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Sample records for alkanes computational evidence

  1. Hydrogen Bonding to Alkanes: Computational Evidence

    DEFF Research Database (Denmark)

    Hammerum, Steen; Olesen, Solveig Gaarn

    2009-01-01

    The structural, vibrational, and energetic properties of adducts of alkanes and strong cationic proton donors were studied with composite ab initio calculations. Hydrogen bonding in [D-H+ H-alkyl] adducts contributes to a significant degree to the interactions between the two components, which...... is substantiated by NBO and AIM results. The hydrogen bonds manifest themselves in the same manner as conventional hydrogen bonds, D-H bond elongation, D-H vibrational stretching frequency red shift and intensity increase, and adduct stabilization. The alkane adducts also exhibit elongation of the C-H bonds...

  2. Fully atomistic molecular-mechanical model of liquid alkane oils: Computational validation.

    Science.gov (United States)

    Zahariev, Tsvetan K; Slavchov, Radomir I; Tadjer, Alia V; Ivanova, Anela N

    2014-04-15

    Fully atomistic molecular dynamics simulations were performed on liquid n-pentane, n-hexane, and n-heptane to derive an atomistic model for middle-chain-length alkanes. All simulations were based on existing molecular-mechanical parameters for alkanes. The computational protocol was optimized, for example, in terms of thermo- and barostat, to reproduce properly the properties of the liquids. The model was validated by comparison of thermal, structural, and dynamic properties of the normal alkane liquids to experimental data. Two different combinations of temperature and pressure coupling algorithms were tested. A simple differential approach was applied to evaluate fluctuation-related properties with sufficient accuracy. Analysis of the data reveals a satisfactory representation of the hydrophobic systems behavior. Thermodynamic parameters are close to the experimental values and exhibit correct temperature dependence. The observed intramolecular geometry corresponds to extended conformations domination, whereas the intermolecular structure demonstrates all characteristics of liquid systems. Cavity size distribution function was calculated from coordinates analysis and was applied to study the solubility of gases in hexane and heptane oils. This study provides a platform for further in-depth research on hydrophobic solutions and multicomponent systems.

  3. Abundance of macroalgal organic matter in biofilms: Evidence from n-alkane biomarkers

    Digital Repository Service at National Institute of Oceanography (India)

    Garg, A.; Bhosle, N.B.

    & Bray, 1963; Kennicutt & Jeffrey, 1981; Doskey & Talbot, 2000). The n-alkanes derived from oils exhibit a carbon preference of one or near one, whereas the n-alkanes of plants generally exhibit a strong odd or even carbon preference. Terrestrial plants... were obtained from Supelco, USA. The internal standard methyl nonadecanoate was obtained from Fluka, Switzerland and the potassium peroxydisul- phate used for ON estimation from Merck, Germany. Analytical grade methanol, dichloromethane, hexane...

  4. An analysis of organic matter sources for surface sediments in the central South Yellow Sea, China: evidence based on macroelements and n-alkanes.

    Science.gov (United States)

    Zhang, Shengyin; Li, Shuanglin; Dong, Heping; Zhao, Qingfang; Lu, Xinchuan; Shi, Ji'an

    2014-11-15

    By analyzing the composition of n-alkane and macroelements in the surface sediments of the central South Yellow Sea of China, we evaluated the influencing factors on the distribution of organic matter. The analysis indicates that the distribution of total organic carbon (TOC) was low in the west and high in the east, and TOC was more related to Al2O3 content than medium diameter (MD). The composition of n-alkanes indicated the organic matter was mainly derived from terrestrial higher plants. Contributions from herbaceous plants and woody plants were comparable. The comprehensive analysis of the parameters of macroelements and n-alkanes showed the terrestrial organic matter in the central South Yellow Sea was mainly from the input of the modern Yellow River and old Yellow River. However, some samples exhibited evident input characteristics from petroleum sources, which changed the original n-alkanes of organic matter in sediments.

  5. Insertion of singlet chlorocarbenes across C-H bonds in alkanes: Evidence for two phase mechanism

    Indian Academy of Sciences (India)

    M Ramalingam; K Ramasami; P Venuvanalingam

    2007-09-01

    Transition states for the insertion reactions of singlet mono and dichlorocarbenes (1CHCl and 1CCl2) into C-H bonds of alkanes (methane, ethane, propane and -butane) have been investigated at MP2 and DFT levels with 6-31g ( , ) basis set. The of 1CHCl and 1CCl2 may interact with alkane’s filled fragment orbital of either or symmetry. So chlorocarbenes insertion reactions have been investigated for both (/) approaches. The approach has been adjudicated to be the minimum energy path over the approach both at the MP2 and DFT levels. Mulliken, NPA and ESP derived charge analyses have been carried out along the minimal energy reaction path using the IRC method for 1CHCl and 1CCl2 insertions into the primary and secondary C-H bonds of propane. The occurrence of TSs either in the electrophilic or nucleophilic phase has been identified through NBO charge analyses in addition to the net charge flow from alkane to the carbene moiety.

  6. Adiabatic Coupling Constant of Nitrobenzene- n-Alkane Critical Mixtures. Evidence from Ultrasonic Spectra and Thermodynamic Data

    Science.gov (United States)

    Mirzaev, Sirojiddin Z.; Kaatze, Udo

    2016-09-01

    Ultrasonic spectra of mixtures of nitrobenzene with n-alkanes, from n-hexane to n-nonane, are analyzed. They feature up to two Debye-type relaxation terms with discrete relaxation times and, near the critical point, an additional relaxation term due to the fluctuations in the local concentration. The latter can be well represented by the dynamic scaling theory. Its amplitude parameter reveals the adiabatic coupling constant of the mixtures of critical composition. The dependence of this thermodynamic parameter upon the length of the n-alkanes corresponds to that of the slope in the pressure dependence of the critical temperature and is thus taken another confirmation of the dynamic scaling model. The change in the variation of the coupling constant and of several other mixture parameters with alkane length probably reflects a structural change in the nitrobenzene- n-alkane mixtures when the number of carbon atoms per alkane exceeds eight.

  7. Late Quaternary environmental changes inferred from n-alkane evidence in coastal area of southern Hainan Island, China

    Science.gov (United States)

    Wang, Mengyuan; Zheng, Zhuo

    2016-04-01

    The studied core was a coastal core in Hainan Island, China. It is in length of 49.01m and divided into four Units (MIS 1~MIS 6) according to lithology description. The Optically Stimulated Luminescence (OSL) attributes the sediments from Unit 3 to the Oxygen Isotope Stage of MIS 5e (Unit 3b and 3c) and 5d (Unit 3a). To interpret the origination of organic carbons and to reconstruct paleovegetation changes, n-alkane, δ13C and TOC have been used in the present research. The result of n-alkanes distribution indicates a series of changes of sedimentary environment and terrestrial input. The shallow water facies at Unit 2, 3a and 4 is mainly characterized by short carbon chain n-alkanes and relatively low concentration. Contrasting with that of deep-water marine facies of MIS 5e (Unit 3b), the n-alkane pattern is typical bimodal and the main peaks are both in short and long carbon chains. During Unit 3b-1 (MIS 5e), more terrestrial original n-alkanes contribute to the concentration of TOC than oceanic. Organic matter source is mainly terrestrial origination. Total organic matter input mechanism of TLG-01 correlates with sediment grain size (average grain size). Total organic carbon input is enhanced with the increasing of fine grain size component. The variation of CPI (25-33) value in this study correlates with hydrological energy. The highest CPI (25-33) value is shown in the high sea level period of MIS 5e, comparing with that in MIS 5d and MIS 1. High CPI value corresponds to high TOC and average grain size (Φ) value. In the weak hydrological energy sedimentary environment, more terrestrial organic matter, together with TOC, deposit in the study area. ACL (25-33) index display higher values in the interglacial period (MIS 5 and MIS 1) than MIS 3 (sediments weathered during MIS 2) and MIS 6. Paq proxy, together with δ13C, estimates the mangrove growing depth in MIS 5e. The correlation between δ13C and each carbon chain alkane state stabilize and turbulence of

  8. Mössbauer studies of alkane ω-hydroxylase: Evidence for a diiron cluster in an integral-membrane enzyme

    OpenAIRE

    Shanklin, John; Achim, Catalina; Schmidt, Hermann; Fox, Brian G.; Münck, Eckard

    1997-01-01

    The gene encoding the alkane ω-hydroxylase (AlkB; EC 1.14.15.3) from Pseudomonas oleovorans was expressed in Escherichia coli. The integral-membrane protein was purified as nearly homogeneous protein vesicles by differential ultracentrifugation and HPLC cation exchange chromatography without the detergent solubilization normally required for membrane proteins. Purified AlkB had specific activity of up to 5 units/mg for octane-dependent NADPH consumption. Mössbauer studies of AlkB showed that ...

  9. In situ detection of anaerobic alkane metabolites in subsurface environments.

    Science.gov (United States)

    Agrawal, Akhil; Gieg, Lisa M

    2013-01-01

    Alkanes comprise a substantial fraction of crude oil and refined fuels. As such, they are prevalent within deep subsurface fossil fuel deposits and in shallow subsurface environments such as aquifers that are contaminated with hydrocarbons. These environments are typically anaerobic, and host diverse microbial communities that can potentially use alkanes as substrates. Anaerobic alkane biodegradation has been reported to occur under nitrate-reducing, sulfate-reducing, and methanogenic conditions. Elucidating the pathways of anaerobic alkane metabolism has been of interest in order to understand how microbes can be used to remediate contaminated sites. Alkane activation primarily occurs by addition to fumarate, yielding alkylsuccinates, unique anaerobic metabolites that can be used to indicate in situ anaerobic alkane metabolism. These metabolites have been detected in hydrocarbon-contaminated shallow aquifers, offering strong evidence for intrinsic anaerobic bioremediation. Recently, studies have also revealed that alkylsuccinates are present in oil and coal seam production waters, indicating that anaerobic microbial communities can utilize alkanes in these deeper subsurface environments. In many crude oil reservoirs, the in situ anaerobic metabolism of hydrocarbons such as alkanes may be contributing to modern-day detrimental effects such as oilfield souring, or may lead to more beneficial technologies such as enhanced energy recovery from mature oilfields. In this review, we briefly describe the key metabolic pathways for anaerobic alkane (including n-alkanes, isoalkanes, and cyclic alkanes) metabolism and highlight several field reports wherein alkylsuccinates have provided evidence for anaerobic in situ alkane metabolism in shallow and deep subsurface environments.

  10. In situ detection of anaerobic alkane metabolites in subsurface environments

    Directory of Open Access Journals (Sweden)

    Lisa eGieg

    2013-06-01

    Full Text Available Alkanes comprise a substantial fraction of crude oil and refined fuels. As such, they are prevalent within deep subsurface fossil fuel deposits and in shallow subsurface environments such as aquifers that are contaminated with hydrocarbons. These environments are typically anaerobic, and host diverse microbial communities that can potentially use alkanes as substrates. Anaerobic alkane biodegradation has been reported to occur under nitrate-reducing, sulfate-reducing, and methanogenic conditions. Elucidating the pathways of anaerobic alkane metabolism has been of interest in order to understand how microbes can be used to remediate contaminated sites. Alkane activation primarily occurs by addition to fumarate, yielding alkylsuccinates, unique anaerobic metabolites that can be used to indicate in situ anaerobic alkane metabolism. These metabolites have been detected in hydrocarbon-contaminated shallow aquifers, offering strong evidence for intrinsic anaerobic bioremediation. Recently, studies have also revealed that alkylsuccinates are present in oil and coal seam production waters, indicating that anaerobic microbial communities can utilize alkanes in these deeper subsurface environments. In many crude oil reservoirs, the in situ anaerobic metabolism of hydrocarbons such as alkanes may be contibuting to modern-day detrimental effects such as oilfield souring, or may lead to more benefical technologies such as enhanced energy recovery from mature oilfields. In this review, we briefly describe the key metabolic pathways for anaerobic alkane (including n-alkanes, isoalkanes, and cyclic alkanes metabolism and highlight several field reports wherein alkylsuccinates have provided evidence for anaerobic in situ alkane metabolism in shallow and deep subsurface environments.

  11. Evidence from carbon isotope measurements for biological origins of individual longchain n-alkanes in sediments from the Nansha Sea, China

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Carbon isotopes are measured for individual long-chain n-alkanes in sediments from the Nansha Sea. The features of carbon isotopic compositions of individual n-alkanes and their origins are studied. The results show that the long-chain n-aikanes have a light carbon isotopic composition and a genetic feature of mixing sources, and low-latitude higher plants and microbes are considered to be their main end member sources. Based on the abundances and carbon isotopic compositions of individual n-alkanes, the fractional contributions of the two end member sources to individual n-aikanes are quantitatively calculated by using a mixing model. The obtained data indicate that the fractional contributions of the two biological sources are different in the three samples. A trend is that the contribution of microbes increases with the depth. These results provide the theory basis and quantitatively studied method for carbon isotopic applied research of individual n-alkanes.

  12. Computational mate choice: theory and empirical evidence.

    Science.gov (United States)

    Castellano, Sergio; Cadeddu, Giorgia; Cermelli, Paolo

    2012-06-01

    The present review is based on the thesis that mate choice results from information-processing mechanisms governed by computational rules and that, to understand how females choose their mates, we should identify which are the sources of information and how they are used to make decisions. We describe mate choice as a three-step computational process and for each step we present theories and review empirical evidence. The first step is a perceptual process. It describes the acquisition of evidence, that is, how females use multiple cues and signals to assign an attractiveness value to prospective mates (the preference function hypothesis). The second step is a decisional process. It describes the construction of the decision variable (DV), which integrates evidence (private information by direct assessment), priors (public information), and value (perceived utility) of prospective mates into a quantity that is used by a decision rule (DR) to produce a choice. We make the assumption that females are optimal Bayesian decision makers and we derive a formal model of DV that can explain the effects of preference functions, mate copying, social context, and females' state and condition on the patterns of mate choice. The third step of mating decision is a deliberative process that depends on the DRs. We identify two main categories of DRs (absolute and comparative rules), and review the normative models of mate sampling tactics associated to them. We highlight the limits of the normative approach and present a class of computational models (sequential-sampling models) that are based on the assumption that DVs accumulate noisy evidence over time until a decision threshold is reached. These models force us to rethink the dichotomy between comparative and absolute decision rules, between discrimination and recognition, and even between rational and irrational choice. Since they have a robust biological basis, we think they may represent a useful theoretical tool for

  13. Microbial biosynthesis of alkanes.

    Science.gov (United States)

    Schirmer, Andreas; Rude, Mathew A; Li, Xuezhi; Popova, Emanuela; del Cardayre, Stephen B

    2010-07-30

    Alkanes, the major constituents of gasoline, diesel, and jet fuel, are naturally produced by diverse species; however, the genetics and biochemistry behind this biology have remained elusive. Here we describe the discovery of an alkane biosynthesis pathway from cyanobacteria. The pathway consists of an acyl-acyl carrier protein reductase and an aldehyde decarbonylase, which together convert intermediates of fatty acid metabolism to alkanes and alkenes. The aldehyde decarbonylase is related to the broadly functional nonheme diiron enzymes. Heterologous expression of the alkane operon in Escherichia coli leads to the production and secretion of C13 to C17 mixtures of alkanes and alkenes. These genes and enzymes can now be leveraged for the simple and direct conversion of renewable raw materials to fungible hydrocarbon fuels.

  14. Computational Study of Low-Temperature Catalytic C-C Bond Activation of Alkanes for Portable Power

    Science.gov (United States)

    2013-06-05

    the RhCl3 system. Our initial computations regarding this system showed that • RhII chloride salts are stable in a mixture of RhI and RhIII, so that...inhibiting the reaction. We found that Fluorinated phosphines are sufficiently π-accepting to satisfy this role. In our next step, we wanted to determine...flames” Proc. Comb. Inst. 2005, 30, 439–446 4. A. Onopchenko, J.G.D. Schulz “Oxidation of butane with cobalt salts and oxygen via electron

  15. Alkane dimers interaction

    DEFF Research Database (Denmark)

    Ferrighi, Lara; Madsen, Georg Kent Hellerup; Hammer, Bjørk

    2010-01-01

    The interaction energies of a series of n-alkane dimers, from methane to decane, have been investigated with Density Functional Theory (DFT), using the MGGA-M06-L density functional. The results are compared both to the available wavefunction-based values as well as to dispersion corrected DFT...

  16. At what chain length do unbranched alkanes prefer folded conformations?

    CERN Document Server

    Byrd, Jason N; Montgomery, John A

    2013-01-01

    Short unbranched alkanes are known to prefer linear conformations, while long unbranched alkanes are folded. It is not known with certainty at what chain length the linear conformation is no longer the global minimum. To clarify this point, we use {\\it ab initio} and density functional methods to compute the relative energies of the linear and hairpin alkane conformers for increasing chain lengths. Extensive electronic structure calculations are performed to obtain optimized geometries, harmonic frequencies and accurate single point energies for the selected alkane conformers from octane through octadecane. Benchmark CCSD(T)/cc-pVTZ single point calculations are performed for chains through tetradecane, while approximate methods are required for the longer chains up to octadecane. Using frozen natural orbitals to unambiguously truncate the virtual orbital space we are able to compute composite CCSD FNO(T) single point energies for all the chain lengths. This approximate composite method has significant comput...

  17. Computational Evidence for the Smallest Boron Nanotube

    Institute of Scientific and Technical Information of China (English)

    Xian Jie LIN; Dong Ju ZHANG; Cheng Bu LIU

    2006-01-01

    The structure of boron nanotubes (BNTs) was found not to be limited to hexagonal pyramidal structures. Based on density functional theory calculations we provided evidence for the smallest boron nanotube, a geometrical analog of the corresponding carbon nanotube. As shown by our calculations, the smallest BNT possesses highly structural, dynamical, and thermal stability, which should be interest for attempts at its synthesis.

  18. An Introduction to Computer Forensics: Gathering Evidence in a Computing Environment

    Directory of Open Access Journals (Sweden)

    Henry B. Wolfe

    2001-01-01

    Full Text Available Business has become increasingly dependent on the Internet and computing to operate. It has become apparent that there are issues of evidence gathering in a computing environment, which by their nature are technical and different to other forms of evidence gathering, that must be addressed. This paper offers an introduction to some of the technical issues surrounding this new and specialized field of Computer Forensics. It attempts to identify and describe sources of evidence that can be found on disk data storage devices in the course of an investigation. It also considers sources of copies of email, which can be used in evidence, as well as case building.

  19. Striking difference between alkane and olefin metathesis using the well-defined precursor [≡Si-O-WMe5]: Indirect evidence in favour of a bifunctional catalyst W alkylidene-hydride

    KAUST Repository

    Riache, Nassima

    2015-01-01

    Metathesis of linear alkanes catalyzed by the well-defined precursor (≡Si-O-WMe5) affords a wide distribution of linear alkanes from methane up to triacontane. Olefin metathesis using the same catalyst and under the same reaction conditions gives a very striking different distribution of linear α-olefins and internal olefins. This shows that olefin and alkane metathesis processes occur via very different pathways.

  20. Nanorheology of Liquid Alkanes

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, S.A., Cochran, H.D., Cummings, P.T. [Tennessee Univ., Knoxville, TN (United States). Dept. of Chemical Engineering], [Oak Ridge National Lab., TN (United States)

    1997-09-01

    We report molecular dynamics simulations of liquid alkanes, squalane and tetracosane, confined between moving walls to which butane chains are tethered, effectively screening the details of the wall. As in an experiment, heat is removed by thermostatting the tethered molecules. Results obtained at high strain rates, typical of practical applications, suggest little or no difference between the bulk rheology and confined flow, and the occurrence of a high degree of slip at the wall-fluid interface at the conditions studied. At relatively low velocities and high densities, tetracosane shows the formation of fully-extended chains at certain wall spacings.

  1. [Forensic evidence-based medicine in computer communication networks].

    Science.gov (United States)

    Qiu, Yun-Liang; Peng, Ming-Qi

    2013-12-01

    As an important component of judicial expertise, forensic science is broad and highly specialized. With development of network technology, increasement of information resources, and improvement of people's legal consciousness, forensic scientists encounter many new problems, and have been required to meet higher evidentiary standards in litigation. In view of this, evidence-based concept should be established in forensic medicine. We should find the most suitable method in forensic science field and other related area to solve specific problems in the evidence-based mode. Evidence-based practice can solve the problems in legal medical field, and it will play a great role in promoting the progress and development of forensic science. This article reviews the basic theory of evidence-based medicine and its effect, way, method, and evaluation in the forensic medicine in order to discuss the application value of forensic evidence-based medicine in computer communication networks.

  2. Confined thin films of linear and branched alkanes

    NARCIS (Netherlands)

    Dijkstra, Marjolein

    1997-01-01

    We report computer simulations in the Grand canonical ensemble of a system of several alkanes between two solid surfaces. We computed the solvation force exerted by the fluid on the plates. The solvation force for linear decane oscillates with distance with a periodicity close to the width of the mo

  3. [Computer work and De Quervain's tenosynovitis: an evidence based approach].

    Science.gov (United States)

    Gigante, M R; Martinotti, I; Cirla, P E

    2012-01-01

    The debate around the role of the work at personal computer as cause of De Quervain's Tenosynovitis was developed partially, without considering multidisciplinary available data. A systematic review of the literature, using an evidence-based approach, was performed. In disorders associated with the use of VDU, we must distinguish those at the upper limbs and among them those related to an overload. Experimental studies on the occurrence of De Quervain's Tenosynovitis are quite limited, as well as clinically are quite difficult to prove the professional etiology, considering the interference due to other activities of daily living or to the biological susceptibility (i.e. anatomical variability, sex, age, exercise). At present there is no evidence of any connection between De Quervain syndrome and time of use of the personal computer or keyboard, limited evidence of correlation is found with time using a mouse. No data are available regarding the use exclusively or predominantly for personal laptops or mobile "smart phone".

  4. Tools for characterizing the whole‐cell bio‐oxidation of alkanes at microscale

    DEFF Research Database (Denmark)

    Grant, Chris; da Silva Damas Pinto, Ana Catarina; Lui, Hai‐Po;

    2012-01-01

    ‐dodecanol after 48 h obtained in a stirred tank reactor. Using the microwell platform we present a rapid and systematic approach to identify the key bottlenecks in the bio‐oxidation of long‐chain alkanes using Escherichia coli expressing the alkane hydroxylase (alkB) complex. The results indicate that mass...... time, this in vivo rate difference is within the range reported for the purified enzyme. Finally, the results obtained also provide strong evidence that the mechanism of E. coli interaction with alkanes is mainly via uptake of alkanes dissolved in the aqueous phase rather than by direct cell...

  5. Selective electrophilic activation of alkanes

    Energy Technology Data Exchange (ETDEWEB)

    Sommer, J.; Bukala, J. (Universite Louis Pasteur, Strasbourg (France))

    1993-07-01

    One major drawback for the direct use of alkanes as chemicals is their chemical inertness toward most of the usual reagents. For this reason, costly, large-scale refinery operations such as catalytic reforming and vapocracking are needed, which necessitate the use of noble metal catalysts and/or high temperature to activate the strong C-H and C-C bonds and yield the primary chemical building blocks such as ethylene, propylene, butadiene, benzene, toluene, and xylene. In response to the challenge to use more economically a larger share of alkanes, and increasing number of research groups are working on the activation functionalization processes of the saturated hydrocarbon C-H bond. The goal is to overcome smoothly and selectively the chemical inertness of the starting (paraffinic) material. A book and special issue have been published recently on this subject. Protonated alkanes are reaction intermediates in superacid-catalyzed protolysis. Protonation occurs on all C-C and C-H [sigma]-bonds independently of the further reactivity of the protonated alkane as confirmed by using [sup 2]H labeled superacids. Direct and selective C-H bond protolysis is limited to tertiary alkanes whereas linear alkanes undergo less selective C-C bond cleavage. 31 refs., 3 figs.

  6. Structural insights into diversity and n-alkane biodegradation mechanisms of alkane hydroxylases

    OpenAIRE

    Yurui eJi; Guannan eMao; Yingying eWang; Mark eBartlam

    2013-01-01

    Environmental microbes utilize four degradation pathways for the oxidation of n-alkanes. Although the enzymes degrading n-alkanes in different microbes may vary, enzymes functioning in the first step in the aerobic degradation of alkanes all belong to the alkane hydroxylases. Alkane hydroxylases are a class of enzymes that insert oxygen atoms derived from molecular oxygen into different sites of the alkane terminus (or termini) depending on the type of enzymes. In this review, we summarize th...

  7. Excessive computer game playing: evidence for addiction and aggression?

    Science.gov (United States)

    Grüsser, S M; Thalemann, R; Griffiths, M D

    2007-04-01

    Computer games have become an ever-increasing part of many adolescents' day-to-day lives. Coupled with this phenomenon, reports of excessive gaming (computer game playing) denominated as "computer/video game addiction" have been discussed in the popular press as well as in recent scientific research. The aim of the present study was the investigation of the addictive potential of gaming as well as the relationship between excessive gaming and aggressive attitudes and behavior. A sample comprising of 7069 gamers answered two questionnaires online. Data revealed that 11.9% of participants (840 gamers) fulfilled diagnostic criteria of addiction concerning their gaming behavior, while there is only weak evidence for the assumption that aggressive behavior is interrelated with excessive gaming in general. Results of this study contribute to the assumption that also playing games without monetary reward meets criteria of addiction. Hence, an addictive potential of gaming should be taken into consideration regarding prevention and intervention.

  8. Evidence for weakly bound electrons in non-irradiated alkane crystals. The electrons as a probe of structural differences in crystals

    CERN Document Server

    Pietrow, M; Misiak, L E; Kornarzynski, K; Szurkowski, J; Rochowski, P; Grzegorczyk, M

    2014-01-01

    It is generally assumed that weakly bound (trapped) electrons in organic solids come only from radiolytical (or photochemical) processes like ionization caused by an excited positron entering the sample. This paper presents an evidence for the presence of these electrons in non-irradiated samples of docosane. We argue that these electrons can be located (trapped) either in interlamellar gaps or in spaces made by non-planar conformers. The electrons from the former ones are bound more weakly than those from the latter ones. The origin of Vis absorption for the samples is explained. These spectra can be used as a probe indicating differences in the solid structures of hydrocarbons.

  9. Alkane desaturation by concerted double hydrogen atom transfer to benzyne.

    Science.gov (United States)

    Niu, Dawen; Willoughby, Patrick H; Woods, Brian P; Baire, Beeraiah; Hoye, Thomas R

    2013-09-26

    The removal of two vicinal hydrogen atoms from an alkane to produce an alkene is a challenge for synthetic chemists. In nature, desaturases and acetylenases are adept at achieving this essential oxidative functionalization reaction, for example during the biosynthesis of unsaturated fatty acids, eicosanoids, gibberellins and carotenoids. Alkane-to-alkene conversion almost always involves one or more chemical intermediates in a multistep reaction pathway; these may be either isolable species (such as alcohols or alkyl halides) or reactive intermediates (such as carbocations, alkyl radicals, or σ-alkyl-metal species). Here we report a desaturation reaction of simple, unactivated alkanes that is mechanistically unique. We show that benzynes are capable of the concerted removal of two vicinal hydrogen atoms from a hydrocarbon. The discovery of this exothermic, net redox process was enabled by the simple thermal generation of reactive benzyne intermediates through the hexadehydro-Diels-Alder cycloisomerization reaction of triyne substrates. We are not aware of any single-step, bimolecular reaction in which two hydrogen atoms are simultaneously transferred from a saturated alkane. Computational studies indicate a preferred geometry with eclipsed vicinal C-H bonds in the alkane donor.

  10. Evidence for weakly bound electrons in non-irradiated alkane crystals: The electrons as a probe of structural differences in crystals

    Energy Technology Data Exchange (ETDEWEB)

    Pietrow, M., E-mail: mrk@kft.umcs.lublin.pl; Misiak, L. E. [Institute of Physics, M. Curie-Skłodowska University, ul. Pl. M. Curie-Skłodowskiej 1, 20-031 Lublin (Poland); Gagoś, M. [Department of Cell Biology, Institute of Biology and Biochemistry, Maria Curie-Skłodowska University, ul. Akademicka 19, 20-033 Lublin (Poland); Kornarzyński, K. [Department of Physics, University of Life Sciences in Lublin, Akademicka 13, 20-950 Lublin (Poland); Szurkowski, J.; Grzegorczyk, M. [Institute of Experimental Physics, University of Gdańsk, Wita Stwosza 57, 80-952 Gdańsk (Poland); Rochowski, P. [Institute of Experimental Physics, University of Gdańsk, Wita Stwosza 57, 80-952 Gdańsk (Poland); Pomeranian University in Słupsk, Arciszewskiego 22b, 76-200 Słupsk (Poland)

    2015-02-14

    It is generally assumed that weakly bound (trapped) electrons in organic solids come only from radiolytical (or photochemical) processes like ionization caused by an excited positron entering the sample. This paper presents evidence for the presence of these electrons in non-irradiated samples of docosane. This can be due to the triboelectrification process. We argue that these electrons can be located (trapped) either in interlamellar gaps or in spaces made by non-planar conformers. Electrons from the former ones are bound more weakly than electrons from the latter ones. The origin of Vis absorption for the samples is explained. These spectra can be used as a probe indicating differences in the solid structures of hydrocarbons.

  11. Liquid-liquid interfaces of semifluorinated alkane diblock copolymers with water, alkanes, and perfluorinated alkanes.

    Science.gov (United States)

    Pierce, Flint; Tsige, Mesfin; Perahia, Dvora; Grest, Gary S

    2008-12-18

    The liquid-liquid interface between semifluorinated alkane diblock copolymers of the form F3C(CF2)n-1-(CH2)m-1CH3 and water, protonated alkanes, and perfluorinated alkanes are studied by fully atomistic molecular dynamics simulations. A modified version of the OPLS-AA (Optimized Parameter for Liquid Simulation All-Atom) force field of Jorgensen et al. has been used to study the interfacial behavior of semifluorinated diblocks. Aqueous interfaces are found to be sharp, with correspondingly large values of the interfacial tension. Due to the reduced hydrophobicity of the protonated block compared to the fluorinated block, hydrogen enhancement is observed at the interface. Water dipoles in the interfacial region are found to be oriented nearly parallel to the liquid-liquid interface. A number of protonated alkanes and perfluorinated alkanes are found to be mutually miscible with the semifluorinated diblocks. For these liquids, interdiffusion follows the expected Fickian behavior, and concentration-dependent diffusivities are determined.

  12. Theoretical study of the rhenium–alkane interaction in transition metal–alkane σ-complexes

    OpenAIRE

    Cobar, Erika A.; Khaliullin, Rustam Z.; Bergman, Robert G.; Head-Gordon, Martin

    2007-01-01

    Metal–alkane binding energies have been calculated for [CpRe(CO)2](alkane) and [(CO)2M(C5H4)CC(C5H4)M(CO)2](alkane), where M = Re or Mn. Calculated binding energies were found to increase with the number of metal–alkane interaction sites. In all cases examined, the manganese–alkane binding energies were predicted to be significantly lower than those for the analogous rhenium–alkane complexes. The metal (Mn or Re)–alkane interaction was predicted to be primarily one of charge transfer, both fr...

  13. Modeling the Role of Alkanes, Polycyclic Aromatic Hydrocarbons, and Their Oligomers in Secondary Organic Aerosol Formation

    Science.gov (United States)

    A computationally efficient method to treat secondary organic aerosol (SOA) from various length and structure alkanes as well as SOA from polycyclic aromatic hydrocarbons (PAHs) is implemented in the Community Multiscale Air Quality (CMAQ) model to predict aerosol concentrations ...

  14. Evaporating Drops of Alkane Mixtures

    CERN Document Server

    Gu'ena, G; Poulard, C; Cazabat, Anne-Marie; Gu\\'{e}na, Geoffroy; Poulard, Christophe

    2005-01-01

    Alkane mixtures are model systems where the influence of surface tension gradients during the spreading and the evaporation of wetting drops can be easily studied. The surface tension gradients are mainly induced by concentration gradients, mass diffusion being a stabilising process. Depending on the relative concentration of the mixture, a rich pattern of behaviours is obtained.

  15. Evaporating Drops of Alkane Mixtures

    OpenAIRE

    Guéna, Geoffroy; Poulard, Christophe; Cazabat, Anne-Marie

    2005-01-01

    22 pages 9 figures; Alkane mixtures are model systems where the influence of surface tension gradients during the spreading and the evaporation of wetting drops can be easily studied. The surface tension gradients are mainly induced by concentration gradients, mass diffusion being a stabilising process. Depending on the relative concentration of the mixture, a rich pattern of behaviours is obtained.

  16. Catalytic conversion of light alkanes

    Energy Technology Data Exchange (ETDEWEB)

    Lyons, J.E.

    1992-06-30

    The second Quarterly Report of 1992 on the Catalytic Conversion of Light Alkanes reviews the work done between April 1, 1992 and June 31, 1992 on the Cooperative Agreement. The mission of this work is to devise a new catalyst which can be used in a simple economic process to convert the light alkanes in natural gas to oxygenate products that can either be used as clean-burning, high octane liquid fuels, as fuel components or as precursors to liquid hydrocarbon uwspomdon fuel. During the past quarter we have continued to design, prepare, characterize and test novel catalysts for the mild selective reaction of light hydrocarbons with air or oxygen to produce alcohols directly. These catalysts are designed to form active metal oxo (MO) species and to be uniquely active for the homolytic cleavage of the carbon-hydrogen bonds in light alkanes producing intermediates which can form alcohols. We continue to investigate three molecular environments for the active catalytic species that we are trying to generate: electron-deficient macrocycles (PHASE I), polyoxometallates (PHASE II), and regular oxidic lattices including zeolites and related structures as well as other molecular surface structures having metal oxo groups (PHASE I).

  17. Alkane biohydroxylation: Interests, constraints and future developments.

    Science.gov (United States)

    Soussan, Laurence; Pen, Nakry; Belleville, Marie-Pierre; Marcano, José Sanchez; Paolucci-Jeanjean, Delphine

    2016-03-20

    Alkanes constitute one of the vastest reserves of raw materials for the production of fine chemicals. This paper focuses on recent advances in alkane biohydroxylation, i.e. the bioactivation of alkanes into their corresponding alcohols. Enzyme and whole-cell biocatalysts have been reviewed. Process considerations to implement such biocatalysts in bioreactors at large scale by coupling the bioconversion with cofactor regeneration and product removal are also discussed.

  18. Crystallization features of normal alkanes in confined geometry.

    Science.gov (United States)

    Su, Yunlan; Liu, Guoming; Xie, Baoquan; Fu, Dongsheng; Wang, Dujin

    2014-01-21

    ) confining environment. We have studied multiple parameters of these microencapsulated n-alkanes, including surface freezing, metastability of the rotator phase, and the phase separation behaviors of n-alkane mixtures using differential scanning calorimetry (DSC), temperature-dependent X-ray diffraction (XRD), and variable-temperature solid-state nuclear magnetic resonance (NMR). Our investigations revealed new direct evidence for the existence of surface freezing in microencapsulated n-alkanes. By examining the differences among chain packing and nucleation kinetics between bulk alkane solid solutions and their microencapsulated counterparts, we also discovered a mechanism responsible for the formation of a new metastable bulk phase. In addition, we found that confinement suppresses lamellar ordering and longitudinal diffusion, which play an important role in stabilizing the binary n-alkane solid solution in microcapsules. Our work also provided new insights into the phase separation of other mixed system, such as waxes, lipids, and polymer blends in confined geometry. These works provide a profound understanding of the relationship between molecular structure and material properties in the context of crystallization and therefore advance our ability to improve applications incorporating polymeric and molecular materials.

  19. Conformation of alkanes in the gas phase and pure liquids.

    Science.gov (United States)

    Thomas, Laura L; Christakis, Theodore J; Jorgensen, William L

    2006-10-26

    Monte Carlo (MC) statistical mechanics simulations have been carried out for the homologous alkane series of n-butane through n-dodecane in the gas phase and for the pure liquids at 298 K and 1 atm using the OPLS-AA force field. The study addresses potential cumulative deviations of computed properties and potential conformational differences between the gas phase and pure liquids, for example, from self-solvation in the gas phase. The average errors in comparison with experimental data for the computed densities and heats of vaporization are modest at 0.7% and 6.9%, respectively. Also, the invariant gas and liquid-phase results for average end-to-end distances and percentages of trans conformations for each nonterminal C-C bond assert that the conformer populations are not altered upon transfer from the gas phase to the pure liquid for the n-alkanes in this size range. Average end-to-end distances were also computed from the results of conformational searches and corroborated the MC findings. Quantitatively, the OPLS-AA result for the trans population of the C3-C4 bond in n-undecane is in close agreement with the findings from (13)C NMR experiments. Finally, previous work on determining the shortest n-alkane that does not have an all-trans global energy minimum has been extended. The smallest n-alkane with a hairpin geometry that is lower in energy than the all-trans conformer occurs for C(22)H(46) with OPLS-AA, though with a correction for GG sequences, the true turning point is likely in the C(16)-C(18) range.

  20. Alkane-Based Urethane Potting Compounds

    Science.gov (United States)

    Morris, D. E.

    1986-01-01

    New low viscosity urethanes easily mixed, molded, and outgassed. Alkane-based urethanes resist hydrolysis and oxidation and have excellent dielectric properties. Low-viscosity alkane-based urethane prepolymer prepared by one-step reaction of either isophorone diisocyanate or methyl-bis (4-cyclohexyl isocyanate) with hydrogenated, hydroxy-terminated polybutadiene (HTPBD).

  1. The early (pre-11 Ma) existence and disparate response of C4 plant in the Indian sub-continent: Evidences from n-alkane isotopic ratios of NW Indian Siwalik paleosol

    Science.gov (United States)

    Ghosh, Sambit; Sanyal, Prasanta; Kumar, Rohtash

    2016-04-01

    The appearance and expansion of C4 plant during the late Miocene was first documented from Siwalik sections of Indian sub-continent using carbon isotope ratio of soil carbonate, soil organic matter and fossil tooth enamel. The timing and nature of C4 plant evolution documented from different Siwalik sections of Indian sub-continent were not equivocal. Even from a particular region, the timing and nature of ecological shift was interpreted differently. The lack of modern data set from the Indian sub-continent might be one of the reasons for differences in results. Moreover the pristine isotopic character of soil organic matter and soil carbonate are prone to alteration during diagenesis. To resolve all the issues, NW Siwalik paleosol (n = 74) derived leaf wax long chain n-alkane δ13C value, a robust proxy, has been used to reconstruct exact timing of C4 plant appearance and its nature of expansion. The average long chain n-alkane δ13C value of modern C3-C4 plants surviving in the Gangetic plain have been used as reference to understand the past vegetation survived in the Siwalik floodplain. The paleosol derived long chain n-alkane δ13C values from Naladkhad (11.6 to 8.8 Ma) and Ranital (11.1 to 6.9 Ma) sections of Kangra sub-basin indicate presence of ˜ 40 % C4 plants at ˜11 Ma. Such significant abundance of C4 plants at ˜11 Ma indicate an early appearance of C4 plants compared to the previously published data. The abundance of C4 plants have increased gradually both in Ranital (9.7 Ma to 6.9 Ma) and Jabbarkhad (6.2 Ma to 2.7 Ma) sections of Kangra sub-basin whereas the C4 plant abundance showed large fluctuations in the Haripur Khol section (5.7 Ma to 1.6 Ma) of Subathu sub-basin. The paleosol derived leaf wax long chain n-alkane δD values measured from the Kangra and Subathu sub-basin indicate three phases of high monsoon at ˜ 9 Ma, ˜5.5 Ma and ˜ 3.5 Ma. The varied response of C4 plant abundance with monsoonal rainfall amount and fluvial architectural

  2. Predicting hydrophobic solvation by molecular simulation: 1. Testing united-atom alkane models.

    Science.gov (United States)

    Jorge, Miguel; Garrido, Nuno M; Simões, Carlos J V; Silva, Cândida G; Brito, Rui M M

    2017-03-05

    We present a systematic test of the performance of three popular united-atom force fields-OPLS-UA, GROMOS and TraPPE-at predicting hydrophobic solvation, more precisely at describing the solvation of alkanes in alkanes. Gibbs free energies of solvation were calculated for 52 solute/solvent pairs from Molecular Dynamics simulations and thermodynamic integration making use of the IBERCIVIS volunteer computing platform. Our results show that all force fields yield good predictions when both solute and solvent are small linear or branched alkanes (up to pentane). However, as the size of the alkanes increases, all models tend to increasingly deviate from experimental data in a systematic fashion. Furthermore, our results confirm that specific interaction parameters for cyclic alkanes in the united-atom representation are required to account for the additional excluded volume within the ring. Overall, the TraPPE model performs best for all alkanes, but systematically underpredicts the magnitude of solvation free energies by about 6% (RMSD of 1.2 kJ/mol). Conversely, both GROMOS and OPLS-UA systematically overpredict solvation free energies (by ∼13% and 15%, respectively). The systematic trends suggest that all models can be improved by a slight adjustment of their Lennard-Jones parameters. © 2016 Wiley Periodicals, Inc.

  3. Heritability in Cognitive Performance: Evidence Using Computer-Based Testing

    Science.gov (United States)

    Hervey, Aaron S.; Greenfield, Kathryn; Gualtieri, C. Thomas

    2012-01-01

    There is overwhelming evidence of genetic influence on cognition. The effect is seen in general cognitive ability, as well as in specific cognitive domains. A conventional assessment approach using face-to-face paper and pencil testing is difficult for large-scale studies. Computerized neurocognitive testing is a suitable alternative. A total of…

  4. Multiple alkane hydroxylase systems in a marine alkane degrader, Alcanivorax dieselolei B-5.

    Science.gov (United States)

    Liu, Chenli; Wang, Wanpeng; Wu, Yehui; Zhou, Zhongwen; Lai, Qiliang; Shao, Zongze

    2011-05-01

    Alcanivorax dieselolei strain B-5 is a marine bacterium that can utilize a broad range of n-alkanes (C(5) -C(36) ) as sole carbon source. However, the mechanisms responsible for this trait remain to be established. Here we report on the characterization of four alkane hydroxylases from A. dieselolei, including two homologues of AlkB (AlkB1 and AlkB2), a CYP153 homologue (P450), as well as an AlmA-like (AlmA) alkane hydroxylase. Heterologous expression of alkB1, alkB2, p450 and almA in Pseudomonas putida GPo12 (pGEc47ΔB) or P. fluorescens KOB2Δ1 verified their functions in alkane oxidation. Quantitative real-time RT-PCR analysis showed that these genes could be induced by alkanes ranging from C(8) to C(36) . Notably, the expression of the p450 and almA genes was only upregulated in the presence of medium-chain (C(8) -C(16) ) or long-chain (C(22) -C(36) ) n-alkanes, respectively; while alkB1 and alkB2 responded to both medium- and long-chain n-alkanes (C(12) -C(26) ). Moreover, branched alkanes (pristane and phytane) significantly elevated alkB1 and almA expression levels. Our findings demonstrate that the multiple alkane hydroxylase systems ensure the utilization of substrates of a broad chain length range.

  5. Supported organoiridium catalysts for alkane dehydrogenation

    Science.gov (United States)

    Baker, R. Thomas; Sattelberger, Alfred P.; Li, Hongbo

    2013-09-03

    Solid supported organoiridium catalysts, a process for preparing such solid supported organoiridium catalysts, and the use of such solid supported organoiridium catalysts in dehydrogenation reactions of alkanes is provided. The catalysts can be easily recovered and recycled.

  6. Changes in iso- and n-alkane distribution during biodegradation of crude oil under nitrate and sulphate reducing conditions.

    Science.gov (United States)

    Hasinger, Marion; Scherr, Kerstin E; Lundaa, Tserennyam; Bräuer, Leopold; Zach, Clemens; Loibner, Andreas Paul

    2012-02-20

    Crude oil consists of a large number of hydrocarbons with different susceptibility to microbial degradation. The influence of hydrocarbon structure and molecular weight on hydrocarbon biodegradation under anaerobic conditions is not fully explored. In this study oxygen, nitrate and sulphate served as terminal electron acceptors (TEAs) for the microbial degradation of a paraffin-rich crude oil in a freshly contaminated soil. During 185 days of incubation, alkanes from n-C11 to n-C39, three n- to iso-alkane ratios commonly used as weathering indicators and the unresolved complex mixture (UCM) were quantified and statistically analyzed. The use of different TEAs for hydrocarbon degradation resulted in dissimilar degradative patterns for n- and iso-alkanes. While n-alkane biodegradation followed well-established patterns under aerobic conditions, lower molecular weight alkanes were found to be more recalcitrant than mid- to high-molecular weight alkanes under nitrate-reducing conditions. Biodegradation with sulphate as the TEA was most pronounced for long-chain (n-C32 to n-C39) alkanes. The observation of increasing ratios of n-C17 to pristane and of n-C18 to phytane provides first evidence of the preferential degradation of branched over normal alkanes under sulphate reducing conditions. The formation of distinctly different n- and iso-alkane biodegradation fingerprints under different electron accepting conditions may be used to assess the occurrence of specific degradation processes at a contaminated site. The use of n- to iso-alkane ratios for this purpose may require adjustment if applied for anaerobic sites.

  7. Solar photothermochemical alkane reverse combustion.

    Science.gov (United States)

    Chanmanee, Wilaiwan; Islam, Mohammad Fakrul; Dennis, Brian H; MacDonnell, Frederick M

    2016-03-01

    A one-step, gas-phase photothermocatalytic process for the synthesis of hydrocarbons, including liquid alkanes, aromatics, and oxygenates, with carbon numbers (Cn) up to C13, from CO2 and water is demonstrated in a flow photoreactor operating at elevated temperatures (180-200 °C) and pressures (1-6 bar) using a 5% cobalt on TiO2 catalyst and under UV irradiation. A parametric study of temperature, pressure, and partial pressure ratio revealed that temperatures in excess of 160 °C are needed to obtain the higher Cn products in quantity and that the product distribution shifts toward higher Cn products with increasing pressure. In the best run so far, over 13% by mass of the products were C5+ hydrocarbons and some of these, i.e., octane, are drop-in replacements for existing liquid hydrocarbons fuels. Dioxygen was detected in yields ranging between 64% and 150%. In principle, this tandem photochemical-thermochemical process, fitted with a photocatalyst better matched to the solar spectrum, could provide a cheap and direct method to produce liquid hydrocarbons from CO2 and water via a solar process which uses concentrated sunlight for both photochemical excitation to generate high-energy intermediates and heat to drive important thermochemical carbon-chain-forming reactions.

  8. Metathesis of alkanes and related reactions

    KAUST Repository

    Basset, Jean-Marie

    2010-02-16

    (Figure Presented) The transformation of alkanes remains a difficult challenge because of the relative inertness of the C-H and C-C bonds. The rewards for asserting synthetic control over unfunctionalized, saturated hydrocarbons are considerable, however, because converting short alkanes into longer chain analogues is usually a value-adding process. Alkane metathesis is a novel catalytic and direct transformation of two molecules of a given alkane into its lower and higher homologues; moreover, the process proceeds at relatively low temperature (ambient conditions or higher). It was discovered through the use of a silica-supported tantalum hydride, (=SiO)2TaH, a multifunctional catalyst with a single site of action. This reaction completes the story of the metathesis reactions discovered over the past 40 years: olefin metathesis, alkyne metathesis, and ene-yne cyclizations. In this Account, we examine the fundamental mechanistic aspects of alkane metathesis as well as the novel reactions that have been derived from its study. The silica-supported tantalum hydride catalyst was developed as the result of systematic and meticulous studies of the interaction between oxide supports and organometallic complexes, a field of study denoted surface organometallic chemistry (SOMC). A careful examination of this surface-supported tantalum hydride led to the later discovery of aluminasupported tungsten hydride, W(H)3/Al 2O3, which proved to be an even better catalyst for alkane metathesis. Supported tantalum and tungsten hydrides are highly unsaturated, electron-deficient species that are very reactive toward the C-H and C-C bonds of alkanes. They show a great versatility in various other reactions, such as cross-metathesis between methane and alkanes, cross-metathesis between toluene and ethane, or even methane nonoxidative coupling. Moreover, tungsten hydride exhibits a specific ability in the transformation of isobutane into 2,3-dimethylbutane as well as in the metathesis of

  9. Evidence-based guidelines for the wise use of computers by children: physical development guidelines.

    Science.gov (United States)

    Straker, L; Maslen, B; Burgess-Limerick, R; Johnson, P; Dennerlein, J

    2010-04-01

    Computer use by children is common and there is concern over the potential impact of this exposure on child physical development. Recently principles for child-specific evidence-based guidelines for wise use of computers have been published and these included one concerning the facilitation of appropriate physical development. This paper reviews the evidence and presents detailed guidelines for this principle. The guidelines include encouraging a mix of sedentary and whole body movement tasks, encouraging reasonable postures during computing tasks through workstation, chair, desk, display and input device selection and adjustment and special issues regarding notebook computer use and carriage, computing skills and responding to discomfort. The evidence limitations highlight opportunities for future research. The guidelines themselves can inform parents and teachers, equipment designers and suppliers and form the basis of content for teaching children the wise use of computers. STATEMENT OF RELEVANCE: Many children use computers and computer-use habits formed in childhood may track into adulthood. Therefore child-computer interaction needs to be carefully managed. These guidelines inform those responsible for children to assist in the wise use of computers.

  10. Evolution of an alkane-inducible biosensor for increased responsiveness to short-chain alkanes.

    Science.gov (United States)

    Reed, Ben; Blazeck, John; Alper, Hal

    2012-04-15

    Synthetic alkane-inducible biosensors have applications as detectors for environmental hydrocarbon contamination and as novel inducible expression systems with low-cost inducers. Here, we have assembled and evolved an alkane-responsive biosensor with a fluorescence output signal in Escherichia coli by utilizing regulatory machinery from Pseudomonas putida's alkane metabolism. Within our system, the transcriptional regulator, AlkSp, is activated by the presence of alkanes and binds to the P(alkB) promoter, stimulating transcription of a Green Fluorescent Protein reporter. Through two successive rounds of directed evolution via error prone PCR and fluorescence activated cell sorting, we isolated alkS mutants enabling up to a 5 fold increase in fluorescence output signal in response to short-chain alkanes such as hexane and pentane. Further characterization of selected mutants demonstrated altered responsiveness to a wide range of linear alkanes (pentane to dodecane). Sequence analysis highlighted the S470T mutation as a likely candidate responsible for increased effectiveness of the AlkS protein for short-chain alkanes. This work represents the first evolution of a synthetic biosensor system for alkanes.

  11. Structural Insights into Diversity and n-Alkane Biodegradation Mechanisms of Alkane Hydroxylases

    Directory of Open Access Journals (Sweden)

    Yurui eJi

    2013-03-01

    Full Text Available Environmental microbes utilize four degradation pathways for the oxidation of n-alkanes. Although the enzymes degrading n-alkanes in different microbes may vary, enzymes functioning in the first step in the aerobic degradation of alkanes all belong to the alkane hydroxylases. Alkane hydroxylases are a class of enzymes that insert oxygen atoms derived from molecular oxygen into different sites of the alkane terminus (or termini depending on the type of enzymes. In this review, we summarize the different types of alkane hydroxylases, their degrading steps and compare typical enzymes from various classes with regard to their three dimensional structures, in order to provide insights into how the enzymes mediate their different roles in the degradation of n-alkanes and what determines their different substrate ranges. Through the above analyses, the degrading mechanisms of enzymes can be elucidated and molecular biological methods can be utilized to expand their catalytic roles in the petrochemical industry or in bioremediation of oil-contaminated environments.

  12. Using the alkanes and long-chain alcohols of plant cuticular wax to estimate diet composition and the intakes of mixed forages in sheep consuming a known amount of alkane-labelled supplement.

    Science.gov (United States)

    Dove, H; Charmley, E

    2008-10-01

    almost two-thirds of estimates based on (LCOH + alkanes) had lower error than those found with alkanes alone. The results confirm that supplements labelled with plant wax components can be used to estimate forage intake, and also show that the LCOH are useful markers for estimating diet composition. Intakes were also computed using a combination of natural LCOH concentrations in the diet and the daily dose rate of even-chain alkanes administered by intra-ruminal device. Differences between intakes so estimated and the measured intakes were closely related to the difference in faecal recovery between the LCOH/alkane pair used to estimate intake, by an amount close to that expected on theoretical grounds. It is concluded that the use of plant wax LCOH, especially in combination with alkanes, will result in improved estimates of diet composition and intake in grazing animals.

  13. A Systematic Literature Review of Empirical Evidence on Computer Games and Serious Games

    Science.gov (United States)

    Connolly, Thomas M.; Boyle, Elizabeth A.; MacArthur, Ewan; Hainey, Thomas; Boyle, James M.

    2012-01-01

    This paper examines the literature on computer games and serious games in regard to the potential positive impacts of gaming on users aged 14 years or above, especially with respect to learning, skill enhancement and engagement. Search terms identified 129 papers reporting empirical evidence about the impacts and outcomes of computer games and…

  14. Defining a Standard for Reporting Digital Evidence Items in Computer Forensic Tools

    Science.gov (United States)

    Bariki, Hamda; Hashmi, Mariam; Baggili, Ibrahim

    Due to the lack of standards in reporting digital evidence items, investigators are facing difficulties in efficiently presenting their findings. This paper proposes a standard for digital evidence to be used in reports that are generated using computer forensic software tools. The authors focused on developing a standard digital evidence items by surveying various digital forensic tools while keeping in mind the legal integrity of digital evidence items. Additionally, an online questionnaire was used to gain the opinion of knowledgeable and experienced stakeholders in the digital forensics domain. Based on the findings, the authors propose a standard for digital evidence items that includes data about the case, the evidence source, evidence item, and the chain of custody. Research results enabled the authors in creating a defined XML schema for digital evidence items.

  15. Thermal analysis as an aid to forensics: Alkane melting and oxidative stability of wool

    Energy Technology Data Exchange (ETDEWEB)

    Alan Riga, D. [Professor of Chemistry, Cleveland State University and TechCon Inc., 6325 Aldenham Dr., Cleveland, OH 44143-3331 (United States)

    1998-12-21

    Interdisciplinary methods and thermal analytical techniques in particular are effective tools in aiding the identification and characterization of materials in question involved in civil or criminal law. Forensic material science uses systematic knowledge of the physical or material world gained through analysis, observation and experimentation. Thermal analytical data can be used to aid the legal system in interpreting technical variations in quite often a complex system.Calorimetry and thermal microscopic methods helped define a commercial product composed of alkanes that was involved in a major law suit. The solid-state structures of a number of normal alkanes have unique crystal structures. These alkanes melt and freeze below room temperature to more than 60C below zero. Mixtures of specific alkanes have attributes of pure chemicals. The X-ray diffraction structure of a mixture of alkanes is the same as a pure alkane, but the melting and freezing temperature are significantly lower than predicted. The jury ruled that the product containing n-alkanes had the appropriate melting characteristics. The thermal-physical properties made a commercial fluid truly unique and there was no advertising infringement according to the law and the jury trialA combination of thermogravimetry, differential thermal analysis, infrared spectroscopy and macrophotography were used to conduct an extensive modeling and analysis of physical evidence obtained in a mobile home fire and explosion. A person's death was allegedly linked to the misuse of a kerosene space heater. The thermal analytical techniques showed that external heating was the cause of the space heater's deformation, not a firing of the heater with gasoline and kerosene. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  16. Computer models and the evidence of anthropogenic climate change: An epistemology of variety-of-evidence inferences and robustness analysis.

    Science.gov (United States)

    Vezér, Martin A

    2016-04-01

    To study climate change, scientists employ computer models, which approximate target systems with various levels of skill. Given the imperfection of climate models, how do scientists use simulations to generate knowledge about the causes of observed climate change? Addressing a similar question in the context of biological modelling, Levins (1966) proposed an account grounded in robustness analysis. Recent philosophical discussions dispute the confirmatory power of robustness, raising the question of how the results of computer modelling studies contribute to the body of evidence supporting hypotheses about climate change. Expanding on Staley's (2004) distinction between evidential strength and security, and Lloyd's (2015) argument connecting variety-of-evidence inferences and robustness analysis, I address this question with respect to recent challenges to the epistemology robustness analysis. Applying this epistemology to case studies of climate change, I argue that, despite imperfections in climate models, and epistemic constraints on variety-of-evidence reasoning and robustness analysis, this framework accounts for the strength and security of evidence supporting climatological inferences, including the finding that global warming is occurring and its primary causes are anthropogenic.

  17. -Alkanes in surficial sediments of Visakhapatnam harbour, east coast of India

    Indian Academy of Sciences (India)

    V R Punyu; R R Harji; N B Bhosle; S S Sawant; K Venkat

    2013-04-01

    Surface sediments collected from 19 stations along Visakhapatnam harbour were analysed for organic carbon (OC), 13CoC, total lipids (TL), total hydrocarbon (THC), -alkane concentration and composition. OC, 13CoC, TL and THC ranged from 0.6% to 7.6%, -29.3 to -23.8‰, 300 to 14,948 g g−1 dw, and 0.2 to 2,277 g g−1 dw, respectively. Predominance of even carbon numbers -alkanes C12–C21 with carbon preference index (CPI) of < 1 suggests major microbial influence. Fair abundance of odd carbon number -alkanes in the range of C15–C22 and C23–C33 indicates some input from phytoplankton and terrestrial sources, respectively. Petrogenic input was evident from the presence of hopanes and steranes. The data suggest that organic matter (OM) sources varied spatially and were mostly derived from mixed source.

  18. n-Alkanes in surficial sediments of Visakhapatnam harbour, east coast of India

    Science.gov (United States)

    Punyu, V. R.; Harji, R. R.; Bhosle, N. B.; Sawant, S. S.; Venkat, K.

    2013-04-01

    Surface sediments collected from 19 stations along Visakhapatnam harbour were analysed for organic carbon (OC), δ 13Coc, total lipids (TL), total hydrocarbon (THC), n-alkane concentration and composition. OC, δ 13Coc, TL and THC ranged from 0.6% to 7.6%, -29.3 to -23.8‰, 300 to 14,948 \\upmu g g - 1 dw, and 0.2 to 2,277 \\upmu g g - 1 dw, respectively. Predominance of even carbon numbers n-alkanes C12-C21 with carbon preference index (CPI) of <1 suggests major microbial influence. Fair abundance of odd carbon number n-alkanes in the range of C15-C22 and C23-C33 indicates some input from phytoplankton and terrestrial sources, respectively. Petrogenic input was evident from the presence of hopanes and steranes. The data suggest that organic matter (OM) sources varied spatially and were mostly derived from mixed source.

  19. Enzymes and Genes Involved in Aerobic Alkane Degradation

    Directory of Open Access Journals (Sweden)

    Zongze eShao

    2013-05-01

    Full Text Available Alkanes are major constituents of crude oil. They are also present at low concentrations in diverse non-contaminated because many living organisms produce them as chemo-attractants or as protecting agents against water loss. Alkane degradation is a widespread phenomenon in nature. The numerous microorganisms, both prokaryotic and eukaryotic, capable of utilizing alkanes as a carbon and energy source, have been isolated and characterized. This review summarizes the current knowledge of how bacteria metabolize alkanes aerobically, with a particular emphasis on the oxidation of long-chain alkanes, including factors that are responsible for chemotaxis to alkanes , transport across cell membrane of alkanes , the regulation of alkane degradation gene and initial oxidation.

  20. Conversion of alkanes to organoseleniums and organotelluriums

    Energy Technology Data Exchange (ETDEWEB)

    Periana, Roy A.; Konnick, Michael M.; Hashiguchi, Brian G.

    2016-11-29

    The invention provides processes and materials for the efficient and costeffective functionalization of alkanes and heteroalkanes, comprising contacting the alkane or heteroalkane and a soft oxidizing electrophile comprising Se(VI) or Te(VI), in an acidic medium, optionally further comprising an aprotic medium, which can be carried out at a temperature of less than 300 C. Isolation of the alkylselenium or alkyltellurium intermediate allows the subsequent conversion to products not necessarily compatible with the initial reaction conditions, such as amines, stannanes, organosulfur compounds, acyls, halocarbons, and olefins.

  1. Improved Alkane Production in Nitrogen-Fixing and Halotolerant Cyanobacteria via Abiotic Stresses and Genetic Manipulation of Alkane Synthetic Genes.

    Science.gov (United States)

    Kageyama, Hakuto; Waditee-Sirisattha, Rungaroon; Sirisattha, Sophon; Tanaka, Yoshito; Mahakhant, Aparat; Takabe, Teruhiro

    2015-07-01

    Cyanobacteria possess the unique capacity to produce alkane. In this study, effects of nitrogen deficiency and salt stress on biosynthesis of alkanes were investigated in three kinds of cyanobacteria. Intracellular alkane accumulation was increased in nitrogen-fixing cyanobacterium Anabaena sp. PCC7120, but decreased in non-diazotrophic cyanobacterium Synechococcus elongatus PCC7942 and constant in a halotolerant cyanobacterium Aphanothece halophytica under nitrogen-deficient condition. We also found that salt stress increased alkane accumulation in Anabaena sp. PCC7120 and A. halophytica. The expression levels of two alkane synthetic genes were not upregulated significantly under nitrogen deficiency or salt stress in Anabaena sp. PCC7120. The transformant Anabaena sp. PCC7120 cells with additional alkane synthetic gene set from A. halophytica increased intracellular alkane accumulation level compared to control cells. These results provide a prospect to improve bioproduction of alkanes in nitrogen-fixing halotolerant cyanobacteria via abiotic stresses and genetic engineering.

  2. 40 CFR 721.535 - Halogenated alkane (generic).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Halogenated alkane (generic). 721.535... Substances § 721.535 Halogenated alkane (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as halogenated alkane (PMN P-01-433) is...

  3. 40 CFR 721.536 - Halogenated phenyl alkane.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Halogenated phenyl alkane. 721.536... Substances § 721.536 Halogenated phenyl alkane. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as halogenated phenyl alkane (PMN P-89-867)...

  4. 40 CFR 721.10163 - Chloro fluoro alkane (generic).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Chloro fluoro alkane (generic). 721... Substances § 721.10163 Chloro fluoro alkane (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as chloro fluoro alkane (PMN...

  5. Reflectance spectroscopy of organic compounds: 1. Alkanes

    Science.gov (United States)

    Clark, R.N.; Curchin, J.M.; Hoefen, T.M.; Swayze, G.A.

    2009-01-01

    Reflectance spectra of the organic compounds comprising the alkane series are presented from the ultraviolet to midinfrared, 0.35 to 15.5 /??m. Alkanes are hydrocarbon molecules containing only single carbon-carbon bonds, and are found naturally on the Earth and in the atmospheres of the giant planets and Saturn's moon, Titan. This paper presents the spectral properties of the alkanes as the first in a series of papers to build a spectral database of organic compounds for use in remote sensing studies. Applications range from mapping the environment on the Earth, to the search for organic molecules and life in the solar system and throughout the. universe. We show that the spectral reflectance properties of organic compounds are rich, with major diagnostic spectral features throughout the spectral range studied. Little to no spectral change was observed as a function of temperature and only small shifts and changes in the width of absorption bands were observed between liquids and solids, making remote detection of spectral properties throughout the solar system simpler. Some high molecular weight organic compounds contain single-bonded carbon chains and have spectra similar to alkanes even ' when they fall into other families. Small spectral differences are often present allowing discrimination among some compounds, further illustrating the need to catalog spectral properties for accurate remote sensing identification with spectroscopy.

  6. Nitrated metalloporphyrins as catalysts for alkane oxidation

    Science.gov (United States)

    Ellis, Jr., Paul E.; Lyons, James E.

    1992-01-01

    Alkanes are oxidized by contact with oxygen-containing gas in the presence as catalyst of a metalloporphyrin in which hydrogen atoms in the porphyrin ring have been replaced with one or more nitro groups. Hydrogen atoms in the porphyrin ring may also be substituted with halogen atoms.

  7. Adsorption of alkyltrimethylammonium bromides at water/alkane interfaces: competitive adsorption of alkanes and surfactants.

    Science.gov (United States)

    Fainerman, V B; Mucic, N; Pradines, V; Aksenenko, E V; Miller, R

    2013-11-12

    The adsorption of members of the homologous series of alkyl trimethylammonium bromides (C(n)TAB) is studied at water/alkane interfaces by drop profile analysis tensiometry. The results are discussed in terms of a competitive adsorption process of alkane and surfactant molecules. A thermodynamic model, derived originally for the adsorption of surfactant mixtures, is adapted such that it describes a competitive adsorption of the surfactant molecules from the aqueous phase and alkane molecules from the oil phase. This new model involves the interspecies attraction coefficient, which mutually increases the adsorption activities of the alkane and C(n)TAB. The effects of the alkyl chain length n of C(n)TABs and the influence of the number of C atoms in the alkane chain are discussed, and the physical quantities are compared to those determined at the aqueous solution/air interface. The new theoretical model for aqueous solution/oil interfaces is also compared to a theory that does not consider the adsorption of alkane. The proposed new model demonstrates good agreement with the experimental data.

  8. The long-chain alkane metabolism network of Alcanivorax dieselolei.

    Science.gov (United States)

    Wang, Wanpeng; Shao, Zongze

    2014-12-12

    Alkane-degrading bacteria are ubiquitous in marine environments, but little is known about how alkane degradation is regulated. Here we investigate alkane sensing, chemotaxis, signal transduction, uptake and pathway regulation in Alcanivorax dieselolei. The outer membrane protein OmpS detects the presence of alkanes and triggers the expression of an alkane chemotaxis complex. The coupling protein CheW2 of the chemotaxis complex, which is induced only by long-chain (LC) alkanes, sends signals to trigger the expression of Cyo, which participates in modulating the expression of the negative regulator protein AlmR. This change in turn leads to the expression of ompT1 and almA, which drive the selective uptake and hydroxylation of LC alkanes, respectively. AlmA is confirmed as a hydroxylase of LC alkanes. Additional factors responsible for the metabolism of medium-chain-length alkanes are also identified, including CheW1, OmpT1 and OmpT2. These results provide new insights into alkane metabolism pathways from alkane sensing to degradation.

  9. Evidence supporting the use of cone-beam computed tomography in orthodontics.

    NARCIS (Netherlands)

    Vlijmen, O.J.C. van; Kuijpers, M.A.R.; Berge, S.J.; Schols, J.G.J.H.; Maal, T.J.J.; Breuning, H.; Kuijpers-Jagtman, A.M.

    2012-01-01

    BACKGROUND: The authors conducted a systematic review of cone-beam computed tomography (CBCT) applications in orthodontics and evaluated the level of evidence to determine whether the use of CBCT is justified in orthodontics. TYPES OF STUDIES REVIEWED: The authors identified articles by searching th

  10. Gathering Empirical Evidence Concerning Links between Computer Aided Design (CAD) and Creativity

    Science.gov (United States)

    Musta'amal, Aede Hatib; Norman, Eddie; Hodgson, Tony

    2009-01-01

    Discussion is often reported concerning potential links between computer-aided designing and creativity, but there is a lack of systematic enquiry to gather empirical evidence concerning such links. This paper reports an indication of findings from other research studies carried out in contexts beyond general education that have sought evidence…

  11. Persistence of Learning Gains from Computer Assisted Learning: Experimental Evidence from China

    Science.gov (United States)

    Mo, D.; Zhang, L.; Wang, J.; Huang, W.; Shi, Y.; Boswell, M.; Rozelle, S.

    2015-01-01

    Computer assisted learning (CAL) programs have been shown to be effective in improving educational outcomes. However, the existing studies on CAL have almost all been conducted over a short period of time. There is very little evidence on how the impact evolves over time. In response, we conducted a clustered randomized experiment involving 2741…

  12. Discrimination of abiogenic and biogenic alkane gases

    Institute of Scientific and Technical Information of China (English)

    DAI JinXing; MI JingKui; LI ZhiSheng; HU AnPing; YANG Chun; ZHOU QingHua; SHUAI YanHua; ZHANG Ying; MA ChengHua; ZOU CaiNeng; ZHANG ShuiChang; LI Jian; NI YunYan; HU GuoYi; LUO Xia; TAO ShiZhen; ZHU GuangYou

    2008-01-01

    We have combined the analytical data of the carbon isotope distribution pattern, R/Ra and cliche values of abiogenic and biogenic (referring to the therrnogenic and bacterial or microbial) alkane gases in China with those of alkane gases from USA, Russia, Germany, Australia and other countries. Four discrimination criteria are derived from this comparative study: 1) Carbon isotopic composition is generally greater than -30‰ for abiogenic methane and less than -30‰ for biogenic methane; 2)Abiogenic alkane gases have a carbon isotopic reversal trend (Δ13c1>Δ13c2>Δ13c3>Δ13c4) with Δ13c1>-30‰ in general; 3) Gases with R/Ra>0.5 and Δ13c1- Δ13c2>0 are of abiogenic origin; 4) Gases (methane) with CH4/3He≤106 are of abiogenic origin, whereas gases with CH4/3He≥1011 are of biogenic origin.

  13. Discrimination of abiogenic and biogenic alkane gases

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    We have combined the analytical data of the carbon isotope distribution pattern, R/Ra and CH4/3He values of abiogenic and biogenic (referring to the thermogenic and bacterial or microbial) alkane gases in China with those of alkane gases from USA, Russia, Germany, Australia and other countries. Four discrimination criteria are derived from this comparative study: 1) Carbon isotopic composition is generally greater than -30‰ for abiogenic methane and less than -30‰ for biogenic methane; 2) Abiogenic alkane gases have a carbon isotopic reversal trend (δ 13C1> δ 13C2> δ 13C3> δ 13C4) with δ 13C1>-30‰ in general; 3) Gases with R/Ra >0.5 and δ 13C11 δ 13C2>0 are of abiogenic origin; 4) Gases (meth- ane) with CH4/3He≤106 are of abiogenic origin, whereas gases with CH4/3He≥1011 are of biogenic origin.

  14. Modeling of Alkane Oxidation Using Constituents and Species

    Science.gov (United States)

    Bellan, Jasette; Harstad, Kenneth G.

    2010-01-01

    It is currently not possible to perform simulations of turbulent reactive flows due in particular to complex chemistry, which may contain thousands of reactions and hundreds of species. This complex chemistry results in additional differential equations, making the numerical solution of the equation set computationally prohibitive. Reducing the chemical kinetics mathematical description is one of several important goals in turbulent reactive flow modeling. A chemical kinetics reduction model is proposed for alkane oxidation in air that is based on a parallel methodology to that used in turbulence modeling in the context of the Large Eddy Simulation. The objective of kinetic modeling is to predict the heat release and temperature evolution. This kinetic mechanism is valid over a pressure range from atmospheric to 60 bar, temperatures from 600 K to 2,500 K, and equivalence ratios from 0.125 to 8. This range encompasses diesel, HCCI, and gas-turbine engines, including cold ignition. A computationally efficient kinetic reduction has been proposed for alkanes that has been illustrated for n-heptane using the LLNL heptane mechanism. This model is consistent with turbulence modeling in that scales were first categorized into either those modeled or those computed as progress variables. Species were identified as being either light or heavy. The heavy species were decomposed into defined 13 constituents, and their total molar density was shown to evolve in a quasi-steady manner. The light species behave either in a quasi-steady or unsteady manner. The modeled scales are the total constituent molar density, Nc, and the molar density of the quasi-steady light species. The progress variables are the total constituent molar density rate evolution and the molar densities of the unsteady light species. The unsteady equations for the light species contain contributions of the type gain/loss rates from the heavy species that are modeled consistent with the developed mathematical

  15. In situ detection of anaerobic alkane metabolites in subsurface environments

    OpenAIRE

    Lisa eGieg; Akhil eAgrawal

    2013-01-01

    Alkanes comprise a substantial fraction of crude oil and refined fuels. As such, they are prevalent within deep subsurface fossil fuel deposits and in shallow subsurface environments such as aquifers that are contaminated with hydrocarbons. These environments are typically anaerobic, and host diverse microbial communities that can potentially use alkanes as substrates. Anaerobic alkane biodegradation has been reported to occur under nitrate-reducing, sulfate-reducing, and methanogenic cond...

  16. In situ detection of anaerobic alkane metabolites in subsurface environments

    OpenAIRE

    Agrawal, Akhil; Gieg, Lisa M.

    2013-01-01

    Alkanes comprise a substantial fraction of crude oil and refined fuels. As such, they are prevalent within deep subsurface fossil fuel deposits and in shallow subsurface environments such as aquifers that are contaminated with hydrocarbons. These environments are typically anaerobic, and host diverse microbial communities that can potentially use alkanes as substrates. Anaerobic alkane biodegradation has been reported to occur under nitrate-reducing, sulfate-reducing, and methanogenic conditi...

  17. Expanding the alkane oxygenase toolbox: new enzymes and applications.

    Science.gov (United States)

    van Beilen, Jan B; Funhoff, Enrico G

    2005-06-01

    As highly reduced hydrocarbons are abundant in the environment, enzymes that catalyze the terminal or subterminal oxygenation of alkanes are relatively easy to find. A number of these enzymes have been biochemically characterized in detail, because the potential of alkane hydroxylases to catalyze high added-value reactions is widely recognized. Nevertheless, the industrial application of these enzymes is restricted owing to the complex biochemistry, challenging process requirements, and the limited number of cloned and expressed enzymes. Rational and evolutionary engineering approaches have started to yield more robust and versatile enzyme systems, broadening the alkane oxygenase portfolio. In addition, metagenomic approaches provide access to many novel alkane oxygenase sequences.

  18. 40 CFR 721.3435 - Butoxy-substituted ether alkane.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Butoxy-substituted ether alkane. 721... Substances § 721.3435 Butoxy-substituted ether alkane. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as butoxy-substituted ether...

  19. Sentence-based attention mechanisms in word learning: Evidence from a computational model

    Directory of Open Access Journals (Sweden)

    Afra eAlishahi

    2012-07-01

    Full Text Available When looking for the referents of nouns, adults and young children are sensitive to cross- situational statistics (Yu & Smith, 2007; Smith & Yu, 2008. In addition, the linguistic context that a word appears in has been shown to act as a powerful attention mechanism for guiding sentence processing and word learning (Landau & Gleitman, 1985; Altmann & Kamide, 1999; Kako & Trueswell, 2000. Koehne & Crocker (2010, 2011 investigate the interaction between cross-situational evidence and guidance from the sentential context in an adult language learning scenario. Their studies reveal that these learning mechanisms interact in a complex manner: they can be used in a complementary way when context helps reduce referential uncertainty; they influence word learning about equally strongly when cross-situational and contextual evidence are in conflict; and contextual cues block aspects of cross-situational learning when both mechanisms are independently applicable. To address this complex pattern of findings, we present a probabilistic computational model of word learning which extends a previous cross-situational model (Fazly et al., 2010 with an attention mechanism based on sentential cues. Our model uses a framework that seamlessly combines the two sources of evidence in order to study their emerging pattern of interaction during the process of word learning. Simulations of the experiments of Koehne & Crocker (2010, 2011 reveal an overall patterns of results that are in line with their findings. Importantly, we demonstrate that our model does not need to explicitly assign priority to either source of evidence in order to produce these results: learning patterns emerge as a result of a probabilistic interaction between the two types of cues. Moreover, using a computational model allows us to examine the developmental trajectory of the differential roles of cross-situational and sentential cues in word learning.

  20. Further Evidence in Support of the Universal Nilpotent Grammatical Computational Paradigm of Quantum Physics

    Science.gov (United States)

    Marcer, Peter J.; Rowlands, Peter

    2010-12-01

    Further evidence is presented in favour of the computational paradigm, conceived and constructed by Rowlands and Diaz, as detailed in Rowlands' book Zero to Infinity (2007) [2], and in particular the authors' paper `The Grammatical Universe: the Laws of Thermodynamics and Quantum Entanglement' [1]. The paradigm, which has isomorphic group and algebraic quantum mechanical language interpretations, not only predicts the well-established facts of quantum physics, the periodic table, chemistry / valence and of molecular biology, whose understanding it extends; it also provides an elegant, simple solution to the unresolved quantum measurement problem. In this fundamental paradigm, all the computational constructs / predictions that emerge, follow from the simple fact, that, as in quantum mechanics, the wave function is defined only up to an arbitrary fixed phase. This fixed phase provides a simple physical understanding of the quantum vacuum in quantum field theory, where only relative phases, known to be able to encode 3+1 relativistic space-time geometries, can be measured. It is the arbitrary fixed measurement standard, against which everything that follows is to be measured, even though the standard itself cannot be, since nothing exists against which to measure it. The standard, as an arbitrary fixed reference phase, functions as the holographic basis for a self-organized universal quantum process of emergent novel fermion states of matter where, following each emergence, the arbitrary standard is re-fixed anew so as to provide a complete history / holographic record or hologram of the current fixed past, advancing an unending irreversible evolution, such as is the evidence of our senses. The fermion states, in accord with the Pauli exclusion principle, each correspond to a unique nilpotent symbol in the infinite alphabet (which specifies the grammar in this nilpotent universal computational rewrite system (NUCRS) paradigm); and the alphabet, as Hill and Rowlands

  1. Evidence for model-based computations in the human amygdala during Pavlovian conditioning.

    Science.gov (United States)

    Prévost, Charlotte; McNamee, Daniel; Jessup, Ryan K; Bossaerts, Peter; O'Doherty, John P

    2013-01-01

    Contemporary computational accounts of instrumental conditioning have emphasized a role for a model-based system in which values are computed with reference to a rich model of the structure of the world, and a model-free system in which values are updated without encoding such structure. Much less studied is the possibility of a similar distinction operating at the level of Pavlovian conditioning. In the present study, we scanned human participants while they participated in a Pavlovian conditioning task with a simple structure while measuring activity in the human amygdala using a high-resolution fMRI protocol. After fitting a model-based algorithm and a variety of model-free algorithms to the fMRI data, we found evidence for the superiority of a model-based algorithm in accounting for activity in the amygdala compared to the model-free counterparts. These findings support an important role for model-based algorithms in describing the processes underpinning Pavlovian conditioning, as well as providing evidence of a role for the human amygdala in model-based inference.

  2. Evidence for model-based computations in the human amygdala during Pavlovian conditioning.

    Directory of Open Access Journals (Sweden)

    Charlotte Prévost

    Full Text Available Contemporary computational accounts of instrumental conditioning have emphasized a role for a model-based system in which values are computed with reference to a rich model of the structure of the world, and a model-free system in which values are updated without encoding such structure. Much less studied is the possibility of a similar distinction operating at the level of Pavlovian conditioning. In the present study, we scanned human participants while they participated in a Pavlovian conditioning task with a simple structure while measuring activity in the human amygdala using a high-resolution fMRI protocol. After fitting a model-based algorithm and a variety of model-free algorithms to the fMRI data, we found evidence for the superiority of a model-based algorithm in accounting for activity in the amygdala compared to the model-free counterparts. These findings support an important role for model-based algorithms in describing the processes underpinning Pavlovian conditioning, as well as providing evidence of a role for the human amygdala in model-based inference.

  3. Resonant diffusion of normal alkanes in zeolites: Effect of the zeolite structure and alkane molecule vibrations

    CERN Document Server

    Tsekov, R

    2015-01-01

    Diffusion of normal alkanes in one-dimensional zeolites is theoretically studied on the basis of the stochastic equation formalism. The calculated diffusion coefficient accounts for the vibrations of the diffusing molecule and zeolite framework, molecule-zeolite interaction, and specific structure of the zeolite. It is shown that when the interaction potential is predominantly determined by the zeolite pore structure, the diffusion coefficient varies periodically with the number of carbon atoms of the alkane molecule, a phenomenon called resonant diffusion. A criterion for observable resonance is obtained from the balance between the interaction potentials of the molecule due to the atomic and pore structures of the zeolite. It shows that the diffusion is not resonant in zeolites without pore structure, such as ZSM-12. Moreover, even in zeolites with developed pore structure no resonant dependence of the diffusion constant can be detected if the pore structure energy barriers are not at least three times high...

  4. Long-chain alkane production by the yeast Saccharomyces cerevisiae.

    Science.gov (United States)

    Buijs, Nicolaas A; Zhou, Yongjin J; Siewers, Verena; Nielsen, Jens

    2015-06-01

    In the past decade industrial-scale production of renewable transportation biofuels has been developed as an alternative to fossil fuels, with ethanol as the most prominent biofuel and yeast as the production organism of choice. However, ethanol is a less efficient substitute fuel for heavy-duty and maritime transportation as well as aviation due to its low energy density. Therefore, new types of biofuels, such as alkanes, are being developed that can be used as drop-in fuels and can substitute gasoline, diesel, and kerosene. Here, we describe for the first time the heterologous biosynthesis of long-chain alkanes by the yeast Saccharomyces cerevisiae. We show that elimination of the hexadecenal dehydrogenase Hfd1 and expression of a redox system are essential for alkane biosynthesis in yeast. Deletion of HFD1 together with expression of an alkane biosynthesis pathway resulted in the production of the alkanes tridecane, pentadecane, and heptadecane. Our study provides a proof of principle for producing long-chain alkanes in the industrial workhorse S. cerevisiae, which was so far limited to bacteria. We anticipate that these findings will be a key factor for further yeast engineering to enable industrial production of alkane based drop-in biofuels, which can allow the biofuel industry to diversify beyond bioethanol.

  5. Expanding the product profile of a microbial alkane biosynthetic pathway.

    Science.gov (United States)

    Harger, Matthew; Zheng, Lei; Moon, Austin; Ager, Casey; An, Ju Hye; Choe, Chris; Lai, Yi-Ling; Mo, Benjamin; Zong, David; Smith, Matthew D; Egbert, Robert G; Mills, Jeremy H; Baker, David; Pultz, Ingrid Swanson; Siegel, Justin B

    2013-01-18

    Microbially produced alkanes are a new class of biofuels that closely match the chemical composition of petroleum-based fuels. Alkanes can be generated from the fatty acid biosynthetic pathway by the reduction of acyl-ACPs followed by decarbonylation of the resulting aldehydes. A current limitation of this pathway is the restricted product profile, which consists of n-alkanes of 13, 15, and 17 carbons in length. To expand the product profile, we incorporated a new part, FabH2 from Bacillus subtilis , an enzyme known to have a broader specificity profile for fatty acid initiation than the native FabH of Escherichia coli . When provided with the appropriate substrate, the addition of FabH2 resulted in an altered alkane product profile in which significant levels of n-alkanes of 14 and 16 carbons in length are produced. The production of even chain length alkanes represents initial steps toward the expansion of this recently discovered microbial alkane production pathway to synthesize complex fuels. This work was conceived and performed as part of the 2011 University of Washington international Genetically Engineered Machines (iGEM) project.

  6. The vapor-particle partitioning of n-alkanes

    Energy Technology Data Exchange (ETDEWEB)

    Doskey, P.V.

    1994-04-01

    A mixed-phase partitioning model has been proposed to predict the distribution of n-alkanes between the vapor and particle phases in the atmosphere. n-Alkanes having terrestrial plant wax and petroleum origins are assumed to be associated with atmospheric particles as microcrystalline solids and subcooled liquids, respectively. The fraction of n-alkanes on atmospheric particles having plant wax and petroleum origins is estimated with carbon preference indices. Hypothetical terrestrial plant wax and petroleum mixtures are used to estimate the mole fractions of the n-alkanes in each phase and the molecular weights of the phases. Solid and subcooled liquid phase n-alkane vapor pressures are used in the model to predict the fraction of n-alkanes associated with particles in the atmosphere. Trends in the prediction of vapor-particle partitioning using these assumptions agree well with field observations. However, the fraction of particle phase n-alkanes predicted by the model was significantly different from the field observations.

  7. Computers and student learning: bivariate and multivariate evidence on the availability and use of computers at home and at school

    OpenAIRE

    Fuchs, Thomas; Wößmann, Ludger

    2004-01-01

    We estimate the relationship between students’ educational achievement and the availability and use of computers at home and at school in the international student-level PISA database. Bivariate analyses show a positive correlation between student achievement and the availability of computers both at home and at schools. However, once we control extensively for family background and school characteristics, the relationship gets negative for home computers and insignificant for school computer...

  8. UNIQUAC interaction parameters for alkane/amine systems determined by Molecular Mechanics

    DEFF Research Database (Denmark)

    Jonsdottir, Svava Osk; Klein, R. A.; Rasmussen, Kjeld

    1996-01-01

    UNIQUAC interaction parameters have been successfully determined for three alkane/primary amine systems using a Molecular Mechanics method called the Consistent Force Field. Interaction parameters for alkane/alkane and alkane/ketone systems had been determined previously using this method...

  9. Irrelevant sensory stimuli interfere with working memory storage: evidence from a computational model of prefrontal neurons.

    Science.gov (United States)

    Bancroft, Tyler D; Hockley, William E; Servos, Philip

    2013-03-01

    The encoding of irrelevant stimuli into the memory store has previously been suggested as a mechanism of interference in working memory (e.g., Lange & Oberauer, Memory, 13, 333-339, 2005; Nairne, Memory & Cognition, 18, 251-269, 1990). Recently, Bancroft and Servos (Experimental Brain Research, 208, 529-532, 2011) used a tactile working memory task to provide experimental evidence that irrelevant stimuli were, in fact, encoded into working memory. In the present study, we replicated Bancroft and Servos's experimental findings using a biologically based computational model of prefrontal neurons, providing a neurocomputational model of overwriting in working memory. Furthermore, our modeling results show that inhibition acts to protect the contents of working memory, and they suggest a need for further experimental research into the capacity of vibrotactile working memory.

  10. Computer Assisted Audit Techniques and Audit Quality in Developing Countries: Evidence from Nigeria

    Directory of Open Access Journals (Sweden)

    Omonuk JB

    2015-12-01

    Full Text Available Most business organizations world-over have computerized their accounting systems. Extant literature finds that the use of Computer Assisted Audit Techniques (CAATs is positively related to the quality of audit reports. CAATs are widely applied to audit financial statements in developed countries. However, there is a void in literature about the audit of computerized accounts in developing countries. We draw a sample from Nigeria to investigate the following questions, “Do auditors effectively audit computerized accounts and; Is there a positive relationship between the use of CAATs and audit quality?” Using descriptive statistics, correlation analysis and logistic multiple regression, we provide evidence that: (1 CAATs are effectively used, (2 there is a positive relationship between the use of CAATS and audit quality, and (3 in a sample that excludes the big 4 International audit firms, local Nigerian firms are not effective in applying CAATs, and so, do not produce quality audit reports.

  11. Differences in NEXAFS of odd/even long chain n-alkane crystals

    Energy Technology Data Exchange (ETDEWEB)

    Swaraj, Sufal, E-mail: sufal.swaraj@synchrotron-soleil.fr [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin – BP 48, F-91192 Gif-sur-Yvette Cedex (France); Ade, Harald [North Carolina State University, Raleigh, NC (United States)

    2013-12-15

    Highlights: •Number and parity of Carbon backbone influences the NEXAFS spectra of n-alkane crystals. •Odd/even effect observed is attributed to the geometrical consequence of a zig–zag chain structure. •NEXAFS spectra are influenced by Interaction of molecular orbitals with periodic lattice. -- Abstract: We present the near edge X-ray absorption fine structure (NEXAFS) spectra of several long chain n-alkanes crystallites formed on Silicon nitride (Si{sub 3}N{sub 4}) windows. Dichroic signature was investigated with the C-C backbone aligned perpendicular to the substrate. Significant changes in the dichroic signature of spectral intensities at energies below the ionization edge (287.5 and 288.1 eV) have been observed. While the dichroic ratio corresponding to the spectral feature at 287.5 eV remains relatively unaffected by the overall length of C-C backbone, it is noticeably affected by the parity (odd or even) of the number of Carbon atoms in the n-alkane backbone. Data obtained provide evidence of the influence of interaction of molecular orbitals with periodic lattice structure.

  12. Involvement of an alkane hydroxylase system of Gordonia sp. strain SoCg in degradation of solid n-alkanes.

    Science.gov (United States)

    Lo Piccolo, Luca; De Pasquale, Claudio; Fodale, Roberta; Puglia, Anna Maria; Quatrini, Paola

    2011-02-01

    Enzymes involved in oxidation of long-chain n-alkanes are still not well known, especially those in gram-positive bacteria. This work describes the alkane degradation system of the n-alkane degrader actinobacterium Gordonia sp. strain SoCg, which is able to grow on n-alkanes from dodecane (C(12)) to hexatriacontane (C(36)) as the sole C source. SoCg harbors in its chromosome a single alk locus carrying six open reading frames (ORFs), which shows 78 to 79% identity with the alkane hydroxylase (AH)-encoding systems of other alkane-degrading actinobacteria. Quantitative reverse transcription-PCR showed that the genes encoding AlkB (alkane 1-monooxygenase), RubA3 (rubredoxin), RubA4 (rubredoxin), and RubB (rubredoxin reductase) were induced by both n-hexadecane and n-triacontane, which were chosen as representative long-chain liquid and solid n-alkane molecules, respectively. Biotransformation of n-hexadecane into the corresponding 1-hexadecanol was detected by solid-phase microextraction coupled with gas chromatography-mass spectrometry (SPME/GC-MS) analysis. The Gordonia SoCg alkB was heterologously expressed in Escherichia coli BL21 and in Streptomyces coelicolor M145, and both hosts acquired the ability to transform n-hexadecane into 1-hexadecanol, but the corresponding long-chain alcohol was never detected on n-triacontane. However, the recombinant S. coelicolor M145-AH, expressing the Gordonia alkB gene, was able to grow on n-triacontane as the sole C source. A SoCg alkB disruption mutant that is completely unable to grow on n-triacontane was obtained, demonstrating the role of an AlkB-type AH system in degradation of solid n-alkanes.

  13. Molecular dynamics study of the water/n-alkane interface

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Molecular dynamics simulations on the interface between liquid water and liquid n-alkane (including octane, nonane, decane, undecane and dodecane) have been performed with the purpose to study the interfacial properties: (Ⅰ) density profile; (Ⅱ) molecular orientation; (Ⅲ) interfacial tension and the temperature effect on the interfacial tension. Simulation results show that at the interface the structures of both water and n-alkane are different from those in the bulk. Water has an orientational preference due to the number of hydrogen bonds per molecule maximized. N-alkane has a more lateral orientation with respect to the interface in order to be in close contact with water. The calculated individual phase bulk density and interfacial tension of water/n-alkane systems are in good agreement with the corresponding experimental ones.

  14. QSPR between Physical- Chemical Properties and Molecule Parameters of Alkanes

    Institute of Scientific and Technical Information of China (English)

    XU Qing-qing; LI Liang-chao; HU Li-ya

    2005-01-01

    A set of molecule parameters, namely, N, N′, p, q,n, were used to express the structures of alkanes. A correlative model was established between certain physical-chemical properties and molecular parameters of alkanes by regression method. Eightphysical-chemical properties, such as evaporation heat (△vH20m ),density(D20 ), capacity(C20 ), surface tension(σ20 ), boiling point ( Tb ), critical temperature ( Tc ), critical pressure (Pc) and critical volume(Vc), of fifty-six C3-C16 alkanes were calculated directly from the model in this paper. The calculated values are in good accordance with the literature ones reported for alkanes, and the correlation coefficients (R) equal or exceed 0.99. The research results indicate that the principle of the method is simple and clear, the method is practical, the correlativity is excellent, and the predicted data are credible.

  15. Alkane oxidation by Pseudomonas oleovorans: genes and proteins

    OpenAIRE

    van Beilen, Jan Berthold

    1994-01-01

    This thesis deals with the molecular genetics and biochemistry of oxidation of medium chainlength alkanes by P. oleovorans, as part of a program to develop biotechnological processes, based on oxygenases.

  16. Alkane oxidation by Pseudomonas oleovorans : genes and proteins

    NARCIS (Netherlands)

    van Beilen, Jan Berthold

    1994-01-01

    This thesis deals with the molecular genetics and biochemistry of oxidation of medium chainlength alkanes by P. oleovorans, as part of a program to develop biotechnological processes, based on oxygenases.

  17. A sampling-based computational strategy for the representation of epistemic uncertainty in model predictions with evidence theory.

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, J. D. (Prostat, Mesa, AZ); Oberkampf, William Louis; Helton, Jon Craig (Arizona State University, Tempe, AZ); Storlie, Curtis B. (North Carolina State University, Raleigh, NC)

    2006-10-01

    Evidence theory provides an alternative to probability theory for the representation of epistemic uncertainty in model predictions that derives from epistemic uncertainty in model inputs, where the descriptor epistemic is used to indicate uncertainty that derives from a lack of knowledge with respect to the appropriate values to use for various inputs to the model. The potential benefit, and hence appeal, of evidence theory is that it allows a less restrictive specification of uncertainty than is possible within the axiomatic structure on which probability theory is based. Unfortunately, the propagation of an evidence theory representation for uncertainty through a model is more computationally demanding than the propagation of a probabilistic representation for uncertainty, with this difficulty constituting a serious obstacle to the use of evidence theory in the representation of uncertainty in predictions obtained from computationally intensive models. This presentation describes and illustrates a sampling-based computational strategy for the representation of epistemic uncertainty in model predictions with evidence theory. Preliminary trials indicate that the presented strategy can be used to propagate uncertainty representations based on evidence theory in analysis situations where naive sampling-based (i.e., unsophisticated Monte Carlo) procedures are impracticable due to computational cost.

  18. Structure and phase transitions of monolayers of intermediate-length n-alkanes on graphite studied by neutron diffraction and molecular dynamics simulation

    DEFF Research Database (Denmark)

    Diama, A.; Matthies, B.; Herwig, K. W.;

    2009-01-01

    We present evidence from neutron diffraction measurements and molecular dynamics (MD) simulations of three different monolayer phases of the intermediate-length alkanes tetracosane (n-C24H50 denoted as C24) and dotriacontane (n-C32H66 denoted as C32) adsorbed on a graphite basal-plane surface. Our...... show evidence of broadening of the lamella boundaries as a result of molecules diffusing parallel to their long axis. At still higher temperatures, they indicate that the introduction of gauche defects into the alkane chains drives a melting transition to a monolayer fluid phase as reported previously...

  19. Contribution of cyanobacterial alkane production to the ocean hydrocarbon cycle.

    Science.gov (United States)

    Lea-Smith, David J; Biller, Steven J; Davey, Matthew P; Cotton, Charles A R; Perez Sepulveda, Blanca M; Turchyn, Alexandra V; Scanlan, David J; Smith, Alison G; Chisholm, Sallie W; Howe, Christopher J

    2015-11-03

    Hydrocarbons are ubiquitous in the ocean, where alkanes such as pentadecane and heptadecane can be found even in waters minimally polluted with crude oil. Populations of hydrocarbon-degrading bacteria, which are responsible for the turnover of these compounds, are also found throughout marine systems, including in unpolluted waters. These observations suggest the existence of an unknown and widespread source of hydrocarbons in the oceans. Here, we report that strains of the two most abundant marine cyanobacteria, Prochlorococcus and Synechococcus, produce and accumulate hydrocarbons, predominantly C15 and C17 alkanes, between 0.022 and 0.368% of dry cell weight. Based on global population sizes and turnover rates, we estimate that these species have the capacity to produce 2-540 pg alkanes per mL per day, which translates into a global ocean yield of ∼ 308-771 million tons of hydrocarbons annually. We also demonstrate that both obligate and facultative marine hydrocarbon-degrading bacteria can consume cyanobacterial alkanes, which likely prevents these hydrocarbons from accumulating in the environment. Our findings implicate cyanobacteria and hydrocarbon degraders as key players in a notable internal hydrocarbon cycle within the upper ocean, where alkanes are continually produced and subsequently consumed within days. Furthermore we show that cyanobacterial alkane production is likely sufficient to sustain populations of hydrocarbon-degrading bacteria, whose abundances can rapidly expand upon localized release of crude oil from natural seepage and human activities.

  20. Positronium in solid phases of n-alkane binary mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Zgardzińska, B.; Goworek, T.

    2015-09-08

    Highlights: • Rotator phase in even alkanes C{sub n}H{sub 2n+2} with n ⩽ 20 appears in mixed samples only. • Interlamellar gap width is the same for shorter chain alkane concentration x and 1 − x. • Excess electron trapping diminishes with broadening of alkane chain distribution Δn. - Abstract: Binary mixtures of even-numbered normal alkanes C{sub n}H{sub 2n+2} and C{sub n+2}H{sub 2n+6} with n ⩽ 18 were investigated by positron annihilation spectroscopy. Formation of the rotator phase was observed in mixed structures, while no such a phase in neat alkanes in this range of n was found. Phase diagrams for n = 18 and n = 16 are very similar to the diagrams for binary mixtures of odd-numbered alkanes. The effect of positronium formation with trapped excess electrons weakens with decreasing n, at low n values the time constant of Ps rise contains the component much shorter than 1 h.

  1. Hydrogen-hydrogen bonds in highly branched alkanes and in alkane complexes: A DFT, ab initio, QTAIM, and ELF study.

    Science.gov (United States)

    Monteiro, Norberto K V; Firme, Caio L

    2014-03-06

    The hydrogen-hydrogen (H-H) bond or hydrogen-hydrogen bonding is formed by the interaction between a pair of identical or similar hydrogen atoms that are close to electrical neutrality and it yields a stabilizing contribution to the overall molecular energy. This work provides new, important information regarding hydrogen-hydrogen bonds. We report that stability of alkane complexes and boiling point of alkanes are directly related to H-H bond, which means that intermolecular interactions between alkane chains are directional H-H bond, not nondirectional induced dipole-induced dipole. Moreover, we show the existence of intramolecular H-H bonds in highly branched alkanes playing a secondary role in their increased stabilities in comparison with linear or less branched isomers. These results were accomplished by different approaches: density functional theory (DFT), ab initio, quantum theory of atoms in molecules (QTAIM), and electron localization function (ELF).

  2. Ubiquitous Computing Identity Authentication Mechanism Based on D-S Evidence Theory and Extended SPKI/SDSI

    Institute of Scientific and Technical Information of China (English)

    SUN Dao-qing; CAO Qi-ying

    2008-01-01

    Ubiquitous computing systems typically have lots of security problems in the area of identity authentication by means of classical PKI methods. The limited computing resources, the disconnection network, the classification requirements of identity authentication, the requirement of trust transfer and cross identity authentication, the bi-directional identity authentication, the security delegation and the simple privacy protection etc are all these unsolved problems. In this paper, a new novel ubiquitous computing identity authentication mechanism, named UCIAMdess, is presented. It is based on D-S Evidence Theory and extended SPKI/SDSI. D-S Evidence Theory is used in UCIAMdess to compute the trust value from the ubiquitous computing environment to the principal or between the different ubiquitous computing environments. SPKI-based authorization is expanded by adding the trust certificate in UCIAMdess to solve above problems in the ubiquitous computing environments. The identity authentication mechanism and the algorithm of certificate reduction are given in the paper to solve the multi-levels trnst-correlative identity authentication problems. The performance analyses show that UCIAMdess is a suitable security mechanism in solving the complex ubiquitous computing problems.

  3. (19)F Oximetry with semifluorinated alkanes.

    Science.gov (United States)

    Kegel, Stefan; Chacon-Caldera, Jorge; Tsagogiorgas, Charalambos; Theisinger, Bastian; Glatting, Gerhard; Schad, Lothar R

    2016-12-01

    This work examines the variation of longitudinal relaxation rate R1(= 1/T1) of the (19)F-CF3-resonance of semifluorinated alkanes (SFAs) with oxygen tension (pO2), temperature (T) and pH in vitro. Contrary to their related perfluorocarbons (PFCs), SFA are amphiphilic and facilitate stable emulsions, a prerequisite for clinical use. A linear relationship between R1 and pO2 was confirmed for the observed SFAs at different temperatures. Using a standard saturation recovery sequence, T1 has been successfully measured using fluorine (19)F-MRI with a self-constructed birdcage resonator at 9.4 T. A calibration curve to calculate pO2 depending on T and R1 was found for each SFA used. In contrast to the commonly used PFC, SFAs are less sensitive to changes in pO2, but more sensitive to changes in temperature. The influence of pH to R1 was found to be negligible.

  4. Computed tomography evidence of dental restoration as aetiological factor for maxillary sinusitis.

    Science.gov (United States)

    Connor, S E; Chavda, S V; Pahor, A L

    2000-07-01

    Maxillary sinusitis due to dental causes is usually secondary to periodontal disease or periapical infection and is commonly associated with mucosal thickening of the floor of the maxillary antrum. Computed tomography (CT) is currently the modality of choice for evaluating the extent of disease and any predisposing factors in patients with symptoms of chronic maxillary sinusitis, but it is unable to diagnose dental disease reliably. The presence of restorative dentistry is, however, easily seen at CT and is associated with both periapical and periodontal disease. We aimed to determine whether its presence at CT may predispose to maxillary sinusitis, and in particular to focal mucosal thickening of the sinus floor characteristic of dental origin. Three hundred and thirty maxillary sinus CT images in 165 patients were reviewed for the presence of restorative dentistry in the adjacent teeth, focal maxillary sinus floor mucosal thickening, any maxillary sinus disease (including complete opacification, air fluid levels, diffuse mucosal thickening, focal mucosal thickening) and evidence of a rhinogenic aetiology (osteomeatal complex pathology, mucosal thickening in other sinuses). One hundred and ninety two sinuses adjacent to restorative dentistry and 178 sinuses not adjacent to restorative dentistry were analysed. Focal floor thickening both with, and without, evidence of a rhinogenic aetiology, was significantly more common adjacent to restorative dentistry. Maxillary sinus disease overall was no more common adjacent to restorative dentistry. This work demonstrated that the presence of restorative dentistry predisposes to focal mucosal thickening in the floor of the maxillary sinus and its presence should prompt clinical and radiographical assessment to exclude dental disease as a source of chronic maxillary sinusitis.

  5. A Comparison of the Monolayer Dynamics of the Branched Alkane Squalane and the Normal Alkane Tetracosane Adsorbed on Graphite

    Science.gov (United States)

    Enevoldsen, A. D.; Hansen, F. Y.; Diama, A.; Taub, H.

    2004-03-01

    Squalane is a branched alkane (C_30H_62) with 24 carbon atoms in its backbone, like the normal alkane tetracosane ( n-C_24H_50), and six symmetrically placed methyl side groups. In general, branched alkanes such as squalane are better lubricants than n-alkanes. We have studied the dynamics of the squalane and tetracosane monolayers by quasielastic neutron scattering and molecular dynamics (MD) simulations on two different time scales. Both experiments and simulations showed that diffusion at 260 K is about 2.5 times faster in the squalane than in the tetracosane system. It is somewhat surprising that the diffusion in a system with a branched alkane is faster than with a normal alkane. A possible explanation is that the squalane molecule does not bind as strongly to the surface as tetracosane, because the MD simulations have shown that the adsorbed molecules have a distorted backbone. This may also explain why the slow intramolecular motions associated with conformational changes are seen at lower temperatures in the squalane than the tetracosane monolayer where they are only observed near melting.

  6. Quantification of chemotaxis-related alkane accumulation in Acinetobacter baylyi using Raman microspectroscopy.

    Science.gov (United States)

    Li, Hanbing; L Martin, Francis Luke; Zhang, Dayi

    2017-03-03

    Alkanes are one of the most widespread contaminants in the natural environment, primarily as a consequence of biological synthesis and oil spills. Many indigenous microbes metabolize alkanes, and the chemotaxis and accumulation in some strains has been identified. For the first time, we apply Raman microspectroscopy to identify such chemotaxis-related affinity, and quantify the alkane concentrations via spectral alterations. Raman spectral alterations were only found for the alkane chemo-attractant bacteria Acinetobacter baylyi ADP1, not for Pseudomonas fluorescence, which exhibits limited chemotaxis towards alkane. The significant alterations were attributed to the strong chemotactic ability of A. baylyi enhancing the affinity and accumulation of alkane molecules on cell membranes or cellular internalization. Spectral fingerprints of A. baylyi significantly altered after 1-h exposure to pure alkanes (dodecane or tetradecane) and alkane mixtures (mineral oil or crude oil), but not monocyclic aromatic hydrocarbons (MAHs) or polycyclic aromatic hydrocarbons (PAHs). A semi-log linear regression relationship between Raman spectral alterations and alkane concentrations showed its feasibility in quantifying alkane concentration in environmental samples. Pure alkanes or alkane mixtures exhibited different limits of detection and regression slopes, indicating that the chemotaxis-related alkane accumulation in A. baylyi is dependent on the carbon chain length. This work provides a novel biospectroscopy approach to characterize the chemotaxis-related alkane bioaccumulation, and has immense potential for fast and high-throughput screening bacterial chemotaxis.

  7. TrueAllele casework on Virginia DNA mixture evidence: computer and manual interpretation in 72 reported criminal cases.

    Directory of Open Access Journals (Sweden)

    Mark W Perlin

    Full Text Available Mixtures are a commonly encountered form of biological evidence that contain DNA from two or more contributors. Laboratory analysis of mixtures produces data signals that usually cannot be separated into distinct contributor genotypes. Computer modeling can resolve the genotypes up to probability, reflecting the uncertainty inherent in the data. Human analysts address the problem by simplifying the quantitative data in a threshold process that discards considerable identification information. Elevated stochastic threshold levels potentially discard more information. This study examines three different mixture interpretation methods. In 72 criminal cases, 111 genotype comparisons were made between 92 mixture items and relevant reference samples. TrueAllele computer modeling was done on all the evidence samples, and documented in DNA match reports that were provided as evidence for each case. Threshold-based Combined Probability of Inclusion (CPI and stochastically modified CPI (mCPI analyses were performed as well. TrueAllele's identification information in 101 positive matches was used to assess the reliability of its modeling approach. Comparison was made with 81 CPI and 53 mCPI DNA match statistics that were manually derived from the same data. There were statistically significant differences between the DNA interpretation methods. TrueAllele gave an average match statistic of 113 billion, CPI averaged 6.68 million, and mCPI averaged 140. The computer was highly specific, with a false positive rate under 0.005%. The modeling approach was precise, having a factor of two within-group standard deviation. TrueAllele accuracy was indicated by having uniformly distributed match statistics over the data set. The computer could make genotype comparisons that were impossible or impractical using manual methods. TrueAllele computer interpretation of DNA mixture evidence is sensitive, specific, precise, accurate and more informative than manual

  8. TrueAllele casework on Virginia DNA mixture evidence: computer and manual interpretation in 72 reported criminal cases.

    Science.gov (United States)

    Perlin, Mark W; Dormer, Kiersten; Hornyak, Jennifer; Schiermeier-Wood, Lisa; Greenspoon, Susan

    2014-01-01

    Mixtures are a commonly encountered form of biological evidence that contain DNA from two or more contributors. Laboratory analysis of mixtures produces data signals that usually cannot be separated into distinct contributor genotypes. Computer modeling can resolve the genotypes up to probability, reflecting the uncertainty inherent in the data. Human analysts address the problem by simplifying the quantitative data in a threshold process that discards considerable identification information. Elevated stochastic threshold levels potentially discard more information. This study examines three different mixture interpretation methods. In 72 criminal cases, 111 genotype comparisons were made between 92 mixture items and relevant reference samples. TrueAllele computer modeling was done on all the evidence samples, and documented in DNA match reports that were provided as evidence for each case. Threshold-based Combined Probability of Inclusion (CPI) and stochastically modified CPI (mCPI) analyses were performed as well. TrueAllele's identification information in 101 positive matches was used to assess the reliability of its modeling approach. Comparison was made with 81 CPI and 53 mCPI DNA match statistics that were manually derived from the same data. There were statistically significant differences between the DNA interpretation methods. TrueAllele gave an average match statistic of 113 billion, CPI averaged 6.68 million, and mCPI averaged 140. The computer was highly specific, with a false positive rate under 0.005%. The modeling approach was precise, having a factor of two within-group standard deviation. TrueAllele accuracy was indicated by having uniformly distributed match statistics over the data set. The computer could make genotype comparisons that were impossible or impractical using manual methods. TrueAllele computer interpretation of DNA mixture evidence is sensitive, specific, precise, accurate and more informative than manual interpretation alternatives

  9. Analysis electronic evidence in the computer crime evidence research%探析电子证据在计算机犯罪中的取证研究

    Institute of Scientific and Technical Information of China (English)

    徐腾

    2011-01-01

    With the growing phenomenon of cyber attacks and attack techniques of the ever-changing, computer forensics is to be able to accept the court, sufficiently reliable and persuasive, there are computers and related peripherals in the electronic evidence in the identification, collection, conservation, analysis, archiving, and presented the court process. Therefore, the Computer Forensics Electronic Evidence of it is very important technology initiative for the electronic evidence of illegal behavior by hackers and complete reconstruction, can accurately and effectively combat illegal hacking.%随着网络攻击现象的增长和攻击技术手段的千变万化,计算机取证就是对能够为法庭接受的,足够可靠和有说服性的,存在于计算机和相关外设中的电子证据的确定、收集、保护、分析、归档以及法庭出示的过程.因此电子证据的计算机取证技术研究就显得十分重要,通过电子取证技术主动获取非法黑客的攻击行为并完整重建,可以准确有效地打击非法黑客.

  10. Biodegradation of Variable-Chain-Length Alkanes at Low Temperatures by a Psychrotrophic Rhodococcus sp.

    OpenAIRE

    Whyte, Lyle G; Hawari, Jalal; Zhou, Edward; Bourbonnière, Luc; Inniss, William E.; Charles W Greer

    1998-01-01

    The psychrotroph Rhodococcus sp. strain Q15 was examined for its ability to degrade individual n-alkanes and diesel fuel at low temperatures, and its alkane catabolic pathway was investigated by biochemical and genetic techniques. At 0 and 5°C, Q15 mineralized the short-chain alkanes dodecane and hexadecane to a greater extent than that observed for the long-chain alkanes octacosane and dotriacontane. Q15 utilized a broad range of aliphatics (C10 to C21 alkanes, branched alkanes, and a substi...

  11. Variation in n-Alkane Distributions of Modern Plants: Questioning Applications of n-Alkanes in Chemotaxonomy and Paleoecology

    Science.gov (United States)

    Bush, R. T.; McInerney, F. A.

    2010-12-01

    Long chain n-alkanes (n-C21 to n-C37) are synthesized as part of the epicuticular leaf wax of terrestrial plants and are among the most recognizable and widely used plant biomarkers. n-Alkane distributions have been utilized in previous studies on modern plant chemotaxonomy, testing whether taxa can be identified based on characteristic n-alkane profiles. Dominant n-alkanes (e.g. n-C27 or n-C31) have also been ascribed to major plant groups (e.g. trees or grasses respectively) and have been used in paleoecology studies to reconstruct fluctuations in plant functional types. However, many of these studies have been based on relatively few modern plant data; with the wealth of modern n-alkane studies, a more comprehensive analysis of n-alkanes in modern plants is now possible and can inform the usefulness of n-alkane distributions as paleoecological indicators. The work presented here is a combination of measurements made using plant leaves collected from the Chicago Botanic Garden and a compilation of published literature data from six continents. We categorized plants by type: angiosperms, gymnosperms, woody plants, forbs, grasses, ferns and pteridophytes, and mosses. We then quantified n-alkane distribution parameters such as carbon preference index (CPI), average chain length (ACL), and dispersion (a measure of the spread of the profile over multiple chain lengths) and used these to compare plant groups. Among all plants, one of the emergent correlations is a decrease in dispersion with increasing CPI. Within and among plant groups, n-alkane distributions show a very large range of variation, and the results show little or no correspondence between broad plant groups and a single dominant n-alkane or a ratio of n-alkanes. These findings are true both when data from six continents are combined and when plants from a given region are compared (North America). We also compared the n-alkane distributions of woody angiosperms, woody gymnosperms, and grasses with one

  12. Use of the N-alkanes to Estimate Intake, Apparent Digestibility and Diet Composition in Sheep Grazing on Stipa brevilfora Desert Steppe

    Institute of Scientific and Technical Information of China (English)

    HU Hong-lian; LIU Yong-zhi; LI Ya-kui; LU De-xun; GAO Min

    2014-01-01

    The application of n-alkane as markers to estimate herbage intake, apparent digestibility and species composition of diet consumed by grazing sheep was studied. Six local Mongolian sheep were used to determine dry matter (DM) intake, apparent DM digestibility and species composition of diet during summer, autumn and winter. Animals were orally dosed twice daily with n-alkane gelatin capsules containing 60 mg C32-alkane as an external marker. Diet composition was estimated by comparing the odd-chain n-alkanes pattern profile (C27-C31) of the consumed plant species with the n-alkanes fecal concentrations of grazing animals, using a non-negative least squares algorithm called EATWHAT software package. The alkane pair C32:C33 and C33 alkane were used to estimate DM intake and diet apparent DM digestibility, respectively. The results showed that daily dry matter intake of the sheep were 1.77, 1.61 and 1.18 kg d-1 in summer, autumn and winter, respectively. Apparent DM digestibility, crude protein (CP), metabolizable energy (ME) and neutral detergent ifber (NDF) intake of diet consumed by sheep decreased signiifcantly (P<0.01) from summer to winter, with no evident changes in ADF and ADL intake. Diet composition indicated Artemisia frigida Willd was the most dominant diet component, contributed 79.68, 68.12 and 86.26% of sheep’s diets in summer, autumn and winter, respectively. Cleistogenes songorica Ohwi and Convolvulus ammannii Desr were the important components of the diet. Although Stipa brevilfora Griseb is one of the main plant species in the study area, the sheep rarely choosed it. The study indicated that CP and ME in diet consumed by sheep were deifcient in winter. Therefore, appropriate supplementation strategies should be indispensable during this period.

  13. Oxidation of methyl tert-butyl ether by alkane hydroxylase in dicyclopropylketone-induced and n-octane-grown Pseudomonas putida GPo1.

    Science.gov (United States)

    Smith, Christy A; Hyman, Michael R

    2004-08-01

    The alkane hydroxylase enzyme system in Pseudomonas putida GPo1 has previously been reported to be unreactive toward the gasoline oxygenate methyl tert-butyl ether (MTBE). We have reexamined this finding by using cells of strain GPo1 grown in rich medium containing dicyclopropylketone (DCPK), a potent gratuitous inducer of alkane hydroxylase activity. Cells grown with DCPK oxidized MTBE and generated stoichiometric quantities of tert-butyl alcohol (TBA). Cells grown in the presence of DCPK also oxidized tert-amyl methyl ether but did not appear to oxidize either TBA, ethyl tert-butyl ether, or tert-amyl alcohol. Evidence linking MTBE oxidation to alkane hydroxylase activity was obtained through several approaches. First, no TBA production from MTBE was observed with cells of strain GPo1 grown on rich medium without DCPK. Second, no TBA production from MTBE was observed in DCPK-treated cells of P. putida GPo12, a strain that lacks the alkane-hydroxylase-encoding OCT plasmid. Third, all n-alkanes that support the growth of strain GPo1 inhibited MTBE oxidation by DCPK-treated cells. Fourth, two non-growth-supporting n-alkanes (propane and n-butane) inhibited MTBE oxidation in a saturable, concentration-dependent process. Fifth, 1,7-octadiyne, a putative mechanism-based inactivator of alkane hydroxylase, fully inhibited TBA production from MTBE. Sixth, MTBE-oxidizing activity was also observed in n-octane-grown cells. Kinetic studies with strain GPo1 grown on n-octane or rich medium with DCPK suggest that MTBE-oxidizing activity may have previously gone undetected in n-octane-grown cells because of the unusually high K(s) value (20 to 40 mM) for MTBE.

  14. Metabolism of Hydrocarbons in n-Alkane-Utilizing Anaerobic Bacteria.

    Science.gov (United States)

    Wilkes, Heinz; Buckel, Wolfgang; Golding, Bernard T; Rabus, Ralf

    2016-01-01

    The glycyl radical enzyme-catalyzed addition of n-alkanes to fumarate creates a C-C-bond between two concomitantly formed stereogenic carbon centers. The configurations of the two diastereoisomers of the product resulting from n-hexane activation by the n-alkane-utilizing denitrifying bacterium strain HxN1, i.e. (1-methylpentyl)succinate, were assigned as (2S,1'R) and (2R,1'R). Experiments with stereospecifically deuterated n-(2,5-2H2)hexanes revealed that exclusively the pro-S hydrogen atom is abstracted from C2 of the n-alkane by the enzyme and later transferred back to C3 of the alkylsuccinate formed. These results indicate that the alkylsuccinate-forming reaction proceeds with an inversion of configuration at the carbon atom (C2) of the n-alkane forming the new C-C-bond, and thus stereochemically resembles a SN2-type reaction. Therefore, the reaction may occur in a concerted manner, which may avoid the highly energetic hex-2-yl radical as an intermediate. The reaction is associated with a significant primary kinetic isotope effect (kH/kD ≥3) for hydrogen, indicating that the homolytic C-H-bond cleavage is involved in the first irreversible step of the reaction mechanism. The (1-methylalkyl)succinate synthases of n-alkane-utilizing anaerobic bacteria apparently have very broad substrate ranges enabling them to activate not only aliphatic but also alkyl-aromatic hydrocarbons. Thus, two denitrifiers and one sulfate reducer were shown to convert the nongrowth substrate toluene to benzylsuccinate and further to the dead-end product benzoyl-CoA. For this purpose, however, the modified β-oxidation pathway known from alkylbenzene-utilizing bacteria was not employed, but rather the pathway used for n-alkane degradation involving CoA ligation, carbon skeleton rearrangement and decarboxylation. Furthermore, various n-alkane- and alkylbenzene-utilizing denitrifiers and sulfate reducers were found to be capable of forming benzyl alcohols from diverse alkylbenzenes

  15. Transition-state enthalpy and entropy effects on reactivity and selectivity in hydrogenolysis of n-alkanes.

    Science.gov (United States)

    Flaherty, David W; Iglesia, Enrique

    2013-12-11

    Statistical mechanics and transition state (TS) theory describe rates and selectivities of C-C bond cleavage in C2-C10 n-alkanes on metal catalysts and provide a general description for the hydrogenolysis of hydrocarbons. Mechanistic interpretation shows the dominant role of entropy, over enthalpy, in determining the location and rate of C-C bond cleavage. Ir, Rh, and Pt clusters cleave C-C bonds at rates proportional to coverages of intermediates derived by removing 3-4 H-atoms from n-alkanes. Rate constants for C-C cleavage reflect large activation enthalpies (ΔH(‡), 217-257 kJ mol(-1)) that are independent of chain length and C-C bond location in C4+ n-alkanes. C-C bonds cleave because of large, positive activation entropies (ΔS(‡), 164-259 J mol(-1) K(-1)) provided by H2 that forms with TS. Kinetic and independent spectroscopic evidence for the composition and structure of these TS give accurate estimates of ΔS(‡) for cleavage at each C-C bond. Large differences between rate constants for ethane and n-decane (~10(8)) reflect an increase in the entropy of gaseous alkanes retained at the TS. The location of C-C bond cleavage depends solely on the rotational entropies of alkyl chains attached to the cleaved C-C bond, which depend on their chain length. Such entropy considerations account for the ubiquitous, but previously unexplained, preference for cleaving nonterminal C-C bonds in n-alkanes. This mechanistic analysis and thermodynamic treatment illustrates the continued utility of such approaches even for hydrogenolysis reactions, with complexity seemingly beyond the reach of classical treatments, and applies to catalytic clusters beyond those reported here (0.6-2.7 nm; Ir, Rh, Pt).

  16. 40 CFR 721.10145 - Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino...

    Science.gov (United States)

    2010-07-01

    ... alcohol, halogenated alkane, substituted epoxide, and amino compound (generic). 721.10145 Section 721... Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino compound... identified generically as modified reaction products of alkyl alcohol, halogenated alkane,...

  17. Alkane inducible proteins in Geobacillus thermoleovorans B23

    Directory of Open Access Journals (Sweden)

    Kato Tomohisa

    2009-03-01

    Full Text Available Abstract Background Initial step of β-oxidation is catalyzed by acyl-CoA dehydrogenase in prokaryotes and mitochondria, while acyl-CoA oxidase primarily functions in the peroxisomes of eukaryotes. Oxidase reaction accompanies emission of toxic by-product reactive oxygen molecules including superoxide anion, and superoxide dismutase and catalase activities are essential to detoxify them in the peroxisomes. Although there is an argument about whether primitive life was born and evolved under high temperature conditions, thermophilic archaea apparently share living systems with both bacteria and eukaryotes. We hypothesized that alkane degradation pathways in thermophilic microorganisms could be premature and useful to understand their evolution. Results An extremely thermophilic and alkane degrading Geobacillus thermoleovorans B23 was previously isolated from a deep subsurface oil reservoir in Japan. In the present study, we identified novel membrane proteins (P16, P21 and superoxide dismutase (P24 whose production levels were significantly increased upon alkane degradation. Unlike other bacteria acyl-CoA oxidase and catalase activities were also increased in strain B23 by addition of alkane. Conclusion We first suggested that peroxisomal β-oxidation system exists in bacteria. This eukaryotic-type alkane degradation pathway in thermophilic bacterial cells might be a vestige of primitive living cell systems that had evolved into eukaryotes.

  18. Determining and quantifying specific sources of light alkane

    Science.gov (United States)

    Bill, M.; Conrad, M. E.

    2015-12-01

    Determining and quantifying specific sources of emission of methane (an important greenhouse gas) and light alkanes from abandoned gas and oil wells, hydraulic fracturing or associated with CO2 sequestration are a challenge in determining their contribution to the atmospheric greenhouse gas budget or to identify source of groundwater contamination. Here, we review organic biogeochemistry proprieties and isotopic fingerprinting of C1-C5 alkanes to address this problem. For instance, the concentration ratios of CH4 to C2-C5 alkanes can be used to distinguish between thermogenic and microbial generated CH4. Together C and H isotopes of CH4 are used to differentiate bacterial generated sources and thermogenic CH4 and may also identify processes such as alteration and source mixing. Carbon isotope ratios pattern of C1-C5 alkanes highlight sources and oxidation processes in the gas reservoirs. Stable carbon isotope measurements are a viable tool for monitoring the degradation progress of methane and light hydrocarbons. The carbon isotope ratios of the reactants and products are independent of the concentration and only depend on the relative progress of the particular reaction. Oxidation/degradation of light alkanes are typically associated with increasing ð13C values. Isotopic mass balances offer the possibility to independently determine the fractions coming from microbial versus thermogenic and would also permit differentiation of the isotope fractionations associated with degradation. Unlike conventional concentration measurements, this approach is constrained by the different isotopic signatures of various sources and sinks.

  19. A novel transmembrane topology of presenilin based on reconciling experimental and computational evidence.

    Science.gov (United States)

    Henricson, Anna; Käll, Lukas; Sonnhammer, Erik L L

    2005-06-01

    The transmembrane topology of presenilins is still the subject of debate despite many experimental topology studies using antibodies or gene fusions. The results from these studies are partly contradictory and consequently several topology models have been proposed. Studies of presenilin-interacting proteins have produced further contradiction, primarily regarding the location of the C-terminus. It is thus impossible to produce a topology model that agrees with all published data on presenilin. We have analyzed the presenilin topology through computational sequence analysis of the presenilin family and the homologous presenilin-like protein family. Members of these families are intramembrane-cleaving aspartyl proteases. Although the overall sequence homology between the two families is low, they share the conserved putative active site residues and the conserved 'PAL' motif. Therefore, the topology model for the presenilin-like proteins can give some clues about the presenilin topology. Here we propose a novel nine-transmembrane topology with the C-terminus in the extracytosolic space. This model has strong support from published data on gamma-secretase function and presenilin topology. Contrary to most presenilin topology models, we show that hydrophobic region X is probably a transmembrane segment. Consequently, the C-terminus would be located in the extracytosolic space. However, the last C-terminal amino acids are relatively hydrophobic and in conjunction with existing experimental data we cannot exclude the possibility that the extreme C-terminus could be buried within the gamma-secretase complex. This might explain the difficulties in obtaining consistent experimental evidence regarding the location of the C-terminal region of presenilin.

  20. Deciding not to decide: computational and neural evidence for hidden behavior in sequential choice.

    Science.gov (United States)

    Gluth, Sebastian; Rieskamp, Jörg; Büchel, Christian

    2013-10-01

    Understanding the cognitive and neural processes that underlie human decision making requires the successful prediction of how, but also of when, people choose. Sequential sampling models (SSMs) have greatly advanced the decision sciences by assuming decisions to emerge from a bounded evidence accumulation process so that response times (RTs) become predictable. Here, we demonstrate a difficulty of SSMs that occurs when people are not forced to respond at once but are allowed to sample information sequentially: The decision maker might decide to delay the choice and terminate the accumulation process temporarily, a scenario not accounted for by the standard SSM approach. We developed several SSMs for predicting RTs from two independent samples of an electroencephalography (EEG) and a functional magnetic resonance imaging (fMRI) study. In these studies, participants bought or rejected fictitious stocks based on sequentially presented cues and were free to respond at any time. Standard SSM implementations did not describe RT distributions adequately. However, by adding a mechanism for postponing decisions to the model we obtained an accurate fit to the data. Time-frequency analysis of EEG data revealed alternating states of de- and increasing oscillatory power in beta-band frequencies (14-30 Hz), indicating that responses were repeatedly prepared and inhibited and thus lending further support for the existence of a decision not to decide. Finally, the extended model accounted for the results of an adapted version of our paradigm in which participants had to press a button for sampling more information. Our results show how computational modeling of decisions and RTs support a deeper understanding of the hidden dynamics in cognition.

  1. Deciding not to decide: computational and neural evidence for hidden behavior in sequential choice.

    Directory of Open Access Journals (Sweden)

    Sebastian Gluth

    2013-10-01

    Full Text Available Understanding the cognitive and neural processes that underlie human decision making requires the successful prediction of how, but also of when, people choose. Sequential sampling models (SSMs have greatly advanced the decision sciences by assuming decisions to emerge from a bounded evidence accumulation process so that response times (RTs become predictable. Here, we demonstrate a difficulty of SSMs that occurs when people are not forced to respond at once but are allowed to sample information sequentially: The decision maker might decide to delay the choice and terminate the accumulation process temporarily, a scenario not accounted for by the standard SSM approach. We developed several SSMs for predicting RTs from two independent samples of an electroencephalography (EEG and a functional magnetic resonance imaging (fMRI study. In these studies, participants bought or rejected fictitious stocks based on sequentially presented cues and were free to respond at any time. Standard SSM implementations did not describe RT distributions adequately. However, by adding a mechanism for postponing decisions to the model we obtained an accurate fit to the data. Time-frequency analysis of EEG data revealed alternating states of de- and increasing oscillatory power in beta-band frequencies (14-30 Hz, indicating that responses were repeatedly prepared and inhibited and thus lending further support for the existence of a decision not to decide. Finally, the extended model accounted for the results of an adapted version of our paradigm in which participants had to press a button for sampling more information. Our results show how computational modeling of decisions and RTs support a deeper understanding of the hidden dynamics in cognition.

  2. An integrative computational analysis provides evidence for FBN1-associated network deregulation in trisomy 21

    Directory of Open Access Journals (Sweden)

    Mireia Vilardell

    2013-06-01

    Although approximately 50% of Down Syndrome (DS patients have heart abnormalities, they exhibit an overprotection against cardiac abnormalities related with the connective tissue, for example a lower risk of coronary artery disease. A recent study reported a case of a person affected by DS who carried mutations in FBN1, the gene causative for a connective tissue disorder called Marfan Syndrome (MFS. The fact that the person did not have any cardiac alterations suggested compensation effects due to DS. This observation is supported by a previous DS meta-analysis at the molecular level where we have found an overall upregulation of FBN1 (which is usually downregulated in MFS. Additionally, that result was cross-validated with independent expression data from DS heart tissue. The aim of this work is to elucidate the role of FBN1 in DS and to establish a molecular link to MFS and MFS-related syndromes using a computational approach. To reach that, we conducted different analytical approaches over two DS studies (our previous meta-analysis and independent expression data from DS heart tissue and revealed expression alterations in the FBN1 interaction network, in FBN1 co-expressed genes and FBN1-related pathways. After merging the significant results from different datasets with a Bayesian approach, we prioritized 85 genes that were able to distinguish control from DS cases. We further found evidence for several of these genes (47%, such as FBN1, DCN, and COL1A2, being dysregulated in MFS and MFS-related diseases. Consequently, we further encourage the scientific community to take into account FBN1 and its related network for the study of DS cardiovascular characteristics.

  3. High Temperature Chemical Kinetic Combustion Modeling of Lightly Methylated Alkanes

    Energy Technology Data Exchange (ETDEWEB)

    Sarathy, S M; Westbrook, C K; Pitz, W J; Mehl, M

    2011-03-01

    Conventional petroleum jet and diesel fuels, as well as alternative Fischer-Tropsch (FT) fuels and hydrotreated renewable jet (HRJ) fuels, contain high molecular weight lightly branched alkanes (i.e., methylalkanes) and straight chain alkanes (n-alkanes). Improving the combustion of these fuels in practical applications requires a fundamental understanding of large hydrocarbon combustion chemistry. This research project presents a detailed high temperature chemical kinetic mechanism for n-octane and three lightly branched isomers octane (i.e., 2-methylheptane, 3-methylheptane, and 2,5-dimethylhexane). The model is validated against experimental data from a variety of fundamental combustion devices. This new model is used to show how the location and number of methyl branches affects fuel reactivity including laminar flame speed and species formation.

  4. Infrared Spectroscopic Investigation on CH Bond Acidity in Cationic Alkanes

    Science.gov (United States)

    Matsuda, Yoshiyuki; Xie, Min; Fujii, Asuka

    2016-06-01

    We have demonstrated large enhancements of CH bond acidities in alcohol, ether, and amine cations through infrared predissociation spectroscopy based on the vacuum ultraviolet photoionization detection. In this study, we investigate for the cationic alkanes (pentane, hexane, and heptane) with different alkyl chain lengths. The σ electrons are ejected in the ionization of alkanes, while nonbonding electrons are ejected in ionization of alcohols, ethers, and amines. Nevertheless, the acidity enhancements of CH in these cationic alkanes have also been demonstrated by infrared spectroscopy. The correlations of their CH bond acidities with the alkyl chain lengths as well as the mechanisms of their acidity enhancements will be discussed by comparison of infrared spectra and theoretical calculations.

  5. A Quick Estimate of the Correlation Energy for Alkanes

    Institute of Scientific and Technical Information of China (English)

    黎书华; 李伟; 马晶

    2003-01-01

    Within the localized molecular orbital description, the intraand interorbital pair correlation energies calculated with the coupled cluster doubles (CCD) theory have been obtained for methane, ethane, propane, butane, isobutane, pentane,isopentane and neopentane using the 6-31G* basis set. The results showed the quantitative transferability of pair correlation energies and gross orbital correlation energies within this series of molecules. Based on the gross orbital correlation energies of five sample alkanes (butane, isobutane, pentane,isopentane and neopentane), we have derived a simple linear relationship to estimate the CCD correlation energy for an arbitrary large alkane. The correlation energy predicted by this simple relationship remarkably recovers more than 98.9% of the exact CCD correlation energy for a number of alkanes containing six to eight carbon atoms. The relative stability of less branched isomers can be correctly predicted.

  6. Packing properties 1-alkanols and alkanes in a phospholipid membrane

    DEFF Research Database (Denmark)

    Westh, Peter

    2006-01-01

    into the membrane, Vm(puremem), was positive for small (C4-C6) 1-alkanols while it was negative for larger alcohols and all alkanes. The magnitude of Vm(puremem) ranged from about +4 cm3/mol for alcohols with an alkyl chain about half the length of the fatty acids of DMPC, to -10 to -15 cm3/mol for the alkanes......We have used vibrating tube densitometry to investigate the packing properties of four alkanes and a homologous series of ten alcohols in fluid-phase membranes of dimyristoyl phosphatidylcholine (DMPC). It was found that the volume change of transferring these compounds from their pure states...... and long chain alcohols. On the basis of these observations, previously published information on the structure of the membrane-solute complexes and the free volume properties of (pure) phospholipid membranes, we suggest that two effects dominate the packing properties of hydrophobic solutes in DMPC. First...

  7. Unidimensional diffusion of long n-alkanes in nanoporous channels.

    Science.gov (United States)

    Jobic, Hervé; Farago, Bela

    2008-11-07

    The diffusion of long n-alkanes confined in silicalite zeolite has been studied with the neutron spin-echo technique. Since only isotropic diffusion has been measured so far with this technique, we derive the intermediate scattering functions for one-dimensional (1D) and single-file diffusion. The 1D diffusion model explains the results obtained for long n-alkanes in the intersecting channel system of silicalite. A redistribution of the molecules is observed at high temperatures, supporting the presence of internal barriers within the zeolite crystals.

  8. Regioselective alkane hydroxylation with a mutant AlkB enzyme

    Science.gov (United States)

    Koch, Daniel J.; Arnold, Frances H.

    2012-11-13

    AlkB from Pseudomonas putida was engineered using in-vivo directed evolution to hydroxylate small chain alkanes. Mutant AlkB-BMO1 hydroxylates propane and butane at the terminal carbon at a rate greater than the wild-type to form 1-propanol and 1-butanol, respectively. Mutant AlkB-BMO2 similarly hydroxylates propane and butane at the terminal carbon at a rate greater than the wild-type to form 1-propanol and 1-butanol, respectively. These biocatalysts are highly active for small chain alkane substrates and their regioselectivity is retained in whole-cell biotransformations.

  9. Squeezing molecularly thin alkane lubrication films: Layering transistions and wear

    DEFF Research Database (Denmark)

    Sivebæk, Ion Marius; Samoilov, V. N.; Persson, B. N. J.

    2004-01-01

    The properties of alkane lubricants confined between two approaching solids are investigated by a model that accounts for the curvature and the elastic properties of the solid surfaces. We consider linear alkane molecules of different chain lengths, C(3)H(8); C(4)H(10); C(8)H(18); C(9)H(20); C(10)H......(22); C(12)H(26), and C(14)H(30) confined between smooth gold surfaces. We observe well-defined molecular layers develop in the lubricant film when the width of the film is of the order of a few atomic diameters. An external squeezing-pressure induces discontinuous changes in the number n of lubricant...

  10. On the relation between Zenkevich and Wiener indices of alkanes

    Directory of Open Access Journals (Sweden)

    ZARKO BOSKOVIC

    2004-04-01

    Full Text Available A relatively complicated relation was found to exist between the quantity U, recently introduced by Zenkevich (providing a measure of internal molecular energy, and the Wiener index W (measuring molecular surface area and intermolecular forces. We now report a detailed analysis of this relation and show that, in the case of alkanes, its main features are reproduced by the formula U = –aW + b + gn1; where n1 is the number of methyl groups, and a, b and g are constants, depending only on the number of carbon atoms. Thus, for isomeric alkanes with the same number of methyl groups, U and W are linearly correlated.

  11. Experimental Evidence on the Effects of Home Computers on Academic Achievement among Schoolchildren

    OpenAIRE

    Robert W. Fairlie; Robinson, Jonathan

    2013-01-01

    Computers are an important part of modern education, yet large segments of the population – especially low-income and minority children – lack access to a computer at home. Does this impede educational achievement? We test this hypothesis by conducting the largest-ever field experiment involving the random provision of free computers for home use to students. 1,123 schoolchildren grades 6-10 in 15 California schools participated in the experiment. Although the program significantly increased ...

  12. Computer simulation, rhetoric, and the scientific imagination how virtual evidence shapes science in the making and in the news

    CERN Document Server

    Roundtree, Aimee Kendall

    2013-01-01

    Computer simulations help advance climatology, astrophysics, and other scientific disciplines. They are also at the crux of several high-profile cases of science in the news. How do simulation scientists, with little or no direct observations, make decisions about what to represent? What is the nature of simulated evidence, and how do we evaluate its strength? Aimee Kendall Roundtree suggests answers in Computer Simulation, Rhetoric, and the Scientific Imagination. She interprets simulations in the sciences by uncovering the argumentative strategies that underpin the production and disseminati

  13. 40 CFR 721.10148 - Acryloxy alkanoic alkane derivative with mixed metal oxides (generic).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Acryloxy alkanoic alkane derivative... Significant New Uses for Specific Chemical Substances § 721.10148 Acryloxy alkanoic alkane derivative with...) The chemical substance identified generically as acryloxy alkanoic alkane derivative with mixed...

  14. 40 CFR 721.785 - Halogenated alkane aromatic compound (generic name).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Halogenated alkane aromatic compound... Specific Chemical Substances § 721.785 Halogenated alkane aromatic compound (generic name). (a) Chemical... as a halogenated alkane aromatic compound (PMN P-94-1747) is subject to reporting under this...

  15. Selective conversion of butane into liquid hydrocarbon fuels on alkane metathesis catalysts

    KAUST Repository

    Szeto, Kaï Chung

    2012-01-01

    We report a selective direct conversion of n-butane into higher molecular weight alkanes (C 5+) by alkane metathesis reaction catalysed by silica-alumina supported tungsten or tantalum hydrides at moderate temperature and pressure. The product is unprecedented, asymmetrically distributed towards heavier alkanes. This journal is © 2012 The Royal Society of Chemistry.

  16. Parameters, Predictions, and Evidence in Computational Modeling: A Statistical View Informed by ACT-R

    Science.gov (United States)

    Weaver, Rhiannon

    2008-01-01

    Model validation in computational cognitive psychology often relies on methods drawn from the testing of theories in experimental physics. However, applications of these methods to computational models in typical cognitive experiments can hide multiple, plausible sources of variation arising from human participants and from stochastic cognitive…

  17. Measurement and Evidence of Computer-Based Task Switching and Multitasking by "Net Generation" Students

    Science.gov (United States)

    Judd, Terry; Kennedy, Gregor

    2011-01-01

    Logs of on-campus computer and Internet usage were used to conduct a study of computer-based task switching and multitasking by undergraduate medical students. A detailed analysis of over 6000 individual sessions revealed that while a majority of students engaged in both task switching and multitasking behaviours, they did so less frequently than…

  18. On the Need for Research Evidence to Guide the Design of Computer Games for Learning

    Science.gov (United States)

    Mayer, Richard E.

    2015-01-01

    Computer games for learning (also called video games or digital games) have potential to improve education. This is the intriguing idea that motivates this special issue of the "Educational Psychologist" on "Psychological Perspectives on Digital Games and Learning." Computer games for learning are games delivered via computer…

  19. Efficacy of individual computer-based auditory training for people with hearing loss: a systematic review of the evidence.

    Directory of Open Access Journals (Sweden)

    Helen Henshaw

    Full Text Available BACKGROUND: Auditory training involves active listening to auditory stimuli and aims to improve performance in auditory tasks. As such, auditory training is a potential intervention for the management of people with hearing loss. OBJECTIVE: This systematic review (PROSPERO 2011: CRD42011001406 evaluated the published evidence-base for the efficacy of individual computer-based auditory training to improve speech intelligibility, cognition and communication abilities in adults with hearing loss, with or without hearing aids or cochlear implants. METHODS: A systematic search of eight databases and key journals identified 229 articles published since 1996, 13 of which met the inclusion criteria. Data were independently extracted and reviewed by the two authors. Study quality was assessed using ten pre-defined scientific and intervention-specific measures. RESULTS: Auditory training resulted in improved performance for trained tasks in 9/10 articles that reported on-task outcomes. Although significant generalisation of learning was shown to untrained measures of speech intelligibility (11/13 articles, cognition (1/1 articles and self-reported hearing abilities (1/2 articles, improvements were small and not robust. Where reported, compliance with computer-based auditory training was high, and retention of learning was shown at post-training follow-ups. Published evidence was of very-low to moderate study quality. CONCLUSIONS: Our findings demonstrate that published evidence for the efficacy of individual computer-based auditory training for adults with hearing loss is not robust and therefore cannot be reliably used to guide intervention at this time. We identify a need for high-quality evidence to further examine the efficacy of computer-based auditory training for people with hearing loss.

  20. Theoretical study of n-alkane adsorption on metal surfaces

    DEFF Research Database (Denmark)

    Morikawa, Yoshitada; Ishii, Hisao; Seki, Kazuhiko

    2004-01-01

    The interaction between n-alkane and metal surfaces has been studied by means of density-functional theoretical calculations within a generalized gradient approximation (GGA). We demonstrate that although the GGA cannot reproduce the physisorption energy well, our calculations can reproduce the e...

  1. MODELING OF ALKANE EMISSIONS FROM A WOOD STAIN

    Science.gov (United States)

    The article discusses full-scale residential house tests to evaluate the effects of organic emissions from a wood finishing product--wood stain--on indoor air quality (IAQ). The test house concentrations of three alkane species, nonane, decane, and undecane, were measured as a fu...

  2. Cyano- and polycyanometallo-porphyrins as catalysts for alkane oxidation

    Science.gov (United States)

    Ellis, Jr., Paul E.; Lyons, James E.

    1993-01-01

    New compositions of matter comprising cyano-substituted metal complexes of porphyrins are catalysts for the oxidation of alkanes. The metal is iron, chromium, manganese, ruthenium, copper or cobalt. The porphyrin ring has cyano groups attached thereto in meso and/or .beta.-pyrrolic positions.

  3. Improving alkane synthesis in Escherichia coli via metabolic engineering.

    Science.gov (United States)

    Song, Xuejiao; Yu, Haiying; Zhu, Kun

    2016-01-01

    Concerns about energy security and global petroleum supply have made the production of renewable biofuels an industrial imperative. The ideal biofuels are n-alkanes in that they are chemically and structurally identical to the fossil fuels and can "drop in" to the transportation infrastructure. In this work, an Escherichia coli strain that produces n-alkanes was constructed by heterologous expression of acyl-acyl carrier protein (ACP) reductase (AAR) and aldehyde deformylating oxygenase (ADO) from Synechococcus elongatus PCC7942. The accumulation of alkanes ranged from 3.1 to 24.0 mg/L using different expressing strategies. Deletion of yqhD, an inherent aldehyde reductase in E. coli, or overexpression of fadR, an activator for fatty acid biosynthesis, exhibited a nearly twofold increase in alkane titers, respectively. Combining yqhD deletion and fadR overexpression resulted in a production titer of 255.6 mg/L in E. coli, and heptadecene was the most abundant product.

  4. Cyano- and polycyanometalloporphyrins as catalysts for alkane oxidation

    Science.gov (United States)

    Ellis, Jr., Paul E.; Lyons, James E.

    1992-01-01

    Alkanes are oxidized by contact with oxygen-containing gas in the presence as catalyst of a metalloporphyrin in which hydrogen atoms in the porphyrin ring have been substituted with one or more cyano groups. Hydrogen atoms in the porphyrin ring may also be substituted with halogen atoms.

  5. Integrated process for preparing a carboxylic acid from an alkane

    Science.gov (United States)

    Benderly, Abraham; Chadda, Nitin; Sevon, Douglass

    2011-12-20

    The present invention relates to an integrated process for producing unsaturated carboxylic acids from the corresponding C.sub.2-C.sub.4 alkane. The process begins with performance of thermally integrated dehydrogenation reactions which convert a C.sub.2-C.sub.4 alkane to its corresponding C.sub.2-C.sub.4 alkene, and which involve exothermically converting a portion of an alkane to its corresponding alkene by oxidative dehydrogenation in an exothermic reaction zone, in the presence of oxygen and a suitable catalyst, and then feeding the products of the exothermic reaction zone to an endothermic reaction zone wherein at least a portion of the remaining unconverted alkane is endothermically dehydrogenated to form an additional quantity of the same corresponding alkene, in the presence of carbon dioxide and an other suitable catalyst. The alkene products of the thermally integrated dehydrogenation reactions are then provided to a catalytic vapor phase partial oxidation process for conversion of the alkene to the corresponding unsaturated carboxylic acid or nitrile. Unreacted alkene and carbon dioxide are recovered from the oxidation product stream and recycled back to the thermally integrated dehydrogenation reactions.

  6. Diffusion of squalene in n-alkanes and squalane.

    Science.gov (United States)

    Kowert, Bruce A; Watson, Michael B; Dang, Nhan C

    2014-02-27

    Squalene, an intermediate in the biosynthesis of cholesterol, has a 24-carbon backbone with six methyl groups and six isolated double bonds. Capillary flow techniques have been used to determine its translational diffusion constant, D, at room temperature in squalane, n-C16, and three n-C8-squalane mixtures. The D values have a weaker dependence on viscosity, η, than predicted by the Stokes-Einstein relation, D = kBT/(6πηr). A fit to the modified relation, D/T = ASE/η(p), gives p = 0.820 ± 0.028; p = 1 for the Stokes-Einstein limit. The translational motion of squalene appears to be much like that of n-alkane solutes with comparable chain lengths; their D values show similar deviations from the Stokes-Einstein model. The n-alkane with the same carbon chain length as squalene, n-C24, has a near-equal p value of 0.844 ± 0.018 in n-alkane solvents. The values of the hydrodynamic radius, r, for n-C24, squalene, and other n-alkane solutes decrease as the viscosity increases and have a common dependence on the van der Waals volumes of the solute and solvent. The possibility of studying squalene in lipid droplets and membranes is discussed.

  7. Catalytic production of branched small alkanes from biohydrocarbons.

    Science.gov (United States)

    Oya, Shin-ichi; Kanno, Daisuke; Watanabe, Hideo; Tamura, Masazumi; Nakagawa, Yoshinao; Tomishige, Keiichi

    2015-08-10

    Squalane, C30 algae-derived branched hydrocarbon, was successfully converted to smaller hydrocarbons without skeletal isomerization and aromatization over ruthenium on ceria (Ru/CeO2 ). The internal CH2 CH2 bonds located between branches are preferably dissociated to give branched alkanes with very simple distribution as compared with conventional methods using metal-acid bifunctional catalysts.

  8. Isolating the non-polar contributions to the intermolecular potential for water-alkane interactions.

    Science.gov (United States)

    Ballal, Deepti; Venkataraman, Pradeep; Fouad, Wael A; Cox, Kenneth R; Chapman, Walter G

    2014-08-14

    Intermolecular potential models for water and alkanes describe pure component properties fairly well, but fail to reproduce properties of water-alkane mixtures. Understanding interactions between water and non-polar molecules like alkanes is important not only for the hydrocarbon industry but has implications to biological processes as well. Although non-polar solutes in water have been widely studied, much less work has focused on water in non-polar solvents. In this study we calculate the solubility of water in different alkanes (methane to dodecane) at ambient conditions where the water content in alkanes is very low so that the non-polar water-alkane interactions determine solubility. Only the alkane-rich phase is simulated since the fugacity of water in the water rich phase is calculated from an accurate equation of state. Using the SPC/E model for water and TraPPE model for alkanes along with Lorentz-Berthelot mixing rules for the cross parameters produces a water solubility that is an order of magnitude lower than the experimental value. It is found that an effective water Lennard-Jones energy ε(W)/k = 220 K is required to match the experimental water solubility in TraPPE alkanes. This number is much higher than used in most simulation water models (SPC/E-ε(W)/k = 78.2 K). It is surprising that the interaction energy obtained here is also higher than the water-alkane interaction energy predicted by studies on solubility of alkanes in water. The reason for this high water-alkane interaction energy is not completely understood. Some factors that might contribute to the large interaction energy, such as polarizability of alkanes, octupole moment of methane, and clustering of water at low concentrations in alkanes, are examined. It is found that, though important, these factors do not completely explain the anomalously strong attraction between alkanes and water observed experimentally.

  9. The prevalence of encoded digital trace evidence in the nonfile space of computer media(,) (.).

    Science.gov (United States)

    Garfinkel, Simson L

    2014-09-01

    Forensically significant digital trace evidence that is frequently present in sectors of digital media not associated with allocated or deleted files. Modern digital forensic tools generally do not decompress such data unless a specific file with a recognized file type is first identified, potentially resulting in missed evidence. Email addresses are encoded differently for different file formats. As a result, trace evidence can be categorized as Plain in File (PF), Encoded in File (EF), Plain Not in File (PNF), or Encoded Not in File (ENF). The tool bulk_extractor finds all of these formats, but other forensic tools do not. A study of 961 storage devices purchased on the secondary market and shows that 474 contained encoded email addresses that were not in files (ENF). Different encoding formats are the result of different application programs that processed different kinds of digital trace evidence. Specific encoding formats explored include BASE64, GZIP, PDF, HIBER, and ZIP.

  10. Role of ozone in SOA formation from alkane photooxidation

    Directory of Open Access Journals (Sweden)

    X. Zhang

    2013-09-01

    Full Text Available Long-chain alkanes, which can be categorized as intermediate volatile organic compounds (IVOCs, are an important source of secondary organic aerosol (SOA. Mechanisms for the gas-phase OH-initiated oxidation of long-chain alkanes have been well documented; particle-phase chemistry, however, has received less attention. The δ-hydroxycarbonyl, which is generated from the isomerization of alkoxy radicals, can undergo heterogeneous cyclization to form substituted dihydrofuran. Due to the presence of C=C bonds, the substituted dihydrofuran is predicted to be highly reactive with OH, and even more so with O3 and NO3, thus opening a reaction pathway that is not usually accessible to alkanes. This work focuses on the role of substituted dihydrofuran formation and its subsequent reaction with OH, and more importantly ozone, in SOA formation from the photooxidation of long-chain alkanes. Experiments were carried out in the Caltech Environmental Chamber using dodecane as a representative alkane to investigate the difference in aerosol composition generated from "OH-oxidation dominating" vs. "ozonolysis dominating" environments. A detailed mechanism incorporating the specific gas-phase photochemistry, together with the heterogeneous formation of substituted dihydrofuran and its subsequent gas-phase OH/O3 oxidation, is presented to evaluate the importance of this reaction channel in the dodecane SOA formation. We conclude that: (1 the formation of δ-hydroxycarbonyl and its subsequent heterogeneous conversion to substituted dihydrofuran is significant in the presence of NOx; (2 the ozonolysis of substituted dihydrofuran dominates over the OH-initiated oxidation under conditions prevalent in urban and rural air; and (3 a spectrum of highly-oxygenated products with carboxylic acid, ester, and ether functional groups are produced from the substituted dihydrofuran chemistry, thereby affecting the average oxidation state of the SOA.

  11. Reconstitution of plant alkane biosynthesis in yeast demonstrates that Arabidopsis ECERIFERUM1 and ECERIFERUM3 are core components of a very-long-chain alkane synthesis complex.

    Science.gov (United States)

    Bernard, Amélie; Domergue, Frédéric; Pascal, Stéphanie; Jetter, Reinhard; Renne, Charlotte; Faure, Jean-Denis; Haslam, Richard P; Napier, Johnathan A; Lessire, René; Joubès, Jérôme

    2012-07-01

    In land plants, very-long-chain (VLC) alkanes are major components of cuticular waxes that cover aerial organs, mainly acting as a waterproof barrier to prevent nonstomatal water loss. Although thoroughly investigated, plant alkane synthesis remains largely undiscovered. The Arabidopsis thaliana ECERIFERUM1 (CER1) protein has been recognized as an essential element of wax alkane synthesis; nevertheless, its function remains elusive. In this study, a screen for CER1 physical interaction partners was performed. The screen revealed that CER1 interacts with the wax-associated protein ECERIFERUM3 (CER3) and endoplasmic reticulum-localized cytochrome b5 isoforms (CYTB5s). The functional relevance of these interactions was assayed through an iterative approach using yeast as a heterologous expression system. In a yeast strain manipulated to produce VLC acyl-CoAs, a strict CER1 and CER3 coexpression resulted in VLC alkane synthesis. The additional presence of CYTB5s was found to enhance CER1/CER3 alkane production. Site-directed mutagenesis showed that CER1 His clusters are essential for alkane synthesis, whereas those of CER3 are not, suggesting that CYTB5s are specific CER1 cofactors. Collectively, our study reports the identification of plant alkane synthesis enzymatic components and supports a new model for alkane production in which CER1 interacts with both CER3 and CYTB5 to catalyze the redox-dependent synthesis of VLC alkanes from VLC acyl-CoAs.

  12. Electronic transport in disordered n-alkanes: From fluid methane to amorphous polyethylene

    Science.gov (United States)

    Cubero, David; Quirke, Nicholas; Coker, David F.

    2003-08-01

    We use a fast Fourier transform block Lanczos diagonalization algorithm to study the electronic states of excess electrons in fluid alkanes (methane, ethane, and propane) and in a molecular model of amorphous polyethylene (PE) relevant to studies of space charge in insulating polymers. We obtain a new pseudopotential for electron-PE interactions by fitting to the electronic properties of fluid alkanes and use this to obtain new results for electron transport in amorphous PE. From our simulations, while the electronic states in fluid methane are extended throughout the whole sample, in amorphous PE there is a transition between localized and delocalized states slightly above the vacuum level (˜+0.06 eV). The localized states in our amorphous PE model extend to -0.33 eV below this level. Using the Kubo-Greenwood equation we compute the zero-field electron mobility in pure amorphous PE to be μ≈2×10-3 cm2/V s. Our results highlight the importance of electron transport through extended states in amorphous regions to an understanding of electron transport in PE.

  13. Auditors’ Usage of Computer Assisted Audit Tools and Techniques: Empirical Evidence from Nigeria

    Directory of Open Access Journals (Sweden)

    Appah Ebimobowei

    2013-06-01

    Full Text Available This study examines use of computer assisted audit tool and techniques in audit practice in the Niger Delta of Nigeria. To achieve this objective, data was collected from primary and secondary sources. The secondary sources were from scholarly books and journals while the primary source involved a well structured questionnaire of three sections of thirty seven items with an average reliability of 0.838. The data collected from the questionnaire were analyzed using relevant descriptive statistics, diagnostics tests, Augmented Dickey-fuller and multiple regressions. The result revealed that performance expectancy, effort expectancy, facilitating conditions and social influence were positively associated at (0.05 to the usage of computer assisted audit tools and techniques by accounting firms. Hence, the study concludes that the adoption of computer assisted audit tools and techniques has become a beneficial choice for auditors in the 21st century complex business environment and an efficient tool to increase the productivity as well as the audit functions. Therefore, professional accountants need to expand their knowledge of information technology and computer accounting audit methodology; the syllabus of accounting programmes for professional and tertiary institutions should be reviewed to include courses in computer accounting information system audit; relevant professional accountancy bodies in Nigeria should also include courses in computer information system audit as part of their training programmes and professional accountants should be made to appreciate the relevance of computer in the 21st century business environment in the provision of relevant accounting services for the sole aim of satisfying their clients and also audit firms need to increase their organizational and technical support to encourage the use of CAATTs.

  14. Distribution and sources of n-alkanes in surface sediments of Taihu Lake, China

    Directory of Open Access Journals (Sweden)

    Yu Yunlong

    2016-03-01

    Full Text Available The last study on n-alkanes in surface sediments of Taihu Lake was in 2000, only 13 surface sediment samples were analysed, in order to have a comprehensive and up-to-date understanding of n-alkanes in the surface sediments of Taihu Lake, 41 surface sediment samples were analyzed by GC-MS. C10 to C37 were detected, the total concentrations of n-alkanes ranged from 2109 ng g−1 to 9096 ng g−1 (dry weight. There was strong odd carbon predominance in long chain n-alkanes and even carbon predominance in short chain n-alkanes. When this finding was combined with the analysis results of wax n-alkanes (WaxCn, carbon preference index (CPI, unresolved complex mixture (UCM, hopanes and steranes, it was considered that the long chain n-alkanes were mainly from terrigenous higher plants, and that the short chain n-alkanes mainly originated from bacteria and algae in the lake, compared with previous studies, there were no obvious anthropogenic petrogenic inputs. Terrestrial and aquatic hydrocarbons ratio (TAR and C21−/C25+ indicated that terrigenous input was higher than aquatic sources and the nearshore n-alkanes were mainly from land-derived sources. Moreover, the distribution of short chain n-alkanes presented a relatively uniform pattern, while the long chain n-alkanes presented a trend that concentrations dropped from nearshore places to the middle of lake.

  15. Image Charge Effects in the Wetting Behavior of Alkanes on Water with Accounting for Water Solubility

    Directory of Open Access Journals (Sweden)

    Kirill A. Emelyanenko

    2016-03-01

    Full Text Available Different types of surface forces, acting in the films of pentane, hexane, and heptane on water are discussed. It is shown that an important contribution to the surface forces originates from the solubility of water in alkanes. The equations for the distribution of electric potential inside the film are derived within the Debye-Hückel approximation, taking into account the polarization of the film boundaries by discrete charges at water-alkane interface and by the dipoles of water molecules dissolved in the film. On the basis of above equations we estimate the image charge contribution to the surface forces, excess free energy, isotherms of water adsorption in alkane film, and the total isotherms of disjoining pressure in alkane film. The results indicate the essential influence of water/alkane interface charging on the disjoining pressure in alkane films, and the wettability of water surface by different alkanes is discussed.

  16. Perspectives on Games, Computers, and Mental Health: Questions about Paradoxes, Evidences, and Challenges.

    Science.gov (United States)

    Desseilles, Martin

    2016-01-01

    In the field of mental health, games and computerized games present questions about paradoxes, evidences, and challenges. This perspective article offers perspectives and personal opinion about these questions, evidences, and challenges with an objective of presenting several ideas and issues in this rapidly developing field. First, games raise some questions in the sense of the paradox between a game and an issue, as well as the paradox of using an amusing game to treat a serious pathology. Second, games also present evidence in the sense that they involve relationships with others, as well as learning, communication, language, emotional regulation, and hedonism. Third, games present challenges, such as the risk of abuse, the critical temporal period that may be limited to childhood, their important influence on sociocognitive learning and the establishment of social norms, and the risk of misuse of games.

  17. DNA minor groove binding of small molecules: Experimental and computational evidence

    Indian Academy of Sciences (India)

    Prateek Pandya; Md Maidul Islam; G Suresh Kumar; B Jayaram; Surat Kumar

    2010-03-01

    Eight indole derivatives were studied for their DNA binding ability using fluorescence quenching and molecular docking methods. These indole compounds have structural moieties similar as in few indole alkaloids. Experimental and theoretical studies have suggested that indole derivatives bind in the minor groove of DNA. Thermodynamic profiles of DNA complexes of indole derivatives were obtained from computational methods. The complexes were largely stabilized by H-bonding and van der Waal’s forces with positive entropy values. Indole derivatives were found to possess some Purine (Pu) - Pyrimidine (Py) specificity with DNA sequences. The results obtained from experimental and computational methods showed good agreement with each other, supported by their correlation constant values.

  18. Sudden Cardiac Risk Stratification with Electrocardiographic Indices - A Review on Computational Processing, Technology Transfer, and Scientific Evidence.

    Science.gov (United States)

    Gimeno-Blanes, Francisco J; Blanco-Velasco, Manuel; Barquero-Pérez, Óscar; García-Alberola, Arcadi; Rojo-Álvarez, José L

    2016-01-01

    Great effort has been devoted in recent years to the development of sudden cardiac risk predictors as a function of electric cardiac signals, mainly obtained from the electrocardiogram (ECG) analysis. But these prediction techniques are still seldom used in clinical practice, partly due to its limited diagnostic accuracy and to the lack of consensus about the appropriate computational signal processing implementation. This paper addresses a three-fold approach, based on ECG indices, to structure this review on sudden cardiac risk stratification. First, throughout the computational techniques that had been widely proposed for obtaining these indices in technical literature. Second, over the scientific evidence, that although is supported by observational clinical studies, they are not always representative enough. And third, via the limited technology transfer of academy-accepted algorithms, requiring further meditation for future systems. We focus on three families of ECG derived indices which are tackled from the aforementioned viewpoints, namely, heart rate turbulence (HRT), heart rate variability (HRV), and T-wave alternans. In terms of computational algorithms, we still need clearer scientific evidence, standardizing, and benchmarking, siting on advanced algorithms applied over large and representative datasets. New scenarios like electronic health recordings, big data, long-term monitoring, and cloud databases, will eventually open new frameworks to foresee suitable new paradigms in the near future.

  19. Sudden Cardiac Risk Stratification with Electrocardiographic Indices - A Review on Computational Processing, Technology Transfer, and Scientific Evidence

    Directory of Open Access Journals (Sweden)

    Francisco Javier eGimeno-Blanes

    2016-03-01

    Full Text Available Great effort has been devoted in recent years to the development of sudden cardiac risk predictors as a function of electric cardiac signals, mainly obtained from the electrocardiogram (ECG analysis. But these prediction techniques are still seldom used in clinical practice, partly due to its limited diagnostic accuracy and to the lack of consensus about the appropriate computational signal processing implementation. This paper addresses a three-fold approach, based on ECG indexes, to structure this review on sudden cardiac risk stratification. First, throughout the computational techniques that had been widely proposed for obtaining these indexes in technical literature. Second, over the scientific evidence, that although is supported by observational clinical studies, they are not always representative enough. And third, via the limited technology transfer of academy-accepted algorithms, requiring further meditation for future systems. We focus on three families of ECG derived indexes which are tackled from the aforementioned viewpoints, namely, heart rate turbulence, heart rate variability, and T-wave alternans. In terms of computational algorithms, we still need clearer scientific evidence, standardizing, and benchmarking, siting on advanced algorithms applied over large and representative datasets. New scenarios like electronic health recordings, big data, long-term monitoring, and cloud databases, will eventually open new frameworks to foresee suitable new paradigms in the near future.

  20. Introducing a Computer Algebra System in Mathematics Education--Empirical Evidence from Germany

    Science.gov (United States)

    Schmidt, Karsten; Kohler, Anke; Moldenhauer, Wolfgang

    2009-01-01

    This paper reports on the effects the use of a pocket calculator-based computer algebra system (CAS) has on the performance in mathematics of grade 11 students in Germany. A project started at 8 of about one hundred upper secondary schools in the federal state of Thuringia in 1999; 3 years later the former restrictions on the use of technology in…

  1. The evidence of personal computer waste quantity in the territory of Serbia -statistical estimation

    Directory of Open Access Journals (Sweden)

    Tadić Branko

    2006-01-01

    Full Text Available In recent years, the state-of-the-art research has been dealing with putting into traffic, withdrawing and freeing the environment from electrical and electronic equipment waste-WEEE. In our country there has been no serious research so far concerning this problem, although current and future members of the European Union (EU are obligated to conduct WEEE directive based on individual responsibility of each "waste manufacturer". The Ministry of Science and Environmental Protection of Serbia has accepted the financing of scientific research project called "The development of electrical and electronic equipment recycling system". In this paper, statistical estimation method of quantity and diffusion of computer waste (which according to the EU classification, belongs to the third category WEEE-devices for computer and communication technique in the territory of Serbia is described. The implications of the problem on our country are also presented.

  2. An Interrogative Model of Computer-Aided Adaptive Testing: Some Experimental Evidence

    Science.gov (United States)

    1988-09-01

    aquired knowledge. This thesis proposes and validates a computer-aided testing model called the Interrogative Diagnostic Model (IDM). The model is...PROGRAM DESIGN The design of a program to implement the model vas quite straight forvard. dB&8B III Plus vas the language selected for Implementation...true/false. Due to the inability of the dBASE III Plus in processing natural language essay type questions vere excluded. The content of the questions

  3. Identification and use of an alkane transporter plug-in for application in biocatalysis and whole-cell biosensing of alkanes

    DEFF Research Database (Denmark)

    Grant, Chris; Deszcz, Dawid; Wei, Yu-Chia

    2014-01-01

    plug-in, specific yields improved by up to 100-fold for bioxidation of>C12 alkanes to fatty alcohols and acids. The alkL protein was shown to be toxic to the host when overexpressed but when expressed from a vector capable of controlled induction, yields of alkane oxidation were improved a further 10...

  4. Alkane biosynthesis genes in cyanobacteria and their transcriptional organization

    Directory of Open Access Journals (Sweden)

    Stephan eKlähn

    2014-07-01

    Full Text Available In cyanobacteria, alkanes are synthesized from a fatty acyl-ACP by two enzymes, acyl-acyl carrier protein reductase (AAR and aldehyde deformylating oxygenase (ADO. Despite the great interest in the exploitation for biofuel production, nothing is known about the transcriptional organization of their genes or the physiological function of alkane synthesis. The comparison of 115 microarray datasets indicates the relatively constitutive expression of aar and ado genes. The analysis of 181 available genomes showed that in 90% of the genomes both genes are present, likely indicating their physiological relevance. In 61% of them they cluster together with genes encoding acetyl-CoA carboxyl transferase and a short chain dehydrogenase, strengthening the link to fatty acid metabolism and in 76% of the genomes they are located in tandem, suggesting constraints on the gene arrangement. However, contrary to the expectations for an operon, we found in Synechocystis sp. PCC 6803 specific promoters for the two genes, sll0208 (ado and sll0209 (aar, that give rise to monocistronic transcripts. Moreover, the upstream located ado gene is driven by a proximal as well as a second, distal, promoter, from which a third transcript, the ~160 nt sRNA SyR9 is transcribed. Thus, the transcriptional organization of the alkane biosynthesis genes in Synechocystis sp. PCC 6803 is of substantial complexity. We verified all three promoters to function independently from each other and show a similar promoter arrangement also in the more distant Nodularia spumigena, Trichodesmium erythraeum, Anabaena sp. PCC 7120, Prochlorococcus MIT9313 and MED4. The presence of separate regulatory elements and the dominance of monocistronic mRNAs suggest the possible autonomous regulation of ado and aar. The complex transcriptional organization of the alkane synthesis gene cluster has possible metabolic implications and should be considered when manipulating the expression of these genes in

  5. Metal-organic framework for the separation of alkane isomers

    Energy Technology Data Exchange (ETDEWEB)

    Long, Jeffrey R.; Herm, Zoey R.; Wiers, Brian M.; Krishna, Rajamani

    2017-01-10

    A metal organic framework Fe.sub.2(bdp).sub.3 (BDP.sup.2-=1,4-benzenedipyrazolate) with triangular channels is particularly suited for C5-C7 separations of alkanes according to the number of branches in the molecule rather than by carbon number. The metal-organic framework can offer pore geometries that is unavailable in zeolites or other porous media, facilitating distinct types of shape-based molecular separations.

  6. Alkane production from biomass: chemo-, bio- and integrated catalytic approaches.

    Science.gov (United States)

    Deneyer, Aron; Renders, Tom; Van Aelst, Joost; Van den Bosch, Sander; Gabriëls, Dries; Sels, Bert F

    2015-12-01

    Linear, branched and cyclic alkanes are important intermediates and end products of the chemical industry and are nowadays mainly obtained from fossil resources. In search for alternatives, biomass feedstocks are often presented as a renewable carbon source for the production of fuels, chemicals and materials. However, providing a complete market for all these applications seems unrealistic due to both financial and logistic issues. Despite the very large scale of current alkane-based fuel applications, biomass definitely has the potential to offer a partial solution to the fuel business. For the smaller market of chemicals and materials, a transition to biomass as main carbon source is more realistic and even probably unavoidable in the long term. The appropriate use and further development of integrated chemo- and biotechnological (catalytic) process strategies will be crucial to successfully accomplish this petro-to-bio feedstock transition. Furthermore, a selection of the most promising technologies from the available chemo- and biocatalytic tool box is presented. New opportunities will certainly arise when multidisciplinary approaches are further explored in the future. In an attempt to select the most appropriate biomass sources for each specific alkane-based application, a diagram inspired by van Krevelen is applied, taking into account both the C-number and the relative functionality of the product molecules.

  7. Vision therapy and computer orthoptics: evidence-based approach to use in your practice.

    Science.gov (United States)

    Lambert, Jennifer

    2013-01-01

    Convergence insufficiency is a commonly seen disorder of the vergence system. Its clinical characteristics and symptoms have been well described by Duane and von Graefe. Laboratory studies have clarified the vergence pathway, which includes a bi-phasic response. Several recent randomized controlled trials show the effectiveness of common treatment modalities, including pencil pushups, computer orthoptics, and office-based therapy. More studies are needed to investigate the possibility that other treatments may treat convergence insufficiency in a more profound way by acting on other parts of the vergence system.

  8. On the inclusion of alkanes into the monolayer of aliphatic alcohols at the water/alkane vapor interface: a quantum chemical approach.

    Science.gov (United States)

    Vysotsky, Yuri B; Fomina, Elena S; Belyaeva, Elena A; Fainerman, Valentin B; Vollhardt, Dieter

    2013-02-14

    In the framework of the quantum chemical semiempirical PM3 method thermodynamic and structural parameters of the formation and clusterization of aliphatic alcohols C(n)H(2n+1)OH (n(OH) = 8-16) at 298 K at the water/alkane vapor C(n)H(2n+2), (n(CH(3)) = 6-16) interface were calculated. The dependencies of enthalpy, entropy and Gibbs' energy of clusterization per one monomer molecule of 2D films on the alkyl chain length of corresponding alcohols and alkanes, the molar fraction of alkanes in the monolayers and the immersion degree of alcohol molecules into the water phase were shown to be linear or stepwise. The threshold of spontaneous clusterization of aliphatic alcohols at the water/alkane vapor interface was 10-11 carbon atoms at 298 K which is in line with experimental data at the air/water interface. It is shown that the presence of alkane vapor does not influence the process of alcohol monolayer formation. The structure of these monolayers is analogous to those obtained at the air/water interface in agreement with experimental data. The inclusion of alkane molecules into the amphiphilic monolayer at the water/alkane vapor interface is possible for amphiphiles with the spontaneous clusterization threshold at the air/water interface (n(s)(0)) of at least 16 methylene units in the alkyl chain, and it does not depend on the molar fraction of alkanes in the corresponding monolayer. The inclusion of alkanes from the vapor phase into the amphiphilic monolayer also requires that the difference between the alkyl chain lengths of alcohols and alkanes is not larger than n(s)(0) - 15 and n(s)(0) - 14 for the 2D film 1 and 2D film 2, respectively.

  9. Evaluation of ESP textbooks: Evidence from ESP textbook of computer engineering major

    Directory of Open Access Journals (Sweden)

    Maryam Danaye Tous

    2013-11-01

    Full Text Available The purpose of this study was to evaluate ESP textbook on “English for the students of computer engineering” taught at Payame Noor University in Astane (Guilan province, Iran. It was a mixed method research. The research instrument consisted of a researcher-made questionnaire which was designed on the basis of eight checklist references. Sample of this study consisted of 49 junior students majoring in computer engineering, who were selected through convenience sampling method. The textbook was evaluated in terms of six criteria of aims and approaches, design and organization, skills and strategies, topics, practical considerations and illustrations, language content and exercises. Data was collected through a five-point Likert scale questionnaire consisting of 22 items. Descriptive statistics including percentage, mean, and standard deviation were calculated for each item. Findings indicated that despite having pedagogical values, the textbook was not very good according to design and organization, language content and exercises, skills and strategies, practical considerations and illustrations. Finally, the pedagogical implication of findings for teaching grammatical items, listening materials, recycling and revision, writing activities and illustrations would be discussed.

  10. Neural mechanisms of transient neocortical beta rhythms: Converging evidence from humans, computational modeling, monkeys, and mice

    Science.gov (United States)

    Sherman, Maxwell A.; Lee, Shane; Law, Robert; Haegens, Saskia; Thorn, Catherine A.; Hämäläinen, Matti S.; Moore, Christopher I.; Jones, Stephanie R.

    2016-01-01

    Human neocortical 15–29-Hz beta oscillations are strong predictors of perceptual and motor performance. However, the mechanistic origin of beta in vivo is unknown, hindering understanding of its functional role. Combining human magnetoencephalography (MEG), computational modeling, and laminar recordings in animals, we present a new theory that accounts for the origin of spontaneous neocortical beta. In our MEG data, spontaneous beta activity from somatosensory and frontal cortex emerged as noncontinuous beta events typically lasting <150 ms with a stereotypical waveform. Computational modeling uniquely designed to infer the electrical currents underlying these signals showed that beta events could emerge from the integration of nearly synchronous bursts of excitatory synaptic drive targeting proximal and distal dendrites of pyramidal neurons, where the defining feature of a beta event was a strong distal drive that lasted one beta period (∼50 ms). This beta mechanism rigorously accounted for the beta event profiles; several other mechanisms did not. The spatial location of synaptic drive in the model to supragranular and infragranular layers was critical to the emergence of beta events and led to the prediction that beta events should be associated with a specific laminar current profile. Laminar recordings in somatosensory neocortex from anesthetized mice and awake monkeys supported these predictions, suggesting this beta mechanism is conserved across species and recording modalities. These findings make several predictions about optimal states for perceptual and motor performance and guide causal interventions to modulate beta for optimal function. PMID:27469163

  11. COMPUTING

    CERN Multimedia

    M. Kasemann

    Overview In autumn the main focus was to process and handle CRAFT data and to perform the Summer08 MC production. The operational aspects were well covered by regular Computing Shifts, experts on duty and Computing Run Coordination. At the Computing Resource Board (CRB) in October a model to account for service work at Tier 2s was approved. The computing resources for 2009 were reviewed for presentation at the C-RRB. The quarterly resource monitoring is continuing. Facilities/Infrastructure operations Operations during CRAFT data taking ran fine. This proved to be a very valuable experience for T0 workflows and operations. The transfers of custodial data to most T1s went smoothly. A first round of reprocessing started at the Tier-1 centers end of November; it will take about two weeks. The Computing Shifts procedure was tested full scale during this period and proved to be very efficient: 30 Computing Shifts Persons (CSP) and 10 Computing Resources Coordinators (CRC). The shift program for the shut down w...

  12. Constructing evidence-based treatment strategies using methods from computer science.

    Science.gov (United States)

    Pineau, Joelle; Bellemare, Marc G; Rush, A John; Ghizaru, Adrian; Murphy, Susan A

    2007-05-01

    This paper details a new methodology, instance-based reinforcement learning, for constructing adaptive treatment strategies from randomized trials. Adaptive treatment strategies are operationalized clinical guidelines which recommend the next best treatment for an individual based on his/her personal characteristics and response to earlier treatments. The instance-based reinforcement learning methodology comes from the computer science literature, where it was developed to optimize sequences of actions in an evolving, time varying system. When applied in the context of treatment design, this method provides the means to evaluate both the therapeutic and diagnostic effects of treatments in constructing an adaptive treatment strategy. The methodology is illustrated with data from the STAR*D trial, a multi-step randomized study of treatment alternatives for individuals with treatment-resistant major depressive disorder.

  13. Judgement heuristics and bias in evidence interpretation: The effects of computer generated exhibits.

    Science.gov (United States)

    Norris, Gareth

    2015-01-01

    The increasing use of multi-media applications, trial presentation software and computer generated exhibits (CGE) has raised questions as to the potential impact of the use of presentation technology on juror decision making. A significant amount of the commentary on the manner in which CGE exerts legal influence is largely anecdotal; empirical examinations too are often devoid of established theoretical rationalisations. This paper will examine a range of established judgement heuristics (for example, the attribution error, representativeness, simulation), in order to establish their appropriate application for comprehending legal decisions. Analysis of both past cases and empirical studies will highlight the potential for heuristics and biases to be restricted or confounded by the use of CGE. The paper will conclude with some wider discussion on admissibility, access to justice, and emerging issues in the use of multi-media in court.

  14. COMPUTING

    CERN Multimedia

    M. Kasemann

    Overview During the past three months activities were focused on data operations, testing and re-enforcing shift and operational procedures for data production and transfer, MC production and on user support. Planning of the computing resources in view of the new LHC calendar in ongoing. Two new task forces were created for supporting the integration work: Site Commissioning, which develops tools helping distributed sites to monitor job and data workflows, and Analysis Support, collecting the user experience and feedback during analysis activities and developing tools to increase efficiency. The development plan for DMWM for 2009/2011 was developed at the beginning of the year, based on the requirements from the Physics, Computing and Offline groups (see Offline section). The Computing management meeting at FermiLab on February 19th and 20th was an excellent opportunity discussing the impact and for addressing issues and solutions to the main challenges facing CMS computing. The lack of manpower is particul...

  15. COMPUTING

    CERN Multimedia

    I. Fisk

    2011-01-01

    Introduction CMS distributed computing system performed well during the 2011 start-up. The events in 2011 have more pile-up and are more complex than last year; this results in longer reconstruction times and harder events to simulate. Significant increases in computing capacity were delivered in April for all computing tiers, and the utilisation and load is close to the planning predictions. All computing centre tiers performed their expected functionalities. Heavy-Ion Programme The CMS Heavy-Ion Programme had a very strong showing at the Quark Matter conference. A large number of analyses were shown. The dedicated heavy-ion reconstruction facility at the Vanderbilt Tier-2 is still involved in some commissioning activities, but is available for processing and analysis. Facilities and Infrastructure Operations Facility and Infrastructure operations have been active with operations and several important deployment tasks. Facilities participated in the testing and deployment of WMAgent and WorkQueue+Request...

  16. COMPUTING

    CERN Multimedia

    P. McBride

    The Computing Project is preparing for a busy year where the primary emphasis of the project moves towards steady operations. Following the very successful completion of Computing Software and Analysis challenge, CSA06, last fall, we have reorganized and established four groups in computing area: Commissioning, User Support, Facility/Infrastructure Operations and Data Operations. These groups work closely together with groups from the Offline Project in planning for data processing and operations. Monte Carlo production has continued since CSA06, with about 30M events produced each month to be used for HLT studies and physics validation. Monte Carlo production will continue throughout the year in the preparation of large samples for physics and detector studies ramping to 50 M events/month for CSA07. Commissioning of the full CMS computing system is a major goal for 2007. Site monitoring is an important commissioning component and work is ongoing to devise CMS specific tests to be included in Service Availa...

  17. Biobased production of alkanes and alkenes through metabolic engineering of microorganisms

    DEFF Research Database (Denmark)

    Kang, Min Kyoung; Nielsen, Jens

    2016-01-01

    hydrocarbon biosynthesis, and in particular, alkanes and alkenes are important high-value chemicals as they can be utilized for a broad range of industrial purposes as well as ‘drop-in’ biofuels. Some microorganisms have the ability to biosynthesize alkanes and alkenes naturally, but their production level...... is extremely low. Therefore, there have been various attempts to recruit other microbial cell factories for production of alkanes and alkenes by applying metabolic engineering strategies. Here we review different pathways and involved enzymes for alkane and alkene production and discuss bottlenecks...

  18. Holistic Processing and Right Hemisphere Lateralization Do Not Always Go Together—Evidence from Computational Modeling

    Directory of Open Access Journals (Sweden)

    Janet H. Hsiao

    2011-05-01

    Full Text Available Studies on face recognition have suggested a relationship between holistic processing and right hemisphere (RH lateralization. Thus, it has long been assumed that holistic processing is a property of RH processing. Nevertheless, recent studies showed reduced holistic processing and increased RH lateralization in Chinese character recognition expertise, suggesting that these two effects may be separate processes. Through computational modeling, in which we implement a theory of hemispheric asymmetry in perception that posits a low spatial frequency bias in the RH and a high spatial frequency bias in the left hemisphere (i.e. the Double Filtering by Frequency Theory, Ivry & Robertson, 1998, here we show that when the recognition task relies purely on featural information, holistic processing increases whereas RH lateralization decreases with increasing stimulus similarity, and there is a negative correlation between them. In contrast, when the recognition task relies purely on configural information, although holistic processing also increases whereas RH lateralization decreases with increasing stimulus similarity, there is no correlation between them. This result suggests that holistic processing and RH lateralization are separate processes that can be influenced differentially by task requirements.

  19. Active paradigms of seizure anticipation: Computer model evidence for necessity of stimulation

    Science.gov (United States)

    Suffczynski, Piotr; Kalitzin, Stiliyan; da Silva, Fernando Lopes; Parra, Jaime; Velis, Demetrios; Wendling, Fabrice

    2008-11-01

    It has been shown that the analysis of electroencephalographic (EEG) signals submitted to an appropriate external stimulation (active paradigm) is efficient with respect to anticipating epileptic seizures [S. Kalitzin , Clin. Neurophysiol. 116, 718 (2005)]. To better understand how an active paradigm is able to detect properties of EEG signals by means of which proictal states can be identified, we performed a simulation study using a computational model of seizure generation of a hippocampal network. Applying the active stimulation methodology, we investigated (i) how changes in model parameters that lead to a transition from the normal ongoing EEG to an ictal pattern are reflected in the properties of the simulated EEG output signals and (ii) how the evolution of neuronal excitability towards seizures can be reconstructed from EEG data using an active paradigm, rather than passively, using only ongoing EEG signals. The simulations indicate that a stimulation paradigm combined with appropriate analytical tools, as proposed here, may yield information about the change in excitability that precedes the transition to a seizure. Such information is apparently not fully reflected in the ongoing EEG activity. These findings give strong support to the development and application of active paradigms with the aim of predicting the occurrence of a transition to an epileptic seizure.

  20. Cloning and expression of three ladA-type alkane monooxygenase genes from an extremely thermophilic alkane-degrading bacterium Geobacillus thermoleovorans B23.

    Science.gov (United States)

    Boonmak, Chanita; Takahashi, Yasunori; Morikawa, Masaaki

    2014-05-01

    An extremely thermophilic bacterium, Geobacillus thermoleovorans B23, is capable of degrading a broad range of alkanes (with carbon chain lengths ranging between C11 and C32) at 70 °C. Whole-genome sequence analysis revealed that unlike most alkane-degrading bacteria, strain B23 does not possess an alkB-type alkane monooxygenase gene. Instead, it possesses a cluster of three ladA-type genes, ladAαB23, ladAβB23, and ladB B23, on its chromosome, whose protein products share significant amino acid sequence identities, 49.8, 34.4, and 22.7 %, respectively, with that of ladA alkane monooxygenase gene found on a plasmid of Geobacillus thermodetrificans NG 80-2. Each of the three genes, ladAαB23, ladAβB23, and ladB B23, was heterologously expressed individually in an alkB1 deletion mutant strain, Pseudomonas fluorescens KOB2Δ1. It was found that all three genes were functional in P. fluorescens KOB2Δ1, and partially restored alkane degradation activity. In this study, we suggest that G. thermoleovorans B23 utilizes multiple LadA-type alkane monooxygenases for the degradation of a broad range of alkanes.

  1. Identification and use of an alkane transporter plug-in for applications in biocatalysis and whole-cell biosensing of alkanes.

    Science.gov (United States)

    Grant, Chris; Deszcz, Dawid; Wei, Yu-Chia; Martínez-Torres, Rubéns Julio; Morris, Phattaraporn; Folliard, Thomas; Sreenivasan, Rakesh; Ward, John; Dalby, Paul; Woodley, John M; Baganz, Frank

    2014-07-28

    Effective application of whole-cell devices in synthetic biology and biocatalysis will always require consideration of the uptake of molecules of interest into the cell. Here we demonstrate that the AlkL protein from Pseudomonas putida GPo1 is an alkane import protein capable of industrially relevant rates of uptake of C7-C16 n-alkanes. Without alkL expression, native E.coli n-alkane uptake was the rate-limiting step in both the whole-cell bioconversion of C7-C16 n-alkanes and in the activation of a whole-cell alkane biosensor by C10 and C11 alkanes. By coexpression of alkL as a transporter plug-in, specific yields improved by up to 100-fold for bioxidation of >C12 alkanes to fatty alcohols and acids. The alkL protein was shown to be toxic to the host when overexpressed but when expressed from a vector capable of controlled induction, yields of alkane oxidation were improved a further 10-fold (8 g/L and 1.7 g/g of total oxidized products). Further testing of activity on n-octane with the controlled expression vector revealed the highest reported rates of 120 μmol/min/g and 1 g/L/h total oxidized products. This is the first time AlkL has been shown to directly facilitate enhanced uptake of C10-C16 alkanes and represents the highest reported gain in product yields resulting from its use.

  2. Utilization of n-alkanes by a newly isolated strain of Acinetobacter venetianus: the role of two AlkB-type alkane hydroxylases.

    Science.gov (United States)

    Throne-Holst, Mimmi; Markussen, Sidsel; Winnberg, Asgeir; Ellingsen, Trond E; Kotlar, Hans-Kristian; Zotchev, Sergey B

    2006-09-01

    A bacterial strain capable of utilizing n-alkanes with chain lengths ranging from decane (C10H22) to tetracontane (C40H82) as a sole carbon source was isolated using a system for screening microorganisms able to grow on paraffin (mixed long-chain n-alkanes). The isolate, identified according to its 16S rRNA sequence as Acinetobacter venetianus, was designated A. venetianus 6A2. Two DNA fragments encoding parts of AlkB-type alkane hydroxylase homologues, designated alkMa and alkMb, were polymerase chain reaction-amplified from the genome of A. venetianus 6A2. To study the roles of these two alkM paralogues in n-alkane utilization in A. venetianus 6A2, we constructed alkMa, alkMb, and alkMa/alkMb disruption mutants. Studies on the growth patterns of the disruption mutants using n-alkanes with different chain lengths as sole carbon source demonstrated central roles for the alkMa and alkMb genes in utilization of C10 to C18 n-alkanes. Comparative analysis of these patterns also suggested different substrate preferences for AlkMa and AlkMb in n-alkane utilization. Because both single and double mutants were able to grow on n-alkanes with chain lengths of C20 and longer, we concluded that yet another enzyme(s) for the utilization of these n-alkanes must exist in A. venetianus 6A2.

  3. COMPUTING

    CERN Multimedia

    I. Fisk

    2013-01-01

    Computing activity had ramped down after the completion of the reprocessing of the 2012 data and parked data, but is increasing with new simulation samples for analysis and upgrade studies. Much of the Computing effort is currently involved in activities to improve the computing system in preparation for 2015. Operations Office Since the beginning of 2013, the Computing Operations team successfully re-processed the 2012 data in record time, not only by using opportunistic resources like the San Diego Supercomputer Center which was accessible, to re-process the primary datasets HTMHT and MultiJet in Run2012D much earlier than planned. The Heavy-Ion data-taking period was successfully concluded in February collecting almost 500 T. Figure 3: Number of events per month (data) In LS1, our emphasis is to increase efficiency and flexibility of the infrastructure and operation. Computing Operations is working on separating disk and tape at the Tier-1 sites and the full implementation of the xrootd federation ...

  4. Biodegraded Oil and Its High Molecular Weight (C35+) n-alkanes in the Qianmiqiao Region in the Bohai Bay Basin, Northern China

    Institute of Scientific and Technical Information of China (English)

    WANG Tieguan; ZHU Dan; LU Hong; ZHANG Zhihuan; YANG Chiyin

    2004-01-01

    With a production of 208.2 m3/d, heavy oil was produced by drill stem test (DST) from three shallow reservoirs in Sand Group Nos. Ⅰ and Ⅲ of the Neogene Guantao Formation (Ng1 and NgⅢ) and the Eogene Dongying Formation (Ed) in an exploratory well Ban-14-1 within the Qianmiqiao region, Bohai Bay Basin, northern China. Based on the GC and GC-MS data of theNgⅠand NgⅢheavy oil samples, all n-alkanes and most isoprenoid hydrocarbons are lost and the GC baseline appears as an evident "hump", implying a large quantity of unresolved complex mixture (UCM),which typically revealed a result of heavy biodegradation. However, there still is a complete series of C14-C73 n-alkanes in the high-temperature gas chromatograms (HTGC) of the heavy oil, among which, the abundance of C30- n-alkanes are drastically reduced. The C35-C55 high molecular weight (HMW) n-alkanes are at high abundance and show a normal distribution pattern with major peak at C43 and an obvious odd-carbon-number predominance with CPI37-55 and OEP45-49values of 1.17 and 1.16-1.20, respectively. According to GC-MS analysis, the heavy oil is characterized by dual source inputs of aquatic microbes and terrestrial higher plants. Various steranes and tricyclic terpanes indicate an algal origin, and hopane-type triterpanes, C24tetracyclic terpane and drimane series show the bacterial contribution. With the odd-carbonnumber preference, HMW n-alkanes provide significant information not only on higher plant source input and immaturity,but also on the strong resistibility to biodegradation.

  5. Computer

    CERN Document Server

    Atkinson, Paul

    2011-01-01

    The pixelated rectangle we spend most of our day staring at in silence is not the television as many long feared, but the computer-the ubiquitous portal of work and personal lives. At this point, the computer is almost so common we don't notice it in our view. It's difficult to envision that not that long ago it was a gigantic, room-sized structure only to be accessed by a few inspiring as much awe and respect as fear and mystery. Now that the machine has decreased in size and increased in popular use, the computer has become a prosaic appliance, little-more noted than a toaster. These dramati

  6. Two novel alkane hydroxylase-rubredoxin fusion genes isolated from a Dietzia bacterium and the functions of fused rubredoxin domains in long-chain n-alkane degradation.

    Science.gov (United States)

    Nie, Yong; Liang, Jieliang; Fang, Hui; Tang, Yue-Qin; Wu, Xiao-Lei

    2011-10-01

    Two alkane hydroxylase-rubredoxin fusion gene homologs (alkW1 and alkW2) were cloned from a Dietzia strain, designated DQ12-45-1b, which can grow on crude oil and n-alkanes ranging in length from 6 to 40 carbon atoms as sole carbon sources. Both AlkW1 and AlkW2 have an integral-membrane alkane monooxygenase (AlkB) conserved domain and a rubredoxin (Rd) conserved domain which are fused together. Phylogenetic analysis showed that these two AlkB-fused Rd domains formed a novel third cluster with all the Rds from the alkane hydroxylase-rubredoxin fusion gene clusters in Gram-positive bacteria and that this third cluster was distant from the known AlkG1- and AlkG2-type Rds. Expression of the alkW1 gene in DQ12-45-1b was induced when cells were grown on C(8) to C(32) n-alkanes as sole carbon sources, but expression of the alkW2 gene was not detected. Functional heterologous expression in an alkB deletion mutant of Pseudomonas fluorescens KOB2Δ1 suggested the alkW1 could restore the growth of KOB2Δ1 on C(14) and C(16) n-alkanes and induce faster growth on C(18) to C(32) n-alkanes than alkW1ΔRd, the Rd domain deletion mutant gene of alkW1, which also caused faster growth than KOB2Δ1 itself. In addition, the artificial fusion of AlkB from the Gram-negative P. fluorescens CHA0 and the Rds from both Gram-negative P. fluorescens CHA0 and Gram-positive Dietzia sp. DQ12-45-1b significantly increased the degradation of C(32) alkane compared to that seen with AlkB itself. In conclusion, the alkW1 gene cloned from Dietzia species encoded an alkane hydroxylase which increased growth on and degradation of n-alkanes up to C(32) in length, with its fused rubredoxin domain being necessary to maintain the functions. In addition, the fusion of alkane hydroxylase and rubredoxin genes from both Gram-positive and -negative bacteria can increase the degradation of long-chain n-alkanes (such as C(32)) in the Gram-negative bacterium.

  7. Cloning and expression of three ladA-type alkane monooxygenase genes from an extremely thermophilic alkane-degrading bacterium Geobacillus thermoleovorans B23

    OpenAIRE

    2014-01-01

    An extremely thermophilic bacterium, Geobacillus thermoleovorans B23, is capable of degrading a broad range of alkanes (with carbon chain lengths ranging between C11 and C32) at 70 A degrees C. Whole-genome sequence analysis revealed that unlike most alkane-degrading bacteria, strain B23 does not possess an alkB-type alkane monooxygenase gene. Instead, it possesses a cluster of three ladA-type genes, ladA alpha(B23), ladA beta(B23), and ladB (B23), on its chromosome, whose protein products sh...

  8. COMPUTING

    CERN Document Server

    I. Fisk

    2010-01-01

    Introduction It has been a very active quarter in Computing with interesting progress in all areas. The activity level at the computing facilities, driven by both organised processing from data operations and user analysis, has been steadily increasing. The large-scale production of simulated events that has been progressing throughout the fall is wrapping-up and reprocessing with pile-up will continue. A large reprocessing of all the proton-proton data has just been released and another will follow shortly. The number of analysis jobs by users each day, that was already hitting the computing model expectations at the time of ICHEP, is now 33% higher. We are expecting a busy holiday break to ensure samples are ready in time for the winter conferences. Heavy Ion An activity that is still in progress is computing for the heavy-ion program. The heavy-ion events are collected without zero suppression, so the event size is much large at roughly 11 MB per event of RAW. The central collisions are more complex and...

  9. COMPUTING

    CERN Multimedia

    M. Kasemann P. McBride Edited by M-C. Sawley with contributions from: P. Kreuzer D. Bonacorsi S. Belforte F. Wuerthwein L. Bauerdick K. Lassila-Perini M-C. Sawley

    Introduction More than seventy CMS collaborators attended the Computing and Offline Workshop in San Diego, California, April 20-24th to discuss the state of readiness of software and computing for collisions. Focus and priority were given to preparations for data taking and providing room for ample dialog between groups involved in Commissioning, Data Operations, Analysis and MC Production. Throughout the workshop, aspects of software, operating procedures and issues addressing all parts of the computing model were discussed. Plans for the CMS participation in STEP’09, the combined scale testing for all four experiments due in June 2009, were refined. The article in CMS Times by Frank Wuerthwein gave a good recap of the highly collaborative atmosphere of the workshop. Many thanks to UCSD and to the organizers for taking care of this workshop, which resulted in a long list of action items and was definitely a success. A considerable amount of effort and care is invested in the estimate of the comput...

  10. Preliminary assessment of halogenated alkanes as vapor-phase tracers

    Energy Technology Data Exchange (ETDEWEB)

    Adams, Michael C.; Moore, Joseph N.; Hirtz, Paul

    1991-01-01

    New tracers are needed to evaluate the efficiency of injection strategies in vapor-dominated environments. One group of compounds that seems to meet the requirements for vapor-phase tracing are the halogenated alkanes (HCFCs). HCFCs are generally nontoxic, and extrapolation of tabulated thermodynamic data indicate that they will be thermally stable and nonreactive in a geothermal environment. The solubilities and stabilities of these compounds, which form several homologous series, vary according to the substituent ratios of fluorine, chlorine, and hydrogen. Laboratory and field tests that will further define the suitability of HCFCs as vapor-phase tracers are under way.

  11. Evidence for Neural Computations of Temporal Coherence in an Auditory Scene and Their Enhancement during Active Listening.

    Science.gov (United States)

    O'Sullivan, James A; Shamma, Shihab A; Lalor, Edmund C

    2015-05-06

    The human brain has evolved to operate effectively in highly complex acoustic environments, segregating multiple sound sources into perceptually distinct auditory objects. A recent theory seeks to explain this ability by arguing that stream segregation occurs primarily due to the temporal coherence of the neural populations that encode the various features of an individual acoustic source. This theory has received support from both psychoacoustic and functional magnetic resonance imaging (fMRI) studies that use stimuli which model complex acoustic environments. Termed stochastic figure-ground (SFG) stimuli, they are composed of a "figure" and background that overlap in spectrotemporal space, such that the only way to segregate the figure is by computing the coherence of its frequency components over time. Here, we extend these psychoacoustic and fMRI findings by using the greater temporal resolution of electroencephalography to investigate the neural computation of temporal coherence. We present subjects with modified SFG stimuli wherein the temporal coherence of the figure is modulated stochastically over time, which allows us to use linear regression methods to extract a signature of the neural processing of this temporal coherence. We do this under both active and passive listening conditions. Our findings show an early effect of coherence during passive listening, lasting from ∼115 to 185 ms post-stimulus. When subjects are actively listening to the stimuli, these responses are larger and last longer, up to ∼265 ms. These findings provide evidence for early and preattentive neural computations of temporal coherence that are enhanced by active analysis of an auditory scene.

  12. COMPUTING

    CERN Multimedia

    I. Fisk

    2011-01-01

    Introduction It has been a very active quarter in Computing with interesting progress in all areas. The activity level at the computing facilities, driven by both organised processing from data operations and user analysis, has been steadily increasing. The large-scale production of simulated events that has been progressing throughout the fall is wrapping-up and reprocessing with pile-up will continue. A large reprocessing of all the proton-proton data has just been released and another will follow shortly. The number of analysis jobs by users each day, that was already hitting the computing model expectations at the time of ICHEP, is now 33% higher. We are expecting a busy holiday break to ensure samples are ready in time for the winter conferences. Heavy Ion The Tier 0 infrastructure was able to repack and promptly reconstruct heavy-ion collision data. Two copies were made of the data at CERN using a large CASTOR disk pool, and the core physics sample was replicated ...

  13. COMPUTING

    CERN Multimedia

    M. Kasemann

    Introduction More than seventy CMS collaborators attended the Computing and Offline Workshop in San Diego, California, April 20-24th to discuss the state of readiness of software and computing for collisions. Focus and priority were given to preparations for data taking and providing room for ample dialog between groups involved in Commissioning, Data Operations, Analysis and MC Production. Throughout the workshop, aspects of software, operating procedures and issues addressing all parts of the computing model were discussed. Plans for the CMS participation in STEP’09, the combined scale testing for all four experiments due in June 2009, were refined. The article in CMS Times by Frank Wuerthwein gave a good recap of the highly collaborative atmosphere of the workshop. Many thanks to UCSD and to the organizers for taking care of this workshop, which resulted in a long list of action items and was definitely a success. A considerable amount of effort and care is invested in the estimate of the co...

  14. COMPUTING

    CERN Multimedia

    I. Fisk

    2012-01-01

    Introduction Computing continued with a high level of activity over the winter in preparation for conferences and the start of the 2012 run. 2012 brings new challenges with a new energy, more complex events, and the need to make the best use of the available time before the Long Shutdown. We expect to be resource constrained on all tiers of the computing system in 2012 and are working to ensure the high-priority goals of CMS are not impacted. Heavy ions After a successful 2011 heavy-ion run, the programme is moving to analysis. During the run, the CAF resources were well used for prompt analysis. Since then in 2012 on average 200 job slots have been used continuously at Vanderbilt for analysis workflows. Operations Office As of 2012, the Computing Project emphasis has moved from commissioning to operation of the various systems. This is reflected in the new organisation structure where the Facilities and Data Operations tasks have been merged into a common Operations Office, which now covers everything ...

  15. COMPUTING

    CERN Multimedia

    M. Kasemann

    Introduction During the past six months, Computing participated in the STEP09 exercise, had a major involvement in the October exercise and has been working with CMS sites on improving open issues relevant for data taking. At the same time operations for MC production, real data reconstruction and re-reconstructions and data transfers at large scales were performed. STEP09 was successfully conducted in June as a joint exercise with ATLAS and the other experiments. It gave good indication about the readiness of the WLCG infrastructure with the two major LHC experiments stressing the reading, writing and processing of physics data. The October Exercise, in contrast, was conducted as an all-CMS exercise, where Physics, Computing and Offline worked on a common plan to exercise all steps to efficiently access and analyze data. As one of the major results, the CMS Tier-2s demonstrated to be fully capable for performing data analysis. In recent weeks, efforts were devoted to CMS Computing readiness. All th...

  16. COMPUTING

    CERN Multimedia

    P. McBride

    It has been a very active year for the computing project with strong contributions from members of the global community. The project has focused on site preparation and Monte Carlo production. The operations group has begun processing data from P5 as part of the global data commissioning. Improvements in transfer rates and site availability have been seen as computing sites across the globe prepare for large scale production and analysis as part of CSA07. Preparations for the upcoming Computing Software and Analysis Challenge CSA07 are progressing. Ian Fisk and Neil Geddes have been appointed as coordinators for the challenge. CSA07 will include production tests of the Tier-0 production system, reprocessing at the Tier-1 sites and Monte Carlo production at the Tier-2 sites. At the same time there will be a large analysis exercise at the Tier-2 centres. Pre-production simulation of the Monte Carlo events for the challenge is beginning. Scale tests of the Tier-0 will begin in mid-July and the challenge it...

  17. COMPUTING

    CERN Multimedia

    I. Fisk

    2010-01-01

    Introduction The first data taking period of November produced a first scientific paper, and this is a very satisfactory step for Computing. It also gave the invaluable opportunity to learn and debrief from this first, intense period, and make the necessary adaptations. The alarm procedures between different groups (DAQ, Physics, T0 processing, Alignment/calibration, T1 and T2 communications) have been reinforced. A major effort has also been invested into remodeling and optimizing operator tasks in all activities in Computing, in parallel with the recruitment of new Cat A operators. The teams are being completed and by mid year the new tasks will have been assigned. CRB (Computing Resource Board) The Board met twice since last CMS week. In December it reviewed the experience of the November data-taking period and could measure the positive improvements made for the site readiness. It also reviewed the policy under which Tier-2 are associated with Physics Groups. Such associations are decided twice per ye...

  18. COMPUTING

    CERN Multimedia

    M. Kasemann

    CCRC’08 challenges and CSA08 During the February campaign of the Common Computing readiness challenges (CCRC’08), the CMS computing team had achieved very good results. The link between the detector site and the Tier0 was tested by gradually increasing the number of parallel transfer streams well beyond the target. Tests covered the global robustness at the Tier0, processing a massive number of very large files and with a high writing speed to tapes.  Other tests covered the links between the different Tiers of the distributed infrastructure and the pre-staging and reprocessing capacity of the Tier1’s: response time, data transfer rate and success rate for Tape to Buffer staging of files kept exclusively on Tape were measured. In all cases, coordination with the sites was efficient and no serious problem was found. These successful preparations prepared the ground for the second phase of the CCRC’08 campaign, in May. The Computing Software and Analysis challen...

  19. Enhanced production of n-alkanes in Escherichia coli by spatial organization of biosynthetic pathway enzymes.

    Science.gov (United States)

    Rahmana, Ziaur; Sung, Bong Hyun; Yi, Ji-Yeun; Bui, Le Minh; Lee, Jun Hyoung; Kim, Sun Chang

    2014-12-20

    Alkanes chemically mimic hydrocarbons found in petroleum, and their demand as biofuels is steadily increasing. Biologically, n-alkanes are produced from fatty acyl-ACPs by acyl-ACP reductases (AARs) and aldehyde deformylating oxygenases (ADOs). One of the major impediments in n-alkane biosynthesis is the low catalytic turnover rates of ADOs. Here, we studied n-alkane biosynthesis in Escherichia coli using a chimeric ADO-AAR fusion protein or zinc finger protein-guided ADO/AAR assembly on DNA scaffolds to control their stoichiometric ratios and spatial arrangements. Bacterial production of n-alkanes with the ADO-AAR fusion protein was increased 4.8-fold (24 mg/L) over a control strain expressing ADO and AAR separately. Optimal n-alkane biosynthesis was achieved when the ADO:AAR binding site ratio on a DNA scaffold was 3:1, yielding an 8.8-fold increase (44 mg/L) over the control strain. Our findings indicate that the spatial organization of alkane-producing enzymes is critical for efficient n-alkane biosynthesis in E. coli.

  20. Comparative study of normal and branched alkane monolayer films adsorbed on a solid surface. II. Dynamics

    DEFF Research Database (Denmark)

    Enevoldsen, Ann Dorrit; Hansen, Flemming Yssing; Diama, A.;

    2007-01-01

    The dynamics of monolayer films of the n-alkane tetracosane (n-C24H52) and the branched alkane squalane (C30H62) adsorbed on graphite have been studied by quasielastic and inelastic neutron scattering and molecular dynamics (MD) simulations. Both molecules have 24 carbon atoms along their carbon...

  1. 40 CFR 721.2625 - Reaction product of alkane-diol and epichlorohydrin.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Reaction product of alkane-diol and epichlorohydrin. 721.2625 Section 721.2625 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED... Specific Chemical Substances § 721.2625 Reaction product of alkane-diol and epichlorohydrin. (a)...

  2. TOPOLOGY OF THE MEMBRANE-BOUND ALKANE HYDROXYLASE OF PSEUDOMONAS-OLEOVORANS

    NARCIS (Netherlands)

    van Beilen, J.B.; PENNINGA, D; Witholt, Bernard

    1992-01-01

    The Pseudomonas oleovorans alkane hydroxylase is an integral cytoplasmic membrane protein that is expressed and active in both Escherichia coli and P. oleovorans. Its primary sequence contains eight hydrophobic stretches that could span the membrane as alpha-helices. The topology of alkane hydroxyla

  3. Solid-Liquid equilibrium of n-alkanes using the Chain Delta Lattice Parameter model

    DEFF Research Database (Denmark)

    Coutinho, João A.P.; Andersen, Simon Ivar; Stenby, Erling Halfdan

    1996-01-01

    -liquid equilibrium of n-alkanes ranging from n-C_20 to n-C_40.The model is further modified to achieve a more correct temperature dependence because it severely underestimates the excess enthalpy. It is shown that the ratio of excess enthalpy and entropy for n-alkane solid solutions, as happens for other solid...

  4. Epitaxial nucleation and growth of n-alkane crystals on graphite

    NARCIS (Netherlands)

    Leunissen, M.E.; Graswinckel, W.S.; Enckevort, W.J.P. van; Vlieg, E.

    2004-01-01

    To study the heteroepitaxial growth of apolar organic compounds on apolar inorganic substrates, the n-alkanes dotriacontane (C32H66) and tritriacontane (C33H68), dissolved in n-heptane, were deposited onto the (0001) face of highly oriented pyrolytic graphite (HOPG). It was found that both n-alkanes

  5. Studies on the Physical Properties of Alkanes Using Edge-adjacency Information Topological Index

    Institute of Scientific and Technical Information of China (English)

    Cai Hua NI; Xian Yu ZENG; He HUANG

    2005-01-01

    Edge-adjacency index and information topological index for 82 molecules of alkanes have been constructed and calculated. The topological indices were used to correlate with seven physical properties of the alkanes. Some empirical equations were obtained through regression.The regression and calculation results show a good agreement of the topological indices and the properties.

  6. Comparative study of normal and branched alkane monolayer films adsorbed on a solid surface. I. Structure

    DEFF Research Database (Denmark)

    Enevoldsen, Ann Dorrit; Hansen, Flemming Yssing; Diama, A.

    2007-01-01

    The structure of a monolayer film of the branched alkane squalane (C30H62) adsorbed on graphite has been studied by neutron diffraction and molecular dynamics (MD) simulations and compared with a similar study of the n-alkane tetracosane (n-C24H52). Both molecules have 24 carbon atoms along their...

  7. Geologic seepage of methane and light alkanes in Los Angeles

    Science.gov (United States)

    Doezema, L. A.; Chang, K.; Baril, R.; Nwachuku, I.; Contreras, P.; Marquez, A.; Howard, D.

    2013-12-01

    Natural geologic seepage of methane from underground oil and natural gas reservoirs has been suggested to be an underreported part of the global methane budget. Other light alkanes are also given off in combination with the methane seepage, making it possible that geologic seepage is also a potentially significant global source of these light alkanes. This study reports C1-C5 findings from geologic seepage made in the Los Angeles region. Microseepage, invisible escape of gases, was measured primarily at Kenneth Hahn Regional Park, while macroseepage, the visible release of gases, was measured at the La Brea Tar Pits. Samples were collected using stainless steel canisters and flux chambers and were analyzed using gas chromatography with flame ionization detectors (GC-FID). Average microseepage flux rates of 0.95 μg m-2 h-1 for ethane and 0.51 μg m-2 h-1 were found for propane, while average macroseepage rates for methane, ethane, and propane were 664, 19.8, and 18.1 mg m-2 h-1 respectively. Relationships between microseepage flux rate and location of underground oil and natural deposit and earthquake fault lines are presented. Additionally, the relative importance of findings in context with global budgets and local air quality is discussed.

  8. Optimized reaction mechanism rate rules for ignition of normal alkanes

    KAUST Repository

    Cai, Liming

    2016-08-11

    The increasing demand for cleaner combustion and reduced greenhouse gas emissions motivates research on the combustion of hydrocarbon fuels and their surrogates. Accurate detailed chemical kinetic models are an important prerequisite for high fidelity reacting flow simulations capable of improving combustor design and operation. The development of such models for many new fuel components and/or surrogate molecules is greatly facilitated by the application of reaction classes and rate rules. Accurate and versatile rate rules are desirable to improve the predictive accuracy of kinetic models. A major contribution in the literature is the recent work by Bugler et al. (2015), which has significantly improved rate rules and thermochemical parameters used in kinetic modeling of alkanes. In the present study, it is demonstrated that rate rules can be used and consistently optimized for a set of normal alkanes including n-heptane, n-octane, n-nonane, n-decane, and n-undecane, thereby improving the predictive accuracy for all the considered fuels. A Bayesian framework is applied in the calibration of the rate rules. The optimized rate rules are subsequently applied to generate a mechanism for n-dodecane, which was not part of the training set for the optimized rate rules. The developed mechanism shows accurate predictions compared with published well-validated mechanisms for a wide range of conditions.

  9. Geomicrobiological linkages between short-chain alkane consumption and sulfate reduction rates in seep sediments.

    Science.gov (United States)

    Bose, Arpita; Rogers, Daniel R; Adams, Melissa M; Joye, Samantha B; Girguis, Peter R

    2013-01-01

    Marine hydrocarbon seeps are ecosystems that are rich in methane, and, in some cases, short-chain (C2-C5) and longer alkanes. C2-C4 alkanes such as ethane, propane, and butane can be significant components of seeping fluids. Some sulfate-reducing microbes oxidize short-chain alkanes anaerobically, and may play an important role in both the competition for sulfate and the local carbon budget. To better understand the anaerobic oxidation of short-chain n-alkanes coupled with sulfate-reduction, hydrocarbon-rich sediments from the Gulf of Mexico (GoM) were amended with artificial, sulfate-replete seawater and one of four n-alkanes (C1-C4) then incubated under strict anaerobic conditions. Measured rates of alkane oxidation and sulfate reduction closely follow stoichiometric predictions that assume the complete oxidation of alkanes to CO2 (though other sinks for alkane carbon likely exist). Changes in the δ(13)C of all the alkanes in the reactors show enrichment over the course of the incubation, with the C3 and C4 incubations showing the greatest enrichment (4.4 and 4.5‰, respectively). The concurrent depletion in the δ(13)C of dissolved inorganic carbon (DIC) implies a transfer of carbon from the alkane to the DIC pool (-3.5 and -6.7‰ for C3 and C4 incubations, respectively). Microbial community analyses reveal that certain members of the class Deltaproteobacteria are selectively enriched as the incubations degrade C1-C4 alkanes. Phylogenetic analyses indicate that distinct phylotypes are enriched in the ethane reactors, while phylotypes in the propane and butane reactors align with previously identified C3-C4 alkane-oxidizing sulfate-reducers. These data further constrain the potential influence of alkane oxidation on sulfate reduction rates (SRRs) in cold hydrocarbon-rich sediments, provide insight into their contribution to local carbon cycling, and illustrate the extent to which short-chain alkanes can serve as electron donors and govern microbial community

  10. Geomicrobiological linkages between short-chain alkane consumption and sulfate reduction rates in seep sediments.

    Directory of Open Access Journals (Sweden)

    Arpita eBose

    2013-12-01

    Full Text Available Marine hydrocarbon seeps are ecosystems that are rich in methane, and, in some cases, short-chain (C2-C5 and longer alkanes. C2-C4 alkanes such as ethane, propane and butane can be significant components of seeping fluids. Some sulfate-reducing microbes oxidize short-chain alkanes anaerobically, and may play an important role in both the competition for sulfate and the local carbon budget. To better understand the anaerobic oxidation of short-chain n-alkanes coupled with sulfate-reduction, hydrocarbon-rich sediments from the Gulf of Mexico were amended with artificial, sulfate-replete seawater and one of four n-alkanes (C1-C4 then incubated under strict anaerobic conditions. Measured rates of alkane oxidation and sulfate reduction closely follow stoichiometric predictions that assume the complete oxidation of alkanes to CO2 (though other sinks for alkane carbon likely exist. Changes in the δ13C of all the alkanes in the reactors show enrichment over the course of the incubation, with the C3 and C4 incubations showing the greatest enrichment (4.4‰ and 4.5‰ respectively. The concurrent depletion in the δ13C of dissolved inorganic carbon (DIC implies a transfer of carbon from the alkane to the DIC pool (-3.5 and -6.7‰ for C3 and C4 incubations, respectively. Microbial community analyses reveal that certain members of the class Deltaproteobacteria are selectively enriched as the incubations degrade C1-C4 alkanes. Phylogenetic analyses indicate that distinct phylotypes are enriched in the ethane reactors, while phylotypes in the propane and butane reactors align with previously identified C3-C4 alkane-oxidizing sulfate-reducers. These data further constrain the potential influence of alkane oxidation on sulfate reduction rates in cold hydrocarbon-rich sediments, provide insight into their contribution to local carbon cycling, and illustrate the extent to which short-chain alkanes can serve as electron donors and govern microbial community

  11. Carbon Isotopic Values of Individual N—Alkanes in Pyrolysates of Algae

    Institute of Scientific and Technical Information of China (English)

    周文; 吴庆余; 等

    2000-01-01

    This paper presents the carbon isotopic values of individual n-alkanes in pyrolysates of algae,which are widely spread in marine and lacustrine environments.The carbon isotopic values of n-alkanes originated from different algal precursors vary greatly,and those of n-alka nes orginated from C.protothecoides,S.sp PCC 6803 and I.Galbana are even heavier than from higher plants,n-alkanes with different carbon numers derived from the sme organism may stem from different biomacromolecules.The dominant product nC31 diene yielded at 300℃ or lower temperature also is different from n-alkanes yielded at the same thermal evolution phase with respect to their origin.The catalysis of mineral components in limestone may lead to a lighter carbon isotope composition of n-alkanes.

  12. The genome sequence of Desulfatibacillum alkenivorans AK-01: a blueprint for anaerobic alkane oxidation.

    Science.gov (United States)

    Callaghan, A V; Morris, B E L; Pereira, I A C; McInerney, M J; Austin, R N; Groves, J T; Kukor, J J; Suflita, J M; Young, L Y; Zylstra, G J; Wawrik, B

    2012-01-01

    Desulfatibacillum alkenivorans AK-01 serves as a model organism for anaerobic alkane biodegradation because of its distinctive biochemistry and metabolic versatility. The D. alkenivorans genome provides a blueprint for understanding the genetic systems involved in alkane metabolism including substrate activation, CoA ligation, carbon-skeleton rearrangement and decarboxylation. Genomic analysis suggested a route to regenerate the fumarate needed for alkane activation via methylmalonyl-CoA and predicted the capability for syntrophic alkane metabolism, which was experimentally verified. Pathways involved in the oxidation of alkanes, alcohols, organic acids and n-saturated fatty acids coupled to sulfate reduction and the ability to grow chemolithoautotrophically were predicted. A complement of genes for motility and oxygen detoxification suggests that D. alkenivorans may be physiologically adapted to a wide range of environmental conditions. The D. alkenivorans genome serves as a platform for further study of anaerobic, hydrocarbon-oxidizing microorganisms and their roles in bioremediation, energy recovery and global carbon cycling.

  13. Molecular simulation of the adsorption of linear alkane mixtures in pillared layered materials

    Institute of Scientific and Technical Information of China (English)

    LI Wen-zhuo; CHE Yu-liang; LIU Zi-yang; ZHANG Dan

    2007-01-01

    The adsorption isotherms of mixtures of linear alkanes, involving n-pentane, n-hexane, and n-heptane in pillared layered materials (PLMs) with three different porosities ψ=0.98, 0.94 and 0.87, and three pore widths H=1.02, 1.70 and 2.38 nm attemperature T=300 K were simulated by using configurational-bias Monte Carlo (CBMC) techniques in grand canonical ensemble. A grid model was employed to calculate the interaction between a fluid molecule and two layered boards here. For alkane mixtures, the n-heptane, the longest chain component in alkane mixtures, is preferentially adsorbed at low pressures, with its adsorption increasing and then decreasing as the pressure increases continuously while the n-pentane, the shortest chain component in alkane mixtures, is still adsorbed at high pressures; the adsorption of the longest chain component of alkane mixtures increases as the pore width and the porosity of PLMs increase.

  14. Co-metabolic conversion of toluene in anaerobic n-alkane-degrading bacteria.

    Science.gov (United States)

    Rabus, Ralf; Jarling, René; Lahme, Sven; Kühner, Simon; Heider, Johann; Widdel, Friedrich; Wilkes, Heinz

    2011-09-01

    Diverse microorganisms have been described to degrade petroleum hydrocarbons anaerobically. Strains able to utilize n-alkanes do not grow with aromatic hydrocarbons, whereas strains able to utilize aromatic hydrocarbons do not grow with n-alkanes. To investigate this specificity in more detail, three anaerobic n-alkane degraders (two denitrifying, one sulfate-reducing) and eight anaerobic alkylbenzene degraders (five denitrifying, three sulfate-reducing) were incubated with mixtures of n-alkanes and toluene. Whereas the toluene degradationers formed only the characteristic toluene-derived benzylsuccinate and benzoate, but no n-alkane-derived metabolites, the n-alkane degraders formed toluene-derived benzylsuccinate, 4-phenylbutanoate, phenylacetate and benzoate besides the regular n-alkane-derived (1-methylalkyl)succinates and methyl-branched alkanoates. The co-metabolic conversion of toluene by anaerobic n-alkane degraders to the level of benzoate obviously follows the anaerobic n-alkane degradation pathway with C-skeleton rearrangement and decarboxylation rather than the β-oxidation pathway of anaerobic toluene metabolism. Hence, petroleum-derived aromatic metabolites detectable in anoxic environments may not be exclusively formed by genuine alkylbenzene degraders. In addition, the hitherto largely unexplored fate of fumarate hydrogen during the activation reactions was examined with (2,3-(2) H(2) )fumarate as co-substrate. Deuterium was completely exchanged with hydrogen at the substituted carbon atom (C-2) of the succinate adducts of n-alkanes, whereas it is retained in toluene-derived benzylsuccinate, regardless of the type of enzyme catalysing the fumarate addition reaction.

  15. Genes involved in alkane degradation in the Alcanivorax hongdengensis strain A-11-3.

    Science.gov (United States)

    Wang, Wanpeng; Shao, Zongze

    2012-04-01

    Alcanivorax hongdengensis A-11-3 is a newly identified type strain isolated from the surface water of the Malacca and Singapore Straits that can degrade a wide range of alkanes. To understand the degradation mechanism of this strain, the genes encoding alkane hydroxylases were obtained by PCR screening and shotgun sequencing of a genomic fosmid library. Six genes involved in alkane degradation were found, including alkB1, alkB2, p450-1, p450-2, p450-3 and almA. Heterogeneous expression analysis confirmed their functions as alkane oxidases in Pseudomonas putida GPo12 (pGEc47ΔB) or Pseudomonas fluorescens KOB2Δ1. Q-PCR revealed that the transcription of alkB1 and alkB2 was enhanced in the presence of n-alkanes C(12) to C(24); three p450 genes were up-regulated by C(8)-C(16) n-alkanes at different levels, whereas enhanced expression of almA was observed when strain A-11-3 grew with long-chain alkanes (C(24) to C(36)). In the case of branched alkanes, pristane significantly enhanced the expression of alkB1, p450-3 and almA. The six genes enable strain A-11-3 to degrade short (C(8)) to long (C(36)) alkanes that are straight or branched. The ability of A. hongdengensis A-11-3 to thrive in oil-polluted marine environments may be due to this strain's multiple systems for alkane degradation and its range of substrates.

  16. n-Alkane distributions as palaeoclimatic proxies in ombrotrophic peat: The role of decomposition and dominant vegetation

    NARCIS (Netherlands)

    Schellekens, J.; Buurman, P.

    2011-01-01

    n-Alkane distributions are frequently used as palaeoclimate proxies in ombrotrophic peat deposits. Although n-alkane distributions differ strongly between plant species, n-alkanes are not species-specific molecules. For a proper interpretation, it is important to understand the different abundances

  17. 40 CFR 721.10178 - Distillates (Fischer-Tropsch), hydroisomerized middle, C10-13-branched alkane fraction.

    Science.gov (United States)

    2010-07-01

    ...), hydroisomerized middle, C10-13-branched alkane fraction. 721.10178 Section 721.10178 Protection of Environment...), hydroisomerized middle, C10-13-branched alkane fraction. (a) Chemical substance and significant new uses subject... middle, C10-13-branched alkane fraction (PMN P-04-319; CAS No. 642928-30-1) is subject to reporting...

  18. 40 CFR 721.10103 - Naphtha (Fischer-Tropsch), C4-11-alkane, branched and linear.

    Science.gov (United States)

    2010-07-01

    ...-alkane, branched and linear. 721.10103 Section 721.10103 Protection of Environment ENVIRONMENTAL... Significant New Uses for Specific Chemical Substances § 721.10103 Naphtha (Fischer-Tropsch), C4-11-alkane... substance identified as naphtha (fischer-tropsch), C4-11-alkane, branched and linear (PMN P-04-235; CAS...

  19. Draft Genome Sequence of Uncultivated Firmicutes (Peptococcaceae SCADC) Single Cells Sorted from Methanogenic Alkane-Degrading Cultures

    Science.gov (United States)

    Tan, BoonFei; Charchuk, Rhianna; Li, Carmen; Nesbø, Camilla; Abu Laban, Nidal

    2014-01-01

    The draft genome of an uncultivated bacterium affiliated with the Peptococcaceae was reconstructed by co-assembling Illumina MiSeq sequences from three single cells sorted by microfluidics from two methanogenic alkane-degrading cultures. Peptococcaceae SCADC (short-chain alkane-degrading culture) may be genetically capable of anaerobic alkane activation by fumarate addition in the absence of sulfate. PMID:25212628

  20. Tracing natural gas transport into shallow groundwater using dissolved nitrogen and alkane chemistry in Parker County, Texas

    Science.gov (United States)

    Larson, T.; Nicot, J. P.; Mickler, P. J.; Darvari, R.

    2015-12-01

    Dissolved methane in shallow groundwater drives public concern about the safety of hydraulic fracturing. We report dissolved alkane and nitrogen gas concentrations and their stable isotope values (δ13C and δ15N, respectively) from 208 water wells in Parker county, Texas. These data are used to differentiate 'stray' natural gas and low temperature microbial methane, and (2) estimate the ratio of stray gas to groundwater. The ratio of (gas-phase) stray natural gas to groundwater is estimated by correlating dissolved methane and nitrogen concentrations and dissolved nitrogen δ15N values. Our hypothesis is groundwater exposed to high volumes of stray natural gas have high dissolved methane concentrations and low dissolved nitrogen concentrations and δ15N values. Alternatively, groundwater exposed to low volumes of stray gas-phase natural gas have elevated dissolved methane, but the concentration of dissolved nitrogen and its d15N value is atmospheric. A cluster of samples in Parker county have high concentrations of dissolved methane (>10mg/L) with d13Cmethane and alkane ratios (C1/C2+C3) typical of natural gas from the Barnett Shale and the Strawn Formation. Coupling dissolved nitrogen concentrations and δ15N values with these results, we suggest that few of the wells in this cluster preserve large gas to water ratios. Many samples with high dissolved methane concentrations have atmospheric dissolved nitrogen concentrations and δ15N values, providing evidence against high flux natural gas transport into shallow groundwater. These results demonstrate that dissolved nitrogen chemistry, in addition to dissolved alkane and noble gas measurements, may be useful to discern sources of dissolved methane and estimate ratios of stray natural gas-water ratios.

  1. Organometallic model complexes elucidate the active gallium species in alkane dehydrogenation catalysts based on ligand effects in Ga K-edge XANES

    Energy Technology Data Exchange (ETDEWEB)

    Getsoian, Andrew “Bean”; Das, Ujjal; Camacho-Bunquin, Jeffrey; Zhang, Guanghui; Gallagher, James R.; Hu, Bo; Cheah, Singfoong; Schaidle, Joshua A.; Ruddy, Daniel A.; Hensley, Jesse E.; Krause, Theodore R.; Curtiss, Larry A.; Miller, Jeffrey T.; Hock, Adam S.

    2016-01-01

    Gallium-modified zeolites are known catalysts for the dehydrogenation of alkanes, reactivity that finds industrial application in the aromatization of light alkanes by Ga-ZSM5. While the role of gallium cations in alkane activation is well known, the oxidation state and coordination environment of gallium under reaction conditions has been the subject of debate. Edge shifts in Ga K-edge XANES spectra acquired under reaction conditions have long been interpreted as evidence for reduction of Ga(III) to Ga(I). However, a change in oxidation state is not the only factor that can give rise to a change in the XANES spectrum. In order to better understand the XANES spectra of working catalysts, we have synthesized a series of molecular model compounds and grafted surface organometallic Ga species and compared their XANES spectra to those of gallium-based catalysts acquired under reducing conditions. We demonstrate that changes in the identity and number of gallium nearest neighbors can give rise to changes in XANES spectra similar to those attributed in literature to changes in oxidation state. Specifically, spectral features previously attributed to Ga(I) may be equally well interpreted as evidence for low-coordinate Ga(III) alkyl or hydride species. These findings apply both to gallium-impregnated zeolite catalysts and to silica-supported single site gallium catalysts, the latter of which is found to be active and selective for dehydrogenation of propane and hydrogenation of propylene.

  2. COMPUTING

    CERN Multimedia

    I. Fisk

    2013-01-01

    Computing operation has been lower as the Run 1 samples are completing and smaller samples for upgrades and preparations are ramping up. Much of the computing activity is focusing on preparations for Run 2 and improvements in data access and flexibility of using resources. Operations Office Data processing was slow in the second half of 2013 with only the legacy re-reconstruction pass of 2011 data being processed at the sites.   Figure 1: MC production and processing was more in demand with a peak of over 750 Million GEN-SIM events in a single month.   Figure 2: The transfer system worked reliably and efficiently and transferred on average close to 520 TB per week with peaks at close to 1.2 PB.   Figure 3: The volume of data moved between CMS sites in the last six months   The tape utilisation was a focus for the operation teams with frequent deletion campaigns from deprecated 7 TeV MC GEN-SIM samples to INVALID datasets, which could be cleaned up...

  3. COMPUTING

    CERN Document Server

    I. Fisk

    2012-01-01

      Introduction Computing activity has been running at a sustained, high rate as we collect data at high luminosity, process simulation, and begin to process the parked data. The system is functional, though a number of improvements are planned during LS1. Many of the changes will impact users, we hope only in positive ways. We are trying to improve the distributed analysis tools as well as the ability to access more data samples more transparently.  Operations Office Figure 2: Number of events per month, for 2012 Since the June CMS Week, Computing Operations teams successfully completed data re-reconstruction passes and finished the CMSSW_53X MC campaign with over three billion events available in AOD format. Recorded data was successfully processed in parallel, exceeding 1.2 billion raw physics events per month for the first time in October 2012 due to the increase in data-parking rate. In parallel, large efforts were dedicated to WMAgent development and integrati...

  4. COMPUTING

    CERN Multimedia

    Matthias Kasemann

    Overview The main focus during the summer was to handle data coming from the detector and to perform Monte Carlo production. The lessons learned during the CCRC and CSA08 challenges in May were addressed by dedicated PADA campaigns lead by the Integration team. Big improvements were achieved in the stability and reliability of the CMS Tier1 and Tier2 centres by regular and systematic follow-up of faults and errors with the help of the Savannah bug tracking system. In preparation for data taking the roles of a Computing Run Coordinator and regular computing shifts monitoring the services and infrastructure as well as interfacing to the data operations tasks are being defined. The shift plan until the end of 2008 is being put together. User support worked on documentation and organized several training sessions. The ECoM task force delivered the report on “Use Cases for Start-up of pp Data-Taking” with recommendations and a set of tests to be performed for trigger rates much higher than the ...

  5. COMPUTING

    CERN Multimedia

    M. Kasemann

    Introduction A large fraction of the effort was focused during the last period into the preparation and monitoring of the February tests of Common VO Computing Readiness Challenge 08. CCRC08 is being run by the WLCG collaboration in two phases, between the centres and all experiments. The February test is dedicated to functionality tests, while the May challenge will consist of running at all centres and with full workflows. For this first period, a number of functionality checks of the computing power, data repositories and archives as well as network links are planned. This will help assess the reliability of the systems under a variety of loads, and identifying possible bottlenecks. Many tests are scheduled together with other VOs, allowing the full scale stress test. The data rates (writing, accessing and transfer¬ring) are being checked under a variety of loads and operating conditions, as well as the reliability and transfer rates of the links between Tier-0 and Tier-1s. In addition, the capa...

  6. COMPUTING

    CERN Multimedia

    Contributions from I. Fisk

    2012-01-01

    Introduction The start of the 2012 run has been busy for Computing. We have reconstructed, archived, and served a larger sample of new data than in 2011, and we are in the process of producing an even larger new sample of simulations at 8 TeV. The running conditions and system performance are largely what was anticipated in the plan, thanks to the hard work and preparation of many people. Heavy ions Heavy Ions has been actively analysing data and preparing for conferences.  Operations Office Figure 6: Transfers from all sites in the last 90 days For ICHEP and the Upgrade efforts, we needed to produce and process record amounts of MC samples while supporting the very successful data-taking. This was a large burden, especially on the team members. Nevertheless the last three months were very successful and the total output was phenomenal, thanks to our dedicated site admins who keep the sites operational and the computing project members who spend countless hours nursing the...

  7. COMPUTING

    CERN Multimedia

    P. MacBride

    The Computing Software and Analysis Challenge CSA07 has been the main focus of the Computing Project for the past few months. Activities began over the summer with the preparation of the Monte Carlo data sets for the challenge and tests of the new production system at the Tier-0 at CERN. The pre-challenge Monte Carlo production was done in several steps: physics generation, detector simulation, digitization, conversion to RAW format and the samples were run through the High Level Trigger (HLT). The data was then merged into three "Soups": Chowder (ALPGEN), Stew (Filtered Pythia) and Gumbo (Pythia). The challenge officially started when the first Chowder events were reconstructed on the Tier-0 on October 3rd. The data operations teams were very busy during the the challenge period. The MC production teams continued with signal production and processing while the Tier-0 and Tier-1 teams worked on splitting the Soups into Primary Data Sets (PDS), reconstruction and skimming. The storage sys...

  8. COMPUTING

    CERN Multimedia

    2010-01-01

    Introduction Just two months after the “LHC First Physics” event of 30th March, the analysis of the O(200) million 7 TeV collision events in CMS accumulated during the first 60 days is well under way. The consistency of the CMS computing model has been confirmed during these first weeks of data taking. This model is based on a hierarchy of use-cases deployed between the different tiers and, in particular, the distribution of RECO data to T1s, who then serve data on request to T2s, along a topology known as “fat tree”. Indeed, during this period this model was further extended by almost full “mesh” commissioning, meaning that RECO data were shipped to T2s whenever possible, enabling additional physics analyses compared with the “fat tree” model. Computing activities at the CMS Analysis Facility (CAF) have been marked by a good time response for a load almost evenly shared between ALCA (Alignment and Calibration tasks - highest p...

  9. Evidence of different thermoregulatory mechanisms between two sympatric Scarabaeus species using infrared thermography and micro-computer tomography.

    Directory of Open Access Journals (Sweden)

    José R Verdú

    Full Text Available In endotherms insects, the thermoregulatory mechanisms modulate heat transfer from the thorax to the abdomen to avoid overheating or cooling in order to obtain a prolonged flight performance. Scarabaeus sacer and S. cicatricosus, two sympatric species with the same habitat and food preferences, showed daily temporal segregation with S. cicatricosus being more active during warmer hours of the day in opposition to S. sacer who avoid it. In the case of S. sacer, their endothermy pattern suggested an adaptive capacity for thorax heat retention. In S. cicatricosus, an active 'heat exchanger' mechanism was suggested. However, no empirical evidence had been documented until now. Thermographic sequences recorded during flight performance showed evidence of the existence of both thermoregulatory mechanisms. In S. sacer, infrared sequences showed a possible heat insulator (passive thermal window, which prevents heat transfer from meso- and metathorax to the abdomen during flight. In S. cicatricosus, infrared sequences revealed clear and effective heat flow between the thorax and abdomen (abdominal heat transfer that should be considered the main mechanism of thermoregulation. This was related to a subsequent increase in abdominal pumping (as a cooling mechanism during flight. Computer microtomography scanning, anatomical dissections and internal air volume measurements showed two possible heat retention mechanisms for S. sacer; the abdominal air sacs and the development of the internal abdominal sternites that could explain the thermoregulation between thorax and abdomen. Our results suggest that interspecific interactions between sympatric species are regulated by very different mechanisms. These mechanisms create unique thermal niches for the different species, thereby preventing competition and modulating spatio-temporal distribution and the composition of dung beetle assemblages.

  10. COMPUTING

    CERN Multimedia

    I. Fisk

    2011-01-01

    Introduction The Computing Team successfully completed the storage, initial processing, and distribution for analysis of proton-proton data in 2011. There are still a variety of activities ongoing to support winter conference activities and preparations for 2012. Heavy ions The heavy-ion run for 2011 started in early November and has already demonstrated good machine performance and success of some of the more advanced workflows planned for 2011. Data collection will continue until early December. Facilities and Infrastructure Operations Operational and deployment support for WMAgent and WorkQueue+Request Manager components, routinely used in production by Data Operations, are provided. The GlideInWMS and components installation are now deployed at CERN, which is added to the GlideInWMS factory placed in the US. There has been new operational collaboration between the CERN team and the UCSD GlideIn factory operators, covering each others time zones by monitoring/debugging pilot jobs sent from the facto...

  11. Sclereids are strong enough to support the delicate corollas: experimental and computational data evidence from Camellia sinensis (L.)

    Science.gov (United States)

    Zhang, Wei; Xue, Yuanyuan; Yang, Shuo; Wang, Yangang; Zhao, Hong

    2017-01-01

    Sclereids are a fundamental cell type that widely exist in higher plants and are generally thought to have a mechanical function. However, the occurrence of sclereids in the ephemeral corolla has rarely been documented and their biological significance is poorly understood. In this study, flower buds from Camellia sinensis at various ontogenetic stages were sampled, cleared, sectioned, stained, and examined using light microscopy to ascertain the morphology and distribution of sclereids and their variation. In addition, Camellia japonica plants with distinctive floral structures were investigated and compared to explore whether sclereid occurrence is associated with floral form. In particular, a computational simulation using finite element analysis was undertaken to investigate how corollas, with and without sclereids, responded to wind and rain. The results showed that sclereids have some mechanical properties that are based on their shape and distribution, which make the soft corolla strong enough to protect the inner ovary. Thus, corolla sclereids may explain how the seemingly delicate corolla performs its protective function in response to environmental stresses. These findings provide further evidence for the hypothesis that flower traits exhibit adaptive responses to abiotic factors in addition to their traditionally recognized pollinator-mediated selection. PMID:28252101

  12. Characterization of a CYP153 alkane hydroxylase gene in a Gram-positive Dietzia sp. DQ12-45-1b and its "team role" with alkW1 in alkane degradation.

    Science.gov (United States)

    Nie, Yong; Liang, Jie-Liang; Fang, Hui; Tang, Yue-Qin; Wu, Xiao-Lei

    2014-01-01

    CYP153 and AlkB-like hydroxylases were recently discovered in Gram-positive alkane-degrading bacteria. However, it is unclear whether they cooperate with each other in alkane degradation as they do in Gram-negative bacteria. In this paper, we cloned the CYP153 gene from a representative Gram-positive alkane-degrading bacterium, Dietzia sp. DQ12-45-1b. The CYP153 gene transcription in Dietzia sp. DQ12-45-1b and heterologous expression in alkB gene knockout mutant strain Pseudomonas fluorescens KOB2∆1 both confirmed the functions of CYP153 on C6-C10 n-alkanes degradation, but not on longer chain-length n-alkanes. In addition, substrate-binding analysis of the purified CYP153 protein revealed different substrate affinities to C6-C16 n-alkanes, confirming n-alkanes binding to CYP153 protein. Along with AlkW1, an AlkB-like alkane hydroxylase in Dietzia sp. DQ12-45-1b, a teamwork pattern was found in n-alkane degradation, i.e. CYP153 was responsible for hydroxylating n-alkanes shorter than C10 while AlkW1 was responsible for those longer than C14. Further sequence analysis suggested that the high horizontal gene transfer (HGT) potential of CYP153 genes may be universal in Gram-positive alkane-degrading actinomycetes that contain both alkB and CYP153 genes.

  13. Involvement of an Alkane Hydroxylase System of Gordonia sp. Strain SoCg in Degradation of Solid n-Alkanes▿

    OpenAIRE

    2010-01-01

    Enzymes involved in oxidation of long-chain n-alkanes are still not well known, especially those in Gram-positive bacteria. This work describes the alkane degradation system of the n-alkane degrader actinobacterium Gordonia sp. strain SoCg, which is able to grow on n-alkanes from dodecane (C12) to hexatriacontane (C36) as the sole C source. SoCg harbors in its chromosome a single alk locus carrying six open reading frames (ORFs), which shows 78 to 79% identity with the alkane hydroxylase (AH)...

  14. COMPUTING

    CERN Multimedia

    M. Kasemann

    CMS relies on a well functioning, distributed computing infrastructure. The Site Availability Monitoring (SAM) and the Job Robot submission have been very instrumental for site commissioning in order to increase availability of more sites such that they are available to participate in CSA07 and are ready to be used for analysis. The commissioning process has been further developed, including "lessons learned" documentation via the CMS twiki. Recently the visualization, presentation and summarizing of SAM tests for sites has been redesigned, it is now developed by the central ARDA project of WLCG. Work to test the new gLite Workload Management System was performed; a 4 times increase in throughput with respect to LCG Resource Broker is observed. CMS has designed and launched a new-generation traffic load generator called "LoadTest" to commission and to keep exercised all data transfer routes in the CMS PhE-DEx topology. Since mid-February, a transfer volume of about 12 P...

  15. Isolation and characterization of a novel n-alkane-degrading strain, Acinetobacter haemolyticus AR-46

    Energy Technology Data Exchange (ETDEWEB)

    Bihari, Z.; Balazs, M.; Bartos, P.; Kesserue, P.; Kiss, I.; Mecs, I. [Bay Zoltan Foundation for Applied Research, Szeged (Hungary). Inst. for Biotechnology; Pettko-Szandtner, A. [Hungarian Academy of Sciences, Szeged (Hungary). Inst. of Plant Biology; Csanadi, G. [Szeged Univ. (Hungary). Dept. of Biotechnology

    2007-03-15

    Strain AR-46, isolated and identified as Acinetobacter haemolyticus, evolutionally distant from the known hydrocarbon-degrading Acinetobacter spp., proved to have excellent long-chain n-alkane-degrading ability. This is the first detailed report on an n-alkane-utilizing strain belonging to this species. The preferred substrate is n-hexadecane, with an optimal temperature of 37 C under aerobic conditions. Five complete and two partial open reading frames were sequenced and correlated with the early steps of monoterminal oxidation-initiated n-alkane mineralization. The encoded protein sequences and the arrangement of these genes displayed high similarity to those found in Acinetobacter sp. M-1, but AR-46 seemed to have only one alkane hydroxylase gene, with a completely different induction profile. Unique behaviour was also observed in n-alkane bioavailability. Substrate uptake occurred through the hydrophobic surface of n-alkane droplet-adhered cells possessing long, thick fimbriae, which were presumed to play a major role in n-alkane solubilization. A majority of the cells was in detached form, with thick, but short fimbriae. These free cells were permanently hydrophilic, unlike the cells of other Acinetobacter strains. (orig.)

  16. Chain length dependence of the thermodynamic properties of linear and cyclic alkanes and polymers.

    Science.gov (United States)

    Huang, Dinghai; Simon, Sindee L; McKenna, Gregory B

    2005-02-22

    The specific heat capacity was measured with step-scan differential scanning calorimetry for linear alkanes from pentane (C(5)H(12)) to nonadecane (C(19)H(40)), for several cyclic alkanes, for linear and cyclic polyethylenes, and for a linear and a cyclic polystyrene. For the linear alkanes, the specific heat capacity in the equilibrium liquid state decreases as chain length increases; above a carbon number N of 10 (decane) the specific heat asymptotes to a constant value. For the cyclic alkanes, the heat capacity in the equilibrium liquid state is lower than that of the corresponding linear chains and increases with increasing chain length. At high enough molecular weights, the heat capacities of cyclic and linear molecules are expected to be equal, and this is found to be the case for the polyethylenes and polystyrenes studied. In addition, the thermal properties of the solid-liquid and the solid-solid transitions are examined for the linear and cyclic alkanes; solid-solid transitions are observed only in the odd-numbered alkanes. The thermal expansion coefficients and the specific volumes of the linear and cyclic alkanes are also calculated from literature data and compared with the trends in the specific heats.

  17. Communication: Stiffening of dilute alcohol and alkane mixtures with water

    Science.gov (United States)

    Ashbaugh, Henry S.; Wesley Barnett, J.; Saltzman, Alexander; Langrehr, Mae E.; Houser, Hayden

    2016-11-01

    We probe the anomalous compressibilities of dilute mixtures of alcohols and alkane gases in water using molecular simulations. The response to increasing solute concentration depends sensitively on temperature, with the compressibility decreasing upon solute addition at low temperatures and increasing at elevated temperatures. The thermodynamic origin of stiffening is directly tied to the solute's partial compressibility, which is negative at low temperatures and rises above water's compressibility with increasing temperature. Hydration shell waters concurrently tilt towards clathrate-like structures at low temperatures that fade with heating. Kirkwood-Buff theory traces the solute's partial compressibility to changes in the solute-water association volume upon heating and incongruous packing of waters at the boundary between the more structured hydration shell and bulk water.

  18. Hydrogen isotope exchange between n-alkanes and water under hydrothermal conditions

    Science.gov (United States)

    Reeves, Eoghan P.; Seewald, Jeffrey S.; Sylva, Sean P.

    2012-01-01

    To investigate the extent of hydrogen isotope (2H and 1H) exchange between hydrocarbons and water under hydrothermal conditions, we performed experiments heating C1-C5n-alkanes in aqueous solutions of varying initial 2H/1H ratios in the presence of a pyrite-pyrrhotite-magnetite redox buffer at 323 °C and 35-36 MPa. Extensive and reversible incorporation of water-derived hydrogen into C2-C5n-alkanes was observed on timescales of months. In contrast, comparatively minor exchange was observed for CH4. Isotopic exchange is facilitated by reversible equilibration of n-alkanes and their corresponding n-alkenes with H2 derived from the disproportionation of water. Rates of δ2H variation in C3+n-alkanes decreased with time, a trend that is consistent with an asymptotic approach to steady state isotopic compositions regulated by alkane-water isotopic equilibrium. Substantially slower δ2H variation was observed for ethane relative to C3-C5n-alkanes, suggesting that the greater stability of C3+ alkenes and isomerization reactions may dramatically enhance rates of 2H/1H exchange in C3+n-alkanes. Thus, in reducing aqueous environments, reversible reaction of alkanes and their corresponding alkenes facilitates rapid 2H/1H exchange between water and alkyl-bound hydrogen on relatively short geological timescales at elevated temperatures and pressures. The proximity of some thermogenic and purported abiogenic alkane δ2H values to those predicted for equilibrium 2H/1H fractionation with ambient water suggests that this process may regulate the δ2H signatures of some naturally occurring hydrocarbons.

  19. n-alkane profiles of engine lubricating oil and particulate matter by molecular sieve extraction.

    Science.gov (United States)

    Caravaggio, Gianni A; Charland, Jean-Pierre; Macdonald, Penny; Graham, Lisa

    2007-05-15

    As part of the Canadian Atmospheric Fine Particle Research Program to obtain reliable primary source emission profiles, a molecular sieve method was developed to reliably determine n-alkanes in lubricating oils, vehicle emissions, and mobile source dominated ambient particulate matter (PM). This work was also initiated to better calculate carbon preference index values (CPI: the ratio of the sums of odd over even n-alkanes), a parameter for estimating anthropogenic versus biogenic contributions in PM. n-Alkanes in lubricating oil and mobile source dominated PM are difficult to identify and quantify by gas chromatography due to the presence of similar components that cannot be fully resolved. This results in a hump, the unresolved complex mixture (UCM) that leads to incorrect n-alkane concentrations and CPI values. The sieve method yielded better chromatography, unambiguous identification of n-alkanes and allowed examination of differences between n-alkane profiles in light (LDV) and heavy duty vehicle (HDV) lubricating oils that would have been otherwise difficult. These profile differences made it possible to relate the LDV profile to that of the PM samples collected during a tunnel study in August 2001 near Vancouver (British Columbia, Canada). The n-alkane PM data revealed that longer sampling times result in a negative artifact, i.e., the desorption of the more volatile n-alkanes from the filters. Furthermore, the sieve procedure yielded n-alkane data that allowed calculation of accurate CPI values for lubricating oils and PM samples. Finally, this method may prove helpful in estimating the respective diesel and gasoline contributions to ambient PM.

  20. Biodegradation of variable-chain-length alkanes at low temperatures by a psychrotrophic Rhodococcus sp.

    Energy Technology Data Exchange (ETDEWEB)

    Whyte, L.G.; Hawari, J.; Zhou, E.; Bourbonniere, L.; Greer, C.W. [NRC-Biotechnology Research Inst., Montreal, Quebec (Canada); Inniss, W.E. [Univ. of Waterloo, Ontario (Canada). Dept. of Biology

    1998-07-01

    The psychrotroph Rhodococcus sp. strain Q15 was examined for its ability to degrade individual n-alkanes and diesel fuel at low temperatures, and its alkane catabolic pathway was investigated by biochemical and genetic techniques. At 0 and 5 C, Q15 mineralized the short-chain alkanes dodecane and hexadecane to a greater extent than that observed for the long-chain alkanes octacosane and dotriacontane. Q15 utilized a broad range of aliphatics (C{sub 10} to C{sub 21} alkanes, branched alkanes, and a substituted cyclohexane) present in diesel fuel at 5 C. Mineralization of hexadecane at 5 C was significantly greater in both hydrocarbon-contaminated and pristine soil microcosms seeded with Q15 cells than in uninoculated control soil microcosms. The detection of hexadecane and dodecane metabolic intermediates (1-hexadecanol and 2-hexadecanol and 1-do-decanol and 2-dodecanone, respectively) by solid-phase microextraction-gas chromatography-mass spectrometry and the utilization of potential metabolic intermediates indicated that Q15 oxidizes alkanes by both the terminal oxidation pathway and the subterminal oxidation pathway. Genetic characterization by PCR and nucleotide sequence analysis indicated that Q15 possesses an aliphatic aldehyde dehydrogenase gene highly homologous to the Rhodococcus erythropolis thcA gene. Rhodococcus sp. strain Q15 possessed two large plasmids of approximately 90 and 115 kb (shown to mediate Cd resistance) which were not required for alkane mineralization, although the 90-kb plasmid enhanced mineralization of some alkanes and growth on diesel oil at both 5 and 25 C.

  1. Gene cloning and functional analysis of triple alkane monooxygenases from Geobacillus thermoleovorans B23

    OpenAIRE

    2014-01-01

    An extremely thermophilic bacterium, Geobacillus thermoleovorans B23 which was isolated from a deep subterranean oil reservoir at Niigata, Japan, is capable of degrading broad range alkanes (C11-C32) at 70℃ by terminal oxidation pathway, followed by β-oxidation pathway. Whole genome sequence analysis revealed that B23 did not have alkB-type alkane monooxygenases genes like most alkane degrading bacteria but it carried three gene homologs namely ladAαB23, ladAβB23 and ladBB23 on its chromosome...

  2. Characterization of the medium- and long-chain n-alkanes degrading Pseudomonas aeruginosa strain SJTD-1 and its alkane hydroxylase genes.

    Science.gov (United States)

    Liu, Huan; Xu, Jing; Liang, Rubing; Liu, Jianhua

    2014-01-01

    A gram-negative aliphatic hydrocarbon-degrading bacterium SJTD-1 isolated from oil-contaminated soil was identified as Pseudomonas aeruginosa by comparative analyses of the 16S rRNA sequence, phenotype, and physiological features. SJTD-1 could efficiently mineralize medium- and long-chain n-alkanes (C12-C30) as its sole carbon source within seven days, showing the most optimal growth on n-hexadecane, followed by n-octadecane, and n-eicosane. In 36 h, 500 mg/L of tetradecane, hexadecane, and octadecane were transformed completely; and 2 g/L n-hexadecane was degraded to undetectable levels within 72 h. Two putative alkane-degrading genes (gene 3623 and gene 4712) were characterized and our results indicated that their gene products were rate-limiting enzymes involved in the synergetic catabolism of C12-C16 alkanes. On the basis of bioinformatics and transcriptional analysis, two P450 monooxygenases, along with a putative AlmA-like oxygenase, were examined. Genetically defective mutants lacking the characteristic alkane hydroxylase failed to degrade n-octadecane, thereby suggesting a different catalytic mechanism for the microbial transformation of alkanes with chain lengths over C18.

  3. Light alkane conversion processes - Suprabiotic catalyst systems for selective oxidation of light alkane gases to fuel oxygenates

    Energy Technology Data Exchange (ETDEWEB)

    Lyons, J.E.

    1992-01-01

    The objective of the work presented in this paper is to develop new, efficient catalysts for the selective transformation of the light alkanes in natural gas to alcohols for use as liquid transportation fuels, fuel precursors and chemical products. There currently exists no DIRECT one-step catalytic air-oxidation process to convert these substrates to alcohols. Such a one-step route would represent superior useful technology for the utilization of natural gas and similar refinery-derived light hydrocarbon streams. Processes for converting natural gas or its components (methane, ethane, propane, and the butanes) to alcohols for use as motor fuels, fuel additives or fuel precursors will not only add a valuable alternative to crude oil but will produce a clean-burning, high octane alternative to conventional gasoline.

  4. Light alkane conversion processes - Suprabiotic catalyst systems for selective oxidation of light alkane gases to fuel oxygenates.

    Energy Technology Data Exchange (ETDEWEB)

    Lyons, J.E.

    1992-07-01

    The objective of the work presented in this paper is to develop new, efficient catalysts for the selective transformation of the light alkanes in natural gas to alcohols for use as liquid transportation fuels, fuel precursors and chemical products. There currently exists no DIRECT one-step catalytic air-oxidation process to convert these substrates to alcohols. Such a one-step route would represent superior useful technology for the utilization of natural gas and similar refinery-derived light hydrocarbon streams. Processes for converting natural gas or its components (methane, ethane, propane, and the butanes) to alcohols for use as motor fuels, fuel additives or fuel precursors will not only add a valuable alternative to crude oil but will produce a clean-burning, high octane alternative to conventional gasoline.

  5. The Effects of Home Computers on Educational Outcomes: Evidence from a Field Experiment with Community College Students

    OpenAIRE

    Robert W. Fairlie; Rebecca A. London

    2013-01-01

    There is no clear theoretical prediction regarding whether home computers are an important input in the educational production function. To investigate the hypothesis that access to a home computer affects educational outcomes, we conduct the first-ever field experiment involving the provision of free computers to students for home use. Financial aid students attending a large community college in Northern California were randomly selected to receive free computers and were followed for two y...

  6. The Effects of Home Computers on Educational Outcomes: Evidence from a Field Experiment with Community College Students

    OpenAIRE

    Fairlie, Robert

    2014-01-01

    There is no clear theoretical prediction regarding whether home computers are an important input in the educational production function.  To investigate the hypothesis that access to a home computer affects educational outcomes, we conduct the first-ever field experiment involving the provision of free computers to students for home use.  Financial aid students attending a large community college in Northern California were randomly selected to receive free computers and were followed for two...

  7. Climate variability recorded by n-alkanes of paleolake sediment in Qaidam Basin on the northeast Tibetan Plateau in late MIS3

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Here we combine n-alkanes preserved in a shell bar section from Qarhan paleolake, Qaidam Basin with the other sedimentary proxies to elucidate the lake evolution process during the period 39.7 to 17.5 14C ka BP (calibrated age ranges from 43.5 to 22.4 cal. ka BP). In different stages, the n-alkane homologues exhibited different distribution modes indicative of variations in the surrounding vegetation and the hydrologic condition of the lake. The n-alkanes proxies (CPIh, ACLh, Paq) have the same trends as the summer solar insolation variation, implying that the summer insolation is the most important climatic factor driving the environmental changes and also indirectly controls lake evolution on the Tibetan Plateau. CPIh and ACLh as well as the total pollen concentration appear to show a trend comparable with methane concentration record from the GRIP ice core that reflected the Dansgaard-Oeschger events. This demonstrates that the paleoclimate variations in Qarhan area generally agree with global climate change and show rapid oscillations in late MIS3. These findings provide the latest molecular fossil evidence from paleolake sediments to confirm that lake evolution on Tibetan Plateau in late MIS3 was closely associated with enhanced summer insolation.

  8. Experimental proof for resonant diffusion of normal alkanes in LTL and ZSM-12 zeolites

    CERN Document Server

    Yoo, K; Smirniotis, P G

    2015-01-01

    The intra-crystalline diffusion of normal alkanes in LTL and ZSM-12 zeolite was experimentally studied via gravimetric measurements performed at different temperatures. A periodic dependence of the diffusion coefficient on the number of carbon atoms in alkane was detected, which is an experimental proof for resonant diffusion. The present observations were described on the base of the existing theory of the resonant diffusion and several important parameters of the alkane-zeolite interaction and zeolite vibrations were obtained. In the considered temperature region the diffusion coefficient follows the Arrhenius law with periodic dependences of the pre-exponential factor and activation energy on the number of carbon atoms in alkanes. A compensation effect of simultaneous increases of the pre-exponential factor and the activation energy was also established.

  9. Hydrothermal conversion of cellulose to alkanes with in-situ hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Sudong; Tan, Zhongchao [Department of Mechanical and Mechatronics Engineering, University of Waterloo (Canada)], Email: tanz@uwaterloo.ca

    2011-07-01

    A recently study examined the probability of hydrothermal conversion of cellulose to alkanes with in-situ H2 instead of external H2. This paper discusses the results of that study. The study researched the effects of volumetric ratios of initial input water to the reactor (W/R) and of selected catalysts on the alkane yields and composition. It was found that with the proper W/R ratios, the reforming of steam in the steam gas phase would automatically produce in-situ H2 and the key was to maintain the right balance of steam phase and liquid phase in the reactor. All the study results conclude that direct hydrothermal conversion of cellulose to alkanes with in-situ H2 is technically feasible. In addition, the application of this technology would protect the alkane bio-oil production biomass from the impact of unstable external supply of H2.

  10. Photocatalytic acceptorless alkane dehydrogenation: scope, mechanism, and conquering deactivation with carbon dioxide.

    Science.gov (United States)

    Chowdhury, Abhishek Dutta; Julis, Jennifer; Grabow, Kathleen; Hannebauer, Bernd; Bentrup, Ursula; Adam, Martin; Franke, Robert; Jackstell, Ralf; Beller, Matthias

    2015-01-01

    Alkane dehydrogenation is of special interest for basic science but also offers interesting opportunities for industry. The existing dehydrogenation methodologies make use of heterogeneous catalysts, which suffer from harsh reaction conditions and a lack of selectivity, whereas homogeneous methodologies rely mostly on unsolicited waste generation from hydrogen acceptors. Conversely, acceptorless photochemical alkane dehydrogenation in the presence of trans-Rh(PMe3 )2 (CO)Cl can be regarded as a more benign and atom efficient alternative. However, this methodology suffers from catalyst deactivation over time. Herein, we provide a detailed investigation of the trans-Rh(PMe3 )2 (CO)Cl-photocatalyzed alkane dehydrogenation using spectroscopic and theoretical investigations. These studies inspired us to utilize CO2 to prevent catalyst deactivation, which leads eventually to improved catalyst turnover numbers in the dehydrogenation of alkanes that include liquid organic hydrogen carriers.

  11. Alkane oxidation with porphyrins and metal complexes thereof having haloalkyl side chains

    Science.gov (United States)

    Wijesekera, Tilak; Lyons, James E.; Ellis, Jr., Paul E.; Bhinde, Manoj V.

    1998-01-01

    Transition metal complexes of meso-haloalkylporphyrins, wherein the haloalkyl groups contain 2 to 8 carbon atoms have been found to be highly effective catalysts for oxidation of alkanes and for the decomposition of hydroperoxides.

  12. Liquid alkanes with targeted molecular weights from biomass-derived carbohydrates.

    Science.gov (United States)

    West, Ryan M; Liu, Zhen Y; Peter, Maximilian; Dumesic, James A

    2008-01-01

    Liquid transportation fuels must burn cleanly and have high energy densities, criteria that are currently fulfilled by petroleum, a non-renewable resource, the combustion of which leads to increasing levels of atmospheric CO(2). An attractive approach for the production of transportation fuels from renewable biomass resources is to convert carbohydrates into alkanes with targeted molecular weights, such as C(8)-C(15) for jet-fuel applications. Targeted n-alkanes can be produced directly from fructose by an integrated process involving first the dehydration of this C(6) sugar to form 5-hydroxymethylfurfural, followed by controlled formation of C-C bonds with acetone to form C(9) and C(15) compounds, and completed by hydrogenation and hydrodeoxygenation reactions to form the corresponding n-alkanes. Analogous reactions are demonstrated starting with 5-methylfurfural or 2-furaldehyde, with the latter leading to C(8) and C(13) n-alkanes.

  13. Recent Results on Fast Flow Gas-Phase Partial Oxidation of Lower Alkanes

    Institute of Scientific and Technical Information of China (English)

    Vladimir S. Arutyunov

    2004-01-01

    Recent experimental results and kinetic modeling of fast flow gas-phase oxidation of methane and other lower alkanes to methanol and other oxygenates are discussed, alongside with prospects and possible areas for applications of the processes.

  14. Assessment of the GECKO-A modeling tool using chamber observations for C12 alkanes

    Science.gov (United States)

    Aumont, B.; La, S.; Ouzebidour, F.; Valorso, R.; Mouchel-Vallon, C.; Camredon, M.; Lee-Taylor, J. M.; Hodzic, A.; Madronich, S.; Yee, L. D.; Loza, C. L.; Craven, J. S.; Zhang, X.; Seinfeld, J.

    2013-12-01

    Secondary Organic Aerosol (SOA) production and ageing is the result of atmospheric oxidation processes leading to the progressive formation of organic species with higher oxidation state and lower volatility. Explicit chemical mechanisms reflect our understanding of these multigenerational oxidation steps. Major uncertainties remain concerning the processes leading to SOA formation and the development, assessment and improvement of such explicit schemes is therefore a key issue. The development of explicit mechanism to describe the oxidation of long chain hydrocarbons is however a challenge. Indeed, explicit oxidation schemes involve a large number of reactions and secondary organic species, far exceeding the size of chemical schemes that can be written manually. The chemical mechanism generator GECKO-A (Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere) is a computer program designed to overcome this difficulty. GECKO-A generates gas phase oxidation schemes according to a prescribed protocol assigning reaction pathways and kinetics data on the basis of experimental data and structure-activity relationships. In this study, we examine the ability of the generated schemes to explain SOA formation observed in the Caltech Environmental Chambers from various C12 alkane isomers and under high NOx and low NOx conditions. First results show that the model overestimates both the SOA yields and the O/C ratios. Various sensitivity tests are performed to explore processes that might be responsible for these disagreements.

  15. Emulsification of crude oil by an alkane-oxidizing Rhodococcus species isolated from seawater

    Energy Technology Data Exchange (ETDEWEB)

    Bredholt, H.; Bruheim, P.; Eimhjellen, K. [Norwegian Univ. of Scince and Technology, Trondheim (Norway); Josefsen, K.; Vatland, A. [SINTEF SI, Oslo (Norway). Industrial Chemistry Div.

    1998-04-01

    A Rhodococcus species, which has proven to be the best of 99 oil-emulsifying bacteria isolated from seawater, was characterized. This bacterium produced very stable oil-in-water emulsions from different crude oils with various content of aliphatic and aromatic compounds, by utilizing C{sub 1}1 and C{sub 3}3 n-alkanes as carbon and energy sources. Bacteria that produce stable emulsions are often able to adhere strongly to hydrocarbons or hydrophobic surfaces. It was at these surfaces that extensive emulsification of the residual oil and accumulation of acidic oxidation products occurred. The acidic products were consumed in a second step. This step was characterized by linear growth and an increasing number of cells growing in the water phase. The most extensive emulsification occurred at the end of the exponential phase. There was no evidence of surfactants at the end of the exponential phase, however, a polymeric compound with emulsifying activity, tightly bound to the oil droplets, was isolated, suggesting that the emulsification resulted from the release of the hydrophobic cell surface discarded during growth limitations. 38 refs., 7 figs.

  16. Biodegradation of variable-chain-length n-alkanes in Rhodococcus opacus R7 and the involvement of an alkane hydroxylase system in the metabolism.

    Science.gov (United States)

    Zampolli, Jessica; Collina, Elena; Lasagni, Marina; Di Gennaro, Patrizia

    2014-01-01

    Rhodococcus opacus R7 is a Gram-positive bacterium isolated from a polycyclic aromatic hydrocarbon contaminated soil for its versatile metabolism; indeed the strain is able to grow on naphthalene, o-xylene, and several long- and medium-chain n-alkanes. In this work we determined the degradation of n-alkanes in Rhodococcus opacus R7 in presence of n-dodecane (C12), n-hexadecane (C16), n-eicosane (C20), n-tetracosane (C24) and the metabolic pathway in presence of C12. The consumption rate of C12 was 88%, of C16 was 69%, of C20 was 51% and of C24 it was 78%. The decrement of the degradation rate seems to be correlated to the length of the aliphatic chain of these hydrocarbons. On the basis of the metabolic intermediates determined by the R7 growth on C12, our data indicated that R. opacus R7 metabolizes medium-chain n-alkanes by the primary alcohol formation. This represents a difference in comparison with other Rhodococcus strains, in which a mixture of the two alcohols was observed. By GC-MSD analysis we also identified the monocarboxylic acid, confirming the terminal oxidation. Moreover, the alkB gene cluster from R. opacus R7 was isolated and its involvement in the n-alkane degradation system was investigated by the cloning of this genomic region into a shuttle-vector E. coli-Rhodococcus to evaluate the alkane hydroxylase activity. Our results showed an increased biodegradation of C12 in the recombinant strain R. erythropolis AP (pTipQT1-alkR7) in comparison with the wild type strain R. erythropolis AP. These data supported the involvement of the alkB gene cluster in the n-alkane degradation in the R7 strain.

  17. Regulation of the Alkane Hydroxylase CYP153 Gene in a Gram-Positive Alkane-Degrading Bacterium, Dietzia sp. Strain DQ12-45-1b.

    Science.gov (United States)

    Liang, Jie-Liang; JiangYang, Jing-Hong; Nie, Yong; Wu, Xiao-Lei

    2015-11-13

    CYP153, one of the most common medium-chain n-alkane hydroxylases belonging to the cytochrome P450 superfamily, is widely expressed in n-alkane-degrading bacteria. CYP153 is also thought to cooperate with AlkB in degrading various n-alkanes. However, the mechanisms regulating the expression of the protein remain largely unknown. In this paper, we studied CYP153 gene transcription regulation by the potential AraC family regulator (CypR) located upstream of the CYP153 gene cluster in a broad-spectrum n-alkane-degrading Gram-positive bacterium, Dietzia sp. strain DQ12-45-1b. We first identified the transcriptional start site and the promoter of the CYP153 gene cluster. Sequence alignment of upstream regions of CYP153 gene clusters revealed high conservation in the -10 and -35 regions in Actinobacteria. Further analysis of the β-galactosidase activity in the CYP153 gene promoter-lacZ fusion cell indicated that the CYP153 gene promoter was induced by n-alkanes comprised of 8 to 14 carbon atoms, but not by derived decanol and decanic acid. Moreover, we constructed a cypR mutant strain and found that the CYP153 gene promoter activities and CYP153 gene transcriptional levels in the mutant strain were depressed compared with those in the wild-type strain in the presence of n-alkanes, suggesting that CypR served as an activator for the CYP153 gene promoter. By comparing CYP153 gene arrangements in Actinobacteria and Proteobacteria, we found that the AraC family regulator is ubiquitously located upstream of the CYP153 gene, suggesting its universal regulatory role in CYP153 gene transcription. We further hypothesize that the observed mode of CYP153 gene regulation is shared by many Actinobacteria.

  18. Simulated Effects of Odd-Alkane Impurities in a Hexane Monolayer on Graphite

    OpenAIRE

    Pint, Cary L.; Roth, Michael W.

    2005-01-01

    We present the results of molecular dynamics simulations of odd alkane impurities present within the hexane (even alkane) monolayer. We simulate various temperatures at ca. 3%, 5%, 10%, and 15% impurities of propane, pentane, heptane, nonane, and undecane, each having a low-temperature solid phase belonging to a different space group as compared to hexane, to study the effects of impurities on the various phases and phase transitions for hexane monolayers that are well-characterized through p...

  19. The fatty acids and alkanes of Satureja adamovicii Silic and Satureja fukarekii Silic (NOTE

    Directory of Open Access Journals (Sweden)

    DUSANKA KITIC

    1999-05-01

    Full Text Available The content and composition of fatty acids and alkanes of Satureja adamovicii Silic and Satureja fukarekii Silic were analized by GC. It was found that unsaturated acids prevailed and that the major components were palmitic, oleic, linoleic and linolenic acids. The hydrocarbon fractions of pentane extracts were shown to consist of the alkane homologues (C17 to C34 with nonacosane and hentriacontane being prevailing compounds.

  20. The quantitative significance of Syntrophaceae and syntrophic partnerships in methanogenic degradation of crude oil alkanes.

    Science.gov (United States)

    Gray, N D; Sherry, A; Grant, R J; Rowan, A K; Hubert, C R J; Callbeck, C M; Aitken, C M; Jones, D M; Adams, J J; Larter, S R; Head, I M

    2011-11-01

    Libraries of 16S rRNA genes cloned from methanogenic oil degrading microcosms amended with North Sea crude oil and inoculated with estuarine sediment indicated that bacteria from the genera Smithella (Deltaproteobacteria, Syntrophaceace) and Marinobacter sp. (Gammaproteobacteria) were enriched during degradation. Growth yields and doubling times (36 days for both Smithella and Marinobacter) were determined using qPCR and quantitative data on alkanes, which were the predominant hydrocarbons degraded. The growth yield of the Smithella sp. [0.020 g(cell-C)/g(alkane-C)], assuming it utilized all alkanes removed was consistent with yields of bacteria that degrade hydrocarbons and other organic compounds in methanogenic consortia. Over 450 days of incubation predominance and exponential growth of Smithella was coincident with alkane removal and exponential accumulation of methane. This growth is consistent with Smithella's occurrence in near surface anoxic hydrocarbon degrading systems and their complete oxidation of crude oil alkanes to acetate and/or hydrogen in syntrophic partnership with methanogens in such systems. The calculated growth yield of the Marinobacter sp., assuming it grew on alkanes, was [0.0005 g(cell-C)/g(alkane-C)] suggesting that it played a minor role in alkane degradation. The dominant methanogens were hydrogenotrophs (Methanocalculus spp. from the Methanomicrobiales). Enrichment of hydrogen-oxidizing methanogens relative to acetoclastic methanogens was consistent with syntrophic acetate oxidation measured in methanogenic crude oil degrading enrichment cultures. qPCR of the Methanomicrobiales indicated growth characteristics consistent with measured rates of methane production and growth in partnership with Smithella.

  1. Vapour Liquid Equilibrium in Asymmetric Mixtures of n-Alkanes with Ethane

    OpenAIRE

    Duta, Anca

    2002-01-01

    The paper presents a vapour liquid equilibria study in binary mixtures of n-alkanes with high dimensional asymmetry. Each mixture contains ethane and alkanes higher than eicosane. Calculations were done using two equations of state, Peng-Robinson (PR) and Soave (SRK), in combination with van der Waals mixing rules, corrected with two interaction parameters. A limited temperature dependence of the interaction parameters was found. The correlations between the interaction parameters a...

  2. Biochemistry of Short-Chain Alkanes (Tissue-Specific Biosynthesis of n-Heptane in Pinus jeffreyi).

    Science.gov (United States)

    Savage, T. J.; Hamilton, B. S.; Croteau, R.

    1996-01-01

    Short-chain (C7-C11) alkanes accumulate as the volatile component of oleoresin (pitch) in several pine species native to western North America. To establish the tissue most amenable for use in detailed studies of short-chain alkane biosynthesis, we examined the tissue specificity of alkane accumulation and biosynthesis in Pinus jeffreyi Grev. & Balf. Short-chain alkane accumulation was highly tissue specific in both 2-year-old saplings and mature trees; heart-wood xylem accumulated alkanes up to 7.1 mg g-1 dry weight, whereas needles and other young green tissue contained oleoresin with monoterpenoid, rather than paraffinic, volatiles. These tissue-specific differences in oleoresin composition appear to be a result of tissue-specific rates of alkane and monoterpene biosynthesis; incubation of xylem tissue with [14C]sucrose resulted in accumulation of radiolabel in alkanes but not monoterpenes, whereas incubation of foliar tissue with 14CO2 resulted in the accumulation of radiolabel in monoterpenes but not alkanes. Furthermore, incubation of xylem sections with [14C]acetate resulted in incorporation of radiolabel into alkanes at rates up to 1.7 nmol h-1 g-1 fresh weight, a rate that exceeds most biosynthetic rates reported with other plant systems for the incorporation of this basic precursor into natural products. This suggests that P. jeffreyi may provide a suitable model for elucidating the enzymology and molecular biology of short-chain alkane biosynthesis.

  3. Combustion Characteristics of Liquid Normal Alkane Fuels in a Model Combustor of Supersonic Combustion Ramjet Engine

    Science.gov (United States)

    今村, 宰; 石川, 雄太; 鈴木, 俊介; 福本, 皓士郎; 西田, 俊介; 氏家, 康成; 津江, 光洋

    Effect of kinds of one-component n-alkane liquid fuels on combustion characteristics was investigated experimentally using a model combustor of scramjet engine. The inlet condition of a model combustor is 2.0 of Mach number, up to 2400K of total temperature, and 0.38MPa of total pressure. Five kinds of n-alkane are tested, of which carbon numbers are 7, 8, 10, 13, and 16. They are more chemically active and less volatile with an increase of alkane carbon number. Fuels are injected to the combustor in the upstream of cavity with barbotage nitrogen gas and self-ignition performance was investigated. The result shows that self-ignition occurs with less equivalence ratio when alkane carbon number is smaller. This indicates that physical characteristic of fuel, namely volatile of fuel, is dominant for self-ignition behavior. Effect on flame-holding performance is also examined with adding pilot hydrogen and combustion is kept after cutting off pilot hydrogen with the least equivalence ratio where alkane carbon number is from 8 to 10. These points are discussed qualitatively from the conflict effect of chemical and physical properties on alkane carbon number.

  4. Numerical and experimental studies of ethanol flames and autoignition theory for higher alkanes

    Science.gov (United States)

    Saxena, Priyank

    In order to enhance the fuel efficiency of an engine and to control pollutant formation, an improved understanding of the combustion chemistry of the fuels at a fundamental level is paramount. This knowledge can be gained by developing detailed reaction mechanisms of the fuels for various combustion processes and by studying combustion analytically employing reduced-chemistry descriptions. There is a need for small detailed reaction mechanisms for alkane and alcohol fuels with reduced uncertainties in their combustion chemistry that are computationally cheaper in multidimensional CFD calculations. Detailed mechanisms are the starting points in identifying reduced-chemistry descriptions of combustion processes to study problems analytically. This research includes numerical, experimental and analytical studies. The first part of the dissertation consists of numerical and experimental studies of ethanol flames. Although ethanol has gained popularity as a possible low-pollution source of renewable energy, significant uncertainties remain in its combustion chemistry. To begin to address ethanol combustion, first a relatively small detailed reaction mechanism, commonly known as the San Diego Mech, is developed for the combustion of hydrogen, carbon monoxide, formaldehyde, methane, methanol, ethane, ethylene, and acetylene, in air or oxygen-inert mixtures. This mechanism is tested for autoignition, premixed-flame burning velocities, and structures and extinction of diffusion flames and of partially premixed flames of many of these fuels. The reduction in uncertainties in the combustion chemistry can best be achieved by consistently updating a reaction mechanism with reaction rate data for the elementary steps based on newer studies in literature and by testing it against as many experimental conditions as available. The results of such a testing for abovementioned fuels are reported here along with the modifications of reaction-rate parameters of the most important

  5. Neutron diffraction and quasielastic neutron scattering studies of films of intermediate-length alkanes adsorbed on a graphite surface

    Science.gov (United States)

    Diama, Armand

    Over the past several years, we have conducted a variety of elastic neutron diffraction and quasielastic neutron scattering experiments to study the structure and the dynamics of films of two intermediate-length alkane molecules (C nH2n+2), adsorbed on a graphite basal-plane surface. The two molecules are the normal alkane n-tetracosane [n-CH 3(CH2)22CH3] and the branched alkane squalane (C30H62 or 2, 6, 10, 15, 19, 23-hexamethyltetracosane) whose carbon backbone is the same length as teteracosane. The temperature dependence of the monolayer structure of tetracosane and squalane was investigated using elastic neutron diffraction and evidence of two phase transitions was observed. Both the low-coverage tetracosane (C 24H50) and squalane (C30H62) monolayers have crystalline-to-"smectic" and "smectic"-to-isotropic fluid phase transitions upon heating. The diffusive motion in the tetracosane and squalane monolayers has been investigated by quasielastic neutron scattering. Two different quasielastic neutron scattering spectrometers at the Center for Neutron Research, National Institute of Standards and Technology (NIST) have been used. The spectrometers differ in both their dynamic range and energy resolution allowing molecular motions to be investigated on time scales in the range 10-13--10 -9 s. On these time scales, we observe evidence of translational, rotational, and intermolecular diffusive motions in the tetracosane and squalane monolayers. We conclude that the molecular diffusive motion in the two monolayers is qualitatively similar. Thus, despite the three methyl sidegroups at each end of the squalane molecule, its monolayer structure, phase transitions, and dynamics are qualitatively similar to that of a monolayer of the unbranched tetracosane molecules. With the higher resolution spectrometer at NIST, we have also investigated the molecular diffusive motion in multilayer tetracosane films. The analysis of our measurements indicates slower diffusive motion in

  6. Characterization of phospholipid+semifluorinated alkane vesicle system.

    Science.gov (United States)

    Sabín, Juan; Ruso, Juan M; González-Pérez, Alfredo; Prieto, Gerardo; Sarmiento, Félix

    2006-01-15

    The aim of this study is to characterize vesicles obtained by the incorporation of the semifluorinated alkane, (perfluoro-n-hexyl)ethane (diblock F6H2) to a standard lipid, egg yolk phosphatidylcholine (PC). Large unilamellar vesicles (LUVs), prepared by extrusion, were characterized by fluorescence spectroscopy, zeta potential (zeta-potential) and light scattering. By using the fluorescence spectroscopy technique, the anisotropy of l,6-diphenyl-l,3,5-hexatriene (DPH) probe at different temperatures was determined. It was demonstrated that F6H2 is placed inside of the lipid bilayer and that the hydrocarbon acyl chain in the bilayers has higher viscosity in the presence of fluoroalkane. The zeta-potential of the PC-F6H2 system is negative and increases (in absolute value) from -10 to -19 mV when the temperature rises from 10 to 25 degrees C, this last value keeping practically constant with a further increase of temperature. The adsorption of K+ ions on the liposome surface was measured by zeta-potential. This adsorption originates a sudden increase of the initial zeta-potential followed by a slight decrease with K+ concentration. The application of the DLVO theory of colloidal stability showed a growing dependence of the DLVO potential with K+ concentration and consequently a increasing stability.

  7. Digit ratios by computer-assisted analysis confirm lack of anatomical evidence of prenatal androgen exposure in clinical phenotypes of polycystic ovary syndrome

    Directory of Open Access Journals (Sweden)

    Lehotay Denis C

    2010-12-01

    Full Text Available Abstract Background We recently showed that women with four clinical phenotypes of polycystic ovary syndrome (PCOS do not demonstrate anatomical evidence of elevated prenatal androgen exposure as judged by a lower ratio of the index (2D to ring (4D finger. However, those findings conflicted with a previous study where women with PCOS had lower right hand 2D:4D compared to healthy female controls. Both these studies used Vernier calipers to measure finger lengths - a method recently shown to be less reliable at obtaining finger length measurements than computer-assisted analysis. Methods Ninety-six women diagnosed with PCOS according to the 2003 Rotterdam criteria had their finger lengths measured with computer-assisted analysis. Participants were categorized into four recognized phenotypes of PCOS and their 2D:4D compared to healthy female controls (n = 48 and men (n = 50. Results Digit ratios assessed by computer-assisted analysis in women with PCOS did not differ from female controls, but were significantly lower in men. When subjects were stratified by PCOS phenotype, 2D:4D did not differ among phenotypes or when compared to female controls. Conclusion Computer-assisted measurements validated that digit ratios of women with PCOS do not show anatomical evidence of increased prenatal androgen exposure.

  8. Empirical evidence that proves a serious game is an educationally effective tool for learning computer programming constructs at the computational thinking level

    OpenAIRE

    2013-01-01

    Owing to their easy engagement and motivational nature, games predominantly in young age groups, have been omnipresent in education since ancient times. More recently, computer video games have become widely used, particularly in secondary and tertiary education, as a method of enhancing the understanding of some subject areas (especially in English language education, geography, history and health) and also used as an aid to attracting and retaining students. Many academics have proposed...

  9. Understanding the factors affecting the activation of alkane by Cp'Rh(CO)2 (Cp' = Cp or Cp*).

    Science.gov (United States)

    George, Michael W; Hall, Michael B; Jina, Omar S; Portius, Peter; Sun, Xue-Zhong; Towrie, Michael; Wu, Hong; Yang, Xinzheng; Zaric, Snezana D

    2010-11-23

    Fast time-resolved infrared spectroscopic measurements have allowed precise determination of the rates of activation of alkanes by Cp'Rh(CO) (Cp(') = η(5)-C(5)H(5) or η(5)-C(5)Me(5)). We have monitored the kinetics of C─H activation in solution at room temperature and determined how the change in rate of oxidative cleavage varies from methane to decane. The lifetime of CpRh(CO)(alkane) shows a nearly linear behavior with respect to the length of the alkane chain, whereas the related Cp*Rh(CO)(alkane) has clear oscillatory behavior upon changing the alkane. Coupled cluster and density functional theory calculations on these complexes, transition states, and intermediates provide the insight into the mechanism and barriers in order to develop a kinetic simulation of the experimental results. The observed behavior is a subtle interplay between the rates of activation and migration. Unexpectedly, the calculations predict that the most rapid process in these Cp'Rh(CO)(alkane) systems is the 1,3-migration along the alkane chain. The linear behavior in the observed lifetime of CpRh(CO)(alkane) results from a mechanism in which the next most rapid process is the activation of primary C─H bonds (─CH(3) groups), while the third key step in this system is 1,2-migration with a slightly slower rate. The oscillatory behavior in the lifetime of Cp*Rh(CO)(alkane) with respect to the alkane's chain length follows from subtle interplay between more rapid migrations and less rapid primary C─H activation, with respect to CpRh(CO)(alkane), especially when the CH(3) group is near a gauche turn. This interplay results in the activation being controlled by the percentage of alkane conformers.

  10. Session 6: Highly active Pt/zeolite catalysts for combustion of C{sub 2}-C{sub 4} alkanes

    Energy Technology Data Exchange (ETDEWEB)

    Garetto, T.F.; Rincon, E.; Apesteguia, C.R. [Instituto de Investigaciones en Catalisis y Petroquimica -INCAPE- (UNL-CONICET), Santa Fe (Argentina)

    2004-07-01

    In an attempt for developing more active Pt-based catalysts for lower-alkane combustion, we investigate in this work the deep oxidation of C{sub 2}-C{sub 4} alkanes over Pt-based catalysts. Results show that the lower alkane oxidation turnover rates are more than two orders of magnitude higher on Pt/zeolites compared to Pt/Al{sub 2}O{sub 3} catalyst. (authors)

  11. Fatty aldehyde dehydrogenase multigene family involved in the assimilation of n-alkanes in Yarrowia lipolytica.

    Science.gov (United States)

    Iwama, Ryo; Kobayashi, Satoshi; Ohta, Akinori; Horiuchi, Hiroyuki; Fukuda, Ryouichi

    2014-11-28

    In the n-alkane assimilating yeast Yarrowia lipolytica, n-alkanes are oxidized to fatty acids via fatty alcohols and fatty aldehydes, after which they are utilized as carbon sources. Here, we show that four genes (HFD1-HFD4) encoding fatty aldehyde dehydrogenases (FALDHs) are involved in the metabolism of n-alkanes in Y. lipolytica. A mutant, in which all of four HFD genes are deleted (Δhfd1-4 strain), could not grow on n-alkanes of 12-18 carbons; however, the expression of one of those HFD genes restored its growth on n-alkanes. Production of Hfd2Ap or Hfd2Bp, translation products of transcript variants generated from HFD2 by the absence or presence of splicing, also supported the growth of the Δhfd1-4 strain on n-alkanes. The FALDH activity in the extract of the wild-type strain was increased when cells were incubated in the presence of n-decane, whereas this elevation in FALDH activity by n-decane was not observed in Δhfd1-4 strain extract. Substantial FALDH activities were detected in the extracts of Escherichia coli cells expressing the HFD genes. Fluorescent microscopic observation suggests that Hfd3p and Hfd2Bp are localized predominantly in the peroxisome, whereas Hfd1p and Hfd2Ap are localized in both the endoplasmic reticulum and the peroxisome. These results suggest that the HFD multigene family is responsible for the oxidation of fatty aldehydes to fatty acids in the metabolism of n-alkanes, and raise the possibility that Hfd proteins have diversified by gene multiplication and RNA splicing to efficiently assimilate or detoxify fatty aldehydes in Y. lipolytica.

  12. Alkane Hydroxylase Gene (alkB Phylotype Composition and Diversity in Northern Gulf of Mexico Bacterioplankton

    Directory of Open Access Journals (Sweden)

    Conor Blake Smith

    2013-12-01

    Full Text Available Natural and anthropogenic activities introduce alkanes into marine systems where they are degraded by alkane hydroxylases expressed by phylogenetically diverse bacteria. Partial sequences for alkB, one of the structural genes of alkane hydroxylase, have been used to assess the composition of alkane-degrading communities, and to determine their responses to hydrocarbon inputs. We present here the first spatially extensive analysis of alkB in bacterioplankton of the northern Gulf of Mexico (nGoM, a region that experiences numerous hydrocarbon inputs. We have analyzed 401 partial alkB gene sequences amplified from genomic extracts collected during March 2010 from 17 water column samples that included surface waters and bathypelagic depths. Previous analyses of 16S rRNA gene sequences for these and related samples have shown that nGoM bacterial community composition and structure stratify strongly with depth, with distinctly different communities above and below 100 m. Although we hypothesized that alkB gene sequences would exhibit a similar pattern, PCA analyses of operational protein units (OPU indicated that community composition did not vary consistently with depth or other major physical-chemical variables. We observed 22 distinct OPUs, one of which was ubiquitous and accounted for 57% of all sequences. This OPU clustered with alkB sequences from known hydrocarbon oxidizers (e.g., Alcanivorax and Marinobacter. Some OPUs could not be associated with known alkane degraders, however, and perhaps represent novel hydrocarbon-oxidizing populations or genes. These results indicate that the capacity for alkane hydrolysis occurs widely in the nGoM, but that alkane degrader diversity varies substantially among sites and responds differently than bulk communities to physical-chemical variables.

  13. Characterization of n-alkanes in PM{sub 2.5} of the Taipei aerosol

    Energy Technology Data Exchange (ETDEWEB)

    Young, Li Hao [National Taiwan Univ., Taipei (Taiwan). Graduate Inst. of Environmental Health; Wang, Chiu Sen [National Taiwan Univ., Taipei (Taiwan). Dept. of Public Health

    2002-07-01

    Ambient concentrations of n-alkanes with carbon number ranging from 17 to 36 were determined for PM{sub 2.5} collected in Taipei city during September 1997-February 1998. The measured concentrations of particulate n-alkanes were in the range of 69-702ngm{sup -3} considerably higher than the concentration levels observed in Los Angeles and Hong Kong. The concentration distributions of n-alkanes homologues obtained in this study exhibited peaks at C{sub 19}, C{sub 24} or C{sub 25}. This suggests that fossil fuel utilization, such as vehicular exhaust and lubricant residues, was an important contributor to the Taipei aerosol. Source apportionment of PM{sub 2.5} was conducted using carbon preference index (CPI, defined as the ratio of the total concentration of particulate n-alkanes with odd carbon number to that with even carbon number) and U:R ratio (the concentration ratio of unresolved components to resolved components obtained from chromatograms). The low CPI value (0.9-1.9) and high U:R ratio (2.6-6.4) for each sample further confirmed that fossil fuel utilization was the major source of n-alkanes in ambient PM{sub 2.5} of Taipei city. Estimates from these results showed that 69-93% of the n-alkanes in PM{sub 2.5} of the Taipei aerosol originated from vehicular exhaust. The higher concentration level of particulate n-alkanes in the Taipei aerosol was mainly a result of vehicular emissions. (author)

  14. Squeezing molecular thin alkane lubrication films between curved solid surfaces with long-range elasticity: Layering transitions and wear

    DEFF Research Database (Denmark)

    Sivebæk, Ion Marius; Samoilov, V. N.; Persson, B. N. J.

    2003-01-01

    The properties of alkane lubricants confined between two approaching solids are investigated by a model that accounts for the curvature and the elastic properties of the solid surfaces. We consider linear alkane molecules of different chain lengths, C3H8, C4H10, C8H18, C9H20, C10H22, C12H26 and C14...... of lubricant layers. We find that with increasing alkane chain length, the transition from n to n-1 layers occurs at higher pressure, as expected based on the increasing wettability ~or spreading pressure with increasing chain length. Thus, the longer alkanes are better boundary lubricants than the shorter...

  15. Anaerobic alkane biodegradation by cultures enriched from oil sands tailings ponds involves multiple species capable of fumarate addition.

    Science.gov (United States)

    Tan, BoonFei; Semple, Kathleen; Foght, Julia

    2015-05-01

    A methanogenic short-chain alkane-degrading culture (SCADC) was enriched from oil sands tailings and transferred several times with a mixture of C6, C7, C8 and C10 n-alkanes as the predominant organic carbon source, plus 2-methylpentane, 3-methylpentane and methylcyclopentane as minor components. Cultures produced ∼40% of the maximum theoretical methane during 18 months incubation while depleting the n-alkanes, 2-methylpentane and methylcyclopentane. Substrate depletion correlated with detection of metabolites characteristic of fumarate activation of 2-methylpentane and methylcyclopentane, but not n-alkane metabolites. During active methanogenesis with the mixed alkanes, reverse-transcription PCR confirmed the expression of functional genes (assA and bssA) associated with hydrocarbon addition to fumarate. Pyrosequencing of 16S rRNA genes amplified during active alkane degradation revealed enrichment of Clostridia (particularly Peptococcaceae) and methanogenic Archaea (Methanosaetaceae and Methanomicrobiaceae). Methanogenic cultures transferred into medium containing sulphate produced sulphide, depleted n-alkanes and produced the corresponding succinylated alkane metabolites, but were slow to degrade 2-methylpentane and methylcyclopentane; these cultures were enriched in Deltaproteobacteria rather than Clostridia. 3-Methylpentane was not degraded by any cultures. Thus, nominally methanogenic oil sands tailings harbour dynamic and versatile hydrocarbon-degrading fermentative syntrophs and sulphate reducers capable of degrading n-, iso- and cyclo-alkanes by addition to fumarate.

  16. Cyclooctane metathesis catalyzed by silica-supported tungsten pentamethyl [(ΞSiO)W(Me)5]: Distribution of macrocyclic alkanes

    KAUST Repository

    Riache, Nassima

    2014-10-03

    Metathesis of cyclic alkanes catalyzed by the new surface complex [(ΞSiO)W(Me)5] affords a wide distribution of cyclic and macrocyclic alkanes. The major products with the formula CnH2n are the result of either a ring contraction or ring expansion of cyclooctane leading to lower unsubstituted cyclic alkanes (5≤n≤7) and to an unprecedented distribution of unsubstituted macrocyclic alkanes (12≤n≤40), respectively, identified by GC/MS and by NMR spectroscopies.

  17. Leaf wax n-alkane distributions in and across modern plants: Implications for paleoecology and chemotaxonomy

    Science.gov (United States)

    Bush, Rosemary T.; McInerney, Francesca A.

    2013-09-01

    Long chain (C21 to C37) n-alkanes are among the most long-lived and widely utilized terrestrial plant biomarkers. Dozens of studies have examined the range and variation of n-alkane chain-length abundances in modern plants from around the world, and n-alkane distributions have been used for a variety of purposes in paleoclimatology and paleoecology as well as chemotaxonomy. However, most of the paleoecological applications of n-alkane distributions have been based on a narrow set of modern data that cannot address intra- and inter-plant variability. Here, we present the results of a study using trees from near Chicago, IL, USA, as well as a meta-analysis of published data on modern plant n-alkane distributions. First, we test the conformity of n-alkane distributions in mature leaves across the canopy of 38 individual plants from 24 species as well as across a single growing season and find no significant differences for either canopy position or time of leaf collection. Second, we compile 2093 observations from 86 sources, including the new data here, to examine the generalities of n-alkane parameters such as carbon preference index (CPI), average chain length (ACL), and chain-length ratios for different plant groups. We show that angiosperms generally produce more n-alkanes than do gymnosperms, supporting previous observations, and furthermore that CPI values show such variation in modern plants that it is prudent to discard the use of CPI as a quantitative indicator of n-alkane degradation in sediments. We also test the hypotheses that certain n-alkane chain lengths predominate in and therefore can be representative of particular plant groups, namely, C23 and C25 in Sphagnum mosses, C27 and C29 in woody plants, and C31 in graminoids (grasses). We find that chain-length distributions are highly variable within plant groups, such that chemotaxonomic distinctions between grasses and woody plants are difficult to make based on n-alkane abundances. In contrast

  18. Ubiquitous Presence and Novel Diversity of Anaerobic Alkane Degraders in Cold Marine Sediments.

    Science.gov (United States)

    Gittel, Antje; Donhauser, Johanna; Røy, Hans; Girguis, Peter R; Jørgensen, Bo B; Kjeldsen, Kasper U

    2015-01-01

    Alkanes are major constituents of crude oil and are released to the marine environment by natural seepage and from anthropogenic sources. Due to their chemical inertness, their removal from anoxic marine sediments is primarily controlled by the activity of anaerobic alkane-degrading microorganisms. To facilitate comprehensive cultivation-independent surveys of the diversity and distribution of anaerobic alkane degraders, we designed novel PCR primers that cover all known diversity of the 1-methylalkyl succinate synthase gene (masD/assA), which catalyzes the initial activation of alkanes. We studied masD/assA gene diversity in pristine and seepage-impacted Danish coastal sediments, as well as in sediments and alkane-degrading enrichment cultures from the Middle Valley (MV) hydrothermal vent system in the Pacific Northwest. MasD/assA genes were ubiquitously present, and the primers captured the diversity of both known and previously undiscovered masD/assA gene diversity. Seepage sediments were dominated by a single masD/assA gene cluster, which is presumably indicative of a substrate-adapted community, while pristine sediments harbored a diverse range of masD/assA phylotypes including those present in seepage sediments. This rare biosphere of anaerobic alkane degraders will likely increase in abundance in the event of seepage or accidental oil spillage. Nanomolar concentrations of short-chain alkanes (SCA) were detected in pristine and seepage sediments. Interestingly, anaerobic alkane degraders closely related to strain BuS5, the only SCA degrader in pure culture, were found in mesophilic MV enrichments, but not in cold sediments from Danish waters. We propose that the new masD/assA gene lineages in these sediments represent novel phylotypes that are either fueled by naturally occurring low levels of SCA or that metabolize medium- to long-chain alkanes. Our study highlights that masD/assA genes are a relevant diagnostic marker to identify seepage and microseepage, e

  19. Composition index of n-alkanes and paleoenvironmental study in sediments of the Arctic

    Institute of Scientific and Technical Information of China (English)

    Lu Bing; Zhou Huaiyang; Wang Zipan; Lu Douding

    2001-01-01

    This paper reports different concentration patterns of n-alkanes distribution in the sediments from the Chukchi Sea, the Bering Sea in the Arctic. Factor statistical analysis method is used for studying the source of n-alkanes and paleoenviroment. The result shows that n-alkanes is in the range of nC15~nC33 and n-alkane distribution patterns are characterized by two modes. The first mode belongs to the higher molecular with MH being nC25~ nC27, CPI> 1 and with remarkable odd-even dominance.They are of terrigenous plant origin. The second one belongs to lower carbon range with MH being nC17 ~nC20, CPI> 1 and with indistinct odd-even dominance. Therefore they are contributed by marine biological inputs. The contribution of land origin is larger than that of marine source. Pr/Ph is lower than 1 in the investigated area, which indicates the depositional environment of reducing reaction with lower oxygen. The result of factor analysis has good agreement with composition characteristics of n-alkanes in the sediment.

  20. Extension of Tao-Mason Equation of State to Heavy n-Alkanes

    Institute of Scientific and Technical Information of China (English)

    Fakhri Yousefi; Hajir Karimi; Mohammad Mehdi Papari

    2013-01-01

    In our previous paper we extended the Tao and Mason equation of state (TM EOS) to refrigerant fluids, using the speed of sound data. This is a continuation for evaluating TM EOS in predicting PVT properties of heavy n-alkanes. Liquid density of long-chain n-alkane systems from C9 to C20 have been calculated using an analytical equation of state based on the statistical-mechanical perturbation theory. The second virial coefficients of these n-alkanes are scarce and there is no accurate potential energy function for their theoretical calculation. In this work the second virial coefficients are calculated using a corresponding state correlation based on surface tension and liquid density at the freezing point. The deviation of calculated densities of these alkanes is within 0.5%from ex-perimental data. The densities of n-alkanes obtained from the TM EOS are compared with those calculated from Ihm-Song-Mason equation of state and the corresponding-states liquid densities (COSTALD). Our results are in favor of the preference of the TM EOS over other two equations of state.

  1. Simulation experiments on the variation of leaf n-alkanes in aquatic environments

    Institute of Scientific and Technical Information of China (English)

    Chengling JIA; Anwen ZHOU; Xiangru MA; Jingjing LI; Shucheng XIE

    2009-01-01

    The leaves of six plant species and the corresponding leaf residues collected in water from the two-year simulation experiments were analyzed in n-alkane distributions by gas chromatography (GC) and gas chromatography-mas spectrometry (GC/MS). The leaf n-alkanes keep unchanged in the dominant homologues when soaked in tap water for two years. The most significant change was observed in carbon preference index (CPI), with enhanced values being found in leaf residues collected from water. This is contradictory with the previous reports showing the lower CPI values during sinking and burial processes in natural aquatic environments. The elevated CPI values from leaf residues might be related to the low amount of microorganisms in the water used in the simulation experiment, and the enhanced solubility of even-carbon-numbered n-alkanes via van der Waals attraction. In contrast with herbaceous plants, the woody plants appear to show relatively great variations in both the CPI and the average chain length (ACL) values of n-alkanes after submerged in water for two years. Our data clearly show the differentiated decomposition between woody and herbaceous leaves, with the woody leaves suffered from much stronger decomposition. This observation suggests that in comparison with the grassland, the forest vegetation might result in relatively low authentic signals to be preserved in the n-alkane distributions in aquatic sediments.

  2. Distribution of alkB genes within n-alkane-degrading bacteria.

    Science.gov (United States)

    Vomberg, A; Klinner, U

    2000-08-01

    Fifty-four bacterial strains belonging to 37 species were tested for their ability to assimilate short chain and/or medium chain liquid n-alkanes. A gene probe derived from the alkB gene of Pseudomonas oleovorans ATCC 29347 was utilized in hybridization experiments. Results of Southern hybridization of PCR-amplificates were compared with those of colony hybridization and dot blot hybridization. Strongest signals were received only from Gram-negative bacteria growing solely with short n-alkanes (C10). Hybridization results with soil isolates growing with n-alkanes of different chain lengths suggested as well that alkB genes seem to be widespread only in solely short-chain n-alkane-degrading pseudomonads. PCR products of Rhodococcus sp., Nocardioides sp., Gordona sp. and Sphingomonas sp. growing additionally or solely with medium-chain n-alkane as hexadecane had only few sequence identity with alkB though hybridizing with the gene probe. The derived amino acid sequence of the alkB-amplificate of Pseudomonas aureofaciens showed high homology (95%) with AlkB from Ps. oleovorans. alkB gene disruptants were not able to grow with decane.

  3. Toward aldehyde and alkane production by removing aldehyde reductase activity in Escherichia coli.

    Science.gov (United States)

    Rodriguez, Gabriel M; Atsumi, Shota

    2014-09-01

    Advances in synthetic biology and metabolic engineering have enabled the construction of novel biological routes to valuable chemicals using suitable microbial hosts. Aldehydes serve as chemical feedstocks in the synthesis of rubbers, plastics, and other larger molecules. Microbial production of alkanes is dependent on the formation of a fatty aldehyde intermediate which is converted to an alkane by an aldehyde deformylating oxygenase (ADO). However, microbial hosts such as Escherichia coli are plagued by many highly active endogenous aldehyde reductases (ALRs) that convert aldehydes to alcohols, which greatly complicates strain engineering for aldehyde and alkane production. It has been shown that the endogenous ALR activity outcompetes the ADO enzyme for fatty aldehyde substrate. The large degree of ALR redundancy coupled with an incomplete database of ALRs represents a significant obstacle in engineering E. coli for either aldehyde or alkane production. In this study, we identified 44 ALR candidates encoded in the E. coli genome using bioinformatics tools, and undertook a comprehensive screening by measuring the ability of these enzymes to produce isobutanol. From the pool of 44 candidates, we found five new ALRs using this screening method (YahK, DkgA, GldA, YbbO, and YghA). Combined deletions of all 13 known ALRs resulted in a 90-99% reduction in endogenous ALR activity for a wide range of aldehyde substrates (C2-C12). Elucidation of the ALRs found in E. coli could guide one in reducing competing alcohol formation during alkane or aldehyde production.

  4. ClogP(alk): a method for predicting alkane/water partition coefficient.

    Science.gov (United States)

    Kenny, Peter W; Montanari, Carlos A; Prokopczyk, Igor M

    2013-05-01

    Alkane/water partition coefficients (P(alk)) are less familiar to the molecular design community than their 1-octanol/water equivalents and access to both data and prediction tools is much more limited. A method for predicting alkane/water partition coefficient from molecular structure is introduced. The basis for the ClogP(alk) model is the strong (R² = 0.987) relationship between alkane/water partition coefficient and molecular surface area (MSA) that was observed for saturated hydrocarbons. The model treats a molecule as a perturbation of a saturated hydrocarbon molecule with the same MSA and uses increments defined for functional groups to quantify the extent to which logP(alk) is perturbed by the introduction each functional group. Interactions between functional groups, such as intramolecular hydrogen bonds are also parameterized within a perturbation framework. The functional groups and interactions between them are specified substructurally in a transparent and reproducible manner using SMARTS notation. The ClogP(alk) model was parameterized using data measured for structurally prototypical compounds that dominate the literature on alkane/water partition coefficients and then validated using an external test set of 100 alkane/water logP measurements, the majority of which were for drugs.

  5. Thermodynamics of mixtures containing alkoxyethanols. XXVIII: Liquid-liquid equilibria for 2-phenoxyethanol + selected alkanes

    Energy Technology Data Exchange (ETDEWEB)

    Alonso, Victor; Garcia, Mario [G.E.T.E.F., Grupo Especializado en Termodinamica de Equilibrio entre Fases, Departamento de Fisica Aplicada, Facultad de Ciencias, Universidad de Valladolid, E-47071 Valladolid (Spain); Gonzalez, Juan Antonio, E-mail: jagl@termo.uva.es [G.E.T.E.F., Grupo Especializado en Termodinamica de Equilibrio entre Fases, Departamento de Fisica Aplicada, Facultad de Ciencias, Universidad de Valladolid, E-47071 Valladolid (Spain); Garcia De La Fuente, Isaias; Cobos, Jose Carlos [G.E.T.E.F., Grupo Especializado en Termodinamica de Equilibrio entre Fases, Departamento de Fisica Aplicada, Facultad de Ciencias, Universidad de Valladolid, E-47071 Valladolid (Spain)

    2011-07-10

    Highlights: {yields} LLE coexistence curves were determined for mixtures of 2PhEE with alkanes. {yields} UCST values are higher for n-alkane systems than for solutions with cyclic alkanes. {yields} For the latter mixtures, UCST increases with the size of the alkyl group attached. {yields} Alkoxyethanol-alkoxyethanol interactions are enhanced by aromatic group in cellosolve. - Abstract: The coexistence curves of the liquid-liquid equilibria (LLE) for systems of 2-phenoxyethanol (2PhEE) with heptane, octane, cyclohexane, methylcyclohexane or ethylcyclohexane have been determined by the method of the critical opalescence using a laser scattering technique. All the curves show an upper critical solution temperature (UCST), have a rather horizontal top and their symmetry depends on the relative size of the mixture compounds. UCST values are higher for systems with linear alkanes than for solutions including cyclic alkanes. For these mixtures, the UCST increases with the size of the alkyl group attached to the cyclic part of the molecule. It is shown that interactions between alkoxyethanol molecules are stronger when the hydroxyether contains an aromatic group. Data are used to determine the critical exponent for the order parameter mole fraction. Values obtained are consistent with those provided by the Ising model or by the renormalization group theory.

  6. Carbon Isotopes of Alkanes in Hydrothermal Abiotic Organic Synthesis Processes at High Temperatures and Pressures: An Experimental Study

    Science.gov (United States)

    Fu, Qi; Socki, Richard A.; Niles, Paul B.

    2010-01-01

    Observation of methane in the Martian atmosphere has been reported by different detection techniques [1-4]. With more evidence showing extensive water-rock interaction in Martian history [5-7], abiotic formation by Fischer-Tropsch Type (FTT) synthesis during serpentization reactions may be one possible process responsible for methane generation on Mars [8, 9]. While the experimental studies performed to date leave little doubt that chemical reactions exist for the abiotic synthesis of organic compounds by mineral surface-catalyzed reactions [10-12], little is known about the reaction pathways by which CO2 and/or CO are reduced under hydrothermal conditions. Carbon and hydrogen isotope measurements of alkanes have been used as an effective tool to constrain the origin and reaction pathways of hydrocarbon formation. Alkanes generated by thermal breakdown of high molecular weight organic compounds have carbon and hydrogen isotopic signatures completely distinct from those formed abiotically [13-15]. Recent experimental studies, however, showed that different abiogenic hydrocarbon formation processes (e.g., polymerization vs. depolymerization) may have different carbon and hydrogen isotopic patterns [16]. Results from previous experiments studying decomposition of higher molecular weight organic compounds (lignite) also suggested that pressure could be a crucial factor affecting fractionation of carbon isotopes [17]. Under high pressure conditions, no experimental data are available describing fractionation of carbon isotope during mineral catalyzed FTT synthesis. Thus, hydrothermal experiments present an excellent opportunity to provide the requisite carbon isotope data. Such data can also be used to identify reaction pathways of abiotic organic synthesis under experimental conditions.

  7. Establishing Computer-Assisted Instruction to Teach Academics to Students with Autism as an Evidence-Based Practice

    Science.gov (United States)

    Root, Jenny R.; Stevenson, Bradley S.; Davis, Luann Ley; Geddes-Hall, Jennifer; Test, David W.

    2017-01-01

    Computer-assisted instruction (CAI) is growing in popularity and has demonstrated positive effects for students with disabilities, including those with autism spectrum disorder (ASD). In this review, criteria for group experimental and single case studies were used to determine quality (Horner et al., "Exceptional Children" 71:165-179,…

  8. Evidence for phosphorus bonding in phosphorus trichloride-methanol adduct: a matrix isolation infrared and ab initio computational study.

    Science.gov (United States)

    Joshi, Prasad Ramesh; Ramanathan, N; Sundararajan, K; Sankaran, K

    2015-04-09

    The weak interaction between PCl3 and CH3OH was investigated using matrix isolation infrared spectroscopy and ab initio computations. In a nitrogen matrix at low temperature, the noncovalent adduct was generated and characterized using Fourier transform infrared spectroscopy. Computations were performed at B3LYP/6-311++G(d,p), B3LYP/aug-cc-pVDZ, and MP2/6-311++G(d,p) levels of theory to optimize the possible geometries of PCl3-CH3OH adducts. Computations revealed two minima on the potential energy surface, of which, the global minimum is stabilized by a noncovalent P···O interaction, known as a pnictogen bonding (phosphorus bonding or P-bonding). The local minimum corresponded to a cyclic adduct, stabilized by the conventional hydrogen bonding (Cl···H-O and Cl···H-C interactions). Experimentally, 1:1 P-bonded PCl3-CH3OH adduct in nitrogen matrix was identified, where shifts in the P-Cl modes of PCl3, O-C, and O-H modes of CH3OH submolecules were observed. The observed vibrational frequencies of the P-bonded adduct in a nitrogen matrix agreed well with the computed frequencies. Furthermore, computations also predicted that the P-bonded adduct is stronger than H-bonded adduct by ∼1.56 kcal/mol. Atoms in molecules and natural bond orbital analyses were performed to understand the nature of interactions and effect of charge transfer interaction on the stability of the adducts.

  9. Transferable potentials for phase equilibria-coarse-grain description for linear alkanes.

    Science.gov (United States)

    Maerzke, Katie A; Siepmann, J Ilja

    2011-04-07

    Coarse-grain potentials allow one to extend molecular simulations to length and time scales beyond those accesssible to atomistic representations of the interacting system. Since the coarse-grain potentials remove a large number of interaction sites and, hence, a large number of degrees of freedom, it is generally assumed that coarse-grain potentials are not transferable to different systems or state points (temperature and pressure). Here we apply lessons learned from the parametrization of transferable atomistic potentials to develop a systematic procedure for the parametrization of transferable coarse-grain potentials. In particular, we apply an iterative Boltzmann optimization for the determination of the bonded interactions for coarse-grain beads belonging to the same molecule and separated by one or two coarse-grain bonds and parametrize the nonbonded interactions by fitting to the vapor-liquid coexistence curves computed for selected molecules represented by the TraPPE-UA (transferable potentials for phase equilibria-united atom) force field. This approach is tested here for linear alkanes where parameters for C(3)H(7) end segments and for C(3)H(6) middle segments of the TraPPE-CG (transferable potentials for phase equilibria-coarse grain) force field are determined and it is shown that these parameters yield quite accurate vapor-liquid equilibria for neat n-hexane to n-triacontane and for the binary mixture of n-hexane and n-hexatriacontane. In addition, the position of the first peak in various radial distribution functions and the coordination number for the first solvation shell are well reproduced by the TraPPE-CG force field, but the first peaks are too high and narrow.

  10. Structure and solvation forces in confined films: Linear and branched alkanes

    Energy Technology Data Exchange (ETDEWEB)

    Gao, J.; Luedtke, W.D.; Landman, U. [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

    1997-03-01

    Equilibrium structures, solvation forces, and conformational dynamics of thin confined films of n-hexadecane and squalane are investigated using a new grand canonical ensemble molecular dynamics method for simulations of confined liquids. The method combines constant pressure simulations with a computational cell containing solid surfaces and both bulk and confined liquid regions in equilibrium with each other. Layered density oscillations in the confined films are found for various widths of the confining gap. The solvation force oscillations as a function of the gap width for the straight chain n-hexadecane liquid are more pronounced exhibiting attractive and repulsive regions, while for the branched alkane the solvation forces are mostly repulsive, with the development of shallow local attractive regions for small values of the gap width. Furthermore, the nature of the transitions between well-formed layered configurations is different in the two systems. The n-hexadecane film exhibits solid-like characteristics portrayed by step-like variations in the number of confined segments occurring in response to a small decrease in the gap width, starting from well-layered states of the film; the behavior of the squalane film is liquid-like, exhibiting a monotonic continuous decrease in the number of confined segments as the gap width is decreased. These characteristics are correlated with structural properties of the confined films which, for n-hexadecane, exhibit enhanced layered ordering and in-plane ordered molecular arrangements, as well as with the relatively high tendency for interlayer molecular interdigitation in the squalane films. Reduced conformational (trans-guache) transition rates in the confined films, compared to their bulk values, are found, and their oscillatory dependence on the degree of confinement is analyzed, showing smaller transition rates for the well-formed layered states of the films. {copyright} {ital 1997 American Institute of Physics.}

  11. Radical and Non-Radical Mechanisms for Alkane Oxidations by Hydrogen Peroxide-Trifluoroacetic Acid

    Energy Technology Data Exchange (ETDEWEB)

    Camaioni, Donald M.; Bays, J. Timothy; Shaw, Wendy J.; Linehan, John C.; Birnbaum, Jerome C.

    2001-02-01

    The oxidation of cyclohexane by the H2O2-trifluoroacetic acid system is revisited. Consistent with a previous report (Deno, N.; Messer, L. A. Chem. Comm. 1976, 1051), cyclohexanol forms initially but then esterifies to cyclohexyl trifluoroacetate. Small amounts of trans-1,2-cyclohexadiyl bis(trifluoroacetate) also form. Although these products form irrespective of the presence or absence of O2, dual mechanisms are shown to operate. In the absence of O2, the dominant mechanism is a radical chain reaction that is propagated by CF3• abstracting H from C6H12 and SH2 displacement of C6H11• on CF3CO2OH. The intermediacy of C6H11• and CF3• is inferred from production of CHF3 and CO2 along with cyclohexyl trifluoroacetate, or CDF3 when cyclohexane-d12 is used. In the presence of O2, fluoroform and CO2 are suppressed, the reaction rate slows, and the rate law approaches second order (first order in peracid and in C6H12). Trapping of cyclohexyl radicals by quinoxaline is inefficient except at elevated (75 °C) temperatures. Fluoroform and CO2, telltale evidence for the chain pathway, were not produced when quinoxaline was present in room temperature reactions. These observations suggest that a parallel, nonfree radical, oxenoid insertion mechanism dominates when O2 is present. A pathway is discussed in which a biradicaloid-zwiterionic transition state is attained by hydrogen transfer from alkane to peroxide oxygen with synchronous O-O bond scission.

  12. Additional chain-branching pathways in the low-temperature oxidation of branched alkanes

    KAUST Repository

    Wang, Zhandong

    2015-12-31

    Chain-branching reactions represent a general motif in chemistry, encountered in atmospheric chemistry, combustion, polymerization, and photochemistry; the nature and amount of radicals generated by chain-branching are decisive for the reaction progress, its energy signature, and the time towards its completion. In this study, experimental evidence for two new types of chain-branching reactions is presented, based upon detection of highly oxidized multifunctional molecules (HOM) formed during the gas-phase low-temperature oxidation of a branched alkane under conditions relevant to combustion. The oxidation of 2,5-dimethylhexane (DMH) in a jet-stirred reactor (JSR) was studied using synchrotron vacuum ultra-violet photoionization molecular beam mass spectrometry (SVUV-PI-MBMS). Specifically, species with four and five oxygen atoms were probed, having molecular formulas of C8H14O4 (e.g., diketo-hydroperoxide/keto-hydroperoxy cyclic ether) and C8H16O5 (e.g., keto-dihydroperoxide/dihydroperoxy cyclic ether), respectively. The formation of C8H16O5 species involves alternative isomerization of OOQOOH radicals via intramolecular H-atom migration, followed by third O2 addition, intramolecular isomerization, and OH release; C8H14O4 species are proposed to result from subsequent reactions of C8H16O5 species. The mechanistic pathways involving these species are related to those proposed as a source of low-volatility highly oxygenated species in Earth\\'s troposphere. At the higher temperatures relevant to auto-ignition, they can result in a net increase of hydroxyl radical production, so these are additional radical chain-branching pathways for ignition. The results presented herein extend the conceptual basis of reaction mechanisms used to predict the reaction behavior of ignition, and have implications on atmospheric gas-phase chemistry and the oxidative stability of organic substances. © 2015 The Combustion Institute.

  13. The synergetic effect of starch and alpha amylase on the biodegradation of n-alkanes.

    Science.gov (United States)

    Karimi, M; Biria, D

    2016-06-01

    The impact of adding soluble starch on biodegradation of n-alkanes (C10-C14) by Bacillus subtilis TB1 was investigated. Gas chromatography was employed to measure the residual hydrocarbons in the system. It was observed that the efficiency of biodegradation improved with the presence of starch and the obtained residual hydrocarbons in the system were 53% less than the samples without starch. The produced bacterial enzymes were studied through electrophoresis and reverse zymography for explaining the observations. The results indicated that the produced amylase by the bacteria can degrade hydrocarbons and the same was obtained by the application of a commercial alpha amylase sample. In addition, in silico docking of alpha-amylase with n-alkanes with different molecular weights was studied by Molegro virtual docker which showed high negative binding energies and further substantiated the experimental observations. Overall, the findings confirmed the catalytic effect of alpha amylase on n-alkanes degradation.

  14. Effects of surfactants on bacteria and the bacterial degradation of alkanes in crude oil

    Energy Technology Data Exchange (ETDEWEB)

    Bruheim, Per

    1998-12-31

    This thesis investigates the effects of surfactants on the bacterial degradation of alkanes in crude oil. Several alkane oxidising Gram positive and Gram negative were tested for their abilities to oxidise alkanes in crude oil emulsified with surfactants. The surfactants used to make the oil in water emulsions were either of microbial or chemical origin. Oxidation rates of resting bacteria oxidising various crude oil in water emulsions were measured by Warburg respirometry. The emulsions were compared with non-emulsified oil to see which was the preferred substrate. The bacteria were pregrown to both the exponential and stationary phase of growth before harvesting and preparation for the Warburg experiments. 123 refs., 4 figs., 14 tabs.

  15. Mie potentials for phase equilibria calculations: application to alkanes and perfluoroalkanes.

    Science.gov (United States)

    Potoff, Jeffrey J; Bernard-Brunel, Damien A

    2009-11-05

    Transferable united-atom force fields, based on n - 6 Lennard-Jones potentials, are presented for normal alkanes and perfluorocarbons. It is shown that by varying the repulsive exponent the range of the potential can be altered, leading to improved predictions of vapor pressures while also reproducing saturated liquid densities to high accuracy. Histogram-reweighting Monte Carlo simulations in the grand canonical ensemble are used to determine the vapor liquid coexistence curves, vapor pressures, heats of vaporization, and critical points for normal alkanes methane through tetradecane, and perfluorocarbons perfluoromethane through perfluorooctane. For all molecules studied, saturated liquid densities are reproduced to within 1% of experiment. Vapor pressures for normal alkanes and perfluorocarbons were predicted to within 3% and 6% of experiment, respectively. Calculations performed for binary mixture vapor-liquid equilibria for propane + pentane show excellent agreement with experiment, while slight deviations are observed for the ethane + perfluoroethane mixture.

  16. Separation of Primary Alcohols and Saturated Alkanes from Fisher-Tropsch Synthesis Products

    Institute of Scientific and Technical Information of China (English)

    Suqiao Li; Zhongli Tang⁎; Fujun Zhou; Wenbin Li; Xigang Yuan

    2014-01-01

    abstract A method for separating primary alcohols and saturated alkanes from the products of Fisher-Tropsch synthesis is developed. The separation scheme consists of three steps:(1) the raw material is pre-separated by fractional distillation into four fractions according to normal boiling points;(2) appropriate extractants are selected to sep-arate the primary alcohols from the saturated alkanes in each fraction;(3) the extractants are recovered by azeotropic distillation and the primary alcohols in the extract phase are purified. Based on the proposed method, the total recovery rates of the primary alcohols and the saturated alkanes are 86.23%and 84.62%respectively. © 2014 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. Al rights reserved.

  17. Condensing complex atmospheric chemistry mechanisms. 1: The direct constrained approximate lumping (DCAL) method applied to alkane photochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Wang, S.W.; Georgopoulos, P.G. [Environmental and Occupational Health Sciences Inst., Piscataway, NJ (United States); Li, G.; Rabitz, H. [Princeton Univ., NJ (United States). Dept. of Chemistry

    1998-07-01

    Atmospheric chemistry mechanisms are the most computationally intensive components of photochemical air quality simulation models (PAQSMs). The development of a photochemical mechanism, that accurately describes atmospheric chemistry while being computationally efficient for use in PAQSMs, is a difficult undertaking that has traditionally been pursued through semiempirical (diagnostic) lumping approaches. The limitations of these diagnostic approaches are often associated with inaccuracies due to the fact that the lumped mechanisms have typically been optimized to fit the concentration profile of a specific species. Formal mathematical methods for model reduction have the potential (demonstrated through past applications in other areas) to provide very effective solutions to the need for computational efficiency combined with accuracy. Such methods, that can be used to condense a chemical mechanism, include kinetic lumping and domain separation. An application of the kinetic lumping method, using the direct constrained approximately lumping (DCAL) approach, to the atmospheric photochemistry of alkanes is presented in this work. It is shown that the lumped mechanism generated through the application of the DCAL method has the potential to overcome the limitations of existing semiempirical approaches, especially in relation to the consistent and accurate calculation of the time-concentration profiles of multiple species.

  18. Standoffish perhaps, but successful as well: evidence that avoidant attachment can be beneficial in professional tennis and computer science.

    Science.gov (United States)

    Ein-Dor, Tsachi; Reizer, Abira; Shaver, Phillip R; Dotan, Eyal

    2012-06-01

    Attachment-related avoidance and anxiety have repeatedly been associated with poorer adjustment in various social, emotional, and behavioral domains. We examined 2 domains in which avoidant individuals might be better equipped than their less avoidant peers to succeed and be satisfied--professional singles tennis and computer science. These fields may reward self-reliance, independence, and the ability to work without proximal social support from loved ones. In study 1, we followed 58 professional singles tennis players for 16 months and found that scores on attachment-related avoidance predicted a higher ranking, above and beyond the contributions of training and coping resources. In study 2, we sampled 100 students and found that those who scored higher on avoidance were happier with their choice of computer science as a career than those who scored lower on avoidance. Results are discussed in relation to the possible adaptive functions of certain personality characteristics often viewed as undesirable.

  19. Homology modeling and protein engineering of alkane monooxygenase in Burkholderia thailandensis MSMB121: in silico insights.

    Science.gov (United States)

    Jain, Chakresh Kumar; Gupta, Money; Prasad, Yamuna; Wadhwa, Gulshan; Sharma, Sanjeev Kumar

    2014-07-01

    The degradation of hydrocarbons plays an important role in the eco-balancing of petroleum products, pesticides and other toxic products in the environment. The degradation of hydrocarbons by microbes such as Geobacillus thermodenitrificans, Burkhulderia, Gordonia sp. and Acinetobacter sp. has been studied intensively in the literature. The present study focused on the in silico protein engineering of alkane monooxygenase (ladA)-a protein involved in the alkane degradation pathway. We demonstrated the improvement in substrate binding energy with engineered ladA in Burkholderia thailandensis MSMB121. We identified an ortholog of ladA monooxygenase found in B. thailandensis MSMB121, and showed it to be an enzyme involved in an alkane degradation pathway studied extensively in Geobacillus thermodenitrificans. Homology modeling of the three-dimensional structure of ladA was performed with a crystal structure (protein databank ID: 3B9N) as a template in MODELLER 9v11, and further validated using PROCHECK, VERIFY-3D and WHATIF tools. Specific amino acids were substituted in the region corresponding to amino acids 305-370 of ladA protein, resulting in an enhancement of binding energy in different alkane chain molecules as compared to wild protein structures in the docking experiments. The substrate binding energy with the protein was calculated using Vina (Implemented in VEGAZZ). Molecular dynamics simulations were performed to study the dynamics of different alkane chain molecules inside the binding pockets of wild and mutated ladA. Here, we hypothesize an improvement in binding energies and accessibility of substrates towards engineered ladA enzyme, which could be further facilitated for wet laboratory-based experiments for validation of the alkane degradation pathway in this organism.

  20. Phase Equilibria of Water/CO2 and Water/n-Alkane Mixtures from Polarizable Models.

    Science.gov (United States)

    Jiang, Hao; Economou, Ioannis G; Panagiotopoulos, Athanassios Z

    2017-02-16

    Phase equilibria of water/CO2 and water/n-alkane mixtures over a range of temperatures and pressures were obtained from Monte Carlo simulations in the Gibbs ensemble. Three sets of Drude-type polarizable models for water, namely the BK3, GCP, and HBP models, were combined with a polarizable Gaussian charge CO2 (PGC) model to represent the water/CO2 mixture. The HBP water model describes hydrogen bonds between water and CO2 explicitly. All models underestimate CO2 solubility in water if standard combining rules are used for the dispersion interactions between water and CO2. With the dispersion parameters optimized to phase compositions, the BK3 and GCP models were able to represent the CO2 solubility in water, however, the water composition in CO2-rich phase is systematically underestimated. Accurate representation of compositions for both water- and CO2-rich phases cannot be achieved even after optimizing the cross interaction parameters. By contrast, accurate compositions for both water- and CO2-rich phases were obtained with hydrogen bonding parameters determined from the second virial coefficient for water/CO2. Phase equilibria of water/n-alkane mixtures were also studied using the HBP water and an exponenial-6 united-atom n-alkanes model. The dispersion interactions between water and n-alkanes were optimized to Henry's constants of methane and ethane in water. The HBP water and united-atom n-alkane models underestimate water content in the n-alkane-rich phase; this underestimation is likely due to the neglect of electrostatic and induction energies in the united-atom model.

  1. Distractor Evoked Deviations of Saccade Trajectory Are Modulated by Fixation Activity in the Superior Colliculus: Computational and Behavioral Evidence

    OpenAIRE

    Zhiguo Wang; Jan Theeuwes

    2014-01-01

    Previous studies have shown that saccades may deviate towards or away from task irrelevant visual distractors. This observation has been attributed to active suppression (inhibition) of the distractor location unfolding over time: early in time inhibition at the distractor location is incomplete causing deviation towards the distractor, while later in time when inhibition is complete the eyes deviate away from the distractor. In a recent computational study, Wang, Kruijne and Theeuwes propose...

  2. Decision-making in stimulant and opiate addicts in protracted abstinence: evidence from computational modeling with pure users

    OpenAIRE

    2014-01-01

    Substance dependent individuals (SDI) often exhibit decision-making deficits; however, it remains unclear whether the nature of the underlying decision-making processes is the same in users of different classes of drugs and whether these deficits persist after discontinuation of drug use. We used computational modeling to address these questions in a unique sample of relatively pure amphetamine-dependent (N=38) and heroin-dependent individuals (N=43) who were currently in protracted abstinenc...

  3. Oil and gas potential assessment for coal measure source rocks on absolute concentration of n-alkanes and aromatic hydrocarbons

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Absolute concentration of normal alkanes(n-alkanes) and aromatic hydrocarbons in bitumen extracted from source rocks in the period of thermodegradation from Turpan-Hami Basin suggests that aromatic hydrocarbons are dominant in coal and carbargilite while n-alkanes are dominant in mudstones. Bulkrock analysis and gas chromatograph/mass spectrum(GC-MS) of source rocks shows aromatic hydrocarbons are dominant in total ion chromatograms(TIC) of samples with poor perhydrous macerals while n-alkanes are dominant in TICs of samples with abundant perhydrous macerals. The identification of oil-prone and gas prone property based on GC-MS of bitumen "A" together with bulkrock analysis indicates that source rocks from Shengbei area are more oil-prone while source rocks from Qiudong and Xiaocaohu areas are more gas-prone,coinciding with the distribution of oil and gas reservoirs in Taibei Sag. Ratios used to identify oil-prone and gas-prone property for source rocks from Turpan Basin are proposed:n-alkanes >110 μg·mg-1,aromatics <15 μg·mg-1,and n-alkanes/aromatics >8 for oil-prone source rock bitumen while n-alkanes<82 μg·mg-1,aromatics >40 μg·mg-1,and n-alkanes/aromatics <1.5 for gas-prone source rock bitumen.

  4. Reveal of small alkanes and isomers using calculated core and valence binding energy spectra and total momentum cross sections

    CERN Document Server

    Yang, Zejin

    2013-01-01

    The present study revealed quantum mechanically that the C1s binding energy spectra of the small alkanes (upto six carbons) provide a clear picture of isomeric chemical shift in linear alkanes and branched isomers, whereas the valence binding energy spectra contain more sensitive information regarding the length of the carbon chains. Total momentum cross sections of the alkanes exhibit the information of the chain length as well as constitutional isomers of the small alkanes. The C1s binding energies of small alkanes (including isomers) are position specific and the terminal carbons have the lowest energies. The length of an alkane chain does not apparently affect the C1s energies so that the terminal carbons (289.11 eV) of pentane are almost the same as those of hexane. The valence binding energy spectra of the alkanes are characterized by inner valence and outer valence regions which are separated by an energy gap at approximately 17 eV. The intensities of the total momentum cross sections of the alkanes ar...

  5. Alkane-degrading bacteria at the soil-litter interface: comparing isolates with T-RFLP-based community profiles.

    Science.gov (United States)

    Giebler, Julia; Wick, Lukas Y; Chatzinotas, Antonis; Harms, Hauke

    2013-10-01

    Alkane-degrading bacteria were isolated from uncontaminated soil microcosms, which had been incubated with maize litter as natural alkane source. The isolates served to understand spatio-temporal community changes at the soil-litter interface, which had been detected using alkB as a functional marker gene for bacterial alkane degraders. To obtain a large spectrum of isolates, liquid subcultivation was combined with a matrix-assisted enrichment (Teflon membranes, litter). Elevated cell numbers of alkane degraders were detected by most probable number counting indicating enhanced alkane degradation potential in soil in response to litter treatment. Partial 16S rRNA gene sequencing of 395 isolates revealed forty different phylogenetic groups [operational taxonomic units (OTUs)] and spatio-temporal shifts in community composition. Ten OTUs comprised so far unknown alkane degraders, and five OTUs represented putative new bacterial genera. The combination of enrichment methods yielded a higher diversity of isolates than liquid subcultivation alone. Comparison of 16S rRNA gene T-RFLP profiles indicated that many alkane degraders present in the enrichments were not detectable in the DNA extracts from soil microcosms. These possibly rare specialists might represent a seed bank for the alkane degradation capacity in uncontaminated soil. This relevant ecosystem function can be fostered by the formation of the soil-litter interface.

  6. QSPR models based on molecular mechanics and quantum chemical calculations. 2. Thermodynamic properties of alkanes, alcohols, polyols, and ethers

    DEFF Research Database (Denmark)

    Dyekjær, Jane Dannow; Jonsdottir, Svava Osk

    2003-01-01

    for alkanes, alcohols, diols, ethers, and oxyalcohols, including cyclic alkanes and alcohols. Several good models, having good predictability, have been developed. To enhance the applicability of the QSPR models, simpler expressions for each descriptor have also been developed. This allows for the prediction...

  7. Separating and characterizing functional alkane degraders from crude-oil-contaminated sites via magnetic nanoparticle-mediated isolation.

    Science.gov (United States)

    Wang, Xinzi; Zhao, Xiaohui; Li, Hanbing; Jia, Jianli; Liu, Yueqiao; Ejenavi, Odafe; Ding, Aizhong; Sun, Yujiao; Zhang, Dayi

    Uncultivable microorganisms account for over 99% of all species on the planet, but their functions are yet not well characterized. Though many cultivable degraders for n-alkanes have been intensively investigated, the roles of functional n-alkane degraders remain hidden in the natural environment. This study introduces the novel magnetic nanoparticle-mediated isolation (MMI) technology in Nigerian soils and successfully separates functional microbes belonging to the families Oxalobacteraceae and Moraxellaceae, which are dominant and responsible for alkane metabolism in situ. The alkR-type n-alkane monooxygenase genes, instead of alkA- or alkP-type, were the key functional genes involved in the n-alkane degradation process. Further physiological investigation via a BIOLOG PM plate revealed some carbon (Tween 20, Tween 40 and Tween 80) and nitrogen (tyramine, l-glutamine and d-aspartic acid) sources promoting microbial respiration and n-alkane degradation. With further addition of promoter carbon or nitrogen sources, the separated functional alkane degraders significantly improved n-alkane biodegradation rates. This suggests that MMI is a promising technology for separating functional microbes from complex microbiota, with deeper insight into their ecological functions and influencing factors. The technique also broadens the application of the BIOLOG PM plate for physiological research on functional yet uncultivable microorganisms.

  8. Understanding the Role of Sodium during Adsorption: A Force Field for Alkanes in Sodium-Exchanged Faujasites.

    NARCIS (Netherlands)

    Calero, S.; Dubbeldam, D.; Krishna, R.; Smit, B.; Vlugt, T.J.H.; Denayer, J.F.M.; Martens, J.A.; Maesen, T.L.M.

    2004-01-01

    We have developed a united atom force field able to accurately describe the adsorption properties of linear alkanes in the sodium form of FAU-type zeolites. This force field successfully reproduces experimental adsorption properties of n-alkanes over a wide range of sodium cation densities, temperat

  9. Alkane sorption in molecular sieves: The contribution of ordering, intermolecular interactions and sorption on Brondsted acid sites

    NARCIS (Netherlands)

    Eder, Florian; Lercher, Johannes A.

    1997-01-01

    Distinct molecular ordering of sorbed alkanes is observed in MFI zeolites when the chain length of the alkane is similar to the length of the zig-zag channels (i.e., with n-hexane and n-heptane). In contrast, sorbate-sorbate interactions lead to an increase of the heat of adsorption with increasing

  10. Thermal non-oxidative aromatization of light alkanes catalyzed by gallium nitride.

    Science.gov (United States)

    Li, Lu; Mu, Xiaoyue; Liu, Wenbo; Kong, Xianghua; Fan, Shizhao; Mi, Zetian; Li, Chao-Jun

    2014-12-15

    The thermal catalytic activity of GaN in non-oxidative alkane dehydroaromatization has been discovered for the first time. The origin of the catalytic activity was studied experimentally and theoretically. Commercially available GaN powders with a wurtzite crystal structure showed superior stability and reactivity for converting light alkanes, including methane, propane, n-butane, n-hexane and cyclohexane into benzene at an elevated temperature with high selectivity. The catalyst is highly robust and can be used repeatedly without noticeable deactivation.

  11. Thermodynamic functions of formation of n-alkane complexes with crystalline urea

    Energy Technology Data Exchange (ETDEWEB)

    Tolmachev, V.V.; Semenov, L.V.; Gaile, A.A.; Proskuryakov, V.A.

    1987-07-10

    For optimization of the conditions of deparaffination of petroleum fractions with the aid of urea, with the composition of the feedstock taken into account, it is important to know the equilibrium constants of formation of complexes of urea with n-alkanes differing in the number of carbon atoms in their molecules, as functions of temperature. In this investigation they obtained experimental data necessary for calculating the thermodynamic functions of formation of n-alkane complexes with crystalline urea up to the decomposition temperature, using Kirchhoff's equations.

  12. Homolytic Bond Dissociation Enthalpies of C C and C-H Bonds in Highly Crowded Alkanes

    Institute of Scientific and Technical Information of China (English)

    ZHU Chen; RUI Lei; FU Yao

    2008-01-01

    The homolytic C-C and C--H bond dissociation enthalpyies (BDE) of highly crowded alkanes were calcu- lated by using an ONIOM-G3B3 method. Geometric parameters such as bond length, bond angle and molecular volume were carefully investigated, as most of the acyclic alkanes in this study were not yet synthesized. These pa-rameters reflect the influence of steric effect on BDE. Good correlations were found between the rapid decrease of BDE and the increase of molecular volumes. The correlations can be applied to the prediction of the possible exis-tence of many highly strained compounds.

  13. Regioselective alkane hydroxylation with a mutant CYP153A6 enzyme

    Science.gov (United States)

    Koch, Daniel J.; Arnold, Frances H.

    2013-01-29

    Cytochrome P450 CYP153A6 from Myobacterium sp. strain HXN1500 was engineered using in-vivo directed evolution to hydroxylate small-chain alkanes regioselectively. Mutant CYP153A6-BMO1 selectively hydroxylates butane and pentane at the terminal carbon to form 1-butanol and 1-pentanol, respectively, at rates greater than wild-type CYP153A6 enzymes. This biocatalyst is highly active for small-chain alkane substrates and the regioselectivity is retained in whole-cell biotransformations.

  14. Measurement and modelling of hydrogen bonding in 1-alkanol plus n-alkane binary mixtures

    DEFF Research Database (Denmark)

    von Solms, Nicolas; Jensen, Lars; Kofod, Jonas L.;

    2007-01-01

    Two equations of state (simplified PC-SAFT and CPA) are used to predict the monomer fraction of 1-alkanols in binary mixtures with n-alkanes. It is found that the choice of parameters and association schemes significantly affects the ability of a model to predict hydrogen bonding in mixtures, even...... studies, which is clarified in the present work. New hydrogen bonding data based on infrared spectroscopy are reported for seven binary mixtures of alcohols and alkanes. (C) 2007 Elsevier B.V. All rights reserved....

  15. Classification of vegetable oils according to their botanical origin using n-alkane profiles established by GC-MS.

    Science.gov (United States)

    Troya, F; Lerma-García, M J; Herrero-Martínez, J M; Simó-Alfonso, E F

    2015-01-15

    n-Alkane profiles established by gas chromatography-mass spectrometry (GC-MS) were used to classify vegetable oils according to their botanical origin. The n-alkanes present in corn, grapeseed, hazelnut, olive, peanut and sunflower oils were isolated by means of alkaline hydrolysis followed by silica gel column chromatography of the unsaponifiable fractions. The n-alkane fraction was constituted mainly of n-alkanes in the range C8-C35, although only those most abundant (15 n-alkanes, from 21 to 35 carbon No.) were used as original variables to construct linear discriminant analysis (LDA) models. Ratios of the peak areas selected by pairs were used as predictors. All the oils were correctly classified according to their botanical origin, with assignment probabilities higher than 95%, using an LDA model.

  16. Enhanced translocation and growth of Rhodococcus erythropolis PR4 in the alkane phase of aqueous-alkane two phase cultures were mediated by GroEL2 overexpression.

    Science.gov (United States)

    Takihara, Hayato; Ogihara, Jun; Yoshida, Takao; Okuda, Shujiro; Nakajima, Mutsuyasu; Iwabuchi, Noriyuki; Sunairi, Michio

    2014-01-01

    We previously reported that R. erythropolis PR4 translocated from the aqueous to the alkane phase, and then grew in two phase cultures to which long-chain alkanes had been added. This was considered to be beneficial for bioremediation. In the present study, we investigated the proteins involved in the translocation of R. erythropolis PR4. The results of our proteogenomic analysis suggested that GroEL2 was upregulated more in cells that translocated inside of the pristane (C19) phase than in those located at the aqueous-alkane interface attached to the n-dodecane (C12) surface. PR4 (pK4-EL2-1) and PR4 (pK4-ΔEL2-1) strains were constructed to confirm the effects of the upregulation of GroEL2 in translocated cells. The expression of GroEL2 in PR4 (pK4-EL2-1) was 15.5-fold higher than that in PR4 (pK4-ΔEL2-1) in two phase cultures containing C12. The growth and cell surface lipophilicity of PR4 were enhanced by the introduction of pK4-EL2-1. These results suggested that the plasmid overexpression of groEL2 in PR4 (pK4-EL2-1) led to changes in cell localization, enhanced growth, and increased cell surface lipophilicity. Thus, we concluded that the overexpression of GroEL2 may play an important role in increasing the organic solvent tolerance of R. erythropolis PR4 in aqueous-alkane two phase cultures.

  17. On the evidence of extra mixing in models of 8 M⊙ computed with the new solar abundances

    Directory of Open Access Journals (Sweden)

    Scuflaire R.

    2013-03-01

    Full Text Available Stars more massive than about 3M⊙ are known to experience loops in the HR diagram during their core helium burning phase. Except for very massive stars the extent of their loops increases with the stellar mass. We show that a stellar evolution track for a 8M⊙ star computed with the new solar abundances [2] shows only a very tiny loop located near the red giant branch. An overshooting below the convective envelope is required to obtain a H-discontinuity located deep enough in the μ-gradient region and thus to allow the development of a loop in the HR diagram.

  18. Computational evidence for intramolecular hydrogen bonding and nonbonding X···O interactions in 2'-haloflavonols

    Directory of Open Access Journals (Sweden)

    Tânia A. O. Fonseca

    2012-01-01

    Full Text Available The conformational isomerism and stereoelectronic interactions present in 2'-haloflavonols were computationally analyzed. On the basis of the quantum theory of atoms in molecules (QTAIM and natural bond orbital (NBO analysis, the conformer stabilities of 2'-haloflavonols were found to be dictated mainly by a C=O···H–O intramolecular hydrogen bond, but an unusual C–F···H–O hydrogen-bond and intramolecular C–X···O nonbonding interactions are also present in such compounds.

  19. Diversity of alkane degrading bacteria associated with plants in a petroleum oil-contaminated environment and expression of alkane monooxygenase (alkB) genes

    Science.gov (United States)

    Andria, V.; Yousaf, S.; Reichenauer, T. G.; Smalla, K.; Sessitsch, A.

    2009-04-01

    Among twenty-six different plant species, Italian ryegrass (Lolium multiflorum var. Taurus), Birdsfoot trefoil (Lotus corniculatus var. Leo), and the combination of both plants performed well in a petroleum oil contaminated soil. Hydrocarbon degrading bacteria were isolated from the rhizosphere, root interior and shoot interior and subjected to the analysis of 16S rRNA, the 16S and 23S rRNA intergenic spacer region and alkane hydroxylase genes. Higher numbers of culturable, degrading bacteria were associated with Italian ryegrass, which were also characterized by a higher diversity, particularly in the plant interior. Only half of the isolated bacteria hosted known alkane hydroxylase genes (alkB and cytochrome P153-like). Our results indicated that alkB genes have spread through horizontal gene transfer, particularly in the Italian ryegrass rhizosphere, and suggested mobility of catabolic genes between Gram-negative and Gram-positive bacteria. We furthermore studied the colonization behaviour of selected hydrocarbon-degrading strains (comprising an endopyhte and a rhizosphere strain) as well as the expression of their alkane monooxygenase genes in association with Italian ryegrass. Results showed that the endophyte strain better colonized the plant, particularly the plant interior, and also showed higher expression of alkB genes suggesting a more efficient degradation of the pollutant. Furthermore, plants inoculated with the endophyte were better able to grow in the presence of diesel. The rhizosphere strain colonized primarily the rhizosphere and showed low alkB gene expression in the plant interior.

  20. Molecular simulation and macroscopic modeling of the diffusion of hydrogen, carbon monoxide and water in heavy n-alkane mixtures.

    Science.gov (United States)

    Makrodimitri, Zoi A; Unruh, Dominik J M; Economou, Ioannis G

    2012-03-28

    The self-diffusion coefficient of hydrogen (H(2)), carbon monoxide (CO) and water (H(2)O) in n-alkanes was studied by molecular dynamics simulation. Diffusion in a few pure n-alkanes (namely n-C(8), n-C(20), n-C(64) and n-C(96)) was examined. In addition, binary n-C(12)-n-C(96) mixtures with various compositions as well as more realistic five- and six-n-alkane component mixtures were simulated. In all cases, the TraPPE united atom force field was used for the n-alkane molecules. The force field for the mixture of n-alkanes was initially validated against experimental density values and was shown to be accurate. Moreover, macroscopic correlations for predicting diffusion coefficient of H(2), CO and H(2)O in n-alkanes and mixtures of n-alkanes were developed. The functional form of the correlation was based on the rough hard sphere theory (RHS). The correlation was applied to simulation data and an absolute average deviation (AAD) of 5.8% for pure n-alkanes and 3.4% for n-alkane mixtures was obtained. Correlation parameters vary in a systematic way with carbon number and so they can be used to provide predictions in the absence of any experimental or molecular simulation data. Finally, in order to reduce the number of adjustable parameters, for the n-alkane mixtures the "pseudo-carbon number" approach was used. This approach resulted in relatively higher deviation from MD simulation data (AAD of 18.2%); however, it provides a convenient and fast method to predict diffusion coefficients. The correlations developed here are expected to be useful for engineering calculations related to the design of the Gas-to-Liquid process.

  1. Computer technology-based interventions in HIV prevention: state of the evidence and future directions for research

    Science.gov (United States)

    Noar, Seth M.

    2015-01-01

    Computer technology-based interventions (CBIs) represent a promising area for HIV prevention behavioral intervention research. Such programs are a compelling prevention option given their potential for broad reach, customized content, and low cost delivery. The purpose of the current article is to provide a review of the state of the literature on CBIs. First, we define CBIs in HIV prevention and highlight the many advantages of such interventions. Next, we provide an overview of what is currently known regarding the efficacy of CBIs in HIV prevention, focusing on two recent meta-analyses of this literature. Finally, we propose an agenda for future directions for research in the area of CBIs, using the RE-AIM model as an organizing guide. We conclude that with the continued growth of computer technologies, opportunities to apply such technologies in HIV prevention will continue to blossom. Further research is greatly needed to advance an understanding of not only how and under what circumstances CBIs can be efficacious, but also how the reach, adoption, implementation, and maintenance of such programs in clinical and community settings can be achieved. PMID:21287420

  2. Activation of the aryl hydrocarbon receptor by carbaryl: Computational evidence of the ability of carbaryl to assume a planar conformation.

    Science.gov (United States)

    Casado, Susana; Alonso, Mercedes; Herradón, Bernardo; Tarazona, José V; Navas, José

    2006-12-01

    It has been accepted that aryl hydrocarbon receptor (AhR) ligands are compounds with two or more aromatic rings in a coplanar conformation. Although general agreement exists that carbaryl is able to activate the AhR, it has been proposed that such activation could occur through alternative pathways without ligand binding. This idea was supported by studies showing a planar conformation of carbaryl as unlikely. The objective of the present work was to clarify the process of AhR activation by carbaryl. In rat H4IIE cells permanently transfected with a luciferase gene under the indirect control of AhR, incubation with carbaryl led to an increase of luminescence. Ligand binding to the AhR was studied by means of a cell-free in vitro system in which the activation of AhR can occur only by ligand binding. In this system, exposure to carbaryl also led to activation of AhR. These results were similar to those obtained with the AhR model ligand beta-naphthoflavone, although this compound exhibited higher potency than carbaryl in both assays. By means of computational modeling (molecular mechanics and quantum chemical calculations), the structural characteristics and electrostatic properties of carbaryl were described in detail, and it was observed that the substituent at C-1 and the naphthyl ring were not coplanar. Assuming that carbaryl would interact with the AhR through a hydrogen bond, this interaction was studied computationally using hydrogen fluoride as a model H-bond donor. Under this situation, the stabilization energy of the carbaryl molecule would permit it to adopt a planar conformation. These results are in accordance with the mechanism traditionally accepted for AhR activation: Binding of ligands in a planar conformation.

  3. Decision-making in stimulant and opiate addicts in protracted abstinence: evidence from computational modeling with pure users

    Science.gov (United States)

    Ahn, Woo-Young; Vasilev, Georgi; Lee, Sung-Ha; Busemeyer, Jerome R.; Kruschke, John K.; Bechara, Antoine; Vassileva, Jasmin

    2014-01-01

    Substance dependent individuals (SDI) often exhibit decision-making deficits; however, it remains unclear whether the nature of the underlying decision-making processes is the same in users of different classes of drugs and whether these deficits persist after discontinuation of drug use. We used computational modeling to address these questions in a unique sample of relatively “pure” amphetamine-dependent (N = 38) and heroin-dependent individuals (N = 43) who were currently in protracted abstinence, and in 48 healthy controls (HC). A Bayesian model comparison technique, a simulation method, and parameter recovery tests were used to compare three cognitive models: (1) Prospect Valence Learning with decay reinforcement learning rule (PVL-DecayRI), (2) PVL with delta learning rule (PVL-Delta), and (3) Value-Plus-Perseverance (VPP) model based on Win-Stay-Lose-Switch (WSLS) strategy. The model comparison results indicated that the VPP model, a hybrid model of reinforcement learning (RL) and a heuristic strategy of perseverance had the best post-hoc model fit, but the two PVL models showed better simulation and parameter recovery performance. Computational modeling results suggested that overall all three groups relied more on RL than on a WSLS strategy. Heroin users displayed reduced loss aversion relative to HC across all three models, which suggests that their decision-making deficits are longstanding (or pre-existing) and may be driven by reduced sensitivity to loss. In contrast, amphetamine users showed comparable cognitive functions to HC with the VPP model, whereas the second best-fitting model with relatively good simulation performance (PVL-DecayRI) revealed increased reward sensitivity relative to HC. These results suggest that some decision-making deficits persist in protracted abstinence and may be mediated by different mechanisms in opiate and stimulant users. PMID:25161631

  4. Decision-making in stimulant and opiate addicts in protracted abstinence: evidence from computational modeling with pure users

    Directory of Open Access Journals (Sweden)

    Woo-Young eAhn

    2014-08-01

    Full Text Available Substance dependent individuals (SDI often exhibit decision-making deficits; however, it remains unclear whether the nature of the underlying decision-making processes is the same in users of different classes of drugs and whether these deficits persist after discontinuation of drug use. We used computational modeling to address these questions in a unique sample of relatively pure amphetamine-dependent (N=38 and heroin-dependent individuals (N=43 who were currently in protracted abstinence, and in 48 healthy controls. A Bayesian model comparison technique, a simulation method, and parameter recovery tests were used to compare three cognitive models: (1 Prospect Valence Learning with decay reinforcement learning rule (PVL-DecayRI, (2 PVL with delta learning rule (PVL-Delta, and (3 Value-Plus-Perseverance (VPP models based on Win-Stay-Lose-Switch (WSLS strategy. The model comparison results indicated that the VPP model, a hybrid model of reinforcement learning (RL and a heuristic strategy of perseverance had the best post hoc model fit, but the two PVL models showed better simulation performance. Computational modeling results suggested that overall all three groups relied more on RL than on a WSLS strategy. Heroin users displayed reduced loss aversion relative to healthy controls across all three models, which suggests that their decision-making deficits are longstanding (or pre-existing and may be driven by reduced sensitivity to loss. In contrast, amphetamine users showed comparable cognitive functions to healthy controls with the VPP model, whereas the second best-fitting model with relatively good simulation performance (PVL-DecayRI revealed increased reward sensitivity relative to healthy controls. These results suggest that some decision-making deficits persist in protracted abstinence and may be mediated by different mechanisms in opiate and stimulant users.

  5. 破坏计算机信息系统罪的证据研究%Research on the Evidence of the Crime of Destroying Computer Information Systems

    Institute of Scientific and Technical Information of China (English)

    陈荔

    2013-01-01

    随着信息科技的迅速发展,人们对于计算机及网络虚拟生活的依赖程度日益提高,破坏计算机信息系统类犯罪也越来越多,文章从上海检察机关相关案例入手,从电子数据的收集鉴定和审查认定方面探讨破坏计算机信息系统案件类案件在理论和实务中遇到的问题。%With the rapid development of information technology, people's dependence on computer and network virtual life is increasing. The Crime of Destroying Computer Information Systems is also increasing. This article starts from Shanghai prosecution’s case, encountered in both theory and practice problems with forensic and examination of electronic evidence collected from the crime of destroying computer information systems.

  6. Modeling the influence of alkane molecular structure on secondary organic aerosol formation.

    Science.gov (United States)

    Aumont, Bernard; Camredon, Marie; Mouchel-Vallon, Camille; La, Stéphanie; Ouzebidour, Farida; Valorso, Richard; Lee-Taylor, Julia; Madronich, Sasha

    2013-01-01

    Secondary Organic Aerosols (SOA) production and ageing is a multigenerational oxidation process involving the formation of successive organic compounds with higher oxidation degree and lower vapor pressure. Intermediate Volatility Organic Compounds (IVOC) emitted to the atmosphere are expected to be a substantial source of SOA. These emitted IVOC constitute a complex mixture including linear, branched and cyclic alkanes. The explicit gas-phase oxidation mechanisms are here generated for various linear and branched C10-C22 alkanes using the GECKO-A (Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere) and SOA formation is investigated for various homologous series. Simulation results show that both the size and the branching of the carbon skeleton are dominant factors driving the SOA yield. However, branching appears to be of secondary importance for the particle oxidation state and composition. The effect of alkane molecular structure on SOA yields appears to be consistent with recent laboratory observations. The simulated SOA composition shows, however, an unexpected major contribution from multifunctional organic nitrates. Most SOA contributors simulated for the oxidation of the various homologous series are far too reduced to be categorized as highly oxygenated organic aerosols (OOA). On a carbon basis, the OOA yields never exceeded 10% regardless of carbon chain length, molecular structure or ageing time. This version of the model appears clearly unable to explain a large production of OOA from alkane precursors.

  7. Interrogation of Chesapeake Bay sediment microbial communities for intrinsic alkane-utilizing potential under anaerobic conditions.

    Science.gov (United States)

    Johnson, Jamie M; Wawrik, Boris; Isom, Catherine; Boling, Wilford B; Callaghan, Amy V

    2015-02-01

    Based on the transient exposure of Chesapeake Bay sediments to hydrocarbons and the metabolic versatility of known anaerobic alkane-degrading microorganisms, it was hypothesized that distinct Bay sediment communities, governed by geochemical gradients, would have intrinsic alkane-utilizing potential under sulfate-reducing and/or methanogenic conditions. Sediment cores were collected along a transect of the Bay. Community DNA was interrogated via pyrosequencing of 16S rRNA genes, PCR of anaerobic hydrocarbon activation genes, and qPCR of 16S rRNA genes and genes involved in sulfate reduction/methanogenesis. Site sediments were used to establish microcosms amended with n-hexadecane under sulfate-reducing and methanogenic conditions. Sequencing of 16S rRNA genes indicated that sediments associated with hypoxic water columns contained significantly greater proportions of Bacteria and Archaea consistent with syntrophic degradation of organic matter and methanogenesis compared to less reduced sediments. Microbial taxa frequently associated with hydrocarbon-degrading communities were found throughout the Bay, and the genetic potential for hydrocarbon metabolism was demonstrated via the detection of benzyl-(bssA) and alkylsuccinate synthase (assA) genes. Although microcosm studies did not indicate sulfidogenic alkane degradation, the data suggested that methanogenic conversion of alkanes was occurring. These findings highlight the potential role that anaerobic microorganisms could play in the bioremediation of hydrocarbons in the Bay.

  8. Growth of n-alkane films on a single-crystal substrate

    DEFF Research Database (Denmark)

    Wu, Z. U.; Ehrlich, S. N.; Matthies, B.;

    2001-01-01

    The structure and growth mode of alkane films (n-C/sub n/H/sub 2n+2/; n=4, 6, 7) adsorbed on a Ag(111) surface have been investigated by synchrotron X-ray scattering. New models are proposed for the butane (n=4) and hexane (n=6) monolayer and butane bilayer structures. Specular reflectivity scans...

  9. Solvent isotope effects on alkane formation by cyanobacterial aldehyde deformylating oxygenase and their mechanistic implications.

    Science.gov (United States)

    Waugh, Matthew W; Marsh, E Neil G

    2014-09-02

    The reaction catalyzed by cyanobacterial aldehyde deformylating oxygenase is of interest both because of its potential application to the production of biofuels and because of the highly unusual nature of the deformylation reaction it catalyzes. Whereas the proton in the product alkane derives ultimately from the solvent, the identity of the proton donor in the active site remains unclear. To investigate the proton transfer step, solvent isotope effect (SIE) studies were undertaken. The rate of alkane formation was found to be maximal at pH 6.8 and to be the same in D2O or H2O within experimental error, implying that proton transfer is not a kinetically significant step. However, when the ratio of protium to deuterium in the product alkane was measured as a function of the mole fraction of D2O, a (D2O)SIEobs of 2.19 ± 0.02 was observed. The SIE was invariant with the mole fraction of D2O, indicating the involvement of a single protic site in the reaction. We interpret this SIE as most likely arising from a reactant state equilibrium isotope effect on a proton donor with an inverse fractionation factor, for which Φ = 0.45. These observations are consistent with an iron-bound water molecule being the proton donor to the alkane in the reaction.

  10. Chain Length Effects of Linear Alkanes in Zeolite Ferrierite. 1. Sorption and 13C NMR Experiments

    NARCIS (Netherlands)

    Well, van Willy J.M.; Cottin, Xavier; Haan, vde Jan W.; Smit, Berend; Nivarthy, Gautam; Lercher, Johannes A.; Hooff, van Jan H.C.; Santen, van Rutger A.

    1998-01-01

    Temperature-programmed desorption, heat of adsorption, adsorption isotherm, and 13C NMR measurements are used to study the sorption properties of linear alkanes in ferrierite. Some remarkable chain length effects are found in these properties. While propane, n-butane, and n-pentane fill the ferrieri

  11. Iridium complexes of new NCP pincer ligands: catalytic alkane dehydrogenation and alkene isomerization.

    Science.gov (United States)

    Jia, Xiangqing; Zhang, Lei; Qin, Chuan; Leng, Xuebing; Huang, Zheng

    2014-09-28

    Iridium complexes of novel NCP pincer ligands containing pyridine and phosphinite arms have been synthesized. One Ir complex shows good catalytic activity for alkane dehydrogenation, and all complexes are highly active for olefin isomerization. A combination of the Ir complex and a (PNN)Fe pincer complex catalyzes the formation of linear alkylboronates selectively from internal olefins via sequential olefin isomerization-hydroboration.

  12. Stable carbon and hydrogen isotopic fractionations of alkane compounds and crude oil during aerobically microbial degradation

    Institute of Scientific and Technical Information of China (English)

    PENG Xianzhi; ZHANG Gan; CHEN Fanzhong; LIU Guoqing

    2004-01-01

    Normal alkane compounds dodecane, pentadecane, hexadecane, octadecane, tetracosane, isoprenoid alkane pristane and a crude oil sample were aerobically biodegraded with a pure bacterial strain GIM2.5 and white rot fungus Phanerochaete Chrysosporium-1767 to monitor the kinetic fractionation of the molecular stable carbon (δ13C) and hydrogen (δD) isotopes in the course of biodegradation. Both δ13C (V-PDB) and δ D (V-SMOW) remained stable for the standard alkane compounds and n-alkane components (from n-C13 to n-C25) of the crude oil, generally varying in the range of ±0.5‰ and ±5‰ respectively, within the range of the instrumental precisions, especially for those molecularly heavier than n-C16 during microbial degradation. These results indicate that molecular stable carbon and hydrogen isotopic fingerprints can be promising indicators for tracing the sources of petroleum-related contaminants in the environment, especially in the case of severe weathering when they are difficult to be unambiguously identified by the chemical fingerprints alone.

  13. Characteristics of Carbon Isotopes of Alkane Components and Identification Marks of Biogenic Gases in China

    Institute of Scientific and Technical Information of China (English)

    戴金星; 陈英

    1994-01-01

    The carbon isotope composition of alkane component in biogenic gases of China has the following characteristics:with the increase of carbon number of the alkane molecules in biogenic gases, (i) the distribution range of the δ13C values and their main frequency sections become narrower, and both the heaviest and the lightest δ13C boundary values shift to their heavier end; (ii) the δ13C values of ethane and propane in biogenic gases present a positive linear relationship and (iii) the values of δ13C1, δ13C2 and δ13C3 tend to become heavier with the increase of heavy alkane component (C2+3) in biogenic gases. The authors studied the relationship between the δ13C values and the amount of heavy alkane components in biogenic gases (δ13C1 -C2+3(%). δ13C2 -C2+3(%) ,δ13C3-C2+3(%) for the first time and set up the interrelated regression equations between δ13C and C2+3 content (C2+3%), and advance that δ13C1< -55‰ and C2+3<0. 5% are two fine marks for identification of biogenic gases of China. δ13C

  14. Adsorption and diffusion of alkanes in Na-MOR: modeling the effect of the aluminum distribution

    NARCIS (Netherlands)

    Ban, S.; Vlugt, T.J.H.

    2009-01-01

    We investigated the adsorption and the diffusion of alkanes in the sodium-exchanged zeolite Mordenite (Na-MOR) using molecular simulations. MOR-type zeolite consists of main channels (6.5 × 7 Å) oriented along the z crystallographic axis that are connected to small side pockets (3.4 × 4.8 Å). It is

  15. Cool-flame Extinction During N-Alkane Droplet Combustion in Microgravity

    Science.gov (United States)

    Nayagam, Vedha; Dietrich, Daniel L.; Hicks, Michael C.; Williams, Forman A.

    2014-01-01

    Recent droplet combustion experiments onboard the International Space Station (ISS) have revealed that large n-alkane droplets can continue to burn quasi-steadily following radiative extinction in a low-temperature regime, characterized by negative-temperaturecoefficient (NTC) chemistry. In this study we report experimental observations of n-heptane, n-octane, and n-decane droplets of varying initial sizes burning in oxygen/nitrogen/carbon dioxide and oxygen/helium/nitrogen environments at 1.0, 0.7, and 0.5 atmospheric pressures. The oxygen concentration in these tests varied in the range of 14% to 25% by volume. Large n-alkane droplets exhibited quasi-steady low-temperature burning and extinction following radiative extinction of the visible flame while smaller droplets burned to completion or disruptively extinguished. A vapor-cloud formed in most cases slightly prior to or following the "cool flame" extinction. Results for droplet burning rates in both the hot-flame and cool-flame regimes as well as droplet extinction diameters at the end of each stage are presented. Time histories of radiant emission from the droplet captured using broadband radiometers are also presented. Remarkably the "cool flame" extinction diameters for all the three n-alkanes follow a trend reminiscent of the ignition delay times observed in previous studies. The similarities and differences among the n-alkanes during "cool flame" combustion are discussed using simplified theoretical models of the phenomenon

  16. The influence of extraframework aluminum on H-FAU catalyzed cracking of light alkanes

    NARCIS (Netherlands)

    Narbeshuber, T.F.; Brait, A.; Seshan, K.; Lercher, J.A.

    1996-01-01

    The conversion of light linear and branched alkanes on two faujasite samples containing different concentrations of free Brønsted acid sites and extraframework alumina (EFAL) was studied between 733 K and 813 K. Protolytic cracking and bimolecular hydride transfer proceeded solely on Brønsted acid s

  17. Localized diffusive motion on two different time scales in solid alkane nanoparticles

    DEFF Research Database (Denmark)

    Wang, S. K.; Mamontov, E.; Bai, M.

    2010-01-01

    High-energy-resolution quasielastic neutron scattering on three complementary spectrometers has been used to investigate molecular diffusive motion in solid nano- to bulk-sized particles of the alkane n-C32H66. The crystalline-to-plastic and plastic-to-fluid phase transition temperatures are obse...

  18. Technical Note: n-Alkane lipid biomarkers in loess: post-sedimentary or syn-sedimentary?

    Directory of Open Access Journals (Sweden)

    D. Faust

    2012-07-01

    Full Text Available There is an ongoing discussion whether n-alkane biomarkers – and organic matter (OM from loess in general – reflect a syn-sedimentary paleoenvironmental and paleoclimate signal or whether they are significantly a post-sedimentary feature contaminated by root-derived OM. We present first radiocarbon data for the n-alkane fraction of lipid extracts and for the first time luminescence ages for the Middle to Late Weichselian loess-paleosol sequence of Gleina in Saxony, Germany. Comparison of these biomarker ages with sedimentation ages as assessed by optically stimulated luminescence (OSL dating shows that one n-alkane sample features a syn-sedimentary age (14C: 29.2 ± 1.4 kyr cal BP versus OSL: 27.3 ± 3.0 kyr. By contrast, the 14C ages derived from the other n-alkane samples are clearly younger (20.3 ± 0.7 kyr cal BP, 22.1 ± 0.7 kyr cal BP and 29.8 ± 1.4 kyr cal BP than the corresponding OSL ages (26.6 ± 3.1 kyr, 32.0 ± 3.5 kyr and 45.6 ± 5.3 kyr. This finding suggests that a post-sedimentary n-alkane contamination presumably by roots has occurred. In order to estimate the post-sedimentary n-alkane contamination more quantitatively, we applied a 14C mass balance calculation based on the measured pMC (percent modern carbon values, the calculated syn-sedimentary pMC values and pMC values suspected to reflect likely time points of post-sedimentary contamination (current, modern, 3 kyr, 6 kyr and 9 kyr. Accordingly, current and modern root-contamination would account for up to 7%, a 3 kyr old root-contamination for up to 10%, and an Early and Middle Holocene root-contamination for up to 20% of the total sedimentary n-alkane pool. We acknowledge and encourage that these first radiocarbon results need further confirmation both from other loess-paleosol sequences and for different biomarkers, e.g. carboxylic acids or alcohols as further lipid biomarkers.

  19. Calculations of gamma-ray spectral profiles of linear alkanes in the positron annihilation process

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Xiaoguang [Molecular Model Discovery Laboratory, Department of Chemistry and Biotechnology, School of Science, Faculty of Science, Engineering and Technology, Swinburne University of Technology, PO Box 218, Hawthorn, Victoria, 3122 (Australia); School of Physics and Optoelectronic Engineering, Ludong University, Shandong, Yantai, 264025 (China); Wang, Feng, E-mail: fwang@swin.edu.au [Molecular Model Discovery Laboratory, Department of Chemistry and Biotechnology, School of Science, Faculty of Science, Engineering and Technology, Swinburne University of Technology, PO Box 218, Hawthorn, Victoria, 3122 (Australia)

    2014-10-15

    Highlights: • The study calculates gamma-ray profiles for linear alkanes (n up to 12) quantum mechanically;. • “Profile quality” has been defined as the root-mean square deviation (RMSD) between the theoretical and the experimental results in the entire region of the profile. • Excellent agreement with measurements suggests that the theory model is applicable to predict other alkanes such as heptane (C{sub 7}H{sub 16}) etc. • The study suggested that gamma-ray spectra may be more sensitive to study smaller alkanes (and their isomers), rather than larger alkanes (i.e., n > 12). - Abstract: The positron–electron annihilation gamma-ray spectra of linear alkanes C{sub n}H{sub 2n+2} (n = 1–12) have been studied systematically. A profile quality (PQ) parameter, χ, is introduced to assess the agreement between the obtained theoretical profiles and the experimental measurements in the entire region of energy shift of the spectra. Together with the Doppler shift (Δε) of the gamma-ray spectra, the two parameters, χ and Δε, are able to provide a more comprehensive assessment of the calculated gamma-ray spectra with respect to available experiment. Applying the recently developed docking model, the present study determines the positrophilic electrons for individual alkanes from which the gamma-ray spectral profiles are calculated. The results achieve an excellent agreement with experiment, not only with respect to the Doppler shift, but also with respect to the gamma-ray profiles in the photon energy region up to 5 keV. The study further calculates the gamma-ray spectra of other linear alkanes in the series without available experimental measurements, such as heptane (C{sub 7}H{sub 16}), octane (C{sub 8}H{sub 18}), decane (C{sub 10}H{sub 22}) and undecane (C{sub 11}H{sub 24}). The results obtained show a dominance of the positrophilic electrons in the lowest occupied valence orbital (LOVO) in the positron–electron annihilation process, in agreement with

  20. Insights into rapid climate change: A high resolution, compound-specific n-alkane δD study of the 8.2 ka event (Tenaghi Philippon, Greece)

    Science.gov (United States)

    Schemmel, F.; Niedermeyer, E.; Schwab, V.; Pross, J.; Mulch, A.

    2013-12-01

    Despite being characterized as remarkably stable, the Holocene climate has experienced a number of abrupt, relatively short-term climate changes. Arguably the most prominent climate perturbation, the 8.2 ka event, was caused by the catastrophic drainage of the ice-dammed Laurentide ice-lake into the North Atlantic, leading to a severe weakening of thermohaline circulation, causing a decline in temperature and significant changes in atmospheric circulation in the Northern Hemisphere, especially in the North Atlantic realm and Europe. Being located between the climate systems of the higher and lower latitudes, the Mediterranean region is particularly susceptible to rapid climate change. Available proxy data and climate models provide first-order insight into the impact of the 8.2 ka event in this area but often lack the temporal resolution to supply information about changes in seasonality, hence severely hindering the understanding of rapid climate changes and revealing the need for high resolution terrestrial archives. Here, we present a multi-proxy, high resolution stable isotope study across the 8.2 ka event on a peat core from the classical site of Tenaghi Philippon (NE Greece). We aim to characterize the effects of changing temperature and rainfall patterns by using compound-specific δD values of the long-chain n-alkanes as a proxy for terrestrial (summer) precipitation. We compare changes in hydrogen isotopic composition to the concentration of the long-chain n-alkanes as well as to δ13Cbulk measurements of the organic material and high-resolution palynomorphic data from the same core. Analysis of 35 samples of telmatic peat shows significant decreases in concentration of the long-chain n-alkanes along with strong positive shifts in δD (over 40 ‰ in δDC29) during the 8.2 ka event. The general trend of δD of the n-Alkanes n-C27, n-C29 and n-C31 coincides with changes in δ13Cbulk, and to some degree reflects changes in moisture availability. We attribute

  1. Charge Transport in 4 nm Molecular Wires with Interrupted Conjugation: Combined Experimental and Computational Evidence for Thermally Assisted Polaron Tunneling.

    Science.gov (United States)

    Taherinia, Davood; Smith, Christopher E; Ghosh, Soumen; Odoh, Samuel O; Balhorn, Luke; Gagliardi, Laura; Cramer, Christopher J; Frisbie, C Daniel

    2016-04-26

    We report the synthesis, transport measurements, and electronic structure of conjugation-broken oligophenyleneimine (CB-OPI 6) molecular wires with lengths of ∼4 nm. The wires were grown from Au surfaces using stepwise aryl imine condensation reactions between 1,4-diaminobenzene and terephthalaldehyde (1,4-benzenedicarbaldehyde). Saturated spacers (conjugation breakers) were introduced into the molecular backbone by replacing the aromatic diamine with trans-1,4-diaminocyclohexane at specific steps during the growth processes. FT-IR and ellipsometry were used to follow the imination reactions on Au surfaces. Surface coverages (∼4 molecules/nm(2)) and electronic structures of the wires were determined by cyclic voltammetry and UV-vis spectroscopy, respectively. The current-voltage (I-V) characteristics of the wires were acquired using conducting probe atomic force microscopy (CP-AFM) in which an Au-coated AFM probe was brought into contact with the wires to form metal-molecule-metal junctions with contact areas of ∼50 nm(2). The low bias resistance increased with the number of saturated spacers, but was not sensitive to the position of the spacer within the wire. Temperature dependent measurements of resistance were consistent with a localized charge (polaron) hopping mechanism in all of the wires. Activation energies were in the range of 0.18-0.26 eV (4.2-6.0 kcal/mol) with the highest belonging to the fully conjugated OPI 6 wire and the lowest to the CB3,5-OPI 6 wire (the wire with two saturated spacers). For the two other wires with a single conjugation breaker, CB3-OPI 6 and CB5-OPI 6, activation energies of 0.20 eV (4.6 kcal/mol) and 0.21 eV (4.8 kcal/mol) were found, respectively. Computational studies using density functional theory confirmed the polaronic nature of charge carriers but predicted that the semiclassical activation energy of hopping should be higher for CB-OPI molecular wires than for the OPI 6 wire. To reconcile the experimental and

  2. Yas3p, an Opi1 Family Transcription Factor, Regulates Cytochrome P450 Expression in Response to n-Alkanes in Yarrowia lipolytica*

    OpenAIRE

    Hirakawa, Kiyoshi; Kobayashi, Satoshi; Inoue, Takuro; Endoh-Yamagami, Setsu; Fukuda, Ryouichi; Ohta, Akinori

    2009-01-01

    In the alkane-assimilating yeast Yarrowia lipolytica, the expression of ALK1, a gene encoding cytochrome P450 that catalyzes the first step of n-alkane oxidation, is induced by n-alkanes. We previously demonstrated that two basic helix-loop-helix proteins, Yas1p and Yas2p, activate the transcription of ALK1 in an alkane-dependent manner by forming a heterocomplex and binding to alkane-responsive element 1 (ARE1), a cis-acting element in the ALK1 promoter. Here we i...

  3. Enhanced biodegradation of alkane hydrocarbons and crude oil by mixed strains and bacterial community analysis.

    Science.gov (United States)

    Chen, Yu; Li, Chen; Zhou, Zhengxi; Wen, Jianping; You, Xueyi; Mao, Youzhi; Lu, Chunzhe; Huo, Guangxin; Jia, Xiaoqiang

    2014-04-01

    In this study, two strains, Acinetobacter sp. XM-02 and Pseudomonas sp. XM-01, were isolated from soil samples polluted by crude oil at Bohai offshore. The former one could degrade alkane hydrocarbons (crude oil and diesel, 1:4 (v/v)) and crude oil efficiently; the latter one failed to grow on alkane hydrocarbons but could produce rhamnolipid (a biosurfactant) with glycerol as sole carbon source. Compared with pure culture, mixed culture of the two strains showed higher capability in degrading alkane hydrocarbons and crude oil of which degradation rate were increased from 89.35 and 74.32 ± 4.09 to 97.41 and 87.29 ± 2.41 %, respectively. In the mixed culture, Acinetobacter sp. XM-02 grew fast with sufficient carbon source and produced intermediates which were subsequently utilized for the growth of Pseudomonas sp. XM-01 and then, rhamnolipid was produced by Pseudomonas sp. XM-01. Till the end of the process, Acinetobacter sp. XM-02 was inhibited by the rapid growth of Pseudomonas sp. XM-01. In addition, alkane hydrocarbon degradation rate of the mixed culture increased by 8.06 to 97.41 % compared with 87.29 % of the pure culture. The surface tension of medium dropping from 73.2 × 10(-3) to 28.6 × 10(-3) N/m. Based on newly found cooperation between the degrader and the coworking strain, rational investigations and optimal strategies to alkane hydrocarbons biodegradation were utilized for enhancing crude oil biodegradation.

  4. Diverse Bacterial Groups Contribute to the Alkane Degradation Potential of Chronically Polluted Subantarctic Coastal Sediments.

    Science.gov (United States)

    Guibert, Lilian M; Loviso, Claudia L; Borglin, Sharon; Jansson, Janet K; Dionisi, Hebe M; Lozada, Mariana

    2016-01-01

    We aimed to gain insight into the alkane degradation potential of microbial communities from chronically polluted sediments of a subantarctic coastal environment using a combination of metagenomic approaches. A total of 6178 sequences annotated as alkane-1-monooxygenases (EC 1.14.15.3) were retrieved from a shotgun metagenomic dataset that included two sites analyzed in triplicate. The majority of the sequences binned with AlkB described in Bacteroidetes (32 ± 13 %) or Proteobacteria (29 ± 7 %), although a large proportion remained unclassified at the phylum level. Operational taxonomic unit (OTU)-based analyses showed small differences in AlkB distribution among samples that could be correlated with alkane concentrations, as well as with site-specific variations in pH and salinity. A number of low-abundance OTUs, mostly affiliated with Actinobacterial sequences, were found to be only present in the most contaminated samples. On the other hand, the molecular screening of a large-insert metagenomic library of intertidal sediments from one of the sampling sites identified two genomic fragments containing novel alkB gene sequences, as well as various contiguous genes related to lipid metabolism. Both genomic fragments were affiliated with the phylum Planctomycetes, and one could be further assigned to the genus Rhodopirellula due to the presence of a partial sequence of the 23S ribosomal RNA (rRNA) gene. This work highlights the diversity of bacterial groups contributing to the alkane degradation potential and reveals patterns of functional diversity in relation with environmental stressors in a chronically polluted, high-latitude coastal environment. In addition, alkane biodegradation genes are described for the first time in members of Planctomycetes.

  5. Diverse Bacterial Groups Contribute to the Alkane Degradation Potential of Chronically Polluted Subantarctic Coastal Sediments

    Energy Technology Data Exchange (ETDEWEB)

    Guibert, Lilian M.; Loviso, Claudia L.; Borglin, Sharon; Jansson, Janet K.; Dionisi, Hebe M.; Lozada, Mariana

    2015-11-07

    We aimed to gain insight into the alkane degradation potential of microbial communities from chronically polluted sediments of a subantarctic coastal environment using a combination of metagenomic approaches. A total of 6178 sequences annotated as alkane-1-monooxygenases (EC 1.14.15.3) were retrieved from a shotgun metagenomic dataset that included two sites analyzed in triplicate. The majority of the sequences binned with AlkB described in Bacteroidetes (32 ± 13 %) or Proteobacteria (29 ± 7 %), although a large proportion remained unclassified at the phylum level. Operational taxonomic unit (OTU)-based analyses showed small differences in AlkB distribution among samples that could be correlated with alkane concentrations, as well as with site-specific variations in pH and salinity. A number of low-abundance OTUs, mostly affiliated with Actinobacterial sequences, were found to be only present in the most contaminated samples. On the other hand, the molecular screening of a large-insert metagenomic library of intertidal sediments from one of the sampling sites identified two genomic fragments containing novel alkB gene sequences, as well as various contiguous genes related to lipid metabolism. Both genomic fragments were affiliated with the phylum Planctomycetes, and one could be further assigned to the genus Rhodopirellula due to the presence of a partial sequence of the 23S ribosomal RNA (rRNA) gene. This work highlights the diversity of bacterial groups contributing to the alkane degradation potential and reveals patterns of functional diversity in relation with environmental stressors in a chronically polluted, high-latitude coastal environment. In addition, alkane biodegradation genes are described for the first time in members of Planctomycetes.

  6. Distractor evoked deviations of saccade trajectory are modulated by fixation activity in the superior colliculus: computational and behavioral evidence.

    Directory of Open Access Journals (Sweden)

    Zhiguo Wang

    Full Text Available Previous studies have shown that saccades may deviate towards or away from task irrelevant visual distractors. This observation has been attributed to active suppression (inhibition of the distractor location unfolding over time: early in time inhibition at the distractor location is incomplete causing deviation towards the distractor, while later in time when inhibition is complete the eyes deviate away from the distractor. In a recent computational study, Wang, Kruijne and Theeuwes proposed an alternative theory that the lateral interactions in the superior colliculus (SC, which are characterized by short-distance excitation and long-distance inhibition, are sufficient for generating both deviations towards and away from distractors. In the present study, we performed a meta-analysis of the literature, ran model simulations and conducted two behavioral experiments to further explore this unconventional theory. Confirming predictions generated by the model simulations, the behavioral experiments show that a saccades deviate towards close distractors and away from remote distractors, and b the amount of deviation depends on the strength of fixation activity in the SC, which can be manipulated by turning off the fixation stimulus before or after target onset (Experiment 1, or by varying the eccentricity of the target and distractor (Experiment 2.

  7. Distractor evoked deviations of saccade trajectory are modulated by fixation activity in the superior colliculus: computational and behavioral evidence.

    Science.gov (United States)

    Wang, Zhiguo; Theeuwes, Jan

    2014-01-01

    Previous studies have shown that saccades may deviate towards or away from task irrelevant visual distractors. This observation has been attributed to active suppression (inhibition) of the distractor location unfolding over time: early in time inhibition at the distractor location is incomplete causing deviation towards the distractor, while later in time when inhibition is complete the eyes deviate away from the distractor. In a recent computational study, Wang, Kruijne and Theeuwes proposed an alternative theory that the lateral interactions in the superior colliculus (SC), which are characterized by short-distance excitation and long-distance inhibition, are sufficient for generating both deviations towards and away from distractors. In the present study, we performed a meta-analysis of the literature, ran model simulations and conducted two behavioral experiments to further explore this unconventional theory. Confirming predictions generated by the model simulations, the behavioral experiments show that a) saccades deviate towards close distractors and away from remote distractors, and b) the amount of deviation depends on the strength of fixation activity in the SC, which can be manipulated by turning off the fixation stimulus before or after target onset (Experiment 1), or by varying the eccentricity of the target and distractor (Experiment 2).

  8. review of the archaeological evidence for food plants from the British Isles: an example of the use of the Archaeobotanical Computer Database (ABCD

    Directory of Open Access Journals (Sweden)

    Philippa Tomlinson

    1996-09-01

    Full Text Available The Archaeobotanical Computer Database is an electronic compilation of information about remains of plants from archaeological deposits throughout the British Isles. For the first time, this wealth of published data, much of it post-dating Godwin's (1975 History of the British Flora has been brought together in a form in which the user can explore the history of a particular species or group of plants, or investigate the flora and vegetation of a particular archaeological period or part of the British Isles. The database contains information about the sites, deposits and samples from which the remains in question have been recovered, together with details of the plant parts identified and their mode of preservation. It also provides some interpretative guidance concerning the integrity of contexts and the reliability of dating as an aid to judging the quality of the data available. In this paper the compilers of the ABCD make use of the database in order to review the archaeological evidence for food plants in the British Isles. The paper begins with a definition of its scope, examining the concept of a "food plant" and the taphonomy of plant remains on British archaeological sites. It then summarises the principal changes in food plants from the prehistoric period to post-medieval times. The body of the paper is a detailed discussion of the evidence for the use of berries, other fruits, vegetables, pulses, herbs and flavourings, oil plants, cereals and nuts. Finally, the paper compares the archaeological evidence with that known from documentary sources. Readers will be able to view the archaeological evidence as distribution maps and will be able to explore aspects of the database online, enabling queries by taxa, site or worker. Instructions on obtaining electronic copies of the database tables and registering as an ABCD user are also included.

  9. Polycyclic Aromatic Hydrocarbons and n-alkanes in Suspended Particulate Matter and Sediments from the Langat River, Peninsular Malaysia

    Directory of Open Access Journals (Sweden)

    Alireza Riyahi Bakhtiari

    2009-07-01

    Full Text Available The Langat River basin has seen rapid developments in industrialization, urbanization and dramatic population increases during the past two decades. The composition and sources of polycyclic aromatic hydrocarbons (PAHs and aliphatic hydrocarbon (n-alkanes concentrations were determined in surface sediments (SS and suspended particulate matter (SPM collected from six locations in the Langat River. The total n-alkanes concentrations (∑HC ranged from 5900 to 23000 µg/g in SPM and 1700 to 8600 µg/g in SS samples. Total PAHs concentrations varied from 306 to 7968 ng/g in SPM and 558 to 980 ng/g in SS. PAHs and n-alkanes were dominated by higher molecular weight compounds in SS and low-medium molecular weight compounds in SPM. Carbon preference index (CPI values for n-alkanes in ranges C 25-33, C 15-35 and C 25-35 varied from 0.95 to 2.49 in SS and close to unity in SPM. The CPIs values indicated multiple n-alkanes sources (petrogenic and natural. PAHs isomer pairs ratios indicated multiple (petrogenic and pyrogenic with predominance of pyrogenic PAH sources. Analysis of the possible source of PAHs and n-alkanes indicated a complicated, combined PAHs and n-alkanes source in the Langat River.

  10. Composition of leaf n-alkanes in three Satureja montana L. subspecies from the Balkan peninsula: ecological and taxonomic aspects.

    Science.gov (United States)

    Dodoš, Tanja; Rajčević, Nemanja; Tešević, Vele; Matevski, Vlado; Janaćković, Pedja; Marin, Petar D

    2015-01-01

    The composition of the epicuticular leaf n-alkanes of eight populations of three Satureja montana subspecies (S. montana L. subsp. pisidica (Wettst.) Šilić, S. montana L. subsp. montana, and S. montana L. subsp. variegata (Host) P. W. Ball), from central and western areas of the Balkan Peninsula was characterized by GC-FID and GC/MS analyses. In the leaf waxes, 15 n-alkane homologs with chain-lengths ranging from C21 to C35 were identified. The main n-alkane in almost all samples was n-nonacosane (C29 ), but differences in the contents of three other dominant n-alkanes allowed separating the coastal from the continental populations. The diversity and variability of the epicuticular-leaf-n-alkane patterns and their relation to different geographic and bioclimatic parameters were analyzed by several statistical methods (principal component, discriminant, and cluster analyses as well as the Mantel test). All tests showed a high correlation between the leaf n-alkane pattern and the geographical distribution of the investigated populations, confirming the differentiation between S. montana subsp. pisidica and the other two subspecies. The S. montana subsp. variegata and S. montana subsp. montana populations are geographically closer and their differentiation according to the leaf-n-alkane patterns was not clear, even though there was some indication of discrimination between them. Moreover, most of the bioclimatic parameters related to temperature were highly correlated with the differentiation of the coastal and the continental populations.

  11. Seasonal variations and source profile of n-alkanes in particulate matter (PM10) at a heavy traffic site, Delhi.

    Science.gov (United States)

    Gupta, Sarika; Gadi, Ranu; Mandal, T K; Sharma, S K

    2017-01-01

    Delhi is one of the most polluted cities in the world. The generation of aerosols in the lower atmosphere of the city is mainly due to a large amount of natural dust advection and sizable anthropogenic activities. The compositions of organic compounds in aerosols are highly variable in this region and need to be investigated thoroughly. Twenty-four-hour sampling to assess concentrations of n-alkanes (ng/m(3)) in PM10 was carried out during January 2015 to June 2015 at Indira Gandhi Delhi Technical University for Women (IGDTUW) Campus, Delhi, India. The total average concentration of n-alkanes, 243.7 ± 5.5 ng/m(3), along with the diagnostic tools has been calculated. The values of CPI1, CPI2, and CPI3 for the whole range of n-alkanes series, petrogenic n-alkanes, and biogenic n-alkanes were 1.00, 1.02, and 1.04, respectively, and C max were at C25 and C27. Diagnostic indices and curves indicated that the dominant inputs of n-alkanes are from petrogenic emissions, with lower contribution from biogenic emissions. Significant seasonal variations were observed in average concentrations of n-alkanes, which is comparatively higher in winter (187.4 ± 4.3 ng/m(3)) than during the summer season (56.3 ± 1.1 ng/m(3)).

  12. Preferential methanogenic biodegradation of short-chain n-alkanes by microbial communities from two different oil sands tailings ponds.

    Science.gov (United States)

    Shahimin, Mohd Faidz Mohamad; Foght, Julia M; Siddique, Tariq

    2016-05-15

    Oil sands tailings ponds harbor diverse anaerobic microbial communities capable of methanogenic biodegradation of solvent hydrocarbons entrained in the tailings. Mature fine tailings (MFT) from two operators (Albian and CNRL) that use different extraction solvents were incubated with mixtures of either two (n-pentane and n-hexane) or four (n-pentane, n-hexane, n-octane and n-decane) n-alkanes under methanogenic conditions for ~600 d. Microbes in Albian MFT began methane production by ~80 d, achieving complete depletion of n-pentane and n-hexane in the two-alkane mixture and their preferential biodegradation in the four-alkane mixture. Microbes in CNRL MFT preferentially metabolized n-octane and n-decane in the four-alkane mixture after a ~80 d lag but exhibited a lag of ~360 d before commencing biodegradation of n-pentane and n-hexane in the two-alkane mixture. 16S rRNA gene pyrosequencing revealed Peptococcaceae members as key bacterial n-alkane degraders in all treatments except CNRL MFT amended with the four-alkane mixture, in which Anaerolineaceae, Desulfobacteraceae (Desulfobacterium) and Syntrophaceae (Smithella) dominated during n-octane and n-decane biodegradation. Anaerolineaceae sequences increased only in cultures amended with the four-alkane mixture and only during n-octane and n-decane biodegradation. The dominant methanogens were acetoclastic Methanosaetaceae. These results highlight preferential n-alkane biodegradation by microbes in oil sands tailings from different producers, with implications for tailings management and reclamation.

  13. Hydrogen isotopic compositions and their environmental significance for individual n-alkanes in typical plants from land in China

    Institute of Scientific and Technical Information of China (English)

    DUAN Yi; WU BaoXiang

    2009-01-01

    Hydrogen isotopes of n-alkanes in grasses, tree leaves and reeds from six regions with latitudes of 20° to 39°N in China are measured by GC-TC-IRMS analytical technique in order to understand their hy-drogen isotopic compositions and environmental significance. The results show that a difference in δD values (from -42.1‰ to -66.6‰) of n-alkanes exists among the same kinds of plants from various re-gions. Hydrogen isotopic compositions of most even carbon numbered n-alkanes in every plant are slightly heavier than that of the odd homologues. A trend toward D-enrichment with increasing chain length of n-alkanes in most plant samples is observed. Mean δD values of n-alkanes in the studied plants range from -202.6‰ to -130.7‰ and the reed from a salt marsh has the largest value. The mean δD values of individual n-alkanes among the same kinds of plants from various regions have the characteristics of leaf > reed > grass. The hydrogen isotopic compositions of n-alkanes are apparently distinct among various kinds of plants from the same region and the mean δD values exhibit a distri-bution of tree leaf > reed > grass. It is observed that the mean δD values of n-alkanes and δD values of C27 and C29 n-alkanes in the grasses and tree leaves from these studied regions correlate clearly nega-tively with latitude and positively with temperature, indicating that these values can be used as excel-lent indicators of environment and climate. These results provide important basic data for under-standing the distributional law of hydrogen isotopes of individual n-aikanes and their applied research.

  14. Carbon and Hydrogen Isotopic Composition of Plant Wax n-Alkanes: A Tool for Characterizing Soil Provenance in Forensic Science

    Science.gov (United States)

    Pedentchouk, N.; Wagner, T.; Jones, M.

    2009-04-01

    Forensic science is an integrative discipline that requires material evidence from diverse sources. Geochemical evidence derived from inorganic and organic substances is becoming increasingly popular among law enforcement agencies in industrialized countries. Previous investigations indicate that the relative distributions of individual plant-derived biomarkers found in soils are linked to the biomarker patterns found in the overlying vegetation. However, identification of soil provenance based on the distribution of plant-derived biomarkers for forensic purposes is inhibited by the fact that a significant number of terrestrial plant species have overlapping biomarker distributions. In order to enhance the resolving power of plant-derived biomarker signal, we propose to enhance the molecular approach by adding a stable isotope component, i.e. the delta13C/deltaD values of individual biomarkers. The first objective of this project is to determine the delta13C/deltaD signatures of n-alkanes derived from various higher plant types commonly growing in the UK. The second objective is to investigate whether the same species/plant types differ isotopically between two locations affected by different weather patterns in the UK: a relatively warmer and drier Norwich, Norfolk and a cooler and wetter Newcastle-upon-Tyne in NE England. The n-C29 alkane data from 14 tree species sampled during July 2007 and August 2008 in Newcastle show a clear negative trend between delta13C and deltaD values. When these data are plotted against each other, the six deciduous angiosperms (delta13C: c. -39 to -35 per mil; deltaD: c. -155 to -130 per mil) are completely separated from four evergreen angiosperms (delta13C: c. -33 to -28 per mil; deltaD: c. -195 to -165 per mil). The four gymnosperm species data plot between those of the deciduous and evergreen angiosperms. Because all 14 species in Newcastle experience the same environmental conditions, we suggest that the observed isotopic

  15. Influence of pore size distributions on decomposition of maize leaf residue: evidence from X-ray computed micro-tomography

    Science.gov (United States)

    Negassa, Wakene; Guber, Andrey; Kravchenko, Alexandra; Rivers, Mark

    2014-05-01

    Soil's potential to sequester carbon (C) depends not only on quality and quantity of organic inputs to soil but also on the residence time of the applied organic inputs within the soil. Soil pore structure is one of the main factors that influence residence time of soil organic matter by controlling gas exchange, soil moisture and microbial activities, thereby soil C sequestration capacity. Previous attempts to investigate the fate of organic inputs added to soil did not allow examining their decomposition in situ; the drawback that can now be remediated by application of X-ray computed micro-tomography (µ-CT). The non-destructive and non-invasive nature of µ-CT gives an opportunity to investigate the effect of soil pore size distributions on decomposition of plant residues at a new quantitative level. The objective of this study is to examine the influence of pore size distributions on the decomposition of plant residue added to soil. Samples with contrasting pore size distributions were created using aggregate fractions of five different sizes (soil samples. Dried pieces of maize leaves 2.5 mg in size (equivalent to 1.71 mg C g-1 soil) were added to half of the studied samples. Samples with and without maize leaves were incubated for 120 days. CO2 emission from the samples was measured at regular time intervals. In order to ensure that the observed differences are due to differences in pore structure and not due to differences in inherent properties of the studied aggregate fractions, we repeated the whole experiment using soil from the same aggregate size fractions but ground to soil size fractions of intact aggregates, and 40-50% in ground samples, respectively. The results of the incubation experiment demonstrated that, while greater C mineralization was observed in samples of all size fractions amended with leaf, the effect of leaf presence was most pronounced in the smaller aggregate fractions (0.05-0.1 mm and 0.05 mm) of intact aggregates. The results of

  16. Structural and Kinetic Studies of Novel Cytochrome P450 Small-Alkane Hydroxylases

    Energy Technology Data Exchange (ETDEWEB)

    Arnold, Frances H.

    2012-02-27

    The goals of this project are to investigate (1) the kinetics and stabilities of engineered cytochrome P450 (P450) small alkane hydroxylases and their evolutionary intermediates, (2) the structural basis for catalytic proficiency on small alkanes of these engineered P450s, and (3) the changes in redox control resulting from protein engineering. To reach these goals, we have established new methods for determining the kinetics and stabilities of multicomponent P450s such as CYP153A6. Using these, we were able to determine that CYP153A6 is proficient for hydroxylation of alkanes as small as ethane, an activity that has never been observed previously in any natural P450. To elucidate the structures of the engineered P450s, we obtained x-ray diffraction data for two variants in the P450PMO (propane monooxygenase) lineage and a preliminary structure for the most evolved variant. This structure shows changes in the substrate binding regions of the enzyme and a reduction in active site volume that are consistent with the observed changes in substrate specificity from fatty acids in the native enzyme to small alkanes in P450PMO. We also constructed semi-rational designed libraries mutating only residues in the enzyme active site that in one round of mutagenesis and screening produced variants that achieved nearly half of the activity of the most evolved enzymes of the P450PMO lineage. Finally, we found that changes in redox properties of the laboratory-evolved P450 alkane hydroxylases did not reflect the improvement in their electron transfer efficiency. The heme redox potential remained constant throughout evolution, while activity increased and coupling efficiency improved from 10% to 90%. The lack of correlation between heme redox potential and enzyme activity and coupling efficiency led us to search for other enzyme properties that could be better predictors for activity towards small alkanes, specifically methane. We investigated the oxidation potential of the radical

  17. The Application Research of Cloud Computing Technology in the Electronic Data Investigation and Evidence Collection%云计算技术在电子数据调查与取证中的应用研究

    Institute of Scientific and Technical Information of China (English)

    黄云峰

    2014-01-01

    With the development of cloud computing technology, it has been widely used in many fields. The low storage amount, unseasonal analysis and some other defects that exist in traditional computer forensics can be solved through the cloud computing. The characteristics of efficient computing, virtualization operation of cloud computing technology can expand the storage of evidence, improve the equipment utilization, and shorten the time of evidence and so on. This paper introduces the characteristics of cloud computing and the connotation of electronic data evidence, analyzes the significance of cloud computing to electronic data evidence, and further carries on the analysis and research on the application of cloud computing in electronic data evidence.%随着云计算技术的发展,其已经在许多领域得到广泛的应用。通过云计算技术可以解决传统计算机取证所存在的存储量不足、分析不及时等一些缺陷,因为云计算技术具有高效计算、虚拟化运行等特点,基于这些特点可以扩大证据的储存、提高设备的利用率以及缩短取证时间等等。文章介绍了云计算的特点及电子数据取证的内涵,分析了云计算对电子数据取证的意义,并进一步对云计算在电子数据取证中的应用进行了分析与研究。

  18. Revisiting Mt. Kilimanjaro: Do n-alkane biomarkers in soils reflect the δ2H isotopic composition of precipitation?

    Directory of Open Access Journals (Sweden)

    M. Zech

    2014-06-01

    Full Text Available During the last decade compound-specific deuterium (δ2H analysis of plant leaf wax-derived n-alkanes has become a promising and popular tool in paleoclimate research. This is based on the widely accepted assumption that n-alkanes in soils and sediments generally reflect δ2H of precipitation (δ2Hprec. Recently, several authors suggested that δ2H of n-alkanes (δ2H,sub>n-alkanes can also be used as proxy in paleoaltimetry studies. Here we present results from a δ2H transect study (~1500 to 4000 m a.s.l. carried out on precipitation and soil samples taken from the humid southern slopes of Mt. Kilimanjaro. Contrary to earlier suggestions, a distinct altitude effect in δ2Hprec is present above ~2000 m a.s.l., i.e. δ2Hprec values become more negative with increasing altitude. The compound-specific δ2H values of nC27 and nC29 do not confirm this altitudinal trend, but rather become more positive both in the O-layers (organic layers and the Ah-horizons (mineral topsoils. Although our δ2Hn-alkane results are in agreement with previously published results from the southern slopes of Mt. Kilimanjaro (Peterse et al., 2009, BG, 6, 2799–2807, a major re-interpretation is required given that the δ2Hn-alkane results do not reflect the δ2Hprec results. The theoretical framework for this re-interpretation is based on the evaporative isotopic enrichment of leaf water associated with transpiration process. Modelling results show that relative humidity, decreasing considerably along the southern slopes of Mt. Kilimanjaro (from 78% at ~ 2000 m a.s.l. to 51% at 4000 m a.s.l., strongly controls δ2Hleaf water. The modelled δ2H leaf water enrichment along the altitudinal transect matches well the measured 2H leaf water enrichment as assessed by using the δ2Hprec and δ2Hn-alkane results and biosynthetic fractionation during n-alkane biosynthesis in leaves. Given that our results clearly demonstrate that n-alkanes in soils do not simply reflect δ2Hprec

  19. The effect of environmental factors on stable isotopic composition of n-alkanes in Mediterranean olive oils

    Science.gov (United States)

    Pedentchouk, Nikolai; Mihailova, Alina; Abbado, Dimitri

    2014-05-01

    Traceability of the geographic origin of olive oils is an important issue from both commercial and health perspectives. This study evaluates the impact of environmental factors on stable C and H isotope compositions of n-alkanes in extra virgin olive oils from Croatia, France, Greece, Italy, Morocco, Portugal, Slovenia, and Spain. The data are used to investigate the applicability of stable isotope methodology for olive oil regional classification in the Mediterranean region. Analysis of stable C isotope composition of n-C29 alkane showed that extra virgin olive oils from Portugal and Spain have the most positive n-C29 alkane delta13C values. Conversely, olive oils from Slovenia, northern and central Italy are characterized by the most negative values. Overall, the n-C29 alkane delta13C values show a positive correlation with the mean air temperature during August-December and a negative correlation with the mean relative humidity during these months. Analysis of stable H isotope composition of n-C29 alkane revealed that the deltaD values are the most positive in olive oils from Greece and Morocco and the most negative in oils from northern Italy. The deltaD values of oils show significant correlation with all the analyses geographical parameters: the mean air temperature and relative humidity during August-December, the total amount of rainfall (the same months) and the annual deltaD values of precipitation. As predictor variables in the Categorical Data Analysis, the n-C29 alkane deltaD values show the most significant discriminative power, followed by the n-C29 alkane delta13C values. Overall, 93.4% of olive oil samples have been classified correctly into one of the production regions. Our findings suggest that an integrated analysis of C and H isotope compositions of n-alkanes extracted from extra virgin olive oil could become a useful tool for geographical provenancing of this highly popular food commodity.

  20. A Facile Aqueous Synthesis of Bis(indol-3-yl)alkanes Cata-lyzed by Dodecylbenzenesulfonic Acid

    Institute of Scientific and Technical Information of China (English)

    PENG,Yi-Yuan; ZHANG,Qiu-Lan; YUAN,Jian-Jun; CHENG,Jin-Pei

    2008-01-01

    An environmentally friendly synthetic method for bis(indol-3-yl)alkane derivatives has been developed. In the presence of 10 mol% of dodecylbenzenesulfonic acid (DBSA), electrophilic substitution reaction of indoles with aldehydes or ketones proceeded smoothly in water, giving rise to the corresponding bis(indol-3-yl)alkanes in good to excellent yields. The use of inexpensive and easily available catalyst, mild reaction conditions and simple work-up procedure made this protocol practical and economically attractive.

  1. Novel Mesoporous Silica Materials with Hierarchically Ordered Nanochannel: Synthesis with the Assistance of Straight-Chain Alkanes and Application

    Directory of Open Access Journals (Sweden)

    Haidong Zhang

    2016-01-01

    Full Text Available The straight-chain alkane-assisted synthesis of hierarchical mesoporous silica materials (MSM results in variable mesostructures and morphologies due to remarkably different self-assembly routes of template agent from those without the assistance of straight-chain alkanes. The textural properties, particularly pore size, channel structure, morphology, and hierarchical structure of those MSM make them demonstrate peculiar effects in the immobilization of homogeneous catalysts.

  2. Draft Genome Sequence of Nocardioides luteus Strain BAFB, an Alkane-Degrading Bacterium Isolated from JP-7-Polluted Soil

    Science.gov (United States)

    Brown, Lisa M.; Gunasekera, Thusitha S.

    2017-01-01

    ABSTRACT Nocardioides luteus strain BAFB is a Gram-positive bacterium that efficiently degrades C8 to C11 alkanes aerobically. The draft genome of N. luteus BAFB is 5.76 Mb in size, with 5,358 coding sequences and 69.9% G+C content. The genes responsible for alkane degradation are present in this strain. PMID:28126947

  3. Alkane distribution and carbon isotope composition in fossil leaves: An interpretation of plant physiology in the geologic past

    Science.gov (United States)

    Graham, H. V.; Freeman, K. H.

    2014-12-01

    The relative chain-length distribution and carbon-isotope composition of n-alkanes extracted from sedimentary rocks are important geochemical tools for investigating past terrestrial ecosystems. Alkanes preserved in ancient sediments are assumed to be contemporaneous, derived from the same ecosystem, and integrated from the biomass present on the landscape at the time of deposition. Further, there is an underlying assumption that ancient plants exhibited the same metabolic and physiological responses to climate conditions that are observed for modern plants. Interpretations of alkane abundances and isotopic signatures are complicated by the strong influence of phylogenetic affiliation and ecological factors, such as canopy structure. A better understanding of how ecosystem and taxa influence alkane properties, including homologue abundance patterns and leaf-lipid carbon isotope fractionation would help strengthen paleoecological interpretations based on these widely employed plant biomarkers. In this study, we analyze the alkane chain-length distribution and carbon-isotope composition of phytoleim and alkanes (d13Cleaf and d13Clipid) extracted from a selection of Cretaceous and Paleocene fossil leaves from the Guaduas and Cerrejon Formations of Colombia. These data were compared with data for the same families in a modern analogue biome. Photosynthetic and biosynthetic fractionation (∆leaf and elipid) values determined from the fossil material indicate carbon metabolism patterns were similar to modern plants. Fossil data were incorporated in a biomass-weighted mixing model to represent the expected lipid complement of sediment arising from this ecosystem and compared with alkane measurements from the rock matrix. Modeled and observed isotopic and abundance patterns match well for alkane homologs most abundant in plants (i.e., n-C27 to n-C33). The model illustrates the importance of understanding biases in litter flux and taphonomic pressures inherent in the

  4. Fossil Leaves and Fossil Leaf n-Alkanes: Reconstructing the First Closed Canopied Rainforests

    Science.gov (United States)

    Graham, H. V.; Freeman, K. H.

    2013-12-01

    Although the age and location is disputed, the rise of the first closed-canopy forest is likely linked with the expansion of angiosperms in the late Cretacous or early Cenozoic. The carbon isotope 'canopy effect' reflects the extent of canopy closure, and is well documented in δ13C values of the leaves and leaf lipids in modern forests. To test the extent of canopy closure among the oldest documented angiosperm tropical forests, we analyzed isotopic characteristics of leaf fossils and leaf waxes from the Guaduas and Cerrejón Formations. The Guaduas Fm. (Maastrichtian) contains some of the earliest angiosperm fossils in the Neotropics, and both leaf morphology and pollen records at this site suggest an open-canopy structure. The Cerrejón Fm. (Paleocene) contains what are believed to be the first recorded fossil leaves from a closed-canopy forest. We analyzed the bulk carbon isotope content (δ13Cleaf) of 199 fossil leaves, as well as the n-alkane concentration and chain-length distribution, and δ13C of alkanes (δ13Clipid) of 73 fossil leaves and adjacent sediment samples. Fossil leaves are dominated by eudicots and include ten modern plant families (Apocynaceae, Bombaceae, Euphorbaceae, Fabaceae, Lauraceae, Malvaceae, Meliaceae, Menispermaceae, Moraceae, Sapotaceae). We interpreted extent of canopy coverage based on the range of δ13Cleaf values. The narrow range of δ13C values in leaves from the Guaduas Fm (2.7‰) is consistent with an open canopy. A significantly wider range in values (6.3‰) suggests a closed-canopy signature for site 0315 of the Cerrejón Fm,. In contrast, at Site 0318, a lacustrine deposit, leaves had a narrow range (3.3‰) in δ13C values, and this is not consistent with a closed-canopy, but is consistent with leaf assemblages from a forest edge. Leaves that accumulate in lake sediments tend to be biased toward plants living at the lake edge, which do not experience closed-canopy conditions, and do not express the isotopic

  5. Competition between n-alkane-assimilating yeasts and bacteria during colonization of sandy soil microcosms.

    Science.gov (United States)

    Schmitz, C; Goebel, I; Wagner, S; Vomberg, A; Klinner, U

    2000-07-01

    An n-alkane-assimilating strain of Candida tropicalis was selected in sandy soil inoculated with microorganisms from contaminated sites. Competition experiments with n-alkane utilizers from different strain collections confirmed that yeasts overgrow bacteria in sandy soil. Acidification of the soil is one of the colonization factors useful for the yeasts. It can be counteracted by addition of bentonite, a clay mineral with high ion exchange capacity, but not, however, by kaolin. Strains of different yeast species showed different levels of competitiveness. Strains of Arxula adeninivorans, Candida maltosa, and Yarrowia lipolytica overgrew strains of C. tropicalis, C. shehatae or Pichia stipitis. Two strains of C. maltosa and Y. lipolytica coexisted during several serial transfers under microcosm conditions.

  6. Prediction of vapour-liquid equilibrium for n-alkane fluids

    Directory of Open Access Journals (Sweden)

    Binay Prakash Akhouri

    2016-03-01

    Full Text Available Analysis of the equations of state of the hard convex body chain and hard spheres has been done for predicting the vapor liquid equilibrium of simple fluids of n-alkanes.The repulsive part of the Boublik equation of state for the hard convex body chainhas been foundas an equivalent alternativeeither for the well known Carnahan-Starling repulsive termor the established van der Waals repulsive part of hard spheres equations of state.The attractive parts of these equations of state have the similar form as that of the van der Waals and are obeying thepower-law temperature dependency. Add-on separation method of compressibility factor has been used for these equations of state. The simulated data for VLE densities from these equations of state are found to agree well with the available experimental data for n-alkane fluids.

  7. A Novel Topological Index for the Studies on Structure-Properties of Alkanes

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A novel topological index derived from eccentric connectivity index has been proposed. The new topological index and eccentric connectivity index were correlated with eight physical properties such as the boiling point, critical temperature, critical pressure, critical volume, evaporation heat, density, heat capaci- ty, surface tension, and three thermodynamic properties such as standard enthalpy, standard entropy and standard formation free energy of alkanes. A series of empiric equations for calculating the properties were obtained. Correlation coefficients of nine properties were more than 0. 99 . Regression analysis and calcula- tion results indicated that the topological indices were well correlated with the physico-chemical properties of alkanes, and the novel topological index was far superior to eccentric connectivity index in the correlation.

  8. Alkane Biomarkers in Permian-Triassic Boundary Strata at Meishan Section, Changxing,Zhejiang Province

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Meishan Section D in Changxing County, Zhejiang Province, China has been selected as the global stratotype of the Permian-Triassic boundary and various studies have been done at the boundary, but the gas chromatographic-mass spectrographic analysis of alkane biomarkers has not been investigated. This paper presents the results of a study of the biomarkers analyzed in a series of samples across the Permian-Triassic boundary at both Meishan Section A and Section D. The results show that the overall concentration of alkane biomarkers in the Permian-Triassic boundary strata is high in Bed 26 while it is low in Bed 27. A variety of biomarker parameters demonstrate that the main sources of organic matter in the sediment are algae and bacteria and that the depositional environment varied from weakly oxidizing to reducing during the studied interval.

  9. Interaction of hydrocarbon monolayer surfaces across n-alkanes: A steric repulsion

    Science.gov (United States)

    Herder, Christina E.; Ninham, Barry W.; Christenson, Hugo K.

    1989-05-01

    We present results of force measurements between hydrocarbon monolayer surfaces across n-alkanes (hexane, decane, and tetradecane). The interaction is qualitatively different from that of any previously studied system and, in particular, bears no resemblance to an oscillatory solvation force. Instead, the force is repulsive from about 2.5 nm, with the exception of a shallow minimum just outside a force maximum at 0.8-0.9 nm. At smaller separations the force becomes attractive and there is a weak adhesion at contact. We suggest that the force law is due to a steric effect—a repulsive interaction originating in restrictions on chain conformations of the alkanes at small surface separations. This interaction is accessible via simple mean-field theories. The similarity of the liquid-liquid and liquid-surface interactions allows this to dominate over solvation effects. The results are of significance for interaggregate interactions in lamellar liquid crystals, microemulsions, and surfactant-stabilized dispersions.

  10. Catalytic oxidation of light alkanes (C1-C4) by heteropoly compounds

    KAUST Repository

    Sun, Miao

    2014-01-22

    Heteropoly compounds (HPC) have revealed their potential to generate catalyst for selectively converting light alkanes to oxygenated products. There are various structures in which they are active the primary structure being that of the heteropolyanion itself, the secondary structure is the three-dimensional arrangements of polyanions, and the tertiary structure representing the manner in which the secondary structure assembles into solid particles. There are also a huge variety of elements inside the HPA. The heteropoly acids can have acidity, which varies dramatically depending on composition. This complexity of situation makes it very difficult to really have a predictive vision of their ability to activate and functionalize alkanes. However, a large amount of data reported suggests that the initial formula of the precatalyst is pivotal to direct the selectivity of the reaction toward different oxygenates. Inclusion of alternative transition metal atoms as addenda is highly influential with iron, vanadium, and antimony being particularly outstanding.

  11. Comparison of bulk and n-alkane PETM carbon isotope trends from the Bighorn Basin, Wyoming

    Science.gov (United States)

    Baczynski, A. A.; McInerney, F. A.; Kraus, M. J.; Wing, S.

    2010-12-01

    The Paleocene-Eocene Thermal Maximum (PETM), a period of abrupt, short-term, and large-scale global warming fueled by a large release of isotopically light carbon, is recorded in terrestrial and marine carbonates and organic carbon as a prominent negative carbon isotope excursion (CIE). Here we present a composite stable carbon isotope record from n-alkanes and four bulk organic carbon records from individual sections spanning the PETM interval in the Cabin Fork area of the southeastern Bighorn Basin, Wyoming. The n-alkane curve shows an abrupt, negative shift in δ13C values, an extended CIE body, and a rapid recovery to pre-PETM δ13C values. While the bulk organic carbon records show similarly abrupt negative shifts in δ13C values, the CIE appears to be compressed as well as smaller in magnitude, and the return to more positive δ13C values is often more gradual. Furthermore, the stratigraphic thickness of the most negative CIE values and the pattern of the recovery phase are not consistent among the four bulk organic carbon records. The discrepancy between the bulk organic matter and n-alkane CIE may arise because of changes in soil organic matter cycling during the PETM. Bulk soil organic matter δ13C values are influenced by degradation and selective preservation whereas n-alkanes are resistant to diagenesis. Variations in sediment accumulation rates across the basin may be responsible for the differences between the four bulk organic carbon δ13C records. Sites with extended CIE bodies likely present more complete isotope records with greater time resolution and less time averaging than those with reduced CIEs. The shape of the high-resolution n-alkane curve presented here is similar to the newest 3He-based timescale for the PETM using data from Walvis Ridge, IODP site 1266 (Murphy et al., 2010). The most significant difference between this revised PETM timescale and previously published age models is the allocation of time within the PETM event. Murphy et

  12. Biodegradation of crude oil and n-alkanes by fungi isolated from Oman

    Energy Technology Data Exchange (ETDEWEB)

    Elshafie, Abdulkadir [Department of Biology, College of Science, Sultan Qaboos University, P.O. Box 36 Al Khod, Muscat (Oman)], E-mail: Elshafie@squ.edu.om; AlKindi, Abdulaziz Yahya [Department of Biology, College of Science, Sultan Qaboos University, P.O. Box 36 Al Khod, Muscat (Oman); Al-Busaidi, Sultan [Oman Refinery Company Laboratories, LLC, P.O. Box 3568 Ruwi PC112 (Oman); Bakheit, Charles [Department of Mathematics and Statistics, College of Science, Sultan Qaboos University, P.O. Box 36 Al Khod, Muscat (Oman); Albahry, S.N. [Department of Biology, College of Science, Sultan Qaboos University, P.O. Box 36 Al Khod, Muscat (Oman)

    2007-11-15

    Ten fungal species isolated from tar balls collected from the beaches of Oman were tested for their abilities to grow and degrade n-alkanes and crude oil. The abilities of Aspergillus niger, A. ochraceus and Penicillium chrysogenum to degrade n-alkanes (C13-C18), crude oil were compared and their mycelial biomass was measured. Significant differences were found in the utilization of C15, C16, C17 and C18 by the three fungi. Similarly, significant differences we found in the amount of biomass produced by the three fungi growing on C13, C17, C18 and crude oil. The correlation coefficient of biomass and oil utilization was not statistically significant for Aspergillus niger, significant for Aspergillus terreus and highly significant for P. chrysogenum.

  13. Anaerobic biodegradation of longer-chain n-alkanes coupled to methane production in oil sands tailings.

    Science.gov (United States)

    Siddique, Tariq; Penner, Tara; Semple, Kathleen; Foght, Julia M

    2011-07-01

    Extraction of bitumen from mined oil sands ores produces enormous volumes of tailings that are stored in settling basins (current inventory ≥ 840 million m(3)). Our previous studies revealed that certain hydrocarbons (short-chain n-alkanes [C(6)-C(10)] and monoaromatics [toluene, o-xylene, m-xylene]) in residual naphtha entrained in the tailings are biodegraded to CH(4) by a consortium of microorganisms. Here we show that higher molecular weight n-alkanes (C(14), C(16), and C(18)) are also degraded under methanogenic conditions in oil sands tailings, albeit after a lengthy lag (~180 d) before the onset of methanogenesis. Gas chromatographic analyses showed that the longer-chain n-alkanes each added at ~400 mg L(-1) were completely degraded by the resident microorganisms within ~440 d at ~20 °C. 16S rRNA gene sequence analysis of clone libraries implied that the predominant pathway of longer-chain n-alkane metabolism in tailings is through syntrophic oxidation of n-alkanes coupled with CO(2) reduction to CH(4). These studies demonstrating methanogenic biodegradation of longer-chain n-alkanes by microbes native to oil sands tailings may be important for effective management of tailings and greenhouse gas emissions from tailings ponds.

  14. Leaf n-alkanes as characters differentiating coastal and continental Juniperus deltoides populations from the Balkan Peninsula.

    Science.gov (United States)

    Rajčević, Nemanja; Janaćković, Pedja; Dodoš, Tanja; Tešević, Vele; Bojović, Srdjan; Marin, Petar D

    2014-07-01

    The composition of the cuticular n-alkanes isolated from the leaves of nine populations of Juniperus deltoides R.P.Adams from continental and coastal areas of the Balkan Peninsula was characterized by GC-FID and GC/MS analyses. In the leaf waxes, 14 n-alkane homologues with chain-lengths ranging from C22 to C35 were identified. n-Tritriacontane (C33 ) was dominant in the waxes of all populations, but variations between the populations in the contents of all n-alkanes were observed. Several statistical methods (ANOVA, principal component, discriminant, and cluster analyses) were used to investigate the diversity and variability of the cuticular-leaf-n-alkane patterns of the nine J. deltoides populations. This is the first report on the n-alkane composition for this species. The multivariate statistical analyses evidenced a high correlation of the leaf-n-alkane pattern with the geographical distribution of the investigated samples, differentiating the coastal from the continental populations of this taxon.

  15. Transcriptional response of Desulfatibacillum alkenivorans AK-01 to growth on alkanes: insights from RT-qPCR and microarray analyses.

    Science.gov (United States)

    Herath, Anjumala; Wawrik, Boris; Qin, Yujia; Zhou, Jizhong; Callaghan, Amy V

    2016-05-01

    Microbial transformation of n-alkanes in anaerobic ecosystems plays a pivotal role in biogeochemical carbon cycling and bioremediation, but the requisite genetic machinery is not well elucidated.Desulfatibacillum alkenivorans AK-01 utilizes n-alkanes (C13 to C18) and contains two genomic loci encoding alkylsuccinate synthase (ASS) gene clusters. ASS catalyzes alkane addition to fumarate to form methylalkylsuccinic acids. We hypothesized that the genes in the two clusters would be differentially expressed depending on the alkane substrate utilized for growth. RT-qPCR was used to investigate ass-gene expression across AK-01's known substrate range, and microarray-based transcriptomic analysis served to investigate whole-cell responses to growth on n-hexadecane versus hexadecanoate. RT-qPCR revealed induction of ass gene cluster 1 during growth on all tested alkane substrates, and the transcriptional start sites in cluster 1 were determined via 5'RACE. Induction of ass gene cluster 2 was not observed under the tested conditions. Transcriptomic analysis indicated that the upregulation of genes potentially involved in methylalkylsuccinate metabolism, including methylmalonyl-CoA mutase and a putative carboxyl transferase. These findings provide new directions for studying the transcriptional regulation of genes involved in alkane addition to fumarate, fumarate recycling and the processing of methylalkylsuccinates with regard to isolates, enrichment cultures and ecological datasets.

  16. Water solubility of selected C9-C18 alkanes using a slow-stir technique: Comparison to structure - property models.

    Science.gov (United States)

    Letinski, Daniel J; Parkerton, Thomas F; Redman, Aaron D; Connelly, Martin J; Peterson, Brian

    2016-05-01

    Aqueous solubility is a fundamental physical-chemical substance property that strongly influences the distribution, fate and effects of chemicals upon release into the environment. Experimental water solubility was determined for 18 selected C9-C18 normal, branched and cyclic alkanes. A slow-stir technique was applied to obviate emulsion formation, which historically has resulted in significant overestimation of the aqueous solubility of such hydrophobic liquid compounds. Sensitive GC-MS based methods coupled with contemporary sample extraction techniques were employed to enable reproducible analysis of low parts-per billion aqueous concentrations. Water solubility measurements for most of the compounds investigated, are reported for the first time expanding available data for branched and cyclic alkanes. Measured water solubilities spanned four orders of magnitude ranging from 0.3 μg/L to 250 μg/L. Good agreement was observed for selected alkanes tested in this work and reported in earlier literature demonstrating the robustness of the slow-stir water solubility technique. Comparisons of measured alkane water solubilities were also made with those predicted by commonly used quantitative structure-property relationship models (e.g. SPARC, EPIWIN, ACD/Labs). Correlations are also presented between alkane measured water solubilities and molecular size parameters (e.g. molar volume, solvent accessible molar volume) affirming a mechanistic description of empirical aqueous solubility results and prediction previously reported for a more limited set of alkanes.

  17. Long chain n-alkanes and their carbon isotopes in lichen species from western Hubei Province: implication for geological records

    Institute of Scientific and Technical Information of China (English)

    Xianyu HUANG; Jiantao XUE; Shouyu GUO

    2012-01-01

    Five coticolous lichen samples were collected from western Hubei Province of China to analyze the long chain n-alkanes and their carbon isotope compositions.The n-alkanes range in carbon number from C17 to C33 with strong odd-over-even predominance between C21and C33.Lichens are dominated by n-C29 in the samples of Dajiuhu,Shennongjia Mountain,but by both n-C23 and n-C29 at Qizimei Mountain.This difference may result from the different environmental conditions in these two sites.The δ13C values of long chain n-alkanes in lichen samples show the signature of C3 plants.Based on compoundspecific carbon isotopic values and previous results,we state that alkane homologs > C23 mainly originate from the symbiotic fungi,while symbiotic algae only contribute trace amount of long chain alkanes.Of great interesting is the occurrence of long chain 3-methylalkanes in the Qizimei samples.These anteiso compounds range from C24 to C32,displaying obvious even-over-odd predominance.This study reveals that the association of long chain 3-methylalkanes with n-C23 alkane might be used as proxies to reconstruct the paleoecological implications of lichens in Earth history.

  18. Long chain n-alkanes and their carbon isotopes in lichen species from western Hubei Province: implication for geological records

    Science.gov (United States)

    Huang, Xianyu; Xue, Jiantao; Guo, Shouyu

    2012-03-01

    Five coticolous lichen samples were collected from western Hubei Province of China to analyze the long chain n-alkanes and their carbon isotope compositions. The n-alkanes range in carbon number from C17 to C33 with strong odd-over-even predominance between C21 and C33. Lichens are dominated by n-C29 in the samples of Dajiuhu, Shennongjia Mountain, but by both n-C23 and n-C29 at Qizimei Mountain. This difference may result from the different environmental conditions in these two sites. The δ 13C values of long chain n-alkanes in lichen samples show the signature of C3 plants. Based on compoundspecific carbon isotopic values and previous results, we state that alkane homologs >C23 mainly originate from the symbiotic fungi, while symbiotic algae only contribute trace amount of long chain alkanes. Of great interesting is the occurrence of long chain 3-methylalkanes in the Qizimei samples. These anteiso compounds range from C24 to C32, displaying obvious even-over-odd predominance. This study reveals that the association of long chain 3-methylalkanes with n-C23 alkane might be used as proxies to reconstruct the paleoecological implications of lichens in Earth history.

  19. Distribution and sources of n-alkanes and polycyclic aromatic hydrocarbons in shellfish of the Egyptian Red Sea coast

    Directory of Open Access Journals (Sweden)

    Ahmed El Nemr

    2016-06-01

    Full Text Available Aromatic hydrocarbons and n-alkanes were analyzed in shellfish collected from 13 different sites along the Egyptian Red Sea coast. All samples were analyzed for n-alkanes (C8–C40 and polycyclic aromatic hydrocarbons (EPA list of PAHs. n-Alkanes in shellfish samples from 13 locations were found to be in the range of 71.0–701.1 ng/g with a mean value of 242.2 ± 192.1 ng/g dry wt. Different indices were calculated for the n-alkanes to assess their sources. These were carbon preference index (CPI, average chain length (ACL, terrigenous/aquatic ratio (TAR, natural n-alkane ratio (NAR and proxy ratio (Paq. Most of the collected samples of n-alkanes were discovered to be from natural sources. Aromatic hydrocarbons (16 PAHs from 13 sites varied between 1.3 and 160.9 ng/g with an average of 47.9 ± 45.5 ng/g dry wt. Benzo(apyrine (BaP, a cancer risk assessment, was calculated for the PAHs and resulted in ranges between 0.08 and 4.47 with an average of 1.25 ng/g dry wt.

  20. Biocatalysts for cascade reaction: porcine pancreas lipase (PPL)-catalyzed synthesis of bis(indolyl)alkanes.

    Science.gov (United States)

    Xiang, Ziwei; Liu, Zhiqiang; Chen, Xiang; Wu, Qi; Lin, XianFu

    2013-10-01

    A cascade reaction between aldehydes and indole catalyzed by lipase from porcine pancreas Type II (PPL) in solvent mixture at 50 °C was reported for the first time. Some control experiments had been designed to demonstrate that the PPL was responsible for the cascade reaction. After the optimization of the stepwise process, a series of bis(indolyl)alkanes were prepared in moderate to excellent yields under the catalysis of PPL.

  1. A novel growth mode of alkane films on a SiO2 surface

    DEFF Research Database (Denmark)

    Mo, H.; Taub, H.; Volkmann, U.G.;

    2003-01-01

    Synchrotron X-ray specular scattering measurements confirm microscopically a structural model recently inferred by very-high-resolution ellipsometry of a solid dotriacontane (n-C32H66 or C32) film formed by adsorption from solution onto a SiO2 surface. Sequentially, one or two layers adsorb on th...... previously for shorter alkanes deposited from the vapor phase onto solid surfaces....

  2. Inhibitory Potency of 4-Carbon Alkanes and Alkenes toward CYP2E1 Activity

    OpenAIRE

    2014-01-01

    CYP2E1 has been implicated in the bioactivation of many small molecules into reactive metabolites which form adducts with proteins and DNA, and thus a better understanding of the molecular determinants of its selectivity are critical for accurate toxicological predictions. In this study, we determined the potency of inhibition of human CYP2E1 for various 4-carbon alkanes, alkenes and alcohols. In addition, known CYP2E1 substrates and inhibitors including 4-methylpyrazole, aniline, and dimethy...

  3. A comparative study of n-alkane biomarker and pollen records: an example from southern China

    Institute of Scientific and Technical Information of China (English)

    ZHENG YanHong; ZHOU WeiJian; XIE ShuCheng; YU XueFeng

    2009-01-01

    We report the results of a comparative study of n-alkane biomarkers and pollens in lacustrine and peat deposits at Dingnan, Jiangxi Province in southern China, and discuss the likely causes for the discrepancy in the interpretations of the n-alkane biomarker and pollen records in terms of climate and vegetation change. The results show that past changes in climate and vegetation revealed by the n-alkane record are not always consistent with the pollen assemblage record in the whole section.Biomarkers do not permit direct identification of the plant family and/or genus and mainly record compositions of local plant remains, while pollens mainly reflect the regional vegetation change. Biomarkers and pollen records complement each other, providing a better picture of local and regional environments. Furthermore, biomarkers are more sensitive than pollen to climatic and vegetational change. Several climatic events are clearly identified by the n-alkane biomarker proxies, such as C31/(C27+C29+C31) ratio and can be correlated to the North Atlantic Heinrich event, B/A, YD and two dry-cool events during the early Holocene such as the periods of 9850 to 9585 cal a B.P. and 8590 to 7920 cal a B.P. These events are consistent with those found in the surrounding regions, suggesting that the regional climate was coupled with global-scale abrupt climatic events. Our results suggest that biomarker and pollen data can record the more detailed climate and vegetation information, thus improving the resolution and precision of vegetation and climate reconstruction.

  4. Modelling and parameter estimation in reactive continuous mixtures: the catalytic cracking of alkanes - part II

    Directory of Open Access Journals (Sweden)

    F. C. PEIXOTO

    1999-09-01

    Full Text Available Fragmentation kinetics is employed to model a continuous reactive mixture of alkanes under catalytic cracking conditions. Standard moment analysis techniques are employed, and a dynamic system for the time evolution of moments of the mixture's dimensionless concentration distribution function (DCDF is found. The time behavior of the DCDF is recovered with successive estimations of scaled gamma distributions using the moments time data.

  5. Angiosperm n-alkane distribution patterns and the geologic record of C4 grassland evolution

    Science.gov (United States)

    Henderson, A.; Graham, H. V.; Patzkowsky, M.; Fox, D. L.; Freeman, K. H.

    2012-12-01

    n-Alkane average chain-length (ACL) patterns vary regionally with community composition and climate. To clarify the influence of phylogenetic and community patterns, we compiled and analyzed a global database of published n-alkane abundance for n-C27 to C35 homologs in modern plant specimens (n=205). ACL for waxes in C4 non-woody plants are longer than for woody plants, suggesting ACL can serve as an indicator of the three-dimensional structure of local vegetation. Further, these findings suggest compound-specific isotopic data for longer alkane homologs (C31, C33, C35) will proportionately represent non-woody vegetation and isotope measurements of C29 are more representative of woody vegetation. Thus, the combination of ACL and carbon isotope compositions should allow us to disentangle C3 woody, C3 non-woody, and C4 non-woody signals in terrestrial paleorecords. Application of this approach to the geologic record of Miocene C4 grassland expansion in the US Great Plains and the Siwaliks in Pakistan illustrate two very different transition scenarios. Alkane-specific isotopic data indicate C4 grasslands appeared 2.5 Ma in the Great Plains and 6.5 Ma in the Siwaliks, and ACL analysis indicates that this transition involved the replacement of woody vegetation in the US and the replacement of C3 grasses in Pakistan. Our analysis illustrates that, consistent with differences in the timing of C4 grassland, the drivers of change were likely not the same in these regions. Oxygen isotope records suggest that the more recent transition in the Great Plains was associated with climate cooling and possibly changes in disturbance regimes and that the transition in the Siwaliks was likely associated with warming and drying.

  6. Hydrocarbon degradation, plant colonization and gene expression of alkane degradation genes by endophytic Enterobacter ludwigii strains

    Energy Technology Data Exchange (ETDEWEB)

    Yousaf, Sohail [AIT Austrian Institute of Technology GmbH, Bioresources Unit, A-2444 Seibersdorf (Austria); Afzal, Muhammad [AIT Austrian Institute of Technology GmbH, Bioresources Unit, A-2444 Seibersdorf (Austria); National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad (Pakistan); Reichenauer, Thomas G. [AIT Austrian Institute of Technology GmbH, Environmental Resources and Technologies Unit, A-2444 Seibersdorf (Austria); Brady, Carrie L. [Forestry and Agricultural Biotechnology Institute, Department of Microbiology and Plant Pathology, University of Pretoria, Pretoria (South Africa); Sessitsch, Angela, E-mail: angela.sessitsch@ait.ac.at [AIT Austrian Institute of Technology GmbH, Bioresources Unit, A-2444 Seibersdorf (Austria)

    2011-10-15

    The genus Enterobacter comprises a range of beneficial plant-associated bacteria showing plant growth promotion. Enterobacter ludwigii belongs to the Enterobacter cloacae complex and has been reported to include human pathogens but also plant-associated strains with plant beneficial capacities. To assess the role of Enterobacter endophytes in hydrocarbon degradation, plant colonization, abundance and expression of CYP153 genes in different plant compartments, three plant species (Italian ryegrass, birdsfoot trefoil and alfalfa) were grown in sterile soil spiked with 1% diesel and inoculated with three endophytic E. ludwigii strains. Results showed that all strains were capable of hydrocarbon degradation and efficiently colonized the rhizosphere and plant interior. Two strains, ISI10-3 and BRI10-9, showed highest degradation rates of diesel fuel up to 68% and performed best in combination with Italian ryegrass and alfalfa. All strains expressed the CYP153 gene in all plant compartments, indicating an active role in degradation of diesel in association with plants. - Highlights: > E. ludwigii strains efficiently colonized plants in a non-sterile soil environment. > E. ludwigii strains efficiently expressed alkane degradation genes in plants. > E. ludwigii efficiently degraded alkane contaminations and promoted plant growth. > E. ludwigii interacted more effectively with Italian ryegrass than with other plants. > Degradation activity varied with plant and microbial genotype as well as with time. - Enterobacter ludwigii strains belonging to the E. cloacae complex are able to efficiently degrade alkanes when associated with plants and to promote plant growth.

  7. Catalytic conversion of light alkanes phase II. Topical report, January 1990--January 1993

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-12-31

    The Topical Report on Phase II of the project entitled, Catalytic Conversion of Light Alkanes reviews work done between January 1, 1990 and September 30, 1992 on the Cooperative Agreement. The mission of this work is to devise a new catalyst which can be used in a simple economic process to convert the light alkanes in natural gas to oxygenate products which can either be used as clean-burning, high octane liquid fuels, as fuel components or as precursors to liquid hydrocarbon transportation fuel. This Topical Report documents our efforts to design, prepare, characterize and test novel catalysts for the mild selective reaction of light hydrocarbons with air or oxygen to produce alcohols directly. These catalysts are designed to form active metal oxo (MO) species and to be uniquely active for the homolytic cleavage of the carbon-hydrogen bonds in light alkanes producing intermediates which can form alcohols. Research on the Cooperative Agreement is divided into three Phases relating to three molecular environments for the active catalytic species that we are trying to generate. In this report we present our work on catalysts which have oxidation-active metals in polyoxoanions (PHASE II).

  8. Supercooling Suppression of Microencapsulated n-Alkanes by Introducing an Organic Gelator

    Institute of Scientific and Technical Information of China (English)

    ZHU Kong-ying; WANG Shuang; QI Heng-zhi; LI Hui; ZHAO Yun-hui; YUAN Xiao-yan

    2012-01-01

    Supercooling of the microencapsulated phase change materials(PCMs) during cooling usually happens.This phenomenon can interfere with heat transfer and is necessary to further overcome.In this study,melamine-formaldehyde microcapsules containing two n-alkane PCMs,namely,n-dodecane(C12) or n-tetradecane(C14)were prepared by in situ polymerization.A small amount of n-hexatriacontane(C36) was introduced as an organic gelator into the core of microcapsules to cope with the supercooling problem.Analyses demonstrate that supcrcooling of the microencapsulated C12 or C14 was significantly suppressed by adding 3%(mass fraction) C36,without changing the spherical morphology and dispersibility.It could be also found that the enthalpy of microencapsulated C12 or C14 containing C36 was similar to that of microencapsulated n-alkanes without C36,whereas the difference between onsets of crystallization and melting(degree of supercooling) is similar to that of those of pure n-alkanes,suggesting the remarkable suppression ability of the organic gelator on supercooling.

  9. Induction and development of the oil emulsifying system in an alkane oxidizing Rhodococcus species

    Energy Technology Data Exchange (ETDEWEB)

    Bredholt, H.; Eimhjellen, K. [Norwegian Univ. of Science and Technology, Dept. of Biotechnology, Trondheim, (Norway)

    1999-08-01

    There is a potential use of oil emulsifying bacteria for the clean-up of oil-contaminated natural environments, and oil transport and storage systems. The control mechanisms of the emulsifying abilities in these bacteria are important in relation to the optimization of such processes. A study was conducted to investigate the physiological criteria for the formation of the emulsifying activity in Rhodococcus sp. strain 094, which forms a hydrophobic cell surface when cultivated on alkanes, permitting oil-associated exponential growth. The ability of this bacteria to produce oil emulsifying agents is clearly inducible by crude oil or a number of single hydrophobic compounds. Before the cells are able to emulsify the oil, they must pass through a relatively short induction period followed by a longer period of synthesis of hydrophobic surface parts, coinciding with cell proliferation. The latter is due to the required coordination with new cell wall synthesis. If the cells are allowed to produce sufficient amounts of hydrophobic cell surface parts, they commence to emulsify the oil efficiently when the hydrophobic factor is released from the cell surface as part of their change to a more hydrophillic state. All the positive inducers were hydrophobic alkyl derivatives, and with one exception, also substrate for growth. Many of the better inducers were alkanes, and would require an alkane oxidizing system to be used by the cells. 14 ref., 2 tabs., 3 figs.

  10. Catalytic conversion of light alkanes: Quarterly report, January 1-March 31, 1992

    Energy Technology Data Exchange (ETDEWEB)

    Biscardi, J.; Bowden, P.T.; Durante, V.A.; Ellis, P.E. Jr.; Gray, H.B.; Gorbey, R.G.; Hayes, R.C.; Hodge, J.; Hughes, M.; Langdale, W.A.; Lyons, J.E.; Marcus, B.; Messick, D.; Merrill, R.A.; Moore, F.A.; Myers, H.K. Jr.; Seitzer, W.H.; Shaikh, S.N.; Tsao, W.H.; Wagner, R.W.; Warren, R.W.; Wijesekera, T.P.

    1997-05-01

    The first Quarterly Report of 1992 on the Catalytic Conversion of Light Alkanes reviews the work done between January 1. 1992 and March 31, 1992 on the Cooperative Agreement. The mission of this work is to devise a new catalyst which can be used in a simple economic process to convert the light alkanes in natural gas to oxygenate products which can either be used as clean-burning, high octane liquid fuels, as fuel components or as precursors to liquid hydrocarbon transportation fuel. During the past quarter we have continued to design, prepare, characterize and test novel catalysts for the mild selective reaction of light hydrocarbons with air or oxygen to produce alcohols directly. These catalysts are designed to form active metal oxo (MO) species and to be uniquely active for the homolytic cleavage of the carbon-hydrogen bonds in light alkanes producing intermediates which can form alcohols. We continue to investigate three molecular environments for the active catalytic species that we are trying to generate: electron-deficient porphryinic macrocycles (PHASE I), polyoxometallates (PHASE II), and regular oxidic lattices including zeolites and related structures as well as other molecular surface structures having metal oxo groups (PHASE III).

  11. Calculations of gamma-ray spectral profiles of linear alkanes in the positron annihilation process

    CERN Document Server

    Ma, X G

    2014-01-01

    The positron-electron annihilation gamma-ray spectra of linear alkanes CnH2n+2 (n=1-12) have been studied systematically. A profile quality (PQ) parameter, is introduced to assess the agreement between the obtained theoretical profiles and the experimental measurements in the entire region of energy shift of the spectra. Together with the Doppler shift of the gamma-ray spectra, the two parameters,PQ and Doppler shift, are able to provide a more comprehensive assessment of the calculated gamma-ray spectra with respect to available experiment. Applying the recently developed docking model, the present study determines the positrophilic electrons for individual alkanes from which the gamma-ray spectral profiles are calculated. The results achieve an excellent agreement with experiment, not only with respect to the Doppler shift, but also with respect to the gamma-ray profiles in the photon energy region up to 5 keV. The study further calculates the gamma-ray spectra of other linear alkanes in the series without ...

  12. Critical constants and acentric factors for long-chain alkanes suitable for corresponding states applications

    DEFF Research Database (Denmark)

    Kontogeorgis, Georgios; Dimitrios, Tassios

    1997-01-01

    Several methods for the estimation of the critical temperature T-c, the critical pressure P-c, and the acentric factor omega for long-chain n-alkanes are reviewed and evaluated for the prediction of vapor pressures using Corresponding States (CS) methods, like the Lee-Kesler equation and the cubic...... equations of state. Most reliable and recent literature methods proposed for the estimation of the acentric factor of heavy alkanes yield similar values and the emphasis is, thus, given to the determination of the best sets of T-c and P-c. Various extrapolation schemes proposed for this purpose and several...... general group-contribution methods were investigated in this work. The correlations proposed by K. Magoulas and D. Tassios, Thermophysical properties of n-alkanes from C-1 to C-20 and their prediction for higher ones, Fluid Phase Equilibria, 56 ( 1990) 119-140; A.S. Teja, R.J. Lee, D.J. Rosenthal, M...

  13. Molecular dynamics simulations of layers of linear and branched alkanes under shear

    Science.gov (United States)

    Soza, P.; Hansen, F. Y.; Taub, H.; Volkmann, U. G.

    2008-03-01

    We have previously studied the equilibrium structure and dynamical excitations in films of the linear alkane tetracosane (n-C24H50) and the branched alkane squalane (C30H62) in great detail^2. Here we report the results of nonequilibrium molecular dynamics simulations of these systems in order to compare the rheological properties of alkanes of the same length but with different architecture. The simulations were done in the NVT ensemble using the reverse nonequilibrium algorithm proposed by F. Müller-Plathe et al.^3. The viscosity was calculated for different shear rates and compared with experimental values. Different structural parameters such as the mean end-to-end distance, the radius of gyration, and the angle of alignment of the molecules with the flow were studied as a function of the shear rate. ^2A.D. Enevoldsen et al., J. Chem. Phys. 126, 104703-10 (2007); 126, 104704-17 (2007). ^3F. Müller-Plathe et al., Phys. Rev. E, 59, 4894 (1998)

  14. Conversion of raw lignocellulosic biomass into branched long-chain alkanes through three tandem steps.

    Science.gov (United States)

    Li, Chunrui; Ding, Daqian; Xia, Qineng; Liu, Xiaohui; Wang, Yanqin

    2016-07-07

    Synthesis of branched long-chain alkanes from renewable biomass has attracted intensive interest in recent years, but the feedstock for this synthesis is restricted to platform chemicals. Here, we develop an effective and energy-efficient process to convert raw lignocellulosic biomass (e.g., corncob) into branched diesel-range alkanes through three tandem steps for the first time. Furfural and isopropyl levulinate (LA ester) were prepared from hemicellulose and cellulose fractions of corncob in toluene/water biphasic system with added isopropanol, which was followed by double aldol condensation of furfural with LA ester into C15 oxygenates and the final hydrodeoxygenation of C15 oxygenates into branched long-chain alkanes. The core point of this tandem process is the addition of isopropanol in the first step, which enables the spontaneous transfer of levulinic acid (LA) into the toluene phase in the form of LA ester through esterification, resulting in LA ester co-existing with furfural in the same phase, which is the basis for double aldol condensation in the toluene phase. Moreover, the acidic aqueous phase and toluene can be reused and the residues, including lignin and humins in aqueous phase, can be separated and carbonized to porous carbon materials.

  15. Catalytic conversion of light alkanes. Quarterly progress report, April 1--June 30, 1992

    Energy Technology Data Exchange (ETDEWEB)

    Lyons, J.E.

    1992-06-30

    The second Quarterly Report of 1992 on the Catalytic Conversion of Light Alkanes reviews the work done between April 1, 1992 and June 31, 1992 on the Cooperative Agreement. The mission of this work is to devise a new catalyst which can be used in a simple economic process to convert the light alkanes in natural gas to oxygenate products that can either be used as clean-burning, high octane liquid fuels, as fuel components or as precursors to liquid hydrocarbon uwspomdon fuel. During the past quarter we have continued to design, prepare, characterize and test novel catalysts for the mild selective reaction of light hydrocarbons with air or oxygen to produce alcohols directly. These catalysts are designed to form active metal oxo (MO) species and to be uniquely active for the homolytic cleavage of the carbon-hydrogen bonds in light alkanes producing intermediates which can form alcohols. We continue to investigate three molecular environments for the active catalytic species that we are trying to generate: electron-deficient macrocycles (PHASE I), polyoxometallates (PHASE II), and regular oxidic lattices including zeolites and related structures as well as other molecular surface structures having metal oxo groups (PHASE I).

  16. Fidelity of fossil n-alkanes from leaf to paleosol and applications to the Paleocene-Eocene Thermal Maximum

    Science.gov (United States)

    Bush, R. T.; McInerney, F. A.; Baczynski, A. A.; Wing, S. L.

    2011-12-01

    Long chain n-alkanes (C21-C35) are well-known as biomarkers of terrestrial plants. They can be preserved across a wide range of terrestrial and marine environments, survive in the sedimentary record for millions of years, and can serve as proxies for ancient environments. Most n-alkane records are derived from sediments rather than directly from fossil leaves. However, little is known about the fidelity of the n-alkane record: how and where leaf preservation relates to n-alkane preservation and how patterns of n-alkane carbon isotope ratios (δ13C) compare to living relatives. To examine these questions, we analyzed n-alkanes from fluvial sediments and individual leaf fossils collected in the Bighorn Basin, Wyoming, across the Paleocene-Eocene Thermal Maximum (PETM) carbon isotope excursion. We assessed the fidelity of the n-alkane signature from individual fossil leaves via three separate means. 1) Spatial variations were assessed by comparing n-alkane concentrations on a fossil leaf and in sediments both directly adjacent to the leaf and farther away. Absolute concentrations were greater within the compression fossil than in the directly adjacent sediment, which were in turn greater than in more distant sediment. 2) n-Alkane abundances and distributions were examined in fossil leaves having a range of preservational quality, from fossils with intact cuticle to carbonized fossils lacking cuticle and higher-order venation. The best preserved fossils preserved a higher concentration of n-alkanes and showed the most similar n-alkane distribution to living relatives. However, a strong odd over even predominance suggests a relatively unmodified plant source occurred in all samples regardless of preservation state. 3) n-Alkane δ13C values were measured for both fossil leaves and their living relatives. Both the saw-tooth pattern of δ13C values between odd and even chain lengths and the general decrease in δ13C values with increasing chain length are consistent with

  17. Structure and Phase Transitions of Monolayers of Intermediate-length n-alkanes on Graphite Studied by Neutron Diffraction and Molecular Dynamics Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Taub, H. [University of Missouri, Columbia; Hansen, F.Y. [Technical University of Denmark; Diama, Amand [National University of the Ivory Coast; Matthies, Blake [Goodyear Tire and Rubber Company, The; Criswell, Leah [University of Missouri, Columbia; Mo, Haiding [Advanced Optowave Corporation; Bai, M [University of Missouri, Columbia; Herwig, Kenneth W [ORNL

    2009-01-01

    We present evidence from neutron diffraction measurements and molecular dynamics (MD) simulations of three different monolayer phases of the intermediate-length alkanes tetracosane (n-C(24)H(50) denoted as C24) and dotriacontane (n-C(32)H(66) denoted as C32) adsorbed on a graphite basal-plane surface. Our measurements indicate that the two monolayer films differ principally in the transition temperatures between phases. At the lowest temperatures, both C24 and C32 form a crystalline monolayer phase with a rectangular-centered (RC) structure. The two sublattices of the RC structure each consists of parallel rows of molecules in their all-trans conformation aligned with their long axis parallel to the surface and forming so-called lamellas of width approximately equal to the all-trans length of the molecule. The RC structure is uniaxially commensurate with the graphite surface in its [110] direction such that the distance between molecular rows in a lamella is 4.26 A=sqrt[3a(g)], where a(g)=2.46 A is the lattice constant of the graphite basal plane. Molecules in adjacent rows of a lamella alternate in orientation between the carbon skeletal plane being parallel and perpendicular to the graphite surface. Upon heating, the crystalline monolayers transform to a 'smectic' phase in which the inter-row spacing within a lamella expands by approximately 10% and the molecules are predominantly oriented with the carbon skeletal plane parallel to the graphite surface. In the smectic phase, the MD simulations show evidence of broadening of the lamella boundaries as a result of molecules diffusing parallel to their long axis. At still higher temperatures, they indicate that the introduction of gauche defects into the alkane chains drives a melting transition to a monolayer fluid phase as reported previously.

  18. Structure and phase transitions of monolayers of intermediate-length n-alkanes on graphite studied by neutron diffraction and molecular dynamics simulation.

    Science.gov (United States)

    Diama, A; Matthies, B; Herwig, K W; Hansen, F Y; Criswell, L; Mo, H; Bai, M; Taub, H

    2009-08-28

    We present evidence from neutron diffraction measurements and molecular dynamics (MD) simulations of three different monolayer phases of the intermediate-length alkanes tetracosane (n-C(24)H(50) denoted as C24) and dotriacontane (n-C(32)H(66) denoted as C32) adsorbed on a graphite basal-plane surface. Our measurements indicate that the two monolayer films differ principally in the transition temperatures between phases. At the lowest temperatures, both C24 and C32 form a crystalline monolayer phase with a rectangular-centered (RC) structure. The two sublattices of the RC structure each consists of parallel rows of molecules in their all-trans conformation aligned with their long axis parallel to the surface and forming so-called lamellas of width approximately equal to the all-trans length of the molecule. The RC structure is uniaxially commensurate with the graphite surface in its [110] direction such that the distance between molecular rows in a lamella is 4.26 A=sqrt[3a(g)], where a(g)=2.46 A is the lattice constant of the graphite basal plane. Molecules in adjacent rows of a lamella alternate in orientation between the carbon skeletal plane being parallel and perpendicular to the graphite surface. Upon heating, the crystalline monolayers transform to a "smectic" phase in which the inter-row spacing within a lamella expands by approximately 10% and the molecules are predominantly oriented with the carbon skeletal plane parallel to the graphite surface. In the smectic phase, the MD simulations show evidence of broadening of the lamella boundaries as a result of molecules diffusing parallel to their long axis. At still higher temperatures, they indicate that the introduction of gauche defects into the alkane chains drives a melting transition to a monolayer fluid phase as reported previously.

  19. Stable hydrogen isotope composition of n-alkanes in urban atmospheric aerosols in Taiyuan, China

    Science.gov (United States)

    Bai, Huiling; Li, Yinghui; Peng, Lin; Liu, Xiangkai; Liu, Xiaofeng; Song, Chongfang; Mu, Ling

    2017-03-01

    The hydrogen isotope compositions (δD) of n-alkanes associated with particulate matter with a diameter of ≤10 μm from Taiyuan, China, during heating and non-heating periods were measured via gas chromatography-isotope ratio mass spectrometry to reveal the spatial and temporal characteristics of five functional zones and to provide another constraint on atmospheric pollutants. The δD values of n-C16 to n-C31 during the heating and non-heating periods ranged from -235.9‰ to -119.8‰ and from -231.3‰ to -129.2‰, respectively, but these similar spans had different distribution features. During the heating period, the δD distributions between non-central heating and commercial districts were consistent, as were those between residential and industrial districts; the n-alkanes came from two or more types of emission sources. Coal soot might be the primary local emission source, but not the only source. During the non-heating period, the n-alkanes of n-C16 to n-C20 were more depleted in D with the increasing carbon number in all functional zones, but there was no rule for n-C21 to n-C31. Specifically, coal soot and vehicle exhaust might be the primary sources of n-alkanes for non-central heating districts in the heating and non-heating periods, respectively, according to the δD distribution of n-C18 to n-C22; gasoline vehicle exhaust might be an n-alkane source, and the hydrogen isotope fractionation effect during the condensation process should be a pollution mechanism for the commercial district during the heating period; the δD distribution difference of n-C16 to n-C18 between the two periods in the residential and industrial districts was consistent, which indicates a similar source of fossil fuel combustion and a similar isotope fractionation effect during the non-heating period.

  20. Allochthonous carbon hypothesis for bulk OM and n-alkane PETM carbon isotope discrepancies

    Science.gov (United States)

    Baczynski, A. A.; McInerney, F. A.; Wing, S. L.; Kraus, M. J.; Fricke, H. C.

    2011-12-01

    The Paleocene-Eocene Thermal Maximum (PETM), a period of abrupt, transient, and large-scale global warming fueled by a large release of isotopically light carbon, is a relevant analogue for episodes of rapid global warming and recovery. The PETM is recorded in pedogenic carbonate, bulk organic matter, and n-alkanes as a prominent negative carbon isotope excursion (CIE) in paleosols exposed in the Bighorn Basin, WY. Here we present a composite stable carbon isotope record from n-alkanes and dispersed soil organic δ13C records from five individual sections that span the PETM in the southeastern Bighorn Basin. Four sections are from a 10km transect in the Cabin Fork area and one section was collected at Sand Creek Divide. These five new dispersed organic carbon (DOC) isotope records are compared to the previously published Polecat Bench (Magioncalda et al. 2004) and Honeycombs (Yans et al. 2006) isotope records. The high-resolution n-alkane curve shows an abrupt, negative shift in δ13C values, an extended CIE body, and a rapid recovery to more positive δ13C values. Although the five DOC records show similarly abrupt negative shifts in δ13C values, the DOC CIEs are compressed, smaller in magnitude, and return to more positive δ13C values more gradually relative to the n-alkane record. Moreover, the stratigraphic thickness of the body of the excursion and the pattern of the recovery phase are not consistent among the five DOC records. We modeled predicted DOC δ13C values from the n-alkane record by applying enrichment factors based on modern plants to the n-alkane δ13C values. The anomaly, difference between the expected and observed DOC δ13C values, was calculated for the PETM records and compared to weight percent carbon and grain size. There is no correlation between pre- and post-PETM anomaly values and grain size or weight percent carbon. PETM anomaly values, however, do trend with both grain size and weight percent carbon. The largest PETM anomaly values

  1. Decimal fraction representations are not distinct from natural number representations - evidence from a combined eye-tracking and computational modeling approach.

    Science.gov (United States)

    Huber, Stefan; Klein, Elise; Willmes, Klaus; Nuerk, Hans-Christoph; Moeller, Korbinian

    2014-01-01

    Decimal fractions comply with the base-10 notational system of natural Arabic numbers. Nevertheless, recent research suggested that decimal fractions may be represented differently than natural numbers because two number processing effects (i.e., semantic interference and compatibility effects) differed in their size between decimal fractions and natural numbers. In the present study, we examined whether these differences indeed indicate that decimal fractions are represented differently from natural numbers. Therefore, we provided an alternative explanation for the semantic congruity effect, namely a string length congruity effect. Moreover, we suggest that the smaller compatibility effect for decimal fractions compared to natural numbers was driven by differences in processing strategy (sequential vs. parallel). To evaluate this claim, we manipulated the tenth and hundredth digits in a magnitude comparison task with participants' eye movements recorded, while the unit digits remained identical. In addition, we evaluated whether our empirical findings could be simulated by an extended version of our computational model originally developed to simulate magnitude comparisons of two-digit natural numbers. In the eye-tracking study, we found evidence that participants processed decimal fractions more sequentially than natural numbers because of the identical leading digit. Importantly, our model was able to account for the smaller compatibility effect found for decimal fractions. Moreover, string length congruity was an alternative account for the prolonged reaction times for incongruent decimal pairs. Consequently, we suggest that representations of natural numbers and decimal fractions do not differ.

  2. Decimal representations are not distinct from natural number representations – Evidence from a combined eye-tracking and computational modelling approach

    Directory of Open Access Journals (Sweden)

    Stefan eHuber

    2014-04-01

    Full Text Available Decimal fractions comply with the base-10 notational system of natural Arabic numbers. Nevertheless, recent research suggested that decimal fractions may be represented differently than natural numbers because two number processing effects (i.e., semantic interference and compatibility effects differed in their size between decimal fractions and natural numbers. In the present study, we examined whether these differences indeed indicate that decimal fractions are represented differently from natural numbers. Therefore, we provided an alternative explanation for the semantic congruity effect, namely a string length congruity effect. Moreover, we suggest that the smaller compatibility effect for decimal fractions compared to natural numbers was driven by differences in processing strategy (sequential vs. parallel.To evaluate this claim, we manipulated the tenth and hundredth digits in a magnitude comparison task with participants' eye movements recorded, while the unit digits remained identical. In addition, we evaluated whether our empirical findings could be simulated by an extended version of our computational model originally developed to simulate magnitude comparisons of two-digit natural numbers. In the eye-tracking study, we found evidence that participants processed decimal fractions more sequentially than natural numbers because of the identical leading digit. Importantly, our model was able to account for the smaller compatibility effect found for decimal fractions. Moreover, string length congruity was an alternative account for the prolonged reaction times for incongruent decimal pairs. Consequently, we suggest that representations of natural numbers and decimal fractions do not differ.

  3. Distribution and significance of C40+ alkanes in the extracts of Cretaceous source rocks from the Songliao Basin

    Institute of Scientific and Technical Information of China (English)

    FENG; ZiHui; FANG; Wei; ZHANG; JuHe; LI; ZhenGuang; HUANG; ChunYan; WANG; Xue; ZHAO; QinLing; HUO; QiuLi

    2007-01-01

    Source rock extracts and crude oils from the Songliao Basin were analyzed by high-temperature gas chromatography (HTGC), gas chromatography-mass spectrometry (HTGC-MS) and gas chromatography-isotope ratio-mass spectrometry (GC-IRMS), for high molecular-weight alkanes. The distributions of n-alkanes in the Nenjiang Formation extracts are in the C14―C63 range; a bimodal distribution occurs in the and C21―40 regions. The C30―C37 n-alkanes are accompanied by C29―C35 hopanes, whereas the high molecular-weight C45―C47 n-alkanes co-occur with abundant isoalkanes, alkylcyclohexanes and alkylcyclopentanes. The high δ13C values of the n-alkanes and the microscopic maceral compositions indicate a highly diversified organic source input for the Nenjiang Formation source rocks, ranging from aquatic plants, blue alge-bacteria, to land plant material. In contrast, n-alkanes in the rock extracts of the Qingshankou Formation are characterized by a single modal distribution, with relatively low abundances of C29―C35 hopanes, but high molecular-weight isoalkanes, alkylcyclohexanes and alkylcyclopentanes. The relatively low δ13C values of C22―C44 n-alkanes and organic material compositions indicate that the source rocks in the Qingshankou Formation contain dominantly type I algal organic matter. The relative abundance of compounds in source rocks changes little at low maturity stage, but decreases drastically at higher maturity levels, with a concurrent reduction in the odd/even carbon predominance. In crude oils, in contrast, the relative abundance of compounds appears to relate closely with the oil source and oil viscosity.

  4. Podemos prever a taxa de cambio brasileira? Evidência empírica utilizando inteligência computacional e modelos econométricos Can we forecast Brazilian exchange rates? Empirical evidences using computational intelligence and econometric models

    Directory of Open Access Journals (Sweden)

    Leandro dos Santos Coelho

    2008-12-01

    Full Text Available As abordagens de inteligência computacional, tais como sistemas nebulosos e redes neurais artificiais, têm-se gradualmente estabelecido como ferramentas robustas para a tarefa de aproximação de sistemas não-lineares complexos e previsão de séries temporais. Em aplicações envolvendo a área de Finanças, evidências empíricas anteriores indicam que modelos de inteligência computacional são mais precisos, dada sua maior capacidade em capturar não-linearidades e outros fatos estilizados presentes em séries financeiras. Nesse sentido, este artigo investiga a hipótese de que os modelos matemáticos de redes neurais perceptron multicamadas, redes neurais função de base radial e o sistema nebuloso Takagi-Sugeno (TAKAGI; SUGENO, 1985 são capazes de fornecer uma previsão fora-da-amostra mais acurada que os modelos auto-regressivos de médias móveis (ARMA e auto-regressivo de médias móveis supondo heterocedasticidade condicional auto-regressiva (ARMA-GARCH. O desempenho de previsão um-passo-à-frente dos modelos foi comparado utilizando-se séries de retorno da taxa de câmbio real/dólar (R$/US$ com freqüências de 15 minutos, 60 minutos, 120 minutos, diária e semanal. Resultados indicam que o desempenho dos modelos está diretamente relacionado à freqüência observada das séries. Além disso, os modelos de redes neurais obtiveram um desempenho superior em relação aos demais modelos considerados. A avaliação da estratégia de negociação estabelecida com base nas previsões geradas pelos modelos indicou que estratégias baseadas em modelos de redes neurais forneceram retornos superiores em relação àquelas baseadas em modelos ARMA e ARMA-GARCH e também em relação à estratégia buy-and-hold.Computational intelligence approaches, such as artificial neural networks and fuzzy systems, have become popular tools in approximating complicated nonlinear systems and time series forecasting. In Finance applications, there is

  5. Overexpression of Arabidopsis ECERIFERUM1 promotes wax very-long-chain alkane biosynthesis and influences plant response to biotic and abiotic stresses.

    Science.gov (United States)

    Bourdenx, Brice; Bernard, Amélie; Domergue, Frédéric; Pascal, Stéphanie; Léger, Amandine; Roby, Dominique; Pervent, Marjorie; Vile, Denis; Haslam, Richard P; Napier, Johnathan A; Lessire, René; Joubès, Jérôme

    2011-05-01

    Land plant aerial organs are covered by a hydrophobic layer called the cuticle that serves as a waterproof barrier protecting plants against desiccation, ultraviolet radiation, and pathogens. Cuticle consists of a cutin matrix as well as cuticular waxes in which very-long-chain (VLC) alkanes are the major components, representing up to 70% of the total wax content in Arabidopsis (Arabidopsis thaliana) leaves. However, despite its major involvement in cuticle formation, the alkane-forming pathway is still largely unknown. To address this deficiency, we report here the characterization of the Arabidopsis ECERIFERUM1 (CER1) gene predicted to encode an enzyme involved in alkane biosynthesis. Analysis of CER1 expression showed that CER1 is specifically expressed in the epidermis of aerial organs and coexpressed with other genes of the alkane-forming pathway. Modification of CER1 expression in transgenic plants specifically affects VLC alkane biosynthesis: waxes of TDNA insertional mutant alleles are devoid of VLC alkanes and derivatives, whereas CER1 overexpression dramatically increases the production of the odd-carbon-numbered alkanes together with a substantial accumulation of iso-branched alkanes. We also showed that CER1 expression is induced by osmotic stresses and regulated by abscisic acid. Furthermore, CER1-overexpressing plants showed reduced cuticle permeability together with reduced soil water deficit susceptibility. However, CER1 overexpression increased susceptibility to bacterial and fungal pathogens. Taken together, these results demonstrate that CER1 controls alkane biosynthesis and is highly linked to responses to biotic and abiotic stresses.

  6. Methyl ketones in high altitude Ecuadorian Andosols confirm excellent conservation of plant-specific n-alkane patterns

    Science.gov (United States)

    Jansen, B.; Nierop, K. G. J.

    2009-04-01

    Montane forest composition and specifically the position of the upper forest line (UFL) is very sensitive to climate change and human interference. As a consequence, reconstructions of past altitudinal UFL dynamics and forest species composition are crucial instruments to infer relationships between climate change and vegetation dynamics, and assess the impact of (pre)historic human settlement. One of the most detailed methods available to date to reconstruct past vegetation dynamics is the analysis of fossil pollen. Unfortunately, fossil pollen analysis does not distinguish beyond family or generic level in most cases, while its spatial resolution is limited amongst others by windblown dispersal of pollen, affecting the accuracy of pollen based reconstructions of UFL positions. To overcome these limitations, we developed a new method based on the analysis of plant-specific groups of biomarkers preserved in suitable archives, such as peat deposits, that are unravelled into the plant species of origin by the newly developed VERHIB model. In a study of UFL positions in the Northern Ecuadorian Andes we found longer chain-length n-alkanes, (C19-C35) to occur in plant-specific patterns in the dominant vegetation in the area as well as preliminary soil and peat samples. A crucial factor in determining the applicability of these n-alkanes as biomarkers for past vegetation is their preservation in soils and peat deposits. Therefore, we investigated the preservation of C19-C35 n-alkanes in a peat core and in five excavations along an altitudinal transect (3500-3860 m.a.s.l) in the study area. We were able to establish that n-methyl ketones are the main degradation product of the n-alkanes in question, while the degradation of the n-alkanes was the main source of the n-methyl ketones. This allowed us to use the relationship between the concentrations and carbon chain length patterns of n-alkanes and n-methyl ketones to assess possible (selective) degradation of the n-alkanes

  7. Comprehensive chemical kinetic modeling of the oxidation of C8 and larger n-alkanes and 2-methylalkanes

    Energy Technology Data Exchange (ETDEWEB)

    Sarathy, S M; Westbrook, C K; Pitz, W J; Mehl, M; Togbe, C; Dagaut, P; Wang, H; Oehlschlaeger, M; NIemann, U; Seshadri, K; Veloo, P S; Ji, C; Egolfopoulos, F; Lu, T

    2011-03-16

    Conventional petroleum jet and diesel fuels, as well as alternative Fischer-Tropsch (FT) fuels and hydrotreated renewable jet (HRJ) fuels, contain high molecular weight lightly branched alkanes (i.e., methylalkanes) and straight chain alkanes (n-alkanes). Improving the combustion of these fuels in practical applications requires a fundamental understanding of large hydrocarbon combustion chemistry. This research project presents a detailed and reduced chemical kinetic mechanism for singly methylated iso-alkanes (i.e., 2-methylalkanes) ranging from C{sub 8} to C{sub 20}. The mechanism also includes an updated version of our previously published C{sub 8} to C{sub 16} n-alkanes model. The complete detailed mechanism contains approximately 7,200 species 31,400 reactions. The proposed model is validated against new experimental data from a variety of fundamental combustion devices including premixed and nonpremixed flames, perfectly stirred reactors and shock tubes. This new model is used to show how the presence of a methyl branch affects important combustion properties such as laminar flame propagation, ignition, and species formation.

  8. High molecular weight (C35+)n-alkanes of Neogene heavily biodegraded oil in the Qianmiqiao region, North China

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    With wax content of 1.62%, heavy oil has been produced from the sandstone reservoirs of Neogene Guantao Formation (Ng1Ⅲ). In the GC and GC-MS RIC profiles of its aliphatic fraction, n-alkanes are totally lost, which shows the result of heavy biodegradedation. However, the remaining trace C13-C36 n-alkanes can be still seen from its m/z 85 mass chromatogram. In addition, a complete series of C35-C73 high molecular weight (HMW) n-alkanes was detected by high-temperature gas chromatography (HTGC). The HMW n-alkane series shows a normal distribution pattern, a major peak at nC43, obvious odd-carbon-number predominance, CPI37-55 and OEP45-49 values up to 1.17 and 1.16-1.20 respectively. The present study not only has conformed the strong resistibility of HMW n-alkanes to biodegradation in crude oils as concluded by previous researchers, but also has provided some significant information on source input and maturity for the heavily biodegraded oil in the Qianmiqiao region.

  9. Arbuscular mycorrhizal wheat inoculation promotes alkane and polycyclic aromatic hydrocarbon biodegradation: Microcosm experiment on aged-contaminated soil.

    Science.gov (United States)

    Ingrid, Lenoir; Lounès-Hadj Sahraoui, Anissa; Frédéric, Laruelle; Yolande, Dalpé; Joël, Fontaine

    2016-06-01

    Very few studies reported the potential of arbuscular mycorrhizal symbiosis to dissipate hydrocarbons in aged polluted soils. The present work aims to study the efficiency of arbuscular mycorrhizal colonized wheat plants in the dissipation of alkanes and polycyclic aromatic hydrocarbons (PAHs). Our results demonstrated that the inoculation of wheat with Rhizophagus irregularis allowed a better dissipation of PAHs and alkanes after 16 weeks of culture by comparison to non-inoculated condition. These dissipations observed in the inoculated soil resulted from several processes: (i) a light adsorption on roots (0.5% for PAHs), (ii) a bioaccumulation in roots (5.7% for PAHs and 6.6% for alkanes), (iii) a transfer in shoots (0.4 for PAHs and 0.5% for alkanes) and mainly a biodegradation. Whereas PAHs and alkanes degradation rates were respectively estimated to 12 and 47% with non-inoculated wheat, their degradation rates reached 18 and 48% with inoculated wheat. The mycorrhizal inoculation induced an increase of Gram-positive and Gram-negative bacteria by 56 and 37% compared to the non-inoculated wheat. Moreover, an increase of peroxidase activity was assessed in mycorrhizal roots. Taken together, our findings suggested that mycorrhization led to a better hydrocarbon biodegradation in the aged-contaminated soil thanks to a stimulation of telluric bacteria and hydrocarbon metabolization in mycorrhizal roots.

  10. Clay minerals and metal oxides strongly influence the structure of alkane-degrading microbial communities during soil maturation.

    Science.gov (United States)

    Steinbach, Annelie; Schulz, Stefanie; Giebler, Julia; Schulz, Stephan; Pronk, Geertje J; Kögel-Knabner, Ingrid; Harms, Hauke; Wick, Lukas Y; Schloter, Michael

    2015-07-01

    Clay minerals, charcoal and metal oxides are essential parts of the soil matrix and strongly influence the formation of biogeochemical interfaces in soil. We investigated the role of these parental materials for the development of functional microbial guilds using the example of alkane-degrading bacteria harbouring the alkane monooxygenase gene (alkB) in artificial mixtures composed of different minerals and charcoal, sterile manure and a microbial inoculum extracted from an agricultural soil. We followed changes in abundance and community structure of alkane-degrading microbial communities after 3 and 12 months of soil maturation and in response to a subsequent 2-week plant litter addition. During maturation we observed an overall increasing divergence in community composition. The impact of metal oxides on alkane-degrading community structure increased during soil maturation, whereas the charcoal impact decreased from 3 to 12 months. Among the clay minerals illite influenced the community structure of alkB-harbouring bacteria significantly, but not montmorillonite. The litter application induced strong community shifts in soils, maturated for 12 months, towards functional guilds typical for younger maturation stages pointing to a resilience of the alkane-degradation function potentially fostered by an extant 'seed bank'.

  11. Role of cysteine residues in the structure, stability, and alkane producing activity of cyanobacterial aldehyde deformylating oxygenase.

    Directory of Open Access Journals (Sweden)

    Yuuki Hayashi

    Full Text Available Aldehyde deformylating oxygenase (AD is a key enzyme for alkane biosynthesis in cyanobacteria, and it can be used as a catalyst for alkane production in vitro and in vivo. However, three free Cys residues in AD may impair its catalytic activity by undesired disulfide bond formation and oxidation. To develop Cys-deficient mutants of AD, we examined the roles of the Cys residues in the structure, stability, and alkane producing activity of AD from Nostoc punctiforme PCC 73102 by systematic Cys-to-Ala/Ser mutagenesis. The C71A/S mutations reduced the hydrocarbon producing activity of AD and facilitated the formation of a dimer, indicating that the conserved Cys71, which is located in close proximity to the substrate-binding site, plays crucial roles in maintaining the activity, structure, and stability of AD. On the other hand, mutations at Cys107 and Cys117 did not affect the hydrocarbon producing activity of AD. Therefore, we propose that the C107A/C117A double mutant is preferable to wild type AD for alkane production and that the double mutant may be used as a pseudo-wild type protein for further improvement of the alkane producing activity of AD.

  12. Metabolism of hydrophobic carbon sources and regulation of it in n-alkane-assimilating yeast Yarrowia lipolytica.

    Science.gov (United States)

    Fukuda, Ryouichi

    2013-01-01

    A potent ability to assimilate hydrophobic compounds, including n-alkanes and fatty acids as carbon sources, is one of important characteristics of the yeast Yarrowia lipolytica, and has been studied for both basic microbiological interest and biotechnological applications. This review summarizes recent progress on the metabolism of n-alkanes and its transcriptional control in response to n-alkanes and to fatty acids in Y. lipolytica. In the metabolism of n-alkanes, cytochromes P450ALK catalyze their initial hydroxylation to fatty alcohols, which are subsequently converted to fatty acids and utilized. The transcription of ALK1, encoding a predominant cytochrome P450ALK, is regulated in response to n-alkanes by two basic helix-loop-helix transcription activators, Yas1p and Yas2p, and Opi1-family transcription repressor Yas3p. Transcription of the genes involved in fatty acid utilization and peroxisome biogenesis is controlled by Ctf1-family Zn2Cys6 type transcription factor Por1p in response to fatty acids in Y. lipolytica.

  13. Alkanes and alkenes in Mediterranean volcanic-hydrothermal systems: origins and geothermometry

    Science.gov (United States)

    Fiebig, Jens; D'Alessandro, Walter; Tassi, Franco; Woodland, Alan

    2010-05-01

    It is still a matter of debate if nature provides conditions for abiogenic production of hydrocarbons. Methane (C1) and the C2+ alkanes emanating from ultramafic hydrothermal systems such as Lost City have been considered to be abiogenic in origin, mainly because of the occurrence of an isotopic reversal between methane and the C2+hydrocarbons and C1/C2+ ratios >1000 [1]. Abiogenic production of methane has been postulated to occur under the relatively oxidizing redox conditions of continental-hydrothermal systems, too. It was observed that temperatures received from the H2-H2O-CO-CO2-CH4 geoindicator were coincident with temperatures derived from carbon isotope partitioning between CO2 and CH4in gases released from the Mediterranean volcanic-hydrothermal systems of Nisyros (Greece), Vesuvio and Ischia (both Italy) [2]. Such equilibrium pattern, if not fortuitous, can only be obtained if mantle- and marine limestone-derived CO2 is reduced to CH4. At Nisyros, observed C1/C2+ ratios from 300-4000 are in agreement with an abiogenic origin of the methane. Ethane and propane, however, were shown to be non-genetic with CO2 and methane. C1/C2 and C2/C3 distribution ratios may point to the admixture of small amounts of hydrocarbons deriving from the thermal decomposition of organic matter along with abiogenically equilibrated methane essentially devoid of the higher hydrocarbons [3]. Here, we provide new isotopic and hydrocarbon concentration data on several Mediterranean volcanic-hydrothermal systems, including Nisyros, Vesuvio, Ischia, Vulcano, Solfatara and Pantelleria. Wherever possible, we have extended our data set for the hydrogen isotope composition of CH4 and H2, n-alkane- and alkene/alkane-distribution ratios. At Nisyros, measured alkene/alkane- and H2/H2O concentration ratios confirm the attainment of equilibrium between CO2 and CH4. CO2 and CH4 appear to have equilibrated in the liquid phase at temperatures of ~360° C and redox conditions closely corresponding

  14. Experimental Evidence on the Effects of Home Computers on Academic Achievement among Schoolchildren. National Poverty Center Working Paper Series #13-02

    Science.gov (United States)

    Fairlie, Robert W.; Robinson, Jonathan

    2013-01-01

    Computers are an important part of modern education, yet large segments of the population--especially low-income and minority children--lack access to a computer at home. Does this impede educational achievement? We test this hypothesis by conducting the largest-ever field experiment involving the random provision of free computers for home use to…

  15. Critical wetting of n-alkanes on water; Mouillage critique des alcanes sur l`eau

    Energy Technology Data Exchange (ETDEWEB)

    Ragil, K.

    1996-10-18

    This study concerns the wetting properties of n-alkanes on water under thermodynamic equilibrium conditions, a problem that is interesting for the petroleum industry as well as for the fundamental understanding of wetting phenomena. An experimental study using ellipsometry reveals that pentane on water undergoes a continuous or critical wetting transition at a temperature equal to 53.1 deg. C. This is the first experimental observation of such a transition, confirming theoretical predictions made on this subject over ten years. This transition is characterized by a continuous and reversible evolution of the thickness of the film of pentane with temperature from a thick (but finite film) to a macroscopic film. The critical wetting transition occurs when the Hamaker constant of the system, which gives the net interaction between the two interfaces bounding the wetting layer of pentane in terms of the van der Waals forces, changes sign. A theoretical approach based on the Cahn-Landau theory, which takes into account long range forces (van der Waals forces), enables us to explain the mechanism of the critical wetting transition and to show that a first-order wetting transition should precede it. Because of their similar dispersive properties, linear alkanes could all be able to show such a succession of transitions. An ellipsometry study performed on a brine/hexane/vapor system confirms that a discontinuous transition from a thin microscopic film to a thick but finite adsorbed film takes place. THis study demonstrates that the wetting of alkanes on water is determined by subtle interplay between short range and long range forces, which can lead to an intermediary state between partial and complete wetting. (author)

  16. Influence of compost amendments on the diversity of alkane degrading bacteria in hydrocarbon contaminated soils

    Directory of Open Access Journals (Sweden)

    Michael eSchloter

    2014-03-01

    Full Text Available Alkane degrading microorganisms play an important role for bioremediation of petrogenic contaminated environments. In this study, we investigated the effects of compost addition on the diversity of alkane monooxygenase gene (alkB harboring bacteria in oil-contaminated soil originated from an industrial zone in Celje, Slovenia, to improve our understanding about the bacterial community involved in alkane degradation and the effects of amendments. Soil without any amendments (control soil and soil amended with compost of different maturation stages, i 1 year and ii 2 weeks, were incubated under controlled conditions in a microcosm experiment and sampled after 0, 6, 12 and 36 weeks of incubation. By using quantitative real-time PCR higher number of alkB genes could be detected in soil samples with compost compared to the control soil after 6, 12 and 36 weeks mainly if the less maturated compost was added. To get an insight into the composition of the alkB harboring microbial communities, we performed next generation sequencing of alkB gene fragment amplicons. Richness and diversity of alkB gene harboring prokaryotes was higher in soil mixed with compost compared to control soil after 6, 12 and 36 weeks again with stronger effects of the less maturated compost. Comparison of communities detected in different samples and time points based on principle component analysis revealed that the addition of compost in general stimulated the abundance of alkB harboring Actinobacteria during the experiment independent from the maturation stage of the compost compared to the control soils. In addition alkB harboring proteobacteria like Shewanella or Hydrocarboniphaga as well as proteobacteria of the genus Agrobacterium responded positively to the addition of compost to soil The amendment of the less maturated compost resulted in addition in a large increase of alkB harboring bacteria of the Cytophaga group (Microscilla mainly at the early sampling

  17. Ozone-driven photochemical formation of carboxylic acid groups from alkane groups

    Directory of Open Access Journals (Sweden)

    S. Liu

    2011-03-01

    Full Text Available Carboxylic acids are ubiquitous in atmospheric particles, and they play an important role in the physical and chemical properties of aerosol particles. During measurements in coastal California in the summer of 2009, carboxylic acid functional groups were highly associated with trajectories from an industrial region with high organic mass (OM, likely from fossil fuel combustion emissions. The concentration of carboxylic acid groups peaked during daytime, suggesting a photochemical secondary formation mechanism. This daytime increase in concentration was tightly correlated with O3 mixing ratio, indicating O3 was the likely driver in acid formation. Based on the diurnal cycles of carboxylic acid and alkane groups, the covariation of carboxylic acid groups with O3, and the composition of the Combustion factor resulted from the factor analyses, gas-phase alkane oxidation by OH radicals to form dihyfrofuran followed by further oxidation of dihydrofuran by O3 is the likely acid formation mechanism. Using the multi-day average of the daytime increase of carboxylic acid group concentrations and m/z 44-based Aged Combustion factor, we estimated the lower-bound contributions of secondary organic aerosol (SOA formed in 12-h daytime of processing in a single day to be 30% of the carboxylic acid groups and 25–45% of the Combustion factor concentration. These unique ambient observations of photochemically-driven acid formation suggest that gas-phase alkanes might be important sources of SOA formation in this coastal region.

  18. Mass dependence of the activation enthalpy and entropy of unentangled linear alkane chains

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Cheol; Douglas, Jack F. [Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)

    2015-10-14

    The mass scaling of the self-diffusion coefficient D of polymers in the liquid state, D ∼ M{sup β}, is one of the most basic characteristics of these complex fluids. Although traditional theories such as the Rouse and reptation models of unentangled and entangled polymer melts, respectively, predict that β is constant, this exponent for alkanes has been estimated experimentally to vary from −1.8 to −2.7 upon cooling. Significantly, β changes with temperature T under conditions where the chains are not entangled and at temperatures far above the glass transition temperature T{sub g} where dynamic heterogeneity does not complicate the description of the liquid dynamics. Based on atomistic molecular dynamics simulations on unentangled linear alkanes in the melt, we find that the variation of β with T can be directly attributed to the dependence of the enthalpy ΔH{sub a} and entropy ΔS{sub a} of activation on the number of alkane backbone carbon atoms, n. In addition, we find a sharp change in the melt dynamics near a “critical” chain length, n ≈ 17. A close examination of this phenomenon indicates that a “buckling transition” from rod-like to coiled chain configurations occurs at this characteristic chain length and distinct entropy-enthalpy compensation relations, ΔS{sub a} ∝ ΔH{sub a}, hold on either side of this polymer conformational transition. We conclude that the activation free energy parameters exert a significant influence on the dynamics of polymer melts that is not anticipated by either the Rouse and reptation models. In addition to changes of ΔH{sub a} and ΔS{sub a} with M, we expect changes in these free energy parameters to be crucial for understanding the dynamics of polymer blends, nanocomposites, and confined polymers because of changes of the fluid free energy by interfacial interactions and geometrical confinement.

  19. Kinetic features and industrial prospects of the selective oxidative cracking of light alkanes

    Science.gov (United States)

    Arutyunov, V. S.; Savchenko, V. I.; Sedov, I. V.; Nikitin, A. V.; Magomedov, R. N.; Proshina, A. Yu

    2017-01-01

    The results of kinetic investigations of selective oxidative cracking of light alkanes are analyzed and integrated. This process attracts researchers' attention owing to possible opportunities for designing new industrial processes based on light hydrocarbon feed. Particular attention is paid to ethane for which comprehensive and adequate models of oxidative conversion suitable for detailed analysis of the process kinetics have already been developed. The prospects for the practical application of methane homologues present in natural and associated gases in the selective oxidative cracking are discussed. The bibliography includes 85 references.

  20. Viscosity and Liquid Density of Asymmetric n-Alkane Mixtures: Measurement and Modelling

    DEFF Research Database (Denmark)

    Queimada, António J.; Marrucho, Isabel M.; Coutinho, João A.P.

    2005-01-01

    Viscosity and liquid density Measurements were performed, at atmospheric pressure. in pure and mixed n-decane. n-eicosane, n-docosane, and n-tetracosane from 293.15 K (or above the melting point) up to 343.15 K. The viscosity was determined with a rolling ball viscometer and liquid densities with...... of state and a corresponding states model recently proposed for surface tension, viscosity, vapor pressure, and liquid densities of the series of n-alkanes. Advantages and shortcoming of these models are discussed....

  1. A QSPR STUDY OF NORMAL BOILING POINT OF ORGANIC COMPOUNDS (ALIPHATIC ALKANES USING MOLECULAR DESCRIPTORS

    Directory of Open Access Journals (Sweden)

    B. Souyei

    2013-12-01

    Full Text Available A quantitative structure–property relationship (QSPR study is carried out to develop correlations that relate the molecular structures of organic compounds (Aliphatic Alkanes to their normal boiling point (NBP and two correlations were proposed for constitutionals and connectivity indices Models. The correlations are simple in application with good accuracy, which provide an easy, direct and relatively accurate way to calculate NBP. Such calculation gives us a model that gives results in remarkable correlations with the descriptors of blokes constitutionals (CON, and connectivity indices (CI (R2 = 0.950, δ = 0.766 (R2 = 0.969, δ = 0.782 respectively.

  2. Reversible Interconversion between Alkanes, Alkenes, Alcohols and Ketones under Hydrothermal Conditions

    Science.gov (United States)

    Shipp, J.; Hartnett, H. E.; Gould, I. R.; Shock, E.; Williams, L. B.

    2011-12-01

    Many transformation reactions involving hydrocarbons that occur in deep sedimentary systems and determine petroleum compositions occur in the presence of H2O. Hydrothermal transformations of organic material are thought to provide carbon sources for microbes in deep ocean sediments. Hydrothermal conditions may also mimic the conditions where life developed on an early Earth. Nevertheless, much remains to be learned about the mechanisms of hydrothermal organic reactions, including ways in which various reactions are interrelated and how reactions compete with each other. It can be argued that metastable equilibrium states develop over geological timescales and at geochemically relevant temperatures, suggesting that reactions occur under thermodynamic rather than kinetic control. The extent to which reactions are reversible, and how product distributions are determined, are primary tests of the metastable equilibrium model. Seewald (2001, GCA 65, 1641-1664) showed that under hydrothermal conditions and in the presence of a redox buffer, simple alkanes and alkenes undergo oxidation, reduction, and hydration reactions. He proposed a reaction scheme where alkanes interconvert with alkenes, followed by stepwise hydration of alkenes to alcohols, oxidation to ketones, and finally conversion to carboxylic acids, which can undergo decarboxylation. Here we describe experiments that further develop the scope of these functional group interconversions, determine relative reaction kinetics, and provide insight into competing reactions. Hydrothermal experiments were performed at 300°C and 100 MPa in gold capsules for 12 to 144 hours. The reactant structures were based on cyclohexane with one and two methyl groups that served as regio- and stereochemical markers for the reactions. Starting with the alkanes, the observed products include the corresponding alkenes, alcohols, ketones and enones, in support of the Seewald reaction scheme. Our experiments add a branch to this scheme

  3. Study of Some Alkanes Thermodynamic Parameters Using New Liquid Crystals Containing Sulfur as Stationary Phases

    Directory of Open Access Journals (Sweden)

    Mebrouk Djedid

    2015-06-01

    Full Text Available Most of the synthesized compounds which have liquid crystalline character in their composition comprise aromatic molecules. Furthermore there are few jobs that replace this type of molecules by inhomogeneous molecules that have LC character. We will replace the aromatic rings by units of 1,3,4-oxadiazole and study the effects of these new components of the transition temperatures and the Thermodynamic characteristics of n- alkanes in these two LC's phases. have been investigated by inverse gas chromatography. The transition temperatures obtained by GC are in good agreement with those found by DSC. The results are interpreted in terms of parameters “b” and related thermodynamic quantities

  4. CPI values of terrestrial higher plant-derived long-chain n-alkanes: a potential paleoclimatic proxy

    Institute of Scientific and Technical Information of China (English)

    Zhiguo RAO; Zhaoyu ZHU; Suping WANG; Guodong JIA; Mingrui QIANG; Yi WU

    2009-01-01

    Carbon Preference Index (CPI values) of higher plant-derived long-chain n-alkanes extracted from 62 surface soil samples in eastern China exhibited a specific pattern of variations, namely gradual increase with the increasing latitudes. Such regular variations existed in both forest soil and grassland soil. Our data implied that CPI values of higher plant-derived long-chain n-alkanes had a certain connection with climatic conditions, and such a connection was not influenced by vegetation types. Together with previous data from marine sediments, loess/ paleosol sequences, tertiary red clay and modern plants, our observation made us conclude that CPI values of higher plant-derived long-chain n-alkanes may be used as an excellent proxy for paleoclimatic studies.

  5. The true structural periodicities and superspace group descriptions of the prototypical incommensurate composite materials: Alkane/urea inclusion compounds

    Science.gov (United States)

    Couzi, Michel; Guillaume, François; Harris, Kenneth D. M.; Palmer, Benjamin A.; Christensen, Kirsten; Collins, Stephen P.

    2016-12-01

    The prototypical family of incommensurate composite materials are the n-alkane/urea inclusion compounds, in which n-alkane guest molecules are arranged in a periodic manner along one-dimensional tunnels in a urea host structure, with an incommensurate relationship between the periodicities of the host and guest substructures along the tunnel. We develop interpretations of the structural periodicities, superspace group descriptions and symmetry properties of the low-temperature phases of n-alkane/urea inclusion compounds, based in part on a high-resolution synchrotron single-crystal X-ray diffraction study of n-nonadecane/urea. Specifically, we prove that, on passing from phase I to phase II, the C-centering of the orthohexagonal unit cell is lost for both the host and guest substructures, and that the symmetries of all phases I, II and III are described completely by (3 + 1)-dimensional superspace groups.

  6. Upgrading light hydrocarbons via tandem catalysis: a dual homogeneous Ta/Ir system for alkane/alkene coupling.

    Science.gov (United States)

    Leitch, David C; Lam, Yan Choi; Labinger, Jay A; Bercaw, John E

    2013-07-17

    Light alkanes and alkenes are abundant but are underutilized as energy carriers because of their high volatility and low energy density. A tandem catalytic approach for the coupling of alkanes and alkenes has been developed in order to upgrade these light hydrocarbons into heavier fuel molecules. This process involves alkane dehydrogenation by a pincer-ligated iridium complex and alkene dimerization by a Cp*TaCl2(alkene) catalyst. These two homogeneous catalysts operate with up to 60/30 cooperative turnovers (Ir/Ta) in the dimerization of 1-hexene/n-heptane, giving C13/C14 products in 40% yield. This dual system can also effect the catalytic dimerization of n-heptane (neohexene as the H2 acceptor) with cooperative turnover numbers of 22/3 (Ir/Ta).

  7. High-resolution NMR spectra of n-alkanes penetrating into carbon fibers and of protons in carbon fibers.

    Science.gov (United States)

    Yamazaki, Yuya; Kobayashi, Nobuaki; Nikki, Kunio; Kuwahara, Daisuke

    2008-08-01

    We present a simple NMR method for microscopically exploring the local environment in carbon fibers. The method utilizes n-alkanes as probe molecules, where the n-alkanes penetrate carbon fibers of interest. The high-resolution (1)H NMR spectra for a mixture of a carbon fiber and n-alkanes acquired by this method show a shift of the resonance line, which is due to the local structure of the fiber. The utility of this method is discussed on the basis of the (1)H NMR spectra obtained. In addition, the (1)H distribution and the local motion in the structure of the carbon fiber are revealed in view of the (1)H NMR spectra.

  8. CF3(+) and CF2H(+): new reagents for n-alkane determination in chemical ionisation reaction mass spectrometry.

    Science.gov (United States)

    Blake, Robert S; Ouheda, Saleh A; Evans, Corey J; Monks, Paul S

    2016-11-28

    Alkanes provide a particular analytical challenge to commonly used chemical ionisation methods such as proton-transfer from water owing to their basicity. It is demonstrated that the fluorocarbon ions CF3(+) and CF2H(+), generated from CF4, as reagents provide an effective means of detecting light n-alkanes in the range C2-C6 using direct chemical ionisation mass spectrometry. The present work assesses the applicability of the reagents in Chemical Ionisation Mass Spectrometric (CI-TOF-MS) environments with factors such as high moisture content, operating pressures of 1-10 Torr, accelerating electric fields (E/N) and long-lived intermediate complex formation. Of the commonly used chemical ionisation reagents, H3O(+) and NO(+) only react with hexane and higher while O2(+) reacts with all the target samples, but creates significant fragmentation. By contrast, CF3(+) and CF2H(+) acting together were found to produce little or no fragmentation. In dry conditions with E/N = 100 Td or higher the relative intensity of CF2H(+) to CF3(+) was mostly less than 1% but always less than 3%, making CF3(+) the main reagent ion. Using O2(+) in a parallel series of experiments, a substantially greater degree of fragmentation was observed. The detection sensitivities of the alkanes with CF3(+) and CF2H(+), while relatively low, were found to be better than those observed with O2(+). Experiments using alkane mixtures in the ppm range have shown the ionisation technique based on CF3(+) and CF2H(+) to be particularly useful for measurements of alkane/air mixtures found in polluted environments. As a demonstration of the technique's effectiveness in complex mixtures, the detection of n-alkanes in a smoker's breath is demonstrated.

  9. The Use of a Combination of alkB Primers to Better Characterize the Distribution of Alkane-Degrading Bacteria.

    Directory of Open Access Journals (Sweden)

    Diogo Jurelevicius

    Full Text Available The alkane monooxygenase AlkB, which is encoded by the alkB gene, is a key enzyme involved in bacterial alkane degradation. To study the alkB gene within bacterial communities, researchers need to be aware of the variations in alkB nucleotide sequences; a failure to consider the sequence variations results in the low representation of the diversity and richness of alkane-degrading bacteria. To minimize this shortcoming, the use of a combination of three alkB-targeting primers to enhance the detection of the alkB gene in previously isolated alkane-degrading bacteria was proposed. Using this approach, alkB-related PCR products were detected in 79% of the strains tested. Furthermore, the chosen set of primers was used to study alkB richness and diversity in different soils sampled in Carmópolis, Brazil and King George Island, Antarctica. The DNA extracted from the different soils was PCR amplified with each set of alkB-targeting primers, and clone libraries were constructed, sequenced and analyzed. A total of 255 alkB phylotypes were detected. Venn diagram analyses revealed that only low numbers of alkB phylotypes were shared among the different libraries derived from each primer pair. Therefore, the combination of three alkB-targeting primers enhanced the richness of alkB phylotypes detected in the different soils by 45% to 139%, when compared to the use of a single alkB-targeting primer. In addition, a dendrogram analysis and beta diversity comparison of the alkB composition showed that each of the sampling sites studied had a particular set of alkane-degrading bacteria. The use of a combination of alkB primers was an efficient strategy for enhancing the detection of the alkB gene in cultivable bacteria and for better characterizing the distribution of alkane-degrading bacteria in different soil environments.

  10. The Use of a Combination of alkB Primers to Better Characterize the Distribution of Alkane-Degrading Bacteria

    Science.gov (United States)

    Jurelevicius, Diogo; Alvarez, Vanessa Marques; Peixoto, Raquel; Rosado, Alexandre S.; Seldin, Lucy

    2013-01-01

    The alkane monooxygenase AlkB, which is encoded by the alkB gene, is a key enzyme involved in bacterial alkane degradation. To study the alkB gene within bacterial communities, researchers need to be aware of the variations in alkB nucleotide sequences; a failure to consider the sequence variations results in the low representation of the diversity and richness of alkane-degrading bacteria. To minimize this shortcoming, the use of a combination of three alkB-targeting primers to enhance the detection of the alkB gene in previously isolated alkane-degrading bacteria was proposed. Using this approach, alkB-related PCR products were detected in 79% of the strains tested. Furthermore, the chosen set of primers was used to study alkB richness and diversity in different soils sampled in Carmópolis, Brazil and King George Island, Antarctica. The DNA extracted from the different soils was PCR amplified with each set of alkB-targeting primers, and clone libraries were constructed, sequenced and analyzed. A total of 255 alkB phylotypes were detected. Venn diagram analyses revealed that only low numbers of alkB phylotypes were shared among the different libraries derived from each primer pair. Therefore, the combination of three alkB-targeting primers enhanced the richness of alkB phylotypes detected in the different soils by 45% to 139%, when compared to the use of a single alkB-targeting primer. In addition, a dendrogram analysis and beta diversity comparison of the alkB composition showed that each of the sampling sites studied had a particular set of alkane-degrading bacteria. The use of a combination of alkB primers was an efficient strategy for enhancing the detection of the alkB gene in cultivable bacteria and for better characterizing the distribution of alkane-degrading bacteria in different soil environments. PMID:23825163

  11. RNAi silencing of a cytochrome P450 monooxygenase disrupts the ability of a filamentous fungus, Graphium sp. to grow on short-chain gaseous alkanes and ethers

    Science.gov (United States)

    Graphium sp. (ATCC 58400), a filamentous fungus, is one of the few eukaryotes that grows on short-chain alkanes and ethers. In this study, we investigated the genetic underpinnings that enable this fungus to catalyze the first step in the alkane and ether oxidation pathway. A gene, CYP52L1, was iden...

  12. Determination of the n-alkane profile of epicuticular wax extracted from mature leaves of Cestrum nocturnum (Solanaceae: Solanales).

    Science.gov (United States)

    Chowdhury, Nandita; Ghosh, Anupam; Bhattacharjee, Indranil; Laskar, Subrata; Chandra, Goutam

    2010-09-01

    An n-hexane extract of fresh, mature leaves of Cestrum nocturnum (Solanales: Solanaceae) containing thin layer epicuticular waxes was analysed by thin-layer chromatography, infrared and gas liquid chromatography using standard hydrocarbons. Seventeen long chain alkanes (n-C(18) to n-C(34)) were identified and quantified. Hentriacontane (n-C(31)) was established as the major n-alkane, while nonadecane (n-C(19)) was the least abundant component of the extracted wax fraction. The carbon preference index calculated for the sample was 1.30, showing an odd to even carbon number predominance.

  13. Assessment of soil n-alkane δD and branched tetraether membrane lipid distributions as tools for paleoelevation reconstruction

    Directory of Open Access Journals (Sweden)

    J. S. Sinninghe Damsté

    2009-12-01

    Full Text Available δ18O values of pedogenic minerals forming from soil water are commonly used to reconstruct paleoelevation. To circumvent some of the disadvantages of this method, soil n-alkane δD values were recently proposed as a new tool to reconstruct elevation changes, after showing that soil n-alkane δD values track the altitude effect on precipitation δD variations (r2=0.73 along Mt. Gongga, China. To verify the suitability of soil n-alkane δD values as a paleoelevation proxy we measured the δD of soil n-alkanes along Mt. Kilimanjaro (Tanzania. At midslope, soil n-alkane δD values are possibly influenced by the present precipitation belt, causing D-depletion in precipitation, and hence in the soil n-alkanes. Consequently, soil n-alkane δD values do not linearly relate with altitude (r2=0.03, suggesting that, in this case, they can not serve as an unambiguous proxy to infer past elevation changes. In contrast, it was recently shown that the MBT/CBT temperature proxy, which is based on the distribution of branched glycerol dialkyl glycerol tetraether (GDGT membrane lipids, is linearly related with MAT, and thus altitude (r2=0.77, at Mt. Kilimanjaro. This suggests that this proxy may be more suitable for paleoelevation reconstruction for this region. However, application of the MBT/CBT proxy on the altitude gradient along Mt. Gongga showed that, although the MBT/CBT-derived temperature lapse rate (−5.9°C/1000 m resembles the measured temperature lapse rate (−6.0°C/1000 m, there is a relatively large degree of scatter (r2=0.55. Our results thus show that both proxies can be subject to relatively large uncertainties in their assessment of past elevation changes, but that a combination of the soil n-alkane δD and MBT/CBT proxies can likely result in a more reliable assessment of paleoelevation.

  14. Predictive Local Composition Models for Solid/Liquid Equilibrium in n-Alkane Systems: Wilson Equation for Multicomponent Systems

    DEFF Research Database (Denmark)

    Coutinho, João A.P.; Stenby, Erling Halfdan

    1996-01-01

    The predictive local composition model is applied to multicomponent hydrocarbon systems with long-chain n-alkanes as solutes. The results show that it can successfully be extended to highorder systems and accurately predict the solid appearance temperature, also known as cloud point, in solutions...... of known composition using only binary information. The model can describe the experimentally well-known capacity of heavy alkanes to act as cloud-point depressants and explains it in terms of the nonideality of the solid solutions formed. There are good indications that no significant error is introduced...

  15. Molecular dynamics insight to phase transition in n-alkanes with carbon nanofillers

    Directory of Open Access Journals (Sweden)

    Monisha Rastogi

    2015-05-01

    Full Text Available The present work aims to investigate the phase transition, dispersion and diffusion behavior of nanocomposites of carbon nanotube (CNT and straight chain alkanes. These materials are potential candidates for organic phase change materials(PCMs and have attracted flurry of research recently. Accurate experimental evaluation of the mass, thermal and transport properties of such composites is both difficult as well as economically taxing. Additionally it is crucial to understand the factors that results in modification or enhancement of their characteristic at atomic or molecular level. Classical molecular dynamics approach has been extended to elucidate the same. Bulk atomistic models have been generated and subjected to rigorous multistage equilibration. To reaffirm the approach, both canonical and constant-temperature, constant- pressure ensembles were employed to simulate the models under consideration. Explicit determination of kinetic, potential, non-bond and total energy assisted in understanding the enhanced thermal and transport property of the nanocomposites from molecular point of view. Crucial parameters including mean square displacement and simulated self diffusion coefficient precisely define the balance of the thermodynamic and hydrodynamic interactions. Radial distribution function also reflected the density variation, strength and mobility of the nanocomposites. It is expected that CNT functionalization could improve the dispersion within n-alkane matrix. This would further ameliorate the mass and thermal properties of the composite. Additionally, the determined density was in good agreement with experimental data. Thus, molecular dynamics can be utilized as a high throughput technique for theoretical investigation of nanocomposites PCMs.

  16. Ignition of alkane-rich FACE gasoline fuels and their surrogate mixtures

    KAUST Repository

    Sarathy, Mani

    2015-01-01

    Petroleum derived gasoline is the most used transportation fuel for light-duty vehicles. In order to better understand gasoline combustion, this study investigated the ignition propensity of two alkane-rich FACE (Fuels for Advanced Combustion Engines) gasoline test fuels and their corresponding PRF (primary reference fuel) blend in fundamental combustion experiments. Shock tube ignition delay times were measured in two separate facilities at pressures of 10, 20, and 40 bar, temperatures from 715 to 1500 K, and two equivalence ratios. Rapid compression machine ignition delay times were measured for fuel/air mixtures at pressures of 20 and 40 bar, temperatures from 632 to 745 K, and two equivalence ratios. Detailed hydrocarbon analysis was also performed on the FACE gasoline fuels, and the results were used to formulate multi-component gasoline surrogate mixtures. Detailed chemical kinetic modeling results are presented herein to provide insights into the relevance of utilizing PRF and multi-component surrogate mixtures to reproduce the ignition behavior of the alkane-rich FACE gasoline fuels. The two FACE gasoline fuels and their corresponding PRF mixture displayed similar ignition behavior at intermediate and high temperatures, but differences were observed at low temperatures. These trends were mimicked by corresponding surrogate mixture models, except for the amount of heat release in the first stage of a two-stage ignition events, when observed. © 2014 The Combustion Institute.

  17. The structure of n-alkane binary mixtures adsorbed on graphite

    Energy Technology Data Exchange (ETDEWEB)

    Espeau, Philippe [Laboratoire de Chimie Physique et Minerale, Faculte de Pharmacie, Universite Rene Descartes-Paris V, F-75006 Paris (France)]. E-mail: philippe.espeau@univ-paris5.fr; White, John W. [Research School of Chemistry, Australian National University, Canberra, ACT 0200 (Australia); Papoular, Robert J. [Laboratoire Leon Brillouin, CEA-CEN Saclay, F-91191 Gif-sur-Yvette Cedex (France)

    2005-12-15

    The thermodynamics and structure of the surface adsorbed phase in binary C15-C16 and C15-C17 n-alkane mixtures confined in graphite pores have been studied by differential scanning calorimetry and small-angle X-ray scattering. The previously observed selective adsorption of the longer alkane for chain length differences greater than five carbon atoms is verified but reduced for chain length differences less than or equal to two. With a difference in chain length of one carbon atom, Vegard's law is followed for the melting points of the adsorbed mixture and the (0 2) d-spacing is a continuous function of the mole fraction x. With a two-carbon atom difference, samples aged for 1 week have a lamellar structure for which the entities A{sub 1-x}B {sub x} try to be commensurate with the substrate. The same samples aged for 1 month show a continuous parabolic x-dependence for both the melting points and the d-spacings. An explanation in terms of selective probability of adsorption is proposed based on crystallographic considerations.

  18. Branched aliphatic alkanes of shell bar section in Qarhan Lake, Qaidam Basin and their paleoclimate significance

    Institute of Scientific and Technical Information of China (English)

    ZHANG HuCai; CHANG FengQin; LI Bin; LEI GuoLiang; CHEN Yue; ZHANG WenXiang; NIU Jie; FAN HongFang; YANG MingSheng

    2007-01-01

    Biomarkers of paleolake deposits from Qarhan Salt Lake in Qaidam Basin, northwest China were systematically analyzed and the A-C series compounds of branched aliphatic alkanes with quaternary substituted carbon atom (BAQCs) were identified. The homologous distinguished three series, A-C,were identified as 5,5-diethylalkanes, 6,6-diethylalkanes and 5-butyl, 5-ethylalkanes series, and their relative abundance was A > B > C. Series A and C were characterized by odd carbon numbers, whereas series B was characterized by even carbon numbers. The high values of series A corresponded with the high values of series B and C. Therefore, it can be concluded that series A, B and C possess a similar biological origin. The abundance of series A was relatively Iow in the lower part of the section compared with that in the upper part, implying that these series originated from bacteria and/or algae more prevalent in fresh-mesohaline water, and such kinds of bacteria and/or algae are most likely to be thermophilous species. The A25/nC25 ratio differences in the section show that such branched aliphatic alkanes can be treated as one kind of environmental change proxy for paleolake evolution and may provide important information for the climate reconstruction of the Late Pleistocene.

  19. From Alkanes to Carboxylic Acids: Terminal Oxygenation by a Fungal Peroxygenase.

    Science.gov (United States)

    Olmedo, Andrés; Aranda, Carmen; Del Río, José C; Kiebist, Jan; Scheibner, Katrin; Martínez, Angel T; Gutiérrez, Ana

    2016-09-26

    A new heme-thiolate peroxidase catalyzes the hydroxylation of n-alkanes at the terminal position-a challenging reaction in organic chemistry-with H2 O2 as the only cosubstrate. Besides the primary product, 1-dodecanol, the conversion of dodecane yielded dodecanoic, 12-hydroxydodecanoic, and 1,12-dodecanedioic acids, as identified by GC-MS. Dodecanal could be detected only in trace amounts, and 1,12-dodecanediol was not observed, thus suggesting that dodecanoic acid is the branch point between mono- and diterminal hydroxylation. Simultaneously, oxygenation was observed at other hydrocarbon chain positions (preferentially C2 and C11). Similar results were observed in reactions of tetradecane. The pattern of products formed, together with data on the incorporation of (18) O from the cosubstrate H2 (18) O2 , demonstrate that the enzyme acts as a peroxygenase that is able to catalyze a cascade of mono- and diterminal oxidation reactions of long-chain n-alkanes to give carboxylic acids.

  20. An Alkane-Soluble Dendrimer as Electron-Transport Layer in Polymer Light-Emitting Diodes.

    Science.gov (United States)

    Zhong, Zhiming; Zhao, Sen; Pei, Jian; Wang, Jian; Ying, Lei; Peng, Junbiao; Cao, Yong

    2016-08-10

    Polymer light-emitting diodes (PLEDs) have attracted broad interest due to their solution-processable properties. It is well-known that to achieve better performance, organic light-emitting diodes require multilayer device structures. However, it is difficult to realize multilayer device structures by solution processing for PLEDs. Because most semiconducting polymers have similar solubility in common organic solvents, such as toluene, xylene, chloroform, and chlorobenzene, the deposition of multilayers can cause layers to mix together and damage each layer. Herein, a novel semiorthogonal solubility relationship was developed and demonstrated. For the first time, an alkane-soluble dendrimer is utilized as the electron-transport layer (ETL) in PLEDs via a solution-based process. With the dendrimer ETL, the external quantum efficiency increases more than threefold. This improvement in the device performance is attributed to better exciton confinement, improved exciton energy transfer, and better charge carrier balance. The semiorthogonal solubility provided by alkane offers another process dimension in PLEDs. By combining them with water/alcohol-soluble polyelectrolytes, more exquisite multilayer devices can be fabricated to achieve high device performance, and new device structures can be designed and realized.

  1. Tetradentate Schiff base ligands and their complexes: synthesis, structural characterization, thermal, electrochemical and alkane oxidation.

    Science.gov (United States)

    Ceyhan, Gökhan; Köse, Muhammet; McKee, Vickie; Uruş, Serhan; Gölcü, Ayşegül; Tümer, Mehmet

    2012-09-01

    Three Schiff base ligands (H(2)L(1)-H(2)L(3)) with N(2)O(2) donor sites were synthesized by condensation of 1,5-diaminonapthalene with benzaldehyde derivatives. A series of Cu(II), Co(II), Ni(II), Mn(II) and Cr(III) complexes were prepared and characterized by spectroscopic and analytical methods. Thermal, electrochemical and alkane oxidation reactions of the ligands and their metal complexes were investigated. Extensive application of 1D ((1)H, (13)C NMR) and 2D (COSY, HETCOR, HMBC and TOSCY) NMR techniques were used to characterize the structures of the ligands and establish the (1)H and (13)C resonance assignments of the three ligands. Ligands H(2)L(1) and H(2)L(3) were obtained as single crystals from THF solution and characterized by X-ray diffraction. Both molecules are centrosymmetric and asymmetric unit contains one half of the molecule. Catalytic alkane oxidation reactions with the transition metal complexes investigated using cyclohexane and cyclooctane as substrates. The Cu(II) and Cr(III) complexes showed good catalytic activity in the oxidation of cyclohexane and cyclooctane to desired oxidized products. Electrochemical and thermal properties of the compounds were also investigated.

  2. Prediction of the Flash Point of Binary and Ternary Straight-Chain Alkane Mixtures

    Directory of Open Access Journals (Sweden)

    X. Li

    2014-01-01

    Full Text Available The flash point is an important physical property used to estimate the fire hazard of a flammable liquid. To avoid the occurrence of fire or explosion, many models are used to predict the flash point; however, these models are complex, and the calculation process is cumbersome. For pure flammable substances, the research for predicting the flash point is systematic and comprehensive. For multicomponent mixtures, especially a hydrocarbon mixture, the current research is insufficient to predict the flash point. In this study, a model was developed to predict the flash point of straight-chain alkane mixtures using a simple calculation process. The pressure, activity coefficient, and other associated physicochemical parameters are not required for the calculation in the proposed model. A series of flash points of binary and ternary mixtures of straight-chain alkanes were determined. The results of the model present consistent experimental results with an average absolute deviation for the binary mixtures of 0.7% or lower and an average absolute deviation for the ternary mixtures of 1.03% or lower.

  3. Chemical characterization of organosulfates in secondary organic aerosol derived from the photooxidation of alkanes

    Science.gov (United States)

    Riva, Matthieu; Da Silva Barbosa, Thais; Lin, Ying-Hsuan; Stone, Elizabeth A.; Gold, Avram; Surratt, Jason D.

    2016-09-01

    We report the formation of aliphatic organosulfates (OSs) in secondary organic aerosol (SOA) from the photooxidation of C10-C12 alkanes. The results complement those from our laboratories reporting the formation of OSs and sulfonates from gas-phase oxidation of polycyclic aromatic hydrocarbons (PAHs). Both studies strongly support the formation of OSs from the gas-phase oxidation of anthropogenic precursors, as hypothesized on the basis of recent field studies in which aromatic and aliphatic OSs were detected in fine aerosol collected from several major urban locations. In this study, dodecane, cyclodecane and decalin, considered to be important SOA precursors in urban areas, were photochemically oxidized in an outdoor smog chamber in the presence of either non-acidified or acidified ammonium sulfate seed aerosol. Effects of acidity and relative humidity on OS formation were examined. Aerosols collected from all experiments were characterized by ultra performance liquid chromatography coupled to electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-QTOFMS). Most of the OSs identified could be explained by formation of gaseous epoxide precursors with subsequent acid-catalyzed reactive uptake onto sulfate aerosol and/or heterogeneous reactions of hydroperoxides. The OSs identified here were also observed and quantified in fine urban aerosol samples collected in Lahore, Pakistan, and Pasadena, CA, USA. Several OSs identified from the photooxidation of decalin and cyclodecane are isobars of known monoterpene organosulfates, and thus care must be taken in the analysis of alkane-derived organosulfates in urban aerosol.

  4. Molecular dynamics insight to phase transition in n-alkanes with carbon nanofillers

    Energy Technology Data Exchange (ETDEWEB)

    Rastogi, Monisha [School of Engineering, Indian Institute of Technology Mandi, Himachal Pradesh 175 001 (India); Vaish, Rahul, E-mail: rahul@iitmandi.ac.in [School of Engineering, Indian Institute of Technology Mandi, Himachal Pradesh 175 001 (India); Materials Research Centre, Indian Institute of Science, Bangalore 560 012 (India)

    2015-05-15

    The present work aims to investigate the phase transition, dispersion and diffusion behavior of nanocomposites of carbon nanotube (CNT) and straight chain alkanes. These materials are potential candidates for organic phase change materials(PCMs) and have attracted flurry of research recently. Accurate experimental evaluation of the mass, thermal and transport properties of such composites is both difficult as well as economically taxing. Additionally it is crucial to understand the factors that results in modification or enhancement of their characteristic at atomic or molecular level. Classical molecular dynamics approach has been extended to elucidate the same. Bulk atomistic models have been generated and subjected to rigorous multistage equilibration. To reaffirm the approach, both canonical and constant-temperature, constant- pressure ensembles were employed to simulate the models under consideration. Explicit determination of kinetic, potential, non-bond and total energy assisted in understanding the enhanced thermal and transport property of the nanocomposites from molecular point of view. Crucial parameters including mean square displacement and simulated self diffusion coefficient precisely define the balance of the thermodynamic and hydrodynamic interactions. Radial distribution function also reflected the density variation, strength and mobility of the nanocomposites. It is expected that CNT functionalization could improve the dispersion within n-alkane matrix. This would further ameliorate the mass and thermal properties of the composite. Additionally, the determined density was in good agreement with experimental data. Thus, molecular dynamics can be utilized as a high throughput technique for theoretical investigation of nanocomposites PCMs.

  5. Influence of alkane chain length on adsorption on an α-alumina surface by MD simulations

    Energy Technology Data Exchange (ETDEWEB)

    Turgut, C. [Department of Science and Analysis of Materials (SAM), CRP-Gabriel Lippmann, L-4422 Belvaux (Luxembourg); Institut Jean Lamour (IJL) CNRS UMR 7198, Université de Lorraine, Faculté des Sciences et Technologies, BP 70239, F-54506 Vandoeuvre-les-Nancy Cedex (France); Pandiyan, S. [Department of Science and Analysis of Materials (SAM), CRP-Gabriel Lippmann, L-4422 Belvaux (Luxembourg); Mether, L. [Department of Physics, University of Helsinki, P.O. Box 43, FI-00014 (Finland); Belmahi, M. [Institut Jean Lamour (IJL) CNRS UMR 7198, Université de Lorraine, Faculté des Sciences et Technologies, BP 70239, F-54506 Vandoeuvre-les-Nancy Cedex (France); Nordlund, K. [Department of Physics, University of Helsinki, P.O. Box 43, FI-00014 (Finland); Philipp, P., E-mail: philipp@lippmann.lu [Department of Science and Analysis of Materials (SAM), CRP-Gabriel Lippmann, L-4422 Belvaux (Luxembourg)

    2015-06-01

    Plasma surface techniques provide both an efficient and ecological tool for the functionalization of surfaces. Hence, a proper understanding of the plasma–surface interactions of precursors and radicals during the deposition process is of great importance. Especially during the initial deposition process, the deposition of molecules and fragments is difficult to investigate by experimental techniques and import insights can be obtained by molecular dynamics simulations. In this work, the reactive force field developed by the group of Kieffer at the University of Michigan was used to study the adsorption of single linear alkane chains on an α-alumina surface. The chain length was changed from 6 backbone carbon atoms to 16 carbon atoms, the deposition energy from 0.01 to 10 eV and the incidence angle from 0° to 60° with respect to the surface normal. Results show that the adsorption depends a lot on the ratio of deposition energy to alkane chain length and the incidence angle. More grazing incidence reduces the adsorption probability and a low ratio of energy to chain length increases it.

  6. Thermodiffusion, molecular diffusion and Soret coefficients of aromatic+n-alkane binary mixtures

    Science.gov (United States)

    Larrañaga, Miren; Bou-Ali, M. Mounir; Lapeira, Estela; Lizarraga, Ion; Santamaría, Carlos

    2016-10-01

    In the present work, we have measured the thermodiffusion coefficient of 51 binary liquid mixtures at 25 oC. These mixtures correspond to the series of the aromatics toluene and 1-methylnaphthalene with n-alkanes nCi (i = 6, 8, 10, 12, and 14) at different mass fractions in the whole range. For that, we have used the thermogravitational technique. It is shown that the thermodiffusion coefficient is a linear function of the mass fraction in all the mixtures. Extrapolating the lines, we obtain the thermodiffusion coefficient in dilute solutions of n-alkanes for both toluene and 1-methylnaphthalene. These limiting values show a linear dependence with the inverse of the product of the molecular weights. In addition, we have measured the molecular diffusion coefficient of all the mixtures at 0.5 of mass fraction and at 25 oC, by the sliding symmetric tubes technique. It is observed that the product of this coefficient with the viscosity at the same concentrations takes a constant value for each of the series considered. Finally, we have also determined the Soret coefficient of the equimass mixtures by the combination of the measurements of thermodiffusion and molecular diffusion coefficients.

  7. Equivalent Alkane Carbon Number of Live Crude Oil: A Predictive Model Based on Thermodynamics

    Directory of Open Access Journals (Sweden)

    Creton Benoit

    2016-09-01

    Full Text Available We took advantage of recently published works and new experimental data to propose a model for the prediction of the Equivalent Alkane Carbon Number of live crude oil (EACNlo for EOR processes. The model necessitates the a priori knowledge of reservoir pressure and temperature conditions as well as the initial gas to oil ratio. Additionally, some required volumetric properties for hydrocarbons were predicted using an equation of state. The model has been validated both on our own experimental data and data from the literature. These various case studies cover broad ranges of conditions in terms of API gravity index, gas to oil ratio, reservoir pressure and temperature, and composition of representative gas. The predicted EACNlo values reasonably agree with experimental EACN values, i.e. determined by comparison with salinity scans for a series of n-alkanes from nC8 to nC18. The model has been used to generate high pressure high temperature data, showing competing effects of the gas to oil ratio, pressure and temperature. The proposed model allows to strongly narrow down the spectrum of possibilities in terms of EACNlo values, and thus a more rational use of equipments.

  8. Particulate n-alkanes and fatty acids in the ChangJiang river system

    Institute of Scientific and Technical Information of China (English)

    WU Ying; ZHANG Jing; LIU Sumei; ZHANG Zaifeng; CHEN Hongtao; XIONG Hui

    2007-01-01

    Particulate samples were collected from the Changjiang river system during a flood period, in May 1997, and POC, stable isotope and lipids associated with particles were examined. Results showed the decrease (0.84% ~ 1.88%) of organic carbon content from the upper reaches to the estuary.δ13C values of particulate organic carbon was in the range of -24.9×10-3 to -26.6×10-3, which were close to the isotopic signature of continental C3 vegetation. Total particulate n-alkanes concentrations varied from 1.4 to 10.1μg/dm3,or from 23.7 to 107μg/g of total suspended matter. Fatty acids were present in all the samples, from 1.4 to 5.4μg/dm3, with saturated and unsaturated straight-chain and branched compounds in the carbon number range from C12 to C30. Both δ13C and the ratio of carbon content to nitrogen content indicate the predominance of terrestrial inputs (soil organic matter) among the particles. The biomarker approach has been used to identify the relative portion of terrigenous and autochthonous fraction in the particulate samples. The distribution of fatty acids suggests a striking phytoplanktonic and microbial signal in most particle samples. The terrestrial alkanes are used to estimate the contribution of terrestrial inputs along the mainstream.

  9. Possible room temperature superconductivity in conductors obtained by bringing alkanes into contact with a graphite surface

    Directory of Open Access Journals (Sweden)

    Yasushi Kawashima

    2013-05-01

    Full Text Available Electrical resistances of conductors obtained by bringing alkanes into contact with a graphite surface have been investigated at room temperatures. Ring current in a ring-shaped container into which n-octane-soaked thin graphite flakes were compressed did not decay for 50 days at room temperature. After two HOPG plates were immersed into n-heptane and n-octane at room temperature, changes in resistances of the two samples were measured by four terminal technique. The measurement showed that the resistances of these samples decrease to less than the smallest resistance that can be measured with a high resolution digital voltmeter (0.1μV. The observation of persistent currents in the ring-shaped container suggests that the HOPG plates immersed in n-heptane and n-octane really entered zero-resistance state at room temperature. These results suggest that room temperature superconductor may be obtained by bringing alkanes into contact with a graphite surface.

  10. The anesthetic effect of alcohols and alkanes in caenorhabditis elegans (C. E. )

    Energy Technology Data Exchange (ETDEWEB)

    Anton, A.H.; Berk, A.I.; Nicholls, C.H. (Case Western Reserve Univ., Cleveland, OH (United States))

    1991-03-11

    The authors colleagues reported that the non-parasitic roundworm, C.E., was reversibly immobilized by volatile anesthetics, whose potencies were directly related to their lipid solubilities as in other animals. In further studies on this phenomenon, they tested a homologous series of organic solvents, to determine whether they also had a reversible anesthetic effect in C.E. as in other animals. Synchronized 3-1/2 day-old cultures of about 100 worms each were exposed to increasing concentrations of the alcohols (C{sub 1} - C{sub 14}) and alkanes (C{sub 5} -C{sub 10}) in 15 ml sealed bottles in a volume of 0.5 ml. The dose that reversibly immobilized 50% of the worms was determined and a straight line was plotted against the octanol/water partition coefficient (K) of each series. As with other animals, potency was directly related to the lipid solubility of these agents so that, for example, the ID{sub 50} for methanol was 1,000 mmol (K=0.12) whereas it was 0.17 mmol for heptanol (K=3,000). The alcohols were about 20 times more potent than the alkanes even though the latter were about 10 times more lipid soluble than the alcohols. In spite of these differences, the cut-off point was at C{sub 9} in the two series.

  11. Molecular simulations of intermediate and long alkanes adsorbed on graphite: tuning of non-bond interactions.

    Science.gov (United States)

    Firlej, Lucyna; Kuchta, Bogdan; Roth, Michael W; Wexler, Carlos

    2011-04-01

    The interplay between the torsional potential energy and the scaling of the 1-4 van der Waals and Coulomb interactions determines the stiffness of flexible molecules. In this paper we demonstrate for the first time that the precise value of the nonbond scaling factor (SF)--often a value assumed without justification--has a significant effect on the critical properties and mechanisms of systems undergoing a phase transition, and that, for accurate simulations, this scaling factor is highly dependent on the system under consideration. In particular, by analyzing the melting of n-alkanes (hexane C6, dodecane C12, tetracosane C24) on graphite, we show that the SF is not constant over varying alkane chain lengths when the structural correlated transformations are concerned. Instead, monotonic decrease of SF with the molecular length drives a cross-over between two distinct mechanisms for melting in such systems. In a broad sense we show that the choice for SF in any simulation containing adsorbed or correlated long molecules needs to be carefully considered.

  12. Can broader diffusion of value-based insurance design increase benefits from US health care without increasing costs? Evidence from a computer simulation model.

    Directory of Open Access Journals (Sweden)

    R Scott Braithwaite

    2010-02-01

    Full Text Available BACKGROUND: Evidence suggests that cost sharing (i.e.,copayments and deductibles decreases health expenditures but also reduces essential care. Value-based insurance design (VBID has been proposed to encourage essential care while controlling health expenditures. Our objective was to estimate the impact of broader diffusion of VBID on US health care benefits and costs. METHODS AND FINDINGS: We used a published computer simulation of costs and life expectancy gains from US health care to estimate the impact of broader diffusion of VBID. Two scenarios were analyzed: (1 applying VBID solely to pharmacy benefits and (2 applying VBID to both pharmacy benefits and other health care services (e.g., devices. We assumed that cost sharing would be eliminated for high-value services ($300,000 per life-year. All costs are provided in 2003 US dollars. Our simulation estimated that approximately 60% of health expenditures in the US are spent on low-value services, 20% are spent on intermediate-value services, and 20% are spent on high-value services. Correspondingly, the vast majority (80% of health expenditures would have cost sharing that is impacted by VBID. With prevailing patterns of cost sharing, health care conferred 4.70 life-years at a per-capita annual expenditure of US$5,688. Broader diffusion of VBID to pharmaceuticals increased the benefit conferred by health care by 0.03 to 0.05 additional life-years, without increasing costs and without increasing out-of-pocket payments. Broader diffusion of VBID to other health care services could increase the benefit conferred by health care by 0.24 to 0.44 additional life-years, also without increasing costs and without increasing overall out-of-pocket payments. Among those without health insurance, using cost saving from VBID to subsidize insurance coverage would increase the benefit conferred by health care by 1.21 life-years, a 31% increase. CONCLUSION: Broader diffusion of VBID may amplify benefits from

  13. Nucleation, growth and habit modification of n-alkanes and homologous mixtures in the absence and presence of flow improving additives

    CERN Document Server

    Taggart, A M

    1996-01-01

    A detailed study has been performed on the nucleation, growth and habit modification of n-alkanes and homologous mixtures in the absence and presence of flow improving additives in an attempt to gain a clearer appreciation of the interaction mechanisms behind wax / additive crystallisation. Kinetic and structural assessment of melt phase n-alkanes illustrate the different crystallographic forms present within the homologous series. Studies demonstrate the alternating behaviour of the even and odd numbered homologues which converges as a function of increasing molecular weight. Greater crystal lattice stabilities were found for those n-alkanes which have an even carbon number and which crystallise into the triclinic crystal structure. Solid state phase behaviour of the n-alkanes was found to vary depending on the number and parity of n. Nucleation kinetic studies of n-alkanes and homologous mixtures from model diesel fuel solvents (dodecane, m-xylene, decalin, pristane and a dewaxed fuel) are assessed using tu...

  14. Sensitive detection of n-alkanes using a mixed ionization mode proton-transfer-reaction mass spectrometer

    Science.gov (United States)

    Amador-Muñoz, Omar; Misztal, Pawel K.; Weber, Robin; Worton, David R.; Zhang, Haofei; Drozd, Greg; Goldstein, Allen H.

    2016-11-01

    Proton-transfer-reaction mass spectrometry (PTR-MS) is a technique that is widely used to detect volatile organic compounds (VOCs) with proton affinities higher than water. However, n-alkanes generally have a lower proton affinity than water and therefore proton transfer (PT) by reaction with H3O+ is not an effective mechanism for their detection. In this study, we developed a method using a conventional PTR-MS to detect n-alkanes by optimizing ion source and drift tube conditions to vary the relative amounts of different primary ions (H3O+, O2+, NO+) in the reaction chamber (drift tube). There are very few studies on O2+ detection of alkanes and the mixed mode has never been proposed before. We determined the optimum conditions and the resulting reaction mechanisms, allowing detection of n-alkanes from n-pentane to n-tridecane. These compounds are mostly emitted by evaporative/combustion process from fossil fuel use. The charge transfer (CT) mechanism observed with O2+ was the main reaction channel for n-heptane and longer n-alkanes, while for n-pentane and n-hexane the main reaction channel was hydride abstraction (HA). Maximum sensitivities were obtained at low E / N ratios (83 Td), low water flow (2 sccm) and high O2+ / NO+ ratios (Uso = 180 V). Isotopic 13C contribution was taken into account by subtracting fractions of the preceding 12C ion signal based on the number of carbon atoms and the natural abundance of 13C (i.e., 5.6 % for n-pentane and 14.5 % for n-tridecane). After accounting for isotopic distributions, we found that PT cannot be observed for n-alkanes smaller than n-decane. Instead, protonated water clusters of n-alkanes (M ṡ H3O+) species were observed with higher abundance using lower O2+ and higher water cluster fractions. M ṡ H3O+ species are probably the source for the M + H+ species observed from n-decane to n-tridecane. Normalized sensitivities to O2+ or to the sum of O2++ NO+ were determined to be a good metric with which to

  15. Crystal Structure of a Putative Cytochrome P450 Alkane Hydroxylase (CYP153D17) from Sphingomonas sp. PAMC 26605 and Its Conformational Substrate Binding

    Science.gov (United States)

    Lee, Chang Woo; Yu, Sang-Cheol; Lee, Joo-Ho; Park, Sun-Ha; Park, Hyun; Oh, Tae-Jin; Lee, Jun Hyuck

    2016-01-01

    Enzymatic alkane hydroxylation reactions are useful for producing pharmaceutical and agricultural chemical intermediates from hydrocarbons. Several cytochrome P450 enzymes catalyze the regio- and stereo-specific hydroxylation of alkanes. We evaluated the substrate binding of a putative CYP alkane hydroxylase (CYP153D17) from the bacterium Sphingomonas sp. PAMC 26605. Substrate affinities to C10–C12 n-alkanes and C10–C14 fatty acids with Kd values varied from 0.42 to 0.59 μM. A longer alkane (C12) bound more strongly than a shorter alkane (C10), while shorter fatty acids (C10, capric acid; C12, lauric acid) bound more strongly than a longer fatty acid (C14, myristic acid). These data displayed a broad substrate specificity of CYP153D17, hence it was named as a putative CYP alkane hydroxylase. Moreover, the crystal structure of CYP153D17 was determined at 3.1 Å resolution. This is the first study to provide structural information for the CYP153D family. Structural analysis showed that a co-purified alkane-like compound bound near the active-site heme group. The alkane-like substrate is in the hydrophobic pocket containing Thr74, Met90, Ala175, Ile240, Leu241, Val244, Leu292, Met295, and Phe393. Comparison with other CYP structures suggested that conformational changes in the β1–β2, α3–α4, and α6–α7 connecting loop are important for incorporating the long hydrophobic alkane-like substrate. These results improve the understanding of the catalytic mechanism of CYP153D17 and provide valuable information for future protein engineering studies. PMID:27941697

  16. Graphic model for calculating the entropy of C11H24 alkanes with allowance for multiple non-valence interactions through three atoms along the chain of a molecule

    Science.gov (United States)

    Nilov, D. Yu.; Smolyakov, V. M.

    2016-08-01

    A fourteen-constant graphic scheme is proposed for evaluating the thermodynamic properties of branched paraffin hydrocarbons. Absolute entropy S f, 298 gas of 159 alkanes, of which 157 alkanes have yet to be studied experimentally, are calculated using 105 experimental data S f, 298 K, gas for alkanes CH4-C32H66.

  17. 云计算环境下的电子证据取证关键技术研究%Research of Key Technologies of Electronic Evidence Forensics Based on Cloud Computing Environment

    Institute of Scientific and Technical Information of China (English)

    吴绍兵

    2012-01-01

    Cloud computing is a method of calculation which provides users with the computing capacity, storage capacity and service capabilities,according to need and the final purpose is user-friendly and greatly reduces the user's hardware and software procurement costs. Cloud computing forensics is a new battlefield,in order to better combat cybercrime in the battlefield,you must come up with some novel methods of investigation. Static electronic evidence, dynamic web-based electronic evidence, the cloud environment of electronic forensics related concepts,key technologies, etc. Are reviewed and the key technologies of the electronic evidence collection model in cloud computing environments are discussed. That cloud computing mode of thinking is proposed. It points out the cloud forensics technology development trends.%云计算是能为用户提供按需分配的计算能力、存储能力及应用服务能力,方便用户使用,大大降低用户软硬件采购费用的一种计算方式.云计算取证是一个新的战场,为了在这一战场中更好地打击网络犯罪,必须研究出一些新奇的调查方法.从静态的电子证据、动态的网络电子取证到云计算环境下的电子取证的相关概念、关键技术等进行了综述,探讨了云计算环境下的电子取证模型关键技术,提出了云计算思维模式,并指出了云取证技术的发展趋势和展望.

  18. Cuticular and internal n-alkane composition of Lucilia sericata larvae, pupae, male and female imagines: application of HPLC-LLSD and GC/MS-SIM.

    Science.gov (United States)

    Gołębiowski, M; Paszkiewicz, M; Grubba, A; Gąsiewska, D; Boguś, M I; Włóka, E; Wieloch, W; Stepnowski, P

    2012-08-01

    The composition of cuticular and internal n-alkanes in Lucilia sericata larvae, pupae, and male and female imagines were studied. The cuticular and internal lipid extracts were separated by HPLC-LLSD, after which the hydrocarbon fraction was identified by GC/MS in selected ion monitoring (SIM) and total ion current (TIC) modes. The cuticular lipids of the larvae contained seven n-alkanes from C23 to C31. The major n-alkane in L. sericata larvae was C29 (42.1%). The total cuticular n-alkane content in the cuticular lipids was 31.46 μg g-1 of the insect body. The internal lipids of L. sericata larvae contained five n-alkanes ranged from C25 to C31. The most abundant compound was C27 (61.71 μg g-1 of the insect body). Eighteen n-alkanes from C14 to C31 were identified in the cuticular lipids of the pupae. The most abundant n-alkanes ranged from C25 to C31; those with odd-numbered carbon chains were particularly abundant, the major one being C29:0 (59.5%). Traces of eight cuticular n-alkanes were present. The internal lipids of L. sericata pupae contained five n-alkanes, ranging from C25 to C31. The cuticular lipids of female imagines contained 17 n-alkanes from C12 to C30. Among the cuticular n-alkanes of females, C27 (47.5%) was the most abundant compound. Four n-alkanes, with only odd-numbered carbon chains, were identified in the internal lipids of females. The lipids from both sexes of L. sericata had similar n-alkane profiles. The cuticular lipids of adult males contained 16 n-alkanes ranging from C13 to C31. C27 (47.9%) was the most abundant cuticular n-alkanes in males. The same n-alkanes only with odd-numbered carbon chains and in smaller quantities of C27 (0.1%) were also identified in the internal lipids of males. The highest amounts of total cuticular n-alkanes were detected in males and females of L. sericata (330.4 and 158.93 μg g-1 of the insect body, respectively). The quantities of total cuticular alcohols in larvae and pupae were smaller (31.46

  19. High-resolution ellipsometric study of an n-alkane film, dotriacontane, adsorbed on a SiO2 surface

    DEFF Research Database (Denmark)

    Volkmann, U.G.; Pino, M.; Altamirano, L.A.

    2002-01-01

    to the interface. At still higher coverages and at temperatures below the bulk melting point at T-b=341 K, solid bulk particles coexist on top of the "perpendicular film." For higher temperatures in the range T-bT-s, a uniformly thick fluid film wets to the parallel film phase. This structure of the alkane/SiO2...

  20. Comparison of quantification methods for the analysis of polychlorinated alkanes using electron capture negative ionisation mass spectrometry

    NARCIS (Netherlands)

    Rusina, T.; Korytar, P.; Boer, de J.

    2011-01-01

    Four quantification methods for short-chain chlorinated paraffins (SCCPs) or polychlorinated alkanes (PCAs) using gas chromatography electron capture negative ionisation low resolution mass spectrometry (GC-ECNI-LRMS) were investigated. The method based on visual comparison of congener group pattern

  1. Carbon isotope analysis of n-alkanes in dust from the lower atmosphere over the eastern Atlantic

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Schefuß, E.; Ratmeyer, V.; Stuut, J-B.W.; Jansen, J.H.F.

    2003-01-01

    Atmospheric dust samples collected along a transect off the West African coast have been investigated for their lipid content and compound-specific stable carbon isotope compositions. The saturated hydrocarbon fractions of the organic solvent extracts consist mainly of long-chain n-alkanes derived f

  2. Isolation of the alkane inducible cytochrome P450 (P450alk) gene from the yeast Candida tropicalis

    Science.gov (United States)

    The gene for the alkane-inducible cytochrome P450, P450alk, has been isolated from the yeast Candida tropicalis by immunoscreening a λgt11 library. Isolation of the gene has been identified on the basis of its inducibility and partial DNA sequence. Transcripts of this gene were i...

  3. Holocene vegetation cover in Qin'an area of western Chinese Loess Plateau revealed by n-alkane

    Institute of Scientific and Technical Information of China (English)

    ZHONG YanXia; CHEN FaHu; AN ChengBang; XIE ShuCheng; HUANG XianYu

    2007-01-01

    Previous studies have found that wetlands prevailed in western Chinese Loess Plateau and pine pollen could reach up to 80% in Qin'an area of the plateau during middle Holocene.It was then deduced that forest vegetation covered Qin'an area in a warm and wet climate during middle Holocene.The proxies of molecule biomarkers from two Holocene sections,a swamp-alluvial loess section and a typical loess-paleosol section are used to reconstruct regional vegetation history.It is found that the heavy-molecular-weight(HMW)homologues of the n-alkanes in all samples exhibit a pronounced odd-over-even predominance,maximizing at C31 and the abundance of the nC27-alkanes is the lowest in nC27,nC29,nC31,i.e.C27<C29<C31,a typical grass n-alkanes model.The results are the same as those of model surface soil samples under grass cover but different from both forest cover and modern pine leaves,which yield preferentially nC29-alkanes peak.It could be jnferred that the area was dominated by grass cover but not forest cover during whole Holocene epoch.The study shows that combining both molecule biomarkers and pollen analysis can avoid the disadvantage of pollen analysis in reconstruction of regional vegetation cover.

  4. Use of cuticular wax alkanes to estimate digestibility and intake of cows as pasture with a view to estimating efficiency.

    Science.gov (United States)

    Determination of feed efficiency requires estimates of intake and digestibility of the diet, but they are difficult to measure on pasture. The objective of this research was to determine if plants cuticular alkanes were suitable as markers to estimate intake and diet digestibility of grazing cows wi...

  5. Alkane production by the marine cyanobacterium Synechococcus sp. NKBG15041c possessing the α-olefin biosynthesis pathway.

    Science.gov (United States)

    Yoshino, Tomoko; Liang, Yue; Arai, Daichi; Maeda, Yoshiaki; Honda, Toru; Muto, Masaki; Kakunaka, Natsumi; Tanaka, Tsuyoshi

    2015-02-01

    The production of alkanes in a marine cyanobacterium possessing the α-olefin biosynthesis pathway was achieved by introducing an exogenous alkane biosynthesis pathway. Cyanobacterial hydrocarbons are synthesized via two separate pathways: the acyl-acyl carrier protein (ACP) reductase/aldehyde-deformylating oxygenase (AAR/ADO) pathway for the alkane biosynthesis and the α-olefin synthase (OLS) pathway for the α-olefin biosynthesis. Coexistence of these pathways has not yet been reported. In this study, the marine cyanobacterium Synechococcus sp. NKBG15041c was shown to produce α-olefins similar to those of Synechococcus sp. PCC7002 via the α-olefin biosynthesis pathway. The production of heptadecane in Synechococcus sp. NKBG15041c was achieved by expressing the AAR/ADO pathway genes from Synechococcus elongatus PCC 7942. The production yields of heptadecane in Synechococcus sp. NKBG15041c varied with the expression level of the aar and ado genes. The maximal yield of heptadecane was 4.2 ± 1.2 μg/g of dried cell weight in the transformant carrying a homologous promoter. Our results also suggested that the effective activation of ADO may be more important for the enhancement of alkane production by cyanobacteria.

  6. Isolation and characterization of alkane degrading bacteria from petroleum reservoir waste water in Iran (Kerman and Tehran provenances).

    Science.gov (United States)

    Hassanshahian, Mehdi; Ahmadinejad, Mohammad; Tebyanian, Hamid; Kariminik, Ashraf

    2013-08-15

    Petroleum products spill and leakage have become two major environmental challenges in Iran. Sampling was performed in the petroleum reservoir waste water of Tehran and Kerman Provinces of Iran. Alkane degrading bacteria were isolated by enrichment in a Bushnel-Hass medium, with hexadecane as sole source of carbon and energy. The isolated strains were identified by amplification of 16S rDNA gene and sequencing. Specific primers were used for identification of alkane hydroxylase gene. Fifteen alkane degrading bacteria were isolated and 8 strains were selected as powerful degradative bacteria. These 8 strains relate to Rhodococcus jostii, Stenotrophomonas maltophilia, Achromobacter piechaudii, Tsukamurella tyrosinosolvens, Pseudomonas fluorescens, Rhodococcus erythropolis, Stenotrophomonas maltophilia, Pseudomonas aeruginosa genera. The optimum concentration of hexadecane that allowed high growth was 2.5%. Gas chromatography results show that all strains can degrade approximately half of hexadecane in one week of incubation. All of the strains have alkane hydroxylase gene which are important for biodegradation. As a result, this study indicates that there is a high diversity of degradative bacteria in petroleum reservoir waste water in Iran.

  7. The influence of molecular structure and aerosol phase on the heterogeneous oxidation of normal and branched alkanes by OH.

    Science.gov (United States)

    Ruehl, Christopher R; Nah, Theodora; Isaacman, Gabriel; Worton, David R; Chan, Arthur W H; Kolesar, Katheryn R; Cappa, Christopher D; Goldstein, Allen H; Wilson, Kevin R

    2013-05-16

    Insights into the influence of molecular structure and thermodynamic phase on the chemical mechanisms of hydroxyl radical-initiated heterogeneous oxidation are obtained by identifying reaction products of submicrometer particles composed of either n-octacosane (C28H58, a linear alkane) or squalane (C30H62, a highly branched alkane) and OH. A common pattern is observed in the positional isomers of octacosanone and octacosanol, with functionalization enhanced toward the end of the molecule. This suggests that relatively large linear alkanes are structured in submicrometer particles such that their ends are oriented toward the surface. For squalane, positional isomers of first-generation ketones and alcohols also form in distinct patterns. Ketones are favored on carbons adjacent to tertiary carbons, while hydroxyl groups are primarily found on tertiary carbons but also tend to form toward the end of the molecule. Some first-generation products, viz., hydroxycarbonyls and diols, contain two oxygen atoms. These results suggest that alkoxy radicals are important intermediates and undergo both intramolecular (isomerization) and intermolecular (chain propagation) hydrogen abstraction reactions. Oxidation products with carbon number less than the parent alkane's are observed to a much greater extent for squalane than for n-octacosane oxidation and can be explained by the preferential cleavage of bonds involving tertiary carbons.

  8. Shock tube measurements of the rate constants for seven large alkanes+OH

    KAUST Repository

    Badra, Jihad

    2015-01-01

    Reaction rate constants for seven large alkanes + hydroxyl (OH) radicals were measured behind reflected shock waves using OH laser absorption. The alkanes, n-hexane, 2-methyl-pentane, 3-methyl-pentane, 2,2-dimethyl-butane, 2,3-dimethyl-butane, 2-methyl-heptane, and 4-methyl-heptane, were selected to investigate the rates of site-specific H-abstraction by OH at secondary and tertiary carbons. Hydroxyl radicals were monitored using narrow-line-width ring-dye laser absorption of the R1(5) transition of the OH spectrum near 306.7 nm. The high sensitivity of the diagnostic enabled the use of low reactant concentrations and pseudo-first-order kinetics. Rate constants were measured at temperatures ranging from 880 K to 1440 K and pressures near 1.5 atm. High-temperature measurements of the rate constants for OH + n-hexane and OH + 2,2-dimethyl-butane are in agreement with earlier studies, and the rate constants of the five other alkanes with OH, we believe, are the first direct measurements at combustion temperatures. Using these measurements and the site-specific H-abstraction measurements of Sivaramakrishnan and Michael (2009) [1,2], general expressions for three secondary and two tertiary abstraction rates were determined as follows (the subscripts indicate the number of carbon atoms bonded to the next-nearest-neighbor carbon): S20=1.58×10-11exp(-1550K/T)cm3molecule-1s-1(887-1327K)S30=2.37×10-11exp(-1850K/T)cm3molecule-1s-1(887-1327K)S21=4.5×10-12exp(-793.7K/T)cm3molecule-1s-1(833-1440K)T100=2.85×10-11exp(-1138.3K/T)cm3molecule-1s-1(878-1375K)T101=7.16×10-12exp(-993K/T)cm3molecule-1s-1(883-1362K) © 2014 The Combustion Institute.

  9. Nonequilibrium molecular dynamics simulation of the rheology of linear and branched alkanes

    Energy Technology Data Exchange (ETDEWEB)

    Cui, S.T.; Cummings, P.T.; Cochran, H.D.; Moore, J.D.; Gupta, S.A. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemical Engineering]|[Oak Ridge National Lab., TN (United States). Chemical Technology Div.

    1998-03-01

    Liquid alkanes in the molecular weight range of C{sub 20}-C{sub 40} are the main constituents of lubricant basestocks, and their rheological properties are therefore of great concern in industrial lubricant applications. Using massively parallel supercomputers and an efficient parallel algorithm, the authors have carried out systematic studies of the rheological properties of a variety of model liquid alkanes ranging from linear to singly branched and multiply branched alkanes. They aim to elucidate the relationship between the molecular architecture and the viscous behavior. Nonequilibrium molecular dynamics simulations have been carried out for n-decane (C{sub 10}H{sub 22}), n-hexadecane (C{sub 16}H{sub 34}), n-tetracosane (C{sub 24}H{sub 50}), 10-n-hexylnonadecane (C{sub 25}H{sub 52}), and squalane (2, 6, 10, 15, 19, 23-hexamethyltetracosane, C{sub 30}H{sub 62}). At a high strain rate, the viscosity shows a power-law shear thinning behavior over several orders of magnitude in strain rate, with exponents ranging from {minus}0.33 to {minus}0.59. The power-law shear thinning is shown to be closely related to the ordering of the molecules. The molecular architecture is shown to have a significant influence on the power-law exponent. At a low strain rate, the viscosity behavior changes to a Newtonian plateau, whose accurate determination has been elusive in previous studies. The molecular order in this regime is essentially that of the equilibrium system, a signature of the linear response. The Newtonian plateau is verified by independent equilibrium molecular dynamics simulations using the Green-Kubo method. The reliable determination of the Newtonian viscosity from nonequilibrium molecular simulation permits us to calculate the viscosity index for squalane. The viscosity index is a widely used property to characterize the lubricant`s temperature performance, and the studies represent the first approach toward its determination by molecular simulation.

  10. Source apportionment of PAHs and n-alkanes in respirable particles in Tehran, Iran by wind sector and vertical profile.

    Science.gov (United States)

    Moeinaddini, Mazaher; Esmaili Sari, Abbas; Riyahi bakhtiari, Alireza; Chan, Andrew Yiu-Chung; Taghavi, Seyed Mohammad; Hawker, Darryl; Connell, Des

    2014-06-01

    The vertical concentration profiles and source contributions of polycyclic aromatic hydrocarbons (PAHs) and n-alkanes in respirable particle samples (PM4) collected at 10, 100, 200 and 300-m altitude from the Milad Tower of Tehran, Iran during fall and winter were investigated. The average concentrations of total PAHs and total n-alkanes were 16.7 and 591 ng/m(3), respectively. The positive matrix factorization (PMF) model was applied to the chemical composition and wind data to apportion the contributing sources. The five PAH source factors identified were: 'diesel' (56.3% of total PAHs on average), 'gasoline' (15.5%), 'wood combustion, and incineration' (13%), 'industry' (9.2%), and 'road soil particle' (6.0%). The four n-alkane source factors identified were: 'petrogenic' (65% of total n-alkanes on average), 'mixture of petrogenic and biomass burning' (15%), 'mixture of biogenic and fossil fuel' (11.5%), and 'biogenic' (8.5%). Source contributions by wind sector were also estimated based on the wind sector factor loadings from PMF analysis. Directional dependence of sources was investigated using the conditional probability function (CPF) and directional relative strength (DRS) methods. The calm wind period was found to contribute to 4.4% of total PAHs and 5.0% of total n-alkanes on average. Highest average concentrations of PAHs and n-alkanes were found in the 10 and 100 m samples, reflecting the importance of contributions from local sources. Higher average concentrations in the 300 m samples compared to those in the 200 m samples may indicate contributions from long-range transport. The vertical profiles of source factors indicate the gasoline and road soil particle-associated PAHs, and the mixture from biogenic and fossil fuel source-associated n-alkanes were mostly from local emissions. The smaller average contribution of diesel-associated PAHs in the lower altitude samples also indicates that the restriction of diesel-fueled vehicle use in the central area

  11. Relationship between chemical structure of soil organic matter and intra-aggregate pore structure: evidence from X-ray computed micro-tomography

    Science.gov (United States)

    Kravchenko, Alexandra; Grandy, Stuart A.

    2014-05-01

    Understanding chemical structure of soil organic matter (SOM) and factors that affect it are vital for gaining understanding of mechanisms of C sequestration by soil. Physical protection of C by adsorption to mineral particles and physical disconnection between C sources and microbial decomposers is now regarded as the key component of soil C sequestration. Both of the processes are greatly influenced by micro-scale structure and distribution of soil pores. However, because SOM chemical structure is typically studied in disturbed (ground and sieved) soil samples the experimental evidence of the relationships between soil pore structure and chemical structure of SOM are still scarce. Our study takes advantage of the X-ray computed micro-tomography (µ-CT) tools that enable non-destructive analysis of pore structure in intact soil samples. The objective of this study is to examine the relationship between SOM chemical structure and pore-characteristics in intact soil macro-aggregates from two contrasting long-term land uses. The two studied land use treatments are a conventionally tilled corn-soybean-wheat rotation treatment and a native succession vegetation treatment removed from agricultural use >20 years ago. The study is located in southwest Michigan, USA, on sandy-loam Typic Hapludalfs. For this study we used soil macro-aggregates 4-6 mm in size collected at 0-15 cm depth. The aggregate size was selected so as both to enable high resolution of µ-CT and to provide sufficient amount of soil for C measurements. X-ray µ-CT scanning was conducted at APS Argonne at a scanning resolution of 14 µm. Two scanned aggregates (1 per treatment) were used in this preliminary study. Each aggregate was cut into 7 "geo-referenced" sections. Analyses of pore characteristics in each section were conducted using 3DMA and ImageJ image analysis tools. SOM chemistry was analyzed using pyrolysis/gas chromatography-mass spectroscopy. Results demonstrated that the relationships

  12. The Genes rubA and rubB for Alkane Degradation in Acinetobacter sp. Strain ADP1 Are in an Operon with estB, Encoding an Esterase, and oxyR

    OpenAIRE

    1999-01-01

    Alkanes are oxidized in Acinetobacter sp. strain ADP1 by a three-component alkane monooxygenase, composed of alkane hydroxylase, rubredoxin, and rubredoxin reductase. rubA and rubB encode rubredoxin and a NAD(P)H-dependent rubredoxin reductase. We demonstrate here that single base pair substitutions in rubA or rubB lead to defects in alkane degradation, showing that both genes are essential for alkane utilization. Differences in the degradation capacity for hexadecane and dodecane in these mu...

  13. Progressive degradation of crude oil n-alkanes coupled to methane production under mesophilic and thermophilic conditions.

    Directory of Open Access Journals (Sweden)

    Lei Cheng

    Full Text Available Although methanogenic degradation of hydrocarbons has become a well-known process, little is known about which crude oil tend to be degraded at different temperatures and how the microbial community is responded. In this study, we assessed the methanogenic crude oil degradation capacity of oily sludge microbes enriched from the Shengli oilfield under mesophilic and thermophilic conditions. The microbial communities were investigated by terminal restriction fragment length polymorphism (T-RFLP analysis of 16S rRNA genes combined with cloning and sequencing. Enrichment incubation demonstrated the microbial oxidation of crude oil coupled to methane production at 35 and 55°C, which generated 3.7±0.3 and 2.8±0.3 mmol of methane per gram oil, respectively. Gas chromatography-mass spectrometry (GC-MS analysis revealed that crude oil n-alkanes were obviously degraded, and high molecular weight n-alkanes were preferentially removed over relatively shorter-chain n-alkanes. Phylogenetic analysis revealed the concurrence of acetoclastic Methanosaeta and hydrogenotrophic methanogens but different methanogenic community structures under the two temperature conditions. Candidate divisions of JS1 and WWE 1, Proteobacteria (mainly consisting of Syntrophaceae, Desulfobacteraceae and Syntrophorhabdus and Firmicutes (mainly consisting of Desulfotomaculum were supposed to be involved with n-alkane degradation in the mesophilic conditions. By contrast, the different bacterial phylotypes affiliated with Caldisericales, "Shengli Cluster" and Synergistetes dominated the thermophilic consortium, which was most likely to be associated with thermophilic crude oil degradation. This study revealed that the oily sludge in Shengli oilfield harbors diverse uncultured microbes with great potential in methanogenic crude oil degradation over a wide temperature range, which extend our previous understanding of methanogenic degradation of crude oil alkanes.

  14. Degradability of n-alkanes during ex situ natural bioremediation of soil contaminated by heavy residual fuel oil (mazut

    Directory of Open Access Journals (Sweden)

    Ali Ramadan Mohamed Muftah

    2013-01-01

    Full Text Available It is well known that during biodegradation of oil in natural geological conditions, or oil pollutants in the environment, a degradation of hydrocarbons occurs according to the well defined sequence. For example, the major changes during the degradation process of n-alkanes occur in the second, slight and third, moderate level (on the biodegradation scale from 1 to 10. According to previous research, in the fourth, heavy level, when intensive changes of phenanthrene and its methyl isomers begin, n-alkanes have already been completely removed. In this paper, the ex situ natural bioremediation (unstimulated bioremediation, without addition of biomass, nutrient substances and biosurfactant of soil contaminated with heavy residual fuel oil (mazut was conducted during the period of 6 months. Low abundance of n-alkanes in the fraction of total saturated hydrocarbons in the initial sample (identification was possible only after concentration by urea adduction technique showed that the investigated oil pollutant was at the boundary between the third and the fourth biodegradation level. During the experiment, an intense degradation of phenanthrene and its methyl-, dimethyl-and trimethyl-isomers was not followed by the removal of the remaining n-alkanes. The abundance of n-alkanes remained at the initial low level, even at end of the experiment when the pollutant reached one of the highest biodegradation levels. These results showed that the unstimulated biodegradation of some hydrocarbons, despite of their high biodegradability, do not proceed completely to the end, even at final degradation stages. In the condition of the reduced availability of some hydrocarbons, microorganisms tend to opt for less biodegradable but more accessible hydrocarbons.

  15. Unusual N-Alkane Distributions in Extracts from Marine Carbonate Rocks at High Levels of Maturity and Overmaturity

    Institute of Scientific and Technical Information of China (English)

    LI JINGGUI(李景贵); R. PAUL PHILP; CUI MINGZHONG(崔明中)

    2002-01-01

    N-alkanes in extracts from possible carbonate source rocks of the Lower Ordovician Majiagou Formation in the central gas field of the Shanganning Basin and the Upper Sinian Dengying Formation in the Weiyuan gas field of the Sichuan Basin, are characterized by bimodal distributions with the dominant carbon numbers in the range C17-C21 and C25-C29. In most samples, the lower carbon number components are present in greater abundance than the higher carbon number ones. Most samples contain significant concentrations of waxy hydrocarbons ( C22 + )with C21-/C22+ ratios between 0.50 to 3.16, and an average value of 1.34. The n-alkanes in extracts of outcrops and shallow core samples of Upper Proterozoic and Lower Palaeozoic carbonate rocks in the western and southern parts of the North China Basin are of unimodal distributions dominated by n-alkanes maximizing in the C25-C29 range. These extracts have very high concentrations of waxy hydrocarbons with C21 -/C22 + ratios all <1.0, ranging from 0. 14 to 0. 90 and averaging 0.36. AⅡ of the extracts have a marked odd/even predominance in the high molecular weight n-alkane range regardless of whether they are from shallow or deep cores or outcrop samples. Simulation experiments were performed using typical sapropelic-type kerogens from the immature Sinian Lower Xiamalin Formation carbonate-rich shales collected at Jixian,Hebei Province, North China Basin, and the contemporary microplanktonic blue-green algae Spirulina subsala. Results indicate that the unusual distribution of n-alkanes in the extracts of Upper Proterozoic and Lower Palaeozoic carbonate rocks possibly originated from algae in the source rocks at high levels of maturity and overmaturity.

  16. Unusual N—Alkane Distributions in Extracts from Marine Carbonate Rocks at High Levels of Maturity and Overmaturity

    Institute of Scientific and Technical Information of China (English)

    李景贵; R.PAULPHILP; 等

    2002-01-01

    N-alkanes in extracts from possible carbonate source rocks of the Lower Ordovician Majiagou Formation in the central gas field of the Shanganning Basin and the Upper Sinian Dengying Formation in the Weiyuan gas field of the Sichuan Basin,are characterized by bimodal distributions with the dominant carbon numbers in the range C17-C21 and C25-C29.In most sam-ples,the lower carbon number components are present in greater abundance than the higher car-bon number ones.Most samples contain significant concentrations of waxy hydrocarbons(C22+)with C21-/C22+ ratios between 0.50 to 3.16 ,and an average value of 1.34.The n-alkanes in extracts of outcrops and shallow core samples of Upper Proterozoic and Lower Palaeozoic carbon-ate rocks in the western and southern parts of the North China Basin are of unimodal distribu-tions dominated by n-alkanes maximizing in the C25-C29 range.These extracts have very high concentrations of waxy hydrocarbons with C21-/C22+ ratios all<1.0,ranging from 0.14 to 0.90 and averaging 0.36.All of the extracts have a marked odd/even predominance in the high mo-lecular weight n-alkane range regardless of whether they are from shallow or deep cores or out-crop samples.Simulation experiments were performed using typical sapropelic-type kerogens from the immature Sinian Lower Xiamalin Formation carbonate-rich shales collected at Jixian ,Hebei Province,North China Basin ,and the contemporary microplanktonic blue-green algae Spirulina subsala.Results indicate that the unusual distribution of n-alkanes in the extracts of Upper Proterozoic and Lower Palaeozoic carbonate rocks possibly originated from algae in the source rocks at high levels fo maturity and overmaturity.

  17. Progressive degradation of crude oil n-alkanes coupled to methane production under mesophilic and thermophilic conditions.

    Science.gov (United States)

    Cheng, Lei; Shi, Shengbao; Li, Qiang; Chen, Jianfa; Zhang, Hui; Lu, Yahai

    2014-01-01

    Although methanogenic degradation of hydrocarbons has become a well-known process, little is known about which crude oil tend to be degraded at different temperatures and how the microbial community is responded. In this study, we assessed the methanogenic crude oil degradation capacity of oily sludge microbes enriched from the Shengli oilfield under mesophilic and thermophilic conditions. The microbial communities were investigated by terminal restriction fragment length polymorphism (T-RFLP) analysis of 16S rRNA genes combined with cloning and sequencing. Enrichment incubation demonstrated the microbial oxidation of crude oil coupled to methane production at 35 and 55°C, which generated 3.7±0.3 and 2.8±0.3 mmol of methane per gram oil, respectively. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that crude oil n-alkanes were obviously degraded, and high molecular weight n-alkanes were preferentially removed over relatively shorter-chain n-alkanes. Phylogenetic analysis revealed the concurrence of acetoclastic Methanosaeta and hydrogenotrophic methanogens but different methanogenic community structures under the two temperature conditions. Candidate divisions of JS1 and WWE 1, Proteobacteria (mainly consisting of Syntrophaceae, Desulfobacteraceae and Syntrophorhabdus) and Firmicutes (mainly consisting of Desulfotomaculum) were supposed to be involved with n-alkane degradation in the mesophilic conditions. By contrast, the different bacterial phylotypes affiliated with Caldisericales, "Shengli Cluster" and Synergistetes dominated the thermophilic consortium, which was most likely to be associated with thermophilic crude oil degradation. This study revealed that the oily sludge in Shengli oilfield harbors diverse uncultured microbes with great potential in methanogenic crude oil degradation over a wide temperature range, which extend our previous understanding of methanogenic degradation of crude oil alkanes.

  18. Compositional characteristics of n-alkanes of the glaciers over the Tibetan Plateau and their environmental and climatic significances

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    We report on the concentration and compositional features of n-alkanes of natural and anthropogenic origins in the snow samples collected from the Qiyi glacier in the Qilian Mountains, the Yuzhufeng glacier in eastern Kunlun Mountains, the Xiaodongkemadi glacier in the Tanggula Mountains, and the Gurenhekou glacier in the Nyainqêntanglha Range. The results indicate a decrease in the total n-alkane concentration (T-HCs) from the northeast to the south over the Tibetan Plateau. The T-HCs in these studied areas were close to those in the Belukha and Sofiyskiy glacier, Russian Alati Mountains and the Dasuopu glacier in the Himalaya but were much higher than those in the Greenland ice sheet, suggesting that the mountain glaciers in the Asian continent may receive a higher loading of n-alkanes than the Greenland ice core. Moreover, the compositional characteristics of n-alkanes indicated that the n-alkanes in the studied areas were probably originated from the plant waxes as well as the fossil-fuel combustion exhaust, whereas the contribution from the lower organisms was small. In addition, the plant wax (Cn(wax)) and anthropogenic (non-Cn(wax)) contributions revealed that fast industrialization may have significant effects on the organic pollutant composition in glacier over the Tibetan Plateau and its circumference environment. Particularly, except for the Yuzhufeng glacier, the ΣnC21-/ΣnC22+ and (nC15+nC17+nC19)/(nC27+nC29+nC31) ratio decreased from the Qiyi glacier to the Gurenhekou glacier over the Tibetan Plateau, while the carbon preference index (CPI) values increased. These results indicate a decrease in terrigenous input while an increase in marine input from the northeast to the south over the Tibetan Plateau. These two ratios can be used as the climatic and environmental change indicators.

  19. Leaf wax n-alkane δD values are determined early in the ontogeny of Populus trichocarpa leaves when grown under controlled environmental conditions.

    Science.gov (United States)

    Kahmen, Ansgar; Dawson, Todd E; Vieth, Andrea; Sachse, Dirk

    2011-10-01

    The stable hydrogen isotope ratios (δD) of leaf wax n-alkanes record valuable information on plant and ecosystem water relations. It remains, however, unknown if leaf wax n-alkane δD values record only environmental variation during the brief period of time of leaf growth or if leaf wax n-alkane δD values are affected by environmental variability throughout the entire lifespan of a leaf. To resolve these uncertainties, we irrigated Populus trichocarpa trees with a pulse of deuterium-enriched water and used compound-specific stable hydrogen isotope analyses to test if the applied tracer could be recovered from leaf wax n-alkanes of leaves that were at different stages of their development during the tracer application. Our experiment revealed that only leaf wax n-alkanes from leaves that had developed during the time of the tracer application were affected, while leaves that were already fully matured at the time of the tracer application were not. We conclude from our study that under controlled environmental conditions, leaf wax n-alkanes are synthesized only early in the ontogeny of a leaf. Our experiment has implications for the interpretation of leaf wax n-alkane δD values in an environmental context, as it suggests that these compounds record only a brief period of the environmental variability that a leaf experiences throughout its life.

  20. RNAi silencing of a cytochrome P450 monoxygenase disrupts the ability of a filamentous fungus, Graphium sp., to grow on short-chain gaseous alkanes and ethers.

    Science.gov (United States)

    Trippe, Kristin M; Wolpert, Thomas J; Hyman, Michael R; Ciuffetti, Lynda M

    2014-02-01

    Graphium sp. (ATCC 58400), a filamentous fungus, is one of the few eukaryotes that grows on short-chain alkanes and ethers. In this study, we investigated the genetic underpinnings that enable this fungus to catalyze the first step in the alkane and ether oxidation pathway. A gene, CYP52L1, was identified, cloned and functionally characterized as an alkane-oxidizing cytochrome P450 (GSPALK1). Analysis of CYP52L1 suggests that it is a member of the CYP52 cytochrome P450 family, which is comprised of medium- and long-chain alkane-oxidizing enzymes found in yeasts. However, phylogenetic analysis of GSPALK1 with other CYP52 members suggests they are not closely related. Post-transcriptional ds-RNA-mediated gene silencing of CYP52L1 severely reduced the ability of this fungus to oxidize alkanes and ethers, however, downstream metabolic steps in these pathways were unaffected. Collectively, the results of this study suggest that GSPALK1 is the enzyme that catalyzes the initial oxidation of alkanes and ethers but is not involved in the later steps of alkane or ether metabolism.

  1. Environmental and biosynthetic influences on carbon and hydrogen isotope ratios of leaf wax n-alkanes

    Science.gov (United States)

    McInerney, F. A.; Freeman, K. H.; Polissar, P. J.; Feakins, S. J.

    2013-12-01

    Both carbon and hydrogen isotope ratios of leaf-wax n-alkanes are influenced by the availability of water in a plant's growth environment. Carbon isotope ratios of bulk tissues in C3 plants demonstrate a strong inverse relationship with measures of available moisture (e.g. mean annual precipitation and precipitation/evaporation). Similarly, hydrogen isotope ratios of leaf wax n-alkanes (δDl) can be enriched relative to precipitation (δDw) by transpiration, which is related to relative humidity and the leaf-to-air vapor pressure deficit. Thus, D-enrichment of leaf-wax n-alkanes relative to precipitation, termed the apparent fractionation (2ɛl/w), becomes more positive with increasing aridity. In theory, more positive values of leaf-wax δ13C (δ13Cl) and 2ɛl/w of leaf-wax n-alkanes should both correspond to more arid conditions in C3 plants. Here we review published and unpublished data on over 100 plants to examine this relationship. Contrary to expectations, C3 dicots show no clear relationship between δ13Cl and 2ɛl/w. This global lack of correlation is surprising given our understanding of aridity related isotopic effects in C3 plants. One possibility is that the implicit assumption of constant fractionation between lipid and bulk tissue is flawed due to the effects of different biosynthetic carriers and reaction pathways. We explore this possibility by examining the offset of leaf-wax carbon isotopes from the bulk leaf tissue (13ɛl/bulk). Different offsets would indicate additional biosynthetic processes are affecting δ13Cl in addition to any direct effects from aridity. We find that 13ɛl/bulk is highly variable, ranging from -1 to -16‰, which could explain the lack of correlation between δ13Cl and 2ɛl/w. In addition, 13ɛl/bulk values for C3 and C4 monocots (averages of -10.6 and -11.4‰ respectively) represent significantly greater offset between leaf wax and bulk tissue than in C3 dicots (average of -4.3‰), which is consistent with previous

  2. Solubility of gold nanoparticles as a function of ligand shell and alkane solvent.

    Science.gov (United States)

    Lohman, Brandon C; Powell, Jeffrey A; Cingarapu, Sreeram; Aakeroy, Christer B; Chakrabarti, Amit; Klabunde, Kenneth J; Law, Bruce M; Sorensen, Christopher M

    2012-05-14

    The solubility of ca. 5.0 nm gold nanoparticles was studied systematically as a function of ligand shell and solvent. The ligands were octane-, decane-, dodecane- and hexadecanethiols; the solvents were the n-alkanes from hexane to hexadecane and toluene. Supernatant concentrations in equilibrium with precipitated superclusters of nanoparticles were measured at room temperature (23 °C) with UV-Vis spectrophotometry. The solubility of nanoparticles ligated with decane- and dodecanethiol was greatest in n-decane and n-dodecane, respectively. In contrast, the solubility of nanoparticles ligated with octane- and hexadecanethiol showed decreasing solubility with increasing solvent chain length. In addition the solubility of the octanethiol ligated system showed a nonmonotonic solvent carbon number functionality with even numbered solvents being better solvents than neighboring odd numbered solvents.

  3. Mass transfer and adsorption equilibrium for low volatility alkanes in BPL activated carbon.

    Science.gov (United States)

    Wang, Yu; Mahle, John J; Furtado, Amanda M B; Glover, T Grant; Buchanan, James H; Peterson, Gregory W; LeVan, M Douglas

    2013-03-01

    The structure of a molecule and its concentration can strongly influence diffusional properties for transport in nanoporous materials. We study mass transfer of alkanes in BPL activated carbon using the concentration-swing frequency response method, which can easily discriminate among mass transfer mechanisms. We measure concentration-dependent diffusion rates for n-hexane, n-octane, n-decane, 2,7-dimethyloctane, and cyclodecane, which have different carbon numbers and geometries: straight chain, branched chain, and cyclic. Micropore diffusion is determined to be the controlling mass transfer resistance except at low relative saturation for n-decane, where an external mass transfer resistance also becomes important, showing that the controlling mass transfer mechanism can change with system concentration. Micropore diffusion coefficients are found to be strongly concentration dependent. Adsorption isotherm slopes obtained from measured isotherms, the concentration-swing frequency response method, and a predictive method show reasonably good agreement.

  4. Analyzing solubility of acid gas and light alkanes in triethylene glycol

    Institute of Scientific and Technical Information of China (English)

    Alireza Bahadori; Had B.Vuthaluru; Saeid Mokhatab

    2008-01-01

    Physical solvents such as ethylene glycol (EG), diethylene glycol (DEG), and triethylene glycol (TEG) are commonly used in wet gas dehydration processes with TEG being the most popular due to ease of regeneration and low solvent losses. Unfortunately, TEG absorbs significantly more hydrocarbons and acid gases than EG or DEG. Quantifying this amount of absorption is therefore critical in order to minimize hydrocarbon losses or to optimize hydrocarbon recovery depending on the objective of the process. In this article, a new correlation that fully covers the operating ranges of TEG dehydration units is developed in order to determine the solubility of light alkanes and acid gases in TEG solvent. The influence of several parameters on hydrocarbon and acid gas solubility including temperature, pressure, and solvent content is also examined.

  5. Self-consistent molecular dynamics calculation of diffusion in higher n-alkanes

    Science.gov (United States)

    Kondratyuk, Nikolay D.; Norman, Genri E.; Stegailov, Vladimir V.

    2016-11-01

    Diffusion is one of the key subjects of molecular modeling and simulation studies. However, there is an unresolved lack of consistency between Einstein-Smoluchowski (E-S) and Green-Kubo (G-K) methods for diffusion coefficient calculations in systems of complex molecules. In this paper, we analyze this problem for the case of liquid n-triacontane. The non-conventional long-time tails of the velocity autocorrelation function (VACF) are found for this system. Temperature dependence of the VACF tail decay exponent is defined. The proper inclusion of the long-time tail contributions to the diffusion coefficient calculation results in the consistency between G-K and E-S methods. Having considered the major factors influencing the precision of the diffusion rate calculations in comparison with experimental data (system size effects and force field parameters), we point to hydrogen nuclear quantum effects as, presumably, the last obstacle to fully consistent n-alkane description.

  6. Xenon and halogenated alkanes track putative substrate binding cavities in the soluble methane monooxygenase hydroxylase.

    Science.gov (United States)

    Whittington, D A; Rosenzweig, A C; Frederick, C A; Lippard, S J

    2001-03-27

    To investigate the role of protein cavities in facilitating movement of the substrates, methane and dioxygen, in the soluble methane monooxygenase hydroxylase (MMOH), we determined the X-ray structures of MMOH from Methylococcus capsulatus (Bath) cocrystallized with dibromomethane or iodoethane, or by using crystals pressurized with xenon gas. The halogenated alkanes bind in two cavities within the alpha-subunit that extend from one surface of the protein to the buried dinuclear iron active site. Two additional binding sites were located in the beta-subunit. Pressurization of two crystal forms of MMOH with xenon resulted in the identification of six binding sites located exclusively in the alpha-subunit. These results indicate that hydrophobic species bind preferentially in preexisting cavities in MMOH and support the hypothesis that such cavities may play a functional role in sequestering and enhancing the availability of the physiological substrates for reaction at the active site.

  7. Catalytic conversion of light alkanes, Phase 1. Topical report, January 1990--January 1993

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1993-12-31

    The authors have found a family of new catalytic materials which, if successfully developed, will be effective in the conversion of light alkanes to alcohols or other oxygenates. Catalysts of this type have the potential to convert natural gas to clean-burning high octane liquid fuels directly without requiring the energy-intensive steam reforming step. In addition they also have the potential to upgrade light hydrocarbons found in natural gas to a variety of high value fuel and chemical products. In order for commercially useful processes to be developed, increases in catalytic life, reaction rate and selectivity are required. Recent progress in the experimental program geared to the further improvement of these catalysts is outlined.

  8. A Quantitative Structure Property Relationship for Prediction of Flash Point of Alkanes Using Molecular Connectivity Indices

    Institute of Scientific and Technical Information of China (English)

    Morteza Atabati; Reza Emamalizadeh

    2013-01-01

    Many structure-property/activity studies use graph theoretical indices,which are based on the topological properties of a molecule viewed as a graph.Since topological indices can be derived directly from the molecular structure without any experimental effort,they provide a simple and straightforward method for property prediction.In this work the flash point of alkanes was modeled by a set of molecular connectivity indices (x),modified molecular connectivity indices (mx(1)h) and valance molecular connectivity indices (mxv),with mxv calculated using the hydrogen perturbation.A stepwise Multiple Linear Regression (MLR) method was used to select the best indices.The predicted flash points are in good agreement with the experimental data,with the average absolute deviation 4.3 K.

  9. Measurements and analysis of excess enthalpies of ester + n-alkane using the UNIFAC model

    Energy Technology Data Exchange (ETDEWEB)

    Ortega, J. (Escuela Superior de Ingenieros Industriales, Las Palmas (Spain). Catedra de Termodinamica y Fisicoquimica); Legido, J.L.; Fernandez, J.; Pias, L.; Paz Andrade, M.I. (Universidad de Santiago de Compostela (Spain). Dept. de Fisica Aplicada)

    1991-02-01

    We present new experimental data of the excess molar enthalpies at 298.15 K for eighteen different binary mixtures of nine methyl alkanoates (ethanoate to decanoate) with n-heptane and n-undecane. The results show that all the systems are endothermic, h{sup E} values increase with the length of the n-alkane and decrease with the length of the methyl ester. The data have been analysed with a version of the UNIFAC model, and the parameters corresponding to the CH{sub 2}/COOC interaction have been recalculated using a larger base of experimental data. New values for the CH{sub 2}/COO interaction parameters have been obtained. (orig.).

  10. Reactivity and fate of secondary alkane sulfonates (SAS) in marine sediments.

    Science.gov (United States)

    Baena-Nogueras, Rosa María; Rojas-Ojeda, Patricia; Sanz, José Luis; González-Mazo, Eduardo; Lara-Martín, Pablo A

    2014-06-01

    This research is focused on secondary alkane sulfonates (SAS), anionic surfactants widely used in household applications that access aquatic environments mainly via sewage discharges. We studied their sorption capacity and anaerobic degradation in marine sediments, providing the first data available on this topic. SAS partition coefficients increased towards those homologues having longer alkyl chains (from up to 141 L kg(-1) for C14 to up to 1753 L kg(-1) for C17), which were those less susceptible to undergo biodegradation. Overall, SAS removal percentages reached up to 98% after 166 days of incubation using anoxic sediments. The degradation pathway consisted on the formation of sulfocarboxylic acids after an initial fumarate attack of the alkyl chain and successive β-oxidations. This is the first study showing that SAS can be degraded in absence of oxygen, so this new information should be taken into account for future environmental risk assessments on these chemicals.

  11. Quantifying sources of methane using light alkanes in the Los Angeles basin, California

    Science.gov (United States)

    Peischl, J.; Ryerson, T. B.; Brioude, J.; Aikin, K. C.; Andrews, A. E.; Atlas, E.; Blake, D.; Daube, B. C.; Gouw, J. A.; Dlugokencky, E.; Frost, G. J.; Gentner, D. R.; Gilman, J. B.; Goldstein, A. H.; Harley, R. A.; Holloway, J. S.; Kofler, J.; Kuster, W. C.; Lang, P. M.; Novelli, P. C.; Santoni, G. W.; Trainer, M.; Wofsy, S. C.; Parrish, D. D.

    2013-05-01

    Methane (CH4), carbon dioxide (CO2), carbon monoxide (CO), and C2-C5 alkanes were measured throughout the Los Angeles (L.A.) basin in May and June 2010. We use these data to show that the emission ratios of CH4/CO and CH4/CO2 in the L.A. basin are larger than expected from population-apportioned bottom-up state inventories, consistent with previously published work. We use experimentally determined CH4/CO and CH4/CO2 emission ratios in combination with annual State of California CO and CO2 inventories to derive a yearly emission rate of CH4 to the L.A. basin. We further use the airborne measurements to directly derive CH4 emission rates from dairy operations in Chino, and from the two largest landfills in the L.A. basin, and show these sources are accurately represented in the California Air Resources Board greenhouse gas inventory for CH4. We then use measurements of C2-C5 alkanes to quantify the relative contribution of other CH4 sources in the L.A. basin, with results differing from those of previous studies. The atmospheric data are consistent with the majority of CH4 emissions in the region coming from fugitive losses from natural gas in pipelines and urban distribution systems and/or geologic seeps, as well as landfills and dairies. The local oil and gas industry also provides a significant source of CH4 in the area. The addition of CH4 emissions from natural gas pipelines and urban distribution systems and/or geologic seeps and from the local oil and gas industry is sufficient to account for the differences between the top-down and bottom-up CH4 inventories identified in previously published work.

  12. Comparative study of normal and branched alkane monolayer films adsorbed on a solid surface. II. Dynamics

    Science.gov (United States)

    Enevoldsen, A. D.; Hansen, F. Y.; Diama, A.; Taub, H.; Dimeo, R. M.; Neumann, D. A.; Copley, J. R. D.

    2007-03-01

    The dynamics of monolayer films of the n-alkane tetracosane (n-C24H52) and the branched alkane squalane (C30H62) adsorbed on graphite have been studied by quasielastic and inelastic neutron scattering and molecular dynamics (MD) simulations. Both molecules have 24 carbon atoms along their carbon backbone, and squalane has an additional six methyl side groups symmetrically placed along its length. The authors' principal objective has been to determine the influence of the side groups on the dynamics of the squalane monolayer and thereby assess its potential as a nanoscale lubricant. To investigate the dynamics of these monolayers they used both the disk chopper spectrometer (DCS) and the high flux backscattering spectrometer (HFBS) at the National Institute of Standards and Technology. These instruments made it possible to study dynamical processes such as molecular diffusive motions and vibrations on very different time scales: 1-40ps (DCS) and 0.1-4ns (HFBS). The MD simulations were done on corresponding time scales and were used to interpret the neutron spectra. The authors found that the dynamics of the two monolayers are qualitatively similar on the respective time scales and that there are only small quantitative differences that can be understood in terms of the different masses and moments of inertia of the two molecules. In the course of this study, the authors developed a procedure to separate out the low-frequency vibrational modes in the spectra, thereby facilitating an analysis of the quasielastic scattering. They conclude that there are no major differences in the monolayer dynamics caused by intramolecular branching. It remains to be seen whether this similarity in monolayer dynamics also holds for the lubricating properties of these molecules in confined geometries.

  13. Comparative study of normal and branched alkane monolayer films adsorbed on a solid surface. I. Structure

    Science.gov (United States)

    Enevoldsen, A. D.; Hansen, F. Y.; Diama, A.; Criswell, L.; Taub, H.

    2007-03-01

    The structure of a monolayer film of the branched alkane squalane (C30H62) adsorbed on graphite has been studied by neutron diffraction and molecular dynamics (MD) simulations and compared with a similar study of the n-alkane tetracosane (n-C24H52). Both molecules have 24 carbon atoms along their backbone and squalane has, in addition, six methyl side groups. Upon adsorption, there are significant differences as well as similarities in the behavior of these molecular films. Both molecules form ordered structures at low temperatures; however, while the melting point of the two-dimensional (2D) tetracosane film is roughly the same as the bulk melting point, the surface strongly stabilizes the 2D squalane film such that its melting point is 91K above its value in bulk. Therefore, squalane, like tetracosane, will be a poor lubricant in those nanoscale devices that require a fluid lubricant at room temperature. The neutron diffraction data show that the translational order in the squalane monolayer is significantly less than in the tetracosane monolayer. The authors' MD simulations suggest that this is caused by a distortion of the squalane molecules upon adsorption on the graphite surface. When the molecules are allowed to relax on the surface, they distort such that all six methyl groups point away from the surface. This results in a reduction in the monolayer's translational order characterized by a decrease in its coherence length and hence a broadening of the diffraction peaks. The MD simulations also show that the melting mechanism in the squalane monolayer is the same footprint reduction mechanism found in the tetracosane monolayer, where a chain melting drives the lattice melting.

  14. Kinetic and Mechanistic Assessment of Alkanol/Alkanal Decarbonylation and Deoxygenation Pathways on Metal Catalysts.

    Science.gov (United States)

    Gürbüz, Elif I; Hibbitts, David D; Iglesia, Enrique

    2015-09-23

    This study combines theory and experiment to determine the kinetically relevant steps and site requirements for deoxygenation of alkanols and alkanals. These reactants deoxygenate predominantly via decarbonylation (C-C cleavage) instead of C-O hydrogenolysis on Ir, Pt, and Ru, leading to strong inhibition effects by chemisorbed CO (CO*). C-C cleavage occurs via unsaturated species formed in sequential quasi-equilibrated dehydrogenation steps, which replace C-H with C-metal bonds, resulting in strong inhibition by H2, also observed in alkane hydrogenolysis. C-C cleavage occurs in oxygenates only at locations vicinal to the C═O group in RCCO* intermediates, because such adjacency weakens C-C bonds, which also leads to much lower activation enthalpies for oxygenates than hydrocarbons. C-O hydrogenolysis rates are independent of H2 pressure and limited by H*-assisted C-O cleavage in RCHOH* intermediates on surfaces with significant coverages of CO* formed in decarbonylation events. The ratio of C-O hydrogenolysis to decarbonylation rates increased almost 100-fold as the Ir cluster size increased from 0.7 to 7 nm; these trends reflect C-O hydrogenolysis reactions favored on terrace sites, while C-C hydrogenolysis prefers sites with lower coordination, because of the relative size of their transition states and the crowded nature of CO*-covered surfaces. C-O hydrogenolysis becomes the preferred deoxygenation route on Cu-based catalysts, thus avoiding CO inhibition effects. The relative rates of C-O and C-C cleavage on these metals depend on their relative ability to bind C atoms, because C-C cleavage transitions states require an additional M-C attachment.

  15. Insect attachment on crystalline bioinspired wax surfaces formed by alkanes of varying chain lengths

    Directory of Open Access Journals (Sweden)

    Elena Gorb

    2014-07-01

    Full Text Available The impeding effect of plant surfaces covered with three-dimensional wax on attachment and locomotion of insects has been shown previously in numerous experimental studies. The aim of this study was to examine the effect of different parameters of crystalline wax coverage on insect attachment. We performed traction experiments with the beetle Coccinella septempunctata and pull-off force measurements with artificial adhesive systems (tacky polydimethylsiloxane semi-spheres on bioinspired wax surfaces formed by four alkanes of varying chain lengths (C36H74, C40H82, C44H90, and C50H102. All these highly hydrophobic coatings were composed of crystals having similar morphologies but differing in size and distribution/density, and exhibited different surface roughness. The crystal size (length and thickness decreased with an increase of the chain length of the alkanes that formed these surfaces, whereas the density of the wax coverage, as well as the surface roughness, showed an opposite relationship. Traction tests demonstrated a significant, up to 30 fold, reduction of insect attachment forces on the wax surfaces when compared with the reference glass sample. Attachment of the beetles to the wax substrates probably relied solely on the performance of adhesive pads. We found no influence of the wax coatings on the subsequent attachment ability of beetles. The obtained data are explained by the reduction of the real contact between the setal tips of the insect adhesive pads and the wax surfaces due to the micro- and nanoscopic roughness introduced by wax crystals. Experiments with polydimethylsiloxane semi-spheres showed much higher forces on wax samples when compared to insect attachment forces measured on these surfaces. We explain these results by the differences in material properties between polydimethylsiloxane probes and tenent setae of C. septempunctata beetles. Among wax surfaces, force experiments showed stronger insect attachment and higher

  16. [Composition of n-alkanes in soils of the Yellow River Estuary Wetlands and their potential as organic matter source indicators].

    Science.gov (United States)

    Yao, Peng; Yin, Hong-Zhen; Yao, Qing-Zhen; Chen, Hong-Tao; Liu, Yue-Liang

    2012-10-01

    Abstract: Surface soil samples from the Yellow River Estuary Wetlands were analyzed for total organic carbon (TOC) and n-alkanes. Molecular indicators of n-alkanes were calculated and their potential as organic matter source indicators was discussed and compared among different sampling areas and times. C25-C33 n-alkanes with odd-to-even predominance were observed in most surface soils of the wetlands, suggesting the dominant contribution of terrestrial higher plants for the soil organic matter (SOM), and the ubiquitous presence of unresolved complex mixture indicated the presence of petroleum contamination. Total n-alkane concentrations in soils varied from 0.57 microg x g(-1) to 3.90 microg x g(-1), and distinct spatial and temporal differences were observed. In April 2009 (dry season), total n-alkane concentration was higher than that in June 2009 (during water-sediment regulation) with the maximum concentration observed at the core area of the wetlands, followed by the north side of the Yellow River after the last pontoon bridge, and the abandoned channel area of the Yellow River. The opposite trend of total n-alkane concentration was observed in June. The variation of total n-alkane concentration at two sampling time points were positively correlated with TOC and negatively correlated with sediment grain size, suggesting the influence of hydro-environment on the accumulation of soil organic matter. Molecular indicators of n-alkanes, such as average chain length (ACL), odd-even predominance (OEP), alkane index (AI), carbon preference index (CPI) and Terrigenous/ Aquatic Ratio (TAR) indicated that the maturity of organic matter in soils of the wetlands was low, and the dominant source of the SOM was terrestrial higher plants and mainly herbaceous plants. Compared with other indicators, TAR is better in reflecting the variation of hydro-environment.

  17. Hydrogen isotopic characteristics and their genetic relationships for individual n-alkanes in plants and sediments from Zoigê marsh sedimentary environment

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    To understand internal relations of their hydrogen isotopic compositions in typical marsh environment, we, using GC-IRMS analytical technique, measured the hydrogen isotopes of individual n-alkanes in the herbaceous plant, woody plant leaf, and sediments from Zoigê marsh in China. The results show significant differences in the hydrogen isotopic compositions of n-alkanes among the different kinds of plants and the different species in the same kind. δD values of n-alkanes in the herbaceous plants (from -254‰ to -184‰) are lighter than those in woody plant leaf ( from -195‰ to -142‰ ), and the hydrogen isotopic compositions of n-alkanes in K. tibetica P. are lighter than P. pratensis L. The mean δD values of n-alkanes in the sediments from Zoigê marsh reflect that they were derived from herbaceous plants, which is consistent with the peat samples being composed mainly of herbaceous plant remnants. The significant differences in hydrogen isotopic compositions of n-alkanes among the sedimentary samples are caused possibly by environment factors and the difference in input quantity of different herbaceous plants. A certain negative correlation exists between the δ13C and δD values of n-alkanes in the samples, and plant types can be distinguished using the cross plot of δD vs. δ13C values of n-alkanes in the plants. These data and recognitions provide scientific basis for hydrogen isotopic applied research of individual n-alkanes.

  18. n-alkane distribution coupled with organic carbon isotope composition in the shell bar section, Qarhan paleolake, Qaidam basin, NE Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    Yang PU; Hucai ZHANG; Guoliang LEI; Fengqin CHANG; Mingsheng YANG; Xianyu HUANG

    2009-01-01

    Lipids extracted from lacustrine deposits in the paleolake Qarhan of the Qaidam basin in the northeastern Tibetan Plateau were determined by conventional gas chromatography-mass spectrometry. Several series of biomarkers were identified, mainly including n-alkanes, n-alkan-2-ones, n-alkanoic acids, branched alkanes, triter-penoids and steroids, indicative of various biogenic contributions. On the basis of cluster analysis, the n-C15, n-C17, n-C19 alkanes were proposed to be derived from algae and/or photosynthetic bacteria, the n-C21 n-C23, n-C25 homologues from aquatic plants, and the n-C29, n-C31 homologues from vascular plants. In contrast, the n-C27 alkane is not categorized in the n-C29 and n-C31 group of alkanes, probably due to more complex origins including both aquatic and vascular plants, and/or differential biodegradation. Stratigraphically, layers-2, 4 and 5 were found to show a close relationship in n-alkane distribution, associated with a positive shift in carbon isotope composition of bulk organic matter (δ13Corg), inferring a cold/dry period. Layers-1 and 6 were clustered together in association with a negative δ13Corg excursion, probably indicating a relatively warm/humid climate. The potential coupling between the n-alkane distributions and δ13Corg, suggests a consequence of vegetation change in response to climate change, with the late MIS3 being shown to be unstable, thought to be the climatic optimum in the Tibetan Plateau. Our results suggest that the cluster analysis used in this study probably provides an effective and authentic method to investigate the n-alkane distribution in paleolake sediments.

  19. Spontaneous Imbibition Dynamics of an n-Alkane in Nanopores: Evidence of Meniscus Freezing and Monolayer Sticking

    CERN Document Server

    Gruener, Simon; 10.1103/PhysRevLett.103.174501

    2009-01-01

    Capillary filling dynamics of liquid n-tetracosane (n-C24H50) in a network of cylindrical pores with 7 and 10 nm mean diameter in monolithic silica glass (Vycor) exhibit an abrupt temperature-slope change at Ts=54 deg C, ~4 deg C above bulk and ~16 deg C, 8 deg C, respectively, above pore freezing. It can be traced to a sudden inversion of the surface tension's T slope, and thus to a decrease in surface entropy at the advancing pore menisci, characteristic of the formation of a single solid monolayer of rectified molecules, known as surface freezing from macroscopic, quiescent tetracosane melts. The imbibition speeds, that are the squared prefactors of the observed square-root-of-time Lucas-Washburn invasion kinetics, indicate a conserved bulk fluidity and capillarity of the nanopore-confined liquid, if we assume a flat lying, sticky hydrocarbon backbone monolayer at the silica walls.

  20. The Effect of Using XO Computers on Students' Mathematics and Reading Abilities: Evidences from Learning Achievement Tests Conducted in Primary Education Schools in Mongolia

    Science.gov (United States)

    Yamaguchi, Shinobu; Sukhbaatar, Javzan; Takada, Jun-ichi; Dayan-Ochir, Khishigbuyan

    2014-01-01

    In 2008, Mongolia took part in One Laptop per Child (OLPC) project. Since that time, over 10,000 students in grades 2-5 in 43 primary education schools are using XO computers. This paper presents the findings of a study conducted in 2012 to evaluate the impact of the OLPC initiatives on students' literacy and math skills. This study covered 14…