. Such processes are often referred to as green chemistry or white biotechnology. Metabolic engineering, which permits the rational design of cell factories using directed genetic modifications, is an indispensable strategy for expanding green chemistry. In this chapter, the benefits of using metabolic engineering approaches for the development of green chemistry are illustrated by the recent advances in microbial production of isoprenoids, a diverse and important group of natural compounds with numerous existing and potential commercial applications. Accumulated knowledge on the metabolic pathways leading to the synthesis of the principal precursors of isoprenoids is reviewed, and recent investigations into isoprenoid production using engineered cell factories are described.

  12. Remodeling the isoprenoid pathway in tobacco by expressing the cytoplasmic mevalonate pathway in chloroplasts.

    Science.gov (United States)

    Kumar, Shashi; Hahn, Frederick M; Baidoo, Edward; Kahlon, Talwinder S; Wood, Delilah F; McMahan, Colleen M; Cornish, Katrina; Keasling, Jay D; Daniell, Henry; Whalen, Maureen C

    2012-01-01

    Metabolic engineering to enhance production of isoprenoid metabolites for industrial and medical purposes is an important goal. The substrate for isoprenoid synthesis in plants is produced by the mevalonate pathway (MEV) in the cytosol and by the 2-C-methyl-d-erythritol 4-phosphate (MEP) pathway in plastids. A multi-gene approach was employed to insert the entire cytosolic MEV pathway into the tobacco chloroplast genome. Molecular analysis confirmed the site-specific insertion of seven transgenes and homoplasmy. Functionality was demonstrated by unimpeded growth on fosmidomycin, which specifically inhibits the MEP pathway. Transplastomic plants containing the MEV pathway genes accumulated higher levels of mevalonate, carotenoids, squalene, sterols, and triacyglycerols than control plants. This is the first time an entire eukaryotic pathway with six enzymes has been transplastomically expressed in plants. Thus, we have developed an important tool to redirect metabolic fluxes in the isoprenoid biosynthesis pathway and a viable multigene strategy for engineering metabolism in plants.

  13. Volatiles in protoplanetary disks

    CERN Document Server

    Pontoppidan, Klaus M; Bergin, Edwin A; Brittain, Sean; Marty, Bernard; Mousis, Olvier; Oberg, Karin L

    2014-01-01

    Volatiles are compounds with low sublimation temperatures, and they make up most of the condensible mass in typical planet-forming environments. They consist of relatively small, often hydrogenated, molecules based on the abundant elements carbon, nitrogen and oxygen. Volatiles are central to the process of planet formation, forming the backbone of a rich chemistry that sets the initial conditions for the formation of planetary atmospheres, and act as a solid mass reservoir catalyzing the formation of planets and planetesimals. This growth has been driven by rapid advances in observations and models of protoplanetary disks, and by a deepening understanding of the cosmochemistry of the solar system. Indeed, it is only in the past few years that representative samples of molecules have been discovered in great abundance throughout protoplanetary disks - enough to begin building a complete budget for the most abundant elements after hydrogen and helium. The spatial distributions of key volatiles are being mapped...

  14. Unstable volatility

    DEFF Research Database (Denmark)

    Casas, Isabel; Gijbels, Irène

    2012-01-01

    The objective of this paper is to introduce the break-preserving local linear (BPLL) estimator for the estimation of unstable volatility functions for independent and asymptotically independent processes. Breaks in the structure of the conditional mean and/or the volatility functions are common i...

  15. Unstable volatility

    DEFF Research Database (Denmark)

    Casas, Isabel; Gijbels, Irène

    2012-01-01

    The objective of this paper is to introduce the break-preserving local linear (BPLL) estimator for the estimation of unstable volatility functions for independent and asymptotically independent processes. Breaks in the structure of the conditional mean and/or the volatility functions are common i...

  16. The non-mevalonate isoprenoid biosynthesis of plants as a test system for drugs against malaria and pathogenic bacteria.

    Science.gov (United States)

    Zeidler, J; Schwender, J; Mueller, C; Lichtenthaler, H K

    2000-12-01

    Two plant test systems are presented in the search for new inhibitors of the non-mevalonate isoprenoid pathway. A derivative of clomazone appears to be an inhibitor of the deoxyxylulose 5-phosphate/methylerythritol 4-phosphate (DOXP/MEP) pathway of isoprenoid formation.

  17. Oxygen isotopes and volatile contents of the Gorgona komatiites, Colombia: A confirmation of the deep mantle origin of H2O

    Science.gov (United States)

    Gurenko, Andrey A.; Kamenetsky, Vadim S.; Kerr, Andrew C.

    2016-11-01

    We report O isotopes in olivine grains (Fo89-93) and volatile contents (CO2, H2O, F, S, Cl) in olivine-hosted melt inclusions from one Gorgona picrite and five komatiites with the aim of constraining the origin of H2O in these magmas. These samples have previously been analysed for major and trace elements and volatile concentrations (H2O, S, Cl) and B isotopes in melt inclusions. A distinctive feature of the included melts is relatively high contents of volatile components and boron, which show positive anomalies in, otherwise depleted, primitive mantle normalised trace and rare earth element patterns and range in δ11 B from -11.5 to 15.6‰. In this study, the olivines were systematically analysed for O isotopes (1) in the centre of grains, (2) near the grain boundaries and, (3) as close as possible to the studied melt inclusions. The majority of olivines (∼66%) are "mantle"-like, 4.8 ‰ ≤δ18 O ≤ 5.5 ‰, with a subordinate but still significant number (∼33%) above, and only 2 grains below, this range. There is no systematic difference between the central and marginal parts of the grains. Higher than "mantle" δ18OOl values are ascribed to low-T (<300 °C) serpentinisation along inner fractures and grain boundaries of olivine phenocrysts. The measured concentrations of volatile components in the melt inclusions corrected for the effects of post-entrapment crystallisation and H2O-CO2 exsolution in inclusion shrinkage bubbles are: 286-1748 μg/g CO2, 0.2-0.86 wt.% H2O, 48-82 μg/g F, 398-699 μg/g S and 132-198 μg/g Cl. They correspond to a pressure of 86 ± 44MPa or ∼2.5-km crustal depth of olivine crystallisation. The correlations of S and, to a lesser extent, of H2O, with highly incompatible lithophile elements and the correlation of F with Cl, but no relationships of H2O with Cl, rule out shallow depth magma degassing and/or crustal contamination. Our new δ18 O olivine and volatile component data combined with the existing, highly variable δ11 B

  18. Plant-specific volatile organic compound emission rates from young and mature leaves of Mediterranean vegetation

    Science.gov (United States)

    Bracho-Nunez, Araceli; Welter, Saskia; Staudt, Michael; Kesselmeier, Jürgen

    2011-08-01

    The seasonality of vegetation, i.e., developmental stages and phenological processes, affects the emission of volatile organic compounds (VOCs). Despite the potential significance, the contributions of seasonality to VOC emission quality and quantity are not well understood and are therefore often ignored in emission simulations. We investigated the VOC emission patterns of young and mature leaves of several Mediterranean plant species in relation to their physiological and developmental changes during the growing period and estimated Es. Foliar emissions of isoprenoids and oxygenated VOCs like methanol and acetone were measured online by means of a proton transfer reaction mass spectrometer (PTR-MS) and offline with gas chromatography coupled with a mass spectrometer and flame ionization detector. The results suggest that VOC emission is a developmentally regulated process and that quantitative and qualitative variability is plant species specific. Leaf ontogeny clearly influenced both the VOC Es and the relative importance of different VOCs. Methanol was the major compound contributing to the sum of target VOC emissions in young leaves (11.8 ± 10.4 μg g-1 h-1), while its contribution was minor in mature leaves (4.1 ± 4.1 μg g-1 h-1). Several plant species showed a decrease or complete subsidence of monoterpene, sesquiterpene, and acetone emissions upon maturity, perhaps indicating a potential response to the higher defense demands of young emerging leaves.

  19. Chapter 3: Omics Advances of Biosynthetic Pathways of Isoprenoid Production in Microalgae

    Energy Technology Data Exchange (ETDEWEB)

    Paniagua-Michel, J.; Subramanian, Venkataramanan

    2017-01-01

    In this chapter, the current status of microalgal isoprenoids and the role of omics technologies, or otherwise specified, in bioproducts optimization and applications are reviewed. Emphasis is focused in the metabolic pathways of microalgae involved in the production of commercially important products, namely, hydrocarbons and biofuels, nutraceuticals, and pharmaceuticals.

  20. Restricted utility of aryl isoprenoids as indicators of photic zone anoxia

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Koopmans, M.P.; Schouten, S.; Kohnen, M.E.L.

    1996-01-01

    In a North Sea oil, the carotenoid derivatives -carotene, -isorenieratane, and isorenieratane were identified, together with a series of aryl isoprenoids with a 2,3,6-trimethyl substitution pattern for the aromatic ring. The 13C values of -carotene and -isorenieratane are similar, whereas isoreniera

  1. Squalenes, phytanes and other isoprenoids as major neutral lipids of methanogenic and thermoacidophilic archaebacteria

    Energy Technology Data Exchange (ETDEWEB)

    Tornabene, T.G. (Colorado State Univ., Fort Collins); Langworthy, T.A.; Holzer, G.; Oro, J.

    1979-01-01

    The neutral lipids of nine species of methanogenic bacteria including five methanobacilli, two methanococci, a methanospirillum, one methanosarcina as well as two thermoacidophilic bacteria, Thermoplasma and Sulfolobus, were analyzed. The major components were C/sub 30/, C/sub 25/ and/or C/sub 20/ acyclic isoprenoid hydrocarbons with a continuous range of hydroisoprenoid homologues. The range of acyclic isoprenoids detected were from C/sub 14/ to C/sub 30/. Apart from Methanosarcina barkeri, squalene and/or hydrosqualene derivatives were the predominant components in all species studied. The components of Methanosarcina barkeri were a family of C/sub 25/ homologues. The distribution of the neutral lipid components and their specific variations in relative intensities emphasized the differences between the test organisms while the generic nature of the isoprenoid hydrocarbons demonstrated similarities between the diverse bacteria. The neutral lipid compositions from these bacteria, many of which exist in environmental conditions like those described for the various evolutionary stages of the archean ecology, resemble the isoprenoid distribution isolated from ancient sediments and petroleum. Therefore, these findings may have major implications to biological and biogeochemical evolution.

  2. Perspectives and limits of engineering the isoprenoid metabolism in heterologous hosts

    NARCIS (Netherlands)

    Muntendam, Remco; Melillo, Elena; Ryden, Annamargareta; Kayser, Oliver

    2009-01-01

    Terpenoids belong to the largest class of natural compounds and are produced in all living organisms. The isoprenoid skeleton is based on assembling of C5 building blocks, but the biosynthesis of a great variety of terpenoids ranging from monoterpenoids to polyterpenoids is not fully understood toda

  3. Chasing volatility

    DEFF Research Database (Denmark)

    Caporin, Massimiliano; Rossi, Eduardo; Santucci de Magistris, Paolo

    The realized volatility of financial returns is characterized by persistence and occurrence of unpreditable large increments. To capture those features, we introduce the Multiplicative Error Model with jumps (MEM-J). When a jump component is included in the multiplicative specification, the condi...... models, the introduction of the jump component provides a sensible improvement in the fit, as well as for in-sample and out-of-sample volatility tail forecasts....

  4. Volatility Risk

    OpenAIRE

    Zhiguang Wang

    2009-01-01

    Classical capital asset pricing theory tells us that riskaverse investors would require higher returns to compensate for higher risk on an investment. One type of risk is price (return) risk, which reflects uncertainty in the price level and is measured by the volatility (standard deviation) of asset returns. Volatility itself is also known to be random and hence is perceived as another type of risk. Investors can bear price risk in exchange for a higher return. But are investors willing to p...

  5. Seasonal cycles of biogenic volatile organic compound fluxes and concentrations in a California citrus orchard

    Science.gov (United States)

    Fares, S.; Park, J.-H.; Gentner, D. R.; Weber, R.; Ormeño, E.; Karlik, J.; Goldstein, A. H.

    2012-10-01

    Orange trees are widely cultivated in Mediterranean climatic regions where they are an important agricultural crop. Citrus have been characterized as emitters of volatile organic compounds (VOC) in chamber studies under controlled environmental conditions, but an extensive characterization at field scale has never been performed using modern measurement methods, and is particularly needed considering the complex interactions between the orchards and the polluted atmosphere in which Citrus is often cultivated. For one year, in a Valencia orange orchard in Exeter, California, we measured fluxes using PTRMS (Proton Transfer Reaction Mass Spectrometer) and eddy covariance for the most abundant VOC typically emitted from citrus vegetation: methanol, acetone, and isoprenoids. Concentration gradients of additional oxygenated and aromatic compounds from the ground level to above the canopy were also measured. In order to characterize concentrations of speciated biogenic VOC (BVOC) in leaves, we analyzed leaf content by GC-MS (Gas Chromatography - Mass Spectrometery) regularly throughout the year. We also characterized in more detail concentrations of speciated BVOC in the air above the orchard by in-situ GC-MS during a few weeks in spring flowering and summer periods. Here we report concentrations and fluxes of the main VOC species emitted by the orchard, discuss how fluxes measured in the field relate to previous studies made with plant enclosures, and describe how VOC content in leaves and emissions change during the year in response to phenological and environmental parameters. The orchard was a source of monoterpenes and oxygenated VOC. The highest emissions were observed during the springtime flowering period, with mid-day fluxes above 2 nmol m-2 s-1 for methanol and up to 1 nmol m-2 s-1 for acetone and monoterpenes. During hot summer days emissions were not as high as we expected considering the known dependence of biogenic emissions on temperature. We provide

  6. A new C9 nor-isoprenoid glucoside from Rantherium suaveolens.

    Science.gov (United States)

    Oueslati, M Habib; Ben Jannet, H; Mighri, Zine; Matthew, Susan; Abreu, Pedro M

    2007-08-01

    The new C(9) nor-isoprenoid 3-methyl-octa-1,5-diene-7-one-3-O-beta-D-glucopyranoside, named as ranthenone glucoside (1), together with the previously known 9-hydoxylinaloyl glucoside (2), sitosterol-3beta-O-[6'-palmitoyl-beta-D-glucopyranoside] (3), scopoletin (4), fraxetin (5), and scopolin (6), were isolated from the aerial parts of Rantherium suaveolens. The structures of these compounds were elucidated by extensive spectroscopic analysis.

  7. Simvastatin inhibits Staphylococcus aureus host cell invasion through modulation of isoprenoid intermediates

    OpenAIRE

    Horn, Mary P.; Knecht, Sharmon M.; Rushing, Frances L.; Birdsong, Julie; Siddall, C. Parker; Johnson, Charron M.; Abraham, Terri N.; Brown, Amy; Volk, Catherine B.; Gammon, Kelly; Bishop, Derron L.; McKillip, John L.; McDowell, Susan A.

    2008-01-01

    Patients on a statin regimen are at a decreased risk of death due to bacterial sepsis. We have found that protection by simvastatin includes the inhibition of host cell invasion by Staphylococcus aureus, the most common etiologic agent of sepsis. Inhibition was due in part to depletion of isoprenoid intermediates within the cholesterol biosynthesis pathway and led to the cytosolic accumulation of the small-guanosine triphosphatases (GTPases) CDC42, Rac, and RhoB. Actin stress fiber disassembl...

  8. Closed pyrolyses of the isoprenoid algaenan of Botryococcus braunii, L race: geochemical implications for derived kerogens

    Science.gov (United States)

    Behar, F.; Derenne, S.; Largeau, C.

    1995-07-01

    Algaenans, i.e., highly aliphatic, nonhydrolysable, insoluble macromolecular constituents, have been identified in a number of microalga cell walls and their selective preservation shown to play a major role in the formation of numerous kerogens. All the algaenans so far examined comprise a network of long polymethylenic chains, except for the L race of Botryococcus braunii. The resistant macromolecular material isolated from the latter, termed PRB L, is based on C 40 isoprenoid chains with a lycopane-type skeleton. Recent comparative studies of PRB L and of Botryococcus-derived sediments provided the first example of kerogen formation via the selective preservation of an "isoprenoid" algaenan. The present study is concerned with PRB L pyrolyses in sealed gold tubes under various temperature/time conditions (260-350°C, 0.5-69 h). For the conversion rates thus obtained, ranging from 30 to 100%, a complete mass balance of the different families of pyrolysis products was established; most of the C 1 to C 40 pyrolysate constituents were identified and the abundances of the above compounds and their variations with conversion progress were determined. This study thus allowed us (1) to derive further information about PRB L chemical structure (location of the ether bridges, contribution of linear chains and their relationships with the C 40 isoprenoid ones), (2) to determine the behaviour of this isoprenoid algaenan to thermal stress (timing of the formation of the different groups of products then released, nature of the primary cleavages, origin and mode of formation of the secondary products, and further degradations), and (3) to show, in connection with previous studies, that PRB L-derived kerogens should exhibit pronounced differences relative to standard type I kerogens, the latter being based on polymethylenic chains, regarding not only the structure of the generated products but also the timing of oil generation (upward shift of the catagenesis zone).

  9. Restricted utility of aryl isoprenoids as indicators of photic zone anoxia

    OpenAIRE

    Sinninghe Damsté, J.S.; Koopmans, M. P.; S. Schouten; Kohnen, M.E.L.

    1996-01-01

    In a North Sea oil, the carotenoid derivatives -carotene, -isorenieratane, and isorenieratane were identified, together with a series of aryl isoprenoids with a 2,3,6-trimethyl substitution pattern for the aromatic ring. The 13C values of -carotene and -isorenieratane are similar, whereas isorenieratane is ca. 15% heavier. This suggests that -isorenieratane is not derived from -isorenieratane biosynthesised by Chlorobiaceae, but from aromatisation of -carotene. This was confirmed by laborator...

  10. Structure elucidation and phytotoxicity of C13 nor-isoprenoids from Cestrum parqui.

    Science.gov (United States)

    D'Abrosca, Brigida; DellaGreca, Marina; Fiorentino, Antonio; Monaco, Pietro; Oriano, Palma; Temussi, Fabio

    2004-02-01

    Twelve C(13) nor-isoprenoids have been isolated from the leaves of Cestrum parqui (Solanaceae). The structure (2R,6R,9R)-2,9-dihydroxy-4-megastigmen-3-one has been assigned to the new compound. All the structures have been determined by spectroscopic means and chemical correlations. The compounds showed phytotoxic effect on the germination and growth of Lactuca sativa L.

  11. Inactivation of sll1556 in Synechocystis strain PCC 6803 impairs isoprenoid biosynthesis from pentose phosphate cycle substrates in vitro.

    Science.gov (United States)

    Poliquin, Kelly; Ershov, Yuri V; Cunningham, Francis X; Woreta, Tinsay T; Gantt, R Raymond; Gantt, Elisabeth

    2004-07-01

    In cyanobacteria many compounds, including chlorophylls, carotenoids, and hopanoids, are synthesized from the isoprenoid precursors isopentenyl diphosphate (IPP) and dimethylallyl diphosphate. Isoprenoid biosynthesis in extracts of the cyanobacterium Synechocystis strain PCC 6803 grown under photosynthetic conditions, stimulated by pentose phosphate cycle substrates, does not appear to require methylerythritol phosphate pathway intermediates. The sll1556 gene, distantly related to type 2 IPP isomerase genes, was disrupted by insertion of a Kanr cassette. The mutant was fully viable under photosynthetic conditions although impaired in the utilization of pentose phosphate cycle substrates. Compared to the parental strain the Deltasll1556 mutant (i) is deficient in isoprenoid biosynthesis in vitro with substrates including glyceraldehyde-3-phosphate, fructose-6-phosphate, and glucose-6-phosphate; (ii) has smaller cells (diameter ca. 13% less); (iii) has fewer thylakoids (ca. 30% less); and (iv) has a more extensive fibrous outer wall layer. Isoprenoid biosynthesis is restored with pentose phosphate cycle substrates plus the recombinant Sll1556 protein in the Deltasll1556 supernatant fraction. IPP isomerase activity could not be demonstrated for the purified Sll1556 protein under our in vitro conditions. The reduction of thylakoid area and the effect on outer wall layer components are consistent with an impairment of isoprenoid biosynthesis in the mutant, possibly via hopanoid biosynthesis. Our findings are consistent with an alternate metabolic shunt for biosynthesis of isoprenoids. Copyright 2004 American Society for Microbiology

  12. Restricted utility of aryl isoprenoids as indicators for photic zone anoxia

    Science.gov (United States)

    Koopmans, Martin P.; Schouten, Stefan; Kohnen, Math E. L.; Sinninghe Damsté, Jaap S.

    1996-12-01

    In a North Sea oil, the carotenoid derivatives β-carotene, β-isorenieratane, and isorenieratane were identified, together with a series of aryl isoprenoids with a 2,3,6-trimethyl substitution pattern for the aromatic ring. The δ13C values of β-carotene and β-isorenieratane are similar, whereas isorenieratane is ca. 15% heavier. This suggests that β-isorenieratane is not derived from β-isorenieratane biosynthesised by Chlorobiaceae, but from aromatisation of β-carotene. This was confirmed by laboratory aromatisation of partially hydrogenated β-carotene, which yielded β-isorenieratane as the main product. The aryl isoprenoids, which can be formed by Csbnd C bond cleavage of both isorenieratane and β-isorenieratane, have a mixed isotopic signature in the oil. These results indicate that mere identification of aryl isoprenoids, without determination of their δ13C values, cannot be used to assess the presence of Chlorobiaceae, and, thus, photic zone anoxia in the depositional environment.

  13. Metabolite profiling identified methylerythritol cyclodiphosphate efflux as a limiting step in microbial isoprenoid production.

    Science.gov (United States)

    Zhou, Kang; Zou, Ruiyang; Stephanopoulos, Gregory; Too, Heng-Phon

    2012-01-01

    Isoprenoids are natural products that are all derived from isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). These precursors are synthesized either by the mevalonate (MVA) pathway or the 1-Deoxy-D-Xylulose 5-Phosphate (DXP) pathway. Metabolic engineering of microbes has enabled overproduction of various isoprenoid products from the DXP pathway including lycopene, artemisinic acid, taxadiene and levopimaradiene. To date, there is no method to accurately measure all the DXP metabolic intermediates simultaneously so as to enable the identification of potential flux limiting steps. In this study, a solid phase extraction coupled with ultra performance liquid chromatography mass spectrometry (SPE UPLC-MS) method was developed. This method was used to measure the DXP intermediates in genetically engineered E. coli. Unexpectedly, methylerythritol cyclodiphosphate (MEC) was found to efflux when certain enzymes of the pathway were over-expressed, demonstrating the existence of a novel competing pathway branch in the DXP metabolism. Guided by these findings, ispG was overexpressed and was found to effectively reduce the efflux of MEC inside the cells, resulting in a significant increase in downstream isoprenoid production. This study demonstrated the necessity to quantify metabolites enabling the identification of a hitherto unrecognized pathway and provided useful insights into rational design in metabolic engineering.

  14. Metabolite profiling identified methylerythritol cyclodiphosphate efflux as a limiting step in microbial isoprenoid production.

    Directory of Open Access Journals (Sweden)

    Kang Zhou

    Full Text Available Isoprenoids are natural products that are all derived from isopentenyl diphosphate (IPP and dimethylallyl diphosphate (DMAPP. These precursors are synthesized either by the mevalonate (MVA pathway or the 1-Deoxy-D-Xylulose 5-Phosphate (DXP pathway. Metabolic engineering of microbes has enabled overproduction of various isoprenoid products from the DXP pathway including lycopene, artemisinic acid, taxadiene and levopimaradiene. To date, there is no method to accurately measure all the DXP metabolic intermediates simultaneously so as to enable the identification of potential flux limiting steps. In this study, a solid phase extraction coupled with ultra performance liquid chromatography mass spectrometry (SPE UPLC-MS method was developed. This method was used to measure the DXP intermediates in genetically engineered E. coli. Unexpectedly, methylerythritol cyclodiphosphate (MEC was found to efflux when certain enzymes of the pathway were over-expressed, demonstrating the existence of a novel competing pathway branch in the DXP metabolism. Guided by these findings, ispG was overexpressed and was found to effectively reduce the efflux of MEC inside the cells, resulting in a significant increase in downstream isoprenoid production. This study demonstrated the necessity to quantify metabolites enabling the identification of a hitherto unrecognized pathway and provided useful insights into rational design in metabolic engineering.

  15. Plant volatiles in extreme terrestrial and marine environments.

    Science.gov (United States)

    Rinnan, Riikka; Steinke, Michael; McGenity, Terry; Loreto, Francesco

    2014-08-01

    This review summarizes the current understanding on plant and algal volatile organic compound (VOC) production and emission in extreme environments, where temperature, water availability, salinity or other environmental factors pose stress on vegetation. Here, the extreme environments include terrestrial systems, such as arctic tundra, deserts, CO₂ springs and wetlands, and marine systems such as sea ice, tidal rock pools and hypersaline environments, with mangroves and salt marshes at the land-sea interface. The emission potentials at fixed temperature and light level or actual emission rates for phototrophs in extreme environments are frequently higher than for organisms from less stressful environments. For example, plants from the arctic tundra appear to have higher emission potentials for isoprenoids than temperate species, and hypersaline marine habitats contribute to global dimethyl sulphide (DMS) emissions in significant amounts. DMS emissions are more widespread than previously considered, for example, in salt marshes and some desert plants. The reason for widespread VOC, especially isoprenoid, emissions from different extreme environments deserves further attention, as these compounds may have important roles in stress resistance and adaptation to extremes. Climate warming is likely to significantly increase VOC emissions from extreme environments both by direct effects on VOC production and volatility, and indirectly by altering the composition of the vegetation.

  16. Study of 'Redhaven' peach and its white-fleshed mutant suggests a key role of CCD4 carotenoid dioxygenase in carotenoid and norisoprenoid volatile metabolism

    Directory of Open Access Journals (Sweden)

    Tartarini Stefano

    2011-01-01

    Full Text Available Abstract Background Carotenoids are plant metabolites which are not only essential in photosynthesis but also important quality factors in determining the pigmentation and aroma of flowers and fruits. To investigate the regulation of carotenoid metabolism, as related to norisoprenoids and other volatile compounds in peach (Prunus persica L. Batsch., and the role of carotenoid dioxygenases in determining differences in flesh color phenotype and volatile composition, the expression patterns of relevant carotenoid genes and metabolites were studied during fruit development along with volatile compound content. Two contrasted cultivars, the yellow-fleshed 'Redhaven' (RH and its white-fleshed mutant 'Redhaven Bianca' (RHB were examined. Results The two genotypes displayed marked differences in the accumulation of carotenoid pigments in mesocarp tissues. Lower carotenoid levels and higher levels of norisoprenoid volatiles were observed in RHB, which might be explained by differential activity of carotenoid cleavage dioxygenase (CCD enzymes. In fact, the ccd4 transcript levels were dramatically higher at late ripening stages in RHB with respect to RH. The two genotypes also showed differences in the expression patterns of several carotenoid and isoprenoid transcripts, compatible with a feed-back regulation of these transcripts. Abamine SG - an inhibitor of CCD enzymes - decreased the levels of both isoprenoid and non-isoprenoid volatiles in RHB fruits, indicating a complex regulation of volatile production. Conclusions Differential expression of ccd4 is likely to be the major determinant in the accumulation of carotenoids and carotenoid-derived volatiles in peach fruit flesh. More in general, dioxygenases appear to be key factors controlling volatile composition in peach fruit, since abamine SG-treated 'Redhaven Bianca' fruits had strongly reduced levels of norisoprenoids and other volatile classes. Comparative functional studies of peach carotenoid

  17. Dynamic Solution Injection: a new method for preparing pptv–ppbv standard atmospheres of volatile organic compounds

    Directory of Open Access Journals (Sweden)

    L. Abrell

    2010-11-01

    Full Text Available Proton Transfer Reaction-Mass Spectrometry (PTR-MS and thermal desorption Gas Chromatography-Mass Spectrometry (GC-MS allow for absolute quantification of a wide range of atmospheric volatile organic compounds (VOCs with concentrations in the ppbv to pptv range. Although often neglected, routine calibration is necessary for accurate quantification of VOCs by PTR-MS and GC-MS. Several gas calibration methods currently exist, including compressed gas cylinders, permeation tubes, diffusion tubes, and liquid injection. While each method has its advantages and limitations, no single technique has emerged that is capable of dynamically generating known concentrations of complex mixtures of VOCs over a large concentration range (ppbv to pptv and is technically simple, field portable, and affordable. We present the development of a new VOC calibration technique based on liquid injection with these features termed Dynamic Solution Injection (DSI. This method consists of injecting VOCs (0.1–0.5 mM dissolved in cyclohexane (PTR-MS or methanol (GC-MS into a 1.0 slpm flow of purified dilution gas in an unheated 25 ml glass vial. Upon changes in the injection flow rate (0.5–4.0 μl min−1, new VOC concentrations are reached within seconds to minutes, depending on the compound, with a liquid injection flow rate accuracy and precision of better than 7% and 4% respectively. We demonstrate the utility of the DSI technique by calibrating a PTR-MS to seven different cyclohexane solutions containing a total of 34 different biogenic compounds including volatile isoprenoids, oxygenated VOCs, fatty acid oxidation products, aromatics, and dimethyl sulfide. We conclude that because of its small size, low cost, and simplicity, the Dynamic Solution Injection method will be of great use to both laboratory and field VOC studies.

  18. Pricing Volatility Referenced Assets

    Directory of Open Access Journals (Sweden)

    Alan De Genaro Dario

    2006-12-01

    Full Text Available Volatility swaps are contingent claims on future realized volatility. Variance swaps are similar instruments on future realized variance, the square of future realized volatility. Unlike a plain vanilla option, whose volatility exposure is contaminated by its asset price dependence, volatility and variance swaps provide a pure exposure to volatility alone. This article discusses the risk-neutral valuation of volatility and variance swaps based on the framework outlined in the Heston (1993 stochastic volatility model. Additionally, the Heston (1993 model is calibrated for foreign currency options traded at BMF and its parameters are used to price swaps on volatility and variance of the BRL / USD exchange rate.

  19. Volatile and non-volatile/semi-volatile compounds and in vitro bioactive properties of Chilean Ulmo (Eucryphia cordifolia Cav.) honey.

    Science.gov (United States)

    Acevedo, Francisca; Torres, Paulina; Oomah, B Dave; de Alencar, Severino Matias; Massarioli, Adna Prado; Martín-Venegas, Raquel; Albarral-Ávila, Vicenta; Burgos-Díaz, César; Ferrer, Ruth; Rubilar, Mónica

    2017-04-01

    Ulmo honey originating from Eucryphia cordifolia tree, known locally in the Araucania region as the Ulmo tree is a natural product with valuable nutritional and medicinal qualities. It has been used in the Mapuche culture to treat infections. This study aimed to identify the volatile and non-volatile/semi-volatile compounds of Ulmo honey and elucidate its in vitro biological properties by evaluating its antioxidant, antibacterial, antiproliferative and hemolytic properties and cytotoxicity in Caco-2 cells. Headspace volatiles of Ulmo honey were isolated by solid-phase microextraction (SPME); non-volatiles/semi-volatiles were obtained by removing all saccharides with acidified water and the compounds were identified by GC/MS analysis. Ulmo honey volatiles consisted of 50 compounds predominated by 20 flavor components. Two of the volatile compounds, lyrame and anethol have never been reported before as honey compounds. The non-volatile/semi-volatile components of Ulmo honey comprised 27 compounds including 13 benzene derivatives accounting 75% of the total peak area. Ulmo honey exhibited weak antioxidant activity but strong antibacterial activity particularly against gram-negative bacteria and methicillin-resistant Staphylococcus aureus (MRSA), the main strain involved in wounds and skin infections. At concentrations >0.5%, Ulmo honey reduced Caco-2 cell viability, released lactate dehydrogenase (LDH) and increased reactive oxygen species (ROS) production in a dose dependent manner in the presence of foetal bovine serum (FBS). The wide array of volatile and non-volatile/semi-volatile constituents of Ulmo honey rich in benzene derivatives may partly account for its strong antibacterial and antiproliferative properties important for its therapeutic use. Our results indicate that Ulmo honey can potentially inhibit cancer growth at least partly by modulating oxidative stress. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Distribution of the 3-hydroxyl-3-methylglutaryl coenzyme A reductase gene and isoprenoid production in marine-derived Actinobacteria.

    Science.gov (United States)

    Khan, Shams Tabrez; Izumikawa, Miho; Motohashi, Keiichiro; Mukai, Akira; Takagi, Motoki; Shin-Ya, Kazuo

    2010-03-01

    During the course of our screening program to isolate isoprenoids from marine Actinobacteria, 523 actinobacterial strains were isolated from 18 marine sponges, a tunicate, and two marine sediments. These strains belonged to 21 different genera, but most were members of Streptomyces, Nocardia, Rhodococcus, and Micromonospora. Some Actinobacteria have been reported to use the mevalonate pathway for the production of isoprenoids as secondary metabolites. Therefore, we investigated whether these strains possessed the 3-hydroxyl-3-methylglutaryl coenzyme A reductase (hmgr) gene, which indicates the presence of the mevalonate pathway. As a result, six strains belonging to the genera Streptomyces (SpC080624SC-11, SpA080624GE-02, and Sp080513GE-23), Nocardia (Sp080513SC-18), and Micromonospora (Se080624GE-07 and SpC080624GE-05) were found to possess the hmgr gene, and these genes were highly similar to hmgr genes in isoprenoid biosynthetic gene clusters. Among the six strains, the two strains SpC080624SC-11 and SpA080624GE-02 produced the novel isoprenoids, JBIR-46, -47, and -48, which consisted of phenazine chromophores, and Sp080513GE-23 produced a known isoprenoid, fumaquinone. Furthermore, these compounds showed cytotoxic activity against human acute myelogenous leukemia HL-60 cells.

  1. Isoprenoid hydrocarbons produced by thermal alteration of Nostoc muscorum and Rhodopseudomonas spheroides

    Science.gov (United States)

    Philp, R. P.; Brown, S.; Calvin, M.

    1978-01-01

    The potential of algae and photosynthetic bacteria to serve as precursors of kerogen was studied to determine what factors affect the relative rates of formation of precursor hydrocarbons. Cells of Nostoc muscorum and Rhodopseudomonas spheroides were subjected to thermal alteration (by heating samples in glass tubes sealed under nitrogen) for two, four, and twelve weeks. Both unextracted and extracted cells in the absence and presence of montmorillonite were investigated, and the isoprenoid hydrocarbons produced in these experiments were determined. Phytane and five isomeric phytenes were the main hydrocarbons observed; their relative rates of formation in the different experimental conditions are described. No phytadienes, pristane, or pristenes were detected.

  2. Spiral mining for lunar volatiles

    Science.gov (United States)

    Schmitt, H. H.; Kulcinski, G. L.; Sviatoslavsky, I. N.; Carrier, W. D., III

    Lunar spiral mining, extending outward from a periodically mobile central power and processing station represents an alternative for comparison with more traditional mining schemes. In this concept, a mining machine would separate regolith fines and extract the contained volatiles. Volatiles then would be pumped along the miner's support arm to the central station for refining and for export or storage. The basic architecture of the central processing station would be cylindrical. A central core area could house the power subsystem of hydrogen-oxygen engines or fuel cells. Habitat sections and other crew occupied areas could be arranged around the power generation core. The outer cylinder could include all volatile refining subsystems. Solar thermal power collectors and reflectors would be positioned on top of the central station. Long term exploitation of a volatile resource region would begin with establishment of a support base at the center of a long boundary of the region. The mining tract for each spiral mining system would extend orthogonal to this boundary. New spiral mining systems would be activated along parallel tracts as demand for lunar He-3 and other solar wind volatiles increased.

  3. Change of isoprenoids, steranes and terpanes during ex situ bioremediation of mazut on industrial level

    Directory of Open Access Journals (Sweden)

    Beškoski Vladimir P.

    2010-01-01

    Full Text Available The paper presents results of the ex situ bioremediation of soil contaminated by mazut (heavy residual fuel oil in the field scale (600 m3. A treatment-bed (thickness 0.4 m consisted of mechanically mixed mazut-contaminated soil, softwood sawdust as the additional carbon source and crude river sand, as bulking and porosity increasing material. The inoculation/reinoculation was conducted periodically using a biomass of a consortium of zymogenous microorganisms isolated from the bioremediation substrate. The biostimulation was performed through addition of nutritious substances (N, P and K. The aeration was improved by systematic mixing of the bioremediation system. After 50 days, the number of hydrocarbon degraders increased 100 times. Based on the changes in the group composition, the average biodegradation rate during bioremediation was 24 mg/kg/day for the aliphatic fraction, 6 mg/kg/day for the aromatic fraction, and 3 mg/kg/day for the nitrogen-sulphuroxygen compounds (NSO-asphaltene fraction. In the saturated hydrocarbon fraction, gas chromatography-mass spectrometry (GC-MS in the single ion-monitoring mode (SIM was applied to analyse isoprenoids pristane and phytane and polycyclic molecules of sterane and triterpane type. Biodegradation occurred during the bioremediation process, as well as reduction of relative quantities of isoprenoids, steranes, tri- and tetracyclic terpanes and pentacyclic terpanes of hopane type.

  4. Aerobic conditions increase isoprenoid biosynthesis pathway gene expression levels for carotenoid production in Enterococcus gilvus.

    Science.gov (United States)

    Hagi, Tatsuro; Kobayashi, Miho; Nomura, Masaru

    2015-06-01

    Some lactic acid bacteria that harbour carotenoid biosynthesis genes (crtNM) can produce carotenoids. Although aerobic conditions can increase carotenoid production and crtNM expression levels, their effects on the pathways that synthesize carotenoid precursors such as mevalonate and isoprene are not completely understood. In this study, we investigated whether aerobic conditions affected gene expression levels involved in the isoprenoid biosynthesis pathway that includes the mevalonate and isoprene biosynthesis pathways in Enterococcus gilvus using real-time quantitative reverse transcription PCR. NADH oxidase (nox) and superoxide dismutase (sod) gene expression levels were investigated as controls for aerobic conditions. The expression levels of nox and sod under aerobic conditions were 7.2- and 8.0-fold higher, respectively, than those under anaerobic conditions. Aerobic conditions concomitantly increased the expression levels of crtNM carotenoid biosynthesis genes. HMG-CoA synthase gene expression levels in the mevalonate pathway were only slightly increased under aerobic conditions, whereas the expression levels of HMG-CoA reductase and five other genes in the isoprene biosynthesis pathways were 1.2-2.3-fold higher than those under anaerobic conditions. These results demonstrated that aerobic conditions could increase the expression levels of genes involved in the isoprenoid biosynthesis pathway via mevalonate in E. gilvus.

  5. Evaluation of alkyne-modified isoprenoids as chemical reporters of protein prenylation.

    Science.gov (United States)

    DeGraw, Amanda J; Palsuledesai, Charuta; Ochocki, Joshua D; Dozier, Jonathan K; Lenevich, Stepan; Rashidian, Mohammad; Distefano, Mark D

    2010-12-01

    Protein prenyltransferases catalyze the attachment of C15 (farnesyl) and C20 (geranylgeranyl) groups to proteins at specific sequences localized at or near the C-termini of specific proteins. Determination of the specific protein prenyltransferase substrates affected by the inhibition of these enzymes is critical for enhancing knowledge of the mechanism of such potential drugs. Here, we investigate the utility of alkyne-containing isoprenoid analogs for chemical proteomics experiments by showing that these compounds readily penetrate mammalian cells in culture and become incorporated into proteins that are normally prenylated. Derivatization via Cu(I) catalyzed click reaction with a fluorescent azide reagent allows the proteins to be visualized and their relative levels to be analyzed. Simultaneous treatment of cells with these probes and inhibitors of prenylation reveals decreases in the levels of some but not all of the labeled proteins. Two-dimensional electrophoretic separation of these labeled proteins followed by mass spectrometric analysis allowed several labeled proteins to be unambiguously identified. Docking experiments and density functional theory calculations suggest that the substrate specificity of protein farnesyl transferase may vary depending on whether azide- or alkyne-based isoprenoid analogs is employed. These results demonstrate the utility of alkyne-containing analogs for chemical proteomic applications.

  6. Conversion of Isoprenoid Oil by Catalytic Cracking and Hydrocracking over Nanoporous Hybrid Catalysts

    Directory of Open Access Journals (Sweden)

    Toshiyuki Kimura

    2012-01-01

    Full Text Available In order to produce petroleum alternatives from biomass, a significant amount of research has been focused on oils from microalgae due to their origin, which would not affect food availability. Nanoporous hybrid catalysts composed of ns Al2O3 and zeolites have been proven to be very useful compared to traditional catalysts in hydrotreating (HT, hydrocracking (HC, and catalytic cracking (CC of large molecules. To evaluate the reaction scheme and products from model isoprenoid compounds of microalgae oil, nanoporous hybrid catalyst technologies (CC: ns Al2O3/H-USY and ns Al2O3/H-GaAlMFI; HC: [Ni-Mo/γ-Al2O3]/ns Al2O3/H-beta were studied. The major product from CC on ns Al2O3/H-USY was highly aromatic gasoline, while the product from HC was half-isoparaffinic/olefinic kerosene. Although more than 50 wt% of the products from HT/CC on the USY catalyst was liquefied petroleum gas due to overcracking, the product from HT/CC on the MFI catalyst was high-octane-number gasoline. Delightfully, the product from HT/HC was kerosene and its average number was 11, with more than 80 wt% being isoparaffinic. As a result, it was demonstrated that hydrotreating may convert isoprenoid oil from microalgae over nanoporous hybrid catalysts into a variety of products.

  7. Potato steroidal glycoalkaloid levels and the expression of key isoprenoid metabolic genes.

    Science.gov (United States)

    Krits, Pinchas; Fogelman, Edna; Ginzberg, Idit

    2007-12-01

    The potato steroidal glycoalkaloids (SGA) are toxic secondary metabolites, and their total content in tubers should not exceed 20 mg/100 g fresh weight. The two major SGA in cultivated potato (Solanum tuberosum) are alpha-chaconine and alpha-solanine. SGA biosynthetic genes and the genetic factors that control their expression have not yet been determined. In the present study, potato genotypes exhibiting different levels of SGA content showed an association between high SGA levels in their leaves and tubers and high expression of 3-hydroxy-3-methylglutaryl coenzyme A reductase 1 (hmg1) and squalene synthase 1 (pss1), genes of the mevalonic/isoprenoid pathway. Transcripts of other key enzymes of branches of the isoprenoid pathway, vetispiradiene/sesquiterpene synthase (pvs1) and sterol C24-methyltransferase type1 (smt1), were undetectable or exhibited stable expression regardless of SGA content, respectively, suggesting facilitated precursor flow to the SGA biosynthetic branch. The transcript ratio of solanidine glucosyltransferase (sgt2) to solanidine galactosyltransferase (sgt1) was correlated to the documented chaconine-to-solanine ratio in the tested genotypes. Significantly higher expression of hmg1, pss1, smt1, sgt1 and sgt2 was monitored in the tuber phelloderm than in the parenchyma of the tuber's flesh, targeting the former as the main SGA-producing tissue in the tuber, in agreement with the known high SGA content in the layers directly under the tuber skin.

  8. Conversion of isoprenoid oil by catalytic cracking and hydrocracking over nanoporous hybrid catalysts.

    Science.gov (United States)

    Kimura, Toshiyuki; Liu, Chen; Li, Xiaohong; Maekawa, Takaaki; Asaoka, Sachio

    2012-01-01

    In order to produce petroleum alternatives from biomass, a significant amount of research has been focused on oils from microalgae due to their origin, which would not affect food availability. Nanoporous hybrid catalysts composed of ns Al₂O₃ and zeolites have been proven to be very useful compared to traditional catalysts in hydrotreating (HT), hydrocracking (HC), and catalytic cracking (CC) of large molecules. To evaluate the reaction scheme and products from model isoprenoid compounds of microalgae oil, nanoporous hybrid catalyst technologies (CC: ns Al₂O₃/H-USY and ns Al₂O₃/H-GaAlMFI; HC: [Ni-Mo/γ-Al₂O₃]/ns Al₂O₃/H-beta) were studied. The major product from CC on ns Al₂O₃/H-USY was highly aromatic gasoline, while the product from HC was half-isoparaffinic/olefinic kerosene. Although more than 50 wt% of the products from HT/CC on the USY catalyst was liquefied petroleum gas due to overcracking, the product from HT/CC on the MFI catalyst was high-octane-number gasoline. Delightfully, the product from HT/HC was kerosene and its average number was 11, with more than 80 wt% being isoparaffinic. As a result, it was demonstrated that hydrotreating may convert isoprenoid oil from microalgae over nanoporous hybrid catalysts into a variety of products.

  9. Incineration of oxygenated volatile organic compounds. Experimental study and kinetic modeling of the oxidation of methyl ethyl ketone, ethyl acetate and butan-2-ol in methane flames; Incineration de composes organiques volatils oxygenes. Etude experimentale et modelisation cinetique de l'oxydation de la methyl ethyl cetone, de l'acetate d'ethyle et du butan-2-ol dans des flammes de methane

    Energy Technology Data Exchange (ETDEWEB)

    Decottignies, V.

    2000-12-01

    This work deals with the low pressure (0.05 atm) degradation of three volatile organic compounds (VOCs): methyl-ethyl-ketone, ethyl acetate and butan-2-ol, in premixed stoichiometric laminar methane flames seeded with 1 to 3% of each VOC. Molar fraction profiles of species have been obtained using microprobe sampling coupled with a gas chromatography and a mass spectroscopy analysis. Temperature profiles have been obtained using the covered thermocouple technique in the presence of the microprobe. The addition of a VOC in the initial reagents mixture leads to an increase of the quantity of intermediate hydrocarbon compounds and in particular of some soot precursor species. The degradation of VOCs leads to the formation of oxygenated intermediates like methanol, dimethyl-ether, acetaldehyde, propanal, acetone and vinyl acetate, the type of VOC having an effect on the quantities produced. The degradation of a VOC can lead to the formation of more toxic or polluting compounds (methyl vinyl ketone, acetic acid and acrolein) than the VOC itself. In the conditions of the study, the intermediate compounds are totally destructed inside the reactional area of the flame front and are no more present in the burnt gases. Sub-mechanisms of VOC oxidation have been developed using experimental observations and the most recent recommendations of the literature. These sub-mechanisms comprise 49 species involved in 241 elementary reactions. Their validation has been performed by comparing the experiment with the kinetic modeling on the molar fraction profiles of the detected species. Experimental data are well reproduced by the model for most species. The addition of a VOC inside the initial reagents mixture creates an important reactivity increase, in particular in the case of butan-2-ol seeded flames. The analysis of reactional ways has permitted to draw out the main reactions responsible for the degradation of the 3 VOCs and the ways of formation and consumption of the

  10. Organic geochemical studies of a Messinian evaporitic basin, Northern Apennines (Italy) II. Isoprenoid and n-alkyl thiophenes and thiolanes

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Haven, H.L. ten; Leeuw, J.W. de; Schenck, P.A.

    1986-01-01

    Series of n-alkyl and isoprenoid thiophenes and thiolanes, most of which have not been previously reported, have been identified in an extract from a Messinian (Upper Miocene)layer deposited under hypersaline, euxinic conditions. The identifications were based on mass spectra and chromatographic dat

  11. Arabidopsis GERANYLGERANYL DIPHOSPHATE SYNTHASE 11 is a hub isozyme required for the production of most photosynthesis-related isoprenoids.

    Science.gov (United States)

    Ruiz-Sola, M Águila; Coman, Diana; Beck, Gilles; Barja, M Victoria; Colinas, Maite; Graf, Alexander; Welsch, Ralf; Rütimann, Philipp; Bühlmann, Peter; Bigler, Laurent; Gruissem, Wilhelm; Rodríguez-Concepción, Manuel; Vranová, Eva

    2016-01-01

    Most plastid isoprenoids, including photosynthesis-related metabolites such as carotenoids and the side chain of chlorophylls, tocopherols (vitamin E), phylloquinones (vitamin K), and plastoquinones, derive from geranylgeranyl diphosphate (GGPP) synthesized by GGPP synthase (GGPPS) enzymes. Seven out of 10 functional GGPPS isozymes in Arabidopsis thaliana reside in plastids. We aimed to address the function of different GGPPS paralogues for plastid isoprenoid biosynthesis. We constructed a gene co-expression network (GCN) using GGPPS paralogues as guide genes and genes from the upstream and downstream pathways as query genes. Furthermore, knock-out and/or knock-down ggpps mutants were generated and their growth and metabolic phenotypes were analyzed. Also, interacting protein partners of GGPPS11 were searched for. Our data showed that GGPPS11, encoding the only plastid isozyme essential for plant development, functions as a hub gene among GGPPS paralogues and is required for the production of all major groups of plastid isoprenoids. Furthermore, we showed that the GGPPS11 protein physically interacts with enzymes that use GGPP for the production of carotenoids, chlorophylls, tocopherols, phylloquinone, and plastoquinone. GGPPS11 is a hub isozyme required for the production of most photosynthesis-related isoprenoids. Both gene co-expression and protein-protein interaction likely contribute to the channeling of GGPP by GGPPS11. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

  12. Identification of long-chain isoprenoid alkylbenzenes in sediments and crude oils

    Science.gov (United States)

    Sinninghe Damsté, Jaap S.; Kock-van Dalen, A. C.; de Leeuw, Jan W.

    1988-11-01

    A series of novel methylated phytanylbenzenes (phytanylbenzene, 1-methyl-3-phytanylbenzene, 1,4-dimethyl-2-phytanylbenzene, 1,2-dimethyl-4-phytanylbenzene and 1,2,4-trimethyl-5-phytanylbenzene) have been identified in sediment extracts and oils ranging in age from Miocene to Permian. Identifications were based on comparison of mass spectra and Chromatographie data of synthetic methylated phytanylbenzenes with those of geologically occurring methylated phytanylbenzenes and by coinjections with the standards. Although methylated phytanylbenzenes are structurally related to the methylated 2-methyl-2-(4,8,12-trimethyltridecyl)chromans, components also present in the samples studied, the former do not appear to be the diagenetic derivatives of the latter. The methylated phytanylbenzenes are thought to be derived diagenetically from isoprenoid quinones or may represent a direct biosynthetic origin from specific archaebacteria.

  13. Isoprenoid biosynthesis. Metabolite profiling of peppermint oil gland secretory cells and application to herbicide target analysis.

    Science.gov (United States)

    Lange, B M; Ketchum, R E; Croteau, R B

    2001-09-01

    Two independent pathways operate in plants for the synthesis of isopentenyl diphosphate and dimethylallyl diphosphate, the central intermediates in the biosynthesis of all isoprenoids. The mevalonate pathway is present in the cytosol, whereas the recently discovered mevalonate-independent pathway is localized to plastids. We have used isolated peppermint (Mentha piperita) oil gland secretory cells as an experimental model system to study the effects of the herbicides fosmidomycin, phosphonothrixin, methyl viologen, benzyl viologen, clomazone, 2-(dimethylamino)ethyl diphosphate, alendronate, and pamidronate on the pools of metabolites related to monoterpene biosynthesis via the mevalonate-independent pathway. A newly developed isolation protocol for polar metabolites together with an improved separation and detection method based on liquid chromatography-mass spectrometry have allowed assessment of the enzyme targets for a number of these herbicides.

  14. Enhancing isoprenoid production through systematically assembling and modulating efflux pumps in Escherichia coli.

    Science.gov (United States)

    Wang, Jian-Feng; Xiong, Zhi-Qiang; Li, Shi-Yuan; Wang, Yong

    2013-09-01

    Enhancement of the cellular exportation of heterologous compounds is an important aspect to improve the product yield in microbial cell factory. Efflux pumps can expel various intra- or extra-cellular substances out of microbial hosts and increase the cellular tolerance. Thus in this study, by using the hydrophobic sesquiterpene (amorphadiene) and diterpene (kaurene) as two model compounds, we attempted to improve isoprenoid production through systematically engineering the efflux pumps in Escherichia coli BL21(DE3). The pleiotropic resistant pumps, AcrAB-TolC, MdtEF-TolC from E. coli and heterologous MexAB-OprM pump from Pseudomonas aeruginosa, were overexpressed, assembled, and finely modulated. We found that overexpression of AcrB and TolC components can effectively enhance the specific yield of amorphadiene and kaurene, e.g., 31 and 37 % improvement for amorphadiene compared with control, respectively. The heterologous MexB component can enhance kaurene production with 70 % improvement which is more effective than TolC and AcrB. The results suggest that the three components of tripartite efflux pumps play varied effect to enhance isoprenoid production. Considering the highly organized structure of efflux pumps and importance of components interaction, various component combinations were constructed and the copy number of key components AcrB and TolC was finely modulated as well. The results exhibit that the combination TolC and TolC and AcrB improved the specific yield of amorphadiene with 118 %, and AcrA and TolC and AcrB improved that of kaurene with 104 %. This study indicates that assembling and finely modulating efflux pumps is an effective strategy to improve the production of heterologous compounds in E. coli.

  15. A transcriptional analysis of carotenoid, chlorophyll and plastidial isoprenoid biosynthesis genes during development and osmotic stress responses in Arabidopsis thaliana

    KAUST Repository

    Meier, Stuart

    2011-05-19

    Background: The carotenoids are pure isoprenoids that are essential components of the photosynthetic apparatus and are coordinately synthesized with chlorophylls in chloroplasts. However, little is known about the mechanisms that regulate carotenoid biosynthesis or the mechanisms that coordinate this synthesis with that of chlorophylls and other plastidial synthesized isoprenoid-derived compounds, including quinones, gibberellic acid and abscisic acid. Here, a comprehensive transcriptional analysis of individual carotenoid and isoprenoid-related biosynthesis pathway genes was performed in order to elucidate the role of transcriptional regulation in the coordinated synthesis of these compounds and to identify regulatory components that may mediate this process in Arabidopsis thaliana.Results: A global microarray expression correlation analysis revealed that the phytoene synthase gene, which encodes the first dedicated and rate-limiting enzyme of carotenogenesis, is highly co-expressed with many photosynthesis-related genes including many isoprenoid-related biosynthesis pathway genes. Chemical and mutant analysis revealed that induction of the co-expressed genes following germination was dependent on gibberellic acid and brassinosteroids (BR) but was inhibited by abscisic acid (ABA). Mutant analyses further revealed that expression of many of the genes is suppressed in dark grown plants by Phytochrome Interacting transcription Factors (PIFs) and activated by photoactivated phytochromes, which in turn degrade PIFs and mediate a coordinated induction of the genes. The promoters of PSY and the co-expressed genes were found to contain an enrichment in putative BR-auxin response elements and G-boxes, which bind PIFs, further supporting a role for BRs and PIFs in regulating expression of the genes. In osmotically stressed root tissue, transcription of Calvin cycle, methylerythritol 4-phosphate pathway and carotenoid biosynthesis genes is induced and uncoupled from that of

  16. A transcriptional analysis of carotenoid, chlorophyll and plastidial isoprenoid biosynthesis genes during development and osmotic stress responses in Arabidopsis thaliana

    Directory of Open Access Journals (Sweden)

    Vallabhaneni Ratnakar

    2011-05-01

    Full Text Available Abstract Background The carotenoids are pure isoprenoids that are essential components of the photosynthetic apparatus and are coordinately synthesized with chlorophylls in chloroplasts. However, little is known about the mechanisms that regulate carotenoid biosynthesis or the mechanisms that coordinate this synthesis with that of chlorophylls and other plastidial synthesized isoprenoid-derived compounds, including quinones, gibberellic acid and abscisic acid. Here, a comprehensive transcriptional analysis of individual carotenoid and isoprenoid-related biosynthesis pathway genes was performed in order to elucidate the role of transcriptional regulation in the coordinated synthesis of these compounds and to identify regulatory components that may mediate this process in Arabidopsis thaliana. Results A global microarray expression correlation analysis revealed that the phytoene synthase gene, which encodes the first dedicated and rate-limiting enzyme of carotenogenesis, is highly co-expressed with many photosynthesis-related genes including many isoprenoid-related biosynthesis pathway genes. Chemical and mutant analysis revealed that induction of the co-expressed genes following germination was dependent on gibberellic acid and brassinosteroids (BR but was inhibited by abscisic acid (ABA. Mutant analyses further revealed that expression of many of the genes is suppressed in dark grown plants by Phytochrome Interacting transcription Factors (PIFs and activated by photoactivated phytochromes, which in turn degrade PIFs and mediate a coordinated induction of the genes. The promoters of PSY and the co-expressed genes were found to contain an enrichment in putative BR-auxin response elements and G-boxes, which bind PIFs, further supporting a role for BRs and PIFs in regulating expression of the genes. In osmotically stressed root tissue, transcription of Calvin cycle, methylerythritol 4-phosphate pathway and carotenoid biosynthesis genes is induced

  17. Volatile Organic Compounds (VOCs)

    Science.gov (United States)

    ... Contact Us Share Volatile Organic Compounds' Impact on Indoor Air Quality On this page: Introduction Sources Health Effects Levels in Homes Steps to Reduce Exposure Standards or Guidelines Additional Resources Introduction Volatile organic compounds ( ...

  18. From emissions to ambient mixing ratios: on-line seasonal field measurements of volatile organic compounds over a Norway spruce dominated forest in central Germany

    Science.gov (United States)

    Bourtsoukidis, E.; Williams, J.; Kesselmeier, J.; Jacobi, S.; Bonn, B.

    2013-11-01

    Biogenic volatile organic compounds (BVOC) are substantial contributors to atmospheric chemistry and physics and demonstrate the close relationship between biosphere and atmosphere. Their emission rates are highly sensitive to meteorological and environmental changes with concomitant impacts on atmospheric chemistry. We have investigated seasonal isoprenoid and oxygenated VOC (oxVOC) fluxes from a Norway spruce (Picea abies) tree in Central Germany and explored the emission responses under various atmospheric conditions. Emission rates were quantified by using dynamic branch enclosure and Proton Transfer Reaction-Mass Spectrometry (PTR-MS) techniques. Additionally, ambient mixing ratios were derived through application of a new box model treatment on the dynamic chamber measurements. These are compared in terms of abundance and origin with the corresponding emissions. Isoprenoids govern the BVOC emissions from Norway spruce, with monoterpenes and sesquiterpenes accounting for 50.8 ± 7.2% and 19.8 ± 8.1% respectively of the total emissions. Normalizing the VOC emission rates, we have observed a trend of reduction of carbon containing emissions from April to November, with an enhancement of oxVOC. Highest emission rates were observed in June for all measured species, with the exception of sesquiterpenes that were emitted most strongly in April. We exploit the wide range of conditions experienced at the site to filter the dataset with a combination of temperature, ozone and absolute humidity values in order to derive the emission potential and temperature dependency development for the major chemical species investigated. A profound reduction of monoterpene emission potential (E30) and temperature dependency (β) was found under low temperature regimes, combined with low ozone levels (E30MT, LTLO3=56 ± 9.1 ng g(dw)-1 h-1, βMT,LTLO3=0.03±0.01 K-1) while a combination of both stresses was found to alter their emissions responses with respect to temperature

  19. Seasonal cycles of biogenic volatile organic compound fluxes and concentrations in a California citrus orchard

    Directory of Open Access Journals (Sweden)

    S. Fares

    2012-10-01

    Full Text Available Orange trees are widely cultivated in Mediterranean climatic regions where they are an important agricultural crop. Citrus have been characterized as emitters of volatile organic compounds (VOC in chamber studies under controlled environmental conditions, but an extensive characterization at field scale has never been performed using modern measurement methods, and is particularly needed considering the complex interactions between the orchards and the polluted atmosphere in which Citrus is often cultivated. For one year, in a Valencia orange orchard in Exeter, California, we measured fluxes using PTRMS (Proton Transfer Reaction Mass Spectrometer and eddy covariance for the most abundant VOC typically emitted from citrus vegetation: methanol, acetone, and isoprenoids. Concentration gradients of additional oxygenated and aromatic compounds from the ground level to above the canopy were also measured. In order to characterize concentrations of speciated biogenic VOC (BVOC in leaves, we analyzed leaf content by GC-MS (Gas Chromatography – Mass Spectrometery regularly throughout the year. We also characterized in more detail concentrations of speciated BVOC in the air above the orchard by in-situ GC-MS during a few weeks in spring flowering and summer periods. Here we report concentrations and fluxes of the main VOC species emitted by the orchard, discuss how fluxes measured in the field relate to previous studies made with plant enclosures, and describe how VOC content in leaves and emissions change during the year in response to phenological and environmental parameters. The orchard was a source of monoterpenes and oxygenated VOC. The highest emissions were observed during the springtime flowering period, with mid-day fluxes above 2 nmol m−2 s−1 for methanol and up to 1 nmol m−2 s−1 for acetone and monoterpenes. During hot summer days emissions were not as high as we expected considering the

  20. Changes in photosynthesis, mesophyll conductance to CO2, and isoprenoid emissions in Populus nigra plants exposed to excess nickel.

    Science.gov (United States)

    Velikova, Violeta; Tsonev, Tsonko; Loreto, Francesco; Centritto, Mauro

    2011-05-01

    Poplar (Populus nigra) plants were grown hydroponically with 30 and 200 μM Ni (Ni30 and Ni200). Photosynthesis limitations and isoprenoid emissions were investigated in two leaf types (mature and developing). Ni stress significantly decreased photosynthesis, and this effect depended on the leaf Ni content, which was lower in mature than in developing leaves. The main limitations to photosynthesis were attributed to mesophyll conductance and metabolism impairment. In Ni-stressed developing leaves, isoprene emission was significantly stimulated. We attribute such stimulation to the lower chloroplastic [CO2] than in control leaves. However chloroplastic [CO2] did not control isoprene emission in mature leaves. Ni stress induced the emission of cis-β-ocimene in mature leaves, and of linalool in both leaf types. Induced biosynthesis and emission of isoprenoids reveal the onset of antioxidant processes that may also contribute to reduce Ni stress, especially in mature poplar leaves. Copyright © 2010 Elsevier Ltd. All rights reserved.

  1. The mitochondrial PPR protein LOVASTATIN INSENSITIVE 1 plays regulatory roles in cytosolic and plastidial isoprenoid biosynthesis through RNA editing.

    Science.gov (United States)

    Tang, Jianwei; Kobayashi, Keiko; Suzuki, Masashi; Matsumoto, Shogo; Muranaka, Toshiya

    2010-02-01

    Unlike animals, plants synthesize isoprenoids via two pathways, the cytosolic mevalonate (MVA) pathway and the plastidial 2-C-methyl-d-erythritol-4-phosphate (MEP) pathway. Little information is known about the mechanisms that regulate these complex biosynthetic networks over multiple organelles. To understand such regulatory mechanisms of the biosynthesis of isoprenoids in plants, we previously characterized the Arabidopsis mutant, lovastatin insensitive 1 (loi1), which is resistant to lovastatin and clomazone, specific inhibitors of the MVA and MEP pathways, respectively. LOI1 encodes a pentatricopeptide repeat (PPR) protein localized in mitochondria that is thought to have RNA binding ability and function in post-transcriptional regulation of mitochondrial gene expression. LOI1 belongs to the DYW subclass of PPR proteins, which is hypothesized to be correlated with RNA editing. As a result of analysis of RNA editing of mitochondrial genes in loi1, a defect in RNA editing of three genes, nad4, ccb203 and cox3, was identified in loi1. These genes are related to the respiratory chain. Wild type (WT) treated with some respiration inhibitors mimicked the loi1 phenotype. Interestingly, HMG-CoA reductase activity of WT treated with lovastatin combined with antimycin A, an inhibitor of complex III in the respiratory chain, was higher than that of WT treated with only lovastatin, despite the lack of alteration of transcript or protein levels of HMGR. These results suggest that HMGR enzyme activity is regulated through the respiratory cytochrome pathway. Although various mechanisms exist for isoprenoid biosynthesis, our studies demonstrate the novel possibility that mitochondrial respiration plays potentially regulatory roles in isoprenoid biosynthesis.

  2. Precise precursor rebalancing for isoprenoids production by fine control of gapA expression in Escherichia coli.

    Science.gov (United States)

    Jung, Juyoung; Lim, Jae Hyung; Kim, Se Yeon; Im, Dae-Kyun; Seok, Joo Yeon; Lee, Seung-Jae V; Oh, Min-Kyu; Jung, Gyoo Yeol

    2016-11-01

    Biosynthesis of isoprenoids via the 1-deoxy-D-xylulose-5-phosphate (DXP) pathway requires equimolar glyceraldehyde 3-phosphate and pyruvate to divert carbon flux toward the products of interest. Here, we demonstrate that precursor balancing is one of the critical steps for the production of isoprenoids in Escherichia coli. First, the implementation of the synthetic lycopene production pathway as a model system and the amplification of the native DXP pathway were accomplished using synthetic constitutive promoters and redesigned 5'-untranslated regions (5'-UTRs). Next, fine-controlled precursor balancing was investigated by tuning phosphoenolpyruvate synthase (PpsA) or glyceraldehyde 3-phosphate dehydrogenase (GAPDH). The results showed that tuning-down of gapA improved the specific lycopene content by 45% compared to the overexpression of ppsA. The specific lycopene content in the strains with down-regulated gapA increased by 97% compared to that in the parental strain. Our results indicate that gapA is the best target for precursor balancing to increase biosynthesis of isoprenoids.

  3. Natural isoprenoids inhibit LPS-induced-production of cytokines and nitric oxide in aminobisphosphonate-treated monocytes.

    Science.gov (United States)

    Marcuzzi, Annalisa; Tommasini, Alberto; Crovella, Sergio; Pontillo, Alessandra

    2010-06-01

    The inhibition of mevalonate pathway through genetic defects (mevalonate kinase deficiency, MKD) or pharmacologic drugs (aminobisphosphonates) causes a shortage of intermediate compounds and, in particular, of geranylgeranyl-pyrophosphate (GGPP) associated to the activation of caspase-1 and IL-1beta release. Geraniol (GOH), farnesol (FOH), geranylgeraniol (GGOH) and menthol (MOH), due to their isoprenoid structure, are supposed to enter the mevalonate pathway and to by-pass the biochemical block, reconstituting the pathway. Considering the already known side effects of aminobisphosphonates, and the lack of a specific treatment for MKD, we evaluated the impact of these natural isoprenoids compounds in a RAW cell lines chemically treated with the aminobisphosphonate alendronate, and in monocytes isolated from 2 patients affected by MKD. GOH, FOH, GGOH and MOH were all capable to diminish inflammatory marker levels induced by LPS. These natural isoprenoids could be proposed as novel therapeutic approach for the still orphan drug MKD, but also considered for the evaluation of possible inflammatory side effects of aminobisphosphonates.

  4. New insight in isoprenoids biosynthesis process and future prospects for drug designing in Plasmodium

    Directory of Open Access Journals (Sweden)

    Gagandeep Singh Saggu

    2016-09-01

    Full Text Available The MEP (Methyl Erythritol Phosphate isoprenoids biosynthesis pathway is an attractive drug target to combat malaria, due to its uniqueness and indispensability for the parasite. It is functional in the apicoplast of Plasmodium and its products get transported to the cytoplasm, where they participate in glycoprotein synthesis, electron transport chain, tRNA modification and several other biological processes. Several compounds have been tested against the enzymes involved in this pathway and amongst them Fosmidomycin, targeted against IspC (DXP reductoisomerase enzyme and MMV008138 targeted against IspD enzyme have shown good anti-malarial activity in parasite cultures. Fosmidomycin is now-a-days prescribed clinically, however, less absorption, shorter half-life, and toxicity at higher doses, limits its use as an anti-malarial. The potential of other enzymes of the pathway as candidate drug targets has also been determined. This review details the various drug molecules tested against these targets with special emphasis to Plasmodium. We corroborate that MEP pathway functional within the apicoplast of Plasmodium is a major drug target, especially during erythrocytic stages. However, the major bottlenecks, bioavailability and toxicity of the new molecules needs to be addressed, before considering any new molecule as a potent antimalarial.

  5. Applicability of highly branched isoprenoids as a sea ice proxy in the Ross Sea

    Science.gov (United States)

    Kim, Jung-Hyun; Lee, Jae Il; Belt, Simon T.; Gal, Jong-Ku; Smik, Lukas; Shin, Kyung-Hoon

    2016-04-01

    Sea ice is an integral component of the polar climate system, constraining the effect of changing surface albedo, ocean-atmosphere heat exchanges, the formation of deep and intermediate waters that participate in driving the meridional overturning circulation and thus global climate. In recent years, a mono-unsaturated highly branched isoprenoid (HBI) alkene which is biosynthesised by certain sea ice diatoms during the spring bloom and, upon ice melt, deposited into underlying sediments, has been uniquely observed in Arctic sea ice and in Arctic sediments. Hence, the term IP25 (ice proxy with 25 carbon atoms) was proposed to distinguish this compound from other HBI isomers and has become an established proxy for the reconstruction of Arctic sea ice. In contrast, a monounsaturated HBI alkene, i.e. IP25, has not been observed in sea ice or sediments from the Antarctic. Hence, the application of diene and triene HBI concentrations and the resulting diene/triene (D/T) ratio was alternatively introduced as sea ice/open water indicators in the Southern Ocean. However, there is still lack of data covering the wide areas around the Antarctic, especially from the Ross Sea. Hence, we investigated surface sediment samples from the Ross Sea (n=14) collected during the R/V ARAON cruise in 2015 as well as from the Antarctic Peninsula (n=17) collected during several R/V ARAON cruises between 2001 and 2013. We will present our preliminary results and will discuss the applicability of the HBI in the Ross Sea.

  6. Nonionic diethanolamide amphiphiles with isoprenoid-type hydrocarbon chains: thermotropic and lyotropic liquid crystalline phase behaviour

    Energy Technology Data Exchange (ETDEWEB)

    Sagnella, Sharon M.; Conn, Charlotte E.; Krodkiewska, Irena; Drummond, Calum J. (CSIRO/MSE)

    2014-09-24

    The thermotropic and lyotropic liquid crystalline phase behaviour of a series of diethanolamide amphiphiles with isoprenoid-type hydrocarbon chains (geranoyl, H-farnesoyl, and phytanoyl) has been investigated. When neat, both H-farnesoyl and phytanoyl diethanolamide form a smectic liquid crystalline structure at sub-zero temperatures. In addition, all three diethanolamides exhibit a glass transition temperature at around -73 C. Geranoyl diethanolamide forms a lamellar crystalline phase with a lattice parameter of 17.4 {angstrom} following long term storage accompanied by the loss of the glass transition. In the presence of water, H-farnesoyl and phytanoyl diethanolamide form lyotropic liquid crystalline phases, whilst geranoyl diethanolamide forms an L{sub 2} phase. H-farnesoyl diethanolamide forms a fluid lamellar phase (L{sub {alpha}}) at room temperature and up to {approx} 40 C. Phytanoyl diethanolamide displays a rich mesomorphism forming the inverse diamond (Q{sub II}{sup D}) and gyroid (Q{sub II}{sup G}) bicontinuous cubic phases in addition to an L{sub {alpha}} phase.

  7. Isoprenoid emission of oak species typical for the Mediterranean area: Source strength and controlling variables

    Science.gov (United States)

    Steinbrecher, Rainer; Hauff, Karin; Rabong, Richard; Steinbrecher, Jutta

    Measurements of isoprenoid emission on five Mediterranean oak species in the field revealed that Quercus frainetto, Quercus petraea and Quercus pubescens are strong emitters of isoprene. In contrast Quercus cerris and Quercus suber emitted no significant amounts of isoprene and monoterpenes. For Q. pubenscens and Q. frainetto median emission factors of 16.68 nmol m -2 s -1 (86.06 μg g -1 dw h -1) and 30.72 nmol m -2 s -1 (133.95 μg g -1 dw h -1 were calculated, respectively. The 25 to 75 percentiles span of the emission factor data sets ranged from - 53% to + 56% of the median values. Light and temperature are the main controlling factors for isoprene emission. The influence of other environmental and plant physiological parameters on the isoprene emission is discussed. The "Guenther" emission algorithm is able to predict the daily maximum of the isoprene emission within the plant specific uncertainty range. However, the morning increase and the afternoon drop in the isoprene emission is not well parameterized. On the basis of process oriented models for the synthesis of isoprene in plants, a further reduction in the uncertainty may be achieved resulting in a more reliable prediction of short-time variation in isoprene emission.

  8. Cloning and characterization of farnesyl pyrophosphate synthase from the highly branched isoprenoid producing diatom Rhizosolenia setigera.

    Science.gov (United States)

    Ferriols, Victor Marco Emmanuel N; Yaginuma, Ryoko; Adachi, Masao; Takada, Kentaro; Matsunaga, Shigeki; Okada, Shigeru

    2015-05-21

    The diatom Rhizosolenia setigera Brightwell produces highly branched isoprenoid (HBI) hydrocarbons that are ubiquitously present in marine environments. The hydrocarbon composition of R. setigera varies between C25 and C30 HBIs depending on the life cycle stage with regard to auxosporulation. To better understand how these hydrocarbons are biosynthesized, we characterized the farnesyl pyrophosphate (FPP) synthase (FPPS) enzyme of R. setigera. An isolated 1465-bp cDNA clone contained an open reading frame spanning 1299-bp encoding a protein with 432 amino acid residues. Expression of the RsFPPS cDNA coding region in Escherichia coli produced a protein that exhibited FPPS activity in vitro. A reduction in HBI content from diatoms treated with an FPPS inhibitor, risedronate, suggested that RsFPPS supplies precursors for HBI biosynthesis. Product analysis by gas chromatography-mass spectrometry also revealed that RsFPPS produced small amounts of the cis-isomers of geranyl pyrophosphate and FPP, candidate precursors for the cis-isomers of HBIs previously characterized. Furthermore, RsFPPS gene expression at various life stages of R. setigera in relation to auxosporulation were also analyzed. Herein, we present data on the possible role of RsFPPS in HBI biosynthesis, and it is to our knowledge the first instance that an FPPS was cloned and characterized from a diatom.

  9. Thermochromatography study of volatile polonium species in various gas atmospheres

    CERN Document Server

    Maugeri, Emilio Andrea; Eichler, Robert; Piguet,David; Mendonça, Tania Melo; Stora, Thierry; Schumann, Dorothea

    2014-01-01

    Phenomena related to the volatilization of polonium and its compounds are critical issues for the safety assessment of the innovative lead–bismuth cooled type of nuclear reactor or accelerator driven systems. The formation and volatilization of different species of polonium and their interaction with fused silica was studied by thermochromatography using carrier gases with varied redox potential. The obtained results show that under inert and reducing conditions in the absence of moisture, elemental polonium is formed. Polonium compounds more volatile than elemental polonium can be formed if traces of moisture are present in both inert and reducing carrier gas. The use of dried oxygen as carrier gas leads to the formation of polonium oxides, which are less volatile than elemental polonium. It was also found that the volatility of polonium oxides increases with increasing oxidation state. In the presence of moisture in an oxidizing carrier gas, species are formed that are more volatile than the oxides and le...

  10. Emerging Equity Market Volatility

    OpenAIRE

    Geert Bekaert; Harvey, Campbell R.

    1995-01-01

    Returns in emerging capital markets are very different from returns in developed markets. While most previous research has focused on average returns, we analyze the volatility of the returns in emerging equity markets. We characterize the time-series of volatility in emerging markets and explore the distributional foundations of the variance process. Of particular interest is evidence of asymmetries in volatility and the evolution of the variance process after periods of capital market refor...

  11. Volatility in Equilibrium

    DEFF Research Database (Denmark)

    Bollerslev, Tim; Sizova, Natalia; Tauchen, George

    Stock market volatility clusters in time, carries a risk premium, is fractionally inte- grated, and exhibits asymmetric leverage effects relative to returns. This paper develops a first internally consistent equilibrium based explanation for these longstanding empirical facts. The model is cast......, and the dynamic cross-correlations of the volatility measures with the returns calculated from actual high-frequency intra-day data on the S&P 500 aggregate market and VIX volatility indexes....

  12. A model to assess the emission of individual isoprenoids emitted from Italian ecosystems

    Science.gov (United States)

    Kemper Pacheco, C. J.; Fares, S.; Loreto, F.; Ciccioli, P.

    2012-04-01

    The aim of this work was to develop a GIS-based model to estimate the emissions from the Italian forest ecosystems. The model was aimed at generating a species-specific emission inventory for isoprene and individual monoterpenes that could have been validated with experimental data collected in selected sites of the CARBOITALY network. The model was develop for the year 2006. At a resolution of 1 km2 with a daily time resolution. By using the emission rates of individual components obtained through several laboratory and field experiments carried out on different vegetation species of the Mediterranean basin, maps of individual isoprenoids were generated for the Italian ecosystems. The spatial distribution and fractional contents of vegetation species present in the Italian forest ecosystems was obtained by combining the CORINE IV land cover map with National Forest Inventory based on ground observations performed at local levels by individual Italian regions (22) in which the country is divided. In general, basal emission rates for individual isoprenoids was reported by Steinbrecher et al. 1997 and Karl et al. 2009 were used. In this case, classes were further subdivided into T and L+T emitters as functions of the active pool. In many instances, however they were revised based on the results obtained in our Institute through determinations performed at leaf, branch (cuvette method) or ecosystem level (REA and the gradient method). In the latter case, studies performed in Italy and/or Mediterranean countries were used. An empirical light extinction function as a function of the canopy type and structure was introduced. The algorithms proposed by (Guenther et al. 1993) were used, but, they were often adapted to fit with the experimental observations made in the Mediterranean Areas. They were corrected for a seasonality factor (Steinbrecher et al. 2009) taking into account a time lag in leaf sprouting due to the plant elevation. A simple parameterization with LAI was

  13. Dynamic Solution Injection: a new method for preparing pptv-ppbv standard atmospheres of volatile organic compounds

    Directory of Open Access Journals (Sweden)

    K. J. Jardine

    2010-07-01

    Full Text Available Proton Transfer Reaction-Mass Spectrometry (PTR-MS and thermal desorption Gas Chromatography-Mass Spectrometry (GC-MS allow for absolute quantification of a wide range of atmospheric volatile organic compounds (VOCs with concentrations in the ppbv to pptv range. Although often neglected, routine calibration is necessary for accurate quantification of VOCs by PTR-MS and GC-MS. Several gas calibration methods currently exist, including compressed gas cylinders, permeation tubes, diffusion tubes, and liquid injection. While each method has its advantages and limitations, no single technique has emerged that is capable of dynamically generating accurate concentrations of complex mixtures of VOCs over a large concentration range (ppbv to pptv, is technically simple and field portable, and affordable. We present the development of a new VOC calibration technique based on liquid injection with these features termed Dynamic Solution Injection (DSI. This method consists of injecting VOCs (0.1–0.5 mM dissolved in cyclohexane (PTR-MS or methanol (GC-MS into a 1.0 slpm flow of purified dilution gas in an unheated 25 mL glass vial. Upon changes in the injection flow rate (0.5–4.0 μL min−1, new VOC concentrations are reached within seconds to minutes, depending on the compound, with a liquid injection flow rate accuracy and precision of better than 7% and 4%, respectively. We demonstrate the utility of the DSI technique by calibrating a PTR-MS to seven different cyclohexane solutions containing a total of 34 different biogenic compounds including volatile isoprenoids, oxygenated VOCs, fatty acid oxidation products, aromatics, and dimethyl sulfide. In order to validate the new DSI method, a GC-MS and PTR-MS calibration intercomparison with VOC standards generated by dynamic dilution of NIST traceable permeation tubes (α-pinene, acetone, and ethanol and a compressed gas cylinder (acetaldehyde was made. The results revealed that while

  14. Staphylococcus aureus mevalonate kinase: isolation and characterization of an enzyme of the isoprenoid biosynthetic pathway.

    Science.gov (United States)

    Voynova, Natalya E; Rios, Sandra E; Miziorko, Henry M

    2004-01-01

    It has been proposed that isoprenoid biosynthesis in several gram-positive cocci depends on the mevalonate pathway for conversion of acetyl coenzyme A to isopentenyl diphosphate. Mevalonate kinase catalyzes a key reaction in this pathway. In this study the enzyme from Staphylococcus aureus was expressed in Escherichia coli, isolated in a highly purified form, and characterized. The overall amino acid sequence of this enzyme was very heterologous compared with the sequences of eukaryotic mevalonate kinases. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and analytical gel filtration chromatography suggested that the native enzyme is a monomer with a molecular mass of approximately 33 kDa. The specific activity was 12 U/mg, and the pH optimum was 7.0 to 8.5. The apparent K(m) values for R,S-mevalonate and ATP were 41 and 339 micro M, respectively. There was substantial substrate inhibition at millimolar levels of mevalonate. The sensitivity to feedback inhibition by farnesyl diphosphate and its sulfur-containing analog, farnesyl thiodiphosphate, was characterized. These compounds were competitive inhibitors with respect to ATP; the K(i) values were 46 and 45 micro M for farnesyl diphosphate and its thio analog, respectively. Parallel measurements with heterologous eukaryotic mevalonate kinases indicated that S. aureus mevalonate kinase is much less sensitive to feedback inhibition (K(i) difference, 3 orders of magnitude) than the human enzyme. In contrast, both enzymes tightly bound trinitrophenyl-ATP, a fluorescent substrate analog, suggesting that there are similarities in structural features that are important for catalytic function.

  15. Understanding Financial Market Volatility

    NARCIS (Netherlands)

    A. Opschoor (Anne)

    2014-01-01

    markdownabstract__Abstract__ Volatility has been one of the most active and successful areas of research in time series econometrics and economic forecasting in recent decades. Loosely speaking, volatility is defined as the average magnitude of fluctuations observed in some phenomenon over time. Wi

  16. Improving Garch Volatility Forecasts

    NARCIS (Netherlands)

    Klaassen, F.J.G.M.

    1998-01-01

    Many researchers use GARCH models to generate volatility forecasts. We show, however, that such forecasts are too variable. To correct for this, we extend the GARCH model by distinguishing two regimes with different volatility levels. GARCH effects are allowed within each regime, so that our model

  17. Understanding Financial Market Volatility

    NARCIS (Netherlands)

    A. Opschoor (Anne)

    2014-01-01

    markdownabstract__Abstract__ Volatility has been one of the most active and successful areas of research in time series econometrics and economic forecasting in recent decades. Loosely speaking, volatility is defined as the average magnitude of fluctuations observed in some phenomenon over

  18. Volatile metabolites from actinomycetes

    DEFF Research Database (Denmark)

    Scholler, C.E.G.; Gurtler, H.; Pedersen, R.

    2002-01-01

    Twenty-six Streptomyces spp. were screened for their volatile production capacity on yeast starch agar. The volatile organic compounds (VOCs) were concentrated on a porous polymer throughout an 8-day growth period. VOCs were analyzed by gas chromatography with flame ionization detection and ident...

  19. Role of minerals in the thermal alteration of organic matter. IV. Generation of n-alkanes, acyclic isoprenoids, and alkenes in laboratory experiments

    Energy Technology Data Exchange (ETDEWEB)

    Huizinga, B.J.; Tannenbaum, E.; Kaplan, I.R.

    1987-05-01

    A series of pyrolysis experiments, utilizing two different immature oil-prone kerogens mixed with common sedimentary minerals (calcite, illite, or Na-montmorillonite), was conducted to study the effects of minerals on the generation of n-alkanes, acyclic isoprenoids, and alkenes during laboratory-simulated catagenesis of kerogen. The influence of clay minerals on the aliphatic hydrocarbons is critically dependent on the water concentration during laboratory thermal maturation. Under extremely low contents of water, C/sub 12+/-range n-alkanes and acyclic isoprenoids are mostly destroyed by montmorillonite but undergo only a minor alteration with illite. Both clay minerals significantly reduce alkene formation during dry pyrolysis. Under hydrous conditions (mineral/water = 2:1), the effects of the clay minerals are substantially reduced. In addition, the dry-pyrolysis experiments show that illite and montmorillonite preferentially retain large amounts of the polar constituents of bitumen, but not n-alkanes of acyclic isoprenoids. Therefore, bitumen fractionation according to polarity differences occurs in the presence of these clay minerals. By this process, n-alkanes, and acyclic isoprenoids are concentrated in the bitumen fraction that is not strongly adsorbed on the clay matrices. In contrast, calcite has no significant influence on the thermal evolution of the hydrocarbons. In addition, calcite is incapable of retaining bitumen. Therefore, the fractionation of n-alkanes or acyclic isoprenoids relative to the polar constituents of bitumen is insignificant in the presence of calcite.

  20. Structure elucidation of C80, C81 and C82 isoprenoid tetraacids responsible for naphthenate deposition in crude oil production.

    Science.gov (United States)

    Lutnaes, Bjart F; Krane, Jostein; Smith, Ben E; Rowland, Steven J

    2007-06-21

    A series of C(80) isoprenoid 20-bis-16,16'-biphytanyl tetraacids has previously been found to be responsible for calcium naphthenate scaling in crude oil processing. This paper describes the structure elucidation by high-field NMR spectroscopy of the structures of the series of homologous C(80) tetraacids containing 4-8 five-membered rings. In addition, the structures of methyl-substituted C(81) and C(82) analogues containing 7 and 8 five-membered rings have been determined for the first time. The biosynthetic implications are discussed.

  1. Evolutionary diversification and characterization of the eubacterial gene family encoding DXR type II, an alternative isoprenoid biosynthetic enzyme.

    Science.gov (United States)

    Carretero-Paulet, Lorenzo; Lipska, Agnieszka; Pérez-Gil, Jordi; Sangari, Félix J; Albert, Victor A; Rodríguez-Concepción, Manuel

    2013-09-03

    Isoprenoids constitute a vast family of natural compounds performing diverse and essential functions in all domains of life. In most eubacteria, isoprenoids are synthesized through the methylerythritol 4-phosphate (MEP) pathway. The production of MEP is usually catalyzed by deoxyxylulose 5-phosphate reductoisomerase (DXR-I) but a few organisms use an alternative DXR-like enzyme (DXR-II). Searches through 1498 bacterial complete proteomes detected 130 sequences with similarity to DXR-II. Phylogenetic analysis identified three well-resolved clades: the DXR-II family (clustering 53 sequences including eleven experimentally verified as functional enzymes able to produce MEP), and two previously uncharacterized NAD(P)-dependent oxidoreductase families (designated DLO1 and DLO2 for DXR-II-like oxidoreductases 1 and 2). Our analyses identified amino acid changes critical for the acquisition of DXR-II biochemical function through type-I functional divergence, two of them mapping onto key residues for DXR-II activity. DXR-II showed a markedly discontinuous distribution, which was verified at several levels: taxonomic (being predominantly found in Alphaproteobacteria and Firmicutes), metabolic (being mostly found in bacteria with complete functional MEP pathways with or without DXR-I), and phenotypic (as no biological/phenotypic property was found to be preferentially distributed among DXR-II-containing strains, apart from pathogenicity in animals). By performing a thorough comparative sequence analysis of GC content, 3:1 dinucleotide frequencies, codon usage and codon adaptation indexes (CAI) between DXR-II sequences and their corresponding genomes, we examined the role of horizontal gene transfer (HGT), as opposed to an scenario of massive gene loss, in the evolutionary origin and diversification of the DXR-II subfamily in bacteria. Our analyses support a single origin of the DXR-II family through functional divergence, in which constitutes an exceptional model of

  2. Oxygen Therapy

    Science.gov (United States)

    Oxygen therapy is a treatment that provides you with extra oxygen. Oxygen is a gas that your body needs to function. Normally, your lungs absorb oxygen from the air you breathe. But some conditions ...

  3. Wet steam treatment with oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Ruehle, W.; Enkler, G. [EnBW Kraftwerke AG, Kernkraftwerk Philippsburg (Germany)

    1999-07-01

    After many years of excellent results using high all volatile treatment (HAVT) for operation of the secondary system of a PWR, flow assisted corrosion in the heating pipes of the intermediate steam reheaters has been experienced. Oxygen addition into the heating steam before the reheater is expected to improve the protective oxide layers formation. The reaction of oxygen with the alkalizing steam ingredients is described. (orig.)

  4. Idiosyncratic Volatility Puzzle

    DEFF Research Database (Denmark)

    Aslanidis, Nektarios; Christiansen, Charlotte; Lambertides, Neophytos;

    from a large pool of macroeconomic and Önancial variables. Cleaning for macro-Önance e§ects reverses the puzzling negative relation between returns and idiosyncratic volatility documented previously. Portfolio analysis shows that the e§ects from macro-Önance factors are economically strong......In this paper, we scrutinize the cross-sectional relation between idiosyncratic volatility and stock returns. As a novelty, the idiosyncratic volatility is obtained by conditioning upon macro-Önance factors as well as upon traditional asset pricing factors. The macro-Önance factors are constructed...

  5. 1-Deoxy-D-xylulose-5-phosphate synthase, a limiting enzyme for plastidic isoprenoid biosynthesis in plants.

    Science.gov (United States)

    Estévez, J M; Cantero, A; Reindl, A; Reichler, S; León, P

    2001-06-22

    The initial step of the plastidic 2C-methyl-D-erythritol 4-phosphate (MEP) pathway that produces isopentenyl diphosphate is catalyzed by 1-deoxy-d-xylulose-5-phosphate synthase. To investigate whether or not 1-deoxy-d-xylulose-5-phosphate synthase catalyzes a limiting step in the MEP pathway in plants, we produced transgenic Arabidopsis plants that over- or underexpress this enzyme. Compared with non-transgenic wild-type plants, the transgenic plants accumulate different levels of various isoprenoids such as chlorophylls, tocopherols, carotenoids, abscisic acid, and gibberellins. Phenotypically, the transgenic plants had slight alterations in growth and germination rates. Because the levels of several plastidic isoprenoids correlate with changes in 1-deoxy-D-xylulose-5-phosphate synthase levels, we conclude that this enzyme catalyzes one of the rate-limiting steps of the MEP biosynthetic pathway. Furthermore, since the product of the MEP pathway is isopentenyl diphosphate, our results suggest that in plastids the pool of isopentenyl diphosphate is limiting to isprenoid production.

  6. Identification of aryl isoprenoids in source rocks and crude oils: Biological markers for the green sulphur bacteria

    Science.gov (United States)

    Summons, R. E.; Powell, T. G.

    1987-03-01

    A series of C 13 to C 31 aryl isoprenoids (1-alkyl,2,3,6-trimethylbenzenes) have been identified in reef-hosted oils and their source rocks from the Middle and Upper Silurian of the Michigan Basin and Middle Devonian of the Alberta Basin, Canada. Their structure has been confirmed by unambiguous synthesis of the C 14 member of the series. Their structure and isotopic composition indicate that they are derived from isorenieratene from the Chlorobiaceae family of sulphur bacteria. These results are consistent with geological and geochemical studies that show that the source rocks were deposited under metahaline to hypersaline sulphate and sulphide rich water columns. The distribution of other biomarkers in these oils and source rocks indicates that a diverse biota contributed organic matter to the source environment. In conjunction with the aryl isoprenoids, they show that there is a remarkable similarity in composition between the two sets of oils and source rocks despite their great temporal and geographic separation. This reflects the similarity of their environments and emphasizes the importance of sedimentary facies in controlling the composition of organic matter in source rocks and their derived oils.

  7. Lovastatin insensitive 1, a Novel pentatricopeptide repeat protein, is a potential regulatory factor of isoprenoid biosynthesis in Arabidopsis.

    Science.gov (United States)

    Kobayashi, Keiko; Suzuki, Masashi; Tang, Jianwei; Nagata, Noriko; Ohyama, Kiyoshi; Seki, Hikaru; Kiuchi, Reiko; Kaneko, Yasuko; Nakazawa, Miki; Matsui, Minami; Matsumoto, Shogo; Yoshida, Shigeo; Muranaka, Toshiya

    2007-02-01

    Higher plants have two metabolic pathways for isoprenoid biosynthesis: the cytosolic mevalonate (MVA) pathway and the plastidal non-mevalonate (MEP) pathway. Despite the compartmentalization of these two pathways, metabolic flow occurs between them. However, little is known about the mechanisms that regulate the two pathways and the metabolic cross-talk. To identify such regulatory mechanisms, we isolated and characterized the Arabidopsis T-DNA insertion mutant lovastatin insensitive 1 (loi1), which is resistant to lovastatin and clomazone, inhibitors of the MVA and MEP pathways, respectively. The accumulation of the major products of these pathways, i.e. sterols and chlorophyll, was less affected by lovastatin and clomazone, respectively, in loi1 than in the wild type. Furthermore, the 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) activity analysis showed higher activity of HMGR in loi1-1 treated with lovastatin than that in the WT. We consider that the lovastatin-resistant phenotype of loi1-1 was derived from this post-transcriptional up-regulation of HMGR. The LOI1 gene encodes a novel pentatricopeptide repeat (PPR) protein. PPR proteins are thought to regulate the expression of genes encoded in organelle genomes by post-transcriptional regulation in mitochondria or plastids. Our results demonstrate that LOI1 is predicted to localize in mitochondria and has the ability to bind single-stranded nucleic acids. Our investigation revealed that the post-transcriptional regulation of mitochondrial RNA may be involved in isoprenoid biosynthesis in both the MVA and MEP pathways.

  8. Titanium Dioxide Volatility in High Temperature Water Vapor

    Science.gov (United States)

    Nguyen, QynhGiao N.

    2008-01-01

    Titanium (Ti) containing materials are of high interest to the aerospace industry due to its high temperature capability, strength, and light weight. As with most metals an exterior oxide layer naturally exists in environments that contain oxygen (i.e. air). At high temperatures, water vapor plays a key role in the volatility of materials including oxide surfaces. This study will evaluate cold pressed titanium dioxide (TiO2) powder pellets at a temperature range of 1400 C - 1200 C in water containing environments to determine the volatile hydroxyl species using the transpiration method. The water content ranged from 0-76 mole% and the oxygen content range was 0-100 mole % during the 20-250 hour exposure times. Preliminary results indicate that oxygen is not a key contributor at these temperatures and the following reaction is the primary volatile equation for all three temperatures: TiO2 (s) + H2O (g) = TiO(OH)2 (g).

  9. On guidance and volatility

    NARCIS (Netherlands)

    Billings, M.B.; Jennings, R.; Lev, B.

    2013-01-01

    Survey evidence suggests that managers voluntarily disclose information, particularly earnings guidance, with an aim toward dampening share price volatility. Yet, consultants and influential institutions advise against providing guidance — citing fears of litigation and market penalties associated w

  10. Dynamic Volatility Arbitrage

    DEFF Research Database (Denmark)

    Dorn, Jochen

    profit on well-developed markets. Dynamic participation features on cross asset portfolios are at rst sight a remedy to that dilemma. Based on volatility thresholds and portfolio re-balancing, the fund engineers try to create a "volatility guaranteed" investment opportunity by surfing on the unusual high...... concepts, next to nothing is known about position reverting strategies and how, and -even more important- in which context they are applied in practice. In the recent market downturn only one sector generated signicant profits for the leading investment banks: Volatility trading activities, namely on Forex......, interest rates and commodities. If an investor positions himself on the (volatility) market within a long/short trading framework, he typically bets on a traditional mispricing arbitrage. However as this corresponds to a call spread with equal exercise prices, this strategy alone would not generate enough...

  11. It’s all about volatility of volatility

    DEFF Research Database (Denmark)

    Grassi, Stefano; Santucci de Magistris, Paolo

    2015-01-01

    for the realized volatility series. It emerges that during the recent financial crisis the relative weight of the daily component dominates over the monthly term. The estimates of the two factor stochastic volatility model suggest that the change in the dynamic structure of the realized volatility during...... the financial crisis is due to the increase in the volatility of the persistent volatility term. A set of Monte Carlo simulations highlights the robustness of the methodology adopted in tracking the dynamics of the parameters....

  12. Non-volatile memories

    CERN Document Server

    Lacaze, Pierre-Camille

    2014-01-01

    Written for scientists, researchers, and engineers, Non-volatile Memories describes the recent research and implementations in relation to the design of a new generation of non-volatile electronic memories. The objective is to replace existing memories (DRAM, SRAM, EEPROM, Flash, etc.) with a universal memory model likely to reach better performances than the current types of memory: extremely high commutation speeds, high implantation densities and retention time of information of about ten years.

  13. Volatiles Which Increase Magma Viscosity

    Science.gov (United States)

    Webb, S.

    2015-12-01

    The standard model of an erupting volcano is one in which the viscosity of a decompressing magma increases as the volatiles leave the melt structure to form bubbles. It has now been observed that the addition of the "volatiles" P, Cl and F result in an increase in silicate melt viscosity. This observation would mean that the viscosity of selected degassing magmas would decrease rather than increase. Here we look at P, Cl and F as three volatiles which increase viscosity through different structural mechanisms. In all three cases the volatiles increase the viscosity of peralkaline composition melts, but appear to always decrease the viscosity of peraluminous melts. Phosphorus causes the melt to unmix into a Na-P rich phase and a Na-poor silicate phase. Thus as the network modifying Na (or Ca) are removed to the phosphorus-rich melt, the matrix melt viscosity increases. With increasing amounts of added phosphorus (at network modifying Na ~ P) the addition of further phosphorus causes a decrease in viscosity. The addition of chlorine to Fe-free aluminosilicate melts results in an increase in viscosity. NMR data on these glass indicates that the chlorine sits in salt-like structures surrounded by Na and/or Ca. Such structures would remove network-modifying atoms from the melt structure and thus result in an increase in viscosity. The NMR spectra of fluorine-bearing glasses shows that F takes up at least 5 different structural positions in peralkaline composition melts. Three of these positions should result in a decrease in viscosity due to the removal of bridging oxygens. Two of the structural positons of F, however, should result in an increase in viscosity as they require the removal of network-modifying atoms from the melt structure (with one of the structures being that observed for Cl). This would imply that increasing amounts of F might result in an increase in viscosity. This proposed increase in viscosity with increasing F has now been experimentally confirmed.

  14. Oil and stock market volatility: A multivariate stochastic volatility perspective

    Energy Technology Data Exchange (ETDEWEB)

    Vo, Minh, E-mail: minh.vo@metrostate.edu

    2011-09-15

    This paper models the volatility of stock and oil futures markets using the multivariate stochastic volatility structure in an attempt to extract information intertwined in both markets for risk prediction. It offers four major findings. First, the stock and oil futures prices are inter-related. Their correlation follows a time-varying dynamic process and tends to increase when the markets are more volatile. Second, conditioned on the past information, the volatility in each market is very persistent, i.e., it varies in a predictable manner. Third, there is inter-market dependence in volatility. Innovations that hit either market can affect the volatility in the other market. In other words, conditioned on the persistence and the past volatility in their respective markets, the past volatility of the stock (oil futures) market also has predictive power over the future volatility of the oil futures (stock) market. Finally, the model produces more accurate Value-at-Risk estimates than other benchmarks commonly used in the financial industry. - Research Highlights: > This paper models the volatility of stock and oil futures markets using the multivariate stochastic volatility model. > The correlation between the two markets follows a time-varying dynamic process which tends to increase when the markets are more volatile. > The volatility in each market is very persistent. > Innovations that hit either market can affect the volatility in the other market. > The model produces more accurate Value-at-Risk estimates than other benchmarks commonly used in the financial industry.

  15. Recognition of n-alkyl and isoprenoid biopolymers in marine sediments by stable carbon isotopic analysis of pyrolysis products of kerogens

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Hold, I.M.; Schouten, S.; Kaam-Peters, H.M.E. van

    1998-01-01

    Analysis of the pyrolysis products of several marine kerogens revealed that the stable carbon isotopic composition of the n-alkanes (C10-C25) are quite similar to those of the n-alkenes. This suggests that they have a common origin such as algal biopolymers. The isoprenoid alkanes (C13-C20) also hav

  16. Increased Expression of RhoA in Epithelium and Smooth Muscle of Obese Mouse Models: Implications for Isoprenoid Control of Airway Smooth Muscle and Fibroblasts

    Directory of Open Access Journals (Sweden)

    Kristie R. Ross

    2013-01-01

    Full Text Available The simultaneous rise in the prevalence of asthma and obesity has prompted epidemiologic studies that establish obesity as a risk factor for asthma. The alterations in cell signaling that explain this link are not well understood and warrant investigation so that therapies that target this asthma phenotype can be developed. We identified a significant increase in expression of the small GTPase RhoA in nasal epithelial cells and tracheal smooth muscle cells from leptin-deficient (ob/ob mice compared to their wild-type counterparts. Since RhoA function is dependent on isoprenoid modification, we sought to determine the role of isoprenoid-mediated signaling in regulating the viability and proliferation of human airway smooth muscle cells (ASM and normal human lung fibroblasts (NHLF. Inhibiting isoprenoid signaling with mevastatin significantly decreased the viability of ASM and NHLF. This inhibition was reversed by geranylgeranyl pyrophosphate (GGPP, but not farnesyl pyrophosphate (FPP, suggesting specificity to the Rho GTPases. Conversely, increasing isoprenoid synthesis significantly increased ASM proliferation and RhoA protein expression. RhoA expression is inherently increased in airway tissue from ob/ob mice, and obesity-entrained alterations in this pathway may make it a novel therapeutic target for treating airway disease in the obese population.

  17. Effect of temperature and CO2-enrichment on photosynthesis and the levels of carbohydrates and isoprenoid pathway products in guayule, a latex producing shrub

    Science.gov (United States)

    The stems and roots of the desert shrub guayule, Parthenium argentatum, contain a significant amount of latex, a potential source of natural rubber. To determine the factors regulating carbon partitioning, net photosynthesis (Pn) and the levels of carbohydrates and isoprenoid compounds were measured...

  18. Origin and diagenetic transformations of C25 and C30 highly branched isoprenoid sulphur compounds : further evidence for the formation of organic sulphur compounds during early diagenesis

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Kohnen, M.E.L.; Rullkotter, J.; Haven, H.L. ten

    1990-01-01

    A number of C₂₅ and C₃₀ highly branched isoprenoid (HBI) sulphur compounds (e. g. , thiolanes, l-oxo-thiolanes, thiophenes, and benzo[b]thiophenes) with 2, 6, 10, 14-tetramethyl-7-(3-methylpentyl) pentadecane and 2, 6, 10, 14, 18-pentamethyl-7-(3-methylpentyl)nonadecane carbon skeletons were identif

  19. A C-25 highly branched isoprenoid alkene and C-25 and C-27 n-polyenes in the marine diatom Rhizosolenia setigera

    NARCIS (Netherlands)

    Sinninghe Damste, J.S; Rijpstra, W.I C; Schouten, S; Peletier, H.; van der Maarel, M.J.E.C.; Gieskes, W.W C

    1999-01-01

    A North Atlantic strain of the marine diatom Rhizosolenia setigera was examined for the presence of hydrocarbons. This strain biosynthesizes a highly branched isoprenoid (HBI) C-25 pentaene, in contrast to Australian strains of R. setigera which produce HBI C-30 alkenes. The more widespread occurren

  20. A C25 highly branched isoprenoid alkene and C25 and C27 n-polyenes in the marine diatom Rhizosolenia setigera

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Rijpstra, W.I.C.; Schouten, S.; Peletier, H.; Maarel, M.J.E. van der; Gieskes, W.W.C.

    1999-01-01

    A North Atlantic strain of the marine diatom Rhizosolenia setigera was examined for the presence of hydrocarbons. This strain biosynthesizes a highly branched isoprenoid (HBI) C25 pentaene, in contrast to Australian strains of R. setigera which produce HBI C30 alkenes. The more widespread occurrence

  1. Fe-FeO and Fe-Fe3C melting relations at Earth's core-mantle boundary conditions: Implications for a volatile-rich or oxygen-rich core

    Science.gov (United States)

    Morard, G.; Andrault, D.; Antonangeli, D.; Nakajima, Y.; Auzende, A. L.; Boulard, E.; Cervera, S.; Clark, A.; Lord, O. T.; Siebert, J.; Svitlyk, V.; Garbarino, G.; Mezouar, M.

    2017-09-01

    Eutectic melting temperatures in the Fe-FeO and Fe-Fe3C systems have been determined up to 150 GPa. Melting criteria include observation of a diffuse scattering signal by in situ X-Ray diffraction, and textural characterisation of recovered samples. In addition, compositions of eutectic liquids have been established by combining in situ Rietveld analyses with ex situ chemical analyses. Gathering these new results together with previous reports on Fe-S and Fe-Si systems allow us to discuss the specific effect of each light element (Si, S, O, C) on the melting properties of the outer core. Crystallization temperatures of Si-rich core compositional models are too high to be compatible with the absence of extensive mantle melting at the core-mantle boundary (CMB) and significant amounts of volatile elements such as S and/or C (>5 at%, corresponding to >2 wt%), or a large amount of O (>15 at% corresponding to ∼5 wt%) are required to reduce the crystallisation temperature of the core material below that of a peridotitic lower mantle.

  2. SESQUITERPENE RICH VOLATILE SEED OIL OF TAGETES PATULA L. FROM NORTHWEST IRAN

    OpenAIRE

    M. B. Hassanpouraghdam; F Shekari; J. EMARAT-PARDAZ; SAFI SHALAMZARI, M.

    2011-01-01

    Hydrodistilled volatile seed oil composition of commonly growing ornamental Tagetes patula L. was analyzed for its constituents by GC/MS. Forty constituents were identified, comprising 94% of the total oil. Sesquiterpene hydrocarbons (52.7%) and oxygenated sesquiterpenes (15.8%) were the main subclasses of volatile oil components followed by monoterpene hydrocarbons (12.6%). The principle constituents of the volatile oil were (E)-caryophyllene (44.6%) caryophyllene oxide (14.8%), germacrene D...

  3. Identification and geochemical significance of cyclic di- and trisulphides with linear and acyclic isoprenoid carbon skeletons in immature sediments

    Energy Technology Data Exchange (ETDEWEB)

    Kohnen, M.E.L.; Sinninghe Damste, J.S.; Kock-Van Dalen, A.C.; Schouten, S.; Leeuw, J.W. De. (Delft Univ. of Tech. (Netherlands)); Haven, H.L. Ten (Inst. of Petroleum and Organic Geochemistry, Juelich (Germany))

    1991-12-01

    Homologous series (C{sub 15}-C{sub 24}) of novel 3-n-alkyl-1,2-dithianes and 3-n-alkyl-6-methyl-1,2-dithianes have been identified in immature sediments. The identification of these compounds was based on comparison of mass spectra and chromatographic data with those of synthesized 3-methyl-6-tridecyl-1,2-dithiane. In addition, 4-methyl-3-(3,7,11-trimethyldodecyl)-1,2-dithiane, 4-(4-8,12-trimethyltridecyl)-1,2-dithiane, 5-methyl-4-(3,7,11-trimethyldodecyl)-1,2,3-trithiepane, and a 1,2-dithiane possessing a pentakishomohopane carbon skeleton were tentatively assigned on the basis of mass spectral characteristics, selective chemolysis, and desulfurization. The occurrence of these cyclic di- and trisulfides with linear, acyclic isoprenoid and hopanoid carbon skeletons in thermally immature sediments indicates that inorganic polysulfides are incorporated into functionalized lipids during the early stages of diagenesis.

  4. Identification and geochemical significance of cyclic di-and trisulphides with linear and acyclic isoprenoid carbon skeletons in immature sediments

    Science.gov (United States)

    Kohnen, Math E. L.; Sinninghe Damsté, Jaap S.; ten Haven, H. L.; Van Dalen, A. C. Kock; Schouten, Stefan; De Leeuw, Jan W.

    1991-12-01

    Homologous series (C 15-C 24) of novel 3- n-alkyl-1,2-dithianes and 3- n-alkyl-6-methyl-1,2-di-thianes have been identified in immature sediments. The identification of these compounds was based on comparison of mass spectra and Chromatographie data with those of synthesized 3-methyl-6-tridecyll, 2-dithiane. In addition, 4-methyl-3-(3,7,11-trimethyldodecyl)-1,2-dithiane, 4-(4,8,12-trimethyltridecyl)-1,2-dithiane, 5-methyl-4-(3,7,11-trimethyldodecyl)-1,2,3-trithiepane, and a 1,2-dithiane possessing a pentakishomohopane carbon skeleton were tentatively assigned on the basis of mass spectral characteristics, selective chemolysis, and desulphurisation. The occurrence of these cyclic di-and trisulphides with linear, acyclic isoprenoid and hopanoid carbon skeletons in thermally immature sediments indicates that inorganic polysulphides are incorporated into functionalised lipids during the early stages of diagenesis.

  5. Isoprenoid Biosynthesis. Metabolite Profiling of Peppermint Oil Gland Secretory Cells and Application to Herbicide Target Analysis1

    Science.gov (United States)

    Lange, B. Markus; Ketchum, Raymond E.B.; Croteau, Rodney B.

    2001-01-01

    Two independent pathways operate in plants for the synthesis of isopentenyl diphosphate and dimethylallyl diphosphate, the central intermediates in the biosynthesis of all isoprenoids. The mevalonate pathway is present in the cytosol, whereas the recently discovered mevalonate-independent pathway is localized to plastids. We have used isolated peppermint (Mentha piperita) oil gland secretory cells as an experimental model system to study the effects of the herbicides fosmidomycin, phosphonothrixin, methyl viologen, benzyl viologen, clomazone, 2-(dimethylamino)ethyl diphosphate, alendronate, and pamidronate on the pools of metabolites related to monoterpene biosynthesis via the mevalonate-independent pathway. A newly developed isolation protocol for polar metabolites together with an improved separation and detection method based on liquid chromatography-mass spectrometry have allowed assessment of the enzyme targets for a number of these herbicides. PMID:11553758

  6. The subcellular localization of periwinkle farnesyl diphosphate synthase provides insight into the role of peroxisome in isoprenoid biosynthesis.

    Science.gov (United States)

    Thabet, Insaf; Guirimand, Grégory; Courdavault, Vincent; Papon, Nicolas; Godet, Stéphanie; Dutilleul, Christelle; Bouzid, Sadok; Giglioli-Guivarc'h, Nathalie; Clastre, Marc; Simkin, Andrew J

    2011-11-15

    Farnesyl diphosphate (FPP) synthase (FPS: EC.2.5.1.1, EC.2.5.1.10) catalyzes the formation of FPP from isopentenyl diphosphate and dimethylallyl diphosphate via two successive condensation reactions. A cDNA designated CrFPS, encoding a protein showing high similarities with trans-type short FPS isoforms, was isolated from the Madagascar periwinkle (Catharanthus roseus). This cDNA was shown to functionally complement the lethal FPS deletion mutant in the yeast Saccharomyces cerevisiae. At the subcellular level, while short FPS isoforms are usually described as cytosolic proteins, we showed, using transient transformations of C. roseus cells with yellow fluorescent protein-fused constructs, that CrFPS is targeted to peroxisomes. This finding is discussed in relation to the subcellular distribution of FPS isoforms in plants and animals and opens new perspectives towards the understanding of isoprenoid biosynthesis.

  7. Understanding Interest Rate Volatility

    DEFF Research Database (Denmark)

    Volker, Desi

    This thesis is the result of my Ph.D. studies at the Department of Finance of the Copenhagen Business School. It consists of three essays covering topics related to the term structure of interest rates, monetary policy and interest rate volatility. The rst essay, \\Monetary Policy Uncertainty...... and Interest Rates", examines the role of monetary policy uncertainty on the term structure of interest rates. The second essay, \\A Regime-Switching A ne Term Structure Model with Stochastic Volatility" (co-authored with Sebastian Fux), investigates the ability of the class of regime switching models...... with and without stochastic volatility to capture the main stylized features of U.S. interest rates. The third essay, \\Variance Risk Premia in the Interest Rate Swap Market", investigates the time-series and cross-sectional properties of the compensation demanded for holding interest rate variance risk. The essays...

  8. Stochastic volatility selected readings

    CERN Document Server

    Shephard, Neil

    2005-01-01

    Neil Shephard has brought together a set of classic and central papers that have contributed to our understanding of financial volatility. They cover stocks, bonds and currencies and range from 1973 up to 2001. Shephard, a leading researcher in the field, provides a substantial introduction in which he discusses all major issues involved. General Introduction N. Shephard. Part I: Model Building. 1. A Subordinated Stochastic Process Model with Finite Variance for Speculative Prices, (P. K. Clark). 2. Financial Returns Modelled by the Product of Two Stochastic Processes: A Study of Daily Sugar Prices, 1961-7, S. J. Taylor. 3. The Behavior of Random Variables with Nonstationary Variance and the Distribution of Security Prices, B. Rosenberg. 4. The Pricing of Options on Assets with Stochastic Volatilities, J. Hull and A. White. 5. The Dynamics of Exchange Rate Volatility: A Multivariate Latent Factor ARCH Model, F. X. Diebold and M. Nerlove. 6. Multivariate Stochastic Variance Models. 7. Stochastic Autoregressive...

  9. Pricing Volatility of Stock Returns with Volatile and Persistent Components

    DEFF Research Database (Denmark)

    Zhu, Jie

    2009-01-01

    This paper introduces a two-component volatility model based on first moments of both components to describe the dynamics of speculative return volatility. The two components capture the volatile and the persistent part of volatility, respectively. The model is applied to 10 Asia-Pacific stock...... markets. Their in-mean effects on returns are tested. The empirical results show that the persistent component is much more important for the volatility dynamic process than is the volatile component. However, the volatile component is found to be a significant pricing factor of asset returns for most...... markets. A positive or risk-premium effect exists between the return and the volatile component, yet the persistent component is not significantly priced for the return dynamic process....

  10. Volatile displacement of Meghalaya coals – A pointer to explore low sulphur coals

    Indian Academy of Sciences (India)

    P Behera

    2007-04-01

    Volatile displacement, which measures the difference between calculated and experimental volatile matter, is indicative of abnormality in coals which may be related to petrological or chemical parameters. The volatile displacement () values of Meghalaya coals were calculated from their chemical analyses. Correlations of volatile displacement () with parameters such as carbon, hydrogen, moisture, oxygen, oxygen plus sulphate sulphur, oxygen plus pyritic sulphur, oxygen plus organic sulphur and total sulphur were studied. An approximately linear relationship exists only between and moisture, and and total sulphur, and not between other parameters. Plots on Seyler’s chart indicate the coals as perhydrous to orthohydrous. The linear relationship with total sulphur indicates that the coals may have become abnormal mainly due to the marine environment of deposition and weathering.

  11. Pricing Volatility of Stock Returns with Volatile and Persistent Components

    DEFF Research Database (Denmark)

    Zhu, Jie

    In this paper a two-component volatility model based on the component's first moment is introduced to describe the dynamic of speculative return volatility. The two components capture the volatile and persistent part of volatility respectively. Then the model is applied to 10 Asia-Pacific stock m......, a positive or risk-premium effect exists between return and the volatile component, yet the persistent component is not significantly priced for return dynamic process.......In this paper a two-component volatility model based on the component's first moment is introduced to describe the dynamic of speculative return volatility. The two components capture the volatile and persistent part of volatility respectively. Then the model is applied to 10 Asia-Pacific stock...... markets. Their in-mean effects on return are also tested. The empirical results show that the persistent component accounts much more for volatility dynamic process than the volatile component. However the volatile component is found to be a significant pricing factor of asset returns for most markets...

  12. Biomass torrefaction: modeling of volatile and solid product evolution kinetics.

    Science.gov (United States)

    Bates, Richard B; Ghoniem, Ahmed F

    2012-11-01

    The aim of this work is the development of a kinetics model for the evolution of the volatile and solid product composition during torrefaction conditions between 200 and 300°C. Coupled to an existing two step solid mass loss kinetics mechanism, this model describes the volatile release kinetics in terms of a set of identifiable chemical components, permitting the solid product composition to be estimated by mass conservation. Results show that most of the volatiles released during the first stage include highly oxygenated species such as water, acetic acid, and carbon dioxide, while volatiles released during the second step are composed primarily of lactic acid, methanol, and acetic acid. This kinetics model will be used in the development of a model to describe reaction energy balance and heat release dynamics.

  13. Dynamic Volatility Arbitrage

    DEFF Research Database (Denmark)

    Dorn, Jochen

    concepts, next to nothing is known about position reverting strategies and how, and -even more important- in which context they are applied in practice. In the recent market downturn only one sector generated signicant profits for the leading investment banks: Volatility trading activities, namely on Forex...

  14. Stock markets liberalization affects volatility?

    OpenAIRE

    Ioan Alin NISTOR; Maria-Lenuţa CIUPAC-ULICI; GHERMAN Mircea-Cristian

    2012-01-01

    Regarding the impact of liberalization, the results show that, in general, market opening is accompanied by a significant increase in market volatility. In particular, volatility tends to decrease due to large capital inflows and domestic growth.The study analyzes the impact of stock market liberalization on volatility in six emerging stock markets by using GARCH methodology. Theory on the effects of financial liberalization on volatility has been ambiguous, and empirical work has yielded con...

  15. The exploitation of volatile oil

    Institute of Scientific and Technical Information of China (English)

    MENG Teng; ZHANG Da; TENG Xiangjin; LINing; HAO Zaibin

    2007-01-01

    Rose is a kind of favorite ornamental plant. This article briefly introduced the cultivation and the use of rose around the world both in ancient time and nowadays. Today, volatile oil becomes the mainstream of the rose industry. People pay attention to the effect of volatile oil; meanwhile, they speed up their research on extracting volatile oil and the ingredients.

  16. Plant volatiles and the environment

    NARCIS (Netherlands)

    Loreto, F.; Dicke, M.; Schnitzler, J.P.; Turlings, T.C.J.

    2014-01-01

    Volatile organic compounds emitted by plants represent the largest part of biogenic volatile organic compounds (BVOCs) released into our atmosphere. Plant volatiles are formed through many biochemical pathways, constitutively and after stress induction. In recent years, our understanding of the func

  17. Latent Integrated Stochastic Volatility, Realized Volatility, and Implied Volatility: A State Space Approach

    DEFF Research Database (Denmark)

    Bach, Christian; Christensen, Bent Jesper

    We include simultaneously both realized volatility measures based on high-frequency asset returns and implied volatilities backed out of individual traded at the money option prices in a state space approach to the analysis of true underlying volatility. We model integrated volatility as a latent...... fi…rst order Markov process and show that our model is closely related to the CEV and Barndorff-Nielsen & Shephard (2001) models for local volatility. We show that if measurement noise in the observable volatility proxies is not accounted for, then the estimated autoregressive parameter in the latent...... process is downward biased. Implied volatility performs better than any of the alternative realized measures when forecasting future integrated volatility. The results are largely similar across the stock market (S&P 500), bond market (30-year U.S. T-bond), and foreign currency exchange market ($/£ )....

  18. Stability and `volatility ` of element 104 oxychloride

    Energy Technology Data Exchange (ETDEWEB)

    Eichler, B.; Gaeggeler, H.W. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-09-01

    The formation enthalpies {Delta}H{sup *} of solid and gaseous oxychlorides of element 104 from free atoms were estimated by extrapolation. Stability and volatility of these compounds are compared to those of the homologous and neighbouring elements in the periodic system. It can be supposed that in a gas adsorption chromatographic process with oxygen containing chlorinating carrier gas the transport with the carrier gas flow occurs in the chemical state 104Cl{sub 4}. Only in the absorbed state the compound 104OCl{sub 2} is formed. (author) 1 fig., 3 refs.

  19. Using oxygen at home

    Science.gov (United States)

    Oxygen - home use; COPD - home oxygen; Chronic obstructive airways disease - home oxygen; Chronic obstructive lung disease - home oxygen; Chronic bronchitis - home oxygen; Emphysema - home oxygen; Chronic respiratory ...

  20. Scaling Foreign Exchange Volatility

    OpenAIRE

    Jonathan Batten; Craig Ellis

    2001-01-01

    When asset returns are normally distributed the risk of an asset over a long return interval may be estimated by scaling the risk from shorter return intervals. While it is well known that asset returns are not normally distributed a key empirical question concerns the effect that scaling the volatility of dependent processes will have on the pricing of related financial assets. This study provides an insight into this issue by investigating the return properties of the most important currenc...

  1. A Computer Model for Analyzing Volatile Removal Assembly

    Science.gov (United States)

    Guo, Boyun

    2010-01-01

    A computer model simulates reactional gas/liquid two-phase flow processes in porous media. A typical process is the oxygen/wastewater flow in the Volatile Removal Assembly (VRA) in the Closed Environment Life Support System (CELSS) installed in the International Space Station (ISS). The volatile organics in the wastewater are combusted by oxygen gas to form clean water and carbon dioxide, which is solved in the water phase. The model predicts the oxygen gas concentration profile in the reactor, which is an indicator of reactor performance. In this innovation, a mathematical model is included in the computer model for calculating the mass transfer from the gas phase to the liquid phase. The amount of mass transfer depends on several factors, including gas-phase concentration, distribution, and reaction rate. For a given reactor dimension, these factors depend on pressure and temperature in the reactor and composition and flow rate of the influent.

  2. The role of minerals in the thermal alteration of organic matter. IV - Generation of n-alkanes, acyclic isoprenoids, and alkenes in laboratory experiments

    Science.gov (United States)

    Huizinga, Bradley J.; Tannenbaum, Eli; Kaplan, Isaac R.

    1987-05-01

    The effect of common sedimentary minerals (illite, Na-montmorillonite, or calcite) under different water concentrations on the generation and release of n-alkanes, acyclic isoprenoids, and select alkenes from oil-prone kerogens was investigated. Matrices containing Green River Formation kerogen or Monterey Formation kerogen, alone or in the presence of minerals, were heated at 200 or 300 C for periods of up to 1000 hours, and the pyrolysis products were analyzed. The influence of the first two clay minerals was found to be critically dependent on the water content. Under the dry pyrolysis conditions, both minerals significantly reduced alkene formation; the C12+ n-alkanes and acyclic isoprenoids were mostly destroyed by montmorillonite, but underwent only minor alteration with illite. Under hydrous conditions (mineral/water of 2/1), the effects of both minerals were substantially reduced. Calcite had no significant effect on the thermal evolution of the hydrocarbons.

  3. Volatile Analysis by Pyrolysis of Regolith for Planetary Resource Exploration

    Science.gov (United States)

    Glavin, Daniel P.; Malespin, Charles; ten Kate, Inge L.; Getty, Stephanie A.; Holmes, Vincent E.; Mumm, Erik; Franz, Heather B.; Noreiga, Marvin; Dobson, Nick; Southard, Adrian E.; hide

    2012-01-01

    The extraction and identification of volatile resources that could be utilized by humans including water, oxygen, noble gases, and hydrocarbons on the Moon, Mars, and small planetary bodies will be critical for future long-term human exploration of these objects. Vacuum pyrolysis at elevated temperatures has been shown to be an efficient way to release volatiles trapped inside solid samples. In order to maximize the extraction of volatiles, including oxygen and noble gases from the breakdown of minerals, a pyrolysis temperature of 1400 C or higher is required, which greatly exceeds the maximum temperatures of current state-of-the-art flight pyrolysis instruments. Here we report on the recent optimization and field testing results of a high temperature pyrolysis oven and sample manipulation system coupled to a mass spectrometer instrument called Volatile Analysis by Pyrolysis of Regolith (VAPoR). VAPoR is capable of heating solid samples under vacuum to temperatures above 1300 C and determining the composition of volatiles released as a function of temperature.

  4. The Carotenogenesis Pathway via the Isoprenoid-β-carotene Interference Approach in a New Strain of Dunaliella salina Isolated from Baja California Mexico

    Directory of Open Access Journals (Sweden)

    Luis Enrique Gutierrez-Millan

    2009-02-01

    Full Text Available D. salina is one of the recognized natural sources to produce β-carotene, and an useful model for studying the role of inhibitors and enhancers of carotenogenesis. However there is little information in D. salina regarding whether the isoprenoid substrate can be influenced by stress factors (carotenogenic or selective inhibitors which in turn may further contribute to elucidate the early steps of carotenogenesis and biosynthesis of β-carotene. In this study,Dunaliella salina (BC02 isolated from La Salina BC Mexico, was subjected to the method of isoprenoids-β-carotene interference in order to promote the interruption or accumulation of the programmed biosynthesis of carotenoids. When Carotenogenic and non-carotenogenic cells of D. salina BC02 were grown under photoautotrophicgrowth conditions in the presence of 200 µM fosmidomycin, carotenogenesis and the synthesis of β-carotene were interrupted after two days in cultured D. salina cells. This result is an indirect consequence of the inhibition of the synthesis of isoprenoids and activity of the recombinant DXR enzyme thereby preventing the conversionof 1-deoxy-D-xylulose 5-phosphate (DXP to 2-C-methyl-D-erythritol (MEP and consequently interrupts the early steps of carotenogenesis in D. salina. The effect at the level of proteins and RNA was not evident. Mevinolin treated D. salina cells exhibited carotenogenesis and β-carotene levels very similar to those of control cell cultures indicating that mevinolin not pursued any indirect action in the biosynthesis of isoprenoids and had no effect at the level of the HMG-CoA reductase, the key enzyme of the Ac/MVA pathway.

  5. Changes in photosynthesis, mesophyll conductance to CO{sub 2}, and isoprenoid emissions in Populus nigra plants exposed to excess nickel

    Energy Technology Data Exchange (ETDEWEB)

    Velikova, Violeta, E-mail: violet@obzor.bio21.bas.bg [Bulgarian Academy of Sciences, Acad. M. Popov Institute of Plant Physiology, Acad. G. Bonchev, Bl. 21, 1113 Sofia (Bulgaria); Tsonev, Tsonko [Bulgarian Academy of Sciences, Acad. M. Popov Institute of Plant Physiology, Acad. G. Bonchev, Bl. 21, 1113 Sofia (Bulgaria); Loreto, Francesco [Consiglio Nazionale delle Ricerche, Istituto per la Protezione delle Piante, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze (Italy); Centritto, Mauro [Consiglio Nazionale delle Ricerche, Istituto di Biologia Agroambientale e Forestale, 00015 Monterotondo Scalo (RM) (Italy)

    2011-05-15

    Poplar (Populus nigra) plants were grown hydroponically with 30 and 200 {mu}M Ni (Ni{sub 30} and Ni{sub 200}). Photosynthesis limitations and isoprenoid emissions were investigated in two leaf types (mature and developing). Ni stress significantly decreased photosynthesis, and this effect depended on the leaf Ni content, which was lower in mature than in developing leaves. The main limitations to photosynthesis were attributed to mesophyll conductance and metabolism impairment. In Ni-stressed developing leaves, isoprene emission was significantly stimulated. We attribute such stimulation to the lower chloroplastic [CO{sub 2}] than in control leaves. However chloroplastic [CO{sub 2}] did not control isoprene emission in mature leaves. Ni stress induced the emission of cis-{beta}-ocimene in mature leaves, and of linalool in both leaf types. Induced biosynthesis and emission of isoprenoids reveal the onset of antioxidant processes that may also contribute to reduce Ni stress, especially in mature poplar leaves. - Graphical abstract: Visible damage caused by Ni treatment. 1 - Ni{sub 0} (control plants); 2 - Ni{sub 200}; M = mature and D = developing Populus nigra leaves. Display Omitted Highlights: > We study the effect of Ni pollution on photosynthesis and isoprenoid emissions. > Ni stress significantly decreases photosynthesis. The main limitations are attributed to mesophyll conductance and metabolism impairment. > Constitutive isoprene emission was significantly stimulated in Ni-stressed leaves. Exposure to enhanced Ni concentration induces cis-beta-ocimene and linalool emissions. - The study reveals consequences of Ni stress on plant physiology, namely increasing diffusional limitation to photosynthesis and isoprenoid emissions.

  6. Plastidic isoprenoid biosynthesis in tomato: physiological and molecular analysis in genotypes resistant and sensitive to drought stress.

    Science.gov (United States)

    Loyola, J; Verdugo, I; González, E; Casaretto, J A; Ruiz-Lara, S

    2012-01-01

    Isoprenoid compounds synthesised in the plastids are involved in plant response to water deficit. The functionality of the biosynthetic pathway of these compounds under drought stress has been analysed at the physiological and molecular levels in two related species of tomato (Solanum chilense and Solanum lycopersicum) that differ in their tolerance to abiotic challenge. Expression analysis of the genes encoding enzymes of these pathways (DXS, IPI, GGPPS, PSY1, NCED and HPT1) in plants at different RWC values shows significant differences for only GGPPS and HPT1, with higher expression in the tolerant S. chilense. Chlorophyll, carotenoids, α-tocopherol and ABA content was also determined in both species under different drought conditions. In agreement with HPT1 transcriptional activity, higher α-tocopherol content was observed in S. chilense than in S. lycopersicum, which correlates with a lower degree of lipoperoxidation in the former species. These results suggest that, in addition to lower stomatal conductance, α-tocopherol biosynthesis is part of the adaptation mechanisms of S. chilense to adverse environmental conditions.

  7. Inhibition Studies on Enzymes Involved in Isoprenoid Biosynthesis: Focus on Two Potential Drug Targets: DXR and IDI-2 Enzymes.

    Science.gov (United States)

    de Ruyck, Jérôme; Wouters, Johan; Poulter, C Dale

    2011-07-01

    Isoprenoid compounds constitute an immensely diverse group of acyclic, monocyclic and polycyclic compounds that play important roles in all living organisms. Despite the diversity of their structures, this plethora of natural products arises from only two 5-carbon precursors, isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). This review will discuss the enzymes in the mevalonate (MVA) and methylerythritol phosphate (MEP) biosynthetic pathways leading to IPP and DMAPP with a particular focus on MEP synthase (DXR) and IPP isomerase (IDI), which are potential targets for the development of antibiotic compounds. DXR is the second enzyme in the MEP pathway and the only one for which inhibitors with antimicrobial activity at pharmaceutically relevant concentrations are known. All of the published DXR inhibitors are fosmidomycin analogues, except for a few bisphosphonates with moderate inhibitory activity. These far, there are no other candidates that target DXR. IDI was first identified and characterised over 40 years ago (IDI-1) and a second convergently evolved isoform (IDI-2) was discovered in 2001. IDI-1 is a metalloprotein found in Eukarya and many species of Bacteria. Its mechanism has been extensively studied. In contrast, IDI-2 requires reduced flavin mononucleotide as a cofactor. The mechanism of action for IDI-2 is less well defined. This review will describe how lead inhibitors are being improved by structure-based drug design and enzymatic assays against DXR to lead to new drug families and how mechanistic probes are being used to address questions about the mechanisms of the isomerases.

  8. [Apneic oxygenation].

    Science.gov (United States)

    Alekseev, A V; Vyzhigina, M A; Parshin, V D; Fedorov, D S

    2013-01-01

    Recent technological advances in thoracic and tracheal surgery make the anaesthesiologist use different respiratory techniques during the operation. Apneic oxygenation is a one of alternative techniques. This method is relatively easy in use, does not require special expensive equipment and is the only possible technique in several clinical situations when other respiratory methods are undesirable or cannot be used. However there is no enough information about apneic oxygenation in Russian. This article reviews publications about apneic oxygenation. The review deals with experiments on diffusion respiration in animals, physiological changes during apneic oxygenation in man and defines clinical cases when apneic oxygenation can be used.

  9. Volatile Organic Compounds are Ghosts for Organic Solar Cells

    Directory of Open Access Journals (Sweden)

    Prakash R. Somani

    2014-11-01

    Full Text Available All our efforts to demonstrate a multifunctional device – photovoltaic gas sensor (i.e. solar cell which show photovoltaic action depending on the gas / volatile organic compounds (VOC in the surrounding atmosphere yielded negative results. Photovoltaic performance of the organic solar cells under study degraded – almost permanently by exposing them to volatile organic compounds (VOCs. Although, the proposed multifunctional device could not be demonstrated; Present investigations yielded very important result that organic solar cells have problems not only with oxygen and humidity (known facts but also with many VOCs and hazardous gases – making lamination / encapsulation step mandatory for their practical utilization.

  10. Fluxes of ozone and Biogenic Volatile Organic Compounds in a mixed Mediterranean forest over a transition period between summer and fall

    Science.gov (United States)

    Fares, S.; Schnitzhofer, R.; Hansel, A.; Petersson, F.; Matteucci, G.; Scarascia Mugnozza, G.; Jiang, X.; Guenther, A. B.; Loreto, F.

    2012-12-01

    Mediterranean plant ecosystems are exposed to abiotic stressors that may be exacerbated by climate change dynamics. Moreover, plants need now to cope with increasing anthropogenic pressures, often associated with expanding impacts of urbanization. Anthropogenic stressors include harmful gases (e.g. ozone,) that are transported from anthropogenic pollution sources to the vegetation. They may alter ecophysiology and compromise metabolism of Mediterranean plants. A disproportionate number of Mediterranean ecosystems, many dominated by forest trees, are being transformed into "urban or pre-urban forests". This is in particular the case for Castelporziano Estate, a 6,000 ha Mediterranean forest located just 25 km from Rome downtown at the coast of the Mediterranean Sea. In September 2011 an intensive field campaign was performed in Castelporziano to investigate ozone deposition and biogenic emissions of volatile organic compounds (BVOC) from a mixed Mediterranean forest, mainly composed by Quercus suber, Quercus ilex, Pinus pinea. Measurements were performed at canopy level with fast real-time instruments (a fast ozone analyzer and a Proton Transfer Reaction-Time of Flight Mass Spectrometer) that allowed eddy covariant flux measurements of ozone and BVOC. In the transitional period from a warm and dry summer to a wet and moderately cool fall we typically observed tropospheric ozone volume mixing ratios (VMR) of 60 ppb at around noon, with high deposition fluxes (up to -10 nmol m-2 s-1) into the forest canopy. Canopy models were used to to calculate that up to 90% of ozone uptake can be attributed to non-stomatal sinks, suggesting that chemical reactions between ozone and reactive BVOC may have played an important role. The concentrations of reactive isoprenoids (e.g. sesquiterpenes) were indeed observed to decrease during the central hours of the day, in coincidence with increased ozone concentrations. Concentrations and fluxes of isoprenoid

  11. Volatility of organic aerosol and its components in the megacity of Paris

    Science.gov (United States)

    Paciga, Andrea; Karnezi, Eleni; Kostenidou, Evangelia; Hildebrandt, Lea; Psichoudaki, Magda; Engelhart, Gabriella J.; Lee, Byong-Hyoek; Crippa, Monica; Prévôt, André S. H.; Baltensperger, Urs; Pandis, Spyros N.

    2016-02-01

    Using a mass transfer model and the volatility basis set, we estimate the volatility distribution for the organic aerosol (OA) components during summer and winter in Paris, France as part of the collaborative project MEGAPOLI. The concentrations of the OA components as a function of temperature were measured combining data from a thermodenuder and an aerosol mass spectrometer (AMS) with Positive Matrix Factorization (PMF) analysis. The hydrocarbon-like organic aerosol (HOA) had similar volatility distributions for the summer and winter campaigns with half of the material in the saturation concentration bin of 10 µg m-3 and another 35-40 % consisting of low and extremely low volatility organic compounds (LVOCs with effective saturation concentrations C* of 10-3-0.1 µg m-3 and ELVOCs C* less or equal than 10-4 µg m-3, respectively). The winter cooking OA (COA) was more than an order of magnitude less volatile than the summer COA. The low-volatility oxygenated OA (LV-OOA) factor detected in the summer had the lowest volatility of all the derived factors and consisted almost exclusively of ELVOCs. The volatility for the semi-volatile oxygenated OA (SV-OOA) was significantly higher than that of the LV-OOA, containing both semi-volatile organic components (SVOCs with C* in the 1-100 µg m-3 range) and LVOCs. The oxygenated OA (OOA) factor in winter consisted of SVOCs (45 %), LVOCs (25 %) and ELVOCs (30 %). The volatility of marine OA (MOA) was higher than that of the other factors containing around 60 % SVOCs. The biomass burning OA (BBOA) factor contained components with a wide range of volatilities with significant contributions from both SVOCs (50 %) and LVOCs (30 %). Finally, combining the bulk average O : C ratios and volatility distributions of the various factors, our results are placed into the two-dimensional volatility basis set (2D-VBS) framework. The OA factors cover a broad spectrum of volatilities with no direct link between the average volatility and

  12. Option Pricing using Realized Volatility

    DEFF Research Database (Denmark)

    Stentoft, Lars Peter

    In the present paper we suggest to model Realized Volatility, an estimate of daily volatility based on high frequency data, as an Inverse Gaussian distributed variable with time varying mean, and we examine the joint properties of Realized Volatility and asset returns. We derive the appropriate...... benchmark model estimated on return data alone. Hence the paper provides evidence on the value of using high frequency data for option pricing purposes....

  13. Option Pricing using Realized Volatility

    DEFF Research Database (Denmark)

    Stentoft, Lars Peter

    In the present paper we suggest to model Realized Volatility, an estimate of daily volatility based on high frequency data, as an Inverse Gaussian distributed variable with time varying mean, and we examine the joint properties of Realized Volatility and asset returns. We derive the appropriate d...... benchmark model estimated on return data alone. Hence the paper provides evidence on the value of using high frequency data for option pricing purposes....

  14. Tutorial on Atomic Oxygen Effects and Contamination

    Science.gov (United States)

    Miller, Sharon K.

    2017-01-01

    Atomic oxygen is the most predominant specie in low Earth orbit (LEO) and is contained in the upper atmosphere of many other planetary bodies. Formed by photo-dissociation of molecular oxygen, it is highly reactive and energetic enough to break chemical bonds on the surface of many materials and react with them to form either stable or volatile oxides. The extent of the damage for spacecraft depends a lot on how much atomic oxygen arrives at the surface, the energy of the atoms, and the reactivity of the material that is exposed to it. Oxide formation can result in shrinkage, cracking, or erosion which can also result in changes in optical, thermal, or mechanical properties of the materials exposed. The extent of the reaction can be affected by mechanical loading, temperature, and other environmental components such as ultraviolet radiation or charged particles. Atomic oxygen generally causes a surface reaction, but it can scatter under coatings and into crevices causing oxidation much farther into a spacecraft surface or structure than would be expected. Contamination can also affect system performance. Contamination is generally caused by arrival of volatile species that condense on spacecraft surfaces. The volatiles are typically a result of outgassing of materials that are on the spacecraft. Once the volatiles are condensed on a surface, they can then be fixed on the surface by ultraviolet radiation andor atomic oxygen reaction to form stable surface contaminants that can change optical and thermal properties of materials in power systems, thermal systems, and sensors. This tutorial discusses atomic oxygen erosion and contaminate formation, and the effect they have on typical spacecraft materials. Scattering of atomic oxygen, some effects of combined environments and examples of effects of atomic oxygen and contamination on spacecraft systems and components will also be presented.

  15. Core-Mantle Partitioning of Volatile Siderophile Elements and the Origin of Volatile Elements in the Earth

    Science.gov (United States)

    Nickodem, K.; Righter, K.; Danielson, L.; Pando, K.; Lee, C.

    2012-01-01

    There are currently several hypotheses on the origin of volatile siderophile elements in the Earth. One hypothesis is that they were added during Earth s accretion and core formation and mobilized into the metallic core [1], others claim multiple stage origin [2], while some hypothesize that volatiles were added after the core already formed [3]. Several volatile siderophile elements are depleted in Earth s mantle relative to the chondrites, something which continues to puzzle many scientists. This depletion is likely due to a combination of volatility and core formation. The Earth s core is composed of Fe and some lighter constituents, although the abundances of these lighter elements are unknown [4]. Si is one of these potential light elements [5] although few studies have analyzed the effect of Si on metal-silicate partitioning, in particular the volatile elements. As, In, Ge, and Sb are trace volatile siderophile elements which are depleted in the mantle but have yet to be extensively studied. The metal-silicate partition coefficients of these elements will be measured to determine the effect of Si. Partition coefficients depend on temperature, pressure, oxygen fugacity, and metal and silicate composition and can constrain the concentrations of volatile, siderophile elements found in the mantle. Reported here are the results from 13 experiments examining the partitioning of As, In, Ge, and Sb between metallic and silicate liquid. These experiments will examine the effect of temperature, and metal-composition (i.e., Si content) on these elements in or-der to gain a greater understanding of the core-mantle separation which occurred during the Earth s early stages. The data can then be applied to the origin of volatile elements in the Earth.

  16. Volatile signals during pregnancy.

    Science.gov (United States)

    Vaglio, Stefano

    2010-01-01

    Scents play a key role in mediating reproductive interactions in many vertebrates including mammals. Nowadays, several studies indicate that humans seem to use remarkably olfactory communication and are even able to produce and perceive pheromones. Furthermore, over the past several years, it became increasingly clear that pheromone-like chemical signals probably play a role in offspring identification and mother recognition. Recently developed technical procedures (solid-phase microextraction and dynamic headspace extraction) now allow investigators to characterize volatile compounds with high reliability. We analyzed the volatile compounds in sweat patch samples collected from the para-axillary and nipple-areola regions of women during pregnancy and after childbirth. We hypothesized that, at the time of birth and during the first weeks of life, the distinctive olfactory pattern of the para-axillary area is probably useful to newborn babies for recognizing and distinguishing their own mother, whereas the characteristic pattern of the nipple-areola region is probably useful as a guide to nourishment.

  17. Molecular plant volatile communication.

    Science.gov (United States)

    Holopainen, Jarmo K; Blande, James D

    2012-01-01

    Plants produce a wide array of volatile organic compounds (VOCs) which have multiple functions as internal plant hormones (e.g., ethylene, methyl jasmonate and methyl salicylate), in communication with conspecific and heterospecific plants and in communication with organisms of second (herbivores and pollinators) and third (enemies of herbivores) trophic levels. Species specific VOCs normally repel polyphagous herbivores and those specialised on other plant species, but may attract specialist herbivores and their natural enemies, which use VOCs as host location cues. Attraction of predators and parasitoids by VOCs is considered an evolved indirect defence, whereby plants are able to indirectly reduce biotic stress caused by damaging herbivores. In this chapter we review these interactions where VOCs are known to play a crucial role. We then discuss the importance of volatile communication in self and nonself detection. VOCs are suggested to appear in soil ecosystems where distinction of own roots from neighbours roots is essential to optimise root growth, but limited evidence of above-ground plant self-recognition is available.

  18. Oxygen Therapy

    OpenAIRE

    2000-01-01

    LTOT is prescribed for people with chronic lung disease in whom there is a decrease in the ability of the lungs to supply enough oxygen to the body. The heart is obliged to pump faster to meet the body's oxygen requirements. This may place undue stress on the heart, resulting in palpitations, dizziness and fatigue. A low oxygen level in arterial blood is also harmful to the heart, the brain and the pulmonary blood vessels. Oxygen therapy is used to break this cycle. A person with low blood ox...

  19. Chilling and heating may regulate C6 volatile aroma production by different mechanisms in tomato (Solanum lycopersicum) fruit

    Science.gov (United States)

    Hexanal, Z-3-hexenal, E-2-hexenal, hexanol, and Z-3-hexenol are major tomato (Solanum lycopersicum L.) volatile aromas derived from oxygenation of unsaturated fatty acids. Chilling and heating may suppress production of these C6 volatiles. The objective of this research was to determine the response...

  20. Divergent Isoprenoid Biosynthesis Pathways in Staphylococcus Species Constitute a Drug Target for Treating Infections in Companion Animals

    Science.gov (United States)

    Cain, Christine L.; Morris, Daniel O.; Rankin, Shelley C.

    2016-01-01

    ABSTRACT Staphylococcus species are a leading cause of skin and soft tissue infections in humans and animals, and the antibiotics used to treat these infections are often the same. Methicillin- and multidrug-resistant staphylococcal infections are becoming more common in human and veterinary medicine. From a “One Health” perspective, this overlap in antibiotic use and resistance raises concerns over the potential spread of antibiotic resistance genes. Whole-genome sequencing and comparative genomics analysis revealed that Staphylococcus species use divergent pathways to synthesize isoprenoids. Species frequently associated with skin and soft tissue infections in companion animals, including S. schleiferi and S. pseudintermedius, use the nonmevalonate pathway. In contrast, S. aureus, S. epidermidis, and S. lugdunensis use the mevalonate pathway. The antibiotic fosmidomycin, an inhibitor of the nonmevalonate pathway, was effective in killing canine clinical staphylococcal isolates but had no effect on the growth or survival of S. aureus and S. epidermidis. These data identify an essential metabolic pathway in Staphylococcus that differs among members of this genus and suggest that drugs such as fosmidomycin, which targets enzymes in the nonmevalonate pathway, may be an effective treatment for certain staphylococcal infections. IMPORTANCE Drug-resistant Staphylococcus species are a major concern in human and veterinary medicine. There is a need for new antibiotics that exhibit a selective effect in treating infections in companion and livestock animals and that would not be used to treat human bacterial infections. We have identified fosmidomycin as an antibiotic that selectively targets certain Staphylococcus species that are often encountered in skin infections in cats and dogs. These findings expand our understanding of Staphylococcus evolution and may have direct implications for treating staphylococcal infections in veterinary medicine. PMID:27704053

  1. Fast detection of leaf pigments and isoprenoids for ecophysiological studies, plant phenotyping and validating remote-sensing of vegetation.

    Science.gov (United States)

    Junker, Laura V; Ensminger, Ingo

    2016-12-01

    Rapid developments in remote-sensing of vegetation and high-throughput precision plant phenotyping promise a range of real-life applications using leaf optical properties for non-destructive assessment of plant performance. Use of leaf optical properties for assessing plant performance requires the ability to use photosynthetic pigments as proxies for physiological properties and the ability to detect these pigments fast, reliably and at low cost. We describe a simple and cost-effective protocol for the rapid analysis of chlorophylls, carotenoids and tocopherols using high-performance liquid chromatography (HPLC). Many existing methods are based on the expensive solvent acetonitrile, take a long time or do not include lutein epoxide and α-carotene. We aimed to develop an HPLC method which separates all major chlorophylls and carotenoids as well as lutein epoxide, α-carotene and α-tocopherol. Using a C30 -column and a mobile phase with a gradient of methanol, methyl-tert-butyl-ether (MTBE) and water, our method separates the above pigments and isoprenoids within 28 min. The broad applicability of our method is demonstrated using samples from various plant species and tissue types, e.g. leaves of Arabidopsis and avocado plants, several deciduous and conifer tree species, various crops, stems of parasitic dodder, fruit of tomato, roots of carrots and Chlorella algae. In comparison to previous methods, our method is very affordable, fast and versatile and can be used to analyze all major photosynthetic pigments that contribute to changes in leaf optical properties and which are of interest in most ecophysiological studies.

  2. Bisphosphonate inhibitors reveal a large elasticity of plastidic isoprenoid synthesis pathway in isoprene-emitting hybrid aspen.

    Science.gov (United States)

    Rasulov, Bahtijor; Talts, Eero; Kännaste, Astrid; Niinemets, Ülo

    2015-06-01

    Recently, a feedback inhibition of the chloroplastic 1-deoxy-D-xylulose 5-phosphate (DXP)/2-C-methyl-D-erythritol 4-phosphate (MEP) pathway of isoprenoid synthesis by end products dimethylallyl diphosphate (DMADP) and isopentenyl diphosphate (IDP) was postulated, but the extent to which DMADP and IDP can build up is not known. We used bisphosphonate inhibitors, alendronate and zoledronate, that inhibit the consumption of DMADP and IDP by prenyltransferases to gain insight into the extent of end product accumulation and possible feedback inhibition in isoprene-emitting hybrid aspen (Populus tremula × Populus tremuloides). A kinetic method based on dark release of isoprene emission at the expense of substrate pools accumulated in light was used to estimate the in vivo pool sizes of DMADP and upstream metabolites. Feeding with fosmidomycin, an inhibitor of DXP reductoisomerase, alone or in combination with bisphosphonates was used to inhibit carbon input into DXP/MEP pathway or both input and output. We observed a major increase in pathway intermediates, 3- to 4-fold, upstream of DMADP in bisphosphonate-inhibited leaves, but the DMADP pool was enhanced much less, 1.3- to 1.5-fold. In combined fosmidomycin/bisphosphonate treatment, pathway intermediates accumulated, reflecting cytosolic flux of intermediates that can be important under strong metabolic pull in physiological conditions. The data suggested that metabolites accumulated upstream of DMADP consist of phosphorylated intermediates and IDP. Slow conversion of the huge pools of intermediates to DMADP was limited by reductive energy supply. These data indicate that the DXP/MEP pathway is extremely elastic, and the presence of a significant pool of phosphorylated intermediates provides an important valve for fine tuning the pathway flux.

  3. Metabolic engineering for the high-yield production of isoprenoid-based C₅ alcohols in E. coli.

    Science.gov (United States)

    George, Kevin W; Thompson, Mitchell G; Kang, Aram; Baidoo, Edward; Wang, George; Chan, Leanne Jade G; Adams, Paul D; Petzold, Christopher J; Keasling, Jay D; Lee, Taek Soon

    2015-06-08

    Branched five carbon (C5) alcohols are attractive targets for microbial production due to their desirable fuel properties and importance as platform chemicals. In this study, we engineered a heterologous isoprenoid pathway in E. coli for the high-yield production of 3-methyl-3-buten-1-ol, 3-methyl-2-buten-1-ol, and 3-methyl-1-butanol, three C5 alcohols that serve as potential biofuels. We first constructed a pathway for 3-methyl-3-buten-1-ol, where metabolite profiling identified NudB, a promiscuous phosphatase, as a likely pathway bottleneck. We achieved a 60% increase in the yield of 3-methyl-3-buten-1-ol by engineering the Shine-Dalgarno sequence of nudB, which increased protein levels by 9-fold and reduced isopentenyl diphosphate (IPP) accumulation by 4-fold. To further optimize the pathway, we adjusted mevalonate kinase (MK) expression and investigated MK enzymes from alternative microbes such as Methanosarcina mazei. Next, we expressed a fusion protein of IPP isomerase and the phosphatase (Idi1~NudB) along with a reductase (NemA) to diversify production to 3-methyl-2-buten-1-ol and 3-methyl-1-butanol. Finally, we used an oleyl alcohol overlay to improve alcohol recovery, achieving final titers of 2.23 g/L of 3-methyl-3-buten-1-ol (~70% of pathway-dependent theoretical yield), 150 mg/L of 3-methyl-2-buten-1-ol, and 300 mg/L of 3-methyl-1-butanol.

  4. Consistent ranking of volatility models

    DEFF Research Database (Denmark)

    Hansen, Peter Reinhard; Lunde, Asger

    2006-01-01

    We show that the empirical ranking of volatility models can be inconsistent for the true ranking if the evaluation is based on a proxy for the population measure of volatility. For example, the substitution of a squared return for the conditional variance in the evaluation of ARCH-type models can...

  5. Political institutions and economic volatility

    NARCIS (Netherlands)

    Klomp, Jeroen; de Haan, Jakob

    2009-01-01

    We examine the effect of political 'institutions' on economic growth volatility, using data from more than 100 countries over the period 1960 to 2005, taking into account various control variables as suggested in previous studies. Our indicator of volatility is the relative standard deviation of the

  6. Emerging non-volatile memories

    CERN Document Server

    Hong, Seungbum; Wouters, Dirk

    2014-01-01

    This book is an introduction to the fundamentals of emerging non-volatile memories and provides an overview of future trends in the field. Readers will find coverage of seven important memory technologies, including Ferroelectric Random Access Memory (FeRAM), Ferromagnetic RAM (FMRAM), Multiferroic RAM (MFRAM), Phase-Change Memories (PCM), Oxide-based Resistive RAM (RRAM), Probe Storage, and Polymer Memories. Chapters are structured to reflect diffusions and clashes between different topics. Emerging Non-Volatile Memories is an ideal book for graduate students, faculty, and professionals working in the area of non-volatile memory. This book also: Covers key memory technologies, including Ferroelectric Random Access Memory (FeRAM), Ferromagnetic RAM (FMRAM), and Multiferroic RAM (MFRAM), among others. Provides an overview of non-volatile memory fundamentals. Broadens readers' understanding of future trends in non-volatile memories.

  7. Appreciating Oxygen

    Science.gov (United States)

    Weiss, Hilton M.

    2008-01-01

    Photosynthetic flora and microfauna utilize light from the sun to convert carbon dioxide and water into carbohydrates and oxygen. While these carbohydrates and their derivative hydrocarbons are generally considered to be fuels, it is the thermodynamically energetic oxygen molecule that traps, stores, and provides almost all of the energy that…

  8. Governmentally amplified output volatility

    Science.gov (United States)

    Funashima, Yoshito

    2016-11-01

    Predominant government behavior is decomposed by frequency into several periodic components: updating cycles of infrastructure, Kuznets cycles, fiscal policy over business cycles, and election cycles. Little is known, however, about the theoretical impact of such cyclical behavior in public finance on output fluctuations. Based on a standard neoclassical growth model, this study intends to examine the frequency at which public investment cycles are relevant to output fluctuations. We find an inverted U-shaped relationship between output volatility and length of cycle in public investment. This implies that periodic behavior in public investment at a certain frequency range can cause aggravated output resonance. Moreover, we present an empirical analysis to test the theoretical implication, using the U.S. data in the period from 1968 to 2015. The empirical results suggest that such resonance phenomena change from low to high frequency.

  9. Volatility Exposure for Strategic Asset Allocation

    OpenAIRE

    Briere, Marie; Burgues, Alexandre; Signori, Ombretta

    2010-01-01

    The authors examine the advantages of incorporating strategic exposure to equity volatility into the investment opportunity set of a long-term equity investor. They consider two standard volatility investments: implied volatility and volatility risk premium strategies. An analytical framework, which offers pragmatic solutions for long-term investors who seek exposure to volatility, is used to calibrate and assess the risk-return profiles of portfolios. The benefit of volatility exposure for a...

  10. Reduced Heart Rate Volatility

    Science.gov (United States)

    Grogan, Eric L.; Morris, John A.; Norris, Patrick R.; France, Daniel J.; Ozdas, Asli; Stiles, Renée A.; Harris, Paul A.; Dawant, Benoit M.; Speroff, Theodore

    2004-01-01

    Objective: To determine if using dense data capture to measure heart rate volatility (standard deviation) measured in 5-minute intervals predicts death. Background: Fundamental approaches to assessing vital signs in the critically ill have changed little since the early 1900s. Our prior work in this area has demonstrated the utility of densely sampled data and, in particular, heart rate volatility over the entire patient stay, for predicting death and prolonged ventilation. Methods: Approximately 120 million heart rate data points were prospectively collected and archived from 1316 trauma ICU patients over 30 months. Data were sampled every 1 to 4 seconds, stored in a relational database, linked to outcome data, and de-identified. HR standard deviation was continuously computed over 5-minute intervals (CVRD, cardiac volatility–related dysfunction). Logistic regression models incorporating age and injury severity score were developed on a test set of patients (N = 923), and prospectively analyzed in a distinct validation set (N = 393) for the first 24 hours of ICU data. Results: Distribution of CVRD varied by survival in the test set. Prospective evaluation of the model in the validation set gave an area in the receiver operating curve of 0.81 with a sensitivity and specificity of 70.1 and 80.0, respectively. CVRD predict death as early as 24 hours in the validation set. Conclusions: CVRD identifies a subgroup of patients with a high probability of dying. Death is predicted within first 24 hours of stay. We hypothesize CVRD is a surrogate for autonomic nervous system dysfunction. PMID:15319726

  11. The Volatile Composition of Portuguese Propolis Towards its Origin Discrimination

    Directory of Open Access Journals (Sweden)

    Soraia I. Falcão

    2016-03-01

    Full Text Available The volatiles from thirty six propolis samples collected from six different geographical locations in Portugal (mainland, Azores archipelago and Madeira Island were evaluated. Populus x canadensis Moenchen leaf-buds and Cistus ladanifer L. branches essential oils were comparatively analysed. The essential oils were isolated by hydrodistillation and analysed by Gas Chromatography (GC and Gas Chromatography-Mass Spectrometry (GC-MS. Cluster analysis based on propolis samples volatiles chemical composition defined three main clusters, not related to sample site collection. Cluster I grouped 28 samples with high relative amounts of oxygen-containing sesquiterpenes (20-77%, while cluster II grouped 7 samples rich in oxygen-containing monoterpenes (9-65% and the only sample from cluster III was monoterpene hydrocarbons rich (26%. Although Populus x canadensis and Cistus ladanifer were associated as resin sources of Portuguese propolis, other Populus species as well as plants like Juniperus genus may contribute to the resin in specific geographical locations.

  12. Quantitative estimates of the volatility of ambient organic aerosol

    Directory of Open Access Journals (Sweden)

    C. D. Cappa

    2010-01-01

    results also show that the amount of semivolatile gas-phase organics in equilibrium with the OA could range from ~20% to 400% of the OA mass, with smaller values generally corresponding to the higher ΔHvap assumptions. The volatility of various OA components determined from factor analysis of AMS spectra has also been assessed. In general, it is found that the fraction of non-volatile material follows the pattern: biomass burning OA < hydrocarbon-like OA < semivolatile oxygenated OA < low-volatility oxygenated OA. Correspondingly, the sensitivity to dilution and the estimated amount of semivolatile gas-phase material for the OA factors follows the reverse order. Primary OA has a substantial semivolatile fraction, in agreement with previous results, while the non-volatile fraction appears to be dominated by oxygenated OA produced by atmospheric aging. The overall OA volatility is thus controlled by the relative contribution of each aerosol type to the total OA burden. Finally, the model/measurement comparison appears to require OA having an evaporation coefficient (γe substantially greater than 10−2; at this point it is not possible to place firmer constraints on γe based on the observations.

  13. Isolation and structure determination of a benzofuran and a bis-nor-isoprenoid from Aspergillus niger grown on the water soluble fraction of Morinda citrifolia Linn. leaves.

    Science.gov (United States)

    Siddiqui, Bina S; Ismail, Fouzia A Sattar; Gulzar, Tahsin; Begum, Sabira

    2003-10-01

    The leaves of Morinda citrifolia, Linn. afforded a new benzofuran and a bis-nor-isoprenoid, blumenol C, hitherto unreported from this source. The structures of these have been elucidated as 5-benzofuran carboxylic acid-6-formyl methyl ester (1) and 4-(3'(R)-hydroxybutyl)-3,5,5, trimethyl-cyclohex-2-en-1-one (2) respectively through spectroscopic studies. The NMR data (including 1D, 2D techniques) and stereochemistry at C-3' of Compound 2 is also being reported for the first time.

  14. Oxygen Therapy

    Science.gov (United States)

    ... oxygen at very high altitudes (like in the mountains or in an airplane) even if you do ... Med Vol 171. P1-P2, 2005 ATS Patient Education Series © 2016 American Thoracic Society www. thoracic. org ...

  15. Dissolved oxygen

    National Research Council Canada - National Science Library

    1981-01-01

    Dissolved oxygen concentrations in the waters of Botany Bay and Georges and Cooks Rivers vary mainly as a result of tidal water movements, algal and macrophytic growth and decay, and effects of storms...

  16. Chemically-resolved volatility measurements of organic aerosol fom different sources.

    Science.gov (United States)

    Huffman, J A; Docherty, K S; Mohr, C; Cubison, M J; Ulbrich, I M; Ziemann, P J; Onasch, T B; Jimenez, J L

    2009-07-15

    A newly modified fast temperature-stepping thermodenuder (TD) was coupled to a High Resolution Time-of-Flight Aerosol Mass Spectrometer for rapid determination of chemically resolved volatility of organic aerosols (OA) emitted from individual sources. The TD-AMS system was used to characterize primary OA (POA) from biomass burning, trash burning surrogates (paper and plastic), and meat cooking as well as chamber-generated secondary OA (SOA) from alpha-pinene and gasoline vapor. Almost all atmospheric models represent POA as nonvolatile, with no allowance for evaporation upon heating or dilution, or condensation upon cooling. Our results indicate that all OAs observed show semivolatile behavior and that most POAs characterized here were at least as volatile as SOA measured in urban environments. Biomass-burning OA (BBOA) exhibited a wide range of volatilities, but more often showed volatility similar to urban OA. Paper-burning resembles some types of BBOA because of its relatively high volatility and intermediate atomic oxygen-to-carbon (O/C) ratio, while meat-cooking OAs (MCOA) have consistently lower volatility than ambient OA. Chamber-generated SOA under the relatively high concentrations used intraditional experiments was significantly more volatile than urban SOA, challenging extrapolation of traditional laboratory volatility measurements to the atmosphere. Most OAs sampled show increasing O/C ratio and decreasing H/C (hydrogen-to-carbon) ratio with temperature, further indicating that more oxygenated OA components are typically less volatile. Future experiments should systematically explore a wider range of mass concentrations to more fully characterize the volatility distributions of these OAs.

  17. Stochastic volatility and stochastic leverage

    DEFF Research Database (Denmark)

    Veraart, Almut; Veraart, Luitgard A. M.

    This paper proposes the new concept of stochastic leverage in stochastic volatility models. Stochastic leverage refers to a stochastic process which replaces the classical constant correlation parameter between the asset return and the stochastic volatility process. We provide a systematic...... treatment of stochastic leverage and propose to model the stochastic leverage effect explicitly, e.g. by means of a linear transformation of a Jacobi process. Such models are both analytically tractable and allow for a direct economic interpretation. In particular, we propose two new stochastic volatility...... models which allow for a stochastic leverage effect: the generalised Heston model and the generalised Barndorff-Nielsen & Shephard model. We investigate the impact of a stochastic leverage effect in the risk neutral world by focusing on implied volatilities generated by option prices derived from our new...

  18. On forecasting Exchange Rate Volatility.

    OpenAIRE

    Hafner, Christian

    2003-01-01

    In an efficient market, foreign exchange rates have to guarantee absence of triangular arbitrage. This note shows that the no-arbitrage condition can be exploited for forecasting the volatility of a single rate by using the information contained in the other rates. Linearly transforming the volatility forecasts of a bivariate model is shown to be more efficient than using a univariate model for the cross-rate.

  19. Development and validation of a rapid resolution liquid chromatography method for the screening of dietary plant isoprenoids: carotenoids, tocopherols and chlorophylls.

    Science.gov (United States)

    Stinco, Carla M; Benítez-González, Ana M; Hernanz, Dolores; Vicario, Isabel M; Meléndez-Martínez, Antonio J

    2014-11-28

    A rapid resolution liquid chromatography (RRLC) method was developed and validated for the simultaneous determination of nine carotenoids compounds (violaxanthin, lutein, zeaxanthin, β-cryptoxanthin, α-carotene, β-carotene, lycopene, phytoene, phytofluene), four tocopherols and four chlorophylls and derivates (chlorophylls and pheophytins). The methodology consisted in a micro-extraction procedure with or without saponification and subsequent analysis by RRLC. The limits of detection were chlorophylls and derivatives. The overall precision values (intra- and inter-day) were lower than 12% when samples were not saponified and <27.6%, when the saponification step was performed. The recovery of the method without the saponification step ranged from 92% to 107%, whilst that when saponification was carried out ranged from 60% for α-tocopherol to 82% for β-carotene. Finally, the applicability of the method was demonstrated by the identification and quantification of isoprenoids in different samples. The methodology is appropriate for the high-throughput screening of dietary isoprenoids in fruits and vegetables.

  20. Recent Advances in Volatiles of Teas

    Directory of Open Access Journals (Sweden)

    Xin-Qiang Zheng

    2016-03-01

    Full Text Available Volatile compounds are important components of tea aroma, a key attribute of sensory quality. The present review examines the formation of aromatic volatiles of various kinds of teas and factors influencing the formation of tea volatiles, including tea cultivar, growing environment and agronomic practices, processing method and storage of tea. The determination of tea volatiles and the relationship of active-aroma volatiles with the sensory qualities of tea are also discussed in the present paper.

  1. Volatilization of heavy metals during incineration of municipal solid wastes

    Institute of Scientific and Technical Information of China (English)

    SUN Lu-shi; S. Abanades; J.D.Lu; G.Flamant; D.Gauthier

    2004-01-01

    Incineration experiments with MSW, which had been impregnated with heavy metals, were presented toobtain information on the volatilization behavior of the elements cadmium (Cd), lead (Pb), and zinc (Zn) underdifferent conditions. Experiments were carried out in a bubbling fluid bed system connected to a customizedinductively coupled plasma optical emission spectroscopy(ICP-OES) for analyzing metals in the flue gas. The resultsindicated that the combustion temperature, the gas atmosphere, and the chlorine content in the flue gas could affectthe volatilization behavior of heavy metals. In the fluidized bed combustion, a large surface area was provided by thebed sand particles, and they may act as absorbents for the gaseous ash-forming compound. Comparer with themetals Cd and Pb, the vaporization of Zn was Iow. The formation of stable compounds such as ZnO·Al2O3 couldgreatly decrease the metals volatilization. The presence of chlorine would enhance the volatilization of heavy metalsby increasing the formation of metal chlorides. However, when the oxygen content was high, the chlorinatingreaction was kinetically hindered, which heavy metals release would be delayed.

  2. Lunar Advanced Volatile Analysis Subsystem: Pressure Transducer Trade Study

    Science.gov (United States)

    Kang, Edward Shinuk

    2017-01-01

    In Situ Resource Utilization (ISRU) is a key factor in paving the way for the future of human space exploration. The ability to harvest resources on foreign astronomical objects to produce consumables and propellant offers potential reduction in mission cost and risk. Through previous missions, the existence of water ice at the poles of the moon has been identified, however the feasibility of water extraction for resources remains unanswered. The Resource Prospector (RP) mission is currently in development to provide ground truth, and will enable us to characterize the distribution of water at one of the lunar poles. Regolith & Environment Science and Oxygen & Lunar Volatile Extraction (RESOLVE) is the primary payload on RP that will be used in conjunction with a rover. RESOLVE contains multiple instruments for systematically identifying the presence of water. The main process involves the use of two systems within RESOLVE: the Oxygen Volatile Extraction Node (OVEN) and Lunar Advanced Volatile Analysis (LAVA). Within the LAVA subsystem, there are multiple calculations that depend on accurate pressure readings. One of the most important instances where pressure transducers (PT) are used is for calculating the number of moles in a gas transfer from the OVEN subsystem. As a critical component of the main process, a mixture of custom and commercial off the shelf (COTS) PTs are currently being tested in the expected operating environment to eventually down select an option for integrated testing in the LAVA engineering test unit (ETU).

  3. RICE PRICE VOLATILITY IN EAST JAVA

    Directory of Open Access Journals (Sweden)

    Wati R.Y.E.

    2017-09-01

    Full Text Available The purpose of the research is analyzing the volatility and volatility spillover of monthly price of paddy at the level of farmers and consumers in 2010-2016. ARCH/GARCH used to analyze volatility and GARCH BEKK-model is used to analyze the volatility spillover. The results of the analysis show that price volatility at the farmer level is very high (extremely high volatility, price volatility at the consumer level is low (low volatility, and volatility spillover does not occur between the farmers and the consumers market. The need to guarantee an effective floor price as well as information disclosure related to the market commodity prices so that the pattern of prices transmission among interrelated markets can be symmetrical.

  4. The price of fixed income market volatility

    CERN Document Server

    Mele, Antonio

    2015-01-01

    Fixed income volatility and equity volatility evolve heterogeneously over time, co-moving disproportionately during periods of global imbalances and each reacting to events of different nature. While the methodology for options-based "model-free" pricing of equity volatility has been known for some time, little is known about analogous methodologies for pricing various fixed income volatilities. This book fills this gap and provides a unified evaluation framework of fixed income volatility while dealing with disparate markets such as interest-rate swaps, government bonds, time-deposits and credit. It develops model-free, forward looking indexes of fixed-income volatility that match different quoting conventions across various markets, and uncovers subtle yet important pitfalls arising from naïve superimpositions of the standard equity volatility methodology when pricing various fixed income volatilities. The ultimate goal of the authors´ efforts is to make interest rate volatility standardization a valuable...

  5. Observability of market daily volatility

    Science.gov (United States)

    Petroni, Filippo; Serva, Maurizio

    2016-02-01

    We study the price dynamics of 65 stocks from the Dow Jones Composite Average from 1973 to 2014. We show that it is possible to define a Daily Market Volatility σ(t) which is directly observable from data. This quantity is usually indirectly defined by r(t) = σ(t) ω(t) where the r(t) are the daily returns of the market index and the ω(t) are i.i.d. random variables with vanishing average and unitary variance. The relation r(t) = σ(t) ω(t) alone is unable to give an operative definition of the index volatility, which remains unobservable. On the contrary, we show that using the whole information available in the market, the index volatility can be operatively defined and detected.

  6. Consistent ranking of volatility models

    DEFF Research Database (Denmark)

    Hansen, Peter Reinhard; Lunde, Asger

    2006-01-01

    result in an inferior model being chosen as "best" with a probability that converges to one as the sample size increases. We document the practical relevance of this problem in an empirical application and by simulation experiments. Our results provide an additional argument for using the realized...... variance in out-of-sample evaluations rather than the squared return. We derive the theoretical results in a general framework that is not specific to the comparison of volatility models. Similar problems can arise in comparisons of forecasting models whenever the predicted variable is a latent variable.......We show that the empirical ranking of volatility models can be inconsistent for the true ranking if the evaluation is based on a proxy for the population measure of volatility. For example, the substitution of a squared return for the conditional variance in the evaluation of ARCH-type models can...

  7. Oil Volatility Risk and Expected Stock Returns

    DEFF Research Database (Denmark)

    Christoffersen, Peter; Pan, Xuhui (Nick)

    After the financialization of commodity futures markets in 2004-05 oil volatility has become a strong predictor of returns and volatility of the overall stock market. Furthermore, stocks' exposure to oil volatility risk now drives the cross-section of expected returns. The difference in average...... return between the quintile of stocks with low exposure and high exposure to oil volatility is significant at 0.66% per month, and oil volatility risk carries a significant risk premium of -0.60% per month. In the post-financialization period, oil volatility risk is strongly related with various measures...

  8. Rhenium volatilization in waste glasses

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Kai; Pierce, David A. [Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Hrma, Pavel, E-mail: pavel.hrma@pnnl.gov [Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Schweiger, Michael J. [Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Kruger, Albert A. [U.S. Department of Energy, Office of River Protection, Richland, WA 99352 (United States)

    2015-09-15

    Highlights: • Re did not volatilize from a HLW feed until 1000 °C. • Re began to volatilize from LAW feeds at ∼600 °C. • The vigorous foaming and generation of gases from salts enhanced Re evaporation in LAW feeds. • The HLW glass with less foaming and salts is a promising medium for Tc immobilization. - Abstract: We investigated volatilization of rhenium (Re), sulfur, cesium, and iodine during the course of conversion of high-level waste melter feed to glass and compared the results for Re volatilization with those in low-activity waste borosilicate glasses. Whereas Re did not volatilize from high-level waste feed heated at 5 K min{sup −1} until 1000 °C, it began to volatilize from low-activity waste borosilicate glass feeds at ∼600 °C, a temperature ∼200 °C below the onset temperature of evaporation from pure KReO{sub 4}. Below 800 °C, perrhenate evaporation in low-activity waste melter feeds was enhanced by vigorous foaming and generation of gases from molten salts as they reacted with the glass-forming constituents. At high temperatures, when the glass-forming phase was consolidated, perrhenates were transported to the top surface of glass melt in bubbles, typically together with sulfates and halides. Based on the results of this study (to be considered preliminary at this stage), the high-level waste glass with less foaming and salts appears a promising medium for technetium immobilization.

  9. Characterization of the Migration of Hop Volatiles into Different Crown Cork Liner Polymers and Can Coatings.

    Science.gov (United States)

    Wietstock, Philip C; Glattfelder, Richard; Garbe, Leif-Alexander; Methner, Frank-Jürgen

    2016-04-01

    Absorption of hop volatiles by crown cork liner polymers and can coatings was investigated in beer during storage. All hop volatiles measured were prone to migrate into the closures, and the absorption kinetics was demonstrated to fit Fick's second law of diffusion well for a plane sheet. The extent and rate of diffusion were significantly dissimilar and were greatly dependent upon the nature of the volatile. Diffusion coefficients ranged from 1.32 × 10(-5) cm(2)/day (limonene) to 0.26 × 10(-5) cm(2)/day (α-humulene). The maximum amounts absorbed into the material at equilibrium were in the following order: limonene > α-humulene > trans-caryophyllene > myrcene ≫ linalool > α-terpineol > geraniol. With the application of low-density polyethylene (LDPE) liners with oxygen-scavenging functionality, oxygen-barrier liners made up from high-density polyethylene (HDPE) or liner polymers from a different manufacturer had no significant effect on the composition of hop volatiles in beers after prolonged storage of 55 days; however, significantly higher amounts of myrcene and limonene were found in the oxygen-barrier-type crown cork, while all other closures behaved similarly. Can coatings were demonstrated to absorb hop volatiles in a similar pattern as crown corks but to a lesser extent. Consequently, significantly higher percentages of myrcene were found in the beers.

  10. Root anoxia effects on physiology and emissions of volatile organic compounds (VOC) under short- and long-term inundation of trees from Amazonian floodplains.

    Science.gov (United States)

    Bracho-Nunez, Araceli; Knothe, Nina Maria; Costa, Wallace R; Maria Astrid, Liberato R; Kleiss, Betina; Rottenberger, Stefanie; Piedade, Maria Teresa Fernandez; Kesselmeier, Jürgen

    2012-01-01

    Volatile organic compound (VOC) emissions are affected by a variety of biotic and abiotic factors such as light intensity, temperature, CO2 and drought. Another stress factor, usually overlooked but very important for the Amazon region, is flooding. We studied the exchange of VOCs in relation to CO2 exchange and transpiration of 8 common tree species from the Amazonian floodplain forest grown up from seeds using a dynamic enclosure system. Analysis of volatile organics was performed by PTR-MS fast online measurements. Our study confirmed emissions of ethanol and acetaldehyde at the beginning of root anoxia after inundation, especially in less anoxia adapted species such as Vatairea guianensis, but not for Hevea spruceana probably due to a better adapted metabolism. In contrast to short-term inundation, long-term flooding of the root system did not result in any emission of ethanol or/and acetaldehyde. Emission of other VOCs, such as isoprenoids, acetone, and methanol exhibited distinct behavior related to the origin (igapó or várzea type of floodplain) of the tree species. Also physiological activities exhibited different response patterns for trees from igapó or várzea. In general, isoprenoid emissions increased within the course of some days of short-term flooding. After a long period of waterlogging, VOC emissions decreased considerably, along with photosynthesis, transpiration and stomatal conductance. However, even under long-term testing conditions, two tree species did not show any significant decrease or increase in photosynthesis. In order to understand ecophysiological advantages of the different responses we need field investigations with adult tree species.

  11. DOES ENERGY CONSUMPTION VOLATILITY AFFECT REAL GDP VOLATILITY? AN EMPIRICAL ANALYSIS FOR THE UK

    Directory of Open Access Journals (Sweden)

    Abdul Rashid

    2013-10-01

    Full Text Available This paper empirically examines the relation between energy consumption volatility and unpredictable variations in real gross domestic product (GDP in the UK. Estimating the Markov switching ARCH model we find a significant regime switching in the behavior of both energy consumption and GDP volatility. The results from the Markov regime-switching model show that the variability of energy consumption has a significant role to play in determining the behavior of GDP volatilities. Moreover, the results suggest that the impacts of unpredictable variations in energy consumption on GDP volatility are asymmetric, depending on the intensity of volatility. In particular, we find that while there is no significant contemporaneous relationship between energy consumption volatility and GDP volatility in the first (low-volatility regime, GDP volatility is significantly positively related to the volatility of energy utilization in the second (high-volatility regime.

  12. Isolation and Characterization of an Acyclic Isoprenoid from Semecarpus anacardium Linn. and its Antibacterial Potential in vitro - Antimicrobial Activity of Semecarpus anacardium Linn. Seeds -

    Directory of Open Access Journals (Sweden)

    Ayyakkannu Purushothaman

    2017-06-01

    Full Text Available Objectives: Semecarpus anacardium Linn. is a plant well-known for its antimicrobial, antidiabetic and anti-arthritic properties in the Ayurvedic and Siddha system of medicine. This has prompted the screening of this plant for antibacterial activity. The main aims of this study were to isolate compounds from the plant’s seeds and to evaluate their antibacterial effects on clinical bacterial test strains. Methods: The n-butanolic concentrate of the seed extract was subjected to thin layer chromatography (TLC and repeated silica gel column chromatography followed by elution with various solvents. The compound was identified based on observed spectral (IR, 1H NMR, 13C NMR and high-resolution mass spectrometry data. The well diffusion method was employed to evaluate the antibacterial activities of the isolated acyclic isoprenoid compound (final concentration: 5 - 15 μg/mL on four test bacterial strains, namely, Staphylococcus aureus (MTCC 96, Bacillus cereus

  13. Factors affecting the volatilization of volatile organic compounds from wastewater

    Directory of Open Access Journals (Sweden)

    Junya Intamanee

    2006-09-01

    Full Text Available This study aimed to understand the influence of the wind speed (U10cm, water depth (h and suspended solids (SS on mass transfer coefficient (KOLa of volatile organic compounds (VOCs volatilized from wastewater. The novelty of this work is not the method used to determine KOLa but rather the use of actual wastewater instead of pure water as previously reported. The influence of U10cm, h, and SS on KOLa was performed using a volatilization tank with the volume of 100-350 L. Methyl Ethyl Ketone (MEK was selected as a representative of VOCs investigated here in. The results revealed that the relationship between KOLa and the wind speeds falls into two regimes with a break at the wind speed of 2.4 m/s. At U10cm 2.4 m/s, KOLa increased more rapidly. The relationship between KOLa and U10cm was also linear but has a distinctly higher slope. For the KOLa dependency on water depth, the KOLa decreased significantly with increasing water depth up to a certain water depth after that the increase in water depth had small effect on KOLa. The suspended solids in wastewater also played an important role on KOLa. Increased SS resulted in a significant reduction of KOLa over the investigated range of SS. Finally, the comparison between KOLa obtained from wastewater and that of pure water revealed that KOLa from wastewater were much lower than that of pure water which was pronounced at high wind speed and at small water depth. This was due the presence of organic mass in wastewater which provided a barrier to mass transfer and reduced the degree of turbulence in the water body resulting in low volatilization rate and thus KOLa. From these results, the mass transfer model for predicting VOCs emission from wastewater should be developed based on the volatilization of VOCs from wastewater rather than that from pure water.

  14. Analysis of volatile nanoparticles emitted from diesel engine using TOF-SIMS and metal-assisted SIMS (MetA-SIMS)

    Science.gov (United States)

    Inoue, Masae; Murase, Atsushi; Yamamoto, Masami; Kubo, Shuichi

    2006-07-01

    Time-of-flight secondary ion mass spectrometry (TOF-SIMS) and metal-assisted SIMS (MetA-SIMS), which is TOF-SIMS analysis of metal-deposited sample surfaces, were applied to analyze small quantities of volatile nanoparticles emitted from a light-duty diesel engine under idling and deceleration conditions. We investigated nucleation materials, i.e., >C35 hydrocarbons, oxidation products, etc., which have lower volatility than the main components of volatile nanoparticles and control the formation of volatile nanoparticles. Oxygenated hydrocarbons were detected by TOF-SIMS in volatile nanoparticles under idling condition. Their relative intensities increased as particle diameter decreased. This resulted in the oxygenated hydrocarbons acting as nucleation materials for volatile nanoparticles under idling condition. High-molecular-weight hydrocarbons of greater than C35 were detected in volatile nanoparticles under deceleration condition by MetA-SIMS. It was concluded that the detected hydrocarbons originated in lubricants and acted as nucleation materials for volatile nanoparticles under deceleration condition. TOF-SIMS makes it possible to detect traces of low-volatility molecules due to its high-vacuum environment. MetA-SIMS is the only method of directly detecting high-molecular-weight hydrocarbons in small quantities of nanoparticles. TOF-SIMS and MetA-SIMS were proved to be useful tools for analyzing of the properties of volatile nanoparticles.

  15. Metabolic Control of Avocado Fruit Growth (Isoprenoid Growth Regulators and the Reaction Catalyzed by 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase).

    Science.gov (United States)

    Cowan, A. K.; Moore-Gordon, C. S.; Bertling, I.; Wolstenholme, B. N.

    1997-06-01

    The effect of isoprenoid growth regulators on avocado (Persea americana Mill. cv Hass) fruit growth and mesocarp 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) activity was investigated during the course of fruit ontogeny. Both normal and small-fruit phenotypes were used to probe the interaction between the end products of isoprenoid biosynthesis and the activity of HMGR in the metabolic control of avocado fruit growth. Kinetic analysis of the changes in both cell number and size revealed that growth was limited by cell number in phenotypically small fruit. In small fruit a 70% reduction in microsomal HMGR activity was associated with an increased mesocarp abscisic acid (ABA) concentration. Application of mevastatin, a competitive inhibitor of HMGR, reduced the growth of normal fruit and increased mesocarp ABA concentration. These effects were reversed by co-treatment of fruit with mevalonic acid lactone, isopentenyladenine, or N-(2-chloro-4-pyridyl)-N-phenylurea, but were not significantly affected by either gibberellic acid or stigmasterol. However, stigmasterol appeared to partially restore fruit growth when co-injected with mevastatin in either phase II or III of fruit growth. In vivo application of ABA reduced fruit growth and mesocarp HMGR activity and accelerated fruit abscission, effects that were reversed by co-treatment with isopentenyladenine. Together, these observations indicate that ABA accumulation down-regulates mesocarp HMGR activity and fruit growth, and that in situ cytokinin biosynthesis modulates these effects during phase I of fruit ontogeny, whereas both cytokinins and sterols seem to perform this function during the later phases.

  16. Volatile phenols in wine: Control measures of Brettanomyces/Dekkera yeasts

    Directory of Open Access Journals (Sweden)

    Sanja Šućur

    2016-10-01

    Full Text Available This review focuses on the considerable amount of research regarding volatile phenols production by Brettanomyces and on microbiological and technological parameters that influence development of these compounds during all stages of grape processing and winemaking. Also, volatile phenols impact on wine aroma and quality and prevention methods were discussed. The yeast genus Brettanomyces is the major microorganism that has the ability to convert hydroxycinnamic acids into significant concentration of phenolic compounds, especially of 4-ethylphenol and 4-ethylguaiacol, in red wine. When volatile phenols reach concentrations above the sensory threshold in wine, it is then characterized as wine with fault. In order to control the growth of Brettanomyces and preclude volatile phenols production, it is helpful to keep good quality of grape, winery sanitation, control of oxygen and sulphite level, as well as orderly check physiochemical composition of wine.

  17. Alumina Volatility in Water Vapor at Elevated Temperatures: Application to Combustion Environments

    Science.gov (United States)

    Opila, Elizabeth J.; Myers, Dwight L.

    2003-01-01

    The volatility of alumina in high temperature water vapor was determined by measuring weight loss of sapphire coupons at temperatures between 1250 and 1500 C, water vapor partial pressures between 0.15 and 0.68 atm in oxygen, at one atmosphere total pressure, and a gas velocity of 4.4 centimeters per second. The variation of the volatility with water vapor partial pressure was consistent with Al(OH)3(g) formation. The enthalpy of reaction to form Al(OH)3(g) from alumina and water vapor was found to be 210 plus or minus 20 kJ/mol. Surface rearrangement of ground sapphire surfaces increased with water vapor partial pressure, temperature and volatility rate. Recession rates of alumina due to volatility were determined as a function of water vapor partial pressure and temperature to evaluate limits for use of alumina in long term applications in combustion environments.

  18. Modeling the Volatility in Global Fertilizer Prices

    NARCIS (Netherlands)

    P-Y. Chen (Ping-Yu); C-L. Chang (Chia-Lin); C-C. Chen (Chi-Chung); M.J. McAleer (Michael)

    2010-01-01

    textabstractThe main purpose of this paper is to estimate the volatility in global fertilizer prices. The endogenous structural breakpoint unit root test and alternative volatility models, including the generalized autoregressive conditional heteroskedasticity (GARCH) model, Exponential GARCH (EGARC

  19. Fluctuation behaviors of financial return volatility duration

    Science.gov (United States)

    Niu, Hongli; Wang, Jun; Lu, Yunfan

    2016-04-01

    It is of significantly crucial to understand the return volatility of financial markets because it helps to quantify the investment risk, optimize the portfolio, and provide a key input of option pricing models. The characteristics of isolated high volatility events above certain threshold in price fluctuations and the distributions of return intervals between these events arouse great interest in financial research. In the present work, we introduce a new concept of daily return volatility duration, which is defined as the shortest passage time when the future volatility intensity is above or below the current volatility intensity (without predefining a threshold). The statistical properties of the daily return volatility durations for seven representative stock indices from the world financial markets are investigated. Some useful and interesting empirical results of these volatility duration series about the probability distributions, memory effects and multifractal properties are obtained. These results also show that the proposed stock volatility series analysis is a meaningful and beneficial trial.

  20. A Fractionally Integrated Wishart Stochastic Volatility Model

    NARCIS (Netherlands)

    M. Asai (Manabu); M.J. McAleer (Michael)

    2013-01-01

    textabstractThere has recently been growing interest in modeling and estimating alternative continuous time multivariate stochastic volatility models. We propose a continuous time fractionally integrated Wishart stochastic volatility (FIWSV) process. We derive the conditional Laplace transform of

  1. SESQUITERPENE RICH VOLATILE SEED OIL OF TAGETES PATULA L. FROM NORTHWEST IRAN

    Directory of Open Access Journals (Sweden)

    M. B. HASSANPOURAGHDAM

    2011-10-01

    Full Text Available Hydrodistilled volatile seed oil composition of commonly growing ornamental Tagetes patula L. was analyzed for its constituents by GC/MS. Forty constituents were identified, comprising 94% of the total oil. Sesquiterpene hydrocarbons (52.7% and oxygenated sesquiterpenes (15.8% were the main subclasses of volatile oil components followed by monoterpene hydrocarbons (12.6%. The principle constituents of the volatile oil were (E-caryophyllene (44.6% caryophyllene oxide (14.8%, germacrene D (3.8%, (Z-β-ocimene (3.8% and limonene (3.7%. From chemical point of view, oxides (15.7% were the predominant group of components with caryophyllene oxide as their main representative. α-terthienyl (3.8% comprised partially large amount in the volatile oil content despite of its polar and less-volatile nature. Taking into account the volatile oil profile, the chemical composition of the volatile seed oil of commonly growing ornamental T. patula L. was characterized as sesquiterpene and α-terthienyl rich one probably with appreciable biocidal (Insecticidal and nematicidal and pharmacological potential.

  2. Automated dynamic headspace/GC-MS analyses affect the repeatability of volatiles in irradiated Turkey.

    Science.gov (United States)

    Nam, Ki-Chang; Cordray, Joseph; Ahn, Dong U

    2004-03-24

    Although a dynamic headspace/gas chromatography-mass spectrometry (DH/GC-MS) method is an effective tool for determining volatiles of irradiated turkey meat, the profile of volatiles may be changeable depending upon the availability of oxygen in the sample vial and sample holding time before purge. The objective of this study was to evaluate the effects of helium flushing and sample holding time before purge on the volatiles profiles of irradiated raw and cooked turkey breast meat. Vacuum-packaged turkey breasts were irradiated at 2.5 kGy, and the volatiles of irradiated raw and cooked samples were analyzed using a DH/GC-MS with different holding times up to 280 min. The amounts of dimethyl disulfide and dimethyl trisulfide decreased as sample holding time in an autosampler (4 degrees C) before purge increased, whereas those of aldehdyes increased as holding time increased due to lipid oxidation. Helium flush of sample vials before sample loading on an autosampler retarded lipid oxidation and minimized the changes of sulfur volatiles in raw meat but was not enough to prevent oxidative changes in cooked meat. Although DH/GC-MS is a convenient method for automatic analysis of volatiles in meat samples, the number of samples that can be loaded in an autosampler at a time should be limited within the range that can permit reasonable repeatabilities for target volatile compounds.

  3. Stochastic Volatility and DSGE Models

    DEFF Research Database (Denmark)

    Andreasen, Martin Møller

    This paper argues that a specification of stochastic volatility commonly used to analyze the Great Moderation in DSGE models may not be appropriate, because the level of a process with this specification does not have conditional or unconditional moments. This is unfortunate because agents may...

  4. Volatiles produced by Staphylococcus xylosus and Staphylococcus carnosus during growth in sausage minces

    DEFF Research Database (Denmark)

    Stahnke, Marie Louise Heller

    1999-01-01

    of air. Volatiles produced by the cultures were collected during growth, identified and quantified. The data were analysed by partial least squares regression. The results showed that oxygen in general had more influence on the aroma producing capacity of Staphylococcus xylosus than of Staphylococcus...

  5. Reversible Oxygenation of Oxygen Transport Proteins.

    Science.gov (United States)

    Drain, C. M.; Corden, Barry B.

    1987-01-01

    Describes a lecture demonstration which illustrates changes in the visible spectra of oxygen transport proteins upon reversible oxygen binding. Provides a comparison of the physical characteristics of oxygen storage and transport proteins. Reviews essentials for preparation of the materials. (ML)

  6. Chemically-resolved aerosol volatility measurements from two megacity field studies

    Directory of Open Access Journals (Sweden)

    J. A. Huffman

    2009-09-01

    Full Text Available The volatilities of different chemical species in ambient aerosols are important but remain poorly characterized. The coupling of a recently developed rapid temperature-stepping thermodenuder (TD, operated in the range 54–230°C with a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS during field studies in two polluted megacities has enabled the first direct characterization of chemically-resolved urban particle volatility. Measurements in Riverside, CA and Mexico City are generally consistent and show ambient nitrate as having the highest volatility of any AMS standard aerosol species while sulfate showed the lowest volatility. Total organic aerosol (OA showed volatility intermediate between nitrate and sulfate, with an evaporation rate of 0.6%·K−1 near ambient temperature, although OA dominates the residual species at the highest temperatures. Different types of OA were characterized with marker ions, diurnal cycles, and positive matrix factorization (PMF and show significant differences in volatility. Reduced hydrocarbon-like OA (HOA, a surrogate for primary OA, POA, oxygenated OA (OOA, a surrogate for secondary OA, SOA, and biomass-burning OA (BBOA separated with PMF were all determined to be semi-volatile. The most aged OOA-1 and its dominant ion, CO2+, consistently exhibited the lowest volatility, with HOA, BBOA, and associated ions for each among the highest. The similar or higher volatility of HOA/POA compared to OOA/SOA contradicts the current representations of OA volatility in most atmospheric models and has important implications for aerosol growth and lifetime. A new technique using the AMS background signal was demonstrated to quantify the fraction of species up to four orders-of-magnitude less volatile than those detectable in the MS mode, which for OA represent ~5% of the non-refractory (NR OA signal. Our results strongly imply that all OA types should be considered

  7. Business Cycles, Financial Crises, and Stock Volatility

    OpenAIRE

    G. William Schwert

    1989-01-01

    This paper shows that stock volatility increases during recessions and financial crises from 1834-1987. The evidence reinforces the notion that stock prices are an important business cycle indicator. Using two different statistical models for stock volatility, I show that volatility increases after major financial crises. Moreover. stock volatility decreases and stock prices rise before the Fed increases margin requirements. Thus, there is little reason to believe that public policies can con...

  8. Decomposing European bond and equity volatility

    DEFF Research Database (Denmark)

    Christiansen, Charlotte

    The paper investigates volatility spillover from US and aggregate European asset markets into European national asset markets. A main contribution is that bond and equity volatilities are analyzed simultaneously. A new model belonging to the "volatilityspillover" family is suggested: The conditio...... (stock) volatilities are mainly influenced by bond (stock) effects. Global, regional, and local volatility effects are all important. The introduction of the euro is associated with a structural break....

  9. The january effect across volatility regimes

    OpenAIRE

    Agnani, Betty; Aray, Henry

    2007-01-01

    Using a Markov regime switching model, this article presents evidence on the well-known January effect on stock returns. The specification allows a distinction to be drawn between two regimes, one with high volatility and other with low volatility. We obtain a time-varying January effect that is, in general, positive and significant in both volatility regimes. However, this effect is larger in the high volatility regime. In sharp contrast with most previous literature we find two major result...

  10. Exponential Smoothing, Long Memory and Volatility Prediction

    DEFF Research Database (Denmark)

    Proietti, Tommaso

    Extracting and forecasting the volatility of financial markets is an important empirical problem. The paper provides a time series characterization of the volatility components arising when the volatility process is fractionally integrated, and proposes a new predictor that can be seen as extensi...... methods for forecasting realized volatility, and that the estimated model confidence sets include the newly proposed fractional lag predictor in all occurrences....

  11. Possible Sources of Polar Volatiles

    Science.gov (United States)

    Schultz, P. H.

    2011-12-01

    Extensive analyses of returned Apollo samples demonstrated that the Moon is extremely volatile poor. While this conclusion remains true, various measurements since the late 90's implicated the presence of water: e.g., enhanced reflection of circularly polarized radar signals and suppression of epithermal neutrons near the poles. More recently, traces of H2O have been discovered inside volcanic glass, along with more significant amounts residing in hydrous minerals (apatite) returned from both highland and mare landing sites. Three recent lunar missions (DIXI, M3, Cassini) identified hydrous phases on/near the lunar surface, whereas the LCROSS probe detected significant quantities of volatiles (OH, H2O and other volatiles) excavated by the Centaur impact. These new mission results and sample studies, however, now allow testing different hypotheses for the generation, trapping, and replenishment of these volatiles. Solar-proton implantation must contribute to the hydrous phases in the lunar regolith in order to account for the observed time-varying abundances and occurrence near the lunar equator. This also cannot be the entire story. The relatively low speed LCROSS-Centaur impact (2.5km/s) could not vaporize such hydrous minerals, yet emissions lines of OH (from the thermal disassociation of H2O), along with other compounds (CO2, NH2) were detected within the first second, before ejecta could reach sunlight. Telescopic observations by Potter and Morgan (1985) discovered a tenuous lunar atmosphere of Na, but the LCROSS UV/Vis spectrometer did not detect the Na-D line until after the ejecta reached sunlight (along with a line pair attributed to Ag). With time, other volatile species emerged (OH, CO). The LAMP instrument on the Lunar Reconnaissance Orbiter had a different viewpoint from the side (rather than from above) and detected many other atomic species release by the LCROSS-Centaur impact. Consequently, it appears that there is a stratigraphy for trapped species

  12. Online measurements of the emissions of intermediate-volatility and semi-volatile organic compounds from aircraft

    Directory of Open Access Journals (Sweden)

    E. S. Cross

    2013-08-01

    Full Text Available A detailed understanding of the climate and air quality impacts of aviation requires measurements of the emissions of intermediate-volatility and semi-volatile organic compounds (I/SVOCs from aircraft. Currently both the amount and chemical composition of aircraft I/SVOC emissions remain poorly characterized. Here we characterize I/SVOC emissions from aircraft, using a novel instrument for the online, quantitative measurement of the mass loading and composition of low-volatility organic vapors. Emissions from the NASA DC8 aircraft were sampled on the ground 143 m downwind of the engines and characterized as a function of engine power from idle (4% maximum rated thrust through 85% power. Results show that I/SVOC emissions are highest during engine idle operating conditions, with decreasing but non-zero I/SVOC emissions at higher engine powers. Comparison of I/SVOC emissions with total hydrocarbon (THC measurements, VOC measurements, and an established emissions profile indicates that I/SVOCs comprise 10–20% of the total organic gas-phase emissions at idle, and an increasing fraction of the total gas-phase organic emissions at higher powers. Positive matrix factorization of online mass spectra is used to identify three distinct types of I/SVOC emissions: aliphatic, aromatic and oxygenated. The volatility and chemical composition of the emissions suggest that unburned fuel is the dominant source of I/SVOCs at idle, while pyrolysis products make up an increasing fraction of the I/SVOCs at higher powers. Oxygenated I/SVOC emissions were detected at lower engine powers (≤30% and may be linked to cracked, partially oxidized or unburned fuel components.

  13. Online measurements of the emissions of intermediate-volatility and semi-volatile organic compounds from aircraft

    Directory of Open Access Journals (Sweden)

    E. S. Cross

    2013-03-01

    Full Text Available A detailed understanding of the climate and air quality impacts of aviation requires detailed measurements of the emissions of intermediate-volatility and semi-volatile organic compounds (I/SVOCs from aircraft. Currently both the amount and chemical composition of aircraft I/SVOC emissions remain poorly characterized. Here we characterize I/SVOC emissions from aircraft, using a novel instrument for the online, quantitative measurement of the mass loading and composition of low-volatility organic vapors. Emissions from the NASA DC8 aircraft were sampled on the ground, 143 m downwind of the engines and characterized as a function of engine power from ground idle (~4% maximum rated thrust through 85% power. Results show that I/SVOC emissions are highest during engine-idle operating conditions, with decreasing but non-zero I/SVOC emissions at higher engine powers. Comparison of I/SVOC emissions with total hydrocarbon (THC measurements, VOC measurements, and an established emissions profile indicates that I/SVOCs comprise 10–20% of the total organic gas phase emissions at idle, and an increasing fraction of the total gas phase organic emissions at higher powers. Positive matrix factorization of online mass spectra is used to identify three distinct types of I/SVOC emissions: aliphatic, aromatic and oxygenated. The volatility and chemical composition of the emissions suggest that unburned fuel is the dominant source of I/SVOCs at idle, while pyrolysis products make up an increasing fraction of the I/SVOCs at higher powers. Oxygenated I/SVOC emissions were detected at lower engine powers (≤30% and may be linked to cracked, partially oxidized or unburned fuel components.

  14. Oil Volatility Risk and Expected Stock Returns

    DEFF Research Database (Denmark)

    Christoffersen, Peter; Pan, Xuhui (Nick)

    After the financialization of commodity futures markets in 2004-05 oil volatility has become a strong predictor of returns and volatility of the overall stock market. Furthermore, stocks' exposure to oil volatility risk now drives the cross-section of expected returns. The difference in average r...

  15. Volatiles in inter-specific bacterial interactions

    NARCIS (Netherlands)

    Tyc, O.; Zweers, H.; De Boer, W.; Garbeva, P.V.

    2015-01-01

    The importance of volatile organic compounds for functioning of microbes is receiving increased research attention. However, to date very little is known on how inter-specific bacterial interactions effect volatiles production as most studies have been focused on volatiles produced by monocultures o

  16. Volatiles in inter-specific bacterial interactions

    NARCIS (Netherlands)

    Tyc, O.; Zweers, H.; De Boer, W.; Garbeva, P.V.

    2015-01-01

    The importance of volatile organic compounds for functioning of microbes is receiving increased research attention. However, to date very little is known on how inter-specific bacterial interactions effect volatiles production as most studies have been focused on volatiles produced by monocultures

  17. Ammonia volatilization from intensively managed dairy pastures.

    NARCIS (Netherlands)

    Bussink, D.W.

    1996-01-01

    The objectives of this thesis are (i) to quantify NH 3 volatilization from grassland, (ii) to gain understanding of the NH3 volatilization processes on grassland and (iii) to study measures how to reduce NH 3 volatilization from gra

  18. Oil Volatility Risk and Expected Stock Returns

    DEFF Research Database (Denmark)

    Christoffersen, Peter; Pan, Xuhui (Nick)

    After the financialization of commodity futures markets in 2004-05 oil volatility has become a strong predictor of returns and volatility of the overall stock market. Furthermore, stocks' exposure to oil volatility risk now drives the cross-section of expected returns. The difference in average r...

  19. Cost Linkages Transmit Volatility Across Markets

    DEFF Research Database (Denmark)

    Nguyen, Daniel Xuyen; Schaur, Georg

    to link the domestic and export supply costs. This theoretical contribution has two new implications for the exporting firm. First, the demand volatility in the foreign market now directly affects the firm's domestic sales volatility. Second, firms hedge domestic demand volatility with exports. The model...

  20. Formation of volatile chemicals from thermal degradation of less volatile coffee components: quinic acid, caffeic acid, and chlorogenic acid.

    Science.gov (United States)

    Moon, Joon-Kwan; Shibamoto, Takayuki

    2010-05-12

    The less volatile constituents of coffee beans (quinic acid, caffeic acid, and chlorogenic acid) were roasted under a stream of nitrogen, air, or helium. The volatile degradation compounds formed were analyzed by gas chromatography and gas chromatography-mass spectrometry. Caffeic acid produced the greatest amount of total volatiles. Quinic acid and chlorogenic acid produced a greater number of volatiles under the nitrogen stream than under the air stream. These results suggest that the presence of oxygen does not play an important role in the formation of volatile compounds by the heat degradation of these chemicals. 2,5-Dimethylfuran formed in relatively large amounts (59.8-2231.0 microg/g) in the samples obtained from quinic acid and chlorogenic acid but was not found in the samples from caffeic acid. Furfuryl alcohol was found in the quinic acid (259.9 microg/g) and caffeic acid (174.4 microg/g) samples roasted under a nitrogen stream but not in the chlorogenic sample. The three acids used in the present study do not contain a nitrogen atom, yet nitrogen-containing heterocyclic compounds, pyridine, pyrrole, and pyrazines, were recovered. Phenol and its derivatives were identified in the largest quantities. The amounts of total phenols ranged from 60.6 microg/g (quinic acid under helium) to 89893.7 microg/g (caffeic acid under helium). It was proposed that phenol was formed mainly from quinic acid and that catechols were formed from caffeic acid. Formation of catechol from caffeic acid under anaerobic condition indicates that the reaction participating in catechol formation was not oxidative degradation.

  1. Volatile components associated with bacterial spoilage of tropical prawns

    DEFF Research Database (Denmark)

    Chinivasagam, H.N.; Bremner, Allan; Wood, A.F.

    1998-01-01

    Analysis of headspace volatiles by gas chromatography/mass spectrometry from king (Penaeus plebejus), banana (P. merguiensis), tiger (P. esculentus/semisulcatus) and greasy (Metapenaeus bennettae) prawns stored in ice or ice slurry, which is effectively an environment of low oxygen tension......, whereas sulphides and amines occurred whether the predominant spoilage organism was Ps.fragi or Shewanella putrefaciens. The free amino acid profiles of banana and king prawns were high in arginine (12-14%) and low in cysteine (0.1-0.17%) and methionine (0.1-0.2%). Filter sterilised raw banana prawn broth...

  2. Radiation-induced volatile hydrocarbon production in platelets

    Energy Technology Data Exchange (ETDEWEB)

    Radha, E.; Vaishnav, Y.N.; Kumar, K.S.; Weiss, J.F.

    1989-01-01

    Generation of volatile hydrocarbons (ethane, pentane) as a measure of lipid peroxidation was followed in preparations from platelet-rich plasma irradiated in vitro. The hydrocarbons in the headspace of sealed vials containing irradiated and nonirradiated washed platelets, platelet-rich plasma, or platelet-poor plasma increased with time. The major hydrocarbon, pentane, increased linearly and significantly with increasing log radiation dose, suggesting that reactive oxygen species induced by ionizing radiation result in lipid peroxidation. Measurements of lipid peroxidation products may give an indication of suboptimal quality of stored and/or irradiated platelets.

  3. Mantle Volatiles - Distribution and Consequences

    Science.gov (United States)

    Luth, R. W.

    2003-12-01

    Volatiles in the mantle have, for many years, been the subject of intensive study from a number of perspectives. They are of interest because of their potential effects on melting relationships, on transport of major and trace elements, and on the rheological and other physical properties of the mantle. By convention, "volatiles" in this context are constituents that are liquid or gaseous at normal Earth surface conditions. This review will look at the behavior of C-O-H-S-halogen volatiles, beginning with H2O and C-O volatiles.There have been tremendous strides made recently towards understanding how volatiles in general and water in particular is transported and stored in the mantle. This progress is based on research on a number of fronts: studies of mantle-derived samples have provided insight into the nature and occurrence of hydrous phases such as amphibole, mica, and chlorite, and have provided constraints on the capacity of nominally anhydrous minerals (NAMs) such as olivine, pyroxenes, and garnet to contain "water" by a variety of substitution mechanisms. Experimental studies on mantle-derived magmas have provided constraints on volatile contents in their source regions. Other studies have constrained the pressure, temperature, and composition conditions over which hydrous phases are stable in the mantle.Fundamental questions remain about the geochemical cycling of volatiles in the mantle, and between the mantle and the surface. Much attention has focused on the capability of hydrous phases such as amphibole, mica, serpentine, chlorite, and a family of "dense hydrous magnesian silicates" (DHMSs) to act as carriers of water in subducting slabs back into the mantle. It has been clear since the work of Ito et al. (1983) that there is a discrepancy between the amount of volatiles subducted into the mantle and those returned to the surface by arc magmatism. A recent overview of volatile cycling in subduction systems by Bebout (1996) suggests that 5-15% of the H2

  4. Level Shifts in Volatility and the Implied-Realized Volatility Relation

    DEFF Research Database (Denmark)

    Christensen, Bent Jesper; de Magistris, Paolo Santucci

    to the multivariate case of the univariate level shift technique by Lu and Perron (2008). An application to the S&P500 index and a simulation experiment show that the recently documented empirical properties of strong persistence in volatility and forecastability of future realized volatility from current implied...... volatility, which have been interpreted as long memory (or fractional integration) in volatility and fractional cointegration between implied and realized volatility, are accounted for by occasional common level shifts....

  5. The economic value of realized volatility

    DEFF Research Database (Denmark)

    Christoffersen, Peter; Feunou, Bruno; Jacobs, Kris

    2014-01-01

    Many studies have documented that daily realized volatility estimates based on intraday returns provide volatility forecasts that are superior to forecasts constructed from daily returns only. We investigate whether these forecasting improvements translate into economic value added. To do so, we...... develop a new class of affine discrete-time option valuation models that use daily returns as well as realized volatility. We derive convenient closed-form option valuation formulas, and we assess the option valuation properties using Standard & Poor’s (S&P) 500 return and option data. We find...... that realized volatility reduces the pricing errors of the benchmark model significantly across moneyness, maturity, and volatility levels....

  6. Molecular Diffusion of Volatiles in Lunar Regolith during the Resource Prospector Mission Sample Acquisition

    Science.gov (United States)

    Teodoro, L. A.; Colaprete, A.; Roush, T. L.; Elphic, R. C.; Cook, A.; Kleinhenz, J.; Fritzler, E.; Smith, J. T.; Zacny, K.

    2016-12-01

    In the context of NASA's Resource Prospector (RP) mission to the high latitudes and permanently shadowed regions of the Moon, we study 3D models of volatile transport in the lunar regolith. This mission's goal is to extract and identify volatile species in the top meter of the lunar regolith layer. Roughly, RP consists of 5 elements: i) the Neutron Spectrometer System will search for high hydrogen concentrations and in turn select optimum drilling locations; ii) The Near Infrared Volatile Spectrometer System (NIRVSS) will characterize the nature of the surficial water ice; iii) The Drill Sub-system will extract samples from the top meter of the lunar surface and deliver them to the Oxygen and Volatile Extraction Node (OVEN); iv) OVEN will heat up the sample and extract the volatiles therein, that will be v) transferred to the Lunar Advanced Volatiles Analysis system for chemical composition analysis. A series of vacuum cryogenic experiments have been carried out at Glenn Research Center with the aim of quantifying the volatile losses during the drilling/sample acquisition phase and sample delivery to crucibles steps. These experiments' outputs include: i) Pressure measurements of several chemical species (e.g. H2O, Ar); ii) Temperature measurements within and at the surface of the lunar simulant using thermocouples; and iii) Surficial temperature NIRVSS measurements. Here, we report on the numerical modeling we are carrying out to understand the physics underpinning these experiments. The models include 2 main parts: i) reliable computation of temperature variation throughout the lunar soil container during the experiment as constrained by temperature measurements; and ii) molecular diffusion of volatiles. The latter includes both Fick's (flight of the molecules in the porous) and Knudsen's (sublimation of volatile molecules at the grain surface) laws. We also mimic the soil porosity by randomly allocating 75 microns particles in the simulation volume. Our

  7. Comparative Analysis of Flower Volatiles from Nine Citrus at Three Blooming Stages

    Directory of Open Access Journals (Sweden)

    Muhammad Azam

    2013-11-01

    Full Text Available Volatiles from flowers at three blooming stages of nine citrus cultivars were analyzed by headspace-solid phase microextraction (HS-SPME-GC-MS. Up to 110 volatiles were detected, with 42 tentatively identified from citrus flowers for the first time. Highest amounts of volatiles were present in fully opened flowers of most citrus, except for pomelos. All cultivars were characterized by a high percentage of either oxygenated monoterpenes or monoterpene hydrocarbons, and the presence of a high percentage of nitrogen containing compounds was also observed. Flower volatiles varied qualitatively and quantitatively among citrus types during blooming. Limonene was the most abundant flower volatile only in citrons; α-citral and β-citral ranked 2nd and 3rd only for Bergamot, and unopened flowers of Ponkan had a higher amount of linalool and β-pinene while much lower amount of γ-terpinene and p-cymene than Satsuma. Taking the average of all cultivars, linalool and limonene were the top two volatiles for all blooming stages; β-pinene ranked 3rd in unopened flowers, while indole ranked 3rd for half opened and fully opened flower volatiles. As flowers bloomed, methyl anthranilate increased while 2-hexenal and p-cymene decreased. In some cases, a volatile could be high in both unopened and fully opened flowers but low in half opened ones. Through multivariate analysis, the nine citrus cultivars were clustered into three groups, consistent with the three true citrus types. Furthermore, an influence of blooming stages on clustering was observed, especially with hybrids Satsuma and Huyou. Altogether, it was suggested that flower volatiles can be suitable markers for revealing the genetic relationships between citrus cultivars but the same blooming stage needs to be strictly controlled.

  8. Mars volatile evolution - Implications of the recent measurement of O-17 in water from the SNC meteorites

    Science.gov (United States)

    Jakosky, Bruce M.

    1993-01-01

    Escape of oxygen to space on Mars is capable of producing a fractionation of oxygen isotopes in the remaining oxygen which is off of the fractionation line produced by the usual mass-dependent exchange processes. The magnitude of fractionation which can occur can be larger than that which was measured in oxygen in water derived from the SNC meteorites (thought to have come from Mars). In conjunction with the apparent lack of fractionation of O-18 in the atmosphere, this result suggests that less than 25 percent of the oxygen in the Martian climate system has been lost over geologic time. Other mechanisms also might be able to produce such a fractionation, so that this conclusion is not unique; however, it is consistent with other lines of evidence. There is no requirement for an initial volatile inventory with an isotopic composition different from that of the bulk planet (as might be the case for a late veneer of volatile-rich material).

  9. Arbitrage and Volatility in Chinese Stock's Markets

    Science.gov (United States)

    Lu, Shu Quan; Ito, Takao; Zhang, Jianbo

    From the point of view of no-arbitrage pricing, what matters is how much volatility the stock has, for volatility measures the amount of profit that can be made from shorting stocks and purchasing options. With the short-sales constraints or in the absence of options, however, high volatility is likely to mean arbitrage from stock market. As emerging stock markets for China, investors are increasingly concerned about volatilities of Chinese two stock markets. We estimate volatility's models for Chinese stock markets' indexes using Markov chain Monte Carlo (MCMC) method and GARCH. We find that estimated values of volatility parameters are very high for all data frequencies. It suggests that stock returns are extremely volatile even at long term intervals in Chinese markets. Furthermore, this result could be considered that there seems to be arbitrage opportunities in Chinese stock markets.

  10. Forecasting volatility of crude oil markets

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Sang Hoon [Department of Business Administration, Gyeongsang National University, Jinju, 660-701 (Korea); Kang, Sang-Mok; Yoon, Seong-Min [Department of Economics, Pusan National University, Busan, 609-735 (Korea)

    2009-01-15

    This article investigates the efficacy of a volatility model for three crude oil markets - Brent, Dubai, and West Texas Intermediate (WTI) - with regard to its ability to forecast and identify volatility stylized facts, in particular volatility persistence or long memory. In this context, we assess persistence in the volatility of the three crude oil prices using conditional volatility models. The CGARCH and FIGARCH models are better equipped to capture persistence than are the GARCH and IGARCH models. The CGARCH and FIGARCH models also provide superior performance in out-of-sample volatility forecasts. We conclude that the CGARCH and FIGARCH models are useful for modeling and forecasting persistence in the volatility of crude oil prices. (author)

  11. Chirospecific analysis of plant volatiles

    Energy Technology Data Exchange (ETDEWEB)

    Tkachev, A V [N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, Novosibirsk (Russian Federation)

    2007-10-31

    Characteristic features of the analysis of plant volatiles by enantioselective gas (gas-liquid) chromatography and gas chromatography/mass spectrometry are discussed. The most recent advances in the design of enantioselective stationary phases are surveyed. Examples of the preparation of the most efficient phases based on modified cyclodextrins are given. Current knowledge on the successful analytical resolution of different types of plant volatiles (aliphatic and aromatic compounds and mono-, sesqui- and diterpene derivatives) into optical antipodes is systematically described. Chiral stationary phases used for these purposes, temperature conditions and enantiomer separation factors are summarised. Examples of the enantiomeric resolution of fragrance compounds and components of plant extracts, wines and essential oils are given.

  12. Chirospecific analysis of plant volatiles

    Science.gov (United States)

    Tkachev, A. V.

    2007-10-01

    Characteristic features of the analysis of plant volatiles by enantioselective gas (gas-liquid) chromatography and gas chromatography/mass spectrometry are discussed. The most recent advances in the design of enantioselective stationary phases are surveyed. Examples of the preparation of the most efficient phases based on modified cyclodextrins are given. Current knowledge on the successful analytical resolution of different types of plant volatiles (aliphatic and aromatic compounds and mono-, sesqui- and diterpene derivatives) into optical antipodes is systematically described. Chiral stationary phases used for these purposes, temperature conditions and enantiomer separation factors are summarised. Examples of the enantiomeric resolution of fragrance compounds and components of plant extracts, wines and essential oils are given.

  13. Volatiles in Inter-Specific Bacterial Interactions.

    Science.gov (United States)

    Tyc, Olaf; Zweers, Hans; de Boer, Wietse; Garbeva, Paolina

    2015-01-01

    The importance of volatile organic compounds for functioning of microbes is receiving increased research attention. However, to date very little is known on how inter-specific bacterial interactions effect volatiles production as most studies have been focused on volatiles produced by monocultures of well-described bacterial genera. In this study we aimed to understand how inter-specific bacterial interactions affect the composition, production and activity of volatiles. Four phylogenetically different bacterial species namely: Chryseobacterium, Dyella, Janthinobacterium, and Tsukamurella were selected. Earlier results had shown that pairwise combinations of these bacteria induced antimicrobial activity in agar media whereas this was not the case for monocultures. In the current study, we examined if these observations were also reflected by the production of antimicrobial volatiles. Thus, the identity and antimicrobial activity of volatiles produced by the bacteria were determined in monoculture as well in pairwise combinations. Antimicrobial activity of the volatiles was assessed against fungal, oomycetal, and bacterial model organisms. Our results revealed that inter-specific bacterial interactions affected volatiles blend composition. Fungi and oomycetes showed high sensitivity to bacterial volatiles whereas the effect of volatiles on bacteria varied between no effects, growth inhibition to growth promotion depending on the volatile blend composition. In total 35 volatile compounds were detected most of which were sulfur-containing compounds. Two commonly produced sulfur-containing volatile compounds (dimethyl disulfide and dimethyl trisulfide) were tested for their effect on three target bacteria. Here, we display the importance of inter-specific interactions on bacterial volatiles production and their antimicrobial activities.

  14. Volatiles in inter-specific bacterial interactions

    Directory of Open Access Journals (Sweden)

    Olaf eTyc

    2015-12-01

    Full Text Available The importance of volatile organic compounds for functioning of microbes is receiving increased research attention. However, to date very little is known on how inter-specific bacterial interactions effect volatiles production as most studies have been focused on volatiles produced by monocultures of well described bacterial genera. In this study we aimed to understand how inter-specific bacterial interactions affect the composition, production and activity of volatiles. Four phylogenetically different bacterial species namely: Chryseobacterium, Dyella, Janthinobacterium and Tsukamurella were selected. Earlier results had shown that pairwise combinations of these bacteria induced antimicrobial activity in agar media whereas this was not the case for monocultures. In the current study, we examined if these observations were also reflected by the production of antimicrobial volatiles. Thus, the identity and antimicrobial activity of volatiles produced by the bacteria were determined in monoculture as well in pairwise combinations. Antimicrobial activity of the volatiles was assessed against fungal, oomycetal and bacterial model organisms. Our results revealed that inter-specific bacterial interactions affected volatiles blend composition. Fungi and oomycetes showed high sensitivity to bacterial volatiles whereas the effect of volatiles on bacteria varied between no effects, growth inhibition to growth promotion depending on the volatile blend composition. In total 35 volatile compounds were detected most of which were sulfur-containing compounds. Two commonly produced sulfur-containing volatile compounds (dimethyl disulfide and dimethyl trisulfide were tested for their effect on three target bacteria. Here we display the importance of inter-specific interactions on bacterial volatiles production and their antimicrobial activities.

  15. Money, banks and endogenous volatility

    OpenAIRE

    Pere Gomis-Porqueras

    2000-01-01

    In this paper I consider a monetary growth model in which banks provide liquidity, and the government fixes a constant rate of money creation. There are two underlying assets in the economy, money and capital. Money is dominated in rate of return. In contrast to other papers with a larger set of government liabilities, I find a unique equilibrium when agents' risk aversion is moderate. However, indeterminacies and endogenous volatility can be observed when agents are relatively risk averse.

  16. Volatility at Karachi Stock Exchange

    OpenAIRE

    Aslam Farid; Javed Ashraf

    1995-01-01

    Frequent “crashes” of the stock market reported during the year 1994 suggest that the Karachi bourse is rapidly converting into a volatile market. This cannot be viewed as a positive sign for this developing market of South Asia. Though heavy fluctuations in stock prices are not an unusual phenomena and it has been observed at almost all big and small exchanges of the world. Focusing on the reasons for such fluctuations is instructive and likely to have important policy implications. Proponen...

  17. Human skin volatiles: a review.

    Science.gov (United States)

    Dormont, Laurent; Bessière, Jean-Marie; Cohuet, Anna

    2013-05-01

    Odors emitted by human skin are of great interest to biologists in many fields; applications range from forensic studies to diagnostic tools, the design of perfumes and deodorants, and the ecology of blood-sucking insect vectors of human disease. Numerous studies have investigated the chemical composition of skin odors, and various sampling methods have been used for this purpose. The literature shows that the chemical profile of skin volatiles varies greatly among studies, and the use of different sampling procedures is probably responsible for some of these variations. To our knowledge, this is the first review focused on human skin volatile compounds. We detail the different sampling techniques, each with its own set of advantages and disadvantages, which have been used for the collection of skin odors from different parts of the human body. We present the main skin volatile compounds found in these studies, with particular emphasis on the most frequently studied body regions, axillae, hands, and feet. We propose future directions for promising experimental studies on odors from human skin, particularly in relation to the chemical ecology of blood-sucking insects.

  18. Occurrence and volatility of several trace elements in pulverized coal boiler

    Institute of Scientific and Technical Information of China (English)

    HUANG Ya-ji; JIN Bao-sheng; ZHONG Zhao-ping; XIAO Rui; TANG Zhi-yong; REN Hui-feng

    2004-01-01

    The contents of eight trace elements(Mn, Cr, Pb, As, Se, Zn, Cd, Hg) in raw coal, bottom ash and flyash were measured in a 220 t/h pulverized coal boiler. Factors affecting distribution of trace elements wereinvestigated, including fly ash diameter, furnace temperature, oxygen content and trace elements' characters. Onecoefficient of Meij was also improved to more directly show element enrichment in combustion products. Theseelements may be classified into three groups according to their distribution: Group 1: Hg, which is very volatile.Group 2: Pb, Zn, Cd, which are partially volatile. Group 3: Mn, which is hardly volatile. Se may be locatedbetween groups 1 and 2. Cr has properties of both group 1 and 3. In addition, the smaller diameter of fly ash, themore relative enrichment of trace elements( except Mn). The fly ash showed different adsorption mechanisms oftrace elements and the volatilization of trace elements rises with furnace temperature. Relative enrichments of traceelements(except Mn and Cr) in fly ash are larger than that in bottom ash. Low oxygen content can not alwaysimprove the volatilization of trace elements. Pb is easier to form chloride than Cd during coal combustion. Traceelements should be classified in accordance with factors.

  19. Comparison of the Profile and Composition of Volatiles in Coniferous Needles According to Extraction Methods.

    Science.gov (United States)

    Jun, Yonjin; Lee, Sang Mi; Ju, Hyun Kyoung; Lee, Hong Jin; Choi, Hyung-Kyoon; Jo, Gyeong Suk; Kim, Young-Suk

    2016-03-17

    The enantiomeric distribution and profile of volatiles in plants, which affect the biological and organoleptic properties, can be varied depending on extraction methods as well as their cultivars. The secondary volatile components of the needles of three conifer cultivars (Chamaecyparispisifera, Chamaecyparisobtusa, and Thujaorientalis) were compared. Furthermore, the effects of three different extraction methods--solid-phase microextraction (SPME), steam distillation (SD), and solvent extraction (SE)--on the composition and enantiomeric distribution of those volatiles were elucidated. Monoterpene hydrocarbons predominated in all samples, and the compositions of sesquiterpenes and diterpenes differed according to the cultivar. In particular, the yields of oxygenated monoterpenes and sesquiterpenes were greatest for SD, whereas those of sesquiterpenes and diterpenes were highest for SE. On the other hand, more monoterpenes with higher volatility could be obtained with SPME and SD than when using SE. In addition, the enantiomeric composition of nine chiral compounds found in three cultivars differed according to their chemotype. There were also some differences in the yielded oxygenated monoterpenes and sesquiterpene hydrocarbons, but not monoterpene hydrocarbons, according to the extraction method. These results demonstrate that the extraction methods used as well as the cultivars influence the measured volatile profiles and enantiomeric distribution of coniferous needle extracts.

  20. Identification and Quantification of Oxidoselina-1,3,7(11)-Trien-8-One and Cyanidin-3-Glucoside as One of the Major Volatile and Non-Volatile Low-Molecular-Weight Constituents in Pitanga Pulp.

    Science.gov (United States)

    Josino Soares, Denise; Pignitter, Marc; Ehrnhöfer-Ressler, Miriam Margit; Walker, Jessica; Montenegro Brasil, Isabella; Somoza, Veronika

    2015-01-01

    The pulp of pitanga (Eugenia uniflora L.) is used to prepare pitanga juice. However, there are no reports on the identification and quantification of the main constituents in pitanga pulp. The aim of this study was to identify and quantify the major volatile and non-volatile low-molecular-weight constituents of the pulp. Isolation of volatile compounds was performed by solvent-assisted flavor evaporation technique. Characterization of the main volatile and non-volatile constituents was performed by GC-MS, LC-MS and NMR spectroscopy. For quantitative measurements, the main volatile compound needed to be isolated from pitanga pulp to obtain a commercially not available reference standard. Cyanidin-3-glucoside was determined as one of the most abundant non-volatile pulp compound yielding 53.8% of the sum of the intensities of all ions detected by LC-MS. Quantification of cyanidin-3-glucoside in pitanga pulp resulted in a concentration of 344 ± 66.4 μg/mL corresponding to 688 ± 133 μg/g dried pulp and 530 ± 102 μg/g fruit. For the volatile fraction, oxidoselina-1,3,7(11)-trien-8-one was identified as the main volatile pulp constituent (27.7% of the sum of the intensities of all ions detected by GC-MS), reaching a concentration of 89.0 ± 16.9 μg/mL corresponding to 1.34 ± 0.25 μg/g fresh pulp and 1.03 ± 0.19 μg/g fruit. The results provide quantitative evidence for the occurrence of an anthocyanin and an oxygenated sesquiterpene as one of the major volatile and non-volatile low-molecular-weight compounds in pitanga pulp.

  1. Identification and Quantification of Oxidoselina-1,3,7(11)-Trien-8-One and Cyanidin-3-Glucoside as One of the Major Volatile and Non-Volatile Low-Molecular-Weight Constituents in Pitanga Pulp

    Science.gov (United States)

    Ehrnhöfer-Ressler, Miriam Margit; Walker, Jessica; Montenegro Brasil, Isabella; Somoza, Veronika

    2015-01-01

    The pulp of pitanga (Eugenia uniflora L.) is used to prepare pitanga juice. However, there are no reports on the identification and quantification of the main constituents in pitanga pulp. The aim of this study was to identify and quantify the major volatile and non-volatile low-molecular-weight constituents of the pulp. Isolation of volatile compounds was performed by solvent-assisted flavor evaporation technique. Characterization of the main volatile and non-volatile constituents was performed by GC-MS, LC-MS and NMR spectroscopy. For quantitative measurements, the main volatile compound needed to be isolated from pitanga pulp to obtain a commercially not available reference standard. Cyanidin-3-glucoside was determined as one of the most abundant non-volatile pulp compound yielding 53.8% of the sum of the intensities of all ions detected by LC-MS. Quantification of cyanidin-3-glucoside in pitanga pulp resulted in a concentration of 344 ± 66.4 μg/mL corresponding to 688 ± 133 μg/g dried pulp and 530 ± 102 μg/g fruit. For the volatile fraction, oxidoselina-1,3,7(11)-trien-8-one was identified as the main volatile pulp constituent (27.7% of the sum of the intensities of all ions detected by GC-MS), reaching a concentration of 89.0 ± 16.9 μg/mL corresponding to 1.34 ± 0.25 μg/g fresh pulp and 1.03 ± 0.19 μg/g fruit. The results provide quantitative evidence for the occurrence of an anthocyanin and an oxygenated sesquiterpene as one of the major volatile and non-volatile low-molecular-weight compounds in pitanga pulp. PMID:26394146

  2. Identification and Quantification of Oxidoselina-1,3,7(11-Trien-8-One and Cyanidin-3-Glucoside as One of the Major Volatile and Non-Volatile Low-Molecular-Weight Constituents in Pitanga Pulp.

    Directory of Open Access Journals (Sweden)

    Denise Josino Soares

    Full Text Available The pulp of pitanga (Eugenia uniflora L. is used to prepare pitanga juice. However, there are no reports on the identification and quantification of the main constituents in pitanga pulp. The aim of this study was to identify and quantify the major volatile and non-volatile low-molecular-weight constituents of the pulp. Isolation of volatile compounds was performed by solvent-assisted flavor evaporation technique. Characterization of the main volatile and non-volatile constituents was performed by GC-MS, LC-MS and NMR spectroscopy. For quantitative measurements, the main volatile compound needed to be isolated from pitanga pulp to obtain a commercially not available reference standard. Cyanidin-3-glucoside was determined as one of the most abundant non-volatile pulp compound yielding 53.8% of the sum of the intensities of all ions detected by LC-MS. Quantification of cyanidin-3-glucoside in pitanga pulp resulted in a concentration of 344 ± 66.4 μg/mL corresponding to 688 ± 133 μg/g dried pulp and 530 ± 102 μg/g fruit. For the volatile fraction, oxidoselina-1,3,7(11-trien-8-one was identified as the main volatile pulp constituent (27.7% of the sum of the intensities of all ions detected by GC-MS, reaching a concentration of 89.0 ± 16.9 μg/mL corresponding to 1.34 ± 0.25 μg/g fresh pulp and 1.03 ± 0.19 μg/g fruit. The results provide quantitative evidence for the occurrence of an anthocyanin and an oxygenated sesquiterpene as one of the major volatile and non-volatile low-molecular-weight compounds in pitanga pulp.

  3. Oxygen measurements to improve singlet oxygen dosimetry

    Science.gov (United States)

    Kim, Michele M.; Penjweini, Rozhin; Ong, Yi Hong; Finlay, Jarod C.; Zhu, Timothy C.

    2017-02-01

    Photodynamic therapy (PDT) involves interactions between the three main components of light fluence, photosensitizer concentration, and oxygenation. Currently, singlet oxygen explicit dosimetry (SOED) has focused on the first two of these components. The macroscopic model to calculate reacted singlet oxygen has previously involved a fixed initial ground state oxygen concentration. A phosphorescence-based oxygen probe was used to measure ground state oxygen concentration throughout treatments for mice bearing radioactively induced fibroscarcoma tumors. Photofrin-, BPD-, and HPPH-mediated PDT was performed on mice. Model-calculated oxygen and measured oxygen was compared to evaluate the macroscopic model as well as the photochemical parameters involved. Oxygen measurements at various depths were compared to calculated values. Furthermore, we explored the use of noninvasive diffuse correlation spectroscopy (DCS) to measure tumor blood flow changes in response to PDT to improve the model calculation of reacted singlet oxygen. Mice were monitored after treatment to see the effect of oxygenation on long-term recurrence-free survival as well as the efficacy of using reacted singlet oxygen as a predictive measure of outcome. Measurement of oxygenation during treatment helps to improve SOED as well as confirm the photochemical parameters involved in the macroscopic model. Use of DCS in predicting oxygenation changes was also investigated.

  4. Origin of Volatiles in Earth: Indigenous Versus Exogenous Sources Based on Highly Siderophile, Volatile Siderophile, and Light Volatile Elements

    Science.gov (United States)

    Righter, K.; Danielson, L.; Pando, K. M.; Marin, N.; Nickodem, K.

    2015-01-01

    Origin of Earth's volatiles has traditionally been ascribed to late accretion of material after major differentiation events - chondrites, comets, ice or other exogenous sources. A competing theory is that the Earth accreted its volatiles as it was built, thus water and other building blocks were present early and during differentiation and core formation (indigenous). Here we discuss geochemical evidence from three groups of elements that suggests Earth's volatiles were acquired during accretion and did not require additional sources after differentiation.

  5. Chemical composition of volatile oils from leaves of Nectandra megapotamica Spreng. (Lauraceae)

    Energy Technology Data Exchange (ETDEWEB)

    Romoff, Paulete; Ferreira, Marcelo J.P., E-mail: romoff@mackenzie.b [Universidade Presbiteriana Mackenzie, Sao Paulo, SP (Brazil). Centro de Ciencias e Humanidades; Padilla, Ricardo; Toyama, Daniela O.; Favero, Oriana A. [Universidade Presbiteriana Mackenzie, Sao Paulo, SP (Brazil). Centro de Ciencias Biologicas e da Saude; Lago, Joao Henrique G. [Universidade Federal de Sao Paulo (UNIFESP), Diadema, SP (Brazil). Dept. de Ciencias Exatas e da Terra

    2010-07-01

    The volatile oils from Nectandra megapotamica Spreng. leaves, collected in February and August of 2007 and at 7:00 and 12:00 h (samples A - D), were extracted by hydrodistillation and the chemical composition was analyzed by GC-FID and GC/MS. A total of nineteen compounds were identified with predominance of oxygenated sesquiterpenes, among them, a-bisabolol, was the main constituent (62.3-69.4 %). After chromatographic separation procedures, this compound was purified from crude oil and its structure was confirmed by analysis of NMR data. This paper describes for the first time the composition of the leaves volatile oil from N. megapotamica. (author)

  6. Chemical mass balance of 300 °C non-volatile particles at the tropospheric research site Melpitz, Germany

    Science.gov (United States)

    Poulain, L.; Birmili, W.; Canonaco, F.; Crippa, M.; Wu, Z. J.; Nordmann, S.; Spindler, G.; Prévôt, A. S. H.; Wiedensohler, A.; Herrmann, H.

    2014-09-01

    In the fine-particle mode (aerodynamic diameter MAAP), and an aerosol mass spectrometer (AMS). The data were collected during two atmospheric field experiments in May-June 2008 as well as February-March 2009. As a basic result, we detected average non-volatile particle-volume fractions of 11 ± 3% (2008) and 17 ± 8% (2009). In both periods, BC was in close linear correlation with the non-volatile fraction, but not sufficient to quantitatively explain the non-volatile particle mass concentration. Based on the assumption that BC is not altered by the heating process, the non-volatile particle mass fraction could be explained by the sum of black carbon (47% in summer, 59% in winter) and a non-volatile organic contribution estimated as part of the low-volatility oxygenated organic aerosol (LV-OOA) (53% in summer, 41% in winter); the latter was identified from AMS data by factor analysis. Our results suggest that LV-OOA was more volatile in summer (May-June 2008) than in winter (February-March 2009) which was linked to a difference in oxidation levels (lower in summer). Although carbonaceous compounds dominated the sub-μm non-volatile particle mass fraction most of the time, a cross-sensitivity to partially volatile aerosol particles of maritime origin could be seen. These marine particles could be distinguished, however from the carbonaceous particles by a characteristic particle volume-size distribution. The paper discusses the uncertainty of the volatility measurements and outlines the possible merits of volatility analysis as part of continuous atmospheric aerosol measurements.

  7. Measurement of non-volatile particle number size distribution

    Science.gov (United States)

    Gkatzelis, G. I.; Papanastasiou, D. K.; Florou, K.; Kaltsonoudis, C.; Louvaris, E.; Pandis, S. N.

    2015-06-01

    An experimental methodology was developed to measure the non-volatile particle number concentration using a thermodenuder (TD). The TD was coupled with a high-resolution time-of-flight aerosol mass spectrometer, measuring the chemical composition and mass size distribution of the submicrometer aerosol and a scanning mobility particle sizer (SMPS) that provided the number size distribution of the aerosol in the range from 10 to 500 nm. The method was evaluated with a set of smog chamber experiments and achieved almost complete evaporation (> 98 %) of secondary organic as well as freshly nucleated particles, using a TD temperature of 400 °C and a centerline residence time of 15 s. This experimental approach was applied in a winter field campaign in Athens and provided a direct measurement of number concentration and size distribution for particles emitted from major pollution sources. During periods in which the contribution of biomass burning sources was dominant, more than 80 % of particle number concentration remained after passing through the thermodenuder, suggesting that nearly all biomass burning particles had a non-volatile core. These remaining particles consisted mostly of black carbon (60 % mass contribution) and organic aerosol, OA (40 %). Organics that had not evaporated through the TD were mostly biomass burning OA (BBOA) and oxygenated OA (OOA) as determined from AMS source apportionment analysis. For periods during which traffic contribution was dominant 50-60 % of the particles had a non-volatile core while the rest evaporated at 400 °C. The remaining particle mass consisted mostly of black carbon (BC) with an 80 % contribution, while OA was responsible for another 15-20 %. Organics were mostly hydrocarbon-like OA (HOA) and OOA. These results suggest that even at 400 °C some fraction of the OA does not evaporate from particles emitted from common combustion processes, such as biomass burning and car engines, indicating that a fraction of this type

  8. Volatile accretion history of the Earth.

    Science.gov (United States)

    Wood, B J; Halliday, A N; Rehkämper, M

    2010-10-28

    It has long been thought that the Earth had a protracted and complex history of volatile accretion and loss. Albarède paints a different picture, proposing that the Earth first formed as a dry planet which, like the Moon, was devoid of volatile constituents. He suggests that the Earth's complement of volatile elements was only established later, by the addition of a small veneer of volatile-rich material at ∼100 Myr (here and elsewhere, ages are relative to the origin of the Solar System). Here we argue that the Earth's mass balance of moderately volatile elements is inconsistent with Albarède's hypothesis but is well explained by the standard model of accretion from partially volatile-depleted material, accompanied by core formation.

  9. Volatile communication in plant-aphid interactions.

    Science.gov (United States)

    de Vos, Martin; Jander, Georg

    2010-08-01

    Volatile communication plays an important role in mediating the interactions between plants, aphids, and other organisms in the environment. In response to aphid infestation, many plants initiate indirect defenses through the release of volatiles that attract ladybugs, parasitoid wasps, and other aphid-consuming predators. Aphid-induced volatile release in the model plant Arabidopsis thaliana requires the jasmonate signaling pathway. Volatile release is also induced by infection with aphid-transmitted viruses. Consistent with mathematical models of optimal transmission, viruses that are acquired rapidly by aphids induce volatile release to attract migratory aphids, but discourage long-term aphid feeding. Although the ecology of these interactions is well-studied, further research is needed to identify the molecular basis of aphid-induced and virus-induced changes in plant volatile release.

  10. Milk Price Volatility and its Determinants

    OpenAIRE

    Dong, Fengxia; Du, Xiaodong; Gould, Brian W.

    2011-01-01

    The classified pricing of fluid milk under the Federal Milk Marketing Orders (FMMO) system combined with the cash settlement feature of Class IIII milk futures contracts generate a unique volatility pattern of these futures markets in the sense that the volatility gradually decreases as the USDA price announcement dates approaching in the month. Focusing on the evolution of volatility in Class III milk futures market, this study quantifies the relative importance of a set of factors driving m...

  11. DOES VOLATILITY RESPOND ASYMMETRIC TO PAST SHOCKS?

    OpenAIRE

    Claudiu Botoc

    2014-01-01

    The main aim of the paper is to examine if the stock market volatility exhibits asymmetric or an asymmetric response to past shocks, for certain CEE countries (Romania,Hungary, Bulgaria, Poland) over the period May 2004 - September 2014. For the stock marketsfrom East Europe the results are in line with the symmetric volatility, i.e. volatility is similaraffected by both positive and negative returns with the same magnitude. For the stock marketsfrom Central Europe the results are consistent ...

  12. The Determinants of Public Deficit Volatility

    OpenAIRE

    2009-01-01

    This paper empirically analyzes the political, institutional and economic sources of public deficit volatility. Using the system-GMM estimator for linear dynamic panel data models and a sample of 125 countries analyzed from 1980 to 2006, we show that higher public deficit volatility is typically associated with higher levels of political instability and less democracy. In addition, public deficit volatility tends to be magnified for small countries, in the outcome of hyper-inflation episodes ...

  13. Exchange Rate Volatility in BRICS Countries

    OpenAIRE

    2012-01-01

    This paper measures the impact of bilateral exchange rates, the world agricultural GDP and third-country exchange rate volatilities (Yen/USD and Euro/USD) on the BRICS agricultural exports using a vector autoregressive (VAR) model. Two measures of volatility are used: the standard deviation and the coefficient of variation of the rates of change of the real exchange rates. We found that most variables are integrated of order two except the third-country exchange rate volatilities which are st...

  14. Volatile halogenated hydrocarbons in foods

    Energy Technology Data Exchange (ETDEWEB)

    Miyahara, Makoto; Toyoda, Masatake; Saito, Yukio [National Institute of Health Services, Tokyo (Japan)] [and others

    1995-02-01

    Volatile halogenated organic compounds were determined in foods. Statistical treatment of the data for 13 sampled from 20 families living in suburban Tokyo (Saitama prefecture) indicated that the foods were contaminated by water pollution and/or substances introduced by the process of food production. Butter and margarine were contaminated by chlorinated ethylene, ethane, and related compounds released by dry cleaning and other operations. Soybean sprouts and tofu (soybean curd) contained chloroform and related trihalomethanes absorbed during the production process. 27 refs., 6 figs., 5 tabs.

  15. Volatile Constituents of Zhumaria Majdae

    Directory of Open Access Journals (Sweden)

    Yazdanparst

    1993-07-01

    Full Text Available Capillary gas chromatography mass spectrometry (GC- MS analyses of a sample of essential oil of zhumaria Linalool ned by simple water distillation of the pulverized air - dired leaves and flowers of the plant indicated that Linalool and comphor are the two major constituents of the volatile oil. Sylvestrene , y -terpinene, a- Pinene, b - carene, camphene, and Epiborneol constitute the other main components of the essential oil. The GC - MS chromatogram indicated the presence of more than fifty - components in the oil, most of them were present in trace amounts. In this study, the chemical structures of twenty of these consti tuents were elucidated using GC - MS analysis.

  16. The Amazonian Floodplains, an ecotype with challenging questions on volatile organic compound (VOC) emissions

    Science.gov (United States)

    Kesselmeier, J.

    2012-12-01

    Volatile organic compound (VOC) emissions are affected by a variety of biotic and abiotic factors such as light intensity, temperature, CO2 and drought. Another factor usually overlooked but very important for the tropical rainforest in Amazonia is regular flooding. According to recent estimates, the total Amazonian floodplain area easily ranges up to 700,000 km^2, including whitewater river floodplains (várzea) blackwater regions (igapó) and further clearwater regions. Regarding the total Amazonian wetlands the area sums up to more than 2.000.000 km^2, i.e. 30% of Amazonia. To survive the flooding periods causing anoxic conditions for the root system of up to several months, vegetation has developed several morphological, anatomical and physiological strategies. One is to switch over the root metabolism to fermentation, thus producing ethanol as one of the main products. Ethanol is a toxic metabolite which is transported into the leaves by the transpiration stream. From there it can either be directly emitted into the atmosphere, or can be re-metabolized to acetaldehyde and/or acetate. All of these compounds are volatile enough to be partly released into the atmosphere. We observed emissions of ethanol, acetaldehyde and acetic acid under root anoxia. Furthermore, plant stress induced by flooding also affected leaf primary physiological processes as well as other VOC emissions such as the release of isoprenoids and other volatiles. For example, Hevea spruceana could be identified as a monoterpene emitting tree species behaving differently upon anoxia depending on the origin, with increasing emissions of the species from igapó and decreasing with the corresponding species from várzea. Contrasting such short term inundations, studies of VOC emissions under long term conditions (2-3 months) did not confirm the ethanol/acetaldehyde emissions, whereas emissions of other VOC species decreased considerably. These results demonstrate that the transfer of our knowledge

  17. Mars Accreted a Volatile Element-Depleted Late Veneer Indicating Early Delivery of Martian Volatiles

    Science.gov (United States)

    Becker, H.; Wang, Z.

    2016-08-01

    Chalcophile elements in SNC meteorites are used to constrain abundances in the Martian mantle. Strong depletion of Te relative to highly siderophile elements suggests a volatile element-depleted late veneer, requiring that volatiles arrived earlier.

  18. Source facies of the Paleozoic petroleum systems in the Tabei uplift, Tarim Basin, NW China: implications from aryl isoprenoids in crude oils

    Energy Technology Data Exchange (ETDEWEB)

    Yongge Sun; Shiping Xu; Hong Lu; Pingxia Cuai [Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou (China). SKLOG

    2003-04-01

    Aryl isoprenoids have been detected for the first time in crude oils from Paleozoic petroleum systems in the Tabei uplift, Tarim Basin, northwestern China. The principal compounds possess the 1-alkyl-2,3,6-trimethyl substitution pattern characteristic of diaromatic carotenoids found in the Chlorobiaceae family of photosynthetic sulfur bacteria, with a predominance of C{sub 13} - C{sub 23} homologues in these samples. Flash pyrolysates of the asphaltene fractions isolated from crude oils show an unusual abundance of 1,2,3,4-tetramethylbenzene, an indicator for a significant contribution of diaromatic carotenoids to the source kerogen of these oils. The wide distribution of these compounds in crude oils reveals that penetration of the photic zone by sulfidic waters during deposition enabled prolific growth of photosynthetic green sulphur bacteria (Chlorobiaceae). This suggests that the source rocks for the Paleozoic petroleum systems in the Tabei uplift were likely deposited under euxinic conditions with sulfate and sulfide-rich water bodies, which doesn't support previously published conclusions of a Middle-Upper Ordovician source that marks the slope facies at the margins of structural uplifts. (author)

  19. MRI study of the cuprizone-induced mouse model of multiple sclerosis: demyelination is not found after co-treatment with polyprenols (long-chain isoprenoid alcohols)

    Science.gov (United States)

    Khodanovich, M.; Glazacheva, V.; Pan, E.; Akulov, A.; Krutenkova, E.; Trusov, V.; Yarnykh, V.

    2016-02-01

    Multiple sclerosis is a neurological disorder with poorly understood pathogenic mechanisms and a lack of effective therapies. Therefore, the search for new MS treatments remains very important. This study was performed on a commonly used cuprizone animal model of multiple sclerosis. It evaluated the effect of a plant-derived substance called Ropren® (containing approximately 95% polyprenols or long-chain isoprenoid alcohols) on cuprizone- induced demyelination. The study was performed on 27 eight-week old male CD-1 mice. To induce demyelination mice were fed 0.5% cuprizone in the standard diet for 10 weeks. Ropren® was administered in one daily intraperitoneal injection (12mg/kg), beginning on the 6th week of the experiment. On the 11th week, the corpus callosum in the brain was evaluated in all animals using magnetic resonance imaging with an 11.7 T animal scanner using T2- weighted sequence. Cuprizone treatment successfully induced the model of demyelination with a significant decrease in the size of the corpus callosum compared with the control group (p<0.01). Mice treated with both cuprizone and Ropren® did not exhibit demyelination in the corpus callosum (p<0.01). This shows the positive effect of polyprenols on cuprizone-induced demyelination in mice.

  20. Mutations in Escherichia coli aceE and ribB genes allow survival of strains defective in the first step of the isoprenoid biosynthesis pathway.

    Directory of Open Access Journals (Sweden)

    Jordi Perez-Gil

    Full Text Available A functional 2-C-methyl-D-erythritol 4-phosphate (MEP pathway is required for isoprenoid biosynthesis and hence survival in Escherichia coli and most other bacteria. In the first two steps of the pathway, MEP is produced from the central metabolic intermediates pyruvate and glyceraldehyde 3-phosphate via 1-deoxy-D-xylulose 5-phosphate (DXP by the activity of the enzymes DXP synthase (DXS and DXP reductoisomerase (DXR. Because the MEP pathway is absent from humans, it was proposed as a promising new target to develop new antibiotics. However, the lethal phenotype caused by the deletion of DXS or DXR was found to be suppressed with a relatively high efficiency by unidentified mutations. Here we report that several mutations in the unrelated genes aceE and ribB rescue growth of DXS-defective mutants because the encoded enzymes allowed the production of sufficient DXP in vivo. Together, this work unveils the diversity of mechanisms that can evolve in bacteria to circumvent a blockage of the first step of the MEP pathway.

  1. Mutations in Escherichia coli aceE and ribB genes allow survival of strains defective in the first step of the isoprenoid biosynthesis pathway.

    Science.gov (United States)

    Perez-Gil, Jordi; Uros, Eva Maria; Sauret-Güeto, Susanna; Lois, L Maria; Kirby, James; Nishimoto, Minobu; Baidoo, Edward E K; Keasling, Jay D; Boronat, Albert; Rodriguez-Concepcion, Manuel

    2012-01-01

    A functional 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway is required for isoprenoid biosynthesis and hence survival in Escherichia coli and most other bacteria. In the first two steps of the pathway, MEP is produced from the central metabolic intermediates pyruvate and glyceraldehyde 3-phosphate via 1-deoxy-D-xylulose 5-phosphate (DXP) by the activity of the enzymes DXP synthase (DXS) and DXP reductoisomerase (DXR). Because the MEP pathway is absent from humans, it was proposed as a promising new target to develop new antibiotics. However, the lethal phenotype caused by the deletion of DXS or DXR was found to be suppressed with a relatively high efficiency by unidentified mutations. Here we report that several mutations in the unrelated genes aceE and ribB rescue growth of DXS-defective mutants because the encoded enzymes allowed the production of sufficient DXP in vivo. Together, this work unveils the diversity of mechanisms that can evolve in bacteria to circumvent a blockage of the first step of the MEP pathway.

  2. [Solidification of volatile oil with graphene oxide].

    Science.gov (United States)

    Yan, Hong-Mei; Jia, Xiao-Bin; Zhang, Zhen-Hai; Sun, E; Xu, Yi-Hao

    2015-02-01

    To evaluate the properties of solidifying volatile oil with graphene oxide, clove oil and zedoary turmeric oil were solidified by graphene oxide. The amount of graphene oxide was optimized with the eugenol yield and curcumol yield as criteria. Curing powder was characterized by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The effects of graphene oxide on dissolution in vitro and thermal stability of active components were studied. The optimum solidification ratio of graphene oxide to volatile oil was 1:1. Dissolution rate of active components had rare influence while their thermal stability improved after volatile oil was solidified. Solidifying herbal volatile oil with graphene oxide deserves further study.

  3. CAM Stochastic Volatility Model for Option Pricing

    Directory of Open Access Journals (Sweden)

    Wanwan Huang

    2016-01-01

    Full Text Available The coupled additive and multiplicative (CAM noises model is a stochastic volatility model for derivative pricing. Unlike the other stochastic volatility models in the literature, the CAM model uses two Brownian motions, one multiplicative and one additive, to model the volatility process. We provide empirical evidence that suggests a nontrivial relationship between the kurtosis and skewness of asset prices and that the CAM model is able to capture this relationship, whereas the traditional stochastic volatility models cannot. We introduce a control variate method and Monte Carlo estimators for some of the sensitivities (Greeks of the model. We also derive an approximation for the characteristic function of the model.

  4. Assessing Relative Volatility/Intermittency/Energy Dissipation

    DEFF Research Database (Denmark)

    Barndorff-Nielsen, Ole E.; Pakkanen, Mikko; Schmiegel, Jürgen

    We introduce the notion of relative volatility/intermittency and demonstrate how relative volatility statistics can be used to estimate consistently the temporal variation of volatility/intermittency even when the data of interest are generated by a non-semimartingale, or a Brownian semistationary...... process in particular. While this estimation method is motivated by the assessment of relative energy dissipation in empirical data of turbulence, we apply it also to energy price data. Moreover, we develop a probabilistic asymptotic theory for relative power variations of Brownian semistationary...... processes and Ito semimartingales and discuss how it can be used for inference on relative volatility/intermittency....

  5. Ecosystem-scale volatile organic compound fluxes during an extreme drought in a broadleaf temperate forest of the Missouri Ozarks (central USA)

    Energy Technology Data Exchange (ETDEWEB)

    Seco, Roger [Univ. of California, Irvine, CA (United States); Karl, Thomas [Univ. of Innsbruck (Austria); Guenther, Alex B. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Washington State Univ., Pullman, WA (United States); Hosman, Kevin P. [Univ. of Missouri, Columbia, MO (United States); Pallardy, Stephen G. [Univ. of Missouri, Columbia, MO (United States); Gu, Lianhong [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Geron, Chris [U.S. Environmental Protection Agency, Research Triangle Park, NC (United States); Harley, Peter [National Center for Atmospheric Research, Boulder, CO (United States); Kim, Saewung [Univ. of California, Irvine, CA (United States)

    2015-07-07

    Considerable amounts and varieties of biogenic volatile organic compounds (BVOCs) are exchanged between vegeta-tion and the surrounding air. These BVOCs play key ecological and atmospheric roles that must be adequately repre-sented for accurately modeling the coupled biosphere–atmosphere–climate earth system. One key uncertainty in existing models is the response of BVOC fluxes to an important global change process: drought. We describe the diur-nal and seasonal variation in isoprene, monoterpene, and methanol fluxes from a temperate forest ecosystem before, during, and after an extreme 2012 drought event in the Ozark region of the central USA. BVOC fluxes were domi-nated by isoprene, which attained high emission rates of up to 35.4 mg m-2h-1 at midday. Methanol fluxes were characterized by net deposition in the morning, changing to a net emission flux through the rest of the daylight hours. Net flux of CO2 reached its seasonal maximum approximately a month earlier than isoprenoid fluxes, which high-lights the differential response of photosynthesis and isoprenoid emissions to progressing drought conditions. Never-theless, both processes were strongly suppressed under extreme drought, although isoprene fluxes remained relatively high compared to reported fluxes from other ecosystems. Methanol exchange was less affected by drought throughout the season, conflrming the complex processes driving biogenic methanol fluxes. The fraction of daytime (7–17 h) assimilated carbon released back to the atmosphere combining the three BVOCs measured was 2% of gross primary productivity (GPP) and 4.9% of net ecosystem exchange (NEE) on average for our whole measurement cam-paign, while exceeding 5% of GPP and 10% of NEE just before the strongest drought phase. The MEGANv2.1 model correctly predicted diurnal variations in fluxes driven mainly by light and temperature, although further research is needed to address model BVOC fluxes

  6. Temperature-induced volatility of molecular markers in ambient airborne particulate matter

    Directory of Open Access Journals (Sweden)

    C. R. Ruehl

    2010-08-01

    Full Text Available Molecular markers are organic compounds used to represent known sources of particulate matter (PM in statistical source apportionment studies. The utility of molecular markers depends on, among other things, their ability to represent PM volatility under realistic atmospheric conditions. We measured the particle-phase concentrations and temperature-induced volatility of commonly-used molecular markers in California's heavily polluted San Joaqin Valley. Concentrations of elemental carbon, organic carbon, levoglucosan, and polycyclic aromatic hydrocarbons were not reduced by mild (~10 K heating. In contrast, both hopane/sterane and n-alkane concentrations were reduced, especially during the summer sampling events at the urban site. These results suggest that hopanes and steranes have effective saturation concentrations ~1 μg m−3, and therefore can be considered semi-volatile in realistic ambient conditions. The volatility behavior of n-alkanes during the urban summer is consistent with that predicted for absorption by suberic acid (a C8 diacid using a group contribution modelling method. Observations can also be matched by an absorbent whose composition is based on recently-obtained high-resolution aerosol mass spectrometer factors (approximately 33% "hydrocarbon-like" and 67% oxygenated organic aerosol. The diminished volatility of the n-alkanes, hopanes, and steranes during rural and/or winter experiments could be explained by a more oxygenated absorbing phase along with a non-absorptive partitioning mechanism, such as adsorption to soot. This suggests that the temperature-induced volatility of large hydrocarbons in PM is most important if a relatively non-polar absorbing organic phase exists. While the activity coefficients of most organic aerosol compounds may be close to unity, the assumption of ideality for large hydrocarbons (e.g., hopanes may result in large errors in partitioning calculations.

  7. Belief biases and volatility of assets

    Science.gov (United States)

    Lei-Sun, Wen-Zou, Hui

    2014-10-01

    Based on an overlapping generation model, this paper introduces the noise traders with belief biases and rational traders. With an equilibrium analysis, this paper examines the volatility of risky asset. The results show that the belief biases, the probability of economy state, and the domain capability are all the factors that have effects on the volatility of the market.

  8. Explaining output volatility: The case of taxation

    DEFF Research Database (Denmark)

    Posch, Olaf

    empirical link between e ective tax rates and output volatility, with some evidence of a cointegrating relationship. In accordance with theory, taxes on labor income and corporate income empirically are found to be negatively related to volatility of macro aggregates whereas the capital tax ratio has...

  9. Effects of Idiosyncratic Volatility in Asset Pricing

    Directory of Open Access Journals (Sweden)

    André Luís Leite

    2016-04-01

    Full Text Available This paper aims to evaluate the effects of the aggregate market volatility components - average volatility and average correlation - on the pricing of portfolios sorted by idiosyncratic volatility, using Brazilian data. The study investigates whether portfolios with high and low idiosyncratic volatility - in relation to the Fama and French model (1996 - have different exposures to innovations in average market volatility, and consequently, different expectations for return. The results are in line with those found for US data, although they portray the Brazilian reality. Decomposition of volatility allows the average volatility component, without the disturbance generated by the average correlation component, to better price the effects of a worsening or an improvement in the investment environment. This result is also identical to that found for US data. Average variance should thus command a risk premium. For US data, this premium is negative. According to Chen and Petkova (2012, the main reason for this negative sign is the high level of investment in research and development recorded by companies with high idiosyncratic volatility. As in Brazil this type of investment is significantly lower than in the US, it was expected that a result with the opposite sign would be found, which is in fact what occurred.

  10. Some recent developments in stochastic volatility modelling

    DEFF Research Database (Denmark)

    Barndorff-Nielsen, Ole Eiler; Nicolato, Elisa; Shephard, N.

    2002-01-01

    This paper reviews and puts in context some of our recent work on stochastic volatility (SV) modelling for financial economics. Here our main focus is on: (i) the relationship between subordination and SV, (ii) OU based volatility models, (iii) exact option pricing, (iv) realized power variation...

  11. Volatility Determination in an Ambit Process Setting

    DEFF Research Database (Denmark)

    Barndorff-Nielsen, Ole; Graversen, Svend-Erik

    The probability limit behaviour of normalised quadratic variation is studied for a simple tempo-spatial ambit process, with particular regard to the question of volatility memorylessness.......The probability limit behaviour of normalised quadratic variation is studied for a simple tempo-spatial ambit process, with particular regard to the question of volatility memorylessness....

  12. Analyzing volatile compounds in dairy products

    Science.gov (United States)

    Volatile compounds give the first indication of the flavor in a dairy product. Volatiles are isolated from the sample matrix and then analyzed by chromatography, sensory methods, or an electronic nose. Isolation may be performed by solvent extraction or headspace analysis, and gas chromatography i...

  13. Stock market volatility and macroeconomic uncertainty

    NARCIS (Netherlands)

    Arnold, I.J.M.; Vrugt, E.B.

    2006-01-01

    This paper provides empirical evidence on the link between stock market volatility and macroeconomic uncertainty. We show that US stock market volatility is significantly related to the dispersion in economic forecasts from SPF survey participants over the period from 1969 to 1996. This link is much

  14. Stock market volatility and macroeconomic uncertainty

    NARCIS (Netherlands)

    Arnold, I.J.M.; Vrugt, E.B.

    2006-01-01

    This paper provides empirical evidence on the link between stock market volatility and macroeconomic uncertainty. We show that US stock market volatility is significantly related to the dispersion in economic forecasts from SPF survey participants over the period from 1969 to 1996. This link is much

  15. Fundamental uncertainty and stock market volatility

    NARCIS (Netherlands)

    Arnold, I.J.M.; Vrugt, E.B.

    2008-01-01

    We provide empirical evidence on the link between stock market volatility and macroeconomic uncertainty. We show that US stock market volatility is significantly related to the dispersion in economic forecasts from participants in the Survey of Professional Forecasters over the period 1969 to 1996.

  16. Current status of fluoride volatility method development

    Energy Technology Data Exchange (ETDEWEB)

    Uhlir, J.; Marecek, M.; Skarohlid, J. [UJV - Nuclear Research Institute, Research Centre Rez, CZ-250 68 Husinec - Rez 130 (Czech Republic)

    2013-07-01

    The Fluoride Volatility Method is based on a separation process, which comes out from the specific property of uranium, neptunium and plutonium to form volatile hexafluorides whereas most of fission products (mainly lanthanides) and higher transplutonium elements (americium, curium) present in irradiated fuel form nonvolatile tri-fluorides. Fluoride Volatility Method itself is based on direct fluorination of the spent fuel, but before the fluorination step, the removal of cladding material and subsequent transformation of the fuel into a powdered form with a suitable grain size have to be done. The fluorination is made with fluorine gas in a flame fluorination reactor, where the volatile fluorides (mostly UF{sub 6}) are separated from the non-volatile ones (trivalent minor actinides and majority of fission products). The subsequent operations necessary for partitioning of volatile fluorides are the condensation and evaporation of volatile fluorides, the thermal decomposition of PuF{sub 6} and the finally distillation and sorption used for the purification of uranium product. The Fluoride Volatility Method is considered to be a promising advanced pyrochemical reprocessing technology, which can mainly be used for the reprocessing of oxide spent fuels coming from future GEN IV fast reactors.

  17. Effect of land-use change and management on biogenic volatile organic compound emissions--selecting climate-smart cultivars.

    Science.gov (United States)

    Rosenkranz, Maaria; Pugh, Thomas A M; Schnitzler, Jörg-Peter; Arneth, Almut

    2015-09-01

    Land-use change (LUC) has fundamentally altered the form and function of the terrestrial biosphere. Increasing human population, the drive for higher living standards and the potential challenges of mitigating and adapting to global environmental change mean that further changes in LUC are unavoidable. LUC has direct consequences on climate not only via emissions of greenhouse gases and changing the surface energy balance but also by affecting the emission of biogenic volatile organic compounds (BVOCs). Isoprenoids, which dominate global BVOC emissions, are highly reactive and strongly modify atmospheric composition. The effects of LUC on BVOC emissions and related atmospheric chemistry have been largely ignored so far. However, compared with natural ecosystems, most tree species used in bioenergy plantations are strong BVOC emitters, whereas intensively cultivated crops typically emit less BVOCs. Here, we summarize the current knowledge on LUC-driven BVOC emissions and how these might affect atmospheric composition and climate. We further discuss land management and plant-breeding strategies, which could be taken to move towards climate-friendly BVOC emissions while simultaneously maintaining or improving key ecosystem functions such as crop yield under a changing environment.

  18. Price volatility in wind dominant electricity markets

    DEFF Research Database (Denmark)

    Farashbashi-Astaneh, Seyed-Mostafa; Chen, Zhe

    2013-01-01

    High penetration of intermittent renewable energy sources causes price volatility in future electricity markets. This is specially the case in European countries that plan high penetration levels. This highlights the necessity for revising market regulations and mechanisms in accordance to genera......High penetration of intermittent renewable energy sources causes price volatility in future electricity markets. This is specially the case in European countries that plan high penetration levels. This highlights the necessity for revising market regulations and mechanisms in accordance...... electricity markets. High price volatility is unappreciated because it imposes high financial risk levels to both electricity consumers and producers. Additionally high price variations impede tracking price signals by consumers in future smart grid and jeopardize implementation of demand response concepts....... The main contribution of this paper is to quantify volatility patterns of electricity price, as penetration level of wind power increases. Results explain a direct relationship between wind penetration and electricity price volatility in a quantitative manner....

  19. Atomic Oxygen Interactions With Silicone Contamination on Spacecraft in Low Earth Orbit Studied

    Science.gov (United States)

    Banks, Bruce A.

    2001-01-01

    Silicones have been widely used on spacecraft as potting compounds, adhesives, seals, gaskets, hydrophobic surfaces, and atomic oxygen protective coatings. Contamination of optical and thermal control surfaces on spacecraft in low Earth orbit (LEO) has been an ever-present problem as a result of the interaction of atomic oxygen with volatile species from silicones and hydrocarbons onboard spacecraft. These interactions can deposit a contaminant that is a risk to spacecraft performance because it can form an optically absorbing film on the surfaces of Sun sensors, star trackers, or optical components or can increase the solar absorptance of thermal control surfaces. The transmittance, absorptance, and reflectance of such contaminant films seem to vary widely from very transparent SiOx films to much more absorbing SiOx-based films that contain hydrocarbons. At the NASA Glenn Research Center, silicone contamination that was oxidized by atomic oxygen has been examined from LEO spacecraft (including the Long Duration Exposure Facility and the Mir space station solar arrays) and from ground laboratory LEO simulations. The findings resulted in the development of predictive models that may help explain the underlying issues and effects. Atomic oxygen interactions with silicone volatiles and mixtures of silicone and hydrocarbon volatiles produce glassy SiOx-based contaminant coatings. The addition of hydrocarbon volatiles in the presence of silicone volatiles appears to cause much more absorbing (and consequently less transmitting) contaminant films than when no hydrocarbon volatiles are present. On the basis of the LDEF and Mir results, conditions of high atomic oxygen flux relative to low contaminant flux appear to result in more transparent contaminant films than do conditions of low atomic oxygen flux with high contaminant flux. Modeling predictions indicate that the deposition of contaminant films early in a LEO flight should depend much more on atomic oxygen flux than

  20. Volatility smile as relativistic effect

    Science.gov (United States)

    Kakushadze, Zura

    2017-06-01

    We give an explicit formula for the probability distribution based on a relativistic extension of Brownian motion. The distribution (1) is properly normalized and (2) obeys the tower law (semigroup property), so we can construct martingales and self-financing hedging strategies and price claims (options). This model is a 1-constant-parameter extension of the Black-Scholes-Merton model. The new parameter is the analog of the speed of light in Special Relativity. However, in the financial context there is no ;speed limit; and the new parameter has the meaning of a characteristic diffusion speed at which relativistic effects become important and lead to a much softer asymptotic behavior, i.e., fat tails, giving rise to volatility smiles. We argue that a nonlocal stochastic description of such (Lévy) processes is inadequate and discuss a local description from physics. The presentation is intended to be pedagogical.

  1. Clustered volatility in multiagent dynamics

    CERN Document Server

    Youssefmir, M; Youssefmir, Michael; Huberman, Bernardo

    1995-01-01

    Large distributed multiagent systems are characterized by vast numbers of agents trying to gain access to limited resources in an unpredictable environment. Agents in these system continuously switch strategies in order to opportunistically find improvements in their utilities. We have analyzed the fluctuations around equilibrium that arise from strategy switching and discovered the existence of a new phenomenon. It consists of the appearance of sudden bursts of activity that punctuate the fixed point, and is due to an effective random walk consistent with overall stability. This clustered volatility is followed by relaxation to the fixed point but with different strategy mixes from the previous one. This phenomenon is quite general for systems in which agents explore strategies in search of local improvements.

  2. Forecasting Exchange Rate Volatility in the Presence of Jumps

    DEFF Research Database (Denmark)

    Busch, Thomas; Christensen, Bent Jesper; Nielsen, Morten Ørregaard

    of exchange rate futures options, allowingcalculation of option implied volatility. We find that implied volatility is an informationallyefficient but biased forecast of future realized exchange rate volatility. Furthermore,we show that log-normality is an even better distributional approximation...... for impliedvolatility than for realized volatility in this market. Finally, we show that the jump componentof future realized exchange rate volatility is to some extent predictable, and thatoption implied volatility is the dominant forecast of the future jump component....

  3. IN SITU MEASUREMENTS OF C2-C10 VOLATILE ORGANIC COMPOUNDS ABOVE A SIERRA NEVADA PONDEROSA PINE PLANTATION

    Science.gov (United States)

    A fully automated GC-FID system was designed and built to measure ambient concentrations of C2-C10 volatile organic compounds, including many oxygenated compounds, without using liquid cryogen. It was deployed at Blodgett Forest Research Station in Georgetown, CA USA, 38 deg 53' ...

  4. Diel cycles of isoprenoids in the emissions of Norway spruce, four Scots pine chemotypes, and in Boreal forest ambient air during HUMPPA-COPEC-2010

    Directory of Open Access Journals (Sweden)

    N. Yassaa

    2012-08-01

    Full Text Available Branch enclosure based emission rates of monoterpenes and sesquiterpenes from four Scots pines (Pinus sylvestris and one Norway spruce (Picea abies, as well as the ambient mixing ratios of monoterpenes were determined during the HUMPPA-COPEC 2010 summer campaign. Differences in chemical composition and in emission strength were observed between the different trees, which confirmed that they represented different chemotypes. The chemotypes of Scots pine can be classified according to species with high, no and intermediate content of Δ-3-carene. The "non-Δ-3-carene" chemotype was found to be the strongest emitter of monoterpenes. From this chemotype, β-myrcene, a very reactive monoterpene, was the dominant species accounting for more than 32 % of the total emission rates of isoprenoids followed by β-phellandrene (~27%. Myrcene fluxes ranged from 0.8 to 24 μg g−1 (dw h−1. α-Farnesene was the dominant sesquiterpene species, with average emission rates of 318 ng g−1 (dw h−1. In the high Δ-3-carene chemotype, more than 48% of the total monoterpene emission was Δ-3-carene. The average Δ-3-carene emission rate (from chemotype 3, circa 609 ng g−1 (dw h−1 reported here is consistent with the previously reported summer season value. Daily maximum temperatures varied between 20 and 35 °C during the measurements. The monoterpene emissions from spruce were dominated by limonene (35%, β-phellandrene (15%, α-pinene (14% and eucalyptol (9%. Total spruce monoterpene emissions ranged from 0.55 up to 12.2 μg g−1 (dw h−1. Overall the total terpene flux (monoterpenes + sesquiterpenes from all studied tree species varied from 230 ng g−1 (dw h−1 up to 66 μg g−1 (dw h−1. Total ambient monoterpenes (including α-pinene, Δ-3-carene, β-pinene and β-myrcene measured during the campaign

  5. Artificial oxygen transport protein

    Science.gov (United States)

    Dutton, P. Leslie

    2014-09-30

    This invention provides heme-containing peptides capable of binding molecular oxygen at room temperature. These compounds may be useful in the absorption of molecular oxygen from molecular oxygen-containing atmospheres. Also included in the invention are methods for treating an oxygen transport deficiency in a mammal.

  6. A Cytosolic Arabidopsis d-Xylulose Kinase Catalyzes the Phosphorylation of 1-Deoxy-d-Xylulose into a Precursor of the Plastidial Isoprenoid Pathway1

    Science.gov (United States)

    Hemmerlin, Andréa; Tritsch, Denis; Hartmann, Michael; Pacaud, Karine; Hoeffler, Jean-François; van Dorsselaer, Alain; Rohmer, Michel; Bach, Thomas J.

    2006-01-01

    Plants are able to integrate exogenous 1-deoxy-d-xylulose (DX) into the 2C-methyl-d-erythritol 4-phosphate pathway, implicated in the biosynthesis of plastidial isoprenoids. Thus, the carbohydrate needs to be phosphorylated into 1-deoxy-d-xylulose 5-phosphate and translocated into plastids, or vice versa. An enzyme capable of phosphorylating DX was partially purified from a cell-free Arabidopsis (Arabidopsis thaliana) protein extract. It was identified by mass spectrometry as a cytosolic protein bearing d-xylulose kinase (XK) signatures, already suggesting that DX is phosphorylated within the cytosol prior to translocation into the plastids. The corresponding cDNA was isolated and enzymatic properties of a recombinant protein were determined. In Arabidopsis, xylulose kinases are encoded by a small gene family, in which only two genes are putatively annotated. The additional gene is coding for a protein targeted to plastids, as was proved by colocalization experiments using green fluorescent protein fusion constructs. Functional complementation assays in an Escherichia coli strain deleted in xk revealed that the cytosolic enzyme could exclusively phosphorylate xylulose in vivo, not the enzyme that is targeted to plastids. xk activities could not be detected in chloroplast protein extracts or in proteins isolated from its ancestral relative Synechocystis sp. PCC 6803. The gene encoding the plastidic protein annotated as “xylulose kinase” might in fact yield an enzyme having different phosphorylation specificities. The biochemical characterization and complementation experiments with DX of specific Arabidopsis knockout mutants seedlings treated with oxo-clomazone, an inhibitor of 1-deoxy-d-xylulose 5-phosphate synthase, further confirmed that the cytosolic protein is responsible for the phosphorylation of DX in planta. PMID:16920870

  7. Prerequisite for highly efficient isoprenoid production by cyanobacteria discovered through the over-expression of 1-deoxy-d-xylulose 5-phosphate synthase and carbon allocation analysis.

    Science.gov (United States)

    Kudoh, Kai; Kawano, Yusuke; Hotta, Shingo; Sekine, Midori; Watanabe, Takafumi; Ihara, Masaki

    2014-07-01

    Cyanobacteria have recently been receiving considerable attention owing to their potential as photosynthetic producers of biofuels and biomaterials. Here, we focused on the production of isoprenoids by cyanobacteria, and aimed to provide insight into metabolic engineering design. To this end, we examined the over-expression of a key enzyme in 2-C-methyl-d-erythritol 4-phosphate (MEP) pathway, 1-deoxy-d-xylulose 5-phosphate synthase (DXS) in the cyanobacterium Synechocystis sp. PCC6803. In the DXS-over-expression strain (Dxs_ox), the mRNA and protein levels of DXS were 4-times and 1.5-times the levels in the wild-type (WT) strain, respectively. The carotenoid content of the Dxs_ox strain (8.4 mg/g dry cell weight [DCW]) was also up to 1.5-times higher than that in the WT strain (5.6 mg/g DCW), whereas the glycogen content dramatically decreased to an undetectable level. These observations suggested that the carotenoid content in the Dxs_ox strain was increased by consuming glycogen, which is a C-storage compound in cyanobacteria. We also quantified the total sugar (145 and 104 mg/g DCW), total fatty acids (31 and 24 mg/g DCW) and total protein (200 and 240 mg/g DCW) content in the WT and Dxs_ox strains, respectively, which were much higher than the carotenoid content. In particular, approximately 54% of the proteins were phycobiliproteins. This study demonstrated the major destinations of carbon flux in cyanobacteria, and provided important insights into metabolic engineering. Target yield can be improved through optimization of gene expression, the DXS protein stabilization, cell propagation depression and restriction of storage compound synthesis.

  8. Physiological and molecular responses of the isoprenoid biosynthetic pathway in a drought-resistant Mediterranean shrub, Cistus creticus exposed to water deficit.

    Science.gov (United States)

    Munné-Bosch, Sergi; Falara, Vasiliki; Pateraki, Irene; López-Carbonell, Marta; Cela, Jana; Kanellis, Angelos K

    2009-01-30

    The goal of the present research was to obtain new insights into the mechanisms underlying drought stress resistance in plants. Specifically, we evaluated changes in the expression of genes encoding enzymes involved in isoprenoid biosynthesis, together with the levels of the corresponding metabolites (chlorophylls, carotenoids, tocopherols and abscisic acid), in a drought-resistant Mediterranean shrub, Cistus creticus grown under Mediterranean field conditions. Summer drought led to reductions in the relative leaf water content (RWC) by 25%, but did not alter the maximum efficiency of PSII, indicating the absence of damage to the photosynthetic apparatus. While the expression of genes encoding C. creticus chlorophyll a oxygenase/chlorophyll b synthase (CAO) and phytoene synthase (PSY) were not affected by water deficit, the genes encoding homogentisate phytyl-transferase (HPT) and 9-cis-epoxycarotenoid dioxygenase (NCED) were induced in water-stressed (WS) plants. Drought-induced changes in gene expression were observed at early stages of drought and were strongly correlated with levels of the corresponding metabolites, with simultaneous increases in abscisic acid and alpha-tocopherol levels of up to 4-fold and 62%, respectively. Furthermore, alpha-tocopherol levels were strongly positively correlated with abscisic acid contents, but not with the levels of jasmonic acid and salicylic acid. We conclude that the abscisic acid and tocopherol biosynthetic pathway may be regulated at the transcript level in WS C. creticus plants, and that the genes encoding HPT and NCED may play a key role in the drought stress resistance of this Mediterranean shrub by modulating abscisic acid and tocopherol biosynthesis.

  9. A cytosolic Arabidopsis D-xylulose kinase catalyzes the phosphorylation of 1-deoxy-D-xylulose into a precursor of the plastidial isoprenoid pathway.

    Science.gov (United States)

    Hemmerlin, Andréa; Tritsch, Denis; Hartmann, Michael; Pacaud, Karine; Hoeffler, Jean-François; van Dorsselaer, Alain; Rohmer, Michel; Bach, Thomas J

    2006-10-01

    Plants are able to integrate exogenous 1-deoxy-D-xylulose (DX) into the 2C-methyl-D-erythritol 4-phosphate pathway, implicated in the biosynthesis of plastidial isoprenoids. Thus, the carbohydrate needs to be phosphorylated into 1-deoxy-D-xylulose 5-phosphate and translocated into plastids, or vice versa. An enzyme capable of phosphorylating DX was partially purified from a cell-free Arabidopsis (Arabidopsis thaliana) protein extract. It was identified by mass spectrometry as a cytosolic protein bearing D-xylulose kinase (XK) signatures, already suggesting that DX is phosphorylated within the cytosol prior to translocation into the plastids. The corresponding cDNA was isolated and enzymatic properties of a recombinant protein were determined. In Arabidopsis, xylulose kinases are encoded by a small gene family, in which only two genes are putatively annotated. The additional gene is coding for a protein targeted to plastids, as was proved by colocalization experiments using green fluorescent protein fusion constructs. Functional complementation assays in an Escherichia coli strain deleted in xk revealed that the cytosolic enzyme could exclusively phosphorylate xylulose in vivo, not the enzyme that is targeted to plastids. xk activities could not be detected in chloroplast protein extracts or in proteins isolated from its ancestral relative Synechocystis sp. PCC 6803. The gene encoding the plastidic protein annotated as "xylulose kinase" might in fact yield an enzyme having different phosphorylation specificities. The biochemical characterization and complementation experiments with DX of specific Arabidopsis knockout mutants seedlings treated with oxo-clomazone, an inhibitor of 1-deoxy-D-xylulose 5-phosphate synthase, further confirmed that the cytosolic protein is responsible for the phosphorylation of DX in planta.

  10. Oxygen sensing and signaling.

    Science.gov (United States)

    van Dongen, Joost T; Licausi, Francesco

    2015-01-01

    Oxygen is an indispensable substrate for many biochemical reactions in plants, including energy metabolism (respiration). Despite its importance, plants lack an active transport mechanism to distribute oxygen to all cells. Therefore, steep oxygen gradients occur within most plant tissues, which can be exacerbated by environmental perturbations that further reduce oxygen availability. Plants possess various responses to cope with spatial and temporal variations in oxygen availability, many of which involve metabolic adaptations to deal with energy crises induced by low oxygen. Responses are induced gradually when oxygen concentrations decrease and are rapidly reversed upon reoxygenation. A direct effect of the oxygen level can be observed in the stability, and thus activity, of various transcription factors that control the expression of hypoxia-induced genes. Additional signaling pathways are activated by the impact of oxygen deficiency on mitochondrial and chloroplast functioning. Here, we describe the molecular components of the oxygen-sensing pathway.

  11. Involvement of a broccoli COQ5 methyltransferase in the production of volatile selenium compounds.

    Science.gov (United States)

    Zhou, Xin; Yuan, Youxi; Yang, Yong; Rutzke, Michael; Thannhauser, Theodore W; Kochian, Leon V; Li, Li

    2009-10-01

    Selenium (Se) is an essential micronutrient for animals and humans but becomes toxic at high dosage. Biologically based Se volatilization, which converts Se into volatile compounds, provides an important means for cleanup of Se-polluted environments. To identify novel genes whose products are involved in Se volatilization from plants, a broccoli (Brassica oleracea var italica) cDNA encoding COQ5 methyltransferase (BoCOQ5-2) in the ubiquinone biosynthetic pathway was isolated. Its function was authenticated by complementing a yeast coq5 mutant and by detecting increased cellular ubiquinone levels in the BoCOQ5-2-transformed bacteria. BoCOQ5-2 was found to promote Se volatilization in both bacteria and transgenic Arabidopsis (Arabidopsis thaliana) plants. Bacteria expressing BoCOQ5-2 produced an over 160-fold increase in volatile Se compounds when they were exposed to selenate. Consequently, the BoCOQ5-2-transformed bacteria had dramatically enhanced tolerance to selenate and a reduced level of Se accumulation. Transgenic Arabidopsis expressing BoCOQ5-2 volatilized three times more Se than the vector-only control plants when treated with selenite and exhibited an increased tolerance to Se. In addition, the BoCOQ5-2 transgenic plants suppressed the generation of reactive oxygen species induced by selenite. BoCOQ5-2 represents, to our knowledge, the first plant enzyme that is not known to be directly involved in sulfur/Se metabolism yet was found to mediate Se volatilization. This discovery opens up new prospects regarding our understanding of the complete metabolism of Se and may lead to ways to modify Se-accumulator plants with increased efficiency for phytoremediation of Se-contaminated environments.

  12. Volatile depletion in the TW Hydrae disk atmosphere

    CERN Document Server

    Du, Fujun; Hogerheijde, Michiel R

    2015-01-01

    An abundance decrease in carbon- and oxygen-bearing species relative to dust has been frequently found in planet-forming disks, which can be attributed to an overall reduction of gas mass. However, in the case of TW Hya, the only disk with gas mass measured directly with HD rotational lines, the inferred gas mass ($\\lesssim$0.005 solar mass) is significantly below the directly measured value ($\\gtrsim$0.05 solar mass). We show that this apparent conflict can be resolved if the elemental abundances of carbon and oxygen are reduced in the upper layers of the outer disk but are normal elsewhere (except for a possible enhancement of their abundances in the inner disk). The implication is that in the outer disk, the main reservoir of the volatiles (CO, water, ...) resides close to the midplane, locked up inside solid bodies that are too heavy to be transported back to the atmosphere by turbulence. An enhancement in the carbon and oxygen abundances in the inner disk can be caused by inward migration of these solid ...

  13. Oxygen-enhanced combustion

    CERN Document Server

    Baukal, Charles E

    2013-01-01

    Combustion technology has traditionally been dominated by air/fuel combustion. However, two developments have increased the significance of oxygen-enhanced combustion-new technologies that produce oxygen less expensively and the increased importance of environmental regulations. Advantages of oxygen-enhanced combustion include less pollutant emissions as well as increased energy efficiency and productivity. Oxygen-Enhanced Combustion, Second Edition compiles information about using oxygen to enhance industrial heating and melting processes. It integrates fundamental principles, applications, a

  14. High temperature volatility and oxidation measurements of titanium and silicon containing ceramic materials

    Science.gov (United States)

    Nguyen, Quynhgiao N.

    Titanium (Ti) containing materials are of high interest to the aerospace industry due to its high temperature capability, strength, and light weight. As with most metals an exterior oxide layer naturally exists in environments that contain oxygen (i.e. air). At high temperatures, water vapor plays a key role in the volatility of materials including oxide surfaces. This study first evaluates several hot-pressed Ti-containing compositions at high temperatures as a function of oxidation resistance. This study will also evaluate cold pressed titanium dioxide (TiO2) powder pellets at a temperature range of 1400°C--1200°C in water containing environments to determine the volatile hydoxyl species using the transpiration method. The water content ranged from 0-76 mole % and the oxygen content range was 0-100 mole % during the 20-250 hour exposure times. Preliminary results indicate that oxygen is not a key contributor at these temperatures and the following reaction is the primary volatile equation at all three temperatures: TiO 2 (s) + H2O (g) = TiO(OH)2 (g).

  15. Flower volatiles, crop varieties and bee responses.

    Directory of Open Access Journals (Sweden)

    Björn K Klatt

    Full Text Available Pollination contributes to an estimated one third of global food production, through both the improvement of the yield and the quality of crops. Volatile compounds emitted by crop flowers mediate plant-pollinator interactions, but differences between crop varieties are still little explored. We investigated whether the visitation of crop flowers is determined by variety-specific flower volatiles using strawberry varieties (Fragaria x ananassa Duchesne and how this affects the pollination services of the wild bee Osmia bicornis L. Flower volatile compounds of three strawberry varieties were measured via headspace collection. Gas chromatography showed that the three strawberry varieties produced the same volatile compounds but with quantitative differences of the total amount of volatiles and between distinct compounds. Electroantennographic recordings showed that inexperienced females of Osmia bicornis had higher antennal responses to all volatile compounds than to controls of air and paraffin oil, however responses differed between compounds. The variety Sonata was found to emit a total higher level of volatiles and also higher levels of most of the compounds that evoked antennal responses compared with the other varieties Honeoye and Darselect. Sonata also received more flower visits from Osmia bicornis females under field conditions, compared with Honeoye. Our results suggest that differences in the emission of flower volatile compounds among strawberry varieties mediate their attractiveness to females of Osmia bicornis. Since quality and quantity of marketable fruits depend on optimal pollination, a better understanding of the role of flower volatiles in crop production is required and should be considered more closely in crop-variety breeding.

  16. Volatility Forecast in Crises and Expansions

    Directory of Open Access Journals (Sweden)

    Sergii Pypko

    2015-08-01

    Full Text Available We build a discrete-time non-linear model for volatility forecasting purposes. This model belongs to the class of threshold-autoregressive models, where changes in regimes are governed by past returns. The ability to capture changes in volatility regimes and using more accurate volatility measures allow outperforming other benchmark models, such as linear heterogeneous autoregressive model and GARCH specifications. Finally, we show how to derive closed-form expression for multiple-step-ahead forecasting by exploiting information about the conditional distribution of returns.

  17. Modelling of volatility in monetary transmission mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Dobešová, Anna; Klepáč, Václav; Kolman, Pavel [Department of Statistics and Operation Analysis, Faculty of Business and Economics, Mendel University in Brno, Zemědělská 1, 61300, Brno (Czech Republic); Bednářová, Petra [Institute of Technology and Business, Okružní 517/10, 370 01, České Budějovice (Czech Republic)

    2015-03-10

    The aim of this paper is to compare different approaches to modeling of volatility in monetary transmission mechanism. For this purpose we built time-varying parameter VAR (TVP-VAR) model with stochastic volatility and VAR-DCC-GARCH model with conditional variance. The data from three European countries are included in the analysis: the Czech Republic, Germany and Slovakia. Results show that VAR-DCC-GARCH system captures higher volatility of observed variables but main trends and detected breaks are generally identical in both approaches.

  18. Securing non-volatile memory regions

    Science.gov (United States)

    Faraboschi, Paolo; Ranganathan, Parthasarathy; Muralimanohar, Naveen

    2013-08-20

    Methods, apparatus and articles of manufacture to secure non-volatile memory regions are disclosed. An example method disclosed herein comprises associating a first key pair and a second key pair different than the first key pair with a process, using the first key pair to secure a first region of a non-volatile memory for the process, and using the second key pair to secure a second region of the non-volatile memory for the same process, the second region being different than the first region.

  19. Transabdominal oxygenation using perfluorocarbons.

    Science.gov (United States)

    Chiba, T; Harrison, M R; Ohkubo, T; Rollins, M D; Albanese, C T; Jennings, R W

    1999-05-01

    Evaluation of the intraabdominal (intraperitoneal and intraluminal) administration of oxygen-saturated perfluorocarbon on both portal and arterial blood oxygenation. Eight male rabbits were divided into the test (n = 5) and control (n = 3) groups. Each underwent intrajejunal, intraperitoneal, and intravascular (artery, portal vein) catheter placements along with ligation of the duodenum and the terminal ileum under general anesthesia. The test group received oxygen-saturated perfluorotripropylamine (FTPA), and the control group received oxygen desaturated FTPA. The oxygen delivery was assessed by serial blood gas measurements before and after the administration of FTPA. The administration of oxygen-saturated FTPA significantly increased the partial pressure of oxygen within both the arterial and the portal venous blood (PaO2, PpVO2) without significant changes in PCO2 values. Oxygen desaturated FTPA failed to show any effects on blood gas values. Compared with oxygen desaturated FTPA, oxygen-saturated FTPA increased PaO2, PpVO2, and oxygen saturation (artery, portal vein) significantly at some, but not all of the time-points measured. The intraabdominal administration of saturated FTPA improved both the portal venous and the arterial oxygenation. This new mode of oxygenation may be helpful as an adjunct to conventional oxygen delivery systems.

  20. Oxygen permeable membrane for oxygen enriched combustion

    Energy Technology Data Exchange (ETDEWEB)

    Asakawa, S. (Matsushita Research Inst., Tokyo, Japan); Saito, Y.; Kawahito, M.; Ito, Y.; Tsuchiya, S.; Sugata, K.

    1983-02-01

    An oxygen enriched air production system using gas separation membranes has been developed to be used for fuel combustion systems. High oxygen permeable scopolymers, including three dimensional structure, have been synthesized through condensation of polyvinylphenol with some, ..cap alpha..,..omega..-bis (diethylamino) polydimethylsiloxanes. The experimental results showed that the oxygen permeability through the copolymer varies as a function of the dimethylsiloxane content of the copolymers. Such composition dependence of the oxygen permeability was explained on the basis of polymer constitution. Typical values of the oxygen permeability, 3.4 x 10/sup -8/ (cc x cm/cm/sup 2/ x sec x cmHg) and ..cap alpha.., 2.1, were obtained at 72% of dimethylsiloxane content. The copolymers are soluble in most common organic solvents and uniform, defect-free membranes as thin as 1000 Angstroms have been formed by spreading solutions of the copolymer on water. Composite membranes fabricated by applying the membranes to porous support materials were used for practical gas separation and 30% oxygen enriched air was produced from ambient air. A new type oxygen enriched combustion system, which is more efficient for energy saving, has been developed by utilizing oxygen enriched air thus produced. 15 references, 15 figures, 1 table.

  1. Realized volatility and absolute return volatility: a comparison indicating market risk.

    Science.gov (United States)

    Zheng, Zeyu; Qiao, Zhi; Takaishi, Tetsuya; Stanley, H Eugene; Li, Baowen

    2014-01-01

    Measuring volatility in financial markets is a primary challenge in the theory and practice of risk management and is essential when developing investment strategies. Although the vast literature on the topic describes many different models, two nonparametric measurements have emerged and received wide use over the past decade: realized volatility and absolute return volatility. The former is strongly favored in the financial sector and the latter by econophysicists. We examine the memory and clustering features of these two methods and find that both enable strong predictions. We compare the two in detail and find that although realized volatility has a better short-term effect that allows predictions of near-future market behavior, absolute return volatility is easier to calculate and, as a risk indicator, has approximately the same sensitivity as realized volatility. Our detailed empirical analysis yields valuable guidelines for both researchers and market participants because it provides a significantly clearer comparison of the strengths and weaknesses of the two methods.

  2. Mecanismos de acción de isoprenoides naturales y su combinación con estatinas sobre la proliferación y el metabolismo lipídico en distintos modelos celulares

    OpenAIRE

    Rodenak Kladniew, Boris

    2015-01-01

    En el presente trabajo se evaluó la capacidad antiproliferativa, anticolesterogénica y los efectos sobre el metabolismo lipídico de dos isoprenoides de 10 carbonos, linalool (monoterpeno alcohol lineal) y 1,8-cineole (monoterpeno cíclico con grupo éter), sobre células HepG2 (procedentes de un hepatocarcinoma humano) como modelo de célula hepática y A549 (provenientes de adenocarcinoma de pulmón humano) como tipo celular extra-hepático. Se analizaron los mecanismos de acción involucrados y los...

  3. Does Energy Consumption Volatility Affect Real GDP Volatility? An Empirical Analysis for the UK

    OpenAIRE

    Abdul Rashid; Ozge Kandemir Kocaaslan

    2013-01-01

    This paper empirically examines the relation between energy consumption volatility and unpredictable variations in real gross domestic product (GDP) in the UK. Estimating the Markov switching ARCH model we find a significant regime switching in the behavior of both energy consumption and GDP volatility. The results from the Markov regime-switching model show that the variability of energy consumption has a significant role to play in determining the behavior of GDP volatilities. Moreover, the...

  4. Lunar In-Situ Volatile Extraction Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A method of extracting volatile resources from the Lunar regolith is proposed to reduce the launch mass and cost of bringing such resources from the Earth to enable...

  5. Food commodity price volatility and food insecurity

    National Research Council Canada - National Science Library

    Alexander Sarris

    2013-01-01

      The paper first reviews several issues relevant to global food commodity market volatility as it pertains to food security, and food importing developing countries, and then discusses international...

  6. Volatility and the natural resource curse

    NARCIS (Netherlands)

    van der Ploeg, F.; Poelhekke, S.

    2009-01-01

    We provide cross-country evidence that rejects the traditional interpretation of the natural resource curse. First, growth depends negatively on volatility of unanticipated output growth independent of initial income, investment, human capital, trade openness, natural resource dependence, and popula

  7. Volatile compounds in meat and meat products

    Directory of Open Access Journals (Sweden)

    Monika KOSOWSKA

    Full Text Available Abstract Meaty flavor is composed of a few hundreds of volatile compounds, only minor part of which are responsible for the characteristic odor. It is developed as a result of multi-directional reactions proceeding between non-volatile precursors contained in raw meat under the influence of temperature. The volatile compounds are generated upon: Maillard reactions, lipid oxidation, interactions between Maillard reaction products and lipid oxidation products as well as upon thiamine degradation. The developed flavor is determined by many factors associated with: raw material (breed, sex, diet and age of animal, conditions and process of slaughter, duration and conditions of meat storage, type of muscle, additives applied and the course of the technological process. The objective of this review article is to draw attention to the issue of volatile compounds characteristic for meat products and factors that affect their synthesis.

  8. Volatile profile of wine Teran PTP

    Directory of Open Access Journals (Sweden)

    Helena BAŠA ČESNIK

    2015-11-01

    Full Text Available Teran PTP is a protected wine with a recognized traditional denomination produced from a grapevine variety ‘Refošk’ in winegrowing district Kras in Slovenia (European Union, 2009; Pravilnik, 2008. The aromatic profile of 82 Teran PTP wines produced in years 2011, 2012 and 2013 was monitored. Intotal the content of 16 volatile compounds was determined. The volatile compounds from wine were extracted following the liquid-liquid extraction and determined with a GC-MS method. The odour activity values and relative odour contributions were calculated for each volatile compound identified. Among sensorial important volatiles the highest odour activity values were determined for ethyl octanoate, ethyl hexanoate, isoamyl acetate and ethyl butyrate. Other research papers also showed, that all red wines investigated except one contained ethyl octanoate, ethyl hexanoate, isoamyl acetate and ethyl butyrate above sensory thresholds.

  9. STOCK MARKET VOLATILITY: DEVELOPED AND EMERGING MARKETS

    National Research Council Canada - National Science Library

    Mohammad Athar Noor; Mohd Asif Khan

    2012-01-01

      This paper examines the general patterns of recent global stock market returns and the volatility of such returns using 17 global stock indexes of countries classified into developed and emerging...

  10. International trade and exchange rate volatility

    NARCIS (Netherlands)

    J.M.A. Viaene (Jean-Marie); C.G. de Vries (Casper)

    1992-01-01

    textabstractFor currencies with well developed forward markets several papers have investigated the conjectured negative relationship between trade and short term exchange rate volatility, without being very successful. A theoretical explanation for the empirical anomalies is provided by solving

  11. Characterisation of selected volatile organic compounds in ...

    African Journals Online (AJOL)

    kshale

    2013-05-15

    May 15, 2013 ... spectrometry. K. Shale1*, J. Mukamugema2, R. J. Lues1, P. Venter3 and K. K. Mokoena1 ..... Cajka T, Riddellova K, Tomaniova M, Hajslova J (2010). Recognition of ... volatile organic compounds of coniferous needle litter.

  12. Assessing relative volatility/intermittency/energy dissipation

    DEFF Research Database (Denmark)

    Barndorff-Nielsen, Ole E.; Pakkanen, Mikko S.; Schmiegel, Jürgen

    2014-01-01

    We introduce the notion of relative volatility/intermittency and demonstrate how relative volatility statistics can be used to estimate consistently the temporal variation of volatility/intermittency when the data of interest are generated by a non-semimartingale, or a Brownian semistationary...... process in particular. This estimation method is motivated by the assessment of relative energy dissipation in empirical data of turbulence, but it is also applicable in other areas. We develop a probabilistic asymptotic theory for realised relative power variations of Brownian semistationary processes......, and introduce inference methods based on the theory. We also discuss how to extend the asymptotic theory to other classes of processes exhibiting stochastic volatility/intermittency. As an empirical application, we study relative energy dissipation in data of atmospheric turbulence....

  13. Long memory and tail dependence in trading volume and volatility

    DEFF Research Database (Denmark)

    Rossi, Eduardo; Santucci de Magistris, Paolo

    2013-01-01

    We investigate the relationship between volatility, measured by realized volatility, and trading volume for 25 NYSE stocks. We show that volume and volatility are long memory but not fractionally cointegrated in most cases. We also find right tail dependence in the volatility and volume innovations...

  14. Financial Development, Financial Structure, and Macroeconomic Volatility: Evidence from China

    Directory of Open Access Journals (Sweden)

    Feng Wei

    2016-11-01

    Full Text Available Using annual data from 1997–2014 of 30 provinces, municipalities, and autonomous regions, subdividing trended and cyclical volatility of macroeconomics and inflation, considering different indicators of financial development and financial structure, this paper investigated the impact of financial development and financial structure on macroeconomic volatility. The empirical results found that (1 the trended and cyclical volatility of the previous macroeconomic period had a significantly positive impact on that of the current period, and the impact of trended volatility was greater than that of cyclical volatility; (2 financial development had a significantly negative impact on macroeconomic cyclical volatility through inflation cyclical volatility, but inflation trended volatility would amplify macroeconomic volatility; financial markets have no significant effect on macroeconomic volatility; financial structure measured with the ratio of stock market turnover and the efficiency of the financial development had a significant positive impact on macroeconomic cyclical volatility; and (3 inflation trended volatility had a significantly negative impact on macroeconomic cyclical volatility and trended volatility, while inflation cyclical volatility had a significantly positive impact on macroeconomic cyclical volatility.

  15. Long memory and tail dependence in trading volume and volatility

    DEFF Research Database (Denmark)

    Rossi, Eduardo; Santucci de Magistris, Paolo

    2013-01-01

    We investigate the relationship between volatility, measured by realized volatility, and trading volume for 25 NYSE stocks. We show that volume and volatility are long memory but not fractionally cointegrated in most cases. We also find right tail dependence in the volatility and volume innovations...

  16. Essays on Economic Volatility and Financial Frictions

    OpenAIRE

    Zhao, Hongyan

    2012-01-01

    This dissertation consists of three essays in macroeconomics. The first one essay discusses the reasons of Chinese huge foreign reserves holdings. It contributes to the literature of sudden stops, precautionary saving and foreign assets holdings. In the second essay, I study the price volatility of commodities and manufactured goods. I measure the price volatility of each individual goods but not on the aggregated level and therefore the results complete the related study. The third essay exp...

  17. Examining Moderate Volatile Loss through Lunar History

    Science.gov (United States)

    Saxena, Prabal; Killen, Rosemary M.; Airapetian, Vladimir; Petro, Noah; Mandell, Avi

    2017-06-01

    While the Moon and bulk silicate earth (BSE) share many compositional similarities, a notable difference is the apparent depletion of moderate volatiles in lunar samples. Depletion of elements such as sodium and potassium relative to BSE composition has been observed in Apollo samples. The source of these depletions is poorly understood but may be a result of preferential accretion of volatile-rich melt in the inner disk to the Earth during Moon formation.However, recent Kepler data has indicated that stellar analogues to our Sun experience enhanced flare activity early in their evolution. This implies that the Sun may have had a higher frequency and energy of flares and associated Coronal Mass Ejections (CME) in its distant past. We examine the potential impacts of this increased activity on lunar exosphere generation and specifically on potential loss of moderate volatiles including sodium and potassium.We use a surface bounded exosphere model that incorporates multiple processes including photon stimulated desorption, kinetic sputtering and impact vaporization in order to study potential moderate volatile loss under a variety of different conditions. This model is informed by appropriate solar wind and CME properties, which includes CMEs of different energies. We also incorporate regolith overturn to determine ranges of potential bulk depletion of moderate volatiles from the lunar regolith.Our work is aimed at determining the potential impact of solar activity on the depletion of moderate volatiles in the lunar regolith. Such a contribution is important to ascertain in order to isolate the depletion of volatiles due to disk processes and may thus help constrain details of the Moon's formation. Finally, we also examine the potential of lunar abundances of moderate volatiles as an observational tracer of past solar activity.

  18. Anticipating Long-Term Stock Market Volatility

    OpenAIRE

    Conrad, Christian; Loch, Karin

    2012-01-01

    We investigate the relationship between long-term U.S. stock market risks and the macroeconomic environment using a two component GARCH-MIDAS model. Our results provide strong evidence in favor of counter-cyclical behavior of long-term stock market volatility. Among the various macro variables in our dataset the term spread, housing starts, corporate profits and the unemployment rate have the highest predictive ability for stock market volatility . While the term spread and housing starts are...

  19. Ammonia volatilization from sows on grassland

    Science.gov (United States)

    Sommer, S. G.; Søgaard, H. T.; Møller, H. B.; Morsing, S.

    According to regulations, sows with piglets on organic farms must graze on pastures. Volatilization of ammonia (NH 3) from urine patches may represent a significant source of nitrogen (N) loss from these farms. Inputs of N are low on organic farms and losses may reduce crop production. This study examined spatial variations in NH 3 volatilization using a movable dynamic chamber, and the pH and total ammoniacal nitrogen (TAN) content in the topsoil of pastures with grazing sows was measured during five periods between June 1998 and May 1999. Gross NH 3 volatilization from the pastures was also measured with an atmospheric mass balance technique during seven periods from September 1997 until June 1999. The dynamic chamber study showed a high variation in NH 3 volatilization because of the distribution of urine; losses were between 0 and 2.8 g NH 3-N m -2 day -1. Volatilization was highest near the feeding area and the huts, where the sows tended to urinate. Ammonia volatilization rate was linearly related to the product of NH 3 concentration in the boundary layer and wind speed. The NH 3 in the boundary layer was in equilibrium with NH 3 in soil solution. Gross NH 3 volatilization was in the range 0.07-2.1 kg NH 3-N ha -1 day -1 from a pasture with 24 sows ha -1. Ammonia volatilization was related to the amount of feed given to the sows, incident solar radiation and air temperature during measuring periods, and also to temperature, incident solar radiation and rain 1-2 days before measurements. Annual ammonia loss was 4.8 kg NH 3-N sow -1.

  20. Volatile flavor compounds in yogurt: a review.

    Science.gov (United States)

    Cheng, Hefa

    2010-11-01

    Considerable knowledge has been accumulated on the volatile compounds contributing to the aroma and flavor of yogurt. This review outlines the production of the major flavor compounds in yogurt fermentation and the analysis techniques, both instrumental and sensory, for quantifying the volatile compounds in yogurt. The volatile compounds that have been identified in plain yogurt are summarized, with the few key aroma compounds described in detail. Most flavor compounds in yogurt are produced from lipolysis of milkfat and microbiological transformations of lactose and citrate. More than 100 volatiles, including carbonyl compounds, alcohols, acids, esters, hydrocarbons, aromatic compounds, sulfur-containing compounds, and heterocyclic compounds, are found in yogurt at low to trace concentrations. Besides lactic acid, acetaldehyde, diacetyl, acetoin, acetone, and 2-butanone contribute most to the typical aroma and flavor of yogurt. Extended storage of yogurt causes off-flavor development, which is mainly attributed to the production of undesired aldehydes and fatty acids during lipid oxidation. Further work on studying the volatile flavor compounds-matrix interactions, flavor release mechanisms, and the synergistic effect of flavor compounds, and on correlating the sensory properties of yogurt with the compositions of volatile flavor compounds are needed to fully elucidate yogurt aroma and flavor.

  1. Market volatility modeling for short time window

    Science.gov (United States)

    de Mattos Neto, Paulo S. G.; Silva, David A.; Ferreira, Tiago A. E.; Cavalcanti, George D. C.

    2011-10-01

    The gain or loss of an investment can be defined by the movement of the market. This movement can be estimated by the difference between the magnitudes of two stock prices in distinct periods and this difference can be used to calculate the volatility of the markets. The volatility characterizes the sensitivity of a market change in the world economy. Traditionally, the probability density function (pdf) of the movement of the markets is analyzed by using power laws. The contributions of this work is two-fold: (i) an analysis of the volatility dynamic of the world market indexes is performed by using a two-year window time data. In this case, the experiments show that the pdf of the volatility is better fitted by exponential function than power laws, in all range of pdf; (ii) after that, we investigate a relationship between the volatility of the markets and the coefficient of the exponential function based on the Maxwell-Boltzmann ideal gas theory. The results show an inverse relationship between the volatility and the coefficient of the exponential function. This information can be used, for example, to predict the future behavior of the markets or to cluster the markets in order to analyze economic patterns.

  2. Oxygen transport membrane

    DEFF Research Database (Denmark)

    2015-01-01

    The present invention relates to a novel composite oxygen transport membrane as well as its preparation and uses thereof.......The present invention relates to a novel composite oxygen transport membrane as well as its preparation and uses thereof....

  3. Hyperbaric oxygen therapy

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/article/002375.htm Hyperbaric oxygen therapy To use the sharing features on this page, please enable JavaScript. Hyperbaric oxygen therapy uses a special pressure chamber to increase ...

  4. Biogeochemistry: Oxygen burrowed away

    NARCIS (Netherlands)

    Meysman, F.J.R.

    2014-01-01

    Multicellular animals probably evolved at the seafloor after a rise in oceanic oxygen levels. Biogeochemical model simulations suggest that as these animals started to rework the seafloor, they triggered a negative feedback that reduced global oxygen.

  5. Biogeochemistry: Oxygen burrowed away

    NARCIS (Netherlands)

    Meysman, F.J.R.

    2014-01-01

    Multicellular animals probably evolved at the seafloor after a rise in oceanic oxygen levels. Biogeochemical model simulations suggest that as these animals started to rework the seafloor, they triggered a negative feedback that reduced global oxygen.

  6. Home Oxygen Therapy

    Science.gov (United States)

    ... Teenagers Living With Lung Disease Articles written by Respiratory Experts Home Oxygen Therapy More and more people are using oxygen therapy ... April 12, 2012 Revised: © 2017 American Association for Respiratory Care

  7. Oxygen evolution reaction catalysis

    Science.gov (United States)

    Haber, Joel A.; Jin, Jian; Xiang, Chengxiang; Gregoire, John M.; Jones, Ryan J.; Guevarra, Dan W.; Shinde, Aniketa A.

    2016-09-06

    An Oxygen Evolution Reaction (OER) catalyst includes a metal oxide that includes oxygen, cerium, and one or more second metals. In some instances, the cerium is 10 to 80 molar % of the metals in the metal oxide and/or the catalyst includes two or more second metals. The OER catalyst can be included in or on an electrode. The electrode can be arranged in an oxygen evolution system such that the Oxygen Evolution Reaction occurs at the electrode.

  8. Cryptococcus neoformans and oxygen

    OpenAIRE

    Vladislav,Raclavsky

    2006-01-01

    Oxygen is essential to life of all organisms except for obligate anaerobic species, because it is necessary for energy generation and also for some biosynthetic pathways. However, sensitivity to low oxygen levels can vary widely in different organisms and cell types. The pathogenic yeast species Cryptococcus neoformans is known to love oxygen. In response to the lack of oxygen (hypoxia), this yeast delays budding without resigning DNA replication, which eventually results in unique cell cycle...

  9. Proterozoic atmospheric oxygen

    DEFF Research Database (Denmark)

    Canfield, Donald Eugene

    2014-01-01

    This article is concerned with the evolution of atmospheric oxygen concentrations through the Proterozoic Eon. In particular, this article will seek to place the history of atmospheric oxygenation through the Proterozoic Eon in the context of the evolving physical environment including the history...... of continental growth and volcanic outgassing, as well as biogeochemical processing of elements within the oceans. The author will seek to explore constraints on the history of oxygenation and understand which processes have regulated oxygen through this eon....

  10. Multifractal diffusion entropy analysis on stock volatility in financial markets

    Science.gov (United States)

    Huang, Jingjing; Shang, Pengjian; Zhao, Xiaojun

    2012-11-01

    This paper introduces a generalized diffusion entropy analysis method to analyze long-range correlation then applies this method to stock volatility series. The method uses the techniques of the diffusion process and Rényi entropy to focus on the scaling behaviors of regular volatility and extreme volatility respectively in developed and emerging markets. It successfully distinguishes their differences where regular volatility exhibits long-range persistence while extreme volatility reveals anti-persistence.

  11. The partitioning of sulfur and chlorine between andesite melts and magmatic volatiles and the exchange coefficients of major cations

    Science.gov (United States)

    Zajacz, Zoltán; Candela, Philip A.; Piccoli, Philip M.; Sanchez-Valle, Carmen

    2012-07-01

    Andesite melts were equilibrated with an H-O-S-bearing volatile phase to determine the partition coefficients for S and Cl as a function of melt composition and oxygen fugacity. The experiments were conducted in rapid-quench MHC vessel assemblies at 200 MPa and 1000 °C, and over a range of imposed fO2 between NNO-1.2 and NNO+1.8. High fluid/melt mass ratios (∼15) were employed, allowing precise and accurate partition coefficients to be obtained by mass balance calculations. Chlorine exhibits Henrian behavior at ClO-0.5 activities typical for arc magmas, with D Cl volatile/melt = 1.36 ± 0.06 (1σ) below 0.2 wt.% Cl in the melt; at higher ClO-0.5 activities, D Cl volatile/melt increases linearly to 2.11 ± 0.02 at 1 wt.% Cl in the melt. In the volatile phase: FeCl2 ∼ NaCl > KCl ∼ HCl. The determination of cation exchange coefficients for major cations yielded: K K,Na volatile/melt = 1.23 ± 0.10 (1σ) and ∗K Fe,Na volatile/melt = D Fe volatile/melt / D Na volatile/melt = 1.08 ± 0.16 (1σ). Under these conditions, the concentration of HCl in the vapor is negatively correlated with the (Na + K)/(Al + Fe3+) ratio in the melt. Reduced sulfur (S2-) appears to obey Henry's law in andesite melt-volatile system at fH2S below pyrrhotite saturation. The partition coefficient for S at fO2 = NNO-0.5 correlates negatively with the FeO concentration in the melt, changing from 254 ± 25 at 4.0 wt.% FeO to 88 ± 6 at 7.5 wt.% FeO. Pyrrhotite saturation is reached when approximately 3.2 mol% S is present in the volatile phase at fO2 = NNO-0.5. At the sulfide/sulfate transition, the partition coefficient of S drops from 171 ± 23 to 21 ± 1 at a constant FeO content of ∼6 wt.% in the melt. At fO2 = NNO+1.8, anhydrite saturation is reached at ∼3.3 mol% S present in the volatile phase. Aqueous volatiles exsolving from intermediate to mafic magmas can efficiently extract S, and effect its transfer to sites of magmatic-hydrothermal ore deposit formation.

  12. Characterization of volatile and non-volatile compounds of fresh pepper (Capsicum annuum)

    NARCIS (Netherlands)

    Eggink, P.M.; Haanstra, J.P.W.; Tikunov, Y.M.; Bovy, A.G.; Visser, R.G.F.

    2010-01-01

    In this study volatile and non-volatile compounds and several agronomical important parameters were measured in mature fruits of elite sweet pepper breeding lines and hybrids and several genebank accessions from different Capsicum species. The sweet pepper breeding lines and hybrids were chosen to

  13. Modelling the Volatility-Return Trade-off when Volatility may be Nonstationary

    DEFF Research Database (Denmark)

    Dahl, Christian Møller; Iglesias, Emma M.

    In this paper a new GARCH-M type model, denoted the GARCH-AR, is proposed. In particular, it is shown that it is possible to generate a volatility-return trade-off in a regression model simply by introducing dynamics in the standardized disturbance process. Importantly, the volatility in the GARCH...

  14. Volatility Spillover and Multivariate Volatility Impulse Response Analysis of GFC News Events

    NARCIS (Netherlands)

    D.E. Allen (David); M.J. McAleer (Michael); R.J. Powell (Robert); A.K. Singh (Abhay)

    2016-01-01

    textabstractThis paper applies two measures to assess spillovers across markets: the Diebold Yilmaz (2012) Spillover Index and the Hafner and Herwartz (2006) analysis of multivariate GARCH models using volatility impulse response analysis. We use two sets of data, daily realized volatility estimates

  15. 负氧离子在仓储过程中对普洱生茶挥发性成分的影响%Effects of the negative oxygen ions on the Pu-erh raw tea volatile components during storage

    Institute of Scientific and Technical Information of China (English)

    任丽; 周红杰; 许腾升; 任洪涛

    2016-01-01

    Objective To improve the beneficial content of tea leaves and reduce the content of smoke substances, so as to improve the quality and taste of Pu-erh raw tea.Methods The aroma components were enriched by the simultaneous distillation extraction. The aroma components of Pu-erh raw tea before and after the negative oxygen ion storage were compared and analyzed by gas chromatography-mass spectroscopy.Results The content of aroma components showed significant differences between Gudao and Longji Pu-erh raw tea. The aroma components having “smell of cigarettes” included hexanal, camphene, benzaldehyde, benzyl alcohol,α-pinene, hotrienol, isoborneol, naphthalene, benzeneacetaldehyde, safranal, 3-carene, 2-methyl naphthalene, indole, 1-methylnaphthalene, 2-vinyl naphthalene, 1,3-dimethyl naphthalene, dihydroactinidiolide, phenanthrene, naphthalene,α-farnesene, icosane, bornyl acetate, n-tetradecane, ene terpenoids and so on, especially the linalool and its oxides. After the negative oxygen ion storage, the smoke substances descend obviously, which could significantly improve the overall taste.Conclusion The negative oxygen ion storage can significantly improve the quality of Pu-erh raw tea.%目的:提升有益内含香气成分和降低茶叶“烟味”杂异味以及提高生茶整体品质。方法采用蒸馏萃取法(simultaneous distillation extraction, SDE)富集其香气物质,并采用气相色谱-质谱联用法对负氧离子仓储前后普洱生茶进行香气成分对比和分析。结果2003年的龙记生饼和2005年的古道生饼香气物质含量呈现很大差异。其中正己醛、莰烯、苯甲醛、苯甲醇、α-蒎烯、脱氢芳樟醇、异龙脑、萘、苯乙醛、藏花醛、3-蒈烯、2-甲基萘、吲哚、1-甲基萘、2-乙烯基萘、1,3-二甲基萘、二氢猕猴桃内酯、菲、萘、α-法呢烯、正二十烷、乙酸冰片酯、十四烷、烯萜类等物质存在“烟味”,芳樟醇及其氧化物突出。经过负

  16. Combination of volatile and non-volatile functions in a single memory cell and its scalability

    Science.gov (United States)

    Kim, Hyungjin; Hwang, Sungmin; Lee, Jong-Ho; Park, Byung-Gook

    2017-04-01

    A single memory cell which combines volatile memory and non-volatile memory functions has been demonstrated with an independent asymmetric dual-gate structure. Owing to the second gate whose dielectric is composed of oxide/nitride/oxide layers, floating body effect was observed even on a fully depleted silicon-on-insulator device and the non-volatile memory function was measured. In addition, read retention characteristics of the volatile memory function depending on the non-volatile memory state were evaluated and analyzed. Further scalability in body thickness was also verified through simulation studies. These results indicate that the proposed device is a promising candidate for high-density embedded memory applications.

  17. Implicit Volatility versus Statistical Volatility: an Exercise Using Options and Telemar S.A. Stock

    Directory of Open Access Journals (Sweden)

    Marcelo Savino Portugal

    2004-06-01

    Full Text Available The main goal this article was to find the best way of making forecast about future volatility using implicit or statistic forecast. The work is based on Telemar S.A. shares data from 21/09/1998 to 21/10/2002 and Telemar S.A. shares data from 2/10/2000 to 21/10/2002. The implicit volatility was obtained using back-out procedure from the Black-Scholes model. The statistics forecasts were obtained using weighted moving average models, GARCH, EGARCH and FIGARCH models. The Wald statistic shows that EGARCH and FIGARCH models are efficient and are not biased forecasts for Telemar S.A. absolute variation between t and t + 1. The volatility evaluation during the maturity time of an option, rejects the hypothesis that implicit volatility is the best forecast to future volatility and the Wald statistic show that FIGARCH model is an efficient and not biased forecast.

  18. Effects of ascorbic acid and antioxidants on color, lipid oxidation and volatiles of irradiated ground beef

    Science.gov (United States)

    Ahn, D. U.; Nam, K. C.

    2004-09-01

    Beef loins with 3 different aging times after slaughter were ground, added with none, 0.1% ascorbic acid, 0.01% sesamol+0.01% α-tocopherol, or 0.1% ascorbic acid+0.01% sesamol+0.01% tocopherol. The meats were packaged in oxygen-permeable bags, irradiated at 2.5 kGy, and color, oxidation-reduction potential (ORP), lipid oxidation and volatile profiles were determined. Irradiation decreased the redness of ground beef, and visible color of beef changed from a bright red to a green/brown depending on the age of meat. Addition of ascorbic acid prevented color changes in irradiated beef, and the effect of ascorbic acid became greater as the age of meat or storage time after irradiation increased. The ground beef added with ascorbic acid had lower ORP than control, and the low ORP of meat helped maintaining the heme pigments in reduced form. During aerobic storage, S-volatiles disappeared while volatile aldehydes significantly increased in irradiated beef. Addition of ascorbic acid at 0.1% or sesamol+α-tocopherol at each 0.01% level to ground beef prior to irradiation were effective in reducing lipid oxidation and S-volatiles. As storage time increased, however, the antioxidant effect of sesamol+tocopherol in irradiated ground beef was superior to that of ascorbic acid.

  19. Effects of ascorbic acid and antioxidants on color, lipid oxidation and volatiles of irradiated ground beef

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, D.U. E-mail: duahn@iastate.edu; Nam, K.C

    2004-10-01

    Beef loins with 3 different aging times after slaughter were ground, added with none, 0.1% ascorbic acid, 0.01% sesamol+0.01% {alpha}-tocopherol, or 0.1% ascorbic acid+0.01% sesamol+0.01% tocopherol. The meats were packaged in oxygen-permeable bags, irradiated at 2.5 kGy, and color, oxidation-reduction potential (ORP), lipid oxidation and volatile profiles were determined. Irradiation decreased the redness of ground beef, and visible color of beef changed from a bright red to a green/brown depending on the age of meat. Addition of ascorbic acid prevented color changes in irradiated beef, and the effect of ascorbic acid became greater as the age of meat or storage time after irradiation increased. The ground beef added with ascorbic acid had lower ORP than control, and the low ORP of meat helped maintaining the heme pigments in reduced form. During aerobic storage, S-volatiles disappeared while volatile aldehydes significantly increased in irradiated beef. Addition of ascorbic acid at 0.1% or sesamol+{alpha}-tocopherol at each 0.01% level to ground beef prior to irradiation were effective in reducing lipid oxidation and S-volatiles. As storage time increased, however, the antioxidant effect of sesamol+tocopherol in irradiated ground beef was superior to that of ascorbic acid.

  20. Effects of gamma irradiation on the yields of volatile extracts of Angelica gigas Nakai

    Energy Technology Data Exchange (ETDEWEB)

    Seo, Hye-Young; Kim, Jun-Hyoung [Department of Food and Nutrition, Chosun University, Gwangju 501-759 (Korea, Republic of); Song, Hyun-Pa; Kim, Dong-Ho; Byun, Myung-Woo [Radiation Food Science and Biotechnology Team, Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Kwon, Joog-Ho [Department of Food Science and Technology, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Kim, Kyong-Su [Department of Food and Nutrition, Chosun University, Gwangju 501-759 (Korea, Republic of)], E-mail: kskim@chosun.ac.kr

    2007-11-15

    The study was carried out to determine the effects of gamma irradiation on the volatile flavor components including essential oils, of Angelica gigas Nakai. The volatile organic compounds from non- and irradiated A. gigas Nakai at doses of 1, 3, 5, 10 and 20 kGy were extracted by a simultaneous steam distillation and extraction (SDE) method and identified by GC/MS analysis. A total of 116 compounds were identified and quantified from non- and irradiated A. gigas Nakai. The major volatile compounds were identified 2,4,6-trimethyl heptane, {alpha}-pinene, camphene, {alpha}-limonene, {beta}-eudesmol, {alpha}-murrolene and sphatulenol. Among these compounds, the amount of essential oils in non-irradiated sample were 77.13%, and the irradiated samples at doses of 1, 3, 5, 10 and 20 kGy were 84.98%, 83.70%, 83.94%, 82.84% and 82.58%, respectively. Oxygenated terpenes such as {beta}-eudesmol, {alpha}-eudesmol, and verbenone were increased after irradiation but did not correlate with the irradiation dose. The yields of active substances such as essential oil were increased after irradiation; however, the yields of essential oils and the irradiation dose were not correlated. Thus, the profile of composition volatiles of A. gigas Nakai did not change with irradiation.

  1. Effects of gamma irradiation on the yields of volatile extracts of Angelica gigas Nakai

    Science.gov (United States)

    Seo, Hye-Young; Kim, Jun-Hyoung; Song, Hyun-Pa; Kim, Dong-Ho; Byun, Myung-Woo; Kwon, Joog-Ho; Kim, Kyong-Su

    2007-11-01

    The study was carried out to determine the effects of gamma irradiation on the volatile flavor components including essential oils, of Angelica gigas Nakai. The volatile organic compounds from non- and irradiated A. gigas Nakai at doses of 1, 3, 5, 10 and 20 kGy were extracted by a simultaneous steam distillation and extraction (SDE) method and identified by GC/MS analysis. A total of 116 compounds were identified and quantified from non- and irradiated A. gigas Nakai. The major volatile compounds were identified 2,4,6-trimethyl heptane, α-pinene, camphene, α-limonene, β-eudesmol, α-murrolene and sphatulenol. Among these compounds, the amount of essential oils in non-irradiated sample were 77.13%, and the irradiated samples at doses of 1, 3, 5, 10 and 20 kGy were 84.98%, 83.70%, 83.94%, 82.84% and 82.58%, respectively. Oxygenated terpenes such as β-eudesmol, α-eudesmol, and verbenone were increased after irradiation but did not correlate with the irradiation dose. The yields of active substances such as essential oil were increased after irradiation; however, the yields of essential oils and the irradiation dose were not correlated. Thus, the profile of composition volatiles of A. gigas Nakai did not change with irradiation.

  2. Thermogenic respiratory processes drive the exponential increase of volatile organic compound emissions in Macrozamia cycad cones.

    Science.gov (United States)

    Terry, L Irene; Roemer, Robert B; Booth, David T; Moore, Chris J; Walter, Gimme H

    2016-07-01

    An important outcome of plant thermogenesis is increased emissions of volatiles that mediate pollinator behaviour. We investigated whether the large increase in emissions, mainly the monoterpene ß-myrcene (>90%), during daily thermogenic events of Macrozamia macleayi and lucida cycad cones are due solely to the influence of high cone temperatures or are, instead, a result of increased respiratory rates during thermogenesis. We concurrently measured temperature, oxygen consumption and ß-myrcene emission profiles during thermogenesis of pollen cones under typical environmental temperatures and during experimental manipulations of cone temperatures and aerobic conditions, all in the dark. The exponential rise in ß-myrcene emissions never occurred without a prior, large increase in respiration, whereas an increase in cone temperature alone did not increase emissions. When respiration during thermogenesis was interrupted by anoxic conditions, ß-myrcene emissions decreased. The increased emission rates are not a result of increased cone temperature per se (through increased enzyme activity or volatilization of stored volatiles) but are dependent on biosynthetic pathways associated with increased respiration during thermogenesis that provide the carbon, energy (ATP) and reducing compounds (NADPH) required for ß-myrcene production through the methylerythritol phosphate (MEP) pathway. These findings establish the significant contribution of respiration to volatile production during thermogenesis.

  3. Optimal directional volatile transport in retronasal olfaction

    Science.gov (United States)

    Ni, Rui; Michalski, Mark H.; Brown, Elliott; Doan, Ngoc; Zinter, Joseph; Ouellette, Nicholas T.; Shepherd, Gordon M.

    2015-01-01

    The ability of humans to distinguish the delicate differences in food flavors depends mostly on retronasal smell, in which food volatiles entrained into the airway at the back of the oral cavity are transported by exhaled air through the nasal cavity to stimulate the olfactory receptor neurons. Little is known whether food volatiles are preferentially carried by retronasal flow toward the nasal cavity rather than by orthonasal flow into the lung. To study the differences between retronasal and orthonasal flow, we obtained computed tomography (CT) images of the orthonasal airway from a healthy human subject, printed an experimental model using a 3D printer, and analyzed the flow field inside the airway. The results show that, during inhalation, the anatomical structure of the oropharynx creates an air curtain outside a virtual cavity connecting the oropharynx and the back of the mouth, which prevents food volatiles from being transported into the main stream toward the lung. In contrast, during exhalation, the flow preferentially sweeps through this virtual cavity and effectively enhances the entrainment of food volatiles into the main retronasal flow. This asymmetrical transport efficiency is also found to have a nonmonotonic Reynolds number dependence: The asymmetry peaks at a range of an intermediate Reynolds number close to 800, because the air curtain effect during inhalation becomes strongest in this range. This study provides the first experimental evidence, to our knowledge, for adaptations of the geometry of the human oropharynx for efficient transport of food volatiles toward the olfactory receptors in the nasal cavity. PMID:26553982

  4. A bacterial volatile signal for biofilm formation

    Directory of Open Access Journals (Sweden)

    Yun Chen

    2015-09-01

    Full Text Available Bacteria constantly monitor the environment they reside in and respond to potential changes in the environment through a variety of signal sensing and transduction mechanisms in a timely fashion. Those signaling mechanisms often involve application of small, diffusible chemical molecules. Volatiles are a group of small air-transmittable chemicals that are produced universally by all kingdoms of organisms. Past studies have shown that volatiles can function as cell-cell communication signals not only within species, but also cross-species. However, little is known about how the volatile-mediated signaling mechanism works. In our recent study (Chen, et al. mBio (2015, 6: e00392-15, we demonstrated that the soil bacterium Bacillus subtilis uses acetic acid as a volatile signal to coordinate the timing of biofilm formation within physically separated cells in the community. We also showed that the bacterium possesses an intertwined gene network to produce, secrete, sense, and respond to acetic acid, in stimulating biofilm formation. Interestingly, many of those genes are highly conserved in other bacterial species, raising the possibility that acetic acid may act as a volatile signal for cross-species communication.

  5. A bacterial volatile signal for biofilm formation

    Science.gov (United States)

    Chen, Yun; Gozzi, Kevin; Chai, Yunrong

    2015-01-01

    Bacteria constantly monitor the environment they reside in and respond to potential changes in the environment through a variety of signal sensing and transduction mechanisms in a timely fashion. Those signaling mechanisms often involve application of small, diffusible chemical molecules. Volatiles are a group of small air-transmittable chemicals that are produced universally by all kingdoms of organisms. Past studies have shown that volatiles can function as cell-cell communication signals not only within species, but also cross-species. However, little is known about how the volatile-mediated signaling mechanism works. In our recent study (Chen, et al. mBio (2015), 6: e00392-15), we demonstrated that the soil bacterium Bacillus subtilis uses acetic acid as a volatile signal to coordinate the timing of biofilm formation within physically separated cells in the community. We also showed that the bacterium possesses an intertwined gene network to produce, secrete, sense, and respond to acetic acid, in stimulating biofilm formation. Interestingly, many of those genes are highly conserved in other bacterial species, raising the possibility that acetic acid may act as a volatile signal for cross-species communication.

  6. Modeling and forecasting petroleum futures volatility

    Energy Technology Data Exchange (ETDEWEB)

    Sadorsky, Perry [York Univ., Schulich School of Business, Toronto, ON (Canada)

    2006-07-15

    Forecasts of oil price volatility are important inputs into macroeconometric models, financial market risk assessment calculations like value at risk, and option pricing formulas for futures contracts. This paper uses several different univariate and multivariate statistical models to estimate forecasts of daily volatility in petroleum futures price returns. The out-of-sample forecasts are evaluated using forecast accuracy tests and market timing tests. The TGARCH model fits well for heating oil and natural gas volatility and the GARCH model fits well for crude oil and unleaded gasoline volatility. Simple moving average models seem to fit well in some cases provided the correct order is chosen. Despite the increased complexity, models like state space, vector autoregression and bivariate GARCH do not perform as well as the single equation GARCH model. Most models out perform a random walk and there is evidence of market timing. Parametric and non-parametric value at risk measures are calculated and compared. Non-parametric models outperform the parametric models in terms of number of exceedences in backtests. These results are useful for anyone needing forecasts of petroleum futures volatility. (author)

  7. A conservative discontinuous target volatility strategy

    Directory of Open Access Journals (Sweden)

    Simone Cirelli

    2017-07-01

    Full Text Available The asset management sector is constantly looking for a reliable investment strategy, which is able to keep its promises. One of the most used approaches is the target volatility strategy that combines a risky asset with a risk-free trying to maintain the portfolio volatility constant over time. Several analyses highlight that such target is fulfilled on average, but in periods of crisis, the portfolio still suffers market’s turmoils. In this paper, the authors introduce an innovative target volatility strategy: the discontinuous target volatility. Such approach turns out to be more conservative in high volatility periods. Moreover, the authors compare the adoption of the VIX Index as a risk measure instead of the classical standard deviation and show whether the former is better than the latter. In the last section, the authors also extend the analysis to remove the risk-free assumption and to include the correlation structure between two risky assets. Empirical results on a wide time span show the capability of the new proposed strategy to enhance the portfolio performance in terms of standard measures and according to stochastic dominance theory.

  8. Optimal directional volatile transport in retronasal olfaction.

    Science.gov (United States)

    Ni, Rui; Michalski, Mark H; Brown, Elliott; Doan, Ngoc; Zinter, Joseph; Ouellette, Nicholas T; Shepherd, Gordon M

    2015-11-24

    The ability of humans to distinguish the delicate differences in food flavors depends mostly on retronasal smell, in which food volatiles entrained into the airway at the back of the oral cavity are transported by exhaled air through the nasal cavity to stimulate the olfactory receptor neurons. Little is known whether food volatiles are preferentially carried by retronasal flow toward the nasal cavity rather than by orthonasal flow into the lung. To study the differences between retronasal and orthonasal flow, we obtained computed tomography (CT) images of the orthonasal airway from a healthy human subject, printed an experimental model using a 3D printer, and analyzed the flow field inside the airway. The results show that, during inhalation, the anatomical structure of the oropharynx creates an air curtain outside a virtual cavity connecting the oropharynx and the back of the mouth, which prevents food volatiles from being transported into the main stream toward the lung. In contrast, during exhalation, the flow preferentially sweeps through this virtual cavity and effectively enhances the entrainment of food volatiles into the main retronasal flow. This asymmetrical transport efficiency is also found to have a nonmonotonic Reynolds number dependence: The asymmetry peaks at a range of an intermediate Reynolds number close to 800, because the air curtain effect during inhalation becomes strongest in this range. This study provides the first experimental evidence, to our knowledge, for adaptations of the geometry of the human oropharynx for efficient transport of food volatiles toward the olfactory receptors in the nasal cavity.

  9. 42 CFR 414.226 - Oxygen and oxygen equipment.

    Science.gov (United States)

    2010-10-01

    ... 42 Public Health 3 2010-10-01 2010-10-01 false Oxygen and oxygen equipment. 414.226 Section 414... Equipment and Prosthetic and Orthotic Devices § 414.226 Oxygen and oxygen equipment. (a) Payment rules—(1) Oxygen equipment. Payment for rental of oxygen equipment is made based on a monthly fee schedule...

  10. Removal Of Volatile Impurities From Copper Concentrates

    Energy Technology Data Exchange (ETDEWEB)

    Winkel, L.; Schuler, A.; Frei, A.; Sturzenegger, M.

    2005-03-01

    To study the removal of volatile impurities from two different copper concentrates they have been heated on a thermo balance to temperatures between 900 and 1500 C. This sample treatment revealed that both concentrates undergo strong weight losses at 500 and 700 C. They were attributed to the removal of sulfur. Elemental analyses of the residues by ICP spectrometry have shown that the thermal treatment efficiently removes the volatile impurities. Already below 900 C most of the arsenic is removed by evaporation, the largest fraction of lead and zinc is removed in the temperature interval of 1300-1500 C. It was observed that quartz in the concentrate leads to the formation of a silicon-enriched phase besides a metal rich sulfide phase. The former is interpreted as an early stage of a silicate slag. Elemental analysis showed that the formation of this distinct slag phase does not hinder the efficient removal of volatile impurities. (author)

  11. Volatility jumps and their economic determinants

    DEFF Research Database (Denmark)

    Caporin, Massimiliano; Rossi, Eduardo; Santucci de Magistris, Paolo

    that there is a positive probability of jumps in volatility. A common factor in the volatility jumps is shown to be related to a set of financial covariates (such as variance risk premium, S&P500 volume, credit-default swap, and federal fund rates). The credit-default swap on US banks and variance risk premium have...... predictive power on expected jump moves, thus confirming the common interpretation that sudden and large increases in equity volatility can be anticipated by credit deterioration of the US bank sector as well as changes in the market expectations of future risks. Finally, the model is extended to incorporate...... the credit-default swap and the variance risk premium in the dynamics of the jump size and intensity....

  12. Dynamic Factor Models for the Volatility Surface

    DEFF Research Database (Denmark)

    van der Wel, Michel; Ozturk, Sait R.; Dijk, Dick van

    The implied volatility surface is the collection of volatilities implied by option contracts for different strike prices and time-to-maturity. We study factor models to capture the dynamics of this three-dimensional implied volatility surface. Three model types are considered to examine desirable...... features for representing the surface and its dynamics: a general dynamic factor model, restricted factor models designed to capture the key features of the surface along the moneyness and maturity dimensions, and in-between spline-based methods. Key findings are that: (i) the restricted and spline......-based models are both rejected against the general dynamic factor model, (ii) the factors driving the surface are highly persistent, (iii) for the restricted models option Delta is preferred over the more often used strike relative to spot price as measure for moneyness....

  13. The volatility of stock market prices.

    Science.gov (United States)

    Shiller, R J

    1987-01-02

    If the volatility of stock market prices is to be understood in terms of the efficient markets hypothesis, then there should be evidence that true investment value changes through time sufficiently to justify the price changes. Three indicators of change in true investment value of the aggregate stock market in the United States from 1871 to 1986 are considered: changes in dividends, in real interest rates, and in a direct measure of intertemporal marginal rates of substitution. Although there are some ambiguities in interpreting the evidence, dividend changes appear to contribute very little toward justifying the observed historical volatility of stock prices. The other indicators contribute some, but still most of the volatility of stock market prices appears unexplained.

  14. Volatile components and continental material of planets

    Science.gov (United States)

    Florenskiy, K. P.; Nikolayeva, O. V.

    1986-01-01

    It is shown that the continental material of the terrestrial planets varies in composition from planet to planet according to the abundances and composition of true volatiles (H20, CO2, etc.) in the outer shells of the planets. The formation of these shells occurs very early in a planet's evolution when the role of endogenous processes is indistinct and continental materials are subject to melting and vaporizing in the absence of an atmosphere. As a result, the chemical properties of continental materials are related not only to fractionation processes but also to meltability and volatility. For planets retaining a certain quantity of true volatile components, the chemical transformation of continental material is characterized by a close interaction between impact melting vaporization and endogeneous geological processes.

  15. Volatile species retention during metallic fuel casting

    Science.gov (United States)

    Fielding, Randall S.; Porter, Douglas L.

    2013-10-01

    Metallic nuclear fuels are candidate transmutation fuel forms for advanced fuel cycles. Through the operation of the Experimental Breeder Reactor II metallic nuclear fuels have been shown to be robust and easily manufactured. However, concerns have been raised concerning loss of americium during the casting process because of its high vapor pressure. In order to address these concerns a gaseous diffusion model was developed and a series of experiments using both manganese and samarium as surrogates for americium were conducted. The modeling results showed that volatility losses can be controlled to essentially no losses with a modest overpressure. Experimental results also showed volatile species retention down to no detectable losses through overpressure, and although the loss values varied from the model results the same trend was seen. Based on these results it is very probable that americium losses through volatility can be controlled to no detectable losses through application of a modest overpressure during casting.

  16. The Volatility and condensation behaviour of elements in dependence of T and fO2: a novel experimental approach

    Science.gov (United States)

    Ertel-Ingrisch, Werner; Dingwell, Don B.

    2010-05-01

    The volatility of elements is one of the most important variables during geological processes on Earth: its impact ranges from daily out gassing of volcanic vents to catastrophic emissions during volcanic eruptions which might scale up to global impacts on our climate. Volatility played, however, already a major role during the formation of our solar system: the nebular gases and their element budget passed through an elemental fractionation process based on differences in the evaporation and condensation behaviour of matter within the solar nebula - the origin of all the planets within our solar system. Precise knowledge of the parameters controlling volatility as well as condensation of elements is still lacking. Whether an element behaves volatile or refractory depends highly on the temperature and oxygen fugacity (fO2) conditions prevailing. To address this issue, we initiated a systematic study of the volatility of 18 volatile elements in respect to fO2 and temperature applying a modified mechanically assisted equilibration technique (MAE): Approx. 60 g of a haplobasaltic starting composition (An-Di) doped with up to 5000 ppm of volatile elements (Li, K, Na, Ti, Cr, Mn, Co, Cu, Cu, Zn, Ga, Rb, Cd, In, Sn, Sb, Cs, Tl) was heated to run temperatures. To investigate the fO2 dependence 2 experiments at logfO2 = -11.3 (~ IW -0.5) and - 0,7 (pure air) at a constant temperature of 1300 °C were performed, while T dependence was investigated at 1300 and 1500 °C at constant fO2 in pure air. The original MAE technique was modified by two Al2O3 plates extending from the hot spot region up to the upper, cooler regions of the muffle tube. These plates function as condensation traps. The temperature profile of the entire setup including the Al2O3 plates under run conditions was calibrated prior to any run. Experiments lasted for up two weeks while experimental conditions were kept strictly constant and were monitored. Up to 46 samples were taken from the melt by time

  17. Changes in dark chocolate volatiles during storage.

    Science.gov (United States)

    Nightingale, Lia M; Cadwallader, Keith R; Engeseth, Nicki J

    2012-05-09

    Chocolate storage is critical to the quality of the final product. Inadequate storage, especially with temperature fluctuations, may lead to a change in crystal structure, which may eventually cause fat bloom. Bloom is the main cause of quality loss in the chocolate industry. The impact of various storage conditions on the flavor quality of dark chocolate was determined. Dark chocolate was stored in different conditions leading to either fat or sugar bloom and analyzed at 0, 4, and 8 weeks of storage. Changes in chocolate flavor were determined by volatile analysis and descriptive sensory evaluation. Results were analyzed by analysis of variance (ANOVA), cluster analysis, principal component analysis (PCA), and linear partial least-squares regression analysis (PLS). Volatile concentration and loss were significantly affected by storage conditions. Chocolates stored at high temperature were the most visually and texturally compromised, but volatile concentrations were affected the least, whereas samples stored at ambient, frozen, and high relative humidity conditions had significant volatile loss during storage. It was determined that high-temperature storage caused a change in crystal state due to the polymorphic shift to form VI, leading to an increase in sample hardness. Decreased solid fat content (SFC) during high-temperature storage increased instrumentally determined volatile retention, although no difference was detected in chocolate flavor during sensory analysis, possibly due to instrumental and sensory sampling techniques. When all instrumental and sensory data had been taken into account, the storage condition that had the least impact on texture, surface roughness, grain size, lipid polymorphism, fat bloom formation, volatile concentrations, and sensory attributes was storage at constant temperature and 75% relative humidity.

  18. Different methods for volatile sampling in mammals.

    Science.gov (United States)

    Kücklich, Marlen; Möller, Manfred; Marcillo, Andrea; Einspanier, Almuth; Weiß, Brigitte M; Birkemeyer, Claudia; Widdig, Anja

    2017-01-01

    Previous studies showed that olfactory cues are important for mammalian communication. However, many specific compounds that convey information between conspecifics are still unknown. To understand mechanisms and functions of olfactory cues, olfactory signals such as volatile compounds emitted from individuals need to be assessed. Sampling of animals with and without scent glands was typically conducted using cotton swabs rubbed over the skin or fur and analysed by gas chromatography-mass spectrometry (GC-MS). However, this method has various drawbacks, including a high level of contaminations. Thus, we adapted two methods of volatile sampling from other research fields and compared them to sampling with cotton swabs. To do so we assessed the body odor of common marmosets (Callithrix jacchus) using cotton swabs, thermal desorption (TD) tubes and, alternatively, a mobile GC-MS device containing a thermal desorption trap. Overall, TD tubes comprised most compounds (N = 113), with half of those compounds being volatile (N = 52). The mobile GC-MS captured the fewest compounds (N = 35), of which all were volatile. Cotton swabs contained an intermediate number of compounds (N = 55), but very few volatiles (N = 10). Almost all compounds found with the mobile GC-MS were also captured with TD tubes (94%). Hence, we recommend TD tubes for state of the art sampling of body odor of mammals or other vertebrates, particularly for field studies, as they can be easily transported, stored and analysed with high performance instruments in the lab. Nevertheless, cotton swabs capture compounds which still may contribute to the body odor, e.g. after bacterial fermentation, while profiles from mobile GC-MS include only the most abundant volatiles of the body odor.

  19. Different methods for volatile sampling in mammals

    Science.gov (United States)

    Möller, Manfred; Marcillo, Andrea; Einspanier, Almuth; Weiß, Brigitte M.

    2017-01-01

    Previous studies showed that olfactory cues are important for mammalian communication. However, many specific compounds that convey information between conspecifics are still unknown. To understand mechanisms and functions of olfactory cues, olfactory signals such as volatile compounds emitted from individuals need to be assessed. Sampling of animals with and without scent glands was typically conducted using cotton swabs rubbed over the skin or fur and analysed by gas chromatography-mass spectrometry (GC-MS). However, this method has various drawbacks, including a high level of contaminations. Thus, we adapted two methods of volatile sampling from other research fields and compared them to sampling with cotton swabs. To do so we assessed the body odor of common marmosets (Callithrix jacchus) using cotton swabs, thermal desorption (TD) tubes and, alternatively, a mobile GC-MS device containing a thermal desorption trap. Overall, TD tubes comprised most compounds (N = 113), with half of those compounds being volatile (N = 52). The mobile GC-MS captured the fewest compounds (N = 35), of which all were volatile. Cotton swabs contained an intermediate number of compounds (N = 55), but very few volatiles (N = 10). Almost all compounds found with the mobile GC-MS were also captured with TD tubes (94%). Hence, we recommend TD tubes for state of the art sampling of body odor of mammals or other vertebrates, particularly for field studies, as they can be easily transported, stored and analysed with high performance instruments in the lab. Nevertheless, cotton swabs capture compounds which still may contribute to the body odor, e.g. after bacterial fermentation, while profiles from mobile GC-MS include only the most abundant volatiles of the body odor. PMID:28841690

  20. Integrated turbomachine oxygen plant

    Science.gov (United States)

    Anand, Ashok Kumar; DePuy, Richard Anthony; Muthaiah, Veerappan

    2014-06-17

    An integrated turbomachine oxygen plant includes a turbomachine and an air separation unit. One or more compressor pathways flow compressed air from a compressor through one or more of a combustor and a turbine expander to cool the combustor and/or the turbine expander. An air separation unit is operably connected to the one or more compressor pathways and is configured to separate the compressed air into oxygen and oxygen-depleted air. A method of air separation in an integrated turbomachine oxygen plant includes compressing a flow of air in a compressor of a turbomachine. The compressed flow of air is flowed through one or more of a combustor and a turbine expander of the turbomachine to cool the combustor and/or the turbine expander. The compressed flow of air is directed to an air separation unit and is separated into oxygen and oxygen-depleted air.

  1. Ambient oxygen promotes tumorigenesis.

    Directory of Open Access Journals (Sweden)

    Ho Joong Sung

    Full Text Available Oxygen serves as an essential factor for oxidative stress, and it has been shown to be a mutagen in bacteria. While it is well established that ambient oxygen can also cause genomic instability in cultured mammalian cells, its effect on de novo tumorigenesis at the organismal level is unclear. Herein, by decreasing ambient oxygen exposure, we report a ∼50% increase in the median tumor-free survival time of p53-/- mice. In the thymus, reducing oxygen exposure decreased the levels of oxidative DNA damage and RAG recombinase, both of which are known to promote lymphomagenesis in p53-/- mice. Oxygen is further shown to be associated with genomic instability in two additional cancer models involving the APC tumor suppressor gene and chemical carcinogenesis. Together, these observations represent the first report directly testing the effect of ambient oxygen on de novo tumorigenesis and provide important physiologic evidence demonstrating its critical role in increasing genomic instability in vivo.

  2. Volatile compound formation during argan kernel roasting.

    Science.gov (United States)

    El Monfalouti, Hanae; Charrouf, Zoubida; Giordano, Manuela; Guillaume, Dominique; Kartah, Badreddine; Harhar, Hicham; Gharby, Saïd; Denhez, Clément; Zeppa, Giuseppe

    2013-01-01

    Virgin edible argan oil is prepared by cold-pressing argan kernels previously roasted at 110 degrees C for up to 25 minutes. The concentration of 40 volatile compounds in virgin edible argan oil was determined as a function of argan kernel roasting time. Most of the volatile compounds begin to be formed after 15 to 25 minutes of roasting. This suggests that a strictly controlled roasting time should allow the modulation of argan oil taste and thus satisfy different types of consumers. This could be of major importance considering the present booming use of edible argan oil.

  3. Local Volatility Calibration Using An Adjoint Proxy

    Directory of Open Access Journals (Sweden)

    Gabriel TURINICI

    2008-11-01

    Full Text Available We document the calibration of the local volatility in a framework similar to Coleman, Li and Verma. The quality of a surface is assessed through a functional to be optimized; the specificity of the approach is to separate the optimization (performed with any suitable optimization algorithm from the computation of the functional where we use an adjoint (as in L. Jiang et. al. to obtain an approximation; moreover our main calibration variable is the implied volatility (the procedure can also accommodate the Greeks. The procedure performs well on benchmarks from the literature and on FOREX data.

  4. Solid state oxygen sensor

    Science.gov (United States)

    Garzon, F.H.; Brosha, E.L.

    1997-12-09

    A potentiometric oxygen sensor is formed having a logarithmic response to a differential oxygen concentration while operating as a Nernstian-type sensor. Very thin films of mixed conducting oxide materials form electrode services while permitting diffusional oxygen access to the interface between the zirconia electrolyte and the electrode. Diffusion of oxygen through the mixed oxide is not rate-limiting. Metal electrodes are not used so that morphological changes in the electrode structure do not occur during extended operation at elevated temperatures. 6 figs.

  5. Measuring tissue oxygenation

    Science.gov (United States)

    Soyemi, Olusola O. (Inventor); Soller, Babs R. (Inventor); Yang, Ye (Inventor)

    2009-01-01

    Methods and systems for calculating tissue oxygenation, e.g., oxygen saturation, in a target tissue are disclosed. In some embodiments, the methods include: (a) directing incident radiation to a target tissue and determining reflectance spectra of the target tissue by measuring intensities of reflected radiation from the target tissue at a plurality of radiation wavelengths; (b) correcting the measured intensities of the reflectance spectra to reduce contributions thereto from skin and fat layers through which the incident radiation propagates; (c) determining oxygen saturation in the target tissue based on the corrected reflectance spectra; and (d) outputting the determined value of oxygen saturation.

  6. Correlation between volatile profiles of Italian fermented sausages and their size and starter culture.

    Science.gov (United States)

    Montanari, Chiara; Bargossi, Eleonora; Gardini, Aldo; Lanciotti, Rosalba; Magnani, Rudy; Gardini, Fausto; Tabanelli, Giulia

    2016-02-01

    The aroma profiles of 10 traditional Italian fermented sausages were evaluated. The volatile organic compounds (VOCs) obtained by solid-phase microextraction and gas chromatograph-mass spectrometry were analysed using principal component analysis (PCA) and linear discriminant analysis (LDA). PCA allowed an acceptable separation but some sausage typologies were not well separated. On the other hand, the supervised approach of LDA allowed a clear grouping of the samples in relation to sausage size and starter culture. In spite of the extreme variability of the volatile profiles of the sausage typologies, this work showed the influence of diameter on VOC profile. The differences observed can be related to the effects that some fundamental physicochemical characteristics (such as water loss kinetics and oxygen availability) have on the results of ripening processes. Differences in VOC profiles were also observed due to the lactic acid bacteria used as starter cultures, with differences mainly attributable to compounds deriving from pyruvate metabolism.

  7. Volatile organic compounds and Photobacterium phosphoreum associated with spoilage of modified-atmosphere-packaged raw pork

    DEFF Research Database (Denmark)

    Nieminen, Timo T.; Dalgaard, Paw; Björkroth, Johanna

    2016-01-01

    Accumulation of volatile organic compounds was monitored in association with sensory quality, bacterial concentrations and culture-independent microbial community analyses in raw pork loin and pork collar during storage under high-oxygen modified atmosphere at +4°C. Of the 48 volatile compounds....... According to the culture-dependent and culture-independent characterization of bacterial communities, Brochothrix thermosphacta, lactic acid bacteria (Carnobacterium, Lactobacillus, Lactococcus, Leuconostoc, Weissella) and Photobacterium spp. predominated in pork samples. Photobacterium spp., typically...... not associated with spoilage of meat, were detected also in 8 of the 11 retail packages of pork investigated subsequently. Eleven isolates from the pork samples were shown to belong to Photobacterium phosphoreum by phenotypic tests and sequencing of the 16S rRNA and gyrB gene fragments. Off-odors in pork samples...

  8. Electroantennogram responses of the potato tuber moth, Phthorimaea operculella (Lepidoptera; Gelichiidae) to plant volatiles

    Indian Academy of Sciences (India)

    P D Das; R Raina; A R Prasad; A Sen

    2007-03-01

    Electroantennograms (EAGs) were recorded from males and females of the potato tuber moth, Phthorimaea operculella in response to a broad range of plant volatile compounds belonging to diverse chemical classes. The responses to 27 compounds were evaluated, which indicated significant differences in EAGs between chemicals as well as between sexes. The fatty acid derivatives comprising essentially green leaf volatile components elicited significantly greater responses in females. The response profile of males was, in general, lower than that of females. EAG responses to the oxygenated and hydrocarbon monoterpenes were lower in both males and females. Dose–response studies indicate differences in response between the sexes and concentrations, suggesting the existence of sexual dimorphism. Compounds belonging to the fatty acid derivatives class appear to be important for an oligophagous pest such as the potato tuber moth and the findings are discussed in relation to host plant selection in this species.

  9. Fundamental mechanisms for conversion of volatiles in biomass and waste combustion. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Glarborg, P.; Hindiyarti, L.; Marshall, P.; Livbjerg, H.; Dagaut, P.; Jensen, Anker; Frandsen, Flemming

    2007-03-15

    This project deals with the volatile oxidation chemistry in biomass and waste fired systems, emphasizing reactions important for pollutants emissions (NO{sub x}, SO{sub 2}, HCl, aerosols). The project aims to extend existing models and databases with a number of chemical subsystems that are presently not well understood, but are particularly important in connection with combustion of biomass and waste. The project is divided into 3 tasks. Task 1: Conversion of chlorine, sulfur and alkali gas phase components in combustion of biomass. Task 2: Formation mechanisms for NO{sub x} in the freeboard of grate combustion of biomass. Task 3: Oxidation mechanisms for oxygenated hydrocarbons in the volatiles from pyrolysis of biomass. (au)

  10. Loss of volatile hydrocarbons from an LNAPL oil source

    Science.gov (United States)

    Baedecker, M.J.; Eganhouse, R.P.; Bekins, B.A.; Delin, G.N.

    2011-01-01

    The light nonaqueous phase liquid (LNAPL) oil pool in an aquifer that resulted from a pipeline spill near Bemidji, Minnesota, was analyzed for volatile hydrocarbons (VHCs) to determine if the composition of the oil remains constant over time. Oil samples were obtained from wells at five locations in the oil pool in an anaerobic part of the glacial outwash aquifer. Samples covering a 21-year period were analyzed for 25 VHCs. Compared to the composition of oil from the pipeline source, VHCs identified in oil from wells sampled in 2008 were 13 to 64% depleted. The magnitude of loss for the VHCs analyzed was toluene ≫ o-xylene, benzene, C6 and C10–12n-alkanes > C7–C9n-alkanes > m-xylene, cyclohexane, and 1- and 2-methylnaphthalene > 1,2,4-trimethylbenzene and ethylbenzene. Other VHCs including p-xylene, 1,3,5- and 1,2,3-trimethylbenzenes, the tetramethylbenzenes, methyl- and ethyl-cyclohexane, and naphthalene were not depleted during the time of the study. Water–oil and air–water batch equilibration simulations indicate that volatilization and biodegradation is most important for the C6–C9n-alkanes and cyclohexanes; dissolution and biodegradation is important for most of the other hydrocarbons. Depletion of the hydrocarbons in the oil pool is controlled by: the lack of oxygen and nutrients, differing rates of recharge, and the spatial distribution of oil in the aquifer. The mass loss of these VHCs in the 5 wells is between 1.6 and 7.4% in 29 years or an average annual loss of 0.06–0.26%/year. The present study shows that the composition of LNAPL changes over time and that these changes are spatially variable. This highlights the importance of characterizing the temporal and spatial variabilities of the source term in solute-transport models.

  11. Loss of volatile hydrocarbons from an LNAPL oil source

    Science.gov (United States)

    Baedecker, Mary Jo; Eganhouse, Robert P.; Bekins, Barbara A.; Delin, Geoffrey N.

    2011-11-01

    The light nonaqueous phase liquid (LNAPL) oil pool in an aquifer that resulted from a pipeline spill near Bemidji, Minnesota, was analyzed for volatile hydrocarbons (VHCs) to determine if the composition of the oil remains constant over time. Oil samples were obtained from wells at five locations in the oil pool in an anaerobic part of the glacial outwash aquifer. Samples covering a 21-year period were analyzed for 25 VHCs. Compared to the composition of oil from the pipeline source, VHCs identified in oil from wells sampled in 2008 were 13 to 64% depleted. The magnitude of loss for the VHCs analyzed was toluene ≫ o-xylene, benzene, C 6 and C 10-12n-alkanes > C 7-C 9n-alkanes > m-xylene, cyclohexane, and 1- and 2-methylnaphthalene > 1,2,4-trimethylbenzene and ethylbenzene. Other VHCs including p-xylene, 1,3,5- and 1,2,3-trimethylbenzenes, the tetramethylbenzenes, methyl- and ethyl-cyclohexane, and naphthalene were not depleted during the time of the study. Water-oil and air-water batch equilibration simulations indicate that volatilization and biodegradation is most important for the C 6-C 9n-alkanes and cyclohexanes; dissolution and biodegradation is important for most of the other hydrocarbons. Depletion of the hydrocarbons in the oil pool is controlled by: the lack of oxygen and nutrients, differing rates of recharge, and the spatial distribution of oil in the aquifer. The mass loss of these VHCs in the 5 wells is between 1.6 and 7.4% in 29 years or an average annual loss of 0.06-0.26%/year. The present study shows that the composition of LNAPL changes over time and that these changes are spatially variable. This highlights the importance of characterizing the temporal and spatial variabilities of the source term in solute-transport models.

  12. Molecular cloning and characterization of a 3-hydroxy-3-methylglutaryl-coenzyme A reductase 1 (hmgr1) gene from rubber tree (Hevea brasiliensis Muell. Arg.): A key gene involved in isoprenoid biosynthesis.

    Science.gov (United States)

    Venkatachalam, P; Priya, P; Jayashree, R; Rekha, K; Thulaseedharan, A

    2009-04-01

    Natural rubber (cis-1,4-polyisoprene) is a secondary metabolite produced in the laticiferous tissue of Hevea tree. Mevalonate synthesis, which is the first step in isoprenoid biosynthesis, is catalyzed by the enzyme 3-hydroxy-3-methylglutarylcoenzyme A reductase 1 (hmgr1). We have cloned and characterized a full-length cDNA as well as genomic DNA for hmgr1 gene from an elite Indian rubber clone (RRII 105). The nucleotide sequence of the genomic clone comprises 4 exons and 3 introns, giving a total length of 2440 bp. The sequences of 42 bp 5' UTR and 69 bp of the 3' UTR were also determined. The hmgr1 cDNA contained an open reading frame of 1838 bp coding for 575 amino acid protein with a theoretical pI value of 6.6 and the calculated protein M W was 61.6 kDa. The deduced amino acid sequence showed high identity with other plant hmgr1 sequences. The amino acid sequence of the Hevea hmgr1 revealed several motifs which are highly conserved and common to the other plant species. These sequence conservations suggest a strong evolutionary pressure to maintain amino acid residues at specific positions, indicating that the conserved motifs might play important roles in the structural and/or catalytic properties of the enzyme. Southern blot analysis of genomic DNA from Hevea probed with a genomic fragment indicated that there were at least three isoforms of hmgr in Hevea. This result reveals that hmgr1 is one of the members of a small gene family. (Northern blot analysis showed that hmgr1 mRNA transcripts were noticed in all tissues - latex, leaf, immature leaf, and seedlings), however, the abundance of transcript level was higher in latex cells. As one step towards a better understanding of the role that this enzyme plays in coordinating isoprenoid biosynthesis in plants, hmgr1 cDNA was over expressed in transgenic Arabidopsis plants. Transgenic plants were morphologically distinguishable from control wild-type plants and an increased expression level of hmgr1 mRNA was

  13. Survey of Cold Water Lines in Protoplanetary Disks: Indications of Systematic Volatile Depletion

    Science.gov (United States)

    Du, Fujun; Bergin, Edwin Anthony; Hogerheijde, Michiel; van Dishoeck, Ewine F.; Blake, Geoff; Bruderer, Simon; Cleeves, Ilse; Dominik, Carsten; Fedele, Davide; Lis, Dariusz C.; Melnick, Gary; Neufeld, David; Pearson, John; Yıldız, Umut

    2017-06-01

    We performed very deep searches for 2 ground-state water transitions in 13 protoplanetary disks with the HIFI instrument on board the Herschel Space Observatory, with integration times up to 12 hr per line. We also searched for, with shallower integrations, two other water transitions that sample warmer gas. The detection rate is low, and the upper limits provided by the observations are generally much lower than predictions of thermo-chemical models with canonical inputs. One ground-state transition is newly detected in the stacked spectrum of AA Tau, DM Tau, LkCa 15, and MWC 480. We run a grid of models to show that the abundance of gas-phase oxygen needs to be reduced by a factor of at least ∼ 100 to be consistent with the observational upper limits (and positive detections) if a dust-to-gas mass ratio of 0.01 were to be assumed. As a continuation of previous ideas, we propose that the underlying reason for the depletion of oxygen (hence the low detection rate) is the freeze-out of volatiles such as water and CO onto dust grains followed by grain growth and settling/migration, which permanently removes these gas-phase molecules from the emissive upper layers of the outer disk. Such depletion of volatiles is likely ubiquitous among different disks, though not necessarily to the same degree. The volatiles might be returned back to the gas phase in the inner disk (≲ 15 au), which is consistent with current constraints. Comparison with studies on disk dispersal due to photoevaporation indicates that the timescale for volatile depletion is shorter than that of photoevaporation.

  14. Forecasting Exchange Rate Volatility in the Presence of Jumps

    DEFF Research Database (Denmark)

    Busch, Thomas; Christensen, Bent Jesper; Nielsen, Morten Ørregaard

    of exchange rate futures options, allowingcalculation of option implied volatility. We find that implied volatility is an informationallyefficient but biased forecast of future realized exchange rate volatility. Furthermore,we show that log-normality is an even better distributional approximation...... for impliedvolatility than for realized volatility in this market. Finally, we show that the jump componentof future realized exchange rate volatility is to some extent predictable, and thatoption implied volatility is the dominant forecast of the future jump component.......We study measures of foreign exchange rate volatility based on high-frequency (5-minute) $/DM exchange rate returns using recent nonparametric statistical techniquesto compute realized return volatility and its separate continuous sample path and jumpcomponents, and measures based on prices...

  15. Volatility of an Indian stock market A random matrix approach

    CERN Document Server

    Kulkarni, V

    2005-01-01

    We examine volatility of an Indian stock market in terms of aspects like participation, synchronization of stocks and quantification of volatility using the random matrix approach. Volatility pattern of the market is found using the BSE index for the three-year period 2000-2002. Random matrix analysis is carried out using daily returns of 70 stocks for several time windows of 85 days in 2001 to (i) do a brief comparative analysis with statistics of eigenvalues and eigenvectors of the matrix C of correlations between price fluctuations, in time regimes of different volatilities. While a bulk of eigenvalues falls within RMT bounds in all the time periods, we see that the largest (deviating) eigenvalue correlates well with the volatility of the index, the corresponding eigenvector clearly shows a shift in the distribution of its components from volatile to less volatile periods and verifies the qualitative association between participation and volatility (ii) observe that the Inverse participation ratio for the ...

  16. Influence of modified atmosphere packaging on volatile compounds and physicochemical and antioxidant attributes of fresh-cut pineapple (Ananas comosus).

    Science.gov (United States)

    Montero-Calderón, Marta; Rojas-Graü, María Alejandra; Aguiló-Aguayo, Ingrid; Soliva-Fortuny, Robert; Martín-Belloso, Olga

    2010-04-28

    The effects of modified atmosphere packaging on volatile compound content and physicochemical and antioxidant attributes of Gold cultivar fresh-cut pineapples were assessed throughout storage at 5 degrees C. Fresh-cut pineapple pieces were packed under LO (low oxygen, 12% O(2), 1% CO(2)), AIR (20.9% O(2)) and HO (high oxygen, 38% O(2)) headspace atmospheres. Methyl butanoate, methyl 2-methylbutanoate, and methyl hexanoate were the most abundant volatiles regardless of the packaging atmosphere and days of storage; whereas most odor active volatiles were methyl and ethyl 2-methylbutanoate, 2,5-dimethyl-4-methoxy-3(2H)-furanone and ethyl hexanoate. Physicochemical attributes of pineapple did not significantly vary, whereas vitamin C content and total antioxidant capacity were lower for fresh-cut pineapple in HO (488 +/- 38 mg/100 mg(fw) and 54.4 +/- 5.7%, respectively) than for LO and AIR packages. Storage life of fresh-cut pineapple was limited to 14 days by volatile compounds losses and fermentation processes.

  17. Volatile components from Anthriscus sylvestris (L.) Hoffm

    NARCIS (Netherlands)

    Bos, R.; Koulman, A; Woerdenbag, H.J.; Quax, Wim; Pras, N.

    2002-01-01

    The volatile components of fresh leaves and roots from Anthriscus sylvestris (L.) Hoffm., obtained through hydrodistillation, were analysed by GC and GC-MS. This was compared to dichloromethane extracts of both fresh and dried leaf and root material. The monoterpene fraction (69-70%) dominated, whil

  18. Volatile organic compound emissions from silage systems

    Science.gov (United States)

    As a precursor to smog, emission of volatile organic compounds (VOCs) to the atmosphere is an environmental concern in some regions. The major source from farms is silage, with emissions coming from the silo face, mixing wagon, and feed bunk. The major compounds emitted are alcohols with other impor...

  19. Volatile-mediated interactions in the rhizosphere

    NARCIS (Netherlands)

    Cordovez da Cunha, Viviane

    2016-01-01

    Plants and microorganisms are constantly engaged in highly dynamic interactions both above- and belowground. Several of these interactions are mediated by volatile organic compounds (VOCs), small carbon-based compounds with high vapor pressure at ambient temperature. In the rhizosphere, VOCs have an

  20. Linux Incident Response Volatile Data Analysis Framework

    Science.gov (United States)

    McFadden, Matthew

    2013-01-01

    Cyber incident response is an emphasized subject area in cybersecurity in information technology with increased need for the protection of data. Due to ongoing threats, cybersecurity imposes many challenges and requires new investigative response techniques. In this study a Linux Incident Response Framework is designed for collecting volatile data…

  1. The economic value of realized volatility

    DEFF Research Database (Denmark)

    Christoffersen, Peter; Feunou, Bruno; Jacobs, Kris

    2014-01-01

    develop a new class of affine discrete-time option valuation models that use daily returns as well as realized volatility. We derive convenient closed-form option valuation formulas, and we assess the option valuation properties using Standard & Poor’s (S&P) 500 return and option data. We find...

  2. Permeation of volatile compounds through starch films

    NARCIS (Netherlands)

    Yilmaz, G.; Jongboom, R.O.J.; Feil, H.; Dijk, van C.; Hennink, W.E.

    2004-01-01

    The aim of this study was to gain insight into the factors that affect the permeation of volatiles through starch films. These films were obtained by casting gelatinized starch/water/glycerol mixtures. The films were dried and conditioned under different conditions (temperature and relative humidity

  3. Ammonia volatilization from coated urea forms

    Directory of Open Access Journals (Sweden)

    Carlos Antonio Costa do Nascimento

    2013-08-01

    Full Text Available Nitrogen fertilization is a major component of the cost of agricultural production, due to the high cost and low efficiency of fertilizers. In the case of urea, the low efficiency is mainly due to losses by volatilization, which are more pronounced in cultivation systems in which plant residues are left on the soil. The objective of this work was to compare the influence of urea coated with sulfur or boric acid and copper sulfate with conventional N fertilizers on N volatilization losses in sugar cane harvested after stubble burning. The sources urea, sulfur-coated urea, urea coated with boric acid and copper sulfate, as well as nitrate and ammonium sulfate, were tested at amounts containing N rates of 120 kg ha-1 N. The integration of new technologies in urea fertilization can reduce N losses by volatilization. These losses were most reduced when using nitrate and ammonium sulfate. The application of a readily acidified substance (boric acid to urea was more efficient in reducing volatilization losses and nutrient removal by sugar cane than that of a substance with gradual acidification (elemental sulfur.

  4. Do Macroeconomic Announcements Cause Asymetric Volatility?

    NARCIS (Netherlands)

    P. de Goeij (Peter); W.A. Marquering (Wessel)

    2002-01-01

    textabstractIn this paper we study the impact of macroeconomic news announcements on the conditional volatility of stock and bond returns. Using daily returns on the S&P 500 index, the NASDAQ index, and the 1 and 10 year U.S. Treasury bonds, for January 1982 - August 2001, some interesting results e

  5. Volatility and conditional distribution in financial markets

    OpenAIRE

    Abberger, Klaus

    1995-01-01

    There are various parametric models to analyse the volatility in time series of financial market data. For maximum likelihood estimation these parametric methods require the assumption of a known conditional distribution. In this paper we examine the conditional distribution of daily DAX returns with the help of nonparametric methods. We use kernel estimators for conditional quantiles resulting from a kernel estimation of conditional distributions.

  6. There's more to volatility than volume

    CERN Document Server

    Gillemot, L; Lillo, F; Gillemot, Laszlo; Lillo, Fabrizio

    2005-01-01

    It is widely believed that fluctuations in transaction volume, as reflected in the number of transactions and to a lesser extent their size, are the main cause of clustered volatility. Under this view bursts of rapid or slow price diffusion reflect bursts of frequent or less frequent trading, which cause both clustered volatility and heavy tails in price returns. We investigate this hypothesis using tick by tick data from the New York and London Stock Exchanges and show that only a small fraction of volatility fluctuations are explained in this manner. Clustered volatility is still very strong even if price changes are recorded on intervals in which the total transaction volume or number of transactions is held constant. In addition the distribution of price returns conditioned on volume or transaction frequency being held constant is similar to that in real time, making it clear that neither of these are the principal cause of heavy tails in price returns. We analyze recent results of Ane and Geman (2000) an...

  7. Measuring volatility with the realized range

    NARCIS (Netherlands)

    M.P.E. Martens (Martin); D.J.C. van Dijk (Dick)

    2006-01-01

    textabstractRealized variance, being the summation of squared intra-day returns, has quickly gained popularity as a measure of daily volatility. Following Parkinson (1980) we replace each squared intra-day return by the high-low range for that period to create a novel and more efficient estimator

  8. Bayesian Vector Autoregressions with Stochastic Volatility

    NARCIS (Netherlands)

    Uhlig, H.F.H.V.S.

    1996-01-01

    This paper proposes a Bayesian approach to a vector autoregression with stochastic volatility, where the multiplicative evolution of the precision matrix is driven by a multivariate beta variate.Exact updating formulas are given to the nonlinear filtering of the precision matrix.Estimation of the au

  9. Volatile components from Anthriscus sylvestris (L.) Hoffm

    NARCIS (Netherlands)

    Bos, R.; Koulman, A; Woerdenbag, H.J.; Quax, Wim; Pras, N.

    2002-01-01

    The volatile components of fresh leaves and roots from Anthriscus sylvestris (L.) Hoffm., obtained through hydrodistillation, were analysed by GC and GC-MS. This was compared to dichloromethane extracts of both fresh and dried leaf and root material. The monoterpene fraction (69-70%) dominated, whil

  10. Recovery of volatile bioproducts by pervaporation

    Energy Technology Data Exchange (ETDEWEB)

    Boeddeker, K.W.

    1994-01-01

    Organophilic prevaporation is linkened to steam distillation in the recovery of volatile bioproducts of fermentation or plant origin. Potential applications are to biosynthetic chemicals (e.g., EtOH; BuOH), aroma compounds (e.g., gamma-decalactone; 6-pentyl-2-pyrone), and essential oils. Unlike steam distillation, pervaporation may be combined with an active fermenter. (orig.)

  11. Volatility Spillover Effects in European Equity Markets

    NARCIS (Netherlands)

    Baele, L.

    2003-01-01

    This paper quantifies the magnitude and time-varying nature of volatility spillovers from the aggregate European (EU) and US market to 13 local European equity markets.I develop a shock spillover model that decomposes local unexpected returns into a country speciffic shock, a regional European shock

  12. Volume, Volatility and Public News Announcements

    DEFF Research Database (Denmark)

    Bollerslev, Tim; Li, Jia; Xue, Yuan

    We provide new empirical evidence for the way in which financial markets process information. Our results are based on high-frequency intraday data along with new econometric techniques for making inference on the relationship between trading intensity and spot volatility around public news...

  13. Explaining output volatility: The case of taxation

    DEFF Research Database (Denmark)

    Posch, Olaf

    the second moment of output growth rates without (long-run) effects on the first moment. Taking the model to the data, we exploit observed heterogeneity patterns to estimate effects of tax rates on macro volatility using panel estimation, explicitly modeling the unobserved variance process. We find a strong...

  14. Acid volatile sulfide (AVS)- a comment

    NARCIS (Netherlands)

    Meysman, F.J.R.; Middelburg, J.J.

    2005-01-01

    The review by Rickard and Morse (this volume) adequately summarizes our current understanding with respect to acid-volatile sulfides (AVS). At the same time, this review addresses some of the misunderstandings with regard to measurements and dynamics of this important sedimentary sulfur pool. In

  15. Bayesian Vector Autoregressions with Stochastic Volatility

    NARCIS (Netherlands)

    Uhlig, H.F.H.V.S.

    1996-01-01

    This paper proposes a Bayesian approach to a vector autoregression with stochastic volatility, where the multiplicative evolution of the precision matrix is driven by a multivariate beta variate.Exact updating formulas are given to the nonlinear filtering of the precision matrix.Estimation of the

  16. Volatile terpenoids from aeciospores of Cronartium fusiforme.

    Science.gov (United States)

    Laseter, J. L.; Weete, J. D.; Walkinshaw, C. H.

    1973-01-01

    Identification of the terpenoids present in the volatile fraction from aeciospores of the gall rust fungus Cronartium fusiforme. The major monoterpenoid hydrocarbons found to be present with only traces of camphene include alpha-pinene, beta-pinene, delta(3)-carene, myrcene, linonene, beta-phellandrene, and delta-terpinene. A number of monoterpenoid alcohols, acyclic sesquiterpenes, and aromatic compounds were also present.

  17. Linux Incident Response Volatile Data Analysis Framework

    Science.gov (United States)

    McFadden, Matthew

    2013-01-01

    Cyber incident response is an emphasized subject area in cybersecurity in information technology with increased need for the protection of data. Due to ongoing threats, cybersecurity imposes many challenges and requires new investigative response techniques. In this study a Linux Incident Response Framework is designed for collecting volatile data…

  18. On multi-scaling in volatility processes

    NARCIS (Netherlands)

    Capobianco, E.

    2002-01-01

    Among the statistical features of financial volatility processes, the most challenging for statistical inference purposes are non-gaussianity and non-stationarity. In this study I present results from experiments aimed to empirically modeling return generating processes in which the underlying volat

  19. Influence of O2 – plasma ambience and growth temperature on the oxidation of Mo-metal and volatilization of oxides

    Directory of Open Access Journals (Sweden)

    Rabindar K. Sharma

    2013-09-01

    Full Text Available In this communication, we investigated role of the oxygen plasma on the oxidation of Mo strip surface (source of Mo and volatilization of formed oxide species. Molybdenum oxide thin films are deposited on Si substrate simultaneously by using the volatilized oxide species as vapor source. A special setup is designed to create stable discharge oxygen plasma. Both the Mo strip surface and oxide films deposited on Si substrates at different temperatures are characterized independently. The presence of well indexed and intense peaks corresponding to MoO3 and Mo8O23 oxide phases in x-ray diffraction (XRD patterns of metals strips, heated at different temperatures in oxygen plasma ambience has been considered as proof of oxidation of Mo-strip surface. The reduction in peaks intensity with increase in metal strip temperature indicates high rate of oxidation and oxide volatilization. It is observed that film formation on silicon substrate could not take place without oxygen plasma even at 500ºC. The scanning electron microscopy (SEM studies of Mo strips as well as the films deposited on Si substrates, at different temperatures are showing the modifications in surface morphology and agreed with the XRD results. Both Raman and FTIR observations of Mo strip are also in consonance with the XRD and SEM findings. The occurrence of oxidation of Mo metal and volatilization of oxide species at this low temperature 300ºC is reported for the first time.

  20. [Study of the effect of volatile metabolites of Trichoderma hamatum on the growth of phytopathogenic soilborne fungi.].

    Science.gov (United States)

    Dal Bello, G M; Mónaco, C I; Cháves, A R

    1997-09-01

    Volatile compounds produced by Trichoderma hamatum were tested for their capacity to suppress in vitro the growth of Alternaria citri, Bipolaris cynodontis, Bipolaris sorokiniana, Curvularia brachyspora, Curvularia lunata, Curvularia oryzae-sativae, Drechslera tritici-repentis, Rhizoctonia solani, Sclerotinia minor and Sclerotium rolfsii. The organisms were cultured in an apparatus made with two Erlenmeyer flasks assembled by their top parts. With the aid of the gas chromatographic technique the variation of carbon dioxide, oxygen and ethylene in the internal system was determined. Acetaldehyde and ethanol were not found. Due to the respiratory metabolism of T. hamatum the carbon dioxide level progressively increased while the oxygen content decreased. Ethylene production was low and after three days remained constant. Excepting C. oryzae-sativae and B. cynodontis the other species showed changes in the growth and development. These results suggest the inhibitory volatiles of T. hamatum as one possible mechanism of biological control.

  1. Temperature-induced volatility of molecular markers in ambient airborne particulate matter

    Directory of Open Access Journals (Sweden)

    C. R. Ruehl

    2011-01-01

    Full Text Available Molecular markers are organic compounds used to represent known sources of particulate matter (PM in statistical source apportionment studies. The utility of molecular markers depends on, among other things, their ability to represent PM volatility under realistic atmospheric conditions. We measured the particle-phase concentrations and temperature-induced volatility of commonly-used molecular markers in California's heavily polluted San Joaqin Valley. Concentrations of elemental carbon, organic carbon, levoglucosan, and polycyclic aromatic hydrocarbons were not reduced by mild (~10 K heating. In contrast, both hopane/sterane and n-alkane concentrations were reduced, especially during the summer sampling events at the urban site. These results suggest that hopanes and steranes have effective saturation concentrations ~1 μg m−3, and therefore can be considered semi-volatile. The volatility of an individual compound depends both on its inherent properties (primarily vapour pressure and the interactions between itself and any potential absorbing phase. The volatility behavior of n-alkanes during the urban summer is consistent with that predicted for absorption by suberic acid (a C8 diacid using a group contribution modelling method. Observations can also be matched by an absorbent whose composition is based on recently-obtained high-resolution aerosol mass spectrometer factors (approximately 33% "hydrocarbon-like" and 67% oxygenated organic aerosol. The reduced evaporation of the n-alkanes, hopanes, and steranes with mild heating during rural and/or winter experiments could be explained by a more oxygenated absorbing phase along with a non-absorptive partitioning mechanism, such as adsorption to soot. This suggests that the temperature-induced volatility of large hydrocarbons in PM is most important if a relatively non-polar absorbing organic phase exists. While the activity coefficients of most organic

  2. Extracorporeal membrane oxygenation circuitry.

    Science.gov (United States)

    Lequier, Laurance; Horton, Stephen B; McMullan, D Michael; Bartlett, Robert H

    2013-06-01

    The extracorporeal membrane oxygenation circuit is made of a number of components that have been customized to provide adequate tissue oxygen delivery in patients with severe cardiac and/or respiratory failure for a prolonged period of time (days to weeks). A standard extracorporeal membrane oxygenation circuit consists of a mechanical blood pump, gas-exchange device, and a heat exchanger all connected together with circuit tubing. Extracorporeal membrane oxygenation circuits can vary from simple to complex and may include a variety of blood flow and pressure monitors, continuous oxyhemoglobin saturation monitors, circuit access sites, and a bridge connecting the venous access and arterial infusion limbs of the circuit. Significant technical advancements have been made in the equipment available for short- and long-term extracorporeal membrane oxygenation applications. Contemporary extracorporeal membrane oxygenation circuits have greater biocompatibility and allow for more prolonged cardiopulmonary support time while minimizing the procedure-related complications of bleeding, thrombosis, and other physiologic derangements, which were so common with the early application of extracorporeal membrane oxygenation. Modern era extracorporeal membrane oxygenation circuitry and components are simpler, safer, more compact, and can be used across a wide variety of patient sizes from neonates to adults.

  3. Highest Oxygen Bar

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The world’s highest altitude Lhalu Wetland in Tibet is rebounding from past environmental damage In Lhasa, where the oxygen content is just 60 percent of that of the plain area, a place known as the "natural oxygen bar"is highly prized by residents.

  4. Plants and Oxygen

    NARCIS (Netherlands)

    Bailey-Serres, J.N.

    2009-01-01

    In this oratie I will first consider the fundamental nature of oxygen and its role within the plant cell and then will summarize studies on the cellular low-oxygen response that are interwoven with international efforts to provide farmers with rice that endures prolonged periods of complete

  5. Oxygen therapy - infants

    Science.gov (United States)

    ... may not work well and may die. Your baby may not grow properly. Many of the developing organs, including the brain and heart, may be injured. Too much oxygen can also cause injury. Breathing too much oxygen can damage the lung. ...

  6. Does implied volatility of currency futures option imply volatility of exchange rates?

    Science.gov (United States)

    Wang, Alan T.

    2007-02-01

    By investigating currency futures options, this paper provides an alternative economic implication for the result reported by Stein [Overreactions in the options market, Journal of Finance 44 (1989) 1011-1023] that long-maturity options tend to overreact to changes in the implied volatility of short-maturity options. When a GARCH process is assumed for exchange rates, a continuous-time relationship is developed. We provide evidence that implied volatilities may not be the simple average of future expected volatilities. By comparing the term-structure relationship of implied volatilities with the process of the underlying exchange rates, we find that long-maturity options are more consistent with the exchange rates process. In sum, short-maturity options overreact to the dynamics of underlying assets rather than long-maturity options overreacting to short-maturity options.

  7. THREE-POINT VOLATILITY SMILE CLASSIFICATION: EVIDENCE FROM THE WARSOW STOCK EXCHANGE DURING VOLATILE SUMMER 2011

    Directory of Open Access Journals (Sweden)

    García-Machado, Juan J.

    2015-01-01

    Full Text Available This paper studies the behavior of the smile in the Warsaw Stock Exchange (WSE during the volatile summer of 2011.We investigate the volatility smile derived from liquid call and put options on the Polish WIG20 index which option series expired on September 2011. In this period, the polish index has dropped about 20% in two weeks time. By linear interpolation, implied volatilities for moneyness points needed were calculated, then we construct 355 smile curves for calls and puts options to study and make some kind of smile-types classification. We propose seventeen types-smiles which represent all possible cases of three points (three moneynesses graphical patterns. This classification is made basing upon relationship higher/equal/lower values of implied volatility for each of three points. Furthermore, we distinguish the convexity of pattern. We can note that smiles, smirks and ups are convex in shape, while reversed ones and downs are concave functions.

  8. Implied volatility transmissions between Thai and selected advanced stock markets

    OpenAIRE

    Thakolsri, Supachok; Sethapramote, Yuthana; Jiranyakul, Komain

    2015-01-01

    This paper investigates the impacts of changes in the U. S. implied volatility on the changes in implied volatilities of the Euro and Thai stock markets. For that purpose, volatilities implicit in stock index option prices from the U. S., Euro and Thai stock markets are analyzed using the standard Granger causality test, impulse response analysis, and variance decompositions. The results found in this study suggest that the U. S. stock market is the leading source of volatility transmissions ...

  9. Forecasting Exchange Rate Volatility in the Presence of Jumps

    OpenAIRE

    Busch, Thomas; Christensen, Bent Jesper; Nielsen, Morten Ørregaard

    2005-01-01

    We study measures of foreign exchange rate volatility based on high-frequency (5-minute) $/DM exchange rate returns using recent nonparametric statistical techniques to compute realized return volatility and its separate continuous sample path and jump components, and measures based on prices of exchange rate futures options, allowing calculation of option implied volatility. We find that implied volatility is an informationally efficient but biased forecast of future realized exchange rate v...

  10. Iodine volatilization from irradiated CsI solutions

    Energy Technology Data Exchange (ETDEWEB)

    Evans, G.J.; Panyan, E.J. [Toronto Univ., ON (Canada). Dept. of Chemical Engineering and Applied Chemistry

    1996-12-01

    A bench-scale, separate-effect, flow apparatus has been constructed to examine volatile iodine production rates in relation to a selection of the possible variables and conditions found in a containment structure with a breached reactor core. The constructed apparatus is designed to provide the widest possible range of data including gas and aqueous phase speciation for an established set of interfacial mass transfer parameters with known pH and dissolved oxygen levels. As the interfacial transfer of iodine is an important component in the understanding of iodine chemistry, commissioning of the constructed apparatus focused on establishing a well characterized set of mass transfer parameters for a variety of mixing conditions and solution volumes. Aqueous phase parameters, obtained using a method involving the sparging of the dissolved oxygen in the aqueous phase, were found to vary by one order of magnitude, from 1x10{sup -2} to 1x10{sup -3} dm/sec. Gas phase parameters also changeable by one order of magnitude, from 1x10{sup -1} to 1x10{sup -2} dm/sec, were studied more thoroughly as they were found to have a greater impact in the system. Two independent methods of analysis were used, one involving tri-iodide solutions, the other using relative humidity values. A selection of the acquired volatility rates in relation to the effect of pH are presented. The apparatus has been found to consistently provide rates up to one order of magnitude lower than modelled predictions. Specifically, for buffered solutions, rates of 2x10{sup -12} mol/min and 1x10{sup -10} mol/min for pH 9 and 5 respectively, have been found. Rates of 1x10{sup -11} mol/min and 6x10{sup -10} mol/min are predicted. Current efforts have addressed potential reasons for this apparent discrepancy, the major factor being the possible release of components from the stainless steel during irradiation. Efforts undertaken to ensure the validity of the results are emphasized. (Abstract Truncated)

  11. Volatile hydrocarbons inhibit methanogenic crude oil degradation

    Directory of Open Access Journals (Sweden)

    Angela eSherry

    2014-04-01

    Full Text Available Methanogenic degradation of crude oil in subsurface sediments occurs slowly, but without the need for exogenous electron acceptors, is sustained for long periods and has enormous economic and environmental consequences. Here we show that volatile hydrocarbons are inhibitory to methanogenic oil biodegradation by comparing degradation of an artificially weathered crude oil with volatile hydrocarbons removed, with the same oil that was not weathered. Volatile hydrocarbons (nC5-nC10, methylcyclohexane, benzene, toluene and xylenes were quantified in the headspace of microcosms. Aliphatic (n-alkanes nC12-nC34 and aromatic hydrocarbons (4-methylbiphenyl, 3-methylbiphenyl, 2-methylnaphthalene, 1-methylnaphthalene were quantified in the total hydrocarbon fraction extracted from the microcosms. 16S rRNA genes from key microorganisms known to play an important role in methanogenic alkane degradation (Smithella and Methanomicrobiales were quantified by quantitative PCR. Methane production from degradation of weathered oil in microcosms was rapid (1.1 ± 0.1 µmol CH4/g sediment/day with stoichiometric yields consistent with degradation of heavier n-alkanes (nC12-nC34. For non-weathered oil, degradation rates in microcosms were significantly lower (0.4 ± 0.3 µmol CH4/g sediment/day. This indicated that volatile hydrocarbons present in the non-weathered oil inhibit, but do not completely halt, methanogenic alkane biodegradation. These findings are significant with respect to rates of biodegradation of crude oils with abundant volatile hydrocarbons in anoxic, sulphate-depleted subsurface environments, such as contaminated marine sediments which have been entrained below the sulfate-reduction zone, as well as crude oil biodegradation in petroleum reservoirs and contaminated aquifers.

  12. Involvement of a Broccoli COQ5 Methyltransferase in the Production of Volatile Selenium Compounds[C][OA

    Science.gov (United States)

    Zhou, Xin; Yuan, Youxi; Yang, Yong; Rutzke, Michael; Thannhauser, Theodore W.; Kochian, Leon V.; Li, Li

    2009-01-01

    Selenium (Se) is an essential micronutrient for animals and humans but becomes toxic at high dosage. Biologically based Se volatilization, which converts Se into volatile compounds, provides an important means for cleanup of Se-polluted environments. To identify novel genes whose products are involved in Se volatilization from plants, a broccoli (Brassica oleracea var italica) cDNA encoding COQ5 methyltransferase (BoCOQ5-2) in the ubiquinone biosynthetic pathway was isolated. Its function was authenticated by complementing a yeast coq5 mutant and by detecting increased cellular ubiquinone levels in the BoCOQ5-2-transformed bacteria. BoCOQ5-2 was found to promote Se volatilization in both bacteria and transgenic Arabidopsis (Arabidopsis thaliana) plants. Bacteria expressing BoCOQ5-2 produced an over 160-fold increase in volatile Se compounds when they were exposed to selenate. Consequently, the BoCOQ5-2-transformed bacteria had dramatically enhanced tolerance to selenate and a reduced level of Se accumulation. Transgenic Arabidopsis expressing BoCOQ5-2 volatilized three times more Se than the vector-only control plants when treated with selenite and exhibited an increased tolerance to Se. In addition, the BoCOQ5-2 transgenic plants suppressed the generation of reactive oxygen species induced by selenite. BoCOQ5-2 represents, to our knowledge, the first plant enzyme that is not known to be directly involved in sulfur/Se metabolism yet was found to mediate Se volatilization. This discovery opens up new prospects regarding our understanding of the complete metabolism of Se and may lead to ways to modify Se-accumulator plants with increased efficiency for phytoremediation of Se-contaminated environments. PMID:19656903

  13. The Volatility Effect: Lower Risk without Lower Return

    NARCIS (Netherlands)

    D.C. Blitz (David); P. van Vliet (Pim)

    2007-01-01

    textabstractWe present empirical evidence that stocks with low volatility earn high risk-adjusted returns. The annual alpha spread of global low versus high volatility decile portfolios amounts to 12% over the 1986-2006 period. We also observe this volatility effect within the US, European and Japan

  14. 21 CFR 573.914 - Salts of volatile fatty acids.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Salts of volatile fatty acids. 573.914 Section 573... Food Additive Listing § 573.914 Salts of volatile fatty acids. (a) Identity. The food additive is a... contains ammonium or calcium salts of volatile fatty acids and shall conform to the...

  15. Emerald ash borer responses to induced plant volatiles

    Science.gov (United States)

    Cesar Rodriguez-Saona; Therese M. Poland; James Miller; Lukasz Stelinski; Linda Buchan; Gary Grant; Peter de Groot; Linda MacDonald

    2007-01-01

    Herbivore feeding and methyl jasmonate, a volatile derivative of the stress-eliciting plant hormone, jasmonic acid, induce responses in plants which include the synthesis and emission of volatiles. These induced volatiles can serve to attract or repel herbivores; therefore, they may have potential use in pest management programs. The exotic emerald ash borer (EAB),...

  16. System of extraction of volatiles from soil using microwave processes

    Science.gov (United States)

    Ethridge, Edwin C. (Inventor); Kaukler, William F. (Inventor)

    2013-01-01

    A device for the extraction and collection of volatiles from soil or planetary regolith. The device utilizes core drilled holes to gain access to underlying volatiles below the surface. Microwave energy beamed into the holes penetrates through the soil or regolith to heat it, and thereby produces vapor by sublimation. The device confines and transports volatiles to a cold trap for collection.

  17. Another Look at the Volatility of Stock Prices

    Science.gov (United States)

    Maruszewski, Richard F., Jr.

    2007-01-01

    Investors are interested in the volatility of a stock for various reasons. One investor may desire to purchase a low volatility stock for peace of mind. Another may be interested in a high volatility stock in order to have the opportunity to buy low and sell high as the price of the stock oscillates. This author had the fortunate timing of reading…

  18. Factor Structure in Commodity Futures Return and Volatility

    DEFF Research Database (Denmark)

    Christoffersen, Peter; Lunde, Asger; Olesen, Kasper Vinther

    Using data on more than 750 million futures trades during 2004-2013, we analyze eight stylized facts of commodity price and volatility dynamics in the post financialization period. We pay particular attention to the factor structure in returns and volatility and to commodity market integration...... volatility indicates a nontrivial degree of market integration....

  19. On the non-causal link between volatility and growth

    DEFF Research Database (Denmark)

    Posch, Olaf; Wälde, Klaus

    di er both in their volatility and growth. Using a continuous-time DSGE model with plausible parametric restrictions, we obtain closedform measures of macro volatility based on cyclical components and output growth rates. Given our results, empirical volatility-growth analysis should include controls...

  20. 40 CFR 53.66 - Test procedure: Volatility test.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 5 2010-07-01 2010-07-01 false Test procedure: Volatility test. 53.66... Characteristics of Class II Equivalent Methods for PM2.5 § 53.66 Test procedure: Volatility test. (a) Overview. This test is designed to ensure that the candidate method's losses due to volatility when sampling...

  1. New technology for volatile components stripping in process fluids; Nova tecnologia para estripagem de componentes volateis em fluidos de processo

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Roberto Massao [White Martins Gases Industriais, Rio de Janeiro, RJ (Brazil)

    1992-12-31

    Stripping is a process used in order to remove volatile contaminants during the purification step by bubbling inert gas in a contaminated liquid. This work defines the stripping process and its process parameters, describes some stripping techniques and introduces the supersonic stripper, that works at supersonic velocity. Dissolved oxygen reduction and stripping time reduction results are shown. The conclusion is that the supersonic stripper is superior to the in-line conventional systems. (author) 6 refs., 2 figs.

  2. Volatility transmission and volatility impulse response functions in European electricity forward markets

    Energy Technology Data Exchange (ETDEWEB)

    Le Pen, Yannick [Institut d' Economie et de Management de Nantes - IAE, Universite de Nantes, Chemin de la Censive du Tertre, BP 52231, 44322 Nantes cedex 3 (France); Sevi, Benoit [Universite d' Angers (GRANEM), Faculte de Droit, Economie et Gestion, Universite d' Angers, 13 allee Francois Mitterrand, BP 13633, 49036 Angers cedex 01 (France)

    2010-07-15

    Using daily data from March 2001 to June 2005, we estimate a VAR-BEKK model and find evidence of return and volatility spillovers between the German, the Dutch and the British forward electricity markets. We apply Hafner and Herwartz [2006, Journal of International Money and Finance 25, 719-740] Volatility Impulse Response Function (VIRF) to quantify the impact of shock on expected conditional volatility. We observe that a shock has a high positive impact only if its size is large compared to the current level of volatility. The impact of shocks are usually not persistent, which may be a consequence of the non-storability of power. Finally, we estimate the density of the VIRF at different forecast horizons. These fitted distributions are asymmetric and show that large increases in expected conditional volatilities are possible even if their probability is low. These results have interesting implications for market participants whose risk management policy depends on option prices which themselves depend on the characteristics of volatility. (author)

  3. Characterization of Semi-volatility of Atmospheric Submicron Particles at a Regional Background Site in North China

    Science.gov (United States)

    He, L. Y.

    2015-12-01

    HE Lingyan1, HUANG Congni1, HUANG Xiaofeng11. Key Laboratory for Urban Habitat Environmental Science and Technology, School of Environment and Energy, Peking University Shenzhen Graduate School, Shenzhen 518055, China Abstract:The coupling of a Thermal Denuder (TD) with a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) was used in Xianghe, which is a regional background site in North China, during June - July, 2013 to on-line measure the mass concentrations and semi-volatilities of atmospheric submicron particles, including organic matter (OM), SO42- , NO3-, NH4+, and Cl-. The total PM1 mass concentration measured was averagely (47.9±47.3) mg/m3 during the campaign, with OM accounting for 38.2% of the total PM1 mass, followed by SO42- (33.7%), NH4+ (13.8%), NO3- (12.3%), and Cl- (2.0%). It was found that NO3- and Cl- had the highest semi-volatility, with about 60% of them evaporating into the gas phase by increasing the temperature to 50 °C, while SO42- showed the lowest semi-volatility, with almost 90% of its mass remaining in the particle phase at 50 °C. The semi-volatility of OM and NH4+ was at the middle level. The semi-volatility of NO3- was affected by the pollution level of the atmospheric submicron particles since it showed an increasing trend with the increasing of PM1 at 50 °C. The oxygen-to-carbon ration of organic aerosol was 0.47 to 0.60 by increasing the temperature from 50 ℃ to 200 °C. In addition, the semi-volatility of the PM1 species with vacuum aerodynamic diameters of 60-2000 nm was little size dependent. The calculation based on the high-resolution mass spectra of OM showed that CO2+-containing organic species had lower semi-volatility, while C4H9+-containing organic species had higher semi-volatility. The semi-volatility of OM was found to be negatively related to its oxidation state. The quantitative result of atmospheric submicron particles' semi-volatility is essential to the research of the physicochemical

  4. Volatile compounds emission and health risk assessment during composting of organic fraction of municipal solid waste

    DEFF Research Database (Denmark)

    Mustafa, Muhammad Farooq; Liu, Yanjun; Duan, Zhenhan

    2017-01-01

    Degradation of mechanically sorted organic fraction (MSOF) of municipal solid waste in composting facilities is among the major contributors of volatile compounds (VCs) generation and emission, causes nuisance problems and health risks on site as well as in the vicinages. The aim of current study...... was to determine the seasonal (summer and winter) variation and human health risk assessment of VCs in the ambient air of different processing units in MSOF at composting plant in China. Average concentration of VCs was 58.50 and 138.03 mg/m3 in summer and winter respectively. Oxygenated compounds were found...

  5. Volatile Oil Constituents of Rosa canina L.: Quality As Affected by the Distillation Method

    OpenAIRE

    Karim Hosni; Amel Kerkenni; Wafa Medfei; Nadia Ben Brahim; Houcine Sebei

    2010-01-01

    The volatile oils of R. canina flowers were isolated by hydrodistillation (HD) and traditional dry distillation (DD) and analyzed by HRGC-FID and GC-MS. Compared to HD, DD at 50°C leads to the isolation of high quality oil which contains the highest content of oxygenated compounds (83%). The main components are the 2-phenethyl alcohol and eugenol. The percentage of the 2-phenethyl alcohol, a highly desirable component in rose oil, was significantly higher (58.4%) in DD extract when compared t...

  6. Oxygen foreshock of Mars

    Science.gov (United States)

    Yamauchi, M.; Lundin, R.; Frahm, R. A.; Sauvaud, J.-A.; Holmström, M.; Barabash, S.

    2015-12-01

    Mars Express (MEX) has operated for more than 10 years in the environment of Mars, providing solar wind ion observations from the Analyzer of Space Plasmas and Energetic Atoms experiment's Ion Mass Analyser (IMA). On 21 September 2008, MEX/IMA detected foreshock-like discrete distributions of oxygen ions at around 1 keV in the solar wind attached to the bow shock and this distribution was observed continuously up to more than 2000 km from the bow shock. Foreshock-like protons are also observed but at a shifted location from the oxygen by about 1000 km, at a slightly higher energy, and flowing in a slightly different direction than the oxygen ions. Both protons and oxygen ions are flowing anti-sunward at different angles with respect to the solar wind direction. This is the first time that a substantial amount of planetary oxygen is observed upstream of the bow shock. Although rare, this is not the only IMA observation of foreshock-like oxygen: oxygen ions are sometimes observed for a short period of time (<5 min) inside the foreshock region. These observations suggest a new escape channel for planetary ions through the acceleration in the bow shock-magnetosheath region.

  7. Long Memory in Stock Market Volatility and the Volatility-in-Mean Effect: The FIEGARCH-M Model

    DEFF Research Database (Denmark)

    Christensen, Bent Jesper; Nielsen, Morten Ørregaard; Zhu, Jie

    We extend the fractionally integrated exponential GARCH (FIEGARCH) model for daily stock return data with long memory in return volatility of Bollerslev and Mikkelsen (1996) by introducing a possible volatility-in-mean effect. To avoid that the long memory property of volatility carries over to r...

  8. Long Memory in Stock Market Volatility and the Volatility-in-Mean Effect: The FIEGARCH-M Model

    DEFF Research Database (Denmark)

    Christensen, Bent Jesper; Nielsen, Morten Ørregaard; Zhu, Jie

    We extend the fractionally integrated exponential GARCH (FIEGARCH) model for daily stock return data with long memory in return volatility of Bollerslev and Mikkelsen (1996) by introducing a possible volatility-in-mean effect. To avoid that the long memory property of volatility carries over to r...

  9. Proteomic and metabolomic analyses provide insight into production of volatile and non-volatile flavor components in mandarin hybrid fruit

    Science.gov (United States)

    Although many of the volatile constituents of flavor and aroma in citrus have been identified, the molecular mechanism and regulation of volatile production is not well understood. Our aim was to understand mechanisms of flavor volatile production and regulation in mandarin fruit. To this end fruits...

  10. Visualization of electrolyte volatile phenomenon in DIR-MCFC

    Science.gov (United States)

    Sugiura, Kimihiko; Yodo, Tadakatsu; Yamauchi, Makoto; Tanimoto, Kazumi

    Volatilization of molten salt is one of the factors that control the performance of molten carbonate fuel cells (MCFC). Volatilization of molten salt promotes cross-leakage and the corrosion of metallic components. Moreover, piping blockage is caused by the solidification of volatile matter. Because reforming catalysts filling the anode channel are polluted by molten salt volatile matter in direct internal reforming molten carbonate fuel cells (DIR-MCFC), the volatilization of molten salt is an especially serious subject. However, neither the behaviour nor the volatilization volume of molten salt volatile matter has heretofore been elucidated on. Because molten salt volatile matter that has strong alkalinity cannot be supplied directly to an analyzer, its volatilization volume is small, and analytical accuracy is poor. Therefore, an attempt has been made to elucidate about the electrolyte volatile phenomenon in an MCFC by using a non-contact image measurement technique. A 16 cm 2 MCFC single cell frame has an observation window and an irradiation window. The image of the volatile phenomenon is shown by irradiating a YAG laser light sheet 2 mm thick from an irradiation window into the anode channel, and taking measurements from an observation window with a high spatial resolution video camera (12 bit). As a result, though the volatile matter is not observed in an anode channel at OCV, the volatile matter flows in a belt-like manner from the inlet side near the electrode toward the outlet at a current density of 150 mA cm -2. In addition, volatile matter is difficult to observe with the conventional thickness of an anode electrode. Because the composition of these volatile matters is 15Li 2CO 3/85K 2CO 3 (the result of conversion into molten salt) by ion chromatography analysis, it is not an electrolyte (62Li 2CO 3/38K 2CO 3) but rather the volatile matter of potassium, such as KOH. Therefore, it is understood that the volatile matter K 2CO 3 is generated as KOH

  11. The fate of volatiles in mid-ocean ridge magmatism

    CERN Document Server

    Keller, Tobias; Hirschmann, Marc M

    2016-01-01

    Deep-Earth volatile cycles couple the mantle with near-surface reservoirs. Volatiles are emitted by volcanism and, in particular, from mid-ocean ridges, which are the most prolific source of basaltic volcanism. Estimates of volatile extraction from the asthenosphere beneath ridges typically rely on measurements of undegassed lavas combined with simple petrogenetic models of the mean degree of melting. Estimated volatile fluxes have large uncertainties; this is partly due to a poor understanding of how volatiles are transported by magma in the asthenosphere. Here, we assess the fate of mantle volatiles through numerical simulations of melting and melt transport at mid-ocean ridges. Our simulations are based on two-phase, magma/mantle dynamics theory coupled to an idealised thermodynamic model of mantle melting in the presence of water and carbon dioxide. We combine simulation results with catalogued observations of all ridge segments to estimate a range of likely volatile output from the global mid-ocean ridge...

  12. Modeling and Forecasting the Volatility of Eastern European Emerging Markets

    Directory of Open Access Journals (Sweden)

    Sang Hoon Kang

    2009-06-01

    Full Text Available This study has attempted to seek a volatility forecasting model that can reflect sufficiently the long memory characteristic in the volatility of four Eastern European emerging stock markets, naThis study has attempted to seek a volatility forecasting model that can reflect sufficiently the long memory characteristic in the volatility of four Eastern European emerging stock markets, namely, Hungary, Poland, Russia, and Slovakia. From the results of our empirical analysis, we found that the FIGARCH model is better equipped to capture the long memory property in the volatility of these markets than the GARCH and IGARCH models. More importantly, the FIGARCH model is found to provide superior performance in one-day-ahead volatility forecasts. Thus, this study recommends researchers, portfolio managers, and traders to use the long memory FIGARCH model in analyzing and forecasting the volatility dynamics of Eastern European emerging markets.

  13. Aspects of volatility targeting for South African equity investors

    Directory of Open Access Journals (Sweden)

    Bhekinkosi Khuzwayo

    2014-11-01

    Full Text Available We consider so-called volatility targeting strategies in the South African equity market. These strategies are aimed at keeping the volatility of a portfolio consisting of a risky asset, typically an equity index, and cash fixed. This is done by changing the allocation of the assets based on an indicator of the future volatility of the risky asset. We use the three month rolling implied volatility as an indicator of future volatility to influence our asset allocation. We compare investments based on different volatility targets to the performance of bonds, equities, property as well as the Absolute Return peer mean. We examine risk and return characteristics of the volatility targeting strategy as compared to different asset classes.

  14. The effect of warming and enhanced ultraviolet radiation on gender-specific emissions of volatile organic compounds from European aspen

    Energy Technology Data Exchange (ETDEWEB)

    Maja, Mengistu M., E-mail: mengistu.maja@uef.fi [University of Eastern Finland, Department of Environmental Science, P.O.Box 1627, 70211 Kuopio (Finland); Kasurinen, Anne; Holopainen, Toini [University of Eastern Finland, Department of Environmental Science, P.O.Box 1627, 70211 Kuopio (Finland); Julkunen-Tiitto, Riitta [University of Eastern Finland, Department of Biology, P.O. Box 111, 80101 Joensuu (Finland); Holopainen, Jarmo K. [University of Eastern Finland, Department of Environmental Science, P.O.Box 1627, 70211 Kuopio (Finland)

    2016-03-15

    Different environmental stress factors often occur together but their combined effects on plant secondary metabolism are seldom considered. We studied the effect of enhanced ultraviolet (UV-B) (31% increase) radiation and temperature (ambient + 2 °C) singly and in combination on gender-specific emissions of volatile organic compounds (VOCs) from 2-year-old clones of European aspen (Populus tremula L.). Plants grew in 36 experimental plots (6 replicates for Control, UV-A, UV-B, T, UV-A + T and UV-B + T treatments), in an experimental field. VOCs emitted from shoots were sampled from two (1 male and 1 female) randomly selected saplings (total of 72 saplings), per plot on two sampling occasions (June and July) in 2014. There was a significant UV-B × temperature interaction effect on emission rates of different VOCs. Isoprene emission rate was increased due to warming, but warming also modified VOC responses to both UV-A and UV-B radiation. Thus, UV-A increased isoprene emissions without warming, whereas UV-B increased emissions only in combination with warming. Warming-modified UV-A and UV-B responses were also seen in monoterpenes (MTs), sesquiterpenes (SQTs) and green leaf volatiles (GLVs). MTs showed also a UV × gender interaction effect as females had higher emission rates under UV-A and UV-B than males. UV × gender and T × gender interactions caused significant differences in VOC blend as there was more variation (more GLVs and trans-β-caryophyllene) in VOCs from female saplings compared to male saplings. VOCs from the rhizosphere were also collected from each plot in two exposure seasons, but no significant treatment effects were observed. Our results suggest that simultaneous warming and elevated-UV-radiation increase the emission of VOCs from aspen. Thus the contribution of combined environmental factors on VOC emissions may have a greater impact to the photochemical reactions in the atmosphere compared to the impact of individual factors acting alone

  15. Central oxygen pipeline failure

    African Journals Online (AJOL)

    Anaesthetic and critical care staff play a governing role in the comprehension of a ... complete central oxygen pipeline failure occurred throughout. Tygerberg Hospital. ..... emergency stations and at plant room emergency supply manifolds.

  16. High Selectivity Oxygen Delignification

    Energy Technology Data Exchange (ETDEWEB)

    Lucian A. Lucia

    2005-11-15

    Project Objective: The objectives of this project are as follows: (1) Examine the physical and chemical characteristics of a partner mill pre- and post-oxygen delignified pulp and compare them to lab generated oxygen delignified pulps; (2) Apply the chemical selectivity enhancement system to the partner pre-oxygen delignified pulps under mill conditions (with and without any predetermined amounts of carryover) to determine how efficiently viscosity is preserved, how well selectivity is enhanced, if strength is improved, measure any yield differences and/or bleachability differences; and (3) Initiate a mill scale oxygen delignification run using the selectivity enhancement agent, collect the mill data, analyze it, and propose any future plans for implementation.

  17. Optic nerve oxygen tension

    DEFF Research Database (Denmark)

    la Cour, M; Kiilgaard, Jens Folke; Eysteinsson, T

    2000-01-01

    To investigate the influence of acute changes in intraocular pressure on the oxygen tension in the vicinity of the optic nerve head under control conditions and after intravenous administration of 500 mg of the carbonic anhydrase inhibitor dorzolamide....

  18. Volatile compounds of commercial Milano salami.

    Science.gov (United States)

    Meynier, A; Novelli, E; Chizzolini, R; Zanardi, E; Gandemer, G

    1999-02-01

    The relationship between extracted volatiles of Milano salami, one of the main dry-cured sausages produced in Italy, and their olfactory properties was studied. Volatile compounds were extracted by a purge-and-trap method, quantified using a flame ionisation detector and identified by mass spectrometry. Olfactory analysis was performed by sniffing the gas chromatographic effluent. Nearly 80 compounds were identified and quantified: most came from spices (60.5%), 18.9% from lipid oxidation, 11.8% from amino acid catabolism and 4.9% from fermentation processes. Panellists detected 19 odours by sniffing. These odours were associated with spices, lipid oxidation or fermentation and were in agreement with the contributions of each reaction to the overall aroma of the product.

  19. Recent developments in volatility modeling and applications

    Directory of Open Access Journals (Sweden)

    A. Thavaneswaran

    2006-01-01

    Full Text Available In financial modeling, it has been constantly pointed out that volatility clustering and conditional nonnormality induced leptokurtosis observed in high frequency data. Financial time series data are not adequately modeled by normal distribution, and empirical evidence on the non-normality assumption is well documented in the financial literature (details are illustrated by Engle (1982 and Bollerslev (1986. An ARMA representation has been used by Thavaneswaran et al., in 2005, to derive the kurtosis of the various class of GARCH models such as power GARCH, non-Gaussian GARCH, nonstationary and random coefficient GARCH. Several empirical studies have shown that mixture distributions are more likely to capture heteroskedasticity observed in high frequency data than normal distribution. In this paper, some results on moment properties are generalized to stationary ARMA process with GARCH errors. Application to volatility forecasts and option pricing are also discussed in some detail.

  20. Water on The Moon, III. Volatiles & Activity

    CERN Document Server

    Crotts, Arlin

    2012-01-01

    For centuries some scientists have argued that there is activity on the Moon (or water, as recounted in Parts I & II), while others have thought the Moon is simply a dead, inactive world. The question comes in several forms: is there a detectable atmosphere? Does the surface of the Moon change? What causes interior seismic activity? From a more modern viewpoint, we now know that as much carbon monoxide as water was excavated during the LCROSS impact, as detailed in Part I, and a comparable amount of other volatiles were found. At one time the Moon outgassed prodigious amounts of water and hydrogen in volcanic fire fountains, but released similar amounts of volatile sulfur (or SO2), and presumably large amounts of carbon dioxide or monoxide, if theory is to be believed. So water on the Moon is associated with other gases. We review what is known (and touch on what is unknown) about outgassing of various gases from the Moon.