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1

Binary chromatographic data and estimation of adsorbent porosities. [data for system n-heptane/n-pentane  

NASA Technical Reports Server (NTRS)

Data for the system n-pentane/n-heptane on porous Chromosorb-102 adsorbent were obtained at 150, 175, and 200 C for mixtures containing zero to 100% n-pentane by weight. Prior results showing limitations on superposition of pure component data to predict multicomponent chromatograms were verified. The thermodynamic parameter MR0 was found to be a linear function of sample composition. A nonporous adsorbent failed to separate the system because of large input sample dispersions. A proposed automated data processing scheme involving magnetic tape recording of the detector signals and processing by a minicomputer was rejected because of resolution limitations of the available a/d converters. Preliminary data on porosity and pore size distributions of the adsorbents were obtained.

Meisch, A. J.

1972-01-01

2

Effect of methanol on the biofiltration of n-hexane.  

PubMed

This study investigated the removal of recalcitrant compounds in the presence of a hydrophilic compound. n-Hexane is used as a model compound to represent hydrophobic compounds. Methanol has been introduced in mixture with n-hexane in order to increase the bioavailability of n-hexane in trickle-bed-air-biofilters (TBABs). The mixing ratios investigated were: 70% methanol:30% n-hexane, and 80% methanol:20% n-hexane by volume. n-Hexane loading rates (LRs) ranged from 0.9 to 13.2 g m(-3) h(-1). Methanol LRs varied from 4.6 to 64.5 g m(-3) h(-1) and from 2.3 to 45.2 g m(-3) h(-1) depending upon the mixing ratio used. Biofilter performance, effect of mixing ratios of methanol to n-hexane, removal profile along biofilter depth, COD/nitrogen consumption and CO(2) production were studied under continuous loading operation conditions. Results have shown that the degradation of n-hexane is significantly enhanced by the presence of methanol for n-hexane LRs less than 13.2 g m(-3) h(-1). For n-hexane LR greater than 13.2 g m(-3) h(-1), even though methanol had impacted n-hexane biodegradation, its removal efficiency was higher than our previous study for biodegradation of n-hexane alone, in presence of surfactant, or in presence of benzene. On the other hand, the degradation of methanol was not impacted by the presence of n-hexane. PMID:22516522

Zehraoui, Abderrahman; Hassan, Ashraf Aly; Sorial, George A

2012-06-15

3

Industrial application of catalytic systems for n-heptane isomerization.  

PubMed

The ideal gasoline must have a high pump octane number, in the 86 to 94 range, and a low environmental impact. Alkanes, as a family, have much lower photochemical reactivities than aromatics or olefins, but only the highly branched alkanes have adequate octane numbers. The purpose of this work is to examine the possibilities of extending the technological alternative of paraffin isomerization to heavier feedstocks (i.e., n-heptane) using non-conventional catalytic systems which have been previously proposed in the literature: a Pt/sulfated zirconia catalyst and a molybdenum sub-oxide catalyst. Under the experimental conditions at which these catalysts have been evaluated, the molybdenum sub-oxide catalyst maintains a good activity and selectivity to isomerization after 24 h, while the Pt/sulfated zirconia catalyst shows a higher dimethylpentanes/methylhexanes ratio, probably due to a lower operating temperature, but also a high formation of cracking products, and presents signs of deactivation after 8 h. Though much remains to be done, the performance of these catalysts indicates that there are good perspectives for their industrial application in the isomerization of n-heptane and heavier alkanes. PMID:21760573

Alemán-Vázquez, Laura Olivia; Cano-Domínguez, José Luis; Torres-García, Enelio; Villagómez-Ibarra, José Roberto

2011-01-01

4

The Burning of Large N-Heptane Droplets in Microgravity  

NASA Technical Reports Server (NTRS)

Experimental results are presented on the burning and sooting behavior of large n-heptane droplets in air at atmospheric pressure under microgravity conditions. The experiments were performed at the Japanese Microgravity Center (JAMIC) 10 sec dropshaft in Hokkaido, Japan. Soot volume fraction, burning rate, flame standoff and luminosity were measured for droplets of 2.6 mm and 2.9 mm in initial diameter. These are the largest droplets for which soot volume fraction measurements have ever been performed. Previous measurements of soot volume fractions for n-heptane droplets, confined to smaller droplet sizes of less than 1.8 mm, indicated that maximum soot volume fraction increased monotonically with initial droplet size. The new results demonstrate for the first time that sooting tendency is reduced for large droplets as it has been speculated previously but never confirmed experimentally. The lower soot volume fractions for the larger droplets were also accompanied by higher burning rates. The observed phenomenon is believed to be caused by the dimensional influence on radiative heat losses from the flame. Numerical calculations confirm that soot radiation affects the droplet burning behavior.

Manzello, Samuel L.; Choi, Mun Young; Kazakov, Andrei; Dryer, Frederick L.; Dobashi, Ritsu; Hirano, Toshisuke; Ferkul, Paul (Technical Monitor)

2000-01-01

5

Ethane and n-pentane in exhaled breath are biomarkers of exposure not effect  

PubMed Central

The relationship of exhaled ethane and n-pentane to exhaled NO, carbonylated proteins, and indoor/outdoor atmospheric pollutants were examined in order to evaluate ethane and n-pentane as potential markers of airway inflammation and/or oxidative stress. Exhaled NO and carbonylated proteins were found to have no significant associations with either ethane (p = 0.96 and p = 0.81, respectively) or n-pentane (p = 0.44 and 0.28, respectively) when outliers were included. In the case where outliers were removed n-pentane was found to be inversely associated with carbonylated proteins. Exhaled hydrocarbons adjusted for indoor hydrocarbon concentrations were instead found to be positively associated with air pollutants (NO, NO2 and CO), suggesting pollutant exposure is driving exhaled hydrocarbon concentrations. Given these find-ings, ethane and n-pentane do not appear to be markers of airway inflammation or oxidative stress. PMID:19283520

Gorham, Katrine A.; Sulbaek Andersen, Mads P.; Meinardi, Simone; Delfino, Ralph J.; Staimer, Norbert; Tjoa, Thomas; Rowland, F. Sherwood; Blake, Donald R.

2013-01-01

6

Effects of Equivalence Ratio on Species and Soot Concentrations in Premixed N-Heptane Flames  

E-print Network

octane number. The oxida- tion of n-heptane has been investigated in shock tubes [1, 2], jet quartz microprobe coupled to an online gas chromatography/mass spectrometry (HP 5890 Series II/HP 5972 of n-heptane/oxygen/Ar mixtures behind inci- dent and reflected shock waves for equivalence ratio

Senkan, Selim M.

7

The critical crossover at the n-hexane-water interface  

SciTech Connect

According to estimates of the parameters of the critical crossover in monolayers of long-chain alcohol molecules adsorbed at the n-hexane-water interface, all systems in which this phenomenon is observed are characterized by the same value of the critical exponent {nu} {approx} 1.8.

Tikhonov, A. M., E-mail: tikhonov@kapitza.ras.r [Russian Academy of Sciences, Kapitza Institute for Physical Problems (Russian Federation)

2010-06-15

8

Transition region ignition characteristics of n-heptane fuel sprays  

NASA Technical Reports Server (NTRS)

Ignition studies were perferred on monodisperse n-heptane sprays at atmospheric pressure over a range of equivalence ratios and droplet diameters. A capacitive discharge spark ignition system was used as the ignition source, providing independent control of spark energy and duration. Preliminary measurements were made to optimize spark duration and spark gap, optimum conditions being those at which the maximum frequency or probability of ignition was observed. The effect of spark duration on ignition frequency for several spark energies was determined for equivalence ratios of 0.5 and 1.0 and initial droplet diameters of 28 and 68 microns. Spark duration had little effect on ignition frequency over the entire 15 to 170 mu s range examined. Spark durations of 70 to 80 mu s were used for all subsequent work. The spark gap was optimized at equivalence ratios of 0.6, 0.8 and 1.0 and initial droplet diameters of 30, 40, 50, 60 and 70 microns by varying the electrode spacing from 0.5 to 5.0 mm while maintaining a constant spark energy. The optimum gap was determined to be 3.0 mm for nearly all conditions.

Danis, A. M.; Cernansky, N. P.; Namer, I.

1985-01-01

9

Selective optical detection of n-heptane/iso-octane vapors by polyimide lightguides  

NASA Astrophysics Data System (ADS)

The optical anisotropy of planar polyimide lightguides in an atmosphere of n-heptane / iso-octane is investigated in a transient experiment for pure and several mixed-vapor concentrations. The polymer sensor responds only to n-heptane and not to iso-octane vapors. However, the presence of the latter affects the dynamic behavior of the waveguide anisotropy, which can be fitted by a stretched exponential time dependence. The saturation values of the birefringence are an absolute measure for the n-heptane concentration and are not affected by the presence of the iso-octane vapors.

Podgorsek, R. P.; Franke, H.; Feger, C.

1995-03-01

10

Positron mobilities in isooctane, n-hexane and hexafluorobenzene  

Microsoft Academic Search

Positron mobilities in three nonpolar liquids, isooctane (2, 2, 4-trimethylpentane), n-hexane and hexafluorobenzene, were measured by observing the drift velocity of free positrons in the presence of an external electric field. The Doppler shift of the 511 keV annihilation line was measured as a function of the electric field up to 26 kV cm?1 at room temperature. The free positron

C. L Wang; Y. Kobayashi; K. Hirata

2000-01-01

11

Neuropathy associated with chronic low level exposure to n-hexane  

SciTech Connect

Concentrations of n-hexane greater than the threshold limit value (TLV) of 500 ppm are known to produce peripheral neuropathy. This report describes the case of a worker who developed peripheral neuropathy, with a histologic pattern characteristic of n-hexane toxicity, after chronic on-the-job exposure to n-hexane at concentrations less than 450 ppm. We suggest that the current TLV for n-hexane be reevaluated.

Ruff, R.L.; Petito, C.K.; Acheson, L.S.

1981-05-01

12

Calorimetric study on the state of water and 1-pentanol in the water/1-pentanol/AOT/n-heptane system  

SciTech Connect

Molar enthalpies of solution of 1-pentanol in the AOT/n-heptane system as well as of water in 1-pentanol/n-heptane and in 1-pentanol/AOT/n-heptane systems have been measured at 25/sup 0/C. The results indicate that at infinite dilution, following a Poisson distribution, 1-pentanol molecules distribute between the AOT reversed micelles and the continuous organic phase, whereas at finite concentrations of 1-pentanol, reversed micelles and alcoholic aggregates coexist. It is also found that water added to 1-pentanol/AOT/n-heptane systems is incorporated in both AOT reversed micelles and alcoholic aggregates.

D'Aprano, A.; Lizzio, A.; Liveri, V.T.

1988-04-07

13

In situ high-pressure and high-temperature experiments on n-heptane.  

PubMed

The Raman spectroscopy of n-heptane was investigated in a moissanite anvil cell at ambient temperatures and a diamond anvil cell under pressures of up to ~2000 MPa and at temperature range from 298 to 588 K. The results show that at room temperature the vibration modes, assigned to the symmetric and antisymmetric stretching of CH(3) and CH(2) stretching, shifted to higher frequency according to quasi-linearity with increasing pressure, and a liquid-solid phase transition occurred at near 1150 MPa. The high-temperature solidus line of n-heptane follows a quadratic function of P = 0.00737T(2) + 5.27977T - 1195.76556. Upon phase change, fitting the experimental data obtained in the temperature range of 183?412 K to the Clausius-Clapeyron equation allows one to define the thermodynamic parameters of n-heptane of dP/dT = 0.01474T + 5.27977. PMID:22449288

Qiao, Erwei; Zheng, Haifei; Long, Changxing

2012-02-01

14

A reactive molecular dynamics study of n-heptane pyrolysis at high temperature.  

PubMed

n-Heptane is the most important straight chain paraffin in the fossil-fuel industry. In this work, pyrolysis of n-heptane at high temperature is investigated by a series of ReaxFF based reactive molecular dynamic simulations. The pyrolysis correlated intermediate reactions, important product/intermediate distributions, and corresponding kinetics behaviors are systematically analyzed at atomistic level. The results indicate that the entire pyrolysis process is radical-dominated. The unimolecular dissociation is the main pathway of n-heptane decomposition. Initiation of the decomposition is mainly through C-C bond fission. Central C-C bonds would dissociate prior to the terminal ones. Besides, the Rice-Kossiakoff theory is proved for the pyrolysis of n-heptane at the atomistic level. To give a better description of the pyrolysis behavior, some alkane related intermolecular reactions should be considered in the mechanism. The apparent activation energy extracted from the present simulations is 43.02-54.49 kcal/mol in the temperature range 2400-3000 K, which is reasonably consistent with the experimental results. PMID:23544797

Ding, Junxia; Zhang, Liang; Zhang, Yan; Han, Ke-Li

2013-04-25

15

Catalytic steam cracking of n-heptane with special reference to the effect of calcined dolomite  

SciTech Connect

The catalyzed steam cracking of n-heptane was carried out using a fixed-bed reactor and different, commercially available limestone [CaCO{sub 3}], dolomites [CaMg(CO{sub 3}){sub 2}], and NiMo/{gamma}-Al{sub 2}O{sub 3} as the catalysts. The steam cracking of n-heptane was investigated by variation of water and n-heptane partial pressure and by the additions of hydrogen and carbon dioxide to the water vapor at a total pressure of 101.3 kPa. In the presence of calcined dolomite (1,073 K), the partial pressure of water vapor (p{sub H{sub 2}O} = 9.1 {minus} 34.2 kPa) enhances cracking efficiency, whereas hydrogen (p{sub H{sub 2}} {approx} 33 kPa) and carbon dioxide (CO{sub 2} = 39 vol %), when added to the cracking mixture (973 K), do suppress conversion of n-heptane.

Taralas, G. [National Technical Univ. of Athens (Greece)] [National Technical Univ. of Athens (Greece)

1996-07-01

16

Spray evaporation and dispersion of n -heptane droplets within premixed flame  

Microsoft Academic Search

A detailed numerical simulation of n-heptane droplets was carried out on a stationary three-dimensional configuration with complex geometry. The investigations\\u000a focused on spray evaporation and dispersion within a carrier phase that featured operating conditions similar to those found\\u000a in industrial applications, i.e. elevated pressure and temperature. The simulations were carried out using the Eulerian–Lagrangian\\u000a approach with two-way coupling. There were

Mouldi Chrigui; Ali Zghal; Amsini Sadiki; Johannes Janicka

2010-01-01

17

Volume properties of reverse micellar systems AOT/ n-heptane/DMSO-water  

NASA Astrophysics Data System (ADS)

The volume properties of reverse micellar systems bis(2-ethylhexyl) sulfosuccinate sodium salt/ n-heptane/dimethyl sulfoxide-water are studied via densitometry. The presence of dimethyl sulfoxide and the increase in its amount in a dimethyl sulfoxide-water mixed solvent raise the apparent volume of the polar phase. This increase is also observed when the degree of hydration of the polar core and the temperature are raised.

Sargsyan, A. R.; Shahinyan, G. A.; Markarian, S. A.

2014-05-01

18

Extraction of succinic acid with 1-octanol\\/ n -heptane solutions of mixed tertiary amine  

Microsoft Academic Search

The reactive extraction of succinic acid was carried out by mixed tertiary amine which consisted of tripropylamine (TPA) and trioctylamine (TOA) as the extraction agent in 1-octanol\\/n-heptane diluent. Maximum distribution coefficient was obtained at 8:2 weight ratio of TPA\\/TOA. At this ratio, its extraction efficiency is above 90% at the 3.9 wt.% of succinic acid in aqueous solution. Furthermore, the

Y. K. Hong; W. H. Hong

2000-01-01

19

Distribution of neutral organic compounds between n-heptane and fluorine-containing alcohols.  

PubMed

Partition coefficients for a number of varied compounds were determined for n-heptane-2,2,2-trifluoroethanol and n-heptane-1,1,1,3,3,3-hexafluoro-2-propanol and used to derive a general model for the distribution of neutral compounds in the biphasic systems. The partition coefficient, log K(p), was correlated through the solvation parameter model giving log K(p) = 0.160 + 1.190V + 0.856E - 1.538S - 1.325A - 2.965B for the n-heptane-2,2,2-trifluoroethanol system with a multiple correlation coefficient of 0.988, standard error of the estimate 0.136, and Fischer statistic 599 for 77 compounds. For n-heptane-1,1,1,3,3,3-hexafluoro-2-propanol, the model is log K(p) = -0.225 + 1.161V + 0.720E - 1.357S - 0.577A - 2.819B with a multiple correlation coefficient of 0.982, standard error of the estimate 0.148, and Fischer statistic 421 for 84 compounds. In the models, the solute descriptors are excess molar refraction E, dipolarity/polarizability S, overall hydrogen bond acidity and basicity A and B, respectively, and McGowan's characteristic volume V. Either model is expected to be able to estimate further values of the partition coefficient to about 0.13 log units and is applicable to a wide range of compounds. Applications include the choice of partitioning systems for sample clean-up and countercurrent chromatography and for estimating solute descriptors for water insoluble or reactive compounds. PMID:17266967

Qian, Jing; Poole, Colin F

2007-03-01

20

[Spectroscopic measurement of intermediate free radicals of n-heptane in the combustion reaction].  

PubMed

Using an intensified spectroscopic detector CCD and a chemical shock tube, transient emission spectra of n-heptane during the reaction process of combustion were measured, with exposure time of 6 micros and a spectral range of 200 - 850 nm Experiments were conducted at an ignition temperature of 1 408 K and pressure of 2.0 atmos, with an initial fuel mole fraction of 1.0% and an equivalence ratio of 1.0. Measured emission bands were determined to be produced by OH, CH and C2 free radicals, which reveals that small OH, CH and C2 radicals are important intermediate products in the combustion process of n-heptane. Time-resolved spectra indicate that radical concentrations of OH, CH and C2 reached their peaks sharply; however, CH and C2 reduced and disappeared rapidly while the duration of OH was much longer in the reaction. This work provides experimental data for understanding the microscopic process and validating the mechanism of n-heptane combustion reaction. PMID:22715748

Ye, Bin; Li, Ping; Zhang, Chang-hua; Wang, Li-dong; Tang, Hong-chang; Li, Xiang-yuan

2012-04-01

21

Mechanism Reduction and Generation Using Analysis of Major Fuel Consumption Pathways for n-Heptane in Premixed and Diffusion  

E-print Network

, evolution of intermediates, and formation of major products. Heptane is a primary reference fuel for spark, Y.; Scacchi, G.; Baronnet, F. Studies on the oxidation reactions of n-heptane and isooctane. Can. J

Utah, University of

22

Thermodynamics of solvation of calix[4]arenes in n-hexane  

NASA Astrophysics Data System (ADS)

The solubility of eight calix[4]arenes and crown-calix[4]arenes in n-hexane at five different temperatures was determined by isothermal saturation. The thermodynamic dissolution parameters were calculated. Thermodynamics of solvation in n-hexane was calculated using thermodynamic parameters of sublimation obtained earlier. Thermogravimetric analysis of the bottom phase was carried out to detect crystallosolvates. The stoichiometry of the crystallosolvates formed was ascertained.

Surov, O. V.; Voronova, M. I.; Mamardashvili, N. Zh.; Zakharov, A. G.

2010-11-01

23

Effects of surfactants and salt on Henry's constant of n-hexane.  

PubMed

n-Hexane biological removal is intrinsically limited by its hydrophobic nature and low bioavailability. The addition of surfactants could enhance the transport of volatile organic compounds (VOCs) and change the gas-liquid equilibrium of VOCs. In this paper, the effects of four surfactants, sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), tert-octylphenoxypoly-ethoxyethanol (Triton X-100), polyoxyethylene (20) sorbitan monooleate (Tween 80), and sodium nitrate on apparent Henry's constant of n-hexane in surfactant solutions were investigated. The apparent Henry's constants were significantly reduced when surfactants concentrations exceeded their critical micelle concentrations (cmc's). On a cmc basis, the anionic surfactant SDS was found to have the greatest effect on the apparent Henry's constant with CTAB succeeding, then followed by Triton X-100 and Tween 80. However, the apparent Henry's constant of n-hexane decreased even more rapidly when Triton X-100, a nonionic surfactant, was added than when the ionic surfactant of SDS or CTAB was applied under identical mass concentration and other conditions. These results suggest that Triton X-100 have the biggest solubilization of n-hexane among the four surfactants. Sodium nitrate slightly decreased the apparent Henry's constant of n-hexane in surfactant solutions, and could be considered as a cosolvent in the surfactant-(n-hexane) solution. In addition, the relationship between apparent Henry's constant and surfactant concentration was further developed. PMID:19864062

Yang, Chunping; Chen, Fayuan; Luo, Shenglian; Xie, Gengxin; Zeng, Guangming; Fan, Changzheng

2010-03-15

24

Experimental and modeling investigation of the low-temperature oxidation of n-heptane  

PubMed Central

The low-temperature oxidation of n-heptane, one of the reference species for the octane rating of gasoline, was investigated using a jet-stirred reactor and two methods of analysis: gas chromatography and synchrotron vacuum ultra-violet photo-ionization mass spectrometry (SVUV-PIMS) with direct sampling through a molecular jet. The second method allowed the identification of products, such as molecules with hydroperoxy functions, which are not stable enough to be detected using gas chromatography. Mole fractions of the reactants and reaction products were measured as a function of temperature (500-1100K), at a residence time of 2s, at a pressure of 800 torr (1.06 bar) and at stoichiometric conditions. The fuel was diluted in an inert gas (fuel inlet mole fraction of 0.005). Attention was paid to the formation of reaction products involved in the low temperature oxidation of n-heptane, such as olefins, cyclic ethers, aldehydes, ketones, species with two carbonyl groups (diones) and ketohydroperoxides. Diones and ketohydroperoxides are important intermediates in the low temperature oxidation of n-alkanes but their formation have rarely been reported. Significant amounts of organic acids (acetic and propanoic acids) were also observed at low temperature. The comparison of experimental data and profiles computed using an automatically generated detailed kinetic model is overall satisfactory. A route for the formation of acetic and propanoic acids was proposed. Quantum calculations were performed to refine the consumption routes of ketohydroperoxides towards diones. PMID:23712100

Herbinet, Olivier; Husson, Benoit; Serinyel, Zeynep; Cord, Maximilien; Warth, Valerie; Fournet, Rene; Glaude, Pierre-Alexandre; Sirjean, Baptiste; Battin-Leclerc, Frederique; Wang, Zhandong; Xie, Mingfeng; Cheng, Zhanjun; Qi, Fei

2013-01-01

25

The Cracking of N-Heptane in the Gas Phase State and in the HZSM-5 Zeolite: A Quantum Molecular Dynamics Study  

SciTech Connect

Quantum molecular dynamics is used to investigate the cracking of a representative hydrocarbon of the paraffin family (n-heptane), analyzing the effects of temperature in the fragmentation of n-heptane when this compound is in the gas phase and inside a typical industrial catalyst (zeolite HZSM-5). The hydrocarbon structural and electronic features in the two environments are determined and compared. The results substantiate current views and exhibit the basic aspects in the cracking of n-heptane.

Zaragoza, I P.; Santamaria, Ruben

2002-10-10

26

Rotator Phases of n-Heptane under High Pressure: Raman Scattering and X-ray Diffraction Studies  

SciTech Connect

We performed high-pressure Raman scattering and angle-dispersive synchrotron X-ray diffraction measurements on n-heptane at room temperature. It has been found that n-heptane undergoes a liquid to rotator phase III (R{sub III}) transition at 1.2 GPa and then transforms into another rotator phase R{sub IV} at about 3 GPa. As the pressure reaches 7.5 GPa, a transition from an orientationally disordered R{sub IV} phase to an ordered crystalline state starts and is completed around 14.5 GPa. Our results clearly present the high-pressure phase transition sequence (liquid-R{sub III}-R{sub IV}-crystal) of n-heptane, similar to that of normal alkanes.

C Ma; Q Zhou; F Li; J Hao; J Shu; L Huang; F Huang; Q Cui

2011-12-31

27

Some Recent Observations on the Burning of Isolated N-Heptane and Alcohol Droplets  

NASA Technical Reports Server (NTRS)

In a joint program involving Prof. F.A. Williams of the University of California, San Diego and Dr. V. Nayagam of the National Center for Microgravity Research on Combustion and Fluid Dynamics, the combustion of liquid fuel droplets of n-heptane, n-decane, methanol, methanol-water, ethanol and ethanol-water having initial diameters between about 1 mm and 6 mm continues to be studied. The objectives of the work are to improve fundamental knowledge of droplet combustion dynamics for pure fuels and fuel-water mixtures through microgravity experiments and theoretical analyses. The Princeton contributions to the collaborative program supports the engineering design, data analysis, and data interpretation requirements for the study of initially single component, spherically symmetric, isolated droplet combustion studies through experiments and numerical modeling. The complementary UCSD contributions apply asymptotic theoretical analyses and are described in the published literature and in a companion communication in this conference. The combined program continues to focus on analyses of results obtained from Fiber Supported Droplet Combustion (FSDC) experiments (FSDC-2, STS- 94) conducted with the above fuels in shuttle cabin air and Droplet Combustion Experiment (DCE) data obtained for unsupported and fiber supported droplets of n-heptane in Helium-Oxygen mixtures and cabin air (STS-83, STS-94). The program is preparing for a second DCE experimental mission using methanol/methanol-water as fuels and helium-oxygen-nitrogen environments. DCE-2 is to be conducted aboard the International Space Station. Emphases of recent Princeton work are on the study of simple alcohols (methanol, ethanol) and alcohol/water mixtures as fuels, with time-dependent measurements of drop size, flame-standoff, liquid-phase composition, and finally, extinction. Ground based experiments have included bench-scale studies at Princeton and collaborative experimental studies in the 2.2 second drop tower at NASA-Glenn Research Center.

Dryer, F. L.; Kazakov, A.; Urban, B. D.

2001-01-01

28

Solubilities of solanesol in acetonitrile, ethanol and n-hexane from 285 to 310K  

Microsoft Academic Search

Using a laser monitoring observation technique, we measured the solubilities of solanesol in acetonitrile, ethyl alcohol and\\u000a n-hexane by a synthetic method at temperatures ranging from 285 to 310 K at atmospheric pressure. Empirical equations were\\u000a proposed and the calculated results show good agreement with the experimental solubilities.

Jiang-Chu Liu; Dian-Qing Li; Rong-Qi Zhou; Fei Hao

2007-01-01

29

Comparison of lipase-catalysed esterification in supercritical carbon dioxide and in n-hexane  

Microsoft Academic Search

Summary Oleic acid esterification by ethanol has been performed by an immobilized lipase fromMucor miehei in supercritical carbon dioxide and in n-hexane as solvents. In both media, determination of apparent kinetic constants has been achieved and influence of water content has been shown to be different due to various rates of water solubilities. Stability of the lipase has been proved

A. Marty; W. Chulalaksananukul; J. S. Condoret; R. M. Willemot; G. Durand

1990-01-01

30

Soot formation modelling of n-heptane sprays under diesel engine conditions using the Conditional Moment Closure  

E-print Network

1 Soot formation modelling of n-heptane sprays under diesel engine conditions using the Conditional-volume vessel under diesel engine conditions under different ambient densities (14.8 and 30 kg/m3 ) and ambient that the conditional moment closure approach is a promising framework for soot modelling under Diesel engine conditions

Daraio, Chiara

31

EFFECTS OF EQUIVALENCE RATIO ON SPECIES AND SOOT CONCENTRATIONS IN PREMIXED N-HEPTANE FLAMES. (R828193)  

EPA Science Inventory

The micro-structure of laminar premixed, atmospheric-pressure, fuel-rich flames of n-heptane/oxygen/argon has been studied at two equivalence ratios (C/O = 0.63 and C/O = 0.67). A heated quartz microprobe coupled to an online gas chromatography/mass spectrometry (HP 5890 Serie...

32

Evidence for an Elongation/Reduction/C1-Elimination Pathway in the Biosynthesis of n-Heptane in Xylem of Jeffrey Pine.  

PubMed Central

The biosynthetic pathway to n-heptane was investigated by examining the effect of the [beta]-keto acyl-acyl carrier protein synthase inhibitor (2R,3S)-2,3-epoxy-4-oxo-7E,10E-dodecadienamide (cerulenin), a thiol reagent ([beta]-mercaptoethanol), and an aldehydetrapping reagent (hydroxylamine) on the biosynthesis of n-[14C]heptane and putative intermediates in xylem sections of Jeffrey pine (Pinus jeffreyi Grev.& Balf.) incubated with [14C]acetate. Cerulenin inhibited C18 fatty acid biosynthesis but had relatively little effect on radiolabel incorporation into C8 fatty acyl groups and n-heptane. [beta]-Mercaptoethanol inhibited n-heptane biosynthesis, with a corresponding accumulation of radiolabel into both octanal and 1-octanol, whereas hydroxylamine inhibited both n-heptane and 1-octanol biosynthesis, with radiolabel accumulation in octyl oximes. [14C]Octanal was converted to both n-heptane and 1-octanol when incubated with xylem sections, whereas [14C]1-octanol was converted to octanal and n-heptane in a hydroxylamine-sensitive reaction. These results suggest a pathway for the biosynthesis of n-heptane whereby acetate is polymerized via a typical fatty acid synthase reaction sequence to yield a C8 thioester, which subsequently undergoes a two-electron reduction to generate a free thiol and octanal, the latter of which alternately undergoes an additional, reversible reduction to form 1-octanol or loss of C1 to generate n-heptane. PMID:12226360

Savage, T. J.; Hristova, M. K.; Croteau, R.

1996-01-01

33

An Experimental Study of n-Heptane and JP-7 Extinction Limits in an Opposed Jet Burner  

NASA Technical Reports Server (NTRS)

Propulsion engine combustor design and analysis requires experimentally verified data on the chemical kinetics of fuel. Among the important data is the combustion extinction limit as measured by observed maximum flame strain rate. The extinction limit relates to the ability to maintain a flame in a combustor during operation. Extinction limit data can be obtained for a given fuel by means of a laminar flame experiment using an opposed jet burner (OJB). Laminar extinction limit data can be applied to the turbulent application of a combustor via laminar flamelet modeling. The OJB consists of two axi-symmetric tubes (one for fuel and one for oxidizer), which produce a flat, disk-like counter-flow diffusion flame. This paper presents results of experiments to measure extinction limits for n-heptane and the military specification fuel JP-7, obtained from an OJB. JP-7 is an Air Force-developed fuel that continues to be important in the area of hypersonics. Because of its distinct properties it is currently the hydrocarbon fuel of choice for use in Scramjet engines. This study provides much-desired data for JP-7, for which very little information previously existed. The interest in n-heptane is twofold. First, there has been a significant amount of previous extinction limit study and resulting data with this fuel. Second, n-heptane (C7H16) is a pure substance, and therefore does not vary in composition as does JP-7, which is a mixture of several different hydrocarbons. These two facts allow for a baseline to be established by comparing the new OJB results to those previously taken. Additionally, the data set for n-heptane, which previously existed for mixtures up to 26 mole percent in nitrogen, is completed up to 100% n-heptane. The extinction limit data for the two fuels are compared, and complete experimental results are included.

Convery, Janet L.; Pellett, Gerald L.; O'Brien, Walter F., Jr.; Wilson, Lloyd G.; Williams, John

2005-01-01

34

Conversion of C 8 aromatics and n-pentane over Ga 2 O 3 \\/HZSM-5 mechanically mixed catalysts  

Microsoft Academic Search

Ga2O3\\/HZSM-5 catalysts prepared as intimate physical mixtures of Ga2O3 with HZSM-5 have been studied for the conversion of C8 aromatics and the aromatization of n-pentane. Hydrogen reduction of the mechanical mixture is a necessary step in the formation of an active catalyst and the reduction process has been characterized by IR spectroscopy. Reduced materials exhibit superior activity and selectivity compared

Vladislav Kanazirev; Veselina Mavrodinova; Lubka Kosova; Geoffrey L. Price

1991-01-01

35

Experimental study on the auto-ignition and combustion characteristics in the homogeneous charge compression ignition (HCCI) combustion operation with ethanol\\/ n-heptane blend fuels by port injection  

Microsoft Academic Search

This article investigates the auto-ignition, combustion, and emission characteristics of homogeneous charge compression ignition (HCCI) combustion engines fuelled with n-heptane and ethanol\\/n-heptane blend fuels. The experiments were conducted on a single-cylinder HCCI engine using neat n-heptane, and 10%, 20%, 30%, 40%, and 50% ethanol\\/n-heptane blend fuels (by volume) at a fixed engine speed of 1800r\\/min. The results show that, with

Xingcai Lü; Yuchun Hou; Linlin Zu; Zhen Huang

2006-01-01

36

Enhancements of methane, benzene, and n-pentane by oil and gas fields observed from the DC-3 aircraft campaign: A case study  

NASA Astrophysics Data System (ADS)

Observations in the boundary layer from the 1 June flight in Colorado of the 2012 Deep Convective Clouds and Chemistry campaign shows enhancements of n-pentane, methane, and benzene near oil and gas wells that are not correlated with enhancements in carbon monoxide. To further investigate the source of methane emissions, an i-pentane:n-pentane ratio is compared to surface measurements from the Denver-Julesberg Basin and found to be similar. Measurements of n-pentane, methane, benzene and CO are also shown with proximity to Denver to compare an urban signature with an oil and gas well emissions signature. Elevated n-pentane, methane, and benzene mixing ratios without enhancements in CO from the 1 June flight are considered to be strongly influenced by emissions from oil and natural gas fields located near the sampling locations.

Farris, Carolyn Michelle

37

Batch polymerization of isoprene in n-hexane by n-butyllithium initiation  

E-print Network

28 Preparation of the Reaction and Storage Vessels. 28 Preparation of the Isoprene. Preparation of the n-Hexane. Purity Tests Polymerization Reactions 30 31 31 32 Analytical Procedures. Determining n-Butyllithium Concentrations... step in which these anions attack monomeric units. During the evolution of the polymeric units, there is a noticeable lack of term- ination and transfer reactions resulting in "living" poly- mer. The total reaction presents a complex array of sub...

Porter, Raymond Eugene

2012-06-07

38

Anti-inflammatory Active Compounds from the n-Hexane Extract of Euphorbia hirta  

Microsoft Academic Search

The n-hexane extract of the aerial parts of Euphorbia hirta L. (Euphorbiaceae) and its main triterpenes, ?-amyrin (1), 24-methy- lencycloartenol (2), and ?-sitosterol (3) were evaluated for anti- inflammatory effects in mice. Both the extract and the triterpenes exerted significant and dose-dependent anti-inflammatory activity in the TPA-induced ear model. Some dual and triplet combinations of the triterpenes were tested as

Mariano Martínez-Vázquez; Teresa O. Ramírez Apan; María Eugenia Lazcano; Robert Bye; D. F. México

1999-01-01

39

Inhalation developmental toxicology studies: Teratology study of n-hexane in mice: Final report  

SciTech Connect

Gestational exposure to n-hexane resulted in an increase in the number of resorbed fetuses for exposure groups relative to the control group; however, the increases were not directly correlated to exposure concentration. The differences were statistically significant for the 200-ppM with respect to total intrauterine death (early plus late resorptions), and with respect to late resorptions for the 5000-ppM group. A small, but statistically significant, reduction in female (but not male) fetal body weight relative to the control group was observed at the 5000-ppM exposure level. There were no exposure-related increases in any individual fetal malformation or variation, nor was there any increase in the incidence of combined malformations or variations. Gestational exposure of CD-1 mice to n-hexane vapors appeared to cause a degree of concentration-related developmental toxicity in the absence of overt maternal toxicity, but the test material was not found to be teratogenic. This developmental toxicity was manifested as an increase in the number of resorptions per litter for all exposure levels, and as a decrease in the uterine: extra-gestational weight gain ratio at the 5000-ppM exposure level. Because of the significant increase in the number of resorptions at the 200-ppM exposure level, a no observable effect level (NOEL) for developmental toxicity was not established for exposure of mice to 200, 1000 or 5000-ppM n-hexane vapors. 21 refs., 3 figs., 9 tabs.

Mast, T.J.; Decker, J.R.; Stoney, K.H.; Westerberg, R.B.; Evanoff, J.J.; Rommereim, R.L.; Weigel, R.J.

1988-05-01

40

Inhalation developmental toxicology studies: Teratology study of n-hexane in rats: Final report  

SciTech Connect

The straight chain hydrocarbon, n-hexane, is a volatile, ubiquitous solvent used in industrial, academic, and smaller commercial environments. The significant opportunity for women of child-bearing age to be exposed to this chemical prompted the undertaking of a study to assess the developmental toxicity of n-hexane in an animal model. Timed-pregnant (30 animals per group) and virgin (10 animals per group) Sprague-Dawley rats were exposed to 0 (filtered air), 200, 1000, and 5000 ppM n-hexane (99.9% purity) vapor in inhalation chambers for 20 h/day for a period of 14 consecutive days. Sperm-positive females were exposed for 6 to 19 days of gestation (dg) and virgins were exposed concurrently for 14 consecutive days. The day of sperm detection was designated as 0 dg for mated females. Adult female body weights were monitored prior to, throughout the exposure period, and at sacrifice. Uterine, placental, and fetal body weights were obtained for gravid females at sacrifice. Implants were enumerated and their status recorded as live fetus, early or late resorption, or dead. Live fetuses were sexed and examined for gross, visceral, skeletal, and soft-tissue craniofacial defects. 16 refs., 3 figs., 7 tabs.

Mast, T.J.

1987-12-01

41

Effects of Air-Fuel Ratio on Composition of Hydrocarbon Exhaust from Toluene, Toluene-n Heptane Mixture and Isooctane  

Microsoft Academic Search

This study describes the variations in the chemical composition of the exhaust at various air-fuel ratios when toluene, toluene-n-heptane mixture, and isooctane are used as fuels in a Labeco single cylinder engine. The exhaust products from toluene are divided into three groups: those which decrease as the equivalence ratio is increased: toluene, benzene, methane, and dimethylacetylene; those which increase with

J. S. Ninomiya; A. Golovoy

1969-01-01

42

A Model of Reduced Kinetics for Alkane Oxidation Using Constituents and Species for N-Heptane  

NASA Technical Reports Server (NTRS)

The reduction of elementary or skeletal oxidation kinetics to a subgroup of tractable reactions for inclusion in turbulent combustion codes has been the subject of numerous studies. The skeletal mechanism is obtained from the elementary mechanism by removing from it reactions that are considered negligible for the intent of the specific study considered. As of now, there are many chemical reduction methodologies. A methodology for deriving a reduced kinetic mechanism for alkane oxidation is described and applied to n-heptane. The model is based on partitioning the species of the skeletal kinetic mechanism into lights, defined as those having a carbon number smaller than 3, and heavies, which are the complement of the species ensemble. For modeling purposes, the heavy species are mathematically decomposed into constituents, which are similar but not identical to groups in the group additivity theory. From analysis of the LLNL (Lawrence Livermore National Laboratory) skeletal mechanism in conjunction with CHEMKIN II, it is shown that a similarity variable can be formed such that the appropriately non-dimensionalized global constituent molar density exhibits a self-similar behavior over a very wide range of equivalence ratios, initial pressures and initial temperatures that is of interest for predicting n-heptane oxidation. Furthermore, the oxygen and water molar densities are shown to display a quasi-linear behavior with respect to the similarity variable. The light species ensemble is partitioned into quasi-steady and unsteady species. The reduced model is based on concepts consistent with those of Large Eddy Simulation (LES) in which functional forms are used to replace the small scales eliminated through filtering of the governing equations; in LES, these small scales are unimportant as far as the overwhelming part of dynamic energy is concerned. Here, the scales thought unimportant for recovering the thermodynamic energy are removed. The concept is tested by using tabular information from the LLNL skeletal mechanism in conjunction with CHEMKIN II utilized as surrogate ideal functions replacing the necessary functional forms. The test reveals that the similarity concept is indeed justified and that the combustion temperature is well predicted, but that the ignition time is over-predicted, a fact traced to neglecting a detailed description of the processes leading to the heavies chemical decomposition. To palliate this deficiency, functional modeling is incorporated into this conceptual reduction in addition to the modeling the evolution of the global constituent molar density, the enthalpy evolution of the heavies, the contribution to the reaction rate of the unsteady lights from other light species and from the heavies, the molar density evolution of oxygen and water, and the mole fractions of the quasisteady light species. The model is compact in that there are only nine species-related progress variables. Results are presented showing the performance of the model for predicting the temperature and species evolution. The model reproduces the ignition time over a wide range of equivalence ratios, initial pressure, and initial temperature.

Harstad, Kenneth G.; Bellan, Josette

2011-01-01

43

Some Recent Observations on the Burning of Isolated N-Heptane and Alcohol Droplets  

NASA Technical Reports Server (NTRS)

In a joint program involving Prof F.A. Williams of the University of California, San Diego and Dr. Vedha Nayagam of the National Center for Microgravity Research on Fluid and Combustion, the combustion of liquid fuel droplets having initial diameters between about 1 mm and 6 mm is being studied. The objectives of the work are to improve fundamental knowledge of droplet combustion dynamics through microgravity experiments and theoretical analyses. The Princeton contributions to the collaborative program supports the engineering design, data analysis, and data interpretation requirements for the study of initially single component, spherically symmetric, isolated droplet combustion studies through experiments and numerical modeling. The complementary UCSD contributions apply asymptotic theoretical analyses and are described in the published literature and in a companion communication in this volume. Emphases of the Princeton work are on the study of simple alcohols (methanol, ethanol), alcohol/water mixtures, and pure alkanes (n-heptane, n-decane) as fuels, with time dependent measurements of drop size, flame-stand-off, liquid-phase composition, and finally, extinction. Ground based experiments have included bench-scale studies at Princeton and collaborative experimental studies in the 2.2 and 5.18 second drop towers at NASA-Glenn Research Center. Spacelab studies have included fiber-supported droplet combustion (FSDC) experiments in the Glovebox facility with accompanying numerical analyses. Experiments include FSDC-1, performed on the USML-2 mission in October, 1995 (STS-73) and FSDC-2, on the second flight of the MSL-1 mission in July, 1997 (STS-94).

Dryer, F. L.

1999-01-01

44

Phase equilibria for binary n-alkanenitrile- n-alkane mixtures. III. Vapour-liquid phase equilibria for propanenitrile with C 5?C 8 n-alkanes  

Microsoft Academic Search

Vapour-liquid phase equilibria at 313.15 K for the four mixtures of propanenitrile with n-pentane, n-hexane, n-heptane and n-octane have been determined by the measurement of the total vapour pressure in a static apparatus. All mixtures display azeotropy, with the alkane mole fraction of the azeotrope moving from 0.938 in the C5 mixture to 0.239 for the C8 mixture. The excess

Ian A. McLure; Jose-Luis Arriaga-Colina; David A. Armitage

1997-01-01

45

In vitro antioxidant activity and HPTLC determination of n-hexane extract of Emilia sonchifolia (L.)DC.  

PubMed Central

The free radical scavenging activities of n-hexane extract of the whole plant of Emilia sonchifolia was evaluated by employing various in vitro assay systems like DPPH radical scavenging activity, superoxide radical scavenging activity and hydrogen peroxide scavenging activity with IC50 values 180, 160 and 160 ?g/ml respectively. The results of the study indicate that the n-hexane extract of the whole plant of Emilia sonchifolia possess a significant scavenging effect with increasing concentrations probably due to its antioxidant potential. High performance thin layer chromatography (HPTLC) analysis in the n-hexane extract of Emilia sonchifolia showed the presence of terpenoids which probably may be responsible for the antioxidant activity. Thus, n-hexane extract of Emilia sonchifolia can be used potentially as a bioactive source of natural antioxidants due to the presence of terpenoids in it PMID:24826021

Sophia, D.; Ragavendran, P.; Arulraj, C.; Gopalakrishnan, V. K.

2011-01-01

46

Effects of chronic n-hexane exposure on nervous system-specific and muscle-specific proteins  

Microsoft Academic Search

Two kinds of nervous system-specific and muscle-specific proteins, enolase and S-100 protein, were quantitatively determined in peripheral nerves and skeletal muscles of rats chronically exposed to a neurotoxic solvent — n-hexane. Three groups of animals were exposed to n-hexane vapor at three different solvent concentrations (500 ppm, 1200 ppm, 3000 ppm) for 12 h\\/day, 7 days\\/ week for 16 weeks.

Jian Huang; Kanefusa Kato; Eiji Shibata; Kimiya Sugimura; Naomi Hisanaga; Yuichiro Ono; Yasuhiro Takeuchi I

1989-01-01

47

Combustion characteristics and influential factors of isooctane active-thermal atmosphere combustion assisted by two-stage reaction of n-heptane  

SciTech Connect

This paper presents an experimental study on the isooctane active-thermal atmosphere combustion (ATAC) which is assisted by two-stage reaction of n-heptane. The active-thermal atmosphere is created by low- and high-temperature reactions of n-heptane which is injected at intake port, and isooctane is directly injected into combustion chamber near the top dead center. The effects of isooctane injection timing, active-thermal atmosphere intensity, overall equivalence ratio, and premixed ratio on combustion characteristics and emissions are investigated. The experimental results reveal that, the isooctane ignition and combustion can be classified to thermal atmosphere combustion, active atmosphere combustion, and active-thermal atmosphere combustion respectively according to the extent of n-heptane oxidation as well as effects of isooctane quenching and charge cooling. n-Heptane equivalence ratio, isooctane equivalence ratio and isooctane delivery advance angle are major control parameters. In one combustion cycle, the isooctane ignited and burned after those of n-heptane, and then this combustion phenomenon can also be named as dual-fuel sequential combustion (DFSC). The ignition timing of the overall combustion event is mainly determined by n-heptane equivalence ratio and can be controlled in flexibility by simultaneously adjusting isooctane equivalence ratio. The isooctane ignition regime, overall thermal efficiency, and NO{sub x} emissions show strong sensitivity to the fuel delivery advance angle between 20 CA BTDC and 25 CA BTDC. (author)

Lu, Xingcai; Ji, Libin; Ma, Junjun; Zhou, Xiaoxin; Huang, Zhen [Key Lab. for Power Machinery and Engineering of MOE, Shanghai Jiao Tong University, 200240 Shanghai (China)

2011-02-15

48

Designed catalysts from Pt nanoparticles supported on macroporous oxides for selective isomerization of n-hexane.  

PubMed

Selective isomerization toward branched hydrocarbons is an important catalytic process in oil refining to obtain high-octane gasoline with minimal content of aromatic compounds. Colloidal Pt nanoparticles with controlled sizes of 1.7, 2.7, and 5.5 nm were deposited onto ordered macroporous oxides of SiO2, Al2O3, TiO2, Nb2O5, Ta2O5, and ZrO2 to investigate Pt size- and support-dependent catalytic selectivity in n-hexane isomerization. Among the macroporous oxides, Nb2O5 and Ta2O5 exhibited the highest product selectivity, yielding predominantly branched C6 isomers, including 2- or 3-methylpentane, as desired products of n-hexane isomerization (140 Torr n-hexane and 620 Torr H2 at 360 °C). In situ characterizations including X-ray diffraction and ambient-pressure X-ray photoelectron spectroscopy showed that the crystal structures of the oxides in Pt/oxide catalysts were not changed during the reaction and oxidation states of Nb2O5 were maintained under both H2 and O2 conditions. Fourier transform infrared spectra of pyridine adsorbed on the oxides showed that Lewis sites were the dominant acidic site of the oxides. Macroporous Nb2O5 and Ta2O5 were identified to play key roles in the selective isomerization by charge transfer at Pt-oxide interfaces. The selectivity was revealed to be Pt size-dependent, with improved isomer production as Pt sizes increased from 1.7 to 5.5 nm. When 5.5 nm Pt nanoparticles were supported on Nb2O5 or Ta2O5, the selectivity toward branched C6 isomers was further increased, reaching ca. 97% with a minimum content of benzene, due to the combined effects of the Pt size and the strong metal-support interaction. PMID:24773412

An, Kwangjin; Alayoglu, Selim; Musselwhite, Nathan; Na, Kyungsu; Somorjai, Gabor A

2014-05-14

49

Adsorption of n-hexane and intermediate molecular weight aromatic hydrocarbons on LaY zeolite  

SciTech Connect

Experimental equilibrium isotherms, Henry`s law constants, and heats of sorption are reported for n-hexane, benzene, toluene, p-xylene, mesitylene, naphthalene, trimethylbenzene (TMP), and hexamethylbenzene (HMB) in La-exchanged zeolite Y (Si/Al = 1.8). Henry`s law constants and energies of adsorption are substantially smaller than those for NaX zeolite, reflecting the absence of accessible cations in LaY. These data provide a basis for the estimation of adsorbed phase concentrations of the relevant hydrocarbons on REY cracking catalysts under reaction conditions.

Ruthven, D.M. [Univ. of Maine, Orono, ME (United States). Dept. of Chemical Engineering] [Univ. of Maine, Orono, ME (United States). Dept. of Chemical Engineering; Kaul, B.K. [Exxon Research and Engineering, Florham Park, NJ (United States)] [Exxon Research and Engineering, Florham Park, NJ (United States)

1996-06-01

50

Determination of low concentrations of aromatic hydrocarbons in multicomponent mixtures with iso-octane and n-heptane  

NASA Astrophysics Data System (ADS)

We have experimentally studied the absorption spectra of hydrocarbon mixtures based on n-heptane and isooctane with small (1%-2%) additions of aromatic hydrocarbons (benzene, toluene, xylene). The study was conducted in the region of the first overtones of the vibrational spectra for the hydrocarbon groups CH3, CH2, CH. We show that four-component modeling of the absorption spectrum of the hydrocarbon mixture and minimization of the deviation of the model spectrum from the experimental spectrum allow us to separately determine the content of the aromatic additives for concentrations from 1%.

Vesnin, V. L.; Muradov, V. G.

2011-11-01

51

Reactive extraction of lactic acid with trioctylamine/methylene chloride/n-hexane  

SciTech Connect

The trioctylamine (TOA)/methylene chloride (MC)/n-hexane system was used as the extraction agent for the extraction of lactic acid. Curves of equilibrium and hydration were obtained at various temperatures and concentrations of TOA. A modified mass action model was proposed to interpret the equilibrium and the hydration curves. The reaction mechanism and the corresponding parameters which best represent the equilibrium data were estimated, and the concentration of water in the organic phase was predicted by inserting the parameters into the simple mathematical equation of the modified model. The concentration of MC and the change of temperature were important factors for the extraction and the stripping process. The stripping was performed by a simple distillation which was a combination of temperature-swing regeneration and diluent-swing regeneration. The type of inactive diluent has no influence on the stripping. The stripping efficiencies were about 70%.

Han, D.H.; Hong, W.H. [Korea Advanced Inst. of Science and Technology, Tajeon (Korea, Democratic People`s Republic of)

1996-04-01

52

Solvent blends can control cationic reversed micellar interdroplet interactions. The effect of n-heptane:benzene mixture on BHDC reversed micellar interfacial properties: droplet sizes and micropolarity.  

PubMed

We have investigated, for the first time, the effect of the composition of the nonpolar organic media on the benzyl-n-hexadecyl-dimethylammonium chloride (BHDC) reversed micelles (RMs) properties at fixed temperature. To achieve this goal we have used the solvatochromic behavior of 1-methyl-8-oxyquinolinium betaine (QB) as absorption probe and dynamic light scattering (DLS), to monitor droplet sizes, interfacial micropolarity, and sequestrated water structure of water/BHDC/n-heptane:benzene RMs. DLS results confirm the formation of the water/BHDC/n-heptane:benzene RMs at every n-heptane mole fraction (X(Hp)) investigated, that is, X(Hp) = 0.00, 0.13, 0.21, 0.30, and 0.38. Also, DLS was used to measure the RMs diffusion coefficient and to calculate the apparent droplet hydrodynamic diameter (d(App)) at different compositions of the nonpolar organic medium. The data suggest that as the n-heptane content increases, the interdroplet attractive interactions also increase with the consequent increment in the droplet size. Moreover, the interdroplet attractive interactions can be "switched on (increased)" or "switched off (decreased)" by formulation of appropriate n-heptane:benzene mixtures. Additionally, QB spectroscopy was used to obtain the "operational" critical micellar concentration (cmc) and to investigate both the RMs interfacial micropolarity and the sequestrated water structure in every RMs studied. The results show that BHDC RMs are formed at lower surfactant concentration when n-heptane or water content increases. When the interdroplet interaction "switches on", the RMs droplet sizes growth expelling benzene molecules from the RMs interface, favoring the water-BHDC interaction at the interface with the consequent increases in the interfacial micropolarity. Therefore, changing the solvent blend is possible to affect dramatically the interfacial micropolarity, the droplet sizes and the structure of the entrapped water. PMID:21916486

Agazzi, Federico M; Falcone, R Dario; Silber, Juana J; Correa, N Mariano

2011-10-27

53

A molecular ;phase ordering; phase transition leading to a modulated aperiodic composite in n-heptane/urea  

SciTech Connect

n-Heptane/urea is an aperiodic inclusion compound in which the ratio of host and guest repeats along the channel axis is very close to unity and is found to have a constant value (0.981) from 280 K to 90 K. Below 280 K, two phase transitions are observed. The first (T{sub c1} = 145 K) is a ferroelastic phase transition that generates superstructure reflections for the host while leaving the guest with 1D order. The second (T{sub c2} = 130 K) is a 'phase ordering' transition to a four-dimensional structure (P2{sub 1}11(0{beta}{gamma})) with pronounced host-guest intermodulation and a temperature dependent phase shift between guests in adjacent channels.

Mariette, C.; Huard, M.; Rabiller, P.; Nichols, Shane M.; Ecolivet, C.; Janssen, Ted; Alquist, III, Keith E.; Hollingsworth, Mark D.; Toudic, B. (CNRS-UMR); (Nijmegen); (KSU)

2012-07-11

54

Molecular shape effect on electron transport in fluids: Density and temperature studies in mixtures of n-pentane and neopentane @fa@f)  

Microsoft Academic Search

Electron mobility ?0 in nonpolar and slightly polar (D?0.5 D) hydrocarbon fluids is strongly affected by the external shape of the molecules. The mobility is large in a liquid of spherelike molecules such as neopentane. Addition of rodlike molecules such as n-pentane decreases ?0, but has little effect on the value of the threshold field for electron heating. A liquid

Norman Gee; Gordon R. Freeman

1983-01-01

55

In Vitro Anti-Listerial Activities of Crude n-Hexane and Aqueous Extracts of Garcinia kola (heckel) Seeds  

PubMed Central

We assessed the anti-Listerial activities of crude n-hexane and aqueous extracts of Garcinia kola seeds against a panel of 42 Listeria isolates previously isolated from wastewater effluents in the Eastern Cape Province of South Africa and belonging to Listeria monocytogenes, Listeria grayi and Listeria ivanovii species. The n-hexane fraction was active against 45% of the test bacteria with zones of inhibition ranging between 8–17 mm, while the aqueous fraction was active against 29% with zones of inhibition ranging between 8–11 mm. The minimum inhibitory concentrations (MIC) were within the ranges of 0.079–0.625 mg/mL for the n-hexane extract and 10 to >10 mg/mL for the aqueous extract. The rate of kill experiment carried out for the n-hexane extract only, revealed complete elimination of the initial bacterial population for L. grayi (LAL 15) at 3× and 4× MIC after 90 and 60 min; L. monocytogenes (LAL 8) at 3× and 4× MIC after 60 and 15 min; L. ivanovii (LEL 18) at 3× and 4× MIC after 120 and 15 min; L. ivanovii (LEL 30) at 2, 3 and 4× MIC values after 105, 90 and 15 min exposure time respectively. The rate of kill activities were time- and concentration-dependant and the extract proved to be bactericidal as it achieved a more than 3log10 decrease in viable cell counts after 2 h exposure time for all of the four test organisms at 3× and 4× MIC values. The results therefore show the potential presence of anti-Listerial compounds in Garcinia kola seeds that can be exploited in effective anti-Listerial chemotherapy. PMID:22072929

Penduka, Dambudzo; Okoh, Anthony I.

2011-01-01

56

Analysis of petroleum contaminated soils by spectral modeling and pure response profile recovery of n-hexane.  

PubMed

This pilot study compared penalized spline regression (PSR) and random forest (RF) regression using visible and near-infrared diffuse reflectance spectroscopy (VisNIR DRS) derived spectra of 164 petroleum contaminated soils after two different spectral pretreatments [first derivative (FD) and standard normal variate (SNV) followed by detrending] for rapid quantification of soil petroleum contamination. Additionally, a new analytical approach was proposed for the recovery of the pure spectral and concentration profiles of n-hexane present in the unresolved mixture of petroleum contaminated soils using multivariate curve resolution alternating least squares (MCR-ALS). The PSR model using FD spectra (r(2) = 0.87, RMSE = 0.580 log10 mg kg(-1), and residual prediction deviation = 2.78) outperformed all other models tested. Quantitative results obtained by MCR-ALS for n-hexane in presence of interferences (r(2) = 0.65 and RMSE 0.261 log10 mg kg(-1)) were comparable to those obtained using FD (PSR) model. Furthermore, MCR ALS was able to recover pure spectra of n-hexane. PMID:24686115

Chakraborty, Somsubhra; Weindorf, David C; Li, Bin; Ali, Md Nasim; Majumdar, K; Ray, D P

2014-07-01

57

Combustion of n-heptane in a shock tube and in a stirred reactor: A detailed kinetic modeling study  

SciTech Connect

A detailed chemical kinetic reaction mechanism is used to study the oxidation of n-heptane under several classes of conditions. Experimental results from ignition behind reflected shock waves and in a rapid compression machine were used to develop and validate the reaction mechanism at relatively high temperatures, while data from a continuously stirred tank reactor (cstr) were used to refine the low temperature portions of the reaction mechanism. In addition to the detailed kinetic modeling, a global or lumped kinetic mechanism was used to study the same experimental results. The lumped model was able to identify key reactions and reaction paths that were most sensitive in each experimental regime and provide important guidance for the detailed modeling effort. In each set of experiments, a region of negative temperature coefficient (NTC) was observed. Variation in pressure from 5 to 40 bars were found to change the temperature range over which the NTC region occurred. Both the lumped and detailed kinetic models reproduced the measured results in each type of experiments, including the features of the NTC region, and the specific elementary reactions and reaction paths responsible for this behavior were identified and rate expressions for these reactions were determined.

Gaffuri, P.; Curran, H.J.; Pitz, W.J.; Westbrook, C.K.

1995-04-13

58

OH time-histories during oxidation of n-heptane and methylcyclohexane at high pressures and temperatures  

SciTech Connect

OH concentration time-histories during n-heptane and methylcyclohexane (MCH) oxidation were measured behind reflected shock waves in a heated, high-pressure shock tube. Experimental conditions covered temperatures of 1121 to 1332 K, pressures near 15 atm, and initial fuel concentrations of 750 and 1000 ppm (by volume), and an equivalence ratio of 0.5 with O{sub 2} as the oxidizer and argon as the bath gas. OH concentrations were measured using narrow-linewidth ring-dye laser absorption near the R-branchhead of the OH A-X(0,0) system at 306.47 nm. These current measurements together with our recent results for n-dodecane oxidation [S.S. Vasu, D.F. Davidson, Z. Hong, V. Vasudevan, R.K. Hanson, Proc. Combust. Inst. 32 (2009), doi:10.1016/j.proci.2008.05.006] provide critically needed validation targets for jet fuel surrogate kinetic mechanisms and further improve understanding of high-pressure, high-temperature oxidation chemistry. Detailed comparisons of these OH time-histories with the predictions of various kinetic mechanisms were made. Sensitivity and pathway analyses for these reference fuel components were performed, leading to reaction rate recommendations with improved model performance. Current results are the first quantitative measurements of OH time-histories during high-pressure oxidation of these fuels, and hence are a critical step toward development of accurate reaction models for jet fuel surrogates. (author)

Vasu, Subith S.; Davidson, David F.; Hanson, Ronald K. [Mechanical Engineering Department, Stanford University, Stanford, CA 94305 (United States)

2009-04-15

59

A modelling study of the combustion of n-heptane and iso-octane in a high pressure turbulent flow reactor  

SciTech Connect

The primary reference fuels n-heptane and iso-octane and their mixtures are used as a measure of the tendency of a given automotive fuel to cause knocking or pre-ignition in an internal combustion engine. Consequently, many experimental studies have been performed on these hydrocarbons in an attempt to better understand their oxidation. Shock tube studies at high temperature and pressure have been performed. Low temperature studies, in which species concentration profiles of primary, intermediate and final products, have been carried out using jet stirred flow reactors. In addition, experiments have been performed in CFR engines and fundamental features of n-heptane autoignition have been observed using a rapid compression machine. A detailed chemical kinetic reaction mechanism is employed here to study the oxidation of both fuels. Computed results are compared with experimental data obtained in the High Pressure Turbulent Flow Reactor at Princeton University.

Curran, H.J.; Gaffuri, P.; Pitz, W.J.; Westbrook, C.K. [Lawrence Livermore National Lab., CA (United States); Callahan, C.; Dryer, F.L.; Held, T. [Princeton Univ., NJ (United States)

1995-04-13

60

Simulating self-excited oscillations in the cold-flame combustion of a mixture of n-heptane with isooctane in an ideal-mixing reactor  

SciTech Connect

Measurements have been made on oscillatory states in cold-flame oxidation of a mixture of n-heptane with isooctane in a spherical ideal-mixing reactor. The oscillation characteristics correlate well with the composition, and the method can be combined with others to determine the octane numbers of actual fuels. The authors consider a model giving a qualitative description of cold-flame burning under oscillatory conditions. They examine how these oscillations (period and amplitude vary with different parameters.

Bykov, V.I.; Pushkareva, T.P.; Stepanskii, Ya.Yu.

1987-09-01

61

Calorimetric, Viscosimetric, and Light Scattering Studies of the Aggregation of, and the Solubilization of Water by, Triton X-35 in n-Heptane.  

PubMed

The behavior of a nonionic surfactant TX-35 in solution in n-heptane in the presence and absence of added water has been examined using the microcalorimetric, viscosimetric, and quasielastic light scattering experimental methods. In this paper, we were interested in the aggregation process of the poly(oxyethylene) glycol alkylphenyl ether in n-heptane and in the solubilization of water in the reverse micelle of the surfactant (micellar solubilization). The analysis of the differential molar enthalpies of dilution of TX-35 in dried n-heptane has shown the occurrence of a gradual exothermic aggregation process on a very wide range of concentration which takes place at particular concentration so-called "operational CMC". This operational CMC value has been confirmed by viscosities measurements. The differential molar enthalpies of hydration of TX-35 were also measured and found to be exothermic. The maximal hydration ratio (w0) was found to be equal to 3.2 mol H2O per mole of TX-35 before the point of phase separation. The measurements of the variation of the amount of water contained in TX-35 solutions at different concentrations in n-heptane also show the occurence of a gradual aggregation process and confirm the value of the maximal hydration ratio already determined by microcalorimetry. In the absence of added water, from the quasielastic light scattering experiments, a mean diameter of the aggregates close to 45 Å has been determine, while in the presence of water, a mean diameter of 61 Å was detected and remained unchanged with increasing the hydration ratio indicating that the size of the aggregate is more influenced by the presence of water than by the amount. In the presence of water, it is relevant to discuss aggregates of lamellar or filament shape. Copyright 1999 Academic Press. PMID:9885255

Lagerge; Grimberg-Michaud; Guerfi; Partyka

1999-01-15

62

Thermodiffusion, molecular diffusion and Soret coefficient of binary and ternary mixtures of n-hexane, n-dodecane and toluene.  

PubMed

In this study, the thermodiffusion, molecular diffusion, and Soret coefficients of 12 binary mixtures composed of toluene, n-hexane and n-dodecane in the whole range of concentrations at atmospheric pressure and temperatures of 298.15 K and 308.15 K have been determined. The experimental measurements have been carried out using the Thermogravitational Column, the Sliding Symmetric Tubes and the Thermal Diffusion Forced Rayleigh Scattering techniques. The results obtained using the different techniques show a maximum deviation of 9% for the thermodiffusion coefficient, 8% for the molecular diffusion coefficient and 2% for the Soret coefficient. For the first time we report a decrease of the thermodiffusion coefficient with increasing ratio of the thermal expansion coefficient and viscosity for a binary mixture of an organic ring compound with a short n-alkane. This observation is discussed in terms of interactions between the different components. Additionally, the thermogravitational technique has been used to measure the thermodiffusion coefficients of four ternary mixtures consisting of toluene, n-hexane and n-dodecane at 298.15 K. In order to complete the study, the values obtained for the molecular diffusion coefficient in binary mixtures, and the thermodiffusion coefficient of binary and ternary mixtures have been compared with recently derived correlations. PMID:25376978

Alonso de Mezquia, David; Wang, Zilin; Lapeira, Estela; Klein, Michael; Wiegand, Simone; Mounir Bou-Ali, M

2014-11-01

63

How TOPO affects the interface of the novel mixed water/AOT:TOPO/n-heptane reverse micelles: dynamic light scattering and Fourier transform infrared spectroscopy studies.  

PubMed

In this work we report for the first time the formation of two reverse micelle (RM) media produced by the nonionic surfactant tri-n-octyl phosphine oxide (TOPO) in n-heptane and the one produced by mixing the anionic sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT) with different TOPO contents dissolved in n-heptane. Dynamic light scattering (DLS) experiments reveal the formation of water/TOPO/n-heptane RMs (TOPO RMs) and water/AOT:TOPO/n-heptane RMs (mixed RMs) since the droplet sizes increase as the water content increases. The addition of TOPO to the system at constant W0 (W0 = [water]/([AOT] + [TOPO])) causes the droplet sizes of mixed RMs to decrease compared with the AOT RMs. In addition, the decrease is larger when the water content is low (W0 = 0.5) but the effect is negligible at the maximum W0 value analyzed (W0 = 2). These results are not expected for mixtures of different nonionic surfactants with AOT and were explained considering the unique TOPO structure. Thus, at W0 = 0.5, we suggest that the percentage of TOPO molecules at the mixed RM interface is higher than those corresponding to the bulk solution. On the other hand, at W0 = 2 the RM interface is comprised mainly of AOT molecules. The FT-IR experiments performed by monitoring monodeuterated water frequency (?(OD)) in TOPO RMs show bound and "bulk-like" water structure even at very low water content. On the other hand, for mixed RMs the water structure depends on the water content. At low W0 value, there are two kinds of water molecules, and at W0 value around 2 only bound water exists. The Fourier transform infrared (FT-IR) experiments performed on the symmetric (?(s)SO3) and asymmetric (?(a)SO3) sulfonate stretching bands of AOT reveal the existence of a strong Na(+)?TOPO complex in the mixed RMs. The results show that adding TOPO to form mixed surfactant RMs with AOT reduces their size, changes the nature of water to have a "bulk-like" character and diminishes the ion pairing of the sulfonate group with Na(+). PMID:24947471

Odella, Emmanuel; Falcone, R Darío; Silber, Juana J; Correa, N Mariano

2014-08-01

64

Identification of linoleic acid, a main component of the n-hexane fraction from Dryopteris crassirhizoma, as an anti-Streptococcus mutans biofilm agent.  

PubMed

Dryopteris crassirhizoma is a semi-evergreen plant. Previous studies have shown the potential of this plant as an agent for the control of cariogenic biofilms. In this study, the main antibacterial components of the plant were identified by correlating gas chromatography-mass spectrometry data with the antibacterial activity of chloroform and n-hexane fractions and then evaluating the activity of the most potent antibacterial component against Streptococcus mutans UA159 biofilms. The most potent antibacterial component was linoleic acid, a main component of the n-hexane fraction. Linoleic acid reduced viability in a dose dependent manner and reduced biofilm accumulation during initial and mature biofilm formation. Furthermore, when the biofilms were briefly treated with linoleic acid (10?min/treatment, a total of six times), the dry weight of the biofilms was significantly diminished. In addition, the anti-biofilm activity of the n-hexane fraction was similar to that of linoleic acid. These results suggest that the n-hexane fraction of D. crassirhizoma and linoleic acid may be useful for controlling cariogenic biofilms. PMID:25115514

Jung, Ji-Eun; Pandit, Santosh; Jeon, Jae-Gyu

2014-01-01

65

Supercritical SC-CO(2) and Soxhlet n-Hexane Extract of Tunisian Opuntia ficus indica Seeds and Fatty Acids Analysis.  

PubMed

The fatty acids profiles of Tunisian Opuntia ficus indica seeds (spiny and thornless form) were investigated. Results of supercritical carbon dioxide (SC-CO(2)) and soxhlet n-hexane extract were compared. Quantitatively, the better yield was obtained through soxhlet n-hexane: 10.32% (spiny) and 8.91% (thornless) against 3.4% (spiny) and 1.94% (thornless) by SC-CO(2) extract (T?=?40°C, P = 180 bar, time?=?135?mn, CO(2) flow rate?=?15?mL·s(-1)). Qualitatively, the main fatty acids components were the same for the two types of extraction. Linoleic acid was the major compound, SC-CO(2):?57.60% (spiny), 59.98% (thornless), soxhlet n-hexane: 57.54% (spiny), 60.66% (thornless), followed by oleic acid, SC-CO(2):?22.31% (spiny), 22.40% (thornless), soxhlet n-hexane: 25.28% (spiny), 20.58% (thornless) and palmitic acid, SC-CO(2):?14.3% (spiny), 12.92% (thornless), soxhlet n-hexane: 11.33% (spiny), 13.08% (thornless). The SC-CO(2) profiles fatty acids showed a richness with other minority compounds such as C(20:1), C(20:2), and C(22).The seeds oil was highly unsaturated (US?=?4.44-5.25), and the rising temperatures donot affect the selectivity of fatty acids extract by SC-CO2: US?=?4.44 (T?=?40°C) and 4.13 (T?=?70°C). PMID:22754699

Yeddes, Nizar; Chérif, Jamila Kalthoum; Jrad, Amel; Barth, Danielle; Trabelsi-Ayadi, Malika

2012-01-01

66

A detailed chemical kinetic reaction mechanism for the oxidation of iso-octane and n-heptane over an extended temperature range and its application to analysis of engine knock  

Microsoft Academic Search

A detailed chemical kinetic reaction is developed to describe the oxidation of n-heptane, iso-octane, and their mixtures over a wide range of operating conditions. In addition to a high temperature submechanism, reaction paths are included to describe the lower temperature regimes in which the rate and intermediate products of oxidation are controlled by addition of molecular oxygen to alkyl and

C. K. Westbrook; J. Warnatz; W. J. Pitz

1988-01-01

67

The effect of varying oven temperatures and residence times on thermal desorption of n-hexane and 1-hexene from diffusive organic vapor dosimeters  

E-print Network

THE EFFECT OF VARYING OVEN TEMPERATURES AND RES IDENCE TIMES ON THERMAL DESORPTION OF N-HEXANE AND 1-HEXENE FROM DIFFUSIVE ORGANIC VAPOR DOS IMETERS A Thesis bv KENNETH GARNETT STEELE Submitted to the Graduate College of Texas ARiM University... ORGANIC VAPOR DOSIMETERS A Thesis by KENNETH GARNETT STEELE Approved as to style and content by: (Cha' of C4 ttee) (Member ) ( e ) (He d f Departm ) December 1981 4804863 ABSTRACT The Effect of Varying Oven Temperatures and Residence Times...

Steele, Kenneth Garnett

2012-06-07

68

1Butyl oleate synthesis by immobilized lipase from Rhizopus oryzae: a comparative study between n-hexane and solvent-free system  

Microsoft Academic Search

Crude Rhizopus oryzae lipase was immobilized on different supports. The CaCO3 was selected as the most suitable adsorbent preserving the catalytic activity almost intact and offering maximum adsorption capacity. Immobilization enhanced the thermo-stability of lipase. Enzymatic esterification between oleic acid and butanol at 37°C with shaking (200rpm) was realized in two systems: n-hexane and solvent-free system. The product of this

Hanen Ghamgui; Maha Karra-Chaâbouni; Youssef Gargouri

2004-01-01

69

Antiproliferative property of n-hexane and chloroform extracts of Anisomeles malabarica (L). R. Br. in HPV16-positive human cervical cancer cells  

PubMed Central

Objectives: To find the efficacy of serial extracts of Anisomeles malabarica in inhibiting proliferation of and inducing apoptosis in human cervical cancer cells, SiHa and ME 180, that are HPV 16-positive. Materials and Methods: The whole plant was extracted in n-hexane, chloroform, ethyl acetate, n-butanol, methanol, and water. The cells were treated with the extracts at increasing concentrations to find the IC50, adopting MTT ([3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide]) assay. Acridine orange (AO) and ethidium bromide (EB) and Hoechst 33258 staining were adopted to assess the mode of cell death, Annexin V-Cy3 staining to evaluate one of the early apoptotic features, JC-1 staining to assess the mitochondrial membrane depolarization, comet assay for DNA fragmentation, and cell cycle analysis for the distribution of cells after treatment. Results: n-Hexane and chloroform extracts were cytotoxic to the cervical cancer cells in dose- and duration-dependent manner. The cells that responded to the treatments revealed typical apoptotic features. Early features of apoptosis, phosphatidyl serine translocation and loss of mitochondrial trans-membrane potential, were observed in the treated cells, and comet assay revealed DNA damage. In the FACS analysis, the cells accumulated in the sub-G0/G1 phase of the cell cycle, except in n-hexane- and chloroform extract–treated SiHa cells at 24 h, which showed arrest in S- and G2/M phases. Conclusions: n-Hexane and chloroform extracts of A. malabarica inhibit proliferation of and induce death in HPV16-positive cervical cancer cells, mostly by apoptosis and to some extent by necrosis. PMID:22368413

Preethy, Christo Paul; Padmapriya, Ramamoorthy; Periasamy, Vaiyapuri Subbarayan; Riyasdeen, Anvarbatcha; Srinag, Suresh; Krishnamurthy, Hanumanthappa; Alshatwi, Ali Abdullah; Akbarsha, Mohammad Abdulkader

2012-01-01

70

In situ {sup 13}C MAS NMR study of n-hexane conversion on Pt and Pd supported on basic materials  

SciTech Connect

n-Hexane conversion was studied in situ on Pt and Pd supported on aluminum-stabilized magnesium oxide and Pt on Zeolite KL catalysts (Pt/Mg(Al)O, Pd/Mg(Al)O and Pt/KL) by means of {sup 13}C MAS NMR spectroscopy. n-Hexane 1-{sup 13}C was used as a labelled reactant. Forty NMR lines corresponding to 14 different products were resolved and identified. The NMR line assignments were confirmed by adsorption of model compounds. The NMR results were further quantified and compared with continuous flow microreactor tests. Four parallel reaction pathways were identified under flow conditions: isomerization, cracking, dehydrocyclization, and dehydrogenation. Aromatization occurs via two reaction routes: (1) n-hexane dehydrogenation towards hexadienes and hexatrienes, followed by dehydrogenation of a cyclic intermediate. The former reaction pathway is prevented under NMR batch conditions. High pressures induced in the NMR cells at high reaction temperatures (573, 653 K) shift the reaction equilibrium towards hydrogenation. NMR experiments showed that on Pt catalysts aromatization occurs via a cyclohexane intermediate, whereas on Pd it takes place via methylcyclopentane ring enlargement. 54 refs., 15 figs., 3 tabs.

Ivanova, I.I.; Pasau-Claerbout, A.; Seivert, M.; Derouane, E.G. [Facultes Universitaires N.D. de la Paix, Namur (Belgium)] [and others] [Facultes Universitaires N.D. de la Paix, Namur (Belgium); and others

1996-02-01

71

Antihyperglycemic and antihyperlipidemic effects of n-hexane fraction from the hydro-methanolic extract of sepals of Salmalia malabarica in streptozotocin-induced diabetic rats.  

PubMed

Bio-efficacy of n-hexane fraction of sepal of Salmalia malabarica was evaluated covering the biochemical sensors for the management of hyperglycemic and hyperlipidemic effects. Evaluation of n-hexane fraction of Salmalia malabarica (SMH) from hydro-methanolic (2:3) extract at the dose of 0.1 gm/kg body weight twice a day were investigated in normal and streptozotocin (STZ) induced diabetic rats. Normal and STZ-induced diabetic rats were divided into five groups. The effect of the fraction on fasting blood glucose (FBG), serum insulin, hemoglobin, glycated hemoglobin, total cholesterol (TC), triglyceride (TG), high density lipoprotein cholesterol (HDLc), low density lipoprotein cholesterol (LDLc), very low density lipoprotein cholesterol (VLDLc), phospholipids, free fatty acids, urea, uric acid, creatinine, albumin and transaminases were investigated in STZ-induced diabetic rat. A significant reduction of FBG level was observed after SMH treatment in STZ-induced diabetic rat. Treatment of diabetic rats with n-hexane fraction of this plant restored the levels of the above biochemical sensors significantly (p<0.001) in respect to the control. Histological studies of pancreas showed a qualitative diminution in the area of the islet's of Langerhans in diabetic group which was recovered by said fraction. Phytochemical screening of the fraction revealed the presence of flavonoids, terpenoids and steroids. PMID:22732718

De, Debasis; Ali, Kazi Monjur; Chatterjee, Kausik; Bera, Tushar Kanti; Ghosh, Debidas

2012-01-01

72

Rate constant for OH with selected large alkanes : shock-tube measurements and an improved group scheme.  

SciTech Connect

High-temperature rate constant experiments on OH with the five large (C{sub 5}-C{sub 8}) saturated hydrocarbons n-heptane, 2,2,3,3-tetramethylbutane (2,2,3,3-TMB), n-pentane, n-hexane, and 2,3-dimethylbutane (2,3-DMB) were performed with the reflected-shock-tube technique using multipass absorption spectrometric detection of OH radicals at 308 nm. Single-point determinations at {approx}1200 K on n-heptane, 2,2,3,3-TMB, n-hexane, and 2,3-DMB were previously reported by Cohen and co-workers; however, the present work substantially extends the database to both lower and higher temperature. The present experiments span a wide temperature range, 789-1308 K, and represent the first direct measurements of rate constants at T > 800 K for n-pentane. The present work utilized 48 optical passes corresponding to a total path length of {approx}4.2 m. As a result of this increased path length, the high OH concentration detection sensitivity permitted pseudo-first-order analyses for unambiguously measuring rate constants.

Sivaramakrishnan, R.; Michael, J. V.; Chemical Sciences and Engineering Division

2009-04-06

73

Benchmark thermochemistry of the C_nH_{2n+2} alkane isomers (n=2--8) and performance of DFT and composite ab initio methods for dispersion-driven isomeric equilibria  

E-print Network

The thermochemistry of linear and branched alkanes with up to eight carbons has been reexamined by means of W4, W3.2lite and W1h theories. `Quasi-W4' atomization energies have been obtained via isodesmic and hypohomodesmotic reactions. Our best atomization energies at 0 K (in kcal/mol) are: 1220.04 n-butane, 1497.01 n-pentane, 1774.15 n-hexane, 2051.17 n-heptane, 2328.30 n-octane, 1221.73 isobutane, 1498.27 isopentane, 1501.01 neopentane, 1775.22 isohexane, 1774.61 3-methylpentane, 1775.67 diisopropyl, 1777.27 neohexane, 2052.43 isoheptane, 2054.41 neoheptane, 2330.67 isooctane, and 2330.81 hexamethylethane. Our best estimates for $\\Delta H^\\circ_{f,298K}$ are: -30.00 n-butane, -34.84 n-pentane, -39.84 n-hexane, -44.74 n-heptane, -49.71 n-octane, -32.01 isobutane, -36.49 isopentane, -39.69 neopentane, -41.42 isohexane, -40.72 3-methylpentane, -42.08 diisopropyl, -43.77 neohexane, -46.43 isoheptane, -48.84 neoheptane, -53.29 isooctane, and -53.68 hexamethylethane. These are in excellent agreement (typically be...

Karton, Amir; Martin, Jan M L

2009-01-01

74

Electric percolation of water-in-oil microemulsions: The application of effective medium theory to system sodium dodecylbenzenesulfonate (DDBS)/n-pentanol/n-heptane/water  

SciTech Connect

The electric conductive behavior of the system water/sodium dodecylbenzenesulfonate (DDBS)/n-pentanol/n-heptane has been studied. The results showed that the system has an intrinsic electric percolation phenomenon. The water induced percolation threshold, {phi}{sub d}{sup p}, varies over a wide range and is higher than the theoretically predicted value of below 1/3. To use the changed form of the effective medium theory, a second-order polynomial relationship between {sigma}{phi}{sub d} and the conductivity {sigma} of system, is much better than to use the plot of {sigma} versus {phi}{sub d} in fitting the conductivity data of W/O microemulsion, where {phi}{sub d} is the volume fraction of the disperse phase. A linear equation exists when the volume fraction {phi}{sub d} of the disperse phase does not exceed percolation threshold {phi}{sub d}{sup p} much more. The content P of n-pentanol and DDBS affects the properties of the system significantly, but the influences on the limit conductivity of the disperse phase and that of the continuous phase are in the same tendency; also the distribution of alcohol among inner water core, surfactant shell, and continuous phase are changed.

Gu, G.; Wang, W.; Yan, H. [Peking Univ., Beijing (China). Technical Physics Dept.] [Peking Univ., Beijing (China). Technical Physics Dept.

1996-03-01

75

Antifungal and herbicidal properties of essential oils and n-hexane extracts of Achillea gypsicola Hub-Mor. and Achillea biebersteinii Afan. (Asteraceae)  

Microsoft Academic Search

The chemical composition of essential oils isolated by hydrodistillation from the aerial parts of Achillea gypsicola Hub-Mor., Achillea biebersteinii Afan. and n-hexane extracts obtained from the flowers of A. gypsicola and A. biebersteinii Afan. was analyzed by GC and GC–MS. Camphor (40.17–23.56%, respectively), 1,8-cineole (22.01–38.09%, respectively), piperitone (11.29–0.37%, respectively), borneol (9.50–5.88%, respectively) and ?-terpineol (1.56–5.15%, respectively) were found to be

Saban Kordali; Ahmet Cakir; Tulay Aytas Akcin; Ebru Mete; Adnan Akcin; Tuba Aydin; Hamdullah Kilic

2009-01-01

76

Absolute cross section for trapping low-energy electrons (0-18 eV) in molecular films of n-hexane  

NASA Astrophysics Data System (ADS)

We propose an apparatus and method, based on the absorption of photon of energy ranging between 1.5 and 3.54eV, to measure the absolute cross section for trapping low-energy electrons in a molecular film deposited on a metal substrate. A simple model is described to analyze electron trapping in the film and charge release from the same film by photon excitation. Measurements of the trapping of electrons in multilayer films of n-hexane are presented for different film thicknesses, electron exposures and incident energies, and probing photon fluxes and energies. The electron trapping cross section in a five-layer film of n-hexane is characterized by a large maximum reaching a value of (4.7±0.4)×10-17cm2 at 10eV and having a 2.3eV full width at half maximum. This feature is ascribed to the formation of one or several core-excited resonances lying between 7 and 14eV and leading, via dissociative electron attachment, to the formation of stable H- fragments, which stabilize within the first outerlayer of the film.

Michaud, M.; Hébert, E. M.; Cloutier, P.; Sanche, L.

2006-10-01

77

NMR and Molecular Dynamics Study of the Size, Shape, and Composition of Reverse Micelles in a Cetyltrimethylammonium Bromide (CTAB)/n-Hexane/Pentanol/Water Microemulsion.  

PubMed

The size, shape, and composition of reverse micelles (RMs) in a cetyltrimethylammonium bromide (CTAB)/pentanol/n-hexane/water microemulsion were investigated using pulsed gradient stimulated echo (PGSTE) nuclear magnetic resonance (NMR) measurements and molecular modeling. PGSTE data were collected at observation times (?) of 10, 40, and 450 ms. At long observation times, CTAB and pentanol exhibited single diffusion coefficients. However, at short (? ? 40 ms) observation times both CTAB and pentanol exhibited slow and fast diffusion coefficients. These NMR data indicate that both CTAB and pentanol molecules reside in different environments within the microemulsion and that there is exchange between regions on the millisecond time scale. Molecular dynamic simulations of the CTAB RM, in a solvent box containing n-hexane and pentanol, produced an ellipsoid shaped RM. Using structural parameters from these simulations and the Stokes-Einstein relation, the structure factor and dimensions of the reverse micelle were determined. Analysis of the composition of the interphase also showed that there was a variation in the ratio of surfactant to cosurfactant molecules depending on the curvature of the interphase. PMID:25134815

Mills, Amanda J; Wilkie, John; Britton, Melanie M

2014-09-11

78

Removal of saturated aliphatic hydrocarbons (gasoline components) from air via bacterial biofiltration.  

PubMed

Two-stage biofilters (using perlite and granular activated carbon, GAC, as packing materials) were used for the removal of several linear, branched, and cyclic C(5)-C(8)saturated aliphatic hydrocarbons from air, both as individual chemicals and in mixtures. The acclimation of biofilters from styrene to n-heptane was complete in 14-18 days. The substrate switch resulted in significant changes in pH and microbial composition of biofilters. Subsequent experiments were conducted under steady state conditions at a constant EBRT of 123 s and near-neutral pH, assuring the predominantly bacterial (as opposed to fungal) biofilter population. n-Heptane was removed with consistently high, 87-100%, removal efficiencies (RE) for up to 16 g x m(-3) x h(-1) critical substrate loads in the perlite biofilter, while n-hexane and n-pentane exhibited significantly lower RE under similar conditions. The REs for iso-octane and cyclohexane were less than 10% under similar loads; n-heptane biodegradation was consistently ca. 10% lower in the presence of iso-octane than in its absence. The GAC biofilter showed a significantly lower efficiency than the perlite biofilter (the critical load, yielding RE > 90%, was only 5 g x m(-3) x h(-1) for n-heptane). Evidence obtained indicates that the rate limiting step for mixed culture biofiltration of aliphatic hydrocarbon mixtures is biodegradation rather than mass transfer. PMID:20560085

Paca, Jan; Halecky, Martin; Vanek, Tomas; Kozliak, Evguenii; Jones, Kim

2010-01-01

79

Separation of n-hexane/acetone mixtures by pervaporation using high density polyethylene/ethylene propylene diene terpolymer rubber blend membranes.  

PubMed

Polymer membranes were prepared by blending high density polyethylene (HDPE) with ethylene propylene diene terpolymer rubber (EPDM). These blend membranes were evaluated for the selective separation of n-hexane from acetone. The flux and selectivity of the membranes were determined both as a function of the blend composition and feed mixture composition. Results showed that polymer blending method could be very useful to develop new membranes with improved selectivity. Pervaporation properties could be optimized by adjusting the blend composition. The effects of blend ratio, feed composition, and penetrant size on the pervaporation process were analyzed. The permeation properties have been explained on the basis of interaction between the membrane and solvents and blend morphology. Flux increases with increasing alkane content in the feed composition. PMID:22118848

Kumar, P V Anil; Anilkumar, S; Varughese, K T; Thomas, Sabu

2012-01-15

80

Bis[3?,7?,12?-tris-(4-nitro-benzo-yloxy)-5?-cholan-24-yl] disulfide-ethyl acetate-n-hexane (4/4/1)  

PubMed Central

The crystal structure of the title compound, C90H100N6O24S2·C4H8O2·0.25C6H14, solved and refined against synchrotron diffraction data, contains two formula units in the asymmetric unit with the all-trans n-hexane mol­ecule having half-occupancy and one of the ethyl acetate mol­ecules disordered over two positions. The two symmetry-independent disulfide mol­ecules are assembled by approximate face-to-face and face-to-edge inter­actions between their 4-nitro­benzo­yloxy groups into an inter­twined dimer having a double-helix-type structure. The centrally placed disulfide bridges in the two symmetry-independent mol­ecules exhibit different helicity as shown by the C—S—S—C torsion angles of 71.0?(1) and ?92.5?(1)°. PMID:21522786

Brzezinski, Krzysztof; Tomkiel, Aneta M.; Lotowski, Zenon; Morzycki, Jacek; Dauter, Zbigniew

2011-01-01

81

Activity, Selectivity, and Sulfur Resistance of Pt\\/WO x –ZrO 2 and Pt\\/Beta Catalysts for the Simultaneous Hydroisomerization of n-Heptane and Hydrogenation of Benzene  

Microsoft Academic Search

Bifunctional Pt\\/WOx–ZrO2 (Pt\\/WZr, 12.7 wt% W) and Pt\\/Beta (Si\\/Al=12) catalysts have been studied for the simultaneous n-alkane hydroisomerization and aromatic hydrogenation using a n-heptane\\/benzene feed mixture (25 wt% benzene) at 3.0 MPa and temperatures in the 473–573 K range. The catalysts were characterized by X-ray diffraction, adsorption–desorption of N2, laser Raman spectroscopy (for WZr), temperature-programmed desorption (TPD) of NH3, CO

M. A. Arribas; F. Márquez

2000-01-01

82

N,N'-(Hexane-1,6-diyl)bis(4-methyl-N-(oxiran-2-ylmethyl)benzenesulfonamide): Synthesis via cyclodextrin mediated N-alkylation in aqueous solution and further Prilezhaev epoxidation  

PubMed Central

Summary N-alkylation of N,N'-(hexane-1,6-diyl)bis(4-methylbenzenesulfonamide) with allyl bromide and subsequent Prilezhaev reaction with m-chloroperbenzoic acid to give N,N'-(hexane-1,6-diyl)bis(4-methyl-N-(oxiran-2-ylmethyl)benzenesulfonamide) is described. This twofold alkylation was performed in aqueous solution, whereby ?-, and randomly methylated ?-cyclodextrin were used as adequate phase transfer catalysts and the cyclodextrin–guest complexes were characterized by 1H NMR and 2D NMR ROESY spectroscopy. Finally, the curing properties of the diepoxide with lysine-based ?-amino-?-caprolactam were analyzed by rheological measurements. PMID:24367447

Fischer, Julian; Millan, Simon

2013-01-01

83

40 CFR Appendix A to Part 439 - Tables  

Code of Federal Regulations, 2010 CFR

... Isopropanol 1 Methanol 1 Phenol Isobutyraldehyde 1 Aldehydes. n-Heptane 1 Alkanes. n-Hexane 1 Diethylamine...Treatability class Benzene Toluene 1 Xylenes n-Heptane High strippability. Chloroform 1 Methylene chloride 1...

2010-07-01

84

Probing mechanisms of axonopathy. Part II: Protein targets of 2,5-hexanedione, the neurotoxic metabolite of the aliphatic solvent n-hexane.  

PubMed

Neuroprotein changes in the spinal cord of rodents with aliphatic gamma-diketone axonopathy induced by 2,5-hexanedione (2,5-HD) are compared with those reported previously in aromatic gamma-diketone-like axonopathy induced by 1,2-diacetylbenzene (1,2-DAB). Sprague-Dawley rats were treated intraperitoneally with 500 mg/kg/day 2,5-HD, equimolar doses of 2,3-hexanedione (negative control), or an equivalent amount of saline containing 50% dimethyl sulfoxide (vehicle), 5 days a week, for 3 weeks. Analysis of the lumbosacral proteome by 2-dimensional differential in-gel electrophoresis and matrix-assisted laser desorption ionization time-of-flight/tandem mass spectrometry revealed 34 proteins markedly modified by 2,5-HD of which neurofilament triplet L, gelsolin, protein disulfide isomerase, glutathione S-transferase, nicotinamide adenine dinucleotide (reduced) dehydrogenase 1 alpha, pyruvate kinase, and fatty acid synthase were also modified by 1,2-DAB. The expression of proteins involved in maintaining the physical integrity of the cytoskeleton or controlling the redox and protein-folding mechanisms was reduced, whereas that of proteins supporting energy metabolism was mainly increased. The similarity of the neuroproteomic patterns of 2,5-HD and 1,2-DAB axonopathy suggests common biomarkers and/or mechanisms of neurotoxicity associated with exposure to their parent chemicals, namely the industrial solvents n-hexane and 1,2-diethylbenzene, respectively. PMID:19033394

Tshala-Katumbay, Desire; Monterroso, Victor; Kayton, Robert; Lasarev, Michael; Sabri, Mohammad; Spencer, Peter

2009-02-01

85

Simulation of the toxicokinetics of trichloroethylene, methylene chloride, styrene and n-hexane by a toxicokinetics/toxicodynamics model using experimental data.  

PubMed

The toxicokinetics/toxicodynamics (TKTD) model simulates the toxicokinetics of a chemical based on physiological data such as blood flow, tissue partition coefficients and metabolism. In this study, Andersen and Clewell's TKTD model was used with seven compartments and ten differential equations for calculating chemical balances in the compartments (Andersen and Clewell 1996, Workshop on physiologically-based pharmacokinetic/pharmacodynamic modeling and risk assessment, Aug. 5-16 at Colorado State University, U.S.A) . Using this model, the authors attempted to simulate the behavior of four chemicals: trichloroethylene, methylene chloride, styrene and n-hexane, and the results were evaluated. Simulations of the behavior of trichloroethylene taken in via inhalation and oral exposure routes were also done. The differences between simulations and measurements are due to the differences between the absorption rates of the exposure routes. By changing the absorption rates, the simulation showed agreement with the measured values. The simulations of the other three chemicals showed good results. Thus, this model is useful for simulating the behavior of chemicals for preliminary toxicity assessment. PMID:15793558

Nakayama, Yumiko; Kishida, Fumio; Nakatsuka, Iwao; Matsuo, Masatoshi

2005-01-01

86

Pattern of neurotoxicity of n?hexane, methyl n?butyl ketone, 2,5?hexanediol, and 2,5?hexanedione alone and in combination with O?ethyl O?4?nitrophenyl phenylphosphonothioate in hens  

Microsoft Academic Search

This investigation was designed to study the neurotoxicity produced in hens by the aliphatic hexacarbons n?hexane, methyl n?butyl ketone (MnBK), 2,5?hexanediol (2,5?HDOH), and 2,5?hexanedione (2,5?HD) following daily dermal application of each chemical alone and in combination with O?ethyl O?4?nitrophenyl phenylphosphonothioote (EPN). Dermal application was carried out on the unprotected back of the neck. To assess whether the joint neurotoxic action

H. M. Makkawy; Gerald M. Campbell

1985-01-01

87

Pattern of neurotoxicity of n-hexane, methyl n-butyl ketone, 2,5-hexanediol, and 2,5-hexanedione alone and in combination with O-ethyl O-4-nitrophenyl phenylphosphonothioate in hens  

SciTech Connect

This investigation was designed to study the neurotoxicity produced in hens by the aliphatic hexacarbons n-hexane, methyl n-butyl ketone (MnBK), 2,5-hexanediol (2,5-HDOH), and 2,5-hexanedione (2,5-HD) following daily dermal application of each chemical alone and in combination with O-ethyl O-4-nitrophenyl phenylphosphonothioate (EPN). Dermal application was carried out on the unprotected back of the neck. To assess whether the joint neurotoxic action of various chemicals is caused by the enhancement of absorption through the skin or by interaction at the molecular level, two additional experiments were performed. Dermal application was carried out for 90 d followed by a 30-d observation period. The results show that (1) hens treated with EPN developed severe ataxia followed by improvement during the observation period; (2) n-hexane produced leg weakness with subsequent recovery, whereas the same dose of MnBK, 2,5-HDOH, or 2,5-HD produced clinical signs of neurotoxicity characterized by gross ataxia; (3) concurrent dermal application of EPN with n-hexane of 2,5-HDOH at the same site or at different sites produced an additive neurotoxic action; (4) simultaneous dermal application of EPN and MnBK at different sites resulted in an additive effect, whereas it caused potentiation when applied at the same site; and (5) concurrent topical application of EPN and 2,5-HD produced a potentiating neurotoxic effect. While no histopathologic lesion was produced at the end of the observation period when any test chemical was applied alone, binary treatments of EPN and aliphatic hexacarbons resulted in histopathologic changes in some hens, with morphology and distribution characteristic of EPN neurotoxicity. The mechanism of this joint action seems to be related both to enhancing skin absorption of EPN and/or to its metabolic activation by n-hexane and its related chemicals.

Abou-Donia, M.B.; Makkawy, H.M.; Campbell, G.M.

1985-01-01

88

Calorimetric investigation of the solubilization of water-in-sodium dodecylbenzenesulfonate reversed micelles and water-in-oil microemulsions in mixed solvent of n-heptane and n-pentanol  

SciTech Connect

Thermal behavior of sodium dodecylbenzenesulfonate (DDBS) reversed micelles with n-pentanol and n-heptane as mixed apolar solvents was studied by titrating water into anhydrous reversed micelles with a Tronac model 450 calorimeter. The solubilization of water can be described in terms of deformation of molecular structure of water, adsorption of water, ionization of surfactant, dilution of counterions, and swelling of droplets. A specific radius of anhydrous reversed micelles, R[sub s] = (1 + [radical]6/2)r[sub 0], relating to a transition from exothermic type to endothermic type is proposed, where r[sub 0] is the molecular radius of water. The partial molar enthalpy of water against R, the molar ratio of water to surfactant, shows an exothermic type with one peak at low P and two peaks at high P, where P is the mass percentages of DDBS and n-pentanol in the mixture. Structural parameters of the droplet, such as radii of the disperse phase (R[sub d]) and the water core (R[sub w]), as well as the average aggregation number (N) and the compact effective head group area (a[sub s] + Ia[sub a], where a[sub s] and a[sub a] are head group areas of surfactant and alcohol per molecule and I is the molar ratio of alcohol to surfactant in interfacial layer), have been derived without any approximation in the densities of the disperse phase.

Gu, G.; Wang, W. (Peking Univ., Beijing (China). Technical Physics Dept.); Yan, H. (Academia Sinica, Beijing (China). Inst. of Chemistry)

1994-10-01

89

HEALTH EFFECTS ASSESSMENT FOR N-PENTANE  

EPA Science Inventory

The report summarizes and evaluates information relevant to a preliminary interim assessment of adverse health effects associated with specific chemicals or compounds. The Office of Emergency and Remedial Response (Superfund) uses these documents in preparing cost-benefit analyse...

90

Experimental neurotoxicity and urinary metabolites of the C5-C7 aliphatic hydrocarbons used as glue solvents in shoe manufacture  

SciTech Connect

Rats were intermittently exposed (9 to 10 h/d, 5 to 6 d/week) to controlled concentrations of single analytical grad solvents in ambient air. After periods ranging from 7 to 30 weeks the animals were perfused with glutaraldehyde and samples of nerves were processed for light microscopy of sections and of teased fibers. Animals treated with n-hexane at 5000 ppm (14 weeks) or 2500 ppm (30 weeks) developed the typical giant axonal degeneration already described in rats treated continuously with 400 to 600 ppm of the same solvent for 7 weeks or more. No such alterations were found in rats subjected to the following intermittent respiratory treatments: n-hexane 500 ppm (30 weeks) or 1500 ppm (14 weeks), cyclohexane 1500 or 2500 (30 weeks), n-pentane 3000 ppm (30 weeks), n-heptane 1500 ppm (30 weeks), 2-methylpentane 1500 ppm (14 weeks), and 3-methylpentane 1500 ppm (14 weeks). The following metabolites were found in the urine of rats according to treatment (in parenthesis): 2-methyl-2-pentanol (2-methylpentane); 3-methyl-2-pentanol and 3-methyl-3-pentanol (3-methylpentane), 2-hexanol, 3-hexanol, gamma-valerolactone, 2,5-dimethylfuran, and 2,5-hexanedione (n-hexane). 2-Hexanol was found to be the main urinary metabolite of n-hexane, while 2,5-hexanedione was present only in a lesser proportion. This feature of rat metabolism suggests that in this species 2,5-hexanedione reaches an effective level at its site of action during intermittent respiratory treatment with n-hexane with difficulty and explains the high concentrations necessary to cause polyneuropathy in rats subjected to this treatment.

Frontali, N.; Amantini, M.C.; Spagnolo, A.; Guarcini, A.M.; Saltari, M.C.; Brugnone, F.; Perbellini, L.

1981-12-01

91

The correlation of nucleate boiling burn-out data  

E-print Network

A dimensionless correlation is developed for nucleate boiling buzrnout data including the following ranges of variables. Fluids - Water Bensene n - Heptane n - Pentane Ethanol Pressure - 0.0045 to 0.96 of critical pressure ...

Griffith, P.

1957-01-01

92

Some effects of aliphatic hydrocarbons on the electrical capacity and ionic currents of the squid giant axon membrane.  

PubMed Central

1. The electrical properties of squid giant axons were examined by means of admittance bridges at frequencies from 0.5 to 300 kHz. A simple equivalent circuit was used to estimate the membrane capacity. 2. The calculated membrane capacities decreased monotonically over the whole frequency range. 3. At 100 kHz and higher frequencies the membrane capacity was independent of potential. 4. At frequencies greater than 20 kHz, exposure of the axons to saturated or 0.9 saturated solutions of n-pentane (275-306 micrometer) reduced the capacity per unit area by 0.1-0.15 micro F cm-2. 5. At 1 kHz the effect of the saturated pentane solutions depended on the membrane potential. In axons having potentials between -60 and zero mV the pentane solutions lowered the capacity, whereas for potentials between -160 and -60 mV they produced little or no change. 6. Saturated solutions of n-hexane, n-heptane and n-octane exhibited qualitatively similar, but quantitatively smaller influences on the membrane capacity, the changes declining as the chain length increased. 7. Under voltage clamp, the peak inward and steady-state outward currents were partially suppressed by the hydrocarbons. Saturated solutions of n-pentane usually reduced the former (reversibly) by 60-80% and the latter by 20-40%. Solutions of n-hexane, n-heptane and n-octane appeared to have successively less effect. Except in deteriorating axons, none of the hydrocarbons produced any consistent changes in the passive membrane resistance, the resting potential or in the reversal potential of the transient inward current. 8. Both the changes in the clamp currents and in the membrane capacity were largely, though not usually completely, reversible. In the hydrocarbon solution the axons deteriorated more rapidly than normal. 9. The responses of axons of Doryteuthis plei to the hydrocarbons were very similar to those of Loligo forbesi with the exception that for the former all observed changes were some five times faster. 10. The time courses of the peak inward and steady-state outward currents on exposure of the axons to n-pentane resembled the time course of the change in membrane capacity at 100 kHz. 11. The simplest interpretation of the high frequency capacity results is suggested to be that, as for lipid bilayers, the membranes become thicker through adsorption of the hydrocarbon. PMID:7252865

Haydon, D A; Requena, J; Urban, B W

1980-01-01

93

Effect of electron scavengers to reduce the ionization current of photoexcited N,N,N',N'-tetramethyl-p-phenylenediamine in nonpolar organic liquids  

SciTech Connect

The effects of perfluoro-n-hexane, perfluoro-n-heptane, perfluoromethylcyclohexane, and perfluorodecalin to reduce the ionization current of photoexcited N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) have been studied in the solvents tetramethylsilane, 2,2-dimethylbutane (2,2-DMB), isooctane, cyclohexane, n-hexane, and n-pentane. Results are reported over a range of excitation energies from 5.2 to 6.7 eV and, for selected systems, over a temperature range from -78 to 25/sup 0/C. At quencher concentrations, c/sub q/ less than or equal to 0.2 M, the ratio of the photocurrent without quencher, J/sub 0/, to that with quencher, J, is found to be concave upward, linear, or concave downward in its dependence on c/sub q/, depending on the system studied. At higher c/sub q/, J/sub 0//J is always concave upward. Both J/sub 0/ and J increase to about the same extent as the excitation energy increases, thus maintaining J/sub 0//J constant. As the temperature increases, J increases somewhat more rapidly than does J/sub 0/ and increasingly so the larger is c/sub q/. An attempt is made to explain these results with a model based on interaction of the quencher with an epithermal electron.

Lee, K.; Lipsky, S.

1982-05-27

94

Rate Constants for the Reactions of Hydroxyl Radical with Several Alkanes, Cycloalkanes, and Dimethyl Ether  

NASA Technical Reports Server (NTRS)

Relative rate experiements were used to measure rate constants and temperature denpendencies of the reactions of OH with propane, n-butane, n-pentane, n-hexane, cyclopropane, cyclobutane, cyclopentane, and dimethyl ether.

DeMore, W.; Bayes, K.

1998-01-01

95

Direct observation of metal nanoparticles as heterogeneous nuclei for the condensation of supersaturated organic vapors: Nucleation of size-selected aluminum nanoparticles in acetonitrile and n-hexane vapors  

NASA Astrophysics Data System (ADS)

This work reports the direct observation and separation of size-selected aluminum nanoparticles acting as heterogeneous nuclei for the condensation of supersaturated vapors of both polar and nonpolar molecules. In the experiment, we study the condensation of supersaturated acetonitrile and n-hexane vapors on charged and neutral Al nanoparticles by activation of the metal nanoparticles to act as heterogeneous nuclei for the condensation of the organic vapor. Aluminum seed nanoparticles with diameters of 1 and 2 nm are capable of acting as heterogeneous nuclei for the condensation of supersaturated acetonitrile and hexane vapors. The comparison between the Kelvin and Fletcher diameters indicates that for the heterogeneous nucleation of both acetonitrile and hexane vapors, particles are activated at significantly smaller sizes than predicted by the Kelvin equation. The activation of the Al nanoparticles occurs at nearly 40% and 65% of the onset of homogeneous nucleation of acetonitrile and hexane supersaturated vapors, respectively. The lower activation of the charged Al nanoparticles in acetonitrile vapor is due to the charge-dipole interaction which results in rapid condensation of the highly polar acetonitrile molecules on the charged Al nanoparticles. The charge-dipole interaction decreases with increasing the size of the Al nanoparticles and therefore at low supersaturations, most of the heterogeneous nucleation events are occurring on neutral nanoparticles. No sign effect has been observed for the condensation of the organic vapors on the positively and negatively charged Al nanoparticles. The present approach of generating metal nanoparticles by pulsed laser vaporization within a supersaturated organic vapor allows for efficient separation between nucleation and growth of the metal nanoparticles and, consequently controls the average particle size, particle density, and particle size distribution within the liquid droplets of the condensing vapor. Strong correlation is found between the seed nanoparticle's size and the degree of the supersaturation of the condensing vapor. This result and the agreement among the calculated Kelvin diameters and the size of the nucleating Al nanoparticles determined by transmission electron microscopy provide strong proof for the development of a new approach for the separation and characterization of heterogeneous nuclei formed in organic vapors. These processes can take place in the atmosphere by a combination of several organic species including polar compounds which could be very efficient in activating charged nanoparticles and cluster ions of atmospheric relevance.

Abdelsayed, Victor; Samy El-Shall, M.

2014-08-01

96

DFT derived solvation models for organic compounds in alkane solvents  

NASA Astrophysics Data System (ADS)

From a density functional theory (DFT) analysis of solvation and the different components which comprise the free energy of solvation we propose quantitative structure-property relationship (QSPR) models to predict free energy of solvation, ?GS0, of organic compounds in seven alkane solvents ( n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, and n-hexadecane). The data contains 151 structurally different compounds containing diverse organic functions: unbranched and branched alkanes, cycloalkanes, aromatics, alcohols, aldehydes, ketones, esters, ethers, amines, nitriles, pyridines, fluorinated hydrocarbons, thiols, sulfides, carboxylic acids and nitro hydrocarbons; covering a ?GS0 range from about -50 to 0 kJ/mol. The models for the seven n-alkane solvents contain the same two molecular descriptors, one DFT descriptor (softness) and one geometric (molecular surface area). This fact suggests that the physical mechanisms behind the solvation of organic compounds in n-alkane solvents are of the same nature, as expected from the similar physical and chemical properties of alkanes. The models proposed have the merit of predicting free energy of solvation in alkane solvents with fewer descriptors than other QSPR models reported in the literature having similar statistics, allowing in this way a well-defined physical interpretation. The two descriptors have definite physical meaning corresponding to the different components which comprise free energy of solvation. Thus, the models proposed reach the desired compromise among simpleness, physical interpretation and computation time.

Delgado, Eduardo J.; Alderete, Joel B.; Jaña, Gonzalo A.

2006-06-01

97

Rate constants for OH with selected large alkanes : shock-tube measurements and an improved group scheme.  

SciTech Connect

High-temperature rate constant experiments on OH with the five large (C{sub 5}-C{sub 8}) saturated hydrocarbons n-heptane, 2,2,3,3-tetramethylbutane (2,2,3,3-TMB), n-pentane, n-hexane, and 2,3-dimethylbutane (2,3-DMB) were performed with the reflected-shock-tube technique using multipass absorption spectrometric detection of OH radicals at 308 nm. Single-point determinations at {approx}1200 K on n-heptane, 2,2,3,3-TMB, n-hexane, and 2,3-DMB were previously reported by Cohen and co-workers; however, the present work substantially extends the database to both lower and higher temperature. The present experiments span a wide temperature range, 789-1308 K, and represent the first direct measurements of rate constants at T > 800 K for n-pentane. The present work utilized 48 optical passes corresponding to a total path length of {approx}4.2 m. As a result of this increased path length, the high OH concentration detection sensitivity permitted pseudo-first-order analyses for unambiguously measuring rate constants. The experimental results can be expressed in Arrhenius form in units of cm{sup 3} molecule{sup -1} s{sup -1} as follows: K{sub OH+n-heptane} = (2.48 {+-} 0.17) x 10{sup -10} exp[(-1927 {+-} 69 K)/T] (838-1287 K); k{sub OH+2,2,3,3-TMB} = (8.26 {+-} 0.89) x 10{sup -11} exp[(-1337 {+-} 94 K)/T] (789-1061 K); K{sub OH+n-pentane} = (1.60 {+-} 0.25) x 10{sup -10} exp[(-1903 {+-} 146 K)/T] (823-1308 K); K{sub OH+n-hexane} = (2.79 {+-} 0.39) x 10{sup -10} exp[(-2301 {+-} 134 K)/T] (798-1299 K); and k{sub OH+2,3-DMB} = (1.27 {+-} 0.16) x 10{sup -10} exp[(-1617 {+-} 118 K)/T] (843-1292 K). The available experimental data, along with lower-T determinations, were used to obtain evaluations of the experimental rate constants over the temperature range from {approx}230 to 1300 K for most of the title reactions. These extended-temperature-range evaluations, given as three-parameter fits, are as follows: k{sub OH+n-heptane} = 2.059 x 10{sup -5}T{sup 1.401} exp(33 K/T) cm{sup 3} molecule{sup -1} s{sup -1} (241-1287 K); k{sub OH+2,2,3,3-TMB} = 6.835 x 10{sup -17}T{sup 1.886} exp(-365 K/T) cm{sup 3} molecule{sup -1} s{sup -1} (290-1180 K); k{sub OH+n-pentane} = 2.495 x 10{sup -16}T{sup 1.649} exp(80 K/T) cm{sup 3} molecule{sup -1} s{sup -1} (224-1308 K); k{sub OH+n-hexane} = 3.959 x 10{sup -18}T{sup 2.218} exp(443 K/T) cm{sup 3} molecule{sup -1} s{sup -1} (292-1299 K); and k{sub OH+2,3-DMB} = 2.287 x 10{sup -17}T{sup 1.958} exp(365 K/T) cm{sup 3} molecule{sup -1} s{sup -1} (220-1292 K). The experimental data and the evaluations obtained for these five larger alkanes in the present work were used along with prior data/evaluations obtained in this laboratory for H abstractions by OH from a series of smaller alkanes (C{sub 3}?C{sub 5}) to devise rate rules for abstractions from various types of primary, secondary, and tertiary H atoms. Specifically, the current scheme was applied with good success to H abstractions by OH from a series of n-alkanes (n-octane through n-hexadecane). The total rate constants using this group scheme for reactions of OH with selected large alkanes are given as three-parameter fits in this article. The rate constants for the various abstraction channels in any large n-alkane can also be obtained using the groups listed in this article. The present group scheme serves to reduce the uncertainties in rate constants for OH + alkane reactions.

Sivaramakrishnan, R.; Michael, J. V.; Chemical Sciences and Engineering Division

2009-04-30

98

[Surface characterization of urushiol-titanium chelate polymers by inverse gas chromatography].  

PubMed

Urushiol-titanium chelate polymer (UTP), the reaction product of urushiol with titanium compound, is a special eco-friendly polymer with excellent performances, such as strong acids-resistance, strong alkalis-resistance, salt solution-resistance and several organic solvent-resistance. Inverse gas chromatography (IGC) was used to measure the dispersive component of surface free energy (gamma(s)d) and the Lewis acid-base parameters of UTP in this work. The gamma(s)d and the acid/base characters of UTP' surfaces were estimated by the retention time with different non-polar and polar probes at infinite dilution region. n-Pentane (C5), n-hexane (C6), n-heptane (C7), n-octane (C8) and n-nonane (C9) were chosen as the non-polar probes to characterize the gamma(s)d. Trichloromethane (CHCl3), tetrahydrofuran (THF) and acetone were chosen as polar probes to detect the Lewis acid-base parameters. The specific free energy (deltaG(a)AB) and the enthalpy (deltaH(a)AB) of adsorption corresponding to acid-base surface interactions were determined. By correlating deltaH(a)AB with the donor and acceptor numbers of the probes, the acidic (K(a)) and the basic (K(b)) parameters of the samples were calculated. The results showed that the dispersive components of the free energy of UTP were 37.68, 33.53, 35.92, 24.01 and 31.32 mJ/m2 at 70, 80, 90, 100 and 110 degrees C, respectively. The Lewis acidic number K(a) of UTP was 0.185 3, and the Lewis basic number K(b) was 0.966 2. The results were of great importance to the study of the surface properties and the applications for urushiol-metal chelate polymers. PMID:21657056

Xu, Yanlian; Lin, Jinhuo; Xia, Jianrong; Hu, Binghuan

2011-03-01

99

Effects of oxygenate concentration on species mole fractions in premixed n-heptane flames  

E-print Network

shock tubes [2,3], jet stirred reactors [4,5], premixed [6­9], and diffusion flames [10,11]. Polycyclic. A heated quartz micro-probe coupled to an on-line gas chromatography/mass spectrometry has been used

Senkan, Selim M.

100

LAMINAR FLAME SPEEDS OF ETHANOL, n-HEPTANE, ISO OCTANE AIR MIXTURES  

Microsoft Academic Search

One of the most important properties of premixed flames is burning velocity. Laminar burning velocities play essential roles in determining several important aspects of the combustion process in spark ignition engines; among these are the ignition delay, the thickness of the wall quench layers, and the minimum ignition energy. It is found that a detailed knowledge of laminar premixed flames

HARA Takashi; TANOUE Kimitoshi

101

One-pot conversion of sugar and sugar polyols to n-alkanes without C-C Dissociation over the Ir-ReOx /SiO2 catalyst combined with H-ZSM-5.  

PubMed

High (?95 % C) yields of n-hexane and n-pentane were obtained by hydrogenolysis of aqueous sorbitol and xylitol, respectively, at 413-443 K by using the Ir-ReOx /SiO2 catalyst combined with H-ZSM-5 as a cocatalyst and n-dodecane as a cosolvent. The direct production of n-hexane from glucose or cellobiose can be achieved by using the same system. The catalyst can be reused simply by the removal of the n-dodecane phase, which contains the product alkane, and the addition of fresh n-dodecane and substrate. PMID:23463694

Chen, Kaiyou; Tamura, Masazumi; Yuan, Zhenle; Nakagawa, Yoshinao; Tomishige, Keiichi

2013-04-01

102

An Experimental Study of High-Pressure Bubble Growth Within Multicomponent Liquid Droplets Levitated in a Flowing Stream of Another Immiscible Liquid  

Microsoft Academic Search

Measurements of vaporization rates of highly superheated liquid droplets are reported at reduced pressures up to 0.4 and reduced temperatures up to 0.95. Binary and ternary mixtures of n-pentane, n-hexane, and n-decane, were studied. The experimental method involved levitating a test droplet in a flowing stream of another immiscible liquid (glycerine). Levitation was achieved by balancing the buoyancy and drag

C. T. Avedisian

1987-01-01

103

Thermodynamic parameters of conformational equilibrium in 1,2-dichloroethane: influence of medium, benzene and compensation effects  

Microsoft Academic Search

The conformational equilibrium of 1,2-dichloroethane (DCE) in 19 different media (vapour phase, liquid, solutions in n-hexane, n-heptane, carbon tetrachloride, benzene, toluene, ethyl benzene (EB), carbon disulphide, diethyl ether, bromoform, chloroform, dichloromethane, pyridine, acetone, methanol-d3, acetonitrile, glassy polystyrene (PS) matrix and 1:1 mixture of PS and EB) has been studied by IR absorption spectra. The enthalpy differences (?H0) between trans (t)

A. A. Stolov; A. B. Remizov

1995-01-01

104

Retention Phenomena Induced by Large Volume Injection of Solvents Non?Miscible with the Mobile Phase in Reversed?Phase Liquid Chromatography  

Microsoft Academic Search

Enhancement of sensitivity for spectrometric detection in liquid chromatography is obtained when increased sample volumes are loaded into the chromatographic column. A new approach of injecting large volumes of solvents non?miscible with the mobile phase is proposed. The paper focuses on the retention study of butylated hydroxyanisole (BHA) loaded into the chromatographic column dissolved in liquid alkanes (n?hexane, n?heptane, and

Andrei Medvedovici; Vasile David; Victor David; Cristina Georgita

2007-01-01

105

On the use of two-photon absorption for determination of femtosecond pump–probe cross-correlation functions  

Microsoft Academic Search

We have investigated the applicability of two-photon absorption signals (h?pump+h?probe) in common solvents for determination of the pump–probe cross-correlation function in transient absorption experiments. Ten different solvents, including water, lower alcohols, n-hexane, n-heptane, acetonitrile, dichloromethane, chloroform and tetrachloromethane, were studied with UV excitation and UV-visible probe pulses. We report on how the signals are influenced by the relative polarization of

Marcus Rasmusson; Alexander N. Tarnovsky; Eva Åkesson; Villy Sundström

2001-01-01

106

Platinum supported on carbon aerogels as catalysts for the n-hexane aromatization  

Microsoft Academic Search

A series of Pt-catalysts were prepared by impregnation of carbon aerogels. The supports were selected on the basis of a different porous texture. The dispersion and sintering resistance of the catalyst were evaluated by varying the Pt-loading and the pre-treatment conditions. XRD, XPS, HRTEM and H2-chemisorption were used to determine the nature and dispersion of Pt-particles. The behavior of these

F. J. Maldonado-Hódar

107

Removal of n-hexane by Fusarium solani with a gas-phase biofilter.  

PubMed

A gas-phase biofilter inoculated with the fungus Fusarium solani, isolated from a consortium grown on hexane vapors, was used to degrade this compound. The biofilter, packed with perlite and operated with an empty bed residence time of 60 s, was supplied with hexane concentrations between 0.5 gm(-3) and 11 gm(-3). Biofilter performance was evaluated over 100 days of operation. Several strategies for supplying the nutritive mineral medium were assayed to maintain favorable conditions for the fungal growth and activity. The Fusarium system was able to sustain an average elimination capacity of 90 gm(-3)(reactor) h(-1) with a maximum of 130 gm(-3)(reactor) h(-1) . The mass transfer limitations due to high biomass development in the biofilter were confirmed in batch experiments. Bacterial contamination was observed, but experiments in the biofilter and in batch reactors using selective inhibitors and controlled pH confirmed the predominant role of the fungus. Results indicate that fungal biofilters can be an effective alternative to conventional abatement technologies for treating hydrophobic compounds. PMID:15933872

Arriaga, Sonia; Revah, Sergio

2005-12-01

108

Esterification kinetics of triglycerides in n-hexane catalyzed by an immobilized lipase  

E-print Network

and sets the basis for a future work of this process using another solvent medium, such as supercritical carbon dioxide. It has been reported in the literature that a higher conversion can be achieved for enzymatic esterifications of pure fatty acids when... using supercritical carbon dioxide as the solvent medium. The fatty acid production through a biological process (Enzymatic oil splitting) is less expensive and easier to operate than the chemical process. In general the best option to produce fatty...

Gomez Ruiz, Alejandro

2012-06-07

109

Mechanism of complete n-hexane oxidation on silica supported cobalt and manganese catalysts  

Microsoft Academic Search

Mono- and bi-component cobalt and manganese samples were prepared by impregnation of silica with aqueous solutions of Co(NO3)2·6H2O and\\/or Mn(NO3)2·6H2O. The bi-component samples were obtained by a common solution of Co- and Mn nitrates (CoMn-MS) or by deposition of cobalt on calcined Mn sample (Co+Mn). The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature programmed reduction

S. Todorova; A. Naydenov; H. Kolev; J. P. Holgado; G. Ivanov; G. Kadinov; A. Caballero

110

Enzymatic synthesis of geraniol and citronellol esters by direct esterification in n-hexane  

Microsoft Academic Search

Short chain fatty acid esters of geraniol and citronellol were synthesized by lipase-catalyzed direct esterification with yields ranging from 90 to 100% molar conversion. The effect of the order of addition of substrates, solvent and enzyme was investigated. Yields were highest when the solvent was added first followed by the substrates and then the lipase.

Paul A. Claon; Casimir C. Akoh

1993-01-01

111

Estimated MP2 and CCSD(T) interaction energies of n-alkane dimers at the basis set limit: Comparison of the methods of Helgaker et al. and Feller  

NASA Astrophysics Data System (ADS)

The MP2 (the second-order Møller-Plesset calculation) and CCSD(T) (coupled cluster calculation with single and double substitutions with noniterative triple excitations) interaction energies of all-trans n-alkane dimers were calculated using Dunning's [J. Chem. Phys. 90, 1007 (1989)] correlation consistent basis sets. The estimated MP2 interaction energies of methane, ethane, and propane dimers at the basis set limit [EMP2(limit)] by the method of Helgaker et al. [J. Chem. Phys. 106, 9639 (1997)] from the MP2/aug-cc-pVXZ (X =D and T) level interaction energies are very close to those estimated from the MP2/aug-cc-pVXZ (X =T and Q) level interaction energies. The estimated EMP2(limit) values of n-butane to n-heptane dimers from the MP2/cc-pVXZ (X =D and T) level interaction energies are very close to those from the MP2/aug-cc-pVXZ (X =D and T) ones. The EMP2(limit) values estimated by Feller's [J. Chem. Phys. 96, 6104 (1992)] method from the MP2/cc-pVXZ (X =D, T, and Q) level interaction energies are close to those estimated by the method of Helgaker et al. from the MP2/cc-pVXZ (X =T and Q) ones. The estimated EMP2(limit) values by the method of Helgaker et al. using the aug-cc-pVXZ (X =D and T) are close to these values. The estimated EMP2(limit) of the methane, ethane, propane, n-butane, n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane dimers by the method of Helgaker et al. are -0.48, -1.35, -2.08, -2.97, -3.92, -4.91, -5.96, -6.68, -7.75, and -8.75kcal /mol, respectively. Effects of electron correlation beyond MP2 are not large. The estimated CCSD(T) interaction energies of the methane, ethane, propane, and n-butane dimers at the basis set limit by the method of Helgaker et al. (-0.41, -1.22, -1.87, and -2.74kcal/mol, respectively) from the CCSD(T )/cc-pVXZ (X =D and T) level interaction energies are close to the EMP2(limit) obtained using the same basis sets. The estimated EMP2(limit) values of the ten dimers were fitted to the form m0+m1X (X is 1 for methane, 2 for ethane, etc.). The obtained m0 and m1 (0.595 and -0.926kcal /mol) show that the interactions between long n-alkane chains are significant. Analysis of basis set effects shows that cc-pVXZ (X =T, Q, or 5), aug-cc-pVXZ (X =D, T, Q, or 5) basis set, or 6-311G** basis set augmented with diffuse polarization function is necessary for quantitative evaluation of the interaction energies between n-alkane chains.

Tsuzuki, Seiji; Honda, Kazumasa; Uchimaru, Tadafumi; Mikami, Masuhiro

2006-03-01

112

A study of PVT relations for carbon dioxide, n-pentane, and n-octane mixtures using a recombination apparatus  

E-print Network

be calculated with the correlation. and, The correlations suggested by Alston, et. a/. i'"l are as follows: Pco2-Lo = 8. 78(10%)(TR)1. 06(Mcs+)1. 7s(xvci/xmt)o. " - 2. 2 Pcoz-sto = 8. 78(10-4)(TR)'OS(M05+) '7e . . . . . 2. 3 where Pood Lo is the MMP... . 20 711 50 Sas eo 801. 00 ese 30 ees. eo 072. 00 070. 70 67iAD 0. 00 ~ 35 7$3 I I. ee 10. 03 \\ 0. 05 2$. 04 27. 0D 32. 1$ 36. 03 40. 03 ~ 4. 57 ~ 0A8 53 87 50 0$ 03 08 0$. 20 72 00 78 35 0 3. I 0 105 50 112. 00 I 'I 7. 70...

Wirawan, Januar Fitri Santo

2012-06-07

113

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

PubMed Central

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. PMID:12226177

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

1996-01-01

114

Experimental study of heat conductivity of n-heptane-n-octane-isooctane liquid ternary mixtures at high pressure  

SciTech Connect

Heat conductivity of liquid ternary mixtures of various compositions at various pressures and temperatures was experimentally studied. Dependence of heat conductivities of ternary mixtures on concentration of components was established. An equation linking the heat conductivities of ternary mixtures through those of pure components and appropriate binary mixtures was proposed.

Naziev, D.Ya. [Azerbaidzhan State Oil Academy, Baku (Russian Federation)

1994-03-20

115

On the Combustion Chemistry of n-Heptane and n-Butanol Blends Darshan M. A. Karwat,*,  

E-print Network

studied in shock tubes,1-7 jet-stirred reactors,8 rapid compression machines,9-13 and premixed laminar of n-C7H16 oxidation have been measured. Specifically, gas sampling techniques have been used in jet, Livermore, California 94550, United States *S Supporting Information ABSTRACT: High-speed gas sampling

Wooldridge, Margaret S.

116

Figure S1. The 17-monitor-average daily maximal 8-hour O3 in the Houston metropolitan area during July-October in both 2000 and 2006; the time periods of the two TexAQS are marked by  

E-print Network

_all n_butane_all 1_butene_all t_2_butene_all c_2_butene_all 1_3_butandiene_all cyclopentane_all cyclopentene_all isopentane_all n_pentane_all 1_pentene_all t_2_pentene_all c_2_pentene_all 3_methyl_1_butene_all 2_methyl_2_butene_all 2_methyl_1_butene_all isoprene_all n_hexane_all 2_methyl_pentane_all 3_methyl

Meskhidze, Nicholas

117

Photocurrent enhancement in nonpolar liquids by the addition of electron scavengers  

SciTech Connect

The photocurrent from anthracene, triphenylamine, and N,N,N',N'-tetramethyl-p-phenylenediamine excited above their ionization thresholds in liquid n-pentane or n-hexane is found to be enhanced by the addition of low concentrations (/approx lt/0.02 M) of the electron scavengers perfluoromethylcyclohexane or perfluorodecalin. The enhancement is not observed in solvents of higher electron mobility (e.g.,. cyclohexane, isooctane, etc.) or for scavengers of lower electron affinity (e.g., n-perfluorohexane). For the solute naphthalene, no enhancement is observed under any conditions. The effects of excitation energy and applied electric field strength are reported.

Howell, G.A.; Lee, K.; Tweeten, D.W.; Lipsky, S.

1988-07-14

118

Total cross section of electron scattering by fluorocarbon molecules  

NASA Astrophysics Data System (ADS)

A compact linear electron transmission apparatus was used for the measurement of the total electron scattering cross section at 4-500 eV. Total cross sections of chlorofluorocarbon (CCl2F2), hydrochlorofluorocarbon (CHClF2), perfluoropropane (C3F8), perfluoro-n-pentane (C5F12), perfluoro-n-hexane (C6F14) and perfluoro-n-octane (C8F18) were obtained experimentally and compared with the values obtained from a theoretical calculation and semi-empirical model calculation.

Yamada, T.; Ushiroda, S.; Kondo, Y.

2008-12-01

119

QCM gas phase detection with ceramic materials—VOCs and oil vapors  

Microsoft Academic Search

Titanate sol–gel layers imprinted with carbonic acids were used as sensitive layers on quartz crystal microbalance. These\\u000a functionalized ceramics enable us detection of volatile organic compounds such as ethanol, n-propanol, n-butanol, n-hexane, n-heptane, n-\\/iso-octane, and n-decane. Variation of the precursors (i.e., tetrabutoxy titanium, tetrapropoxy titanium, tetraethoxy titanium) allows us to\\u000a tune the sensitivity of the material by a factor of

Usman Latif; Andreas Rohrer; Peter A. Lieberzeit; Franz L. Dickert

2011-01-01

120

Phase equilibria study of binary and ternary mixtures of { N-octylisoquinolinium bis{(trifluoromethyl)sulfonyl}imide + hydrocarbon, or an alcohol, or water}  

Microsoft Academic Search

Isoquinolinium ionic liquid has been studied as the temperature–composition phase diagrams of 13 binary mixtures composed of the ionic liquid (IL) N-octylisoquinolinium bis{(trifluoromethyl)sulfonyl}imide, ([C8iQuin][NTf2]) and an aliphatic hydrocarbon (n-hexane, or n-heptane), or cyclic hydrocarbons (cyclohexane, or cycloheptane), or an aromatic hydrocarbon (toluene, or ethylbenzene, or n-propylbenzene, or thiophene), or an alcohol (1-butanol, or 1-hexanol, or 1-octanol, or 1-decanol, or 1-dodecanol,

Urszula Doma?ska; Maciej Zawadzki; Marek Królikowski; Anna Lewandrowska

121

Trapping of Methanol, Hydrogen Cyanide, and n-Hexane in Water Ice, above Its Transformation Temperature to the Crystalline Form  

NASA Astrophysics Data System (ADS)

HCN and n-C 6H 14were found experimentally to be trapped in water ice, when codeposited with water vapor on a cold plate, at 140 K and CH 3OH even at 160 K. At these temperatures at least part of the water ice is cystalline. These three gases have relatively high sublimation temperatures, whereas the gases studied earlier, Ar, Kr, Xe, CO, CH 4, and N 2, which have lower sublimination temperatures, are trapped only in amorphous water ice, up to ˜100 K. It seems that the major factor determining the efficiency of gas trapping by water ice, during codeposition of a gas-water vapor mixture on a cold plate, is the sublimation temperatures of the gases to be trapped. Those with a high sublimation temperature remain, during codeposition, longer in the pores of the water ice which are open to the surface, until they are covered by additional ice layers. Only methanol seems to form a clathrate hydrate, in agreement with the experimental results of D. Blake et al.(1991), Science254, 548-551), which points to the importance of the interaction of the gas molecules with the water molecules in the ice. Consequently, comets and icy satellites that were formed in the Jupiter-Saturn region and their subnebulae could trap CH 3OH, HCN, and heavy hydrocarbons, whereas comets and icy satellites that were formed in the Uranus-Neptune region, at the outskirts of the Saturnian subnebulae (Titan), and beyond the planets in the Kuiper belt could trap also gases having lower sublimation temperatures.

Notesco, G.; Bar-Nun, A.

1997-04-01

122

Retama monosperma n-hexane extract induces cell cycle arrest and extrinsic pathway-dependent apoptosis in Jurkat cells  

PubMed Central

Background Retama monosperma L. (Boiss.) or Genista monosperma L. (Lam.), locally named as “R’tam”, is an annual and spontaneous plant belonging to the Fabaceae family. In Morocco, Retama genus is located in desert regions and across the Middle Atlas and it has been widely used in traditional medicine in many countries. In this study, we show that Retama monosperma hexane extract presents significant anti-leukemic effects against human Jurkat cells. Methods Human Jurkat cells, together with other cell lines were screened with different concentrations of Retama monosperma hexane extract at different time intervals. Growth inhibition was determined using luminescent-based viability assays. Cell cycle arrest and apoptosis were measured by flow cytometry analysis. Combined caspase 3 and 7 activities were measured using luminometric caspase assays and immunoblots were performed to analyze expression of relevant pro- and anti-apoptotic proteins. GC-MS were used to determine the chemical constituents of the active extract. Results Retama monosperma hexane extract (Rm-HE) showed significant cytotoxicity against Jurkat cells, whereas it proved to be essentially ineffective against both normal mouse fibroblasts (NIH3T3) and normal lymphocytes (TK-6). Cytometric analysis indicated that Rm-HE promoted cell cycle arrest and apoptosis induction accompanied by DNA damage induction indicated by an increase in p-H2A.X levels. Rm-HE induced apoptosis was partially JNK-dependent and characterized by an increase in Fas-L levels together with activation of caspases 8, 3, 7 and 9, whereas neither the pro-apoptotic nor anti-apoptotic mitochondrial membrane proteins analyzed were significantly altered. Chemical identification analysis indicated that ?-linolenic acid, campesterol, stigmasterol and sitosterol were the major bioactive components within the extract. Conclusions Our data suggest that bioactive compounds present in Rm-HE show significant anti leukemic activity inducing cell cycle arrest and cell death that operates, at least partially, through the extrinsic apoptosis pathway. PMID:24460687

2014-01-01

123

Combustion of liquid fuels in a flowing combustion gas environment at high pressures  

NASA Technical Reports Server (NTRS)

The combustion of fuel droplets in gases which simulate combustion chamber conditions was considered both experimentally and theoretically. The fuel droplets were simulated by porous spheres and allowed to gasify in combustion gases produced by a burner. Tests were conducted for pressures of 1-40 atm, temperatures of 600-1500 K, oxygen concentrations of 0-13% (molar) and approach Reynolds numbers of 40-680. The fuels considered in the tests included methanol, ethanol, propanol-1, n-pentane, n-heptane and n-decane. Measurements were made of both the rate of gasification of the droplet and the liquid surface temperature. Measurements were compared with theory, involving various models of gas phase transport properties with a multiplicative correction for the effect of forced convection.

Canada, G. S.; Faeth, G. M.

1975-01-01

124

Fuel property effects on engine combustion processes. Final report  

SciTech Connect

A major obstacle to improving spark ignition engine efficiency is the limitations on compression ratio imposed by tendency of hydrocarbon fuels to knock (autoignite). A research program investigated the knock problem in spark ignition engines. Objective was to understand low and intermediate temperature chemistry of combustion processes relevant to autoignition and knock and to determine fuel property effects. Experiments were conducted in an optically and physically accessible research engine, static reactor, and an atmospheric pressure flow reactor (APFR). Chemical kinetic models were developed for prediction of species evolution and autoignition behavior. The work provided insight into low and intermediate temperature chemistry prior to autoignition of n-butane, iso-butane, n-pentane, 1-pentene, n-heptane, iso-octane and some binary blends. Study of effects of ethers (MTBE, ETBE, TAME and DIPE ) and alcohols (methanol and ethanol) on the oxidation and autoignition of primary reference fuel (PRF) blends.

Cernansky, N.P.; Miller, D.L.

1995-04-27

125

Extraction of gold(III) from hydrochloric acid solutions by CTAB/n-heptane/iso-amyl alcohol/Na2SO3 microemulsion.  

PubMed

The extraction of Au(III) from hydrochloric acid solutions by microemulsion was studied. The extraction experiments were carried out using cetyltrimethylammonium bromide (CTAB) as surfactant and iso-amyl alcohol as co-surfactant. Au(III) was found to be extracted into the microemulsion phase due to ion pair formation such as AuCl(4)(-)CTAB(+). The influence of temperature on the extraction of Au(III) has been investigated at temperatures ranging from 288 to 313 K. Temperature was found to decrease the distribution of Au(III). Thermodynamic parameters like enthalpy and entropy of the extraction, calculated by applying Van't Hoff equation, were -36.76 kJ mol(-1) and -84.87 J mol(-1) K(-1), respectively. Furthermore, the influence of the concentrations of hydrogen ion and chloride anion on the extraction efficiency (E%) were verified. Au(III) was extracted quantitatively (E%>99%) and selectively at the whole range of HCl concentrations (0.2-5 M). Recovery of gold from electrical waste and treatment of CTAB wastewater generated from the extraction were also discussed. Thus, the extraction of Au(III) from hydrochloric acid solutions by microemulsion is an effective approach. PMID:21236565

Lu, Wenjuan; Lu, Yanmin; Liu, Fei; Shang, Kai; Wang, Wei; Yang, Yanzhao

2011-02-28

126

Extraction of gold(III) from hydrochloric acid solutions by CTAB\\/ n-heptane\\/iso-amyl alcohol\\/Na 2SO 3 microemulsion  

Microsoft Academic Search

The extraction of Au(III) from hydrochloric acid solutions by microemulsion was studied. The extraction experiments were carried out using cetyltrimethylammonium bromide (CTAB) as surfactant and iso-amyl alcohol as co-surfactant. Au(III) was found to be extracted into the microemulsion phase due to ion pair formation such as AuCl4?CTAB+. The influence of temperature on the extraction of Au(III) has been investigated at

Wenjuan Lu; Yanmin Lu; Fei Liu; Kai Shang; Wei Wang; Yanzhao Yang

2011-01-01

127

A kinetic study of n-heptane catalytic cracking over a commercial Y-type zeolite under supercritical and subcritical conditions  

SciTech Connect

Heptane catalytic cracking over a commercial Y-type zeolite (Promoted Octacat) was studied at 475{degrees}C under subcritical and supercritical hydrocarbon conditions. Kinetic measurements showed that the activity of the catalyst was substantially higher during supercritical cracking, suggesting stabilization of the catalyst toward rapid deactivation. A mechanism based on kinetic and in situ cylindrical internal reflectance FTIR (CIR-FTIR) results was developed to explain the performance of the catalyst under supercritical conditions. The dense supercritical reaction medium, well known for its enhanced solubilization capabilities, continuously removes the newly formed coke through solubilization from the zeolite supercages, pore mouths, and the external surface. This results in a higher number of available active sites to perform catalytic cracking and in lower pore diffusion limitations due to the avoidance of pore blockage. The significantly higher yields of the olefinic and paraffinic reaction products and the higher paraffin/olefin ratios under supercritical cracking conditions are in agreement with the above mechanism. Finally, it was shown that a partial regeneration of a moderately deactivated cracking catalyst is possible by the supercritical reaction medium. Reactivation of a severely deactivated catalyst could not be achieved. 36 refs., 16 figs., 4 tabs.

Dardas, Z.; Sueer, M.G.; Ma, Y.H.; Moser, W.R. [Worcester Polytechnic Institute, MA (United States)] [Worcester Polytechnic Institute, MA (United States)

1996-09-01

128

A Journey from n-Heptane to Liquid Transportation Fuels. 1. The Role of the Allylic Radical and Its Related Species in Aromatic  

E-print Network

the concentration levels of all olefins, most higher unsaturated species, and benzene. To correctly predict the concentration of benzene, the reaction rates involving allyl-radical-related species need to be accurate the concentrations of benzene and higher aromatics. Introduction Combustion chemistry of paraffinic components

Utah, University of

129

Kinetic inhibitor effects on methane/propane clathrate hydrate-crystal growth at the gas/water and water/ n-heptane interfaces  

NASA Astrophysics Data System (ADS)

The influence of the kinetic inhibitor poly( N-vinylpyrrolidone) or PVP on hydrate methane/propane hydrate formation was studied in pre-saturated liquid water with and without the presence of heptane under different undercooling conditions. It was found that when the inhibitor concentration was 0.1 wt%, hydrate formation started as a film at the gas/water interface similar to the crystal behavior without inhibitor. When the inhibitor concentration was 0.5 wt% hydrate formation started at the wall above the gas/water interface and the hydrate film at the gas/water interface was observed as well. However, for inhibitor concentration 1.0 wt%, the hydrate started forming from water droplets attached to the wall above the gas/liquid interface and grew catastrophically. When the inhibitor concentration was 0.1 wt% and undercooling was 13.7 or 8.1 K whiskery or fiber-type hydrate crystals, respectively, were seen within the liquid pool. This morphology was not observed in the absence of PVP. When inhibitor concentration was 0.5 or 1.0 wt% or undercooling was 3.2 K, there was no crystal growth within the liquid pool. Floating crystals were also observed, but were needle-type and thus different from the equiaxed floating crystals found in the system without the inhibitor.

Kumar, Rajnish; Lee, Ju Dong; Song, Myungho; Englezos, Peter

2008-03-01

130

LIQUID-LIQUID EQUILIBRIA FOR THREE- AND FOUR-COMPONENT SYSTEMS COMPRISED OF WATER + ETHANOL + TOLUENE + N-HEPTANE AT 293 K (R821114)  

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

131

Calorimetric, Viscosimetric, and Light Scattering Studies of the Aggregation of, and the Solubilization of Water by, Triton X-35 in n-Heptane  

Microsoft Academic Search

The behavior of a nonionic surfactant TX-35 in solution inn-heptane in the presence and absence of added water has been examined using the microcalorimetric, viscosimetric, and quasielastic light scattering experimental methods. In this paper, we were interested in the aggregation process of the poly(oxyethylene) glycol alkylphenyl ether inn-heptane and in the solubilization of water in the reverse micelle of the

S. Lagerge; E. Grimberg-Michaud; K. Guerfi; S. Partyka

1999-01-01

132

High pressure combustion of liquid fuels. [alcohol and n-paraffin fuels  

NASA Technical Reports Server (NTRS)

Measurements were made of the burning rates and liquid surface temperatures for a number of alcohol and n-paraffin fuels under natural and forced convection conditions. Porous spheres ranging in size from 0.64-1.9 cm O.D. were emloyed to simulate the fuel droplets. The natural convection cold gas tests considered the combustion in air of methanol, ethanol, propanol-1, n-pentane, n-heptane, and n-decane droplets at pressures up to 78 atmospheres. The pressure levels of the natural convection tests were high enough so that near critical combustion was observed for methanol and ethanol vaporization rates and liquid surface temperature measurements were made of droplets burning in a simulated combustion chamber environment. Ambient oxygen molar concentrations included 13%, 9.5% and pure evaporation. Fuels used in the forced convection atmospheric tests included those listed above for the natural convection tests. The ambient gas temperature ranged from 600 to 1500 K and the Reynolds number varied from 30 to 300. The high pressure forced convection tests employed ethanol and n-heptane as fuels over a pressure range of one to 40 atmospheres. The ambient gas temperature was 1145 K for the two combustion cases and 1255 K for the evaporation case.

Canada, G. S.

1974-01-01

133

Comparison of the hydrogenating capacities of Pt. Re and Pt-Re/Al/sub 2/O/sub 3/ in n-hexane reforming  

SciTech Connect

The introduction of rhenium as a second metal and its sulfidation increase the stability and selectivity of Pt Al/sub 2/O/sub 3/ catalyst for naphtha reforming. The addition of Re and S affects the metallic function of the catalyst but not the acidic one. One proposed cause of the improvement of the catalyst by addition of Re and S is higher resistance to deactivation by coking. Others stated that Pt-Re has a greater capacity than Pt to hydrogenate cyclopentadiene, one of the most important coke precursors. Others ascribed to Re the capacity to destroy by hydrogenolysis the coke precursors without necessity of an intimate contact between Pt and Re. Others stated that Re reduces the dehydrogenating capacity of Pt, thereby increasing the dehydrogenation of coke precursors and, in the case of methylcyclopentadiene reforming, decreasing its condensation-dehydrogenation to produce heavy aromatics and poly-ring coke. This paper presents information about the hydrogenation-dehydrogenation capacity of the metallic component of Pt/Al/sub 2/O/sub 3/ reforming catalyst, comparing the activity of Pt, Re and Pt-Re for hydrogenating their own coke and for recovering the activity of metallic-catalyzed reactions.

Parera, J.M.; Beltramini, J.N.; Querini, C.A.; Figoli, N.S.

1986-09-01

134

Relative permittivities and refractive indices on mixing for ( n -hexane + 1-pentanol, or 1-hexanol, or 1-heptanol ) at T = 298.15 K  

Microsoft Academic Search

A previous study on the physical properties of (1-alcohol +n -alkane) has established a correlation between dielectric permittivity at 1 GHz and excess molar volumesVE for all binary systems that were studied. In order to determine whether this behaviour is similar at lower frequencies, relative permittivity ??was measured at 100 kHz. The refractive indexnD was measured to explore the effects

M. I. Paz Andrade

2000-01-01

135

Adsorption and reaction behavior of perfluoro-n-alkanes on Al{sub 2}O{sub 3}  

SciTech Connect

The adsorption of perfluoro-n-pentane and perfluoro-n-hexane on {gamma}-Al{sub 2}O{sub 3} at the solid/vapor interface has been studied by infrared spectroscopy and temperature-programmed desorption (TPD). At ambient beam temperature perfluorocarbons are adsorbed as intact, unchanged molecules and undergo chemical transformations leading to the formation of adsorbed, unsaturated carboxylate species. With increasing temperature further reactions occur, finally resulting in deep oxidation of all adsorbed species (indicated by desorption of CO and CO{sub 2}). These reactions are initiated by the formation of coordination bonds between perfluorocarbons and Lewis-acidic surface sites (coordinatively unsaturated cations) of Al{sub 2}O{sub 3}, followed by abstraction of fluorine from the adsorbed molecules.

Sokoll, R.; Tiller, H.J. [Friedrich-Schiller-Univ. Jena (Germany). Inst. fuer Physikalische Chemie] [Friedrich-Schiller-Univ. Jena (Germany). Inst. fuer Physikalische Chemie

1998-09-15

136

Vacuum ultraviolet absorption spectra of aromatic molecules in solution  

SciTech Connect

The absorption spectra of benzene, naphthalene, azulene, N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD), pyrene, and fluoroanthene were measured in liquid perfluoro-n-hexane (PFn-H) in the range 35,000 to 65,000 cm/sup -1/ and in liquid n-pentane (n-Pt) in the range 35,000 to 59,000 cm/sup -1/, using a 150-..mu..m-thick cell. The absorption spectra in PFn-H show more structure than those in n-Pt and because they are extended in the Rydberg transition region may be used to separate Rydberg from core transitions in the gaseous spectra of the molecules studied. The transmission spectra for PFn-H, n-Pt, and some of the most commonly used hydrocarbon solvents are presented also. 5 figures, 6 tables.

Kourouklis, G.A.; Siomos, K.; Christophorou, L.G.

1982-01-01

137

Photoconductivity induced by single-proton excitation of aromatic molecules in liquid hydrocarbons  

SciTech Connect

The spectral dependence of the photoconductivity of several aromatic solutes (anthracene, 1,2-benzanthracene, perylene, pyrene, azulene, ..cap alpha..-methylnaphthalene, and triphenylamine) in liquid hydrocarbon solvents (neopentane, 2,2,4-trimethylpentane(2,2,4-TMP), 2,2,4,4-tetramethylpentane (2,2,4,4-TMP), and n-pentane) are reported. In liquids which exhibit high thermal electron mobilities, relative maxima or shoulders are detected in the photoconductivity spectra. The corresponding transitions are thought to involve the formation of Rydberg states as precursors of separated charges. For anthracene and azulene, the transitions occur at approximately the same energy where Rydberg lines are observed in the gas phase. Quenching of the photoconductivity by perfluoromethylcyclohexane and by perfluoro-n-hexane supports this hypothesis.

Holroyd, R.A.; Preses, J.M.; Boettcher, E.H.; Schmidt, W.F.

1984-02-16

138

Natural and synthetic oviposition stimulants forCatolaccus grandis (Burks) females.  

PubMed

Oviposition behavior was elicited fromCatolaccus grandis (Burks) (Hymenoptera: Pteromalidae) females, an ectoparasitoid of the boll weevil,Anthonomus grandis Boheman (Coleoptera: Curculionidae), by smears of freshly cut cotton bolls or smears of extracts prepared with boll weevil damaged or undamaged cotton boll tissues. Oviposition behavior was also elicited fromC. grandis females by smears made withn-pentane,n-hexane,n-heptane, and isooctane. This is the first report of oviposition behavior elicited for any parasitoid by these short-chain saturated hydrocarbons (alkanes), introducing a new concept on the chemical mediation of parasitoid behavior during host selection. Oviposition behavior was also elicited fromC. grandis females by volatiles emanating from an artificial diet devoid of insect components that was specifically developed for the in vitro rearing of ectoparasitoids. The possible use of a synergistic combination ofn-hexane and diet to optimize the mechanized production of noncontaminated eggs is also discussed. PMID:24242653

Guerra, A A; Martinez, S; Sonia Del Rio, H

1994-07-01

139

B{sub 2u} {yields} A{sub 1g} fluorescence excitation spectrum of liquid benzene from 250 to 150 nm  

SciTech Connect

The B{sub 2u} {yields} A{sub 1g} fluorescence quantum yield of benzene has been obtained for excitations from 250 to 150 nm in the solvents n-hexane, isooctane, n-perfluorohexane, n-pentane, cyclohexane, and cis-decalin. In n-hexane and isooctane, measurements have been made over a range of benzene concentrations from 0.11{sub 2} to 11.2 M (the neat liquid). In dilute solutions, the sudden losses in fluorescence as the excitation wavelength sweeps from the first into the second absorption system and then again as the excitation wavelength sweeps from the second into the third absorption system are correlated with the behavior of benzene vapor in the region of channel three. Increasing the benzene concentration causes abatements in the rate of loss of fluorescence with decreasing excitation wavelength in the regions of the second and third absorption systems and, above 2 M, causes a reversal of this rate so as to cause a recovery of the fluorescence in the region of the third absorption system. These changes are correlated with the effects of benzene concentration on the electronic absorption spectrum and with reported effects of clustering on the multiphoton photoionization efficiency. 59 refs., 13 figs.

Saik, V.O.; Lipsky, S. [Univ. of Minnesota, Minneapolis, MN (United States)

1995-06-29

140

Catalytic properties and deactivation behavior of crystalline microporous MAPO-36  

SciTech Connect

MAPO-36 showed high catalytic activity in conversion reactions of alcohols, linear, branched, and cycloalkanes, and aromatics. In ethanol, n-hexane, cyclohexane, and isooctane conversion reactions, MAPO-36 showed significantly higher conversion and concentration of aromatics than MAPO-5, SAPO-5, and AIPO[sub 4]-5. The distribution of aliphatics and aromatics is different in these reactions over MAPO-36, MAPO-5, SAPO-5, AIPO[sub 4]-5, and H-ZSM-5. MAPO-36 exhibited lower n-hexane conversion than H-ZSM-5; however, the aromatics yield was higher. The trend was reversed in the cyclohexane conversion reaction. The toluene disproportionation and o-xylene conversion activity of MAPO-36 is very high as compare to MAPO-5, SAPO-5, AIPO[sub 4]-5, and H-ZSM-5. In the o-xylene conversion reaction, MAPO-36 exhibited higher xylene loss, indicating poisoned strong acid sites on the catalytic properties of the catalysts was studied. The influence of pulse number on the catalytic activity of MAPO-36 in n-pentane, n-hexane, 3-methylpentane, cyclohexane, methanol, and toluene reactions was investigated. The deactivation of MAPO-36 is lowest as compared to MAPO-5, SAPO-5, and AIPO[sub 4]-5 in the ethylbenzene conversion reaction. The results on the dependence of cumene cracking activity of MAPO-36, SAPO-5, and AIPO[sub 4]-5 or time-on-stream show that the initial activity of MAPO-36 is high, though it decreases faster than that of SAPO-5 an AIPO[sub 4]-5. In situ IR techniques were used to investigate coke formation and temperature programmed oxidation of coke deposited during the cumene cracking reaction over MAPO-36. 23 refs., 8 figs., 8 tabs.

Akolekar, D.B. (Univ. of Laval, Quebec (Canada))

1993-11-01

141

Vapor-liquid equilibrium constants at infinite dilution determined by a gas stripping method: ethane, propane, n-butane, n-pentane in the methane-n-decane system  

Microsoft Academic Search

A new apparatus to measure partition coefficients Kinfinity \\/SUB s\\/ at infinite dilution up to 200 10⁵ Pa and 423 K is described. Measurements of the systems: (1) methane-ethane-n-decane and methane-propane-n-decane at 294.25 K; and (2) methane-n-butane-n-decane at 344.25 K illustrate the reproducibility and good agreement with literature data. In addition, new data were obtained for the system methane-npentane-n-decane at

D. Legret; J. Desteve; H. Renon; D. Richon

1983-01-01

142

The Measurement of Laminar Burning Velocities and Markstein Numbers for Iso-octane–Air and Iso-octane–n-Heptane–Air Mixtures at Elevated Temperatures and Pressures in an Explosion Bomb  

Microsoft Academic Search

Spherically expanding flames have been employed to measure flame speeds, from which have been derived corresponding laminar burning velocities at zero stretch rate. Two burning velocities are defined, one based upon the rate of propagation of the flame front, the other on the rate of formation of burned gas. To express the effects of flame stretch upon burning velocity, Markstein

D. Bradley; R. A. Hicks; M. Lawes; C. G. W. Sheppard; R. Woolley

1998-01-01

143

Fuel droplet burning rates at high pressures.  

NASA Technical Reports Server (NTRS)

Combustion of methanol, ethanol, propanol-1, n-pentane, n-heptane, and n-decane was observed in air under natural convection conditions, at pressures up to 100 atm. The droplets were simulated by porous spheres, with diameters in the range from 0.63 to 1.90 cm. The pressure levels of the tests were high enough so that near-critical combustion was observed for methanol and ethanol. Due to the high pressures, the phase-equilibrium models of the analysis included both the conventional low-pressure approach as well as high-pressure versions, allowing for real gas effects and the solubility of combustion-product gases in the liquid phase. The burning-rate predictions of the various theories were similar, and in fair agreement with the data. The high-pressure theory gave the best prediction for the liquid-surface temperatures of ethanol and propanol-1 at high pressure. The experiments indicated the approach of critical burning conditions for methanol and ethanol at pressures on the order of 80 to 100 atm, which was in good agreement with the predictions of both the low- and high-pressure analysis.

Canada, G. S.; Faeth, G. M.

1973-01-01

144

Quantitative analysis of volatile organic compounds released and consumed by rat L6 skeletal muscle cells in vitro.  

PubMed

Knowledge of the release of volatile organic compounds (VOCs) by cells provides important information on the origin of VOCs in exhaled breath. Muscle cells are particularly important, since their release of volatiles during the exertion of an effort contributes considerably to breath concentration profiles. Presently, the cultivation of human skeletal muscle cells is encountering a number of obstacles, necessitating the use of animal muscle cells in in vitro studies. Rat L6 skeletal muscle cells are therefore commonly used as a model for studying the molecular mechanisms of human skeletal muscle differentiation and functions, and facilitate the study of the origin and metabolic fate of the endogenously produced compounds observed in breath and skin emanations. Within this study the production and uptake of VOCs by rat L6 skeletal muscle cells were investigated using gas chromatography with mass spectrometric detection, combined with head-space needle trap extraction as the pre-concentration technique (HS-NTE-GC-MS). Seven compounds were found to be produced, whereas sixteen species were consumed (Wilcoxon signed-rank test, p < 0.05) by the cells being studied. The set of released volatiles included two ketones (2-pentanone and 2-nonanone), two volatile sulphur compounds (dimethyl sulfide and methyl 5-methyl-2-furyl sulphide), and three hydrocarbons (2-methyl 1-propene, n-pentane and isoprene). Of the metabolized species there were thirteen aldehydes (2-propenal, 2-methyl 2-propenal, 2-methyl propanal, 2-butenal, 2-methyl butanal, 3-methyl butanal, n-pentanal, 2-methyl 2-butenal, n-hexanal, benzaldehyde, n-octanal, n-nonanal and n-decanal), two esters (n-propyl propionate and n-butyl acetate), and one volatile sulphur compound (dimethyl disulfide). The possible metabolic pathways leading to the uptake and release of these compounds by L6 cells are proposed and discussed. An analysis of the VOCs showed them to have huge potential for the identification and monitoring of some molecular mechanism and conditions. PMID:25307263

Mochalski, Pawe?; Al-Zoairy, Ramona; Niederwanger, Andreas; Unterkofler, Karl; Amann, Anton

2014-01-01

145

Stable Carbon Isotope Ratios and Mixing Ratios of Several VOC Including n-Hexane, Benzene, Toluene, p-Xylene, n-Octane, and n-Decane Measured During the Border Air Quality Study Campaign (June-July, 2007)  

NASA Astrophysics Data System (ADS)

Many important secondary pollutants are formed during the oxidation of Volatile Organic Compounds (VOC) in the atmosphere. These organic compounds can contribute significant mass to atmospheric particulate matter (PM) and therefore impact physical properties and composition of aerosols. Despite numerous studies, the formation processes for atmospheric PM are still not well understood. While there have been very extensive laboratory investigations of PM formation, nearly all of these studies have been conducted at VOC concentrations which exceed ambient atmospheric levels by several orders of magnitude. Consequently there is substantial uncertainty in the extrapolation of laboratory results to the atmosphere. Recently it has been demonstrated that stable carbon isotopic composition measurements can be very valuable in providing increased insight into the chemical and transport processes of VOC in the troposphere. Studies showed that isotope ratio measurements could aid in the determination of photochemical processing of individual VOC. It is expected that applying isotope measurements to studies of VOC oxidation products in the atmosphere will allow to establish quantitative relationship between the amount of precursor oxidized and the concentration of secondary pollutants formed during this process. Thus, the yield of secondary organic aerosols (SOA) from this reaction can be calculated. A cartridge technique was developed for field sampling of VOC and subsequent laboratory analysis by gas chromatography coupled with isotope ratio mass spectrometry. It was first implemented during the BAQS field study (June-July, 2007) parallel to PM sampling. Stable carbon isotopic composition and concentrations of several VOC were determined and compared to those of PM. The results of these measurements will be presented and discussed.

Kornilova, A.; Moukhtar, S.; Huang, L.; Rudolph, J.

2008-12-01

146

Effects of dilution of poly(ethylvinylbenzene-divinylbenzene) adsorbent on the adsorption of aliphatic, alicyclic, and aromatic hydrocarbon adsorbates from effective zero to finite surface coverage  

SciTech Connect

The chromatographic measurement and systematic interpretation of the solidgas partition coefficients K/sub s/ and related thermodynamic properties of a number of hydrocarbon adsorbates (n-pentane through n-octane, cyclohexane, methylcyclohexane, benzene, dichloromethane, chloroform, carbon tetrachloride, tetrahydrofuran, thiophene, and acetone) at effective zero surface coverage with a 1:10 admixture of the title adsorbent-inert diluent from 393 to 443 K are reported. Despite a difference of an order of magnitude in the surface areas of bulk and admixed packings, the adsorbate relative retentions were in good agreement with those found in previous work with neat Porapak Q. The heats of adsorption also coincided to within an experimental error of ca. +- 5%. The GSC technique of elution by characteristic point was then used to derive the finite-concentration adsorption isotherms and isosteric heats of adsorption on n-hexane, cyclohexane, benzene, carbon tetrachloride, and acetone adsorbates with diluted Porapak Q over the temperature range 393-433 K. All exhibited BET Type IV isotherms, as well as changes in the respective isotherm temperature coefficients. The latter is said to be a consequence of the microporous substructure of this adsorbent.

Djordjevic, N.M.; Laub, R.J.

1988-01-15

147

A field-space conformal-solution method: Binary vapor-liquid phase behavior  

NASA Astrophysics Data System (ADS)

The field-space conformal solution method provides an entirely new thermodynamic framework for the description of fluid mixtures in terms of the properties of a pure reference fluid. The utility and performance of the method are examined in the special case of vapor-liquid equilibrium correlation for simple mixtures. This is one of several cases in which field-space methods have numerical or theoretical advantages over methods presently used in mixture property correlation; only properties along the vapor pressure curve of the purefluid reference system are required for a complete description of the mixture phase behavior. Vapor-liquid equilibrium data for three binary hydrocarbon mixtures, n-butane + n-pentane, n-butane + n-hexane, and n-butane + n-octane, are correlated with a simple implementation of the method having two independent mixture parameters. Two pure-fluid equations of state, a Peng-Robinson equation and a 32-constant modified Benedict-Webb-Rubin equation, are tested as reference systems. The effects of differences in the quality of the reference system and of a range of mixture component size ratios are examined.

Storvick, T. S.; Fox, J. R.

1990-01-01

148

Performance of ab initio and density functional methods for conformational equilibria of CnH2n+2 alkane isomers (n=2-8)  

E-print Network

Conformational energies of n-butane, n-pentane, and n-hexane have been calculated at the CCSD(T) level and at or near the basis set limit. Post-CCSD(T) contribution were considered and found to be unimportant. The data thus obtained were used to assess the performance of a variety of density functional methods. Double-hybrid functionals like B2GP-PLYP and B2K-PLYP, especially with a small Grimme-type empirical dispersion correction, are capable of rendering conformational energies of CCSD(T) quality. These were then used as a `secondary standard' for a larger sample of alkanes, including isopentane and the branched hexanes as well as key isomers of heptane and octane. Popular DFT functionals like B3LYP, B3PW91, BLYP, PBE, and PBE0 tend to overestimate conformer energies without dispersion correction, while the M06 family severely underestimates GG interaction energies. Grimme-type dispersion corrections for these overcorrect and lead to qualitatively wrong conformer orderings. All of these functionals also ex...

Gruzman, David; Martin, Jan M L

2009-01-01

149

First Steps in Photophysics. I. Fluorescence Yield and Radiative Rate Coefficient of 9,10-Bis(phenylethynyl)anthracene in Paraffins.  

PubMed

The fluorescence quantum yield of 9,10-bis(phenylethynyl)anthracene (BPEA) is almost unity in every examined solvent. Using different hydrocarbons, one can make a convenient and sufficiently accurate experimental test for determination of the extent of the refractive index correction needed in fluorescence quantum yield determination on a given fluorometer. By comparison of the measurements in n-pentane-cis-decaline or n-hexane-toluene solvent pairs, the requirement of the n(2) correction is confirmed for most of the fluorometers; however, for one of the examined pieces of equipment the necessary correction proved to be slightly lower. By excited state's lifetime measurements, the refractive index dependence of the fluorescence rate coefficient was reexamined. At 25 °C for BPEA the relationship is in agreement with Bakhshiev's prediction: the experimentally determined exponent of n in the rate coefficient deriving equation is around 1.32 using different paraffins as solvents. The negative temperature coefficient of the radiative rate in part originates from the temperature dependence of the refractive index, while also a small intrinsic contribution has been found. PMID:25296291

Demeter, Attila

2014-10-30

150

Biodegradation of petroleum hydrocarbon vapors: laboratory studies on rates and kinetics in unsaturated alluvial sand  

NASA Astrophysics Data System (ADS)

Predictions of natural attenuation of volatile organic compounds (VOCs) in the unsaturated zone rely critically on information about microbial biodegradation kinetics. This study aims at determining kinetic rate laws for the aerobic biodegradation of a mixture of 12 volatile petroleum hydrocarbons and methyl tert-butyl ether (MTBE) in unsaturated alluvial sand. Laboratory column and batch experiments were performed at room temperature under aerobic conditions, and a reactive transport model for VOC vapors in soil gas coupled to Monod-type degradation kinetics was used for data interpretation. In the column experiment, an acclimatization of 23 days took place before steady-state diffusive vapor transport through the horizontal column was achieved. Monod kinetic parameters Ks and vmax could be derived from the concentration profiles of toluene, m-xylene, n-octane, and n-hexane, because substrate saturation was approached with these compounds under the experimental conditions. The removal of cyclic alkanes, isooctane, and 1,2,4-trimethylbenzene followed first-order kinetics over the whole concentration range applied. MTBE, n-pentane, and chlorofluorocarbons (CFCs) were not visibly degraded. Batch experiments suggested first-order disappearance rate laws for all VOCs except n-octane, which decreased following zero-order kinetics in live batch experiments. For many compounds including MTBE, disappearance rates in abiotic batch experiments were as high as in live batches indicating sorption. It was concluded that the column approach is preferable for determining biodegradation rate parameters to be used in risk assessment models.

Höhener, Patrick; Duwig, Céline; Pasteris, Gabriele; Kaufmann, Karin; Dakhel, Nathalie; Harms, Hauke

2003-10-01

151

Modeling VOC Sorption and Transport in Glassy Polymeric Membranes  

NASA Astrophysics Data System (ADS)

In this work we evaluated the sorption, diffusion and permeation of a series of volatile organic compounds (VOCs) (acetone, n-butane, n-pentane, n-hexane, ethanol, methanol, chloroform and toluene) into glassy polymers of increasing fractional free volume (FFV): Polycarbonate (PC), Amorphous Teflon AF1600 and AF2400, poly-trimethylsilyl norbornene (PTMSN) and poly[1-(trimethylsilyl)-1-propyne] (PTMSP). Based on some experimental data of sorption and diffusion, and on theoretical and empirical models for the solubility and diffusion coefficients, the permeability for vapor/N2 mixtures was evaluated. These parameters are useful for the membrane separation processes and for other applications such as chemical sensors. The ideal separation factors of glassy polymeric membranes versus mixtures of VOCs and N2 were estimated at various pressures and compositions and at 25° C. The selectivity vs. permeability maps for the mixtures considered were plotted, showing that some of these materials show potentially the same selective ability of rubbery polymeric films. In particular it is shown that, the higher the FFV, the better the vapor/gas selectivity.

De Angelis, Maria Grazia; Olivieri, Luca; Sarti, G. C.

2010-06-01

152

Lactic fermentation to improve the aroma of protein extracts of sweet lupin (Lupinus angustifolius).  

PubMed

Lupin protein extracts (LPE) are prone to the emission of a beany off-flavour during storage, which confines its application in foods. Fermentation of LPE using several lactic acid bacteria was conducted to reduce off-flavour formation in stored samples. The aroma profile of untreated LPE was compared to those of fermented protein extracts (LPEF). Hexanal and n-hexanol were used as indicator substances of progressing lipid oxidation. The most powerful odourants were evaluated by GC-olfactometry-flavour dilution analysis and identified according to their mass spectra, odour descriptions, and retention indices. Twenty two volatile substances with dilution factors equal to or higher than 100 were determined in both LPE and LPEF, amongst them n-pentanal, n-hexanal, 1-pyrroline, dimethyl trisulfide, 1-octen-3-one, 3-octen-2-one, 1-octen-3-ol, and ?-damascenone. The aroma profile was significantly modified by the fermentation process and the off-flavours were reduced and/or masked by newly formed compounds. PMID:25212139

Schindler, Sabrina; Wittig, Maximilian; Zelena, Kateryna; Krings, Ulrich; Bez, Jürgen; Eisner, Peter; Berger, Ralf G

2011-09-15

153

n-Aldehydes (C6-C10) in snow samples collected at the high alpine research station Jungfraujoch during CLACE 5  

NASA Astrophysics Data System (ADS)

Samples of freshly fallen snow were collected at the high alpine research station Jungfraujoch, Switzerland, during the Cloud and Aerosol Characterization Experiments (CLACE) 5 in February and March 2006. Sampling was carried out on the Sphinx platform. Headspace-solid-phase-dynamic extraction (HS-SPDE) combined with gas chromatography/mass spectrometry (GC/MS) was used to quantify C6-C10 n-aldehydes in the snow samples. The most abundant n-aldehyde was n-hexanal (median concentration 1.324 ?g L-1) followed by n-nonanal, n-decanal, n-octanal and n-heptanal (median concentrations 1.239, 0.863, 0.460, and 0.304 ?g L-1, respectively). A wide range of concentrations was found among individual snow samples, even for samples taken at the same time. Higher median concentrations of all n-aldehydes were observed when air masses reached Jungfraujoch from the north-northwest in comparison to air masses arriving from the southeast-southwest. Results suggest that the n-aldehydes detected most likely are of direct and indirect biogenic origin, and that they entered the snow through the particle phase.

Sieg, K.; Starokozhev, E.; Fries, E.; Sala, S.; Püttmann, W.

2009-03-01

154

Molecular-dynamics simulation of mutual diffusion in nonideal liquid mixtures  

NASA Astrophysics Data System (ADS)

The mutual-diffusion coefficients, D 12, of n-hexane, n-heptane, and n-octane in chloroform were modeled using equilibrium molecular-dynamics (MD) simulations of simple Lennard-Jones (LJ) fluids. Pure-component LJ parameters were obtained by comparison of simulations to experimental self-diffusion coefficients. While values of “effective” LJ parameters are not expected to simulate accurately diverse thermophysical properties over a wide range of conditions, it was recently shown that effective parameters obtained from pure self-diffusion coefficients can accurately model mutual diffusion in ideal, liquid mixtures. In this work, similar simulations are used to model diffusion in nonideal mixtures. The same combining rules used in the previous study for the cross-interaction parameters were found to be adequate to represent the composition dependence of D 12. The effect of alkane chain length on D 12 is also correctly predicted by the simulations. A commonly used assumption in empirical correlations of D 12, that its kinetic portion is a simple, compositional average of the intradiffusion coefficients, is inconsistent with the simulation results. In fact, the value of the kinetic portion of D 12 was often outside the range of values bracketed by the two intradiffusion coefficients for the nonideal system modeled here.

Rowley, R. L.; Stoker, J. M.; Giles, N. F.

1991-05-01

155

Biodiesel production using waste frying oil  

SciTech Connect

Research highlights: {yields} Waste sunflower frying oil is successfully converted to biodiesel using lipase as catalyst. {yields} Various process parameters that affects the conversion of transesterification reaction such as temperature, enzyme concentration, methanol: oil ratio and solvent are optimized. {yields} Inhibitory effect of methanol on lipase is reduced by adding methanol in three stages. {yields} Polar solvents like n-hexane and n-heptane increases the conversion of tranesterification reaction. - Abstract: Waste sunflower frying oil is used in biodiesel production by transesterification using an enzyme as a catalyst in a batch reactor. Various microbial lipases have been used in transesterification reaction to select an optimum lipase. The effects of various parameters such as temperature, methanol:oil ratio, enzyme concentration and solvent on the conversion of methyl ester have been studied. The Pseudomonas fluorescens enzyme yielded the highest conversion. Using the P. fluorescens enzyme, the optimum conditions included a temperature of 45 deg. C, an enzyme concentration of 5% and a methanol:oil molar ratio 3:1. To avoid an inhibitory effect, the addition of methanol was performed in three stages. The conversion obtained after 24 h of reaction increased from 55.8% to 63.84% because of the stage-wise addition of methanol. The addition of a non-polar solvent result in a higher conversion compared to polar solvents. Transesterification of waste sunflower frying oil under the optimum conditions and single-stage methanol addition was compared to the refined sunflower oil.

Charpe, Trupti W. [Chemical Engineering Department, Institute of Chemical Technology, Matunga, Mumbai 400 019 (India); Rathod, Virendra K., E-mail: vk.rathod@ictmumbai.edu.in [Chemical Engineering Department, Institute of Chemical Technology, Matunga, Mumbai 400 019 (India)

2011-01-15

156

Enhancement of the spectral selectivity of complex samples by measuring them in a frozen state at low temperatures in order to improve accuracy for quantitative analysis. Part I. Raman spectroscopic compositional analysis of synthetic hydrocarbon mixtures.  

PubMed

A simple strategy for enhancing the Raman spectral selectivity of complex mixture samples by measuring them in a frozen state at low temperatures has been demonstrated and proven to improve the accuracy for compositional analysis. For evaluation, the Raman spectra of synthetic hydrocarbon mixtures that were composed of eleven hydrocarbons (n-hexane, n-heptane, n-octane, n-nonane, isooctane, cyclohexane, methylcyclohexane, benzene, toluene, xylene, and indan) were continuously collected during the elevation of their temperature from cryogenic to near room temperature. The accuracy of determination of n-paraffin concentrations improved significantly when the samples were measured at the temperature range between approximately -175 and -155 °C in comparison to the measurements at room temperature. However, the improvement of accuracy was relatively marginal for the concentration determination of naphthenic and aromatic components. Since n-paraffins are easily compressible and deformable in frozen conditions, the subsequent spectral variations could be diverse depending on their molecular structures. Due to this fact, the spectral discrimination among the paraffin components, as well as in comparison to other components, was enhanced and the improved spectral selectivity eventually led to more accurate determination of concentrations. Overall, the proposed strategy is simple and effective, so it is applicable for analysis of real complex mixture samples. PMID:23340768

Hwang, Jinyoung; Chung, Hoeil

2013-03-01

157

[Cloning and expression of organic solvent tolerant lipase gene from Staphylococcus saprophyticus M36].  

PubMed

Lipases are important biocatalysts that are widely used in food processing and bio-diesel production. However, organic solvents could inactivate some lipases during applications. Therefore, the efficient cloning and expression of the organic solvent-tolerant lipase is important to its application. In this work, we first found out an organic solvent-tolerant lipase from Staphylococcus saprophyticus M36 and amplified the 741 bp Lipase gene lip3 (GenBank Accession No. FJ979867), by PCR, which encoded a 31.6 kD polypeptide of 247 amino acid residues. But the lipase shared 83% identity with tentative lip3 gene of Staphylococcus saprophyticus (GenBank Accession No. AP008934). We connected the gene with expression vector pET-DsbA, transformed it into Escherichia coli BL21 (DE3), and obtained the recombinant pET-DsbA-lip3. With the induction by 0.4 mmol/L of isopropyl beta-D-thiogalactopyranoside at pH 8.0, OD600 1.0, 25 degrees C for 12 h, the lipase activity reached up to 25.8 U/mL. The lipase expressed was stable in the presence of methanol, n-hexane, and isooctane, n-heptane. PMID:20352979

Tang, Yanchong; Lu, Yaping; Lü, Fengxia; Bie, Xiaomei; Guo, Yao; Lu, Zhaoxin

2009-12-01

158

Testing of the abiotic degradation of chemicals in the atmosphere: the smog chamber approach  

SciTech Connect

Methods for measuring the hydroxyl-, ozone-, and direct photochemical reactivity of a substance in one specially designed medium size smog chamber are described. Rate coefficients for the reaction of OH with n-hexane, n-heptane, ethene, ethyne, chloroform, trichloroethene, methanol, 2-propanol, benzene, o-xylene, 1,4-dichlorobenzene, 1,2,4-trichlorobenzene, p-chloroaniline, naphthalene, acenaphthene, 1,4-dichloronaphthalene, biphenyl, and fluorenone are given and discussed. An upper limit of 5 X 10(-13) cm3/sec is given for the sum penta- and hexa-chlorobiphenyls (PCB). Rate coefficients for the ozone reaction are given for beta-pinene, limonene, delta 3-carene, cineol, vinyl chloride and 1,3-butadiene. In cases where the literature data are available for comparison, the rate coefficients (kappa OH and kappa O3) reported here compare favorably with the best data reported. The direct photochemical reactivity has been shown to be measurable if the chamber is cleaned carefully. Preliminary results on benzophenone are reported. The methods described here, except that of direct photochemical reactivity, are in agreement with those proposed to OECD. Moreover, part of the Draft OECD Test Guideline (Berlin, 1987) on Photochemical-Oxidative Degradation in the Atmosphere is based on work described here and on closely related work in other laboratories.

Kloepffer, W.H.; Haag, F.; Kohl, E.G.; Frank, R.

1988-06-01

159

Monitoring of Selected Skin-Borne Volatile Markers of Entrapped Humans by Selective Reagent Ionization Time of Flight Mass Spectrometry in NO+ Mode  

PubMed Central

Selective reagent ionization time-of-flight mass spectrometry with NO+ as the reagent ion (SRI-TOF-MS (NO+)) was applied for near real-time monitoring of selected skin-borne constituents which are potential markers of human presence. The experimental protocol involved a group of 10 healthy volunteers enclosed in a body plethysmography chamber mimicking the entrapment environment. A total of 12 preselected omnipresent in human scent volatiles were quantitatively monitored. Among them there were six aldehydes (n-propanal, n-hexanal, n-heptanal, n-octanal, n-nonanal, and 2 methyl 2-propenal), four ketones (acetone, 2-butanone, 3-buten-2-one, and 6-methyl-5-hepten-2-one), one hydrocarbon (2-methyl 2-pentene), and one terpene (DL-limonene). The observed median emission rates ranged from 0.28 to 44.8 nmol × person–1 × min–1 (16–1530 fmol × cm–2 × min–1). Within the compounds under study, ketones in general and acetone in particular exhibited the highest abundances. The findings of this study provide invaluable information about formation and evolution of a human-specific chemical fingerprint, which could be used for the early location of entrapped victims during urban search and rescue operations (USaR). PMID:24611620

2014-01-01

160

Transferable Potentials for Phase Equilibria. 4. United-Atom Description of Linear and Branched Alkenes and Alkylbenzenes  

SciTech Connect

The Transferable Potentials for Phase Equilibria-United Atom (TraPPE-UA) force field for hydrocarbons is extended to alkenes and alkylbenzenes by introducing the following pseudo-atoms: CH{sub 2}(sp{sup 2}), CH(sp{sup 2}), CH(aro), R-C(aro) for the link to aliphatic side chains, and C(aro) for the link of two benzene rings. In this united-atom force field, the nonbonded interactions of the hydrocarbon pseudo-atoms are solely governed by Lennard-Jones 12-6 potentials, and the Lennard-Jones well depth and size parameters for the new pseudo-atoms were determined by fitting to the single-component vapor-liquid phase equilibria of a few selected model compounds. Configurational-bias Monte Carlo simulations in the NVT version of the Gibbs ensemble were carried out to calculate the single-component vapor-liquid coexistence curves for ethene, propene, 1-butene, trans- and cis-2-butene. 2-methylpropene, 1,5-hexadiene, 1-octene, benzene, toluene, ethylbenzene, propylbenzene, isopropylbenzene, o-, m-, and p-xylene, and naphthalene. The phase diagrams for the binary mixtures of (supercritical) ethene/n-heptane and benzene/n-pentane were determined from simulations in the NpT Gibbs ensemble. Although the TraPPE-UA force field is rather simple and makes use of relatively few different pseudo-atoms, its performance, as judged by comparisons to other popular force fields and available experimental data, is very satisfactory.

WICK,COLLIN D.; MARTIN,MARCUS G.; SIEPMANN,J. ILJA

2000-07-12

161

Thermochemistry of C7H16 to C10H22 Alkane Isomers: Primary, Secondary, and Tertiary C-H Bond Dissociation Energies and Effects of Branching.  

PubMed

Standard enthalpies of formation (?H°f 298) of methyl, ethyl, primary and secondary propyl, and n-butyl radicals are evaluated and used in work reactions to determine internal consistency. They are then used to calculate the enthalpy of formation for the tert-butyl radical. Other thermochemical properties including standard entropies (S°(T)), heat capacities (Cp(T)), and carbon-hydrogen bond dissociation energies (C-H BDEs) are reported for n-pentane, n-heptane, 2-methylhexane, 2,3-dimethylpentane, and several branched higher carbon number alkanes and their radicals. ?H°f 298 and C-H BDEs are calculated using isodesmic work reactions at the B3LYP (6-31G(d,p) and 6-311G(2d,2p) basis sets), CBS-QB3, CBS-APNO, and G3MP2B3 levels of theory. Structures, moments of inertia, vibrational frequencies, and internal rotor potentials are calculated at the B3LYP/6-31G(d,p) level for contributions to entropy and heat capacities. Enthalpy calculations for these hydrocarbon radical species are shown to have consistency with the CBS-QB3 and CBS-APNO methods using all work reactions. Our recommended ideal gas phase ?H°f 298 values are from the average of all CBS-QB3, CBS-APNO, and for G3MP2B3, only where the reference and target radical are identical types, and are compared with literature values. Calculated values show agreement between the composite calculation methods and the different work reactions. Secondary and tertiary C-H bonds in the more highly branched alkanes are shown to have bond energies that are several kcal mol(-1) lower than the BDEs in corresponding smaller molecules often used as reference species. Entropies and heat capacities are calculated and compared to literature values (when available) when all internal rotors are considered. PMID:25180943

Hudzik, Jason M; Bozzelli, Joseph W; Simmie, John M

2014-10-01

162

Determination of vapor liquid equilibrium for the ternary iso-propanol/atactic-polypropylene/n-heptane mixture at 105C and 140C, and the binary iso-propanol/atactic-polypropylene mixture at 85C using perturbation gas chromatography / cby Lamar Lane Joffrion  

E-print Network

by the perturbation, are sufficiently small to allow equation linearization as assumed in the theoretical development. The other assumptions of the theory are also reflected in the experimental conditions. A mechanical vibrator was used to help pack the column... on the basis of random molecular mixing, do not predict well the thermodynamic properties of the IPA/APP system when considering orientation effects arising from the IPA molecular polarity. The hydrogen bonds existing between IPA molecules tend to cause...

Joffrion, Lamar Lane

2012-06-07

163

Vapor pressure, heat capacity, and density along the saturation line, measurements for cyclohexanol, 2-cyclohexen-1-one, 1,2-dichloropropane, 1,4-di-tert-butylbenzene, ({+-})-2-ethylhexanoic acid, 2-(methylamino)ethanol, perfluoro-n-heptane, and sulfolane  

SciTech Connect

Vapor pressures were measured to a pressure limit of 270 kPa or lower decomposition point for eight compounds using a twin ebulliometric apparatus. Liquid-phase densities along the saturation line were measured for each compound over a range of temperatures (ambient to a maximum of 548 K). A differential scanning calorimeter (DSC) was used to measure two-phase (liquid + vapor) heat capacities for each compound in the temperature region ambient to the critical temperature or lower decomposition point. Where possible, the critical temperature and critical density for each compound were determined experimentally. The results of the measurements were combined to derive a series of thermophysical properties including critical temperature, critical density, critical pressure, acentric factor, enthalpies of vaporization [within the temperature range ({+-}50 K) of the vapor pressures], enthalpies of fusion if solid at ambient temperature, solubility parameter, and heat capacities along the saturation line. Wagner-type vapor-pressure equations were derived for each compound. In addition, the liquid-phase densities were compared with values derived using a four-term power series in either T or [(1 {minus} T{sub r}){sup 1/3}]. All measured and derived values were compared with those obtained in a search of the literature. Recommended critical parameters are listed for each of the compounds studied. A Rule-Of-Thumb derived in the 1992 Project Year was used to estimate thermal decomposition temperatures by radical scission from a knowledge of the bond dissociation energy or vice versa.

Steele, W.V.; Chirico, R.D.; Knipmeyer, S.E.; Nguyen, A. [National Inst. for Petroleum and Energy Research, Bartlesville, OK (United States)] [National Inst. for Petroleum and Energy Research, Bartlesville, OK (United States)

1997-11-01

164

Vapor pressure, heat capacity, and density along the saturation line, measurements for cyclohexanol, 2-cyclohexen-1-one, 1,2-dichloropropane, 1,4-di-tert-butylbenzene, ({+-})-2-ethylhexanoic acid, 2-(methylamino)ethanol, perfluoro-n-heptane, and sulfolane  

Microsoft Academic Search

Vapor pressures were measured to a pressure limit of 270 kPa or lower decomposition point for eight compounds using a twin ebulliometric apparatus. Liquid-phase densities along the saturation line were measured for each compound over a range of temperatures (ambient to a maximum of 548 K). A differential scanning calorimeter (DSC) was used to measure two-phase (liquid + vapor) heat

W. V. Steele; R. D. Chirico; S. E. Knipmeyer; A. Nguyen

1997-01-01

165

n-Aldehydes (C6-C10) in snow samples collected at the high alpine research station Jungfraujoch during CLACE 5  

NASA Astrophysics Data System (ADS)

C6-C10 n-aldehydes were analyzed in samples of freshly fallen snow collected at the high alpine research station Jungfraujoch, Switzerland, during the Cloud and Aerosol Characterization Experiments (CLACE) 5 in February and March 2006. Sampling was carried out on the Sphinx platform. Headspace - solid phase dynamic extraction (HS-SPDE) combined with gas chromatography/mass spectrometry (GC/MS) was used to quantify n-aldehydes in melted snow samples. n-Hexanal was identified as the most abundant n-aldehyde (median concentration 1.324 µg L-1) followed by n-nonanal, n-decanal, n-octanal and n-heptanal (median concentrations 1.239, 0.863, 0.460 and 0.304 µg L-1, respectively). A wide range of concentrations of n-aldehydes was found in snow samples from Jungfraujoch, even for samples collected at the same time during the same snowfall event. According to their physical and chemical characteristics, n-aldehydes are expected to be primarily linked to aerosol particles in the atmosphere suggesting the uptake of n-aldehydes into snow via the particle phase. Particle scavenging can occur during snow formation in clouds. The high concentration variations of the n-aldehydes among the snow samples can be explained assuming that aerosol particles, which are loaded with n-aldehydes, are heterogeneously distributed throughout the snow samples. Higher median concentrations of all n-aldehydes were observed when air masses reached Jungfraujoch from the north-northwest in comparison to air masses arriving from the southeast-southwest. The sources of atmospheric n-aldehydes present at Jungfraujoch are most likely to be related to direct and indirect biogenic emissions. The presence of n-aldehydes as semivolatile constituents of direct biogenic emissions from vegetation has been reported previously in studies of Ciccioli et al. [1], Yokouchi et al. [2] and Kesselmeier and Staudt [3]. The distribution pattern of the n-aldehydes in emissions from vegetation largely matches with the n-aldehyde pattern found in snow collected at Jungfraujoch. One exception is the significantly higher proportion of n-hexanal in the Jungfraujoch samples compared to vegetation emission. Additionally, indirect biogenic emissions can contribute to the atmospheric concentrations of n-aldehydes through oxidation of precursor compounds of biogenic origin. In this context, Moise and Rudich [4] and Thornberry and Abbatt [5] proposed the preferential formation of n-nonanal and n-hexanal from the cleavage by ozonolysis of double bonds in unsaturated fatty acids (namely oleic acid and linoleic acids). The predominance of n-hexanal and n-nonanal among the C6-C10 n-aldehydes in the snow samples collected at Jungfraujoch during CLACE 5 is therefore an argument for the formation of the aldehydes through oxidation of unsaturated fatty acids in the atmosphere. Anthropogenic emissions of n-aldehydes i.e. from fossil fuel burning are thought to be negligible in the air masses reaching Jungfraujoch. References: [1] P. Ciccioli, E. Brancaleoni, M. Frattoni, A. Cecinato, A. Brachetti, Atmos. Environ., Part A 27 (1993) 1891. [2] Y. Yokouchi, H. Mukai, K. Nakajima, Y. Ambe, Atmos. Environ., Part A 24 (1990) 439. [3] J. Kesselmeier, M. Staudt, J. Atmos. Chem. 33 (1999) 23. [4] T. Moise, Y. Rudich, J. Phys. Chem. 106 (2002) 6469. [5] T. Thornberry, J.P.D. Abbatt, Phys. Chem. Chem. Phys. 6 (2004) 84.

Sieg, K.; Starokozhev, E.; Fries, E.; Sala, S.; Püttmann, W.

2009-04-01

166

KEY COMPARISON: International Comparison CCQM-K16: Composition of natural gas types IV and V  

NASA Astrophysics Data System (ADS)

Natural gas is an important energy vector. The determination of its composition is often used as the basis for the calculation of the calorific value. The calorific value in turn is one of the two key parameters used in natural gas trade. In the first series of key comparisons (CCQM-K1e-g), natural gas was already included with three different compositions. These mixtures contained carbon dioxide, nitrogen, ethane, propane and n-butane in methane (matrix) and were only to a limited extent representative of real natural gas. In the past years, national metrology institutes have broadened the range of components by including, e.g., i-butane, neo-pentane, n-pentane, i-pentane and n-hexane. Based on this extended components list, two new mixtures have been defined, one characteristic for a low calorific mixture (type IV) and the other for a high calorific mixture (type V). In the low calorific mixture, helium was also present. Due to presence of the butane and pentane isomers, the mixtures of type IV and V are more demanding with respect to the separation technique than the mixtures used in CCQM-K1e-g. The measurements in this key comparison took place in 2001. There were eight participants and two coordinating laboratories. The key comparison reference value (KCRV) was based on the gravimetric preparation for all components. Even for the heavier hydrocarbons (pentanes and n-hexane) the effects of, e.g., adsorption can be controlled to such an extent that this approach is still valid. The uncertainty evaluation of the KCRVs reflected also the extent to which the preparation data could be demonstrated to be valid. The validity of the preparation data was demonstrated by comparing the composition of the mixtures prepared for this comparison with measurement standards maintained by the coordinating laboratories. The key comparisons demonstrated that the results of the laboratories agreed within 1% relative to the reference value for most components. Even better agreement was obtained for nitrogen in the low calorific mixture (0.5%), carbon dioxide (0.5%), ethane (0,5%), propane (0.5%) and methane (0.1%). In some cases, larger differences were observed, which then also exceeded the associated expanded uncertainty Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the Mutual Recognition Arrangement (MRA).

van der Veen, Adriaan M. H.; Heine, Hans-Joachim; Brinkmann, Freek N. C.; Ziel, Paul R.; de Leer, Ed W. B.; Zhen, Wang Lin; Kato, Kenji; Konopelko, Leonid A.; Popova, Tatjana A.; Alexandrov, Yuri I.; Kortchagina, Elena N.; Kustikov, Yuri A.; Musil, Stanislav; Milton, Martin J. T.; Guenther, Franklin; Rhoderick, George

2005-01-01

167

Temporal variation of volatile organic compounds and their major emission sources in Seoul, Korea.  

PubMed

This study examines the characteristics of volatile organic compounds (VOCs) and their major emission sources at the Bulgwang site in Seoul, Korea. The annual levels of VOCs (96.2-121.1 ppb C) have shown a decreasing trend from 2004 to 2008. The most abundant component in Seoul was toluene, which accounted for over 23.5 % of the total VOCs on the parts per billion on a carbon basis, and the portions of alkanes with two to six carbons constituted the largest major lumped group, ranging from 40.1 to 48.4 % (45.3 ± 3.7 %) of the total VOCs. Major components of the solvent (toluene, m/p-xylene, o-xylene, and ethylbenzene) showed high in daytime and summer and low in nighttime and winter due mainly to the variation of the ambient temperature. The species mostly emitted from gasoline vapor (i/n-butane, i/n-pentane, n-hexane, and 2-methylpentane) and vehicular exhaust (ethylene, acetylene, and benzene) showed bimodal peaks in the diurnal variation around the commuting hours because of the high traffic volume. For the 14 out of 15 highest concentration species, the weekend effect was only evident on Sundays because of the stepwise implementation of the 5-day work-week system. Principal components analysis (PCA) was applied in order to identify the sources of the 15 highest concentration VOCs and, as a result, three principal components such as gasoline vapor (48.9 %), vehicular exhaust (17.9 %), and evaporation of solvents (9.8 %) were obtained to explain a total of 76.6 % of the data variance. Most influential contributing sources at the sampling site were traffic-related ones although the use of solvent was the dominant emission source based on the official emission inventory. PMID:23728967

Shin, H J; Roh, S A; Kim, J C; Lee, S J; Kim, Y P

2013-12-01

168

Molecular dynamics averaging of Xe chemical shifts in liquids.  

PubMed

The Xe nuclear magnetic resonance chemical shift differences that afford the discrimination between various biological environments are of current interest for biosensor applications and medical diagnostic purposes. In many such environments the Xe signal appears close to that in water. We calculate average Xe chemical shifts (relative to the free Xe atom) in solution in eleven liquids: water, isobutane, perfluoro-isobutane, n-butane, n-pentane, neopentane, perfluoroneopentane, n-hexane, n-octane, n-perfluorooctane, and perfluorooctyl bromide. The latter is a liquid used for intravenous Xe delivery. We calculate quantum mechanically the Xe shielding response in Xe-molecule van der Waals complexes, from which calculations we develop Xe (atomic site) interpolating functions that reproduce the ab initio Xe shielding response in the complex. By assuming additivity, these Xe-site shielding functions can be used to calculate the shielding for any configuration of such molecules around Xe. The averaging over configurations is done via molecular dynamics (MD). The simulations were carried out using a MD technique that one of us had developed previously for the simulation of Henry's constants of gases dissolved in liquids. It is based on separating a gaseous compartment in the MD system from the solvent using a semipermeable membrane that is permeable only to the gas molecules. We reproduce the experimental trends in the Xe chemical shifts in n-alkanes with increasing number of carbons and the large chemical shift difference between Xe in water and in perfluorooctyl bromide. We also reproduce the trend for a given solvent of decreasing Xe chemical shift with increasing temperature. We predict chemical shift differences between Xe in alkanes vs their perfluoro counterparts. PMID:15538880

Jameson, Cynthia J; Sears, Devin N; Murad, Sohail

2004-11-15

169

Molecular dynamics averaging of Xe chemical shifts in liquids  

NASA Astrophysics Data System (ADS)

The Xe nuclear magnetic resonance chemical shift differences that afford the discrimination between various biological environments are of current interest for biosensor applications and medical diagnostic purposes. In many such environments the Xe signal appears close to that in water. We calculate average Xe chemical shifts (relative to the free Xe atom) in solution in eleven liquids: water, isobutane, perfluoro-isobutane, n-butane, n-pentane, neopentane, perfluoroneopentane, n-hexane, n-octane, n-perfluorooctane, and perfluorooctyl bromide. The latter is a liquid used for intravenous Xe delivery. We calculate quantum mechanically the Xe shielding response in Xe-molecule van der Waals complexes, from which calculations we develop Xe (atomic site) interpolating functions that reproduce the ab initio Xe shielding response in the complex. By assuming additivity, these Xe-site shielding functions can be used to calculate the shielding for any configuration of such molecules around Xe. The averaging over configurations is done via molecular dynamics (MD). The simulations were carried out using a MD technique that one of us had developed previously for the simulation of Henry's constants of gases dissolved in liquids. It is based on separating a gaseous compartment in the MD system from the solvent using a semipermeable membrane that is permeable only to the gas molecules. We reproduce the experimental trends in the Xe chemical shifts in n-alkanes with increasing number of carbons and the large chemical shift difference between Xe in water and in perfluorooctyl bromide. We also reproduce the trend for a given solvent of decreasing Xe chemical shift with increasing temperature. We predict chemical shift differences between Xe in alkanes vs their perfluoro counterparts.

Jameson, Cynthia J.; Sears, Devin N.; Murad, Sohail

2004-11-01

170

[Characterization of surface properties of 1-allyl-3-methylimidazolium chloride ionic liquid by inverse gas chromatography].  

PubMed

The determination of the dispersive component of surface free energies (gamma(s)d) at different temperatures and Lewis acid-base parameters of 1-allyl-3-methylimidazolium chloride ionic liquid ([AMIM]Cl) were investigated by means of inverse gas chromatography (IGC). Four n-alkanes, including n-hexane (C6), n-heptane (C7), n-octane (C8) and n-nonane (C9), were chosen as the apolar probes to characterize the dispersive component of the surface free energies at 343.15, 353.15, 363.15 and 373.15 K, respectively; and dichloromethane (DCM), trichloromethane (TCM), tetrahydrofuran (THF), ethyl acetate (EtAc), acetone (Acet) as the polar probes to estimate the Lewis acid-base parameters to judge the interactions between [AMIM] Cl and the solvents. The IGC characterizations encompassed the adsorption thermodynamic parameters to acid-base surface interactions, including the standard enthalpy (deltaHa(s)) and the free energy change of adsorption (deltaGa(s)) at different temperatures. The results showed that the Lewis acid parameter Ka of [AMIM] Cl was 0.34, and the base parameter Kb was 1.68, which indicated it was Lewis amphoteric with predominantly basic character. Furthermore, the free energy of adsorption deltaGa(s) was also figured out. It was found that the gamma(s)d of the [AMIM] Cl were 52.26, 50.82, 46.08 and 42.05 mJ/m2 at 343.15, 353.15, 363.15 and 373.15 K, respectively. The results are of great importance to the study of the surface properties and the application of ionic liquid. PMID:23697180

Chen, Yali; Wang, Qiang; Deng, Lishuang; Zhang, Zhengfang; Tang, Jun

2013-02-01

171

Phase equilibria study of the binary systems (N-hexylisoquinolinium thiocyanate ionic liquid + organic solvent or water).  

PubMed

Liquid-liquid phase equilibria (LLE) of binary mixtures containing a room-temperature ionic liquid N-hexylisoquinolinium thiocyanate, [HiQuin][SCN] with an aliphatic hydrocarbon (n-hexane, n-heptane), aromatic hydrocarbon (benzene, toluene, ethylbenzene, n-propylbenzene), cyclohexane, thiophene, water, and 1-alcohol (1-ethanol, 1-butanol, 1-hexanol, 1-octanol, 1-decanol) have been determined using a dynamic method from room temperature to the boiling-point of the solvent at ambient pressure. N-hexylisoquinolinium thiocyanate, [HiQuin][SCN] has been synthesized from N-hexyl-isoquinolinium bromide as a substrate. Specific basic characterization of the new compound including NMR spectra, elementary analysis, and water content have been done. The density and viscosity of pure ionic liquid were determined over a wide temperature range from 298.15 to 348.15 K. The mutual immiscibility with an upper critical solution temperature (UCST) for the binary systems {IL + aliphatic hydrocarbon, cyclohexane, or water} was detected. In the systems of {IL + aromatic hydrocarbon or thiophene} an immiscibility gap with a lower critical solution temperature (LCST) was observed. Complete miscibility in the liquid phase, over a whole range of ionic liquid mole fraction, was observed for the binary mixtures containing IL and an 1-alcohol. For the tested binary systems with immiscibility gap {IL + aliphatic hydrocarbon, aromatic hydrocarbon, cyclohexane, thiophene, or water}, the parameters of the LLE correlation have been derived using the NRTL equation. The basic thermal properties of the pure IL, that is, the glass-transition temperature as well as the heat capacity at the glass-transition temperature, have been measured using a differential scanning microcalorimetry technique (DSC). Decomposition of the IL was detected by simultaneous thermogravimetric/differential thermal analysis (TG/DTA) experiments. PMID:22424076

Królikowska, Marta; Karpi?ska, Monika; Zawadzki, Maciej

2012-04-12

172

INFLUENCE OF EGR COMPOUNDS ON THE OXIDATION OF AN HCCI-DIESEL SURROGATE  

E-print Network

INFLUENCE OF EGR COMPOUNDS ON THE OXIDATION OF AN HCCI-DIESEL SURROGATE J.M. ANDERLOHR*1,3 , A oxides (NOx), while the principle of CI assures a high efficiency close to that of a diesel engine comprehensively assessed [4]. A n-heptane/toluene mixture was used as a diesel surrogate with n-heptane having

Paris-Sud XI, Université de

173

Pollutant Emissions from Gasoline Combustion. 1. Dependence on Fuel  

E-print Network

predictions of species concentrations in premixed flames of n-heptane, isooctane, benzene, cyclohexane-heptane and isooctane, since paraffins are the dominant constituents of gasoline and kinetic data are readily available fractions that are analytically identifi- able in gasoline fuels, which includes n-heptane (3­5), isooctane

Utah, University of

174

Effects of biomass burning on summertime nonmethane hydrocarbon concentrations in the Canadian wetlands  

NASA Technical Reports Server (NTRS)

Approximately 900 whole air samples were collected and assayed for selected C2-C10 hydrocarbons and seven halocarbons during the 5-week Arctic Boundary Layer Expedition (ABLE) 3B conducted in eastern Canadian wetland areas. In more than half of the 46 vertical profiles flown, enhanced nonmethane hydrocarbon (NMHC) concentrations attributable to plumes from Canadian forest fires were observed. Urban plumes, also enhanced in many NMHCs, were separately identified by their high correlation with elevated levels of perchloroethene. Emission factors relative to ethane were determined for 21 hydrocarbons released from Canadian biomass burning. Using these data for ethane, ethyne, propane, n-butane, and carbon monoxide enhancements from the literature, global emissions of these four NMHCs were estimated. Because of its very short atmospheric lifetime and its below detection limit background mixing ratio, 1,3-butadiene is an excellent indicator of recent combustion. No statistically significant emissions of nitrous oxide, isoprene, or CFC 12 were observed in the biomass-burning plumes encountered during ABLE 3B. The presence of the short-lived biogenically emitted isoprene at altitudes as high as 3000 m implies that mixing within the planetary boundary layer (PBL) was rapid. Although background levels of the longer-lived NMHCs in this Canadian region increase during the fire season, isoprene still dominated local hydroxyl radical photochemistry within the PBL except in the immediate vicinity of active fires. The average biomass-burning emission ratios for hydrocarbons from an active fire sampled within minutes of combustion were, relative to ethane, ethene, 2.45; ethyne 0.57; propane, 0.25; propene, 0.73; propyne, 0.06; n-butane, 0.09; i-butane, 0.01; 1-butene, 0.14; cis-2-butene, 0.02; trans-2-butene, 0.03; i-butylene, 0.07; 1,3-butadiene, 0.12; n-pentane, 0.05; i-pentane, 0.03; 1-pentene, 0.06; n-hexane, 0.05; 1-hexene, 0.07; benzene, 0.37; toluene, 0.16.

Blake, D. R.; Smith, T. W., Jr.; Chen, T.-Y.; Whipple, W. J.; Rowland, F. S.

1994-01-01

175

Analysis of natural gas: the necessity of multiple standards for calibration.  

PubMed

The importance of natural gas as an international trading commodity and the cost to consumers has made the accuracy of determinations for the components of natural gas very important. Pricing of natural gas is based on the heating value of the gas determined from either calorimetry measurements or calculations based on individual component concentrations determined by gas chromatography (GC). Due to the expense of accurate calibration standards, many analysts and laboratories will use a single calibration standard to perform natural gas determinations. Therefore, the purpose of this study was to determine whether an analyst could accurately measure the components of natural gas, in particular methane, using a single standard, or whether a suite of standards is necessary to calibrate the analytical instrument. A suite of eight gravimetric primary standards was prepared covering a concentration range for methane of 64-94 mol%, with uncertainties of +/-0.05% relative (95% confidence interval). These natural gas primary standards also contained nitrogen, carbon dioxide, ethane, propane, iso-butane, n-butane, iso-pentane, n-pentane, and n-hexane with varying concentrations from 0.02 to 14%. A single analytical method was used in which only the amount of sample injected onto the column was altered. The results show that when injecting a 0.5 ml sample volume a second-order regression through the standards is necessary for the determination of methane. The results for nitrogen, ethane and propane also show the same trend. Only those individual standards whose methane concentration is within 1% of the test mixture predicted a concentration within 0.05% of the regression value. Those individual primary standards whose methane concentration is different by more than +/-1% of the test mixture predicted values differing by +/-0.5 to +/-2.0% from the regression value. These differences lie well outside the predicted concentration uncertainty interval of +/-0.20%. A smaller sample volume, 0.1 ml, resulted in a set of data that could be fit using linear regression. Each of the eight primary standards individually predicted the methane in the test mixture to be within +/-0.11% of the predicted value from linear regression. The data confirm that it is imperative to fully characterize the analytical system before proceeding with an analysis. PMID:14584698

Rhoderick, George C

2003-10-31

176

COUPLING CONSTRAINT BOUNDARY MAPPING IN THE PROCESS DESIGN PARAMETER SPACE WITH COMMERCIAL PROCESS SIMULATOR TO ESTIMATE PROCESS DESIGN RELIABILITY  

E-print Network

. Computers & Chemical Engineering, 7, 439. Howat, C. S., 1983. Phase Equilibria Studies of the Isoprene, n-Pentane, Cyclopentadiene and Dicyclopentadiene System from 290 to 360K, Ph.D. Thesis, University of Kansas. Howat, C. S., 1995. Estimation...

Myers, Elim Rosalva

2010-01-25

177

Immiscible Systems  

ERIC Educational Resources Information Center

layers of liquids. The setup of both demonstrations is such that one homogeneous layer in a multiphasic mixture separates into two new layers upon shaking. The solvents used are methanol, toluene, petroleum ether or "n"-pentane, silicone oil, perfluoroheptanes,…

Eckelmann, Jens; Luning, Ulrich

2013-01-01

178

Levitation effect in zeolites: Quasielastic neutron scattering and molecular dynamics study of pentane isomers in zeolite NaY.  

PubMed

We report the quasielastic neutron scattering (QENS) and molecular dynamics (MD) investigations into diffusion of pentane isomers in zeolite NaY. The molecular cross section perpendicular to the long molecular axis varies for the three isomers while the mass and the isomer-zeolite interaction remains essentially unchanged. Both QENS and MD results show that the branched isomers neopentane and isopentane have higher self-diffusivities as compared with n-pentane at 300 K in NaY zeolite. This result provides direct experimental evidence for the existence of nonmonotonic, anomalous dependence of self-diffusivity on molecular diameter known as the levitation effect. The energetic barrier at the bottleneck derived from MD simulations exists for n-pentane which lies in the linear regime while no such barrier is seen for neopentane which is located clearly in the anomalous regime. Activation energy is in the order E(a)(n-pentane)>E(a)(isopentane)>E(a)(neopentane) consistent with the predictions of the levitation effect. In the liquid phase, it is seen that D(n-pentane)>D(isopentane)>D(neopentane) and E(a)(n-pentane)n-pentane, a single exponential fit provides a poor fit especially at short times. Cage residence time is largest for n-pentane and lowest for neopentane. For neopentane, the width of the self-part of the dynamic structure factor shows a near monotonic decrease with wavenumber. For n-pentane a minimum is seen near k=0.5 A(-1) suggesting a slowing down of motion around the 12-ring window, the bottleneck for diffusion. Finally, the result that the branched isomer has a higher diffusivity as compared with the linear analog is at variation from what is normally seen. PMID:20406001

Borah, Bhaskar J; Jobic, H; Yashonath, S

2010-04-14

179

21 CFR 177.2440 - Polyethersulfone resins.  

Code of Federal Regulations, 2013 CFR

...food-contact surface: distilled water, 50 percent (by volume) ethyl alcohol in distilled water, 3 percent acetic acid in distilled water, and n -heptane. (Note...testing the finished food-contact article, use a separate test...

2013-04-01

180

21 CFR 177.2440 - Polyethersulfone resins.  

...food-contact surface: distilled water, 50 percent (by volume) ethyl alcohol in distilled water, 3 percent acetic acid in distilled water, and n -heptane. (Note...testing the finished food-contact article, use a separate test...

2014-04-01

181

21 CFR 177.2440 - Polyethersulfone resins.  

Code of Federal Regulations, 2012 CFR

...food-contact surface: distilled water, 50 percent (by volume) ethyl alcohol in distilled water, 3 percent acetic acid in distilled water, and n -heptane. (Note...testing the finished food-contact article, use a separate test...

2012-04-01

182

340 J. Am. Chem. SOC.1982, 104, 340-343 Scheme 111"  

E-print Network

of diethyl malonate with the labeled mesylate was followed by ester hydrolysis, decarboxylation, and Schmidt]-n-heptanal(10). If it is assumed that the malonate alkylation step proceeds with inversionof configuration

Boxer, Steven G.

183

COMBUSTION REACTIONS OF PARAFFIN COMPONENTS IN LIQUID TRANSPORTATION  

E-print Network

-hexadecane and semi-detailed sub- models of iso-octane and methyl cyclohexane, in addition to reac- tions of aromatic for n-heptane, iso-octane, n-decane and gasoline premixed flames. The mechanism was also able

Utah, University of

184

21 CFR 177.1330 - Ionomeric resins.  

...ethanol/water. ii. Nonalcoholic 3% acetic acid. iii. Containing more than 8% alcohol 50% ethanol/water. 7. Bakery products Water, n -heptane. 8. Dry solids (without free fat or oil) No extraction test required. 9. Dry...

2014-04-01

185

Influence of chain length of tertiary amines on extractability and chemical interactions in reactive extraction of succinic acid  

Microsoft Academic Search

Reactive extraction of succinic acid from aqueous solutions with various tertiary amines dissolved in 1-octanol and in n-heptane\\u000a has been studied as a function of the chain length of the tertiary amine. In the tertiary amine extractants in 1-octanol,\\u000a the extractabilities of tertiary amines were proportional to their chain length. But, in n-heptane, the extractabilities of\\u000a tertiary amines decreased with

Yeon Ki Hong; Won Hi Hong

2004-01-01

186

Investigation and technique in the fluorescent spectra examination of crude oil  

E-print Network

as developers n-heptane, benzene, . acetone, and pyrid. ine. A heptane soluble portion of the residue obtained by distilling &'iyoming crude oi. ls at P $00 0 was chromatographed. Lawrence and Barby (18) fractionated chromato- graphically a Venezuelan fuel... as developers n-heptane, benzene, . acetone, and pyrid. ine. A heptane soluble portion of the residue obtained by distilling &'iyoming crude oi. ls at P $00 0 was chromatographed. Lawrence and Barby (18) fractionated chromato- graphically a Venezuelan fuel...

Chambers, Gilbert Vester

2012-06-07

187

Continuous enzymatic transesterification of high oleic sunflower oil in a packed bed reactor: influence of the glycerol production  

Microsoft Academic Search

The transesterification of high oleic sunflower oil with butanol by the immobilized Lipozyme® in n-hexane was carried out in a continuous packed bed reactor, oleic acid, butyl ester, and glycerol being formed as the main products. It was found that glycerol, insoluble in n-hexane, remained in the reactor adsorbed onto the enzymatic support, leading to a drastic decrease in enzymatic

Valérie Dossat; Didier Combes; Alain Marty

1999-01-01

188

THE ANALYTICAL APPLICATION OF FLUORICION. PART IV. SOLVENT EXTRACTION OF THORIUM IN FLUORIDE  

Microsoft Academic Search

Thorium was extracted from a mixture of thorium fluoride in 50% aluminum ; nitrate and nitric acid with TBPnHexane. The ions extracted with 20% TBP-nHexane ; were mainly thorium and a small amount of cerium. Few of the rare earth elements ; except cerium were extracted. The separation of thorium from thorium ore was ; satisfactorily made with 50% TBP-nHexane.

Seki

1962-01-01

189

Research on Volatile Organic Compounds in the Mexico City Metropolitan Area (MCMA) in two campaigns collected in the Winter-2011 and Spring-2012  

NASA Astrophysics Data System (ADS)

Because of the importance of information on the concentration and speciation of Volatile Organic Compounds (VOC) in the atmosphere for the development of regulatory programs or emission control, is necessary to determine the type and the concentrations of reactive and toxic VOC in atmospheric air. The aim of this study is to determine the speciation and quantification of VOC in the atmospheric air of the Mexico City Metropolitan Area (MCMA), from samples obtained in November-December 2011 (cold-dry) and March-April (warm-dry). This study presents the results of characterization of VOC in ambient air in the MCMA conducted during 2011-2012. Sampling of VOC was done in two sampling campaigns: from November 17th to December 11th, 2011, and March 1st to April 6th, 2012 through collection of ambient air each six days in six liters stainless steel SUMMA canisters of 24 hours integrated samples, in three sites (Merced: commercial area with vehicular sources, Pedregal: residential area with vehicular sources and San Agustin: industrial sources with heavy traffic), in the MCMA. The analysis of samples was carried out with two chromatographic systems: 1) method equivalent to the EPA's Method TO-14, and 2) GC/MSD coupled to a preconcentrator ENTECH, for the analysis of the compounds listed in EPA method TO15. It was investigated the concentration of 111 volatile organic compounds, (ozone precursors and toxic compounds). It was found that concentrations of 23 species, constitute 80% of the total VOC concentration tested: ethane, propane, isobutane, n-butane, n-pentane, n-hexane, isopentane, methylcyclopentane, ethylene, propylene, acetylene, benzene, toluene, ethylbenzene, m/p-xylene, o-xylene, 1,2,4-trimethylbenzene, ethyl and isopropyl alcohols, acetone, 2-butanone, MTBE and ethyl acetate. Both in 2011 and 2012, the highest concentrations measured in the three sites were for compounds associated with the combustion of LPG gas: propane, n-butane. The highest concentrations of 25.2±14.5 ppbV and 16.6±9 ppbV for butane and propane respectively, was achieved in Merced in 2011 and 14.7±3.5 ppbV and 28.4±6.7 ppbV for the same compounds, in San Agustin in 2012). In the case of vehicular emissions, in both campaigns, 2011 and 2012, Merced showed the highest levels: 12.3±4.8 ppbV, 2.7±1.1 ppbV and 4.3±3.3 ppbV for toluene, benzene and MTBE respectively in 2011 and 9.48±6.5 ppbV, 1.5±0.9 ppbV and 2.4±1.0 ppbV for the same compounds in 2012. The compounds which comes from industrial emissions, have the lowest average concentrations in all stations. The VOCs measurement in atmospheric air, allowed determinate that the main source of VOC in the three studied sites of the MCMA are emissions of LPG gas and vehicular emissions. The highest concentrations were found during the cold-dry period in 2011. These data are consistent with continuous measurements determined in the southeastern MCMA during 2000-2007.

Magaña, M.; González-Vargas, S.; Blanco, S.; Watanabe, T.; Maeda, T.; Cardenas, B.

2013-05-01

190

Syntheses and structures of lithiated sulfones Li[CR(R?)SO 2Ph] – C versus O bound lithium. [{Li{CH(Me)SO 2Ph}(thf)} ?] – The structure of a C-bound derivative  

Microsoft Academic Search

Sulfones RCH(R?)SO2Ph were reacted with n-BuLi in thf\\/n-hexane (R\\/R?=H\\/Me, Me\\/Et, H\\/CH2Ph) and toluene\\/n-hexane (R\\/R?=Me\\/Ph) yielding under deprotonation Li[CR(R?)SO2Ph] which reacted with Me3SiCl and n-Bu3SnCl forming the requisite trimethylsilyl and tri(n-butyl)tin substituted derivatives R3?E-C(R)R?SO2Ph(R3?E=Me3Si,n-Bu3Sn). Performing the reactions of RCH(R?)SO2Ph with n-BuLi in n-hexane (instead of thf\\/n-hexane) and toluene\\/n-hexane, respectively, resulted in the precipitation of the organo lithium compounds Li[CR(R?)SO2Ph] (1–4) which

Matthias Linnert; Clemens Bruhn; Christoph Wagner; Dirk Steinborn

2006-01-01

191

Electron Transport in Paracoccus Halodenitrificans and the Role of Ubiquinone  

NASA Technical Reports Server (NTRS)

The membrane-bound NADH oxidase of Paracoccus halodenitrificans was inhibited by dicoumarol, 2-n-heptyl-4-hydroxyquinoline-N-oxide (HQNO), and exposure to ultraviolet light (at 366 nm). When the membranes were extracted with n-pentane, NADH oxidase activity was lost. Partial restoration was achieved by adding the ubiquinone fraction extracted from the membranes. Succinate oxidation was not inhibited by dicoumarol or HQNO but was affected by ultraviolet irradiation or n-pentane extraction. However, the addition of the ubiquinone fraction to the n-pentane-extracted membranes did not restore enzyme activity. These observations suggested the reducing equivalents from succinate entered the respiratory chain on the oxygen side of the HQNO-sensitive site and probably did not proceed through a quinone.

Hochstein, L. I.; Cronin, S. E.

1983-01-01

192

Understanding nanofluid stability through molecular simulation  

SciTech Connect

We performed molecular dynamics simulations to study solvation of a nanoparticle and nanoparticle-nanoparticle interactions in an n-hexane solution. Structural signatures are barely observed between the nanoparticle and n-hexane molecules because of weak binding and steric effects. The dynamic properties of the n-hexane molecule, on the other hand, are significantly influenced by the solvated nanoparticle. The diffusion of n-hexane molecules inside the nanoparticle is significantly decreased mainly because of the loss of dimensions of translation. Because one translational degree of freedom is lost by colliding with the wall of nanoparticle, the n-hexane molecules outside the nanoparticle diffuse 30% slower than the molecules in pure solution. The computed free energy profiles illustrate that the arrangement of the nanoparticles in bulk n-hexane solution are dependent on the orientation and functional group. We found that the n-hexane solvent exerts some effects on the interactions between the solvated nanoparticles. This work was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences and by the Office of Energy Efficiency and Renewable Energy, Geothermal Technologies Program. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle.

Dang, Liem X.; Annapureddy, Harsha V.; Sun, Xiuquan; Thallapally, Praveen K.; McGrail, B. Peter

2012-11-01

193

Droplet Vaporization in a High-Pressure Gas  

NASA Technical Reports Server (NTRS)

Results of an experimental study of the vaporization of single R-113 and n-heptane droplets are presented. Gas temperature is found to have a strong effect on drop vaporization, while gas pressure has a weaker effect. A comparison of data from experiments in near-zero gravity with those conducted in normal gravity shows that the vaporization rate and droplet lifetime are affected depending on the liquid involved. In the case of R-113, the removal of the gravity field in free-fall experiments resulted in an increase of droplet lifetime of about 30 percent, whereas in the case of n-heptane, a much less pronounced effect was observed.

Hartfield, J. P.; Farrell, P. V.

1993-01-01

194

A study of Fischer-Tropsch model compounds reacting over ZSM-5  

E-print Network

hydrocarbons or remained and reacted with another molecule. An olefin, like 1-heptene, does not have to form a sterically restricted intermediate as shown in equation (6) as n-heptane would. The size of the ZSM-5 cage restricted the size... hydrocarbons or remained and reacted with another molecule. An olefin, like 1-heptene, does not have to form a sterically restricted intermediate as shown in equation (6) as n-heptane would. The size of the ZSM-5 cage restricted the size...

Riley, Mark Garner

2012-06-07

195

Photophysics of 4- N, N-dimethylamino cinnamaldehyde in AOT reverse micelles and exploration of its position and orientation  

NASA Astrophysics Data System (ADS)

An attempt has been made in this Letter to locate the position and orientation of 4- N, N-dimethylamino cinnamaldehyde (DMACA) inside sodium bis(2-ethylhexyl) sulfosuccinate (AOT)- n-heptane reverse micelle based on change in photophysical properties of DMACA compared to that in n-heptane. It has been proposed that the possibility of finding the donor moiety inside the small water pool of reverse micelle is maximum while the acceptor group straddles in the remaining part of the reverse micelle. The micropolarity in the vicinity of the donor moiety has been computed in terms of dielectric constant with varying water pool size.

Panja, Subhasis; Chakravorti, Sankar

2003-01-01

196

21 CFR 177.1620 - Polyethylene, oxidized.  

...accordance with the following prescribed conditions: (a) Oxidized polyethylene is the basic resin produced by the mild air oxidation of polyethylene conforming to the density, maximum n- hexane extractable fraction, and maximum xylene soluble...

2014-04-01

197

40 CFR 437.2 - General definitions.  

Code of Federal Regulations, 2010 CFR

...nickel. (14) O&G means total recoverable oil and grease (n-hexane extractable material). (15) Selenium means total selenium. (16) Silver means total silver. (17) Tin means total tin. (18) Titanium means...

2010-07-01

198

Spectroscopic studies on the formation of coke on individual Fluid Catalytic Cracking particles: the effect of poisoning metal compounds.  

E-print Network

??The formation of coke on individual Fluid Catalytic Cracking (FCC) catalyst particles was studied using UV/Vis microspectroscopy and confocal fluorescence microscopy, with n-hexane cracking as… (more)

Goetze, J.G.

2013-01-01

199

Biological activity of Glechoma hederacea.  

PubMed

The n-hexane, dichloromethane and methanol extracts of the aerial parts of Glechoma hederacea have been screened for antibacterial and free radical scavenging activity. General toxicity (brine shrimp lethality assay) of these extracts has also been assessed. PMID:12490241

Kumarasamy, Y; Cox, P J; Jaspars, M; Nahar, L; Sarker, S D

2002-12-01

200

Biological activity of Glechoma hederacea  

Microsoft Academic Search

The n-hexane, dichloromethane and methanol extracts of the aerial parts of Glechoma hederacea have been screened for antibacterial and free radical scavenging activity. General toxicity (brine shrimp lethality assay) of these extracts has also been assessed.

Y Kumarasamy; P. J Cox; M Jaspars; L Nahar; S. D Sarker

2002-01-01

201

21 CFR 178.3010 - Adjuvant substances used in the manufacture of foamed plastics.  

...75-37-6) For use as a blowing agent in polystyrene. Isopentane For use as a blowing agent in polystyrene. n -Pentane Do. 1,1,2...only as a blowing agent adjuvant in polystyrene at a level not to exceed 0.3...

2014-04-01

202

Crossed-beam dc slice imaging of chlorine atom reactions with pentane isomers  

Microsoft Academic Search

We present the first in a series of detailed investigations of the reaction of Cl atoms with hydrocarbons in crossed beams. This study focuses on reaction with the pentane isomers n-pentane, isopentane, and neopentane. These crossed-beam ion imaging experiments rely on ``universal'' 157 nm probe of the pentyl radical product, with dc sliced detection providing the scattering distributions directly. The

Armando D. Estillore; Laura M. Visger; Arthur G. Suits

2010-01-01

203

Crossed-beam dc slice imaging of chlorine atom reactions with pentane isomers  

Microsoft Academic Search

We present the first in a series of detailed investigations of the reaction of Cl atoms with hydrocarbons in crossed beams. This study focuses on reaction with the pentane isomers n-pentane, isopentane, and neopentane. These crossed-beam ion imaging experiments rely on “universal” 157 nm probe of the pentyl radical product, with dc sliced detection providing the scattering distributions directly. The

Armando D. Estillore; Laura M. Visger; Arthur G. Suits

2010-01-01

204

Thermodynamic analysis of a solar thermal water pump  

Microsoft Academic Search

The principle of the workings of a solar thermal water pump with n-pentane as the working fluid is described briefly. The performance of the pump is predicted from the thermodynamic analysis of the cycle of events. Experiments were carried out with a small solar thermal pump having a collector area of 1 m2. The experimental and theoretical results were compared.

K. Sumathy; A. Venkatesh; V. Sriramulu

1996-01-01

205

Conservative and dissipative force field for simulation of coarse-grained alkane molecules: A bottom-up approach  

NASA Astrophysics Data System (ADS)

We apply operational procedures available in the literature to the construction of coarse-grained conservative and friction forces for use in dissipative particle dynamics (DPD) simulations. The full procedure rely on a bottom-up approach: large molecular dynamics trajectories of n-pentane and n-decane modeled with an anisotropic united atom model serve as input for the force field generation. As a consequence, the coarse-grained model is expected to reproduce at least semi-quantitatively structural and dynamical properties of the underlying atomistic model. Two different coarse-graining levels are studied, corresponding to five and ten carbon atoms per DPD bead. The influence of the coarse-graining level on the generated force fields contributions, namely, the conservative and the friction part, is discussed. It is shown that the coarse-grained model of n-pentane correctly reproduces self-diffusion and viscosity coefficients of real n-pentane, while the fully coarse-grained model for n-decane at ambient temperature over-predicts diffusion by a factor of 2. However, when the n-pentane coarse-grained model is used as a building block for larger molecule (e.g., n-decane as a two blobs model), a much better agreement with experimental data is obtained, suggesting that the force field constructed is transferable to large macro-molecular systems.

Trément, Sébastien; Schnell, Benoît.; Petitjean, Laurent; Couty, Marc; Rousseau, Bernard

2014-04-01

206

PETROLEUM RESINS: SEPARATION, CHARACTER, AND ROLE IN PETROLEUM  

Microsoft Academic Search

In petroleum science, the term resin generally implies material that has been eluted from various solid adsorbents, whereas the term maltenes (or petrolenes) indicates a mixture of the resins and oils obtained as filtrates from the asphaltene precipitation. Thus, after the asphaltenes are precipitated, adsorbents are added to the n-pentane solutions of the resins and oils, by which process the

Simon I. Andersen; James G. Speight

2001-01-01

207

Integrating Safety Issues in Optimizing Solvent Selection and Process Design  

E-print Network

Health effect Examples of solvents Damage to nervous system n-hexane, perchloroethylene, n-butyl mercaptan Damage to liver or kidney Toluene, carbon tetrachloride, 1,1,2,2 ? tetrachloroethane, chloroform Reproductive hazards 2-methoxyethanol, 2... Health effect Examples of solvents Damage to nervous system n-hexane, perchloroethylene, n-butyl mercaptan Damage to liver or kidney Toluene, carbon tetrachloride, 1,1,2,2 ? tetrachloroethane, chloroform Reproductive hazards 2-methoxyethanol, 2...

Patel, Suhani Jitendra

2011-10-21

208

Toxic polyneuropathy due to glue sniffing  

Microsoft Academic Search

Four cases of toxic polyneuropathy due to glue-sniffing were reported. Neurological examination revealed motor predominant mixed type polyneuropathy. The cause of polyneuropathies in these cases was considered to be due to the inhalation of the vaporized elements of the adhesive agent, which contain mainly n-hexane and toluene. N-hexane is considered to be chiefly responsible for the polyneuropathy, though toluene also

Ikuo Goto; Mutsuro Matsumura; Naohide Inoue; Yoshiyuki Murai; Kenshiro Shida; Tetsuji Santa; Yoshigoro Kuroiwa

1974-01-01

209

Preparative isolation and purification of coumarins from Angelica dahurica ( Fisch. ex Hoffm) Benth, et Hook. f (Chinese traditional medicinal herb) by high-speed counter-current chromatography  

Microsoft Academic Search

A preparative high-speed counter-current chromatography (HSCCC) method for isolation and purification of coumarins from Angelica dahurica (Fisch. ex Hoffm) Benth, et Hook. f (Baizhi in Chinese) was successfully established by using n-hexane–methanol–water as the two-phase solvent system in gradient elution mode. The upper phase of n-hexane–methanol–water (5:5:5, v\\/v) was used as the stationary phase of HSCCC. The mobile phase used

Renmin Liu; Aifeng Li; Ailing Sun

2004-01-01

210

Anticonvulsive activity of Butea monosperma flowers in laboratory animals  

Microsoft Academic Search

The bioassay-guided fractionation of dried flowers of Butea monosperma (BM) was carried out to isolate the active principle responsible for its anticonvulsant activity. The petroleum ether extract was fractionated by column chromatography using solvents of varying polarity such as n-hexane, n-hexane:ethyl acetate, ethyl acetate, and methanol. The anticonvulsive principle of B. monosperma was found to be a triterpene (TBM) present

Veena S Kasture; S. B Kasture; C. T Chopde

2002-01-01

211

Synthesis of nanoporous silica aerogel by ambient pressure drying  

Microsoft Academic Search

A crack-free silica aerogel monolith was fabricated from a cheap water glass derived silicic acid solution by adding glycerol,\\u000a which served as a drying control chemical additive (DCCA). The OH surfaces of the wet gel with glycerol were modified using\\u000a a TMCS\\/n-hexane mixture followed by solvent exchange from water to n-hexane. The obtained surface modified wet gel was dried at

Chul Eui Kim; Jong Seol Yoon; Hae Jin Hwang

2009-01-01

212

Fabrication of Dye-Dispersed Optical-Quality Polymer Films by Coprecipitation of Cyanine Dye with Polymers  

Microsoft Academic Search

3,3'-Diethyloxadicarbocyanine iodide (DODCI)-dissolved polymer powders were formed by coprecipitation of DODCI with polymers [poly(methyl methacrylate) (PMMA), poly(2-hydroxypropyl methacrylate) (PHPMA), etc.]. An acetone solution of DODCI in which a purified polymer was also dissolved was injected into a large amount of n-hexane. The precipitated powder in n-hexane was filtered and then dried under ultrahigh vacuum (UHV), and formed into a thin

Takashi Hiraga; Shigeru Takarada; Norio Tanaka; Kikuko Hayamizu; Tetsuo Moriya

1994-01-01

213

Surface Pressure, Hysteresis, Interfacial Tension, and CMC of Four Sorbitan Monoesters at Water–Air, Water–Hexane, and Hexane–Air Interfaces  

Microsoft Academic Search

The purpose of this study was to investigate the interfacial properties of sorbitan monoesters (Span 20, 40, 60, and 80). The surface pressure was investigated at the water–air interface using a Langmuir–Blodgett apparatus. Interfacial tensions at n-hexane–air and water–n–hexane interfaces were measured by a du Nouy tensiometer. The effects of different surface-active agents and their concentrations on the interfacial properties

Leena Johanna Peltonen; Jouko Yliruusi

2000-01-01

214

Structure and dynamics of a pentablock copolymer of polystyrene-polybutadiene in a butadiene-selective solvent  

E-print Network

Structure and dynamics of a pentablock copolymer of polystyrene-polybutadiene in a butadiene solutions of a polystyrene-polybutadiene pentablock copolymer in n-heptane, a strongly selective solvent by the association of w200 polystyrene blocks. Dynamic light scattering measurements on 8 and 9% samples showed three

215

Equilibrium studies on reactive extraction of succinic acid from aqueous solutions with tertiary amines  

Microsoft Academic Search

Reactive extraction of succinic acid from aqueous solutions with various tertiary amines dissolved in 1-octanol and n-heptane has been studied as a function of the acid concentration and the chain length of tertiary amine. When 1-octanol was used as diluent, the extractability of the tertiary amine was proportional to the chain length of tertiary amine at the same concentration of

Yeon Ki Hong; Won Hi Hong

2000-01-01

216

A REVIEW OF LARGE-SCALE FIRE TESTING FOCUSING ON THE FIRE BEHAVIOUR OF CHEMICALS  

E-print Network

and toxic combustion products in well ventilated conditions. Some aspects of the implication of lab of products acquired over a long term period of time (nearly ten years). Most tests were carried out). C-H or C-H-0 solvents (n-Heptane, isooctane, toluene, methanoi) have also been tested äs reference

Boyer, Edmond

217

Synthesis of a macroporous hydrophilic ternary copolymer and its application in boronate-affinity separation  

Microsoft Academic Search

A new macroporous ternary copolymer was synthesized using vinyl acetate (VAC), glycidyl methacrylate (GMA) and allyl methacrylate (AMA) through suspension polymerization with a mixture of n-heptane and butyl acetate as the porogenic agent. The effects of the crosslinking degree, the level of GMA and the porogenic agent mixture and composition on the pore structure of the copolymer and on the

Yinlin Lei; Zuozhen Liu; Qinfeng Liu; Xingyan Wu

2001-01-01

218

Lipase catalyzed formation of flavour esters  

Microsoft Academic Search

Summary Thirteen commercial lipase preparations were checked for their ability to catalyse the formation of flavour esters (isoamyl or geranyl acetate, propionate and butyrate) by either direct esterification or ester solvolysis in n-heptane. The formation of isoamyl or geranyl butyrates and propionates by direct esterification was catalyzed by the majority of the tested lipases. Acetic acid esters were more difficult

G. Langrand; C. Triantaphylides; J. Baratti

1988-01-01

219

LOW OZONE-DEPLETING HALOCARBONS AS TOTAL-FLOOD AGENTS: VOLUME 2. LABORATORY-SCALE FIRE SUPPRESSION AND EXPLOSION PREVENTION TESTING  

EPA Science Inventory

The report gives results from (1) flame suppression testing of potential Halon-1301 (CF3Br) replacement chemicals in a laboratory cup burner using n-heptane fuel and (2) explosion prevention (inertion) testing in a small-scale explosion sphere using propane and methane as fuels. ...

220

Asphaltene Precipitation in Crude Oils: Theory and Experiments  

E-print Network

asphaltenes and resins. Asphaltenes are defined as the fraction separated from crude oil or petroleum products-Gonzalez and Carlos Lira-Galeana Thermodynamics Research Laboratory, Mexican Institute of Petroleum, Mexico City 07730 upon addition of hydrocarbon solvents such as n-heptane (Speight, 1999). Resins are defined

Wu, Jianzhong

221

Simulating vapor-liquid nucleation of n-alkanes  

NASA Astrophysics Data System (ADS)

A combination of the aggregation-volume-bias Monte Carlo algorithm, the configurational-bias Monte Carlo algorithm, and the umbrella sampling technique was applied to investigate homogeneous vapor-liquid nucleation in ethane, n-butane, and n-heptane. The simple transferable potentials for phase equilibria-united atom (TraPPE-UA) force field was used in this investigation. It was found that for the n-heptane case, the TraPPE-UA force field predicted a nucleation rate that is about three to four orders of magnitude higher than that measured by an upward thermal diffusion cloud chamber experiment. Comparison of the simulation results to the classical nucleation theory (CNT) shows that CNT consistently overestimates the barrier heights for all chain lengths investigated. The offset on the barrier heights was found nearly independent of the supersaturation for both ethane and n-butane, similar to a Lennard-Jones system previously studied. This also directly leads to a good agreement on the cluster sizes between the simulation and the CNT calculated from the nucleation theorem. For n-heptane, however, the offset was found to depend on the supersaturation. It appears that CNT predicts a slightly weaker dependence of the nucleation rate on supersaturation, which agrees with both density functional calculations and the experiments. Structural analysis demonstrates that the orientational order near the surface differs significantly between the critical nucleus and the bulk planar liquid-vapor interface for n-heptane systems, whereas the density in the interior of the critical nucleus is in good agreement with the bulk liquid density. The different surface ordering offers a microscopic explanation for the differences observed for n-heptane between the CNT on one side and experimental observations and simulations on the other side.

Chen, Bin; Siepmann, J. Ilja; Oh, Kwang J.; Klein, Michael L.

2002-03-01

222

HCCI experiments with toluene reference fuels modeled by a semidetailed chemical kinetic model  

SciTech Connect

A semidetailed mechanism (137 species and 633 reactions) and new experiments in a homogeneous charge compression ignition (HCCI) engine on the autoignition of toluene reference fuels are presented. Skeletal mechanisms for isooctane and n-heptane were added to a detailed toluene submechanism. The model shows generally good agreement with ignition delay times measured in a shock tube and a rapid compression machine and is sensitive to changes in temperature, pressure, and mixture strength. The addition of reactions involving the formation and destruction of benzylperoxide radical was crucial to modeling toluene shock tube data. Laminar burning velocities for benzene and toluene were well predicted by the model after some revision of the high-temperature chemistry. Moreover, laminar burning velocities of a real gasoline at 353 and 500 K could be predicted by the model using a toluene reference fuel as a surrogate. The model also captures the experimentally observed differences in combustion phasing of toluene/n-heptane mixtures, compared to a primary reference fuel of the same research octane number, in HCCI engines as the intake pressure and temperature are changed. For high intake pressures and low intake temperatures, a sensitivity analysis at the moment of maximum heat release rate shows that the consumption of phenoxy radicals is rate-limiting when a toluene/n-heptane fuel is used, which makes this fuel more resistant to autoignition than the primary reference fuel. Typical CPU times encountered in zero-dimensional calculations were on the order of seconds and minutes in laminar flame speed calculations. Cross reactions between benzylperoxy radicals and n-heptane improved the model predictions of shock tube experiments for {phi}=1.0 and temperatures lower than 800 K for an n-heptane/toluene fuel mixture, but cross reactions had no influence on HCCI simulations. (author)

Andrae, J.C.G. [Department of Chemical Engineering and Technology, Royal Institute of Technology (KTH), SE-100 44 Stockholm (Sweden); Brinck, T. [Department of Physical Chemistry, Royal Institute of Technology (KTH), SE-100 44 Stockholm (Sweden); Kalghatgi, G.T. [Shell Global Solutions (UK), P.O. Box 1, Chester CH1 3SH (United Kingdom)

2008-12-15

223

Elimination of hydrophobic volatile organic compounds in fungal biofilters: reducing start-up time using different carbon sources.  

PubMed

Fungal biofilters have been recently studied as an alternative to the bacterial systems for the elimination of hydrophobic volatile organic compounds (VOC). Fungi foster reduced transport limitation of hydrophobic VOCs due to their hydrophobic surface and extended gas exchange area associated to the hyphal growth. Nevertheless, one of their principal drawbacks is their slow growth, which is critical in the start-up of fungal biofilters. This work compares the use of different carbon sources (glycerol, 1-hexanol, wheat bran, and n-hexane) to reduce the start-up period and sustain high n-hexane elimination capacities (EC) in biofilters inoculated with Fusarium solani. Four parallel experiments were performed with the different media and the EC, the n-hexane partition coefficient, the biomass production and the specific consumption rate were evaluated. Biofilters were operated with a residence time of 1.3?min and an inlet n-hexane load of 325?g?m(-3) (reactor) h(-1). The time to attain maximum EC once gaseous n-hexane was fed was reduced in the three experiments with alternate substrates, as compared to the 36 days needed with the control where only n-hexane was added. The shortest adaptation period was 7 days when wheat bran was initially used obtaining a maximum EC of 160?g?m(-3) (reactor) h(-1) and a critical load of 55?g?m(-3) (reactor) h(-1). The results were also consistent with the pressure drop, the amount of biomass produced and its affinity for the gaseous n-hexane, as represented by its partition coefficient. PMID:21404250

Vergara-Fernández, Alberto; Hernández, Sergio; Revah, Sergio

2011-04-01

224

Computational study of hydrocarbon adsorption in metal-organic framework Ni2(dhtp).  

PubMed

Enhancing the efficiency of the Rankine cycle, which is utilized for multiple renewable energy sources, requires the use of a working fluid with a high latent heat of vaporization. To further enhance its latent heat, a working fluid can be placed in a metal organic heat carrier (MOHC) with a high heat of adsorption. One such material is Ni\\DOBDC, in which linear alkanes have a higher heat of adsorption than cyclic alkanes. We carried out molecular dynamics simulations to investigate the structural, diffusive, and adsorption properties of n-hexane and cyclohexane in Ni\\DOBDC. The strong binding for both n-hexane and cyclohexane with Ni\\DOBDC is attributed to the increase of the heat of adsorption observed in experiments. Our structural results indicate the organic linkers in Ni\\DOBDC are the primary binding sites for both n-hexane and cyclohexane molecules. However, at all temperatures and loadings examined in present work, n-hexane clearly showed stronger binding with Ni\\DOBDC than cyclohexane. This was found to be the result of the ability of n-hexane to reconfigure its structure to a greater degree than cyclohexane to gain more contacts between adsorbates and adsorbents. The geometry and flexibility of guest molecules were also related to their diffusivity in Ni\\DOBDC, with higher diffusion for flexible molecules. Because of the large pore sizes in Ni\\DOBDC, energetic effects were the dominant force for alkane adsorption and selectivity. PMID:21384829

Sun, Xiuquan; Wick, Collin D; Thallapally, Praveen K; McGrail, B Peter; Dang, Liem X

2011-03-31

225

Chemical class separation of organics in shale oil by thin-layer chromatography  

SciTech Connect

Thin-layer chromatography (TLC) has been applied to the chemical class fractionation of shale oil. The chromatographic procedure gives rapid and reproducible separation of the oil into 14 fractions, without requiring prior extraction of asphaltenes, acids, or bases. The oil was adsorbed on silica-coated TLC plates and eluted with n-pentane and n-pentane/diethyl ether to separate the nonpolar and polar components, respectively. The principal compound types resolved included n-alkanes, alkenes, mono-, hydro-, di-, and polyaromatics, nitriles and ketones, hydroxyl aromatic hydrocarbons, and nitrogen heterocyctes. Compound identification was by gas chromatography/mass spectroscopy supplemented by ir spectrometry. The method significantly decreases the analysis time required for chemical class fractionation. 33 references, 4 figures, 1 table.

Harvey, T.G.; Matheson, T.W.; Pratt, K.C.

1984-01-01

226

Trends in the condensation\\/evaporation and adsorption enthalpies of volatile organic compounds on mesoporous silica materials  

Microsoft Academic Search

The adsorption–desorption of toluene, methylcyclohexane, neopentane and n-pentane was measured at temperatures between 258 and 308K on mesoporous silica materials with different pore structures and pore sizes (MCM-41, SBA-15, SBA-16, LPC and MCF). It was found that the change in the width of the hysteresis cycles with temperature is similar for MCM-41, SBA-15 and MCF but distinct for the materials

P. A. Russo; M. M. L. Ribeiro Carrott; P. J. M. Carrott

227

A coupled implicit method for chemical non-equilibrium flows at all speeds  

NASA Technical Reports Server (NTRS)

The present time-accurate coupled-solution procedure addresses the chemical nonequilibrium Navier-Stokes equations over a wide Mach-number range uses, in conjunction with the strong conservation form of the governing equations, five unknown primitive variables. The numerical tests undertaken address steady convergent-divergent nozzle flows with air dissociation/recombination, dump combustor flows with n-pentane/air chemistry, and unsteady nonreacting cavity flows.

Shuen, Jian-Shun; Chen, Kuo-Huey; Choi, Yunho

1993-01-01

228

MEASURING CONTAMINANT FLUX THROUGH PLANTS BY FOURIER TRANSFORM INFRARED (FT-IR) SPECTROMETRY  

Microsoft Academic Search

Plants have a large capacity to transfer water and associated contaminants from soil to atmosphere. We measured the transfer rate for a range of constituents of gasoline that vary in volatility, solubility, and octanol\\/water partition coefficient. We tested benzene, toluene, ethyl benzene, meta-xylene, 1,2,4-trimethyl benzene, cyclohexene, n-pentane, ethyl ether, n-propyl ether, and t-butyl methyl ether. Aliphatic hydrocarbon constituents of gasoline

V. D. Makepeace; L. C. Davis; J. Dana; K. Selk; K. Smith; R. M. Hammaker; W. G. Fateley; L. E. Erickson

229

Numerical study of multicomponent droplet vaporization at near critical conditions  

NASA Technical Reports Server (NTRS)

A comprehensive numerical analysis of multicomponent droplet vaporization at near critical conditions has been carried out. The model is based on the full time-dependent conservation equations and accommodates various important high-pressure phenomena. As an example, the case involving a two-component (n-pentane and n-octane) fuel droplet in nitrogen gas is studied. The influences of transient effects, surface regression, ambient gas solubility, and phase-equilibrium relations on vaporization mechanisms are examined in detail.

Hsieh, Kwang-Chung; Shuen, Jian-Shun; Yang, Vigor

1988-01-01

230

COI Name COI Synonym CAS 1-Pentene 109-67-1  

E-print Network

,4-Bis(2-chloroethylthio)-n-butane 142868-93-7 1,5-Bis(2-chloroethylthio)-n-pentane 142868-94-8 1-Butene [Propane, 2,2-dimethyl-] 463-82-1 2-Butene 107-01-7 2-Butene-cis 590-18-1 2-Butene-trans [2-Butene, (E-98-2 2-Methyl-1-butene 563-46-2 2-Methylpropene [1-Propene, 2-methyl-] 115-11-7 2-Pentene, (E)- 646

Movileanu, Liviu

231

Temperature and moisture effect on spore emission in the fungal biofiltration of hydrophobic VOCs  

Microsoft Academic Search

The effect of temperature and moisture on the elimination capacity (EC), CO2 production and spore emission by Fusarium solani was studied in biofilters packed with vermiculite and fed with n- pentane. Three temperatures (15, 25 and 35°C) were tested and the highest average EC (64 g m h) and lower emission of spores (2.0 × 10 CFU m air) were obtained at

Alberto Vergara-Fernández; Vanida Salgado-Ísmodes; Miguel Pino; Sergio Hernández; Sergio Revah

2012-01-01

232

Nucleate and transition boiling in narrow horizontal spaces  

NASA Astrophysics Data System (ADS)

Nucleate and transition boiling are performed in a horizontal narrow space between a heated upward-facing copper disk and an unheated surface for saturated n-pentane. The heat flux and the wall temperature are determined by mean of an inverse heat conduction method. The influence of the confinement on the boiling curves and the flow patterns are analysed. Characteristic instabilities are observed at low heat flux and during the transition regime.

Stutz, Benoit; Lallemand, Monique; Raimbault, Fabien; Passos, Julio

2009-05-01

233

Elementary reconstitution of the water splitting light reaction in photosynthesis. 3. Photooxidative properties of chlorophyll dihydrate on metal as catalyst for water photolysis  

Microsoft Academic Search

The photooxidative properties of chlorophyll a dihydrate as photocatalyst for the water splitting reaction are examined using Pt and other metals as nonbiological catalysts for reaction product formation. The photoelectrodeposition of (Chl a 2HâO)\\/sub n\\/ microcrystals from n-pentane suspensions on Pt electrodes is described. The formation of a contiguous multilayer of (Chl a 2HâO)\\/sub n\\/ on Pt is examined by

Michael S. Showell; Francis K. Fong

1982-01-01

234

Elementary reconstitution of the water splitting light reaction in photosynthesis. 2. Optical double resonance study of (Chl a 2HâO)\\/sub n\\/ two-photon interactions in nonpolar solutions  

Microsoft Academic Search

Two-photon interactions of (Chl a 2HâO)\\/sub n\\/ in deaerated 1:1 n-pentane-methylcyclohexane solutions are investigated by fluorescence quenching measurements obtained by using time-resolved optical methods. The Chl a triplet state is populated by excitation with a modulated laser beam. The decay of the triplet population is monitored by measuring the quenching of Chl a fluorescence excited by a CW laser beam.

A. J. Alfano; F. K. Fong

1982-01-01

235

Development of a prototype low-temperature Rankine cycle electricity generation system  

Microsoft Academic Search

This paper describes the development of a small-scale system designed to generate electricity from low temperature heat (e.g., solar energy). The system operates on the Rankine cycle and uses n-pentane as the working fluid. A prototype system has been designed, constructed and tested. It is capable of delivering 1.5 kW of electricity with a thermal efficiency of 4.3%. Laboratory test

V. M. Nguyen; P. S. Doherty; S. B. Riffat

2001-01-01

236

High pressure nuclear magnetic resonance study of the dynamical solvent effects on the rotation of coordinated ethylene in an organometallic compound  

Microsoft Academic Search

The effect of temperature and pressure on the internal rotation rate of coordinated ethylene in ?–cyclopentadienylethylenetetrafluoroethylene–rhodium in liquid solution has been investigated by using 1H Fourier transform (FT) nuclear magnetic resonance spectroscopy. The solvents used in this study are n–pentane–d12, carbon disulfide, and methylcyclohexane–d14. The activation energy (13.4±0.2 kcal\\/mol) for the internal rotation of ethylene is independent of solvent and

Xiangdong Peng; Jiri Jonas

1990-01-01

237

Hydrophobic response of the fungus Rhinocladiella similis in the biofiltration with volatile organic compounds with different polarity.  

PubMed

Rhinocladiella similis biodegraded volatile organic compounds (VOCs) of different polarity in gas-phase biofilters. Elimination capacities, (EC) of 74 g(hexane) m(-3) h(-1), 230 g(ethanol) m(-3) h(-1), 85 g(toluene) m(-3) h(-1) and 30 g(phenol) m(-3) h(-1) were obtained. EC values correlated with the solubility of the VOCs. R. similis grown with n-hexane or ethanol in biofilters packed with Perlite showed that the surface hydrophobicity was higher with n-hexane than ethanol. The hydrophobin-like proteins extracted from the mycelium produced with n-hexane (15 kDa) were different from those in the ethanol biofilter (8.5 kDa and 7 kDa). PMID:19343504

Vigueras, Gabriel; Arriaga, Sonia; Shirai, Keiko; Morales, Marcia; Revah, Sergio

2009-08-01

238

Allelopathic potential of Artemisia arborescens: isolation, identification and quantification of phytotoxic compounds through fractionation-guided bioassays.  

PubMed

The aerial part of Artemisia arborescens L. (Asteraceae) was extracted with water and methanol, and both extracts were fractionated using n-hexane, chloroform, ethyl acetate and n-butanol. The potential phytotoxicity of both crude extracts and their fractions were assayed in vitro on seed germination and root growth of lettuce (Lactuca sativa L.), a sensitive species largely employed in the allelopathy studies. The inhibitory activities were analysed by dose-response curves and the ED 50 were estimated. Crude extracts strongly inhibited both germination and root growth processes. The fraction-bioassay indicated the following hierarchy of phytotoxicity for both physiological processes: ethyl acetate ? n-hexane > chloroform ? n-butanol. On the n-hexane fraction, GC-MS analyses were carried out to characterise and quantify some of the potential allelochemicals. Twenty-one compounds were identified and three of them, camphor, trans-caryophyllene and pulegone were quantified. PMID:22687059

Araniti, Fabrizio; Lupini, Antonio; Sorgonà, Agostino; Conforti, Filomena; Marrelli, Mariangela; Statti, Giancarlo Antonio; Menichini, Francesco; Abenavoli, Maria Rosa

2013-01-01

239

Isolation of Aurantiamides from Gomphrena Celosioides C. Mart  

PubMed Central

In West Africa and Nigeria in particular, many virgin plants are still waiting to be evaluated for their medicinal importance. Claims of plants with folk medicinal applications need to be evaluated and verified. Gomphrena celosioides (family – Amaranthaceae) is a weed grown in lawns and the biological activity of the extract had earlier been established. In the present study, the plant was collected, air dried, ground and soxhlet extracted with n-hexane and two compounds were isolated from the flakes that were recovered from the n-hexane extract on cooling. Column chromatography using 5% chloroform in n-hexane effected the separation. The structures of the isolated compounds were elucidated by spectroscopic analysis using IR, NMR (1H and 13C) and EI-MS. The compounds were found to be aurantiamide and aurantiamide acetate. This is the first report of isolation of these compounds in Gomphrena celosioides. PMID:24734065

Olutola Dosumu, Omotayo; Onocha, Patricia; Ekundayo, Olusegun; Ali, Muhammad

2014-01-01

240

Influence of EGR compounds on the oxidation of an HCCI-diesel surrogate  

E-print Network

This paper presents an experimental and numerical study of the impact of various additives on the oxidation of a typical automotive surrogate fuel blend, i.e. n-heptane and toluene. It examines the impact of engine re-cycled exhaust has compounds on the control of an Homogeneous Charge Compression-Ignition (HCCI) engine. Series of experiments were performed in a hihly diluted Jet-Stirred Reactor (JDR) at pressures of 1 and 10 atm (1 atm = 101,325 Pa). The chosen thermo-chemical conditions were close to those characteristices of the pre-ignition period in an HCCI engine. The influence of various additives, namely nitric oxide (NO), ethylene (C2H4) and methanol (CH3OH), on the oxidation of a n-heptane/toluene blend was studied over a wide range of temperatures (550-1100 K), including the zone of the Negative Temperature Coefficient (NTC).

Anderlohr, Jörg; Da Cruz, A Pires; Bounaceur, Roda; Battin-Leclerc, Frédérique; Dagaut, Philippe; Montagne, X; 10.1016/j.proci.2008.06.019

2009-01-01

241

Autoignition of gasoline surrogates mixtures at intermediate temperatures and high pressures  

SciTech Connect

Ignition times were determined in high-pressure shock-tube experiments for various stoichiometric mixtures of two multicomponent model fuels in air for the validation of ignition delay simulations based on chemical kinetic models. The fuel blends were n-heptane (18%)/isooctane (62%)/ethanol (20%) by liquid volume (14.5%/44.5%/41% by mole fraction) and n-heptane (20%)/toluene (45%)/isooctane (25%)/diisobutylene (10%) by liquid volume (17.5%/55%/19.5%/8.0% by mole fraction). These fuels have octane numbers comparable to a standard European gasoline of 95 RON and 85 MON. The experimental conditions cover temperatures from 690 to 1200 K and pressures at 10, 30, and 50 bar. The obtained ignition time data are scaled with respect to pressure and compared to previous results reported in the literature. (author)

Fikri, M.; Herzler, J.; Starke, R.; Schulz, C.; Roth, P. [IVG, Universitaet Duisburg-Essen, D-47048 Duisburg (Germany); Kalghatgi, G.T. [Shell Global Solutions U.K., P.O. Box 1, Chester CH1 3SH (United Kingdom)

2008-01-15

242

Investigation of atmospheric pressure capillary non-thermal plasmas and their applications to the degradation of volatile organic compounds  

NASA Astrophysics Data System (ADS)

Atmospheric pressure capillary non-thermal plasma (AP-CNTP) has been investigated as a potential technology far the removal of volatile organic compounds (VOCs) in Advanced Life Support Systems (ALS). AP-CNTP is a destructive technology far the removal of VOCs from air streams by active plasma species, such as electrons, ions, and excited molecules. Complete VOC destruction ideally results in the formation of water, carbon dioxide (CO2), and other by-product's may also form, including ozone (O3), nitrous oxide (N2O), nitrogen dioxide (NO2), and decomposed hydrocarbons. Several organic compounds, such as BTEX, ethylene, n-heptane, isooctane, methanol and NH3, were tested in an AP-CNTP system. Parametric experiments were carried out by varying plasma discharge power, flowrates, and initial concentrations. The degradation efficiency varied depending on the chemical nature of the compounds. A plasmochemical kinetic model was derived for toluene, ethylbenzene, and m-xylene and n-heptane.

Yin, Shu-Min

243

Instrumental studies on silicone oil adsorption to the surface of intraocular lenses  

NASA Astrophysics Data System (ADS)

The purpose of this study was to examine the degree of adherence of silicone oil to various intraocular lenses (IOLs) through comparison of the physico-chemical properties of the oil and IOLs. Four kinds of IOLs comprising various biomaterials were examined: PMMA (720A™), PHEMA (IOGEL 1103™), Acrysof (MA60BM™), and silicone (SI30NB™). Each lens was immersed in silicone oil or carboxylated silicone (CS-PDMS) oil for 72 h. For determination of the changes in chemical and elemental compositions on the surfaces of IOLs caused by the contact with silicone oil, IOLs were washed and rinsed with n-pentane to remove as much of the adsorbed silicone oil as possible, then subjected to Fourier transform infrared spectroscopic (FTIR) and X-ray photoelectron spectroscopic (XPS) analyses. The results of FTIR studies strongly indicate that washing with n-pentane completely removed the adhered silicone oil on the surfaces of PHEMA and Acrysof IOLs, whereas the residual silicone oil was detected on the surfaces of PMMA and silicone IOLs. XPS studies showed that silicone oil coverage of PMMA lenses was 12%, even after washing with n-pentane. In the case of silicone IOLs, the relative O1s peak area of carboxyl group in the residual CS-PDMS oil was found to be ˜2.7%. Considering that 2.8% carboxyl group-substituted silicone oil was used in the present study, CS-PDMS oil covered the entire surface of the silicone IOLs.

Kim, Chun Ho; Joo, Choun-Ki; Chun, Heung Jae; Yoo, Bok Ryul; Noh, Dong Il; Shim, Young Bock

2012-12-01

244

Simple solvothermal synthesis of hydrophobic magnetic monodispersed Fe{sub 3}O{sub 4} nanoparticles  

SciTech Connect

Graphical abstract: A facile method to produce monodispersed magnetite nanoparticles is based on the solvothermal reaction of iron acetylacetonate (Fe(acac)3) decomposition. The sizes ranged from 7 to 12 nm, which could be controlled by adjusting the volume ratio of oleylamine to n-hexane. Display Omitted Highlights: ? The solvethermal reaction of Fe(acac){sub 3} decomposition was carried out at mild temperature in the presence of oleylamine and n-hexane. ? The size of nanocrystals is controlled by adjusting the volume ratio of oleylamine to n-hexane. ? The low-boiling-point solvent n-hexane offered autogenous pressure parameter after gasified in the reaction temperature. ? The as prepared hydrophobic monodisperse Fe{sub 3}O{sub 4} NPs can be used to prepare the magnetic micelles for future biomedical applications. -- Abstract: A new solvothermal method is proposed for the preparation of Fe{sub 3}O{sub 4} nanoparticles (NPs) from iron acetylacetonate in the presence of oleylamine and n-hexane. The products are characterized by X-ray powder diffraction, infrared (IR) spectroscopy, transmission electron microscopy, thermogravimetry/differential thermogravimetry (TG/DTG) analysis, and vibrating sample magnetometery. The new procedure yields superparamagnetic monodispersed Fe{sub 3}O{sub 4} particles with sizes ranging from 7 nm to 12 nm. The nanocrystal sizes are controlled by adjusting the volume ratio of oleylamine to n-hexane. IR and TG/DTG analyses indicate that the oleylamine molecules, as stabilizers, are adsorbed on the surface of Fe{sub 3}O{sub 4} NPs as bilayer adsorption models. The surface adsorption quantities of oleylamine on 7.5 and 10.4 nm-diameter Fe{sub 3}O{sub 4} NPs are 18% and 11%, respectively. The hydrophobic surface of the obtained nanocrystals is passivated by adsorbed organic solvent molecules. These molecules provide stability against agglomeration, enable solubility in nonpolar solvents, and allow the formation of magnetic polymer micelles.

Liu, Jing; Wang, Lu [School of Pharmaceutical Sciences, Hebei Medical University, Shijiazhuang 050017 (China)] [School of Pharmaceutical Sciences, Hebei Medical University, Shijiazhuang 050017 (China); Wang, Jing, E-mail: Jingwang@home.ipe.ac.cn [School of Pharmaceutical Sciences, Hebei Medical University, Shijiazhuang 050017 (China)] [School of Pharmaceutical Sciences, Hebei Medical University, Shijiazhuang 050017 (China); Zhang, Lantong, E-mail: zhanglantong@263.net [School of Pharmaceutical Sciences, Hebei Medical University, Shijiazhuang 050017 (China)] [School of Pharmaceutical Sciences, Hebei Medical University, Shijiazhuang 050017 (China)

2013-02-15

245

Ignition Delays of Alkyl Thiophosphites with White and Red Fuming Nitric Acids Within Temperature Range 80 to -105 F  

NASA Technical Reports Server (NTRS)

Ignition delays of alkyl thiophosphites were obtained in a modified open-cup apparatus and a small-scale rocket engine apparatus. At -40 F, mixed alkyl thiophosphites gave short delays with white fuming nitric acid containing 2 percent water and red fuming nitric acids of widely varying compositions. At -40 F and higher, triethyl trithiophosphite blended with as much as 40 percent n-heptane gave satisfactory self-igniting properties at temperatures as low as -76 F.

Miller, Riley O; Ladanyi, Dezso J

1953-01-01

246

Influence of rare earth elements La, Nd and Yb on the acidity of H-MCM-22 and H-Beta zeolites  

Microsoft Academic Search

The influence of rare earth (RE) elements on the acidic properties of H-MCM-22 and H-Beta was studied by pyridine adsorption followed by infrared spectroscopy (FTIR) and n-heptane cracking, as a model reaction.The zeolites were submitted to ion exchange with rare earth nitrate solutions of La, Nd and Yb. The FTIR spectra of REH-MCM-22 indicate the presence of RE elements inside

Angela Martins; João M. Silva; Carlos Henriques; Fernando Ramôa Ribeiro; M. Filipa Ribeiro

2005-01-01

247

Average structural analysis of tar obtained from pyrolysis of wood  

Microsoft Academic Search

Conventional analytical methods such as 1H NMR, vapor pressure osmometry (VPO) and elemental analysis were used to characterize the tar obtained from pyrolysis of pine.The major fraction of tar obtained during pyrolysis of pine at different temperatures was the insoluble fraction in n-heptane which corresponds to asphaltenes; this fraction was characterized and analyzed using average structural parameters. The structural unit

Diana López; Nancy Acelas; Fanor Mondragón

2010-01-01

248

Effects of synthesis parameters on the physico-chemical and photoactivity properties of titania–silica mixed oxide prepared via basic hydrolyzation  

Microsoft Academic Search

Titania–silica mixed oxide (TiO2–SiO2) was prepared from the alkoxides: titanium tetrabutoxide (TBOT) and tetraethyl orthosilicate (TEOS), by using an ammonia–water solution as the hydrolysis catalyst. Variables included synthesis route, aging time, the type of alcohol, and calcination temperature. The materials were then evaluated as photocatalysts for the decomposition of n-heptane. Experimental results revealed: (1) the photoactivity of TiO2–SiO2 prepared via

Qiujing Yang; Chao Xie; Zili Xu; Zhongmin Gao; Ziheng Li; Dejun Wang; Yaoguo Du

2005-01-01

249

On the Collision of a Droplet with a Solid Surface  

Microsoft Academic Search

The collision dynamics of a liquid droplet on a solid metallic surface were studied using a flash photographic method. The intent was to provide clear images of the droplet structure during the deformation process. The ambient pressure (0.101 MPa), surface material (polished stainless steel), initial droplet diameter (about 1.5 mm), liquid (n-heptane) and impact Weber number (43) were fixed. The

S. Chandra; C. T. Avedisian

1991-01-01

250

EXTRACTION OF RARE EARTH METALS WITH 2-ETHYLHEXYL PHOSPHONIC ACID MONO2-ETHYLHEXYL ESTER IN THE PRESENCE OF DIETHYLENETRIAMINEPENTAACETIC ACID IN AQUEOUS PHASE  

Microsoft Academic Search

The extraction equilibria of rare earth metals with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (commercial name, PC-88A, henceforth abbreviated as HR) dissolved in n-heptane were measured at 303 K. It was found that rare earth metals are extracted with the dimer of the extractant, (HR)2, as follows.The extraction equilibrium constants of metals were obtained and compared with the extraction equilibrium constants

Fukiko Kubota; Masahiro Goto; Fumiyuki Nakashio

1993-01-01

251

Extraction Kinetics of Rare Earth Metals with 2-Ethylhexyl Phosphonic Acid Mono2-ethylhexyl Ester Using a Hollow Fiber Membrane Extractor  

Microsoft Academic Search

A kinetic study concerning chemical complexation-based solvent extraction of rare earth metals with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester dissolved as an extractant in n-heptane was carried out using a microporous hydrophobic hollow fiber membrane extractor. The effects of concentration of chemical species in aqueous and organic feed solutions on the apparent permeabilities of metal species for extraction and stripping, respectively,

Fukiko Kubota; Masahiro Goto; Fumiyuki Nakashio; Tadashi Hano

1995-01-01

252

Biotechnological Utilisation of Fusel Oil, A Food Industry By-Product A Kinetic Model on Enzymatic Esterification of i-Amyl Alcohol and Oleic Acid by Candida antarctica Lipase B  

Microsoft Academic Search

Summary Fusel oil is a by-product of distilleries, its main component is i-amyl alcohol, which can form ester compounds. Esterification of oleic acid and i-amyl alcohol by Candida antarctica lipase B (Novozym 435 preparation) in n-heptane solvent was studied in this work. Ping- -pong bi-bi mechanism (inhibition phenomena taken into account) was applied as a com- plex kinetic model. The

Nándor Nemestóthy; László Gubicza; Erika Fehér; Katalin Bélafi-Bakó

253

Simulation of Surface Excess Concentrations for a Binary Hydrocarbon Mixture on Graphite  

Microsoft Academic Search

We perform Molecular Dynamics simulations of thin hydrocarbon films adsorbed on the basal plane of graphite to determine structural and thermodynamic properties. Specifically we study the behaviour of liquid benzene\\/n-heptane mixtures. The intra adsorbate and the adsorbate-substrate interactions are described using a phenomenological force field whose careful parameterization will be reported in a following paper. The foremost quantity we calculate

Bernd Fodi; Reinhard Hentschke

1997-01-01

254

UV?Guided Isolation of Fungal Metabolites by HSCCC  

Microsoft Academic Search

Analytical standardised reversed phase liquid chromatography (RPLC) data can be helpful in finding a suitable solvent combination for isolation of fungal metabolites by high?speed counter current chromatography. Analysis of the distribution coefficient (KD) of fungal metabolites in a series of biphasic systems consisting of n?heptane–ethyl acetate (EtOAc)–methanol (MeOH)–water has been used to illustrate the relationship between the RPLC retention indexes

Petur W. Dalsgaard; Kristian F. Nielsen; Thomas O. Larsen

2005-01-01

255

Solvent effects on hydrogen bonding between 1-pentanol and butyl methacrylate  

Microsoft Academic Search

The hydrogen bonding between 1-pentanol and butyl methacrylate (BMA) was investigated in n-heptane, CCl4, and benzene as solvents by using FTIR spectroscopic method. Utilizing Nash method the formation constant and free energy change of 1?:?1 complexes has been determined. The results show a significant dependence of the association constant upon the solvents used. The solvent effect on the formation of

K. Dharmalingam; K. Ramachandran

2006-01-01

256

Extraction Equilibrium of Dicarboxylic Acids with Tertiary Amine in Single and Binary Diluents  

Microsoft Academic Search

The extraction equilibria of aliphatic dicarboxylic acids with solutions of trialkylamine (TAA) in binary diluents were measured and compared. Oxalic, succinic, DL?malic and D?tartaric acids were used. Trialkylamine with C7–C9 carbon atom chains was dissolved in 1?octanol, methyl?isobutyl ketone (MIBK), and chloroform, or in their binary mixtures with n?heptane. Physical extraction with pure active diluents also was measured. The contribution

Jaroslav Procházka; Aleš Heyberger; Eva Volaufová

2005-01-01

257

Extraction of citric acid with tertiary amine—third-phase formation  

Microsoft Academic Search

The conditions of third-phase formation in the system made up of aqueous solution of citric acid-solution of trialkylamine in a binary diluent were studied. As binary diluents mixtures of octanol-1 or chloroform with n-heptane were used. The experiments were carried out in water-free systems, at 25°C under the limiting condition of amine fully loaded with acid, thus simulating extraction form

Aleš Heyberger; Jaroslav Procházka; Eva Volaufova

1998-01-01

258

Reactive extraction of lactic acid with mixed tertiary amine extractants  

Microsoft Academic Search

The mixture of tripropylamine (TPA) and trioctylamine (TOA) dissolved in 1-octanol\\/n-heptane was used in the reactive extraction of (L+)lactic acid in aqueous solution. Maximum distribution coefficients were obtained in the range from 6:4 to 8:2 weight ratio of TPA\\/TOA at 5% (w\\/w) lactic acid in aqueous phase and their extraction efficiencies were above 90%. By introducing TPA into TOA, the

Yeon Ki Hong; Won Hi Hong

1999-01-01

259

Hydrocarbon fuel cooling technologies for advanced propulsion  

Microsoft Academic Search

Storable hydrocarbon fuels that undergo endothermic reaction provide an attractive heat sink for future high-speed aircraft. An investigation was conducted to explore the endothermic potential of practical fuels, with inexpensive and readily available catalysts, under operating conditions simulative of high-speed flight applications. High heat sink capacities and desirable reaction products have been demonstrated for n-heptane and Norpar 12 fuels using

D. R. Sobel; L. J. Spadaccini

1997-01-01

260

Exploitation of reversed micelles as a medium in mimetic peroxidase-catalyzed fluorogenic reaction between hydrogen peroxide and l-tyrosine  

Microsoft Academic Search

The peroxidase activity of mimetic enzyme, iron tetrasulfonatophthalocyanine (FeTSPc), was characterized in reversed micelles of hexadecyltrimethylammonium bromide (CTAB) formed in n-heptane–n-pentanol solution (2:1, V:V). The assay is based on its catalytic effect on the oxidation reaction of l-tyrosine (l-tyr) by hydrogen peroxide. The influences of environmental factors, such as the water content, CTAB concentration and pH, on the peroxidase activity

Xiao-Lan Chen; Ling Wei; Huang-Hao Yang; Qing-Zhi Zhu; Jin-Gou Xu

2002-01-01

261

Simultaneous Determination of Nalbuphine and Opiates in Human Hair by Gas Chromatography-Mass Spectrometry  

Microsoft Academic Search

The method for simultaneous determination of nalbuphine and opiates (codeine, morphine, and 6-monoacetylmorphine) in human hair was developed in the selected-ion monitoring (SIM) mode of a gas chromatography-mass spectrometer (GC-MS). Thirty-milligram hair samples were incubated in 0.01 M HCl overnight at 50 °C. We extracted the drugs from resulting hydrolyzed solutions with a mixture of chloroform-isopropanol- n-heptane (50:17:33, v\\/ v\\/

Jin Young Kim; Moon Kyo In; Ki-Jung Paeng; Bong Chul Chung

2004-01-01

262

Hindered diffusion of petroleum-derived asphaltenes  

Microsoft Academic Search

Diffusion coefficients of petroleum asphalatenes of molecular weight 2000 to 64,000 in small pores were measured using a model porous system. Mica membranes were prepared by a track-etch process to yield parallel pores of identical geometry. Initial experiments were conducted to measure diffusion rates of linear hydrocarbons of known diffusivity in n-heptane, methanol, isopropanol and tetrahydrofuran (THF) solvents and yielded

Baltus

1982-01-01

263

Evaluation of hepatoprotective activity of Cassia fistula leaf extract  

Microsoft Academic Search

Hepatoprotective activity of the n-heptane extract of Cassia fistula leaves was investigated in rats by inducing hepatotoxicity with carbon tetrachloride:liquid paraffin (1:1). The extract has been shown to possess significant protective effect by lowering the serum levels of transminases (SGOT and SGPT), bilirubin and alkaline phosphatase (ALP). The extract of C. fistula at a dose of 400 mg\\/kg showed significant

T. Bhakta; Pulok K. Mukherjee; Kakali Mukherjee; S. Banerjee; Subhash C. Mandal; Tapan K. Maity; M. Pal; B. P. Saha

1999-01-01

264

Experiments And Model Development For The Investigation Of Sooting And Radiation Effects In Microgravity Droplet Combustion  

NASA Technical Reports Server (NTRS)

This study involves flight experiments (for droplets between 1.5 to 5 mm) and supportive ground-based experiments, with concurrent numerical model development and validation. The experiments involve two fuels: n-heptane, and ethanol. The diagnostic measurements include light extinction for soot volume fraction, two-wavelength pyrometry and thin-filament pyrometry for temperature, spectral detection for OH chemiluminescence, broadband radiometry for flame emission, and thermophoretic sampling with subsequent transmission electron microscopy for soot aerosol property calculations.

Yozgatligil, Ahmet; Choi, Mun Young; Dryer, Frederick L.; Kazakov, Andrei; Dobashi, Ritsu

2003-01-01

265

Isolation and Identification of Phenolic Compounds in the Fruit of Benincasa hispida by HSCCC  

Microsoft Academic Search

Separation of phenolic components from the fruit Benincasa hispida was conducted using high?speed countercurrent chromatography (HSCCC) with two solvent systems, n?hexane–n–butanol–methanol–water (10:16:5:20, v\\/v) and n?hexane–ethyl acetate–methanol–water (1:1:1:1, v\\/v). Three compounds, astilbin (120 mg), catechin (103 mg), and naringenin (79 mg) were obtained from the separation of 2 g of crude phenolic component extract of the fruit. Chemical structures of these three compounds were confirmed

Qizhen Du; Qi Zhang; Yoichiro Ito

2005-01-01

266

New anti-inflammatory triterpene from the root of Ricinus communis.  

PubMed

Liquid-liquid partitioning of Ricinus communis root methanol extract resulted in enrichment of compounds. Purification of the n-hexane fraction led to the isolation and characterisation of two triterpenes: one known compound lupeol (1) and a new diketone pentacyclic triterpene named as erandone (urs-6-ene-3,16-dione) (2), from the plant. Their structures were determined by various spectroscopic techniques. Crude methanolic, enriched n-hexane fraction and isolates at doses 100 mg/kg p.o. exhibited significant (P < 0.001) anti-inflammatory activity in carrageenan-induced hind paw oedema model. PMID:24279342

Srivastava, Pooja; Jyotshna; Gupta, Namita; Maurya, Anil Kumar; Shanker, Karuna

2014-01-01

267

Induction and functional role of cytochromes P450 in the filamentous fungi Mortierella alpina ATCC 8979 and Cunninghamella blakesleeana DSM 1906 during hydroxylation of cycloalkylbenzoxazoles  

Microsoft Academic Search

The occurrence and regulation of cytochrome P450 (P450) in Mortierella alpina and Cunninghamella blakesleeana have been studied to elucidate the enzymatic basis by which 2-cyclopentyl-1,3-benzoxazole is hydroxylated to 3-(benz-1,3-oxazol-2-yl)cyclopentan-1-ol\\u000a by these organisms. The occurrence of P450 in M. alpina was first been shown after induction with n-hexane. An assay protocol was developed with n-hexane-induced cells and adapted to the handling

O. Asperger; H. Steinbrenner; A. Lehmann; M. Petsch; H. Griengl

1999-01-01

268

Evaporation and discharge dynamics of highly charged droplets of heptane, octane, and p-xylene generated by electrospray ionization.  

PubMed

We report studies of the evaporation and discharge dynamics of highly charged droplets generated by electrospray ionization from n-heptane, n-octane, and p-xylene doped with Stadis-450, a conductivity-enhancing agent. A phase Doppler anemometer (PDA) characterizes individual droplets moving through the uniform electric field within an ion mobility cell according to size, velocity, and charge. Repeated reversal of the electric field allows multiple PDA measurements on selected droplets with diameters ranging from 3 to 60 microm and up to 10(7) elementary positive charges. This "ping-pong" technique provides individual droplet histories from which we determine the dynamics of solvent evaporation and charge loss. On average, n-heptane discharges at 101% of the Rayleigh limit of charge, while n-octane and p-xylene droplets discharge at 87% and 89% of their respective limits. Discharge events release an average of 19% of the charge in n-heptane and 17% of the charge in both n-octane and p-xylene. Within the limits of the measurements, no detectable change in droplet diameter accompanies observed discharge events, indicating the loss of a relatively small fraction of the total volume. We compare these results to previous experiments, theoretical models for droplet evaporation and discharge, and predictions from the Rayleigh model. We report both Stadis-450 and triethylamine mass spectra in octane and discuss issues regarding the use of hydrocarbon solvents in electrospray mass spectrometry. PMID:12510751

Grimm, Ronald L; Beauchamp, J L

2002-12-15

269

Stability and aerosolization of pressurized metered dose inhalers containing thymopentin nanoparticles produced using a bottom-up process.  

PubMed

The objective of this study was to investigate the stability and aerosolization of pressurized metered dose inhalers (pMDIs) containing thymopentin nanoparticles. Thymopentin nanoparticles, fabricated by a bottom-up process, were suspended in hydrofluoroalkane (HFA) 134a together with cineole and/or n-heptane to produce pMDI formulations. The stability study of the pMDIs obtained was carried out at ambient temperature for 6 months. The amount of thymopentin and the aerosolization properties of pMDIs were determined using high-performance liquid chromatography (HPLC) and a twin-stage impinger (TSI), respectively. Based on the results, thymopentin nanoparticles were readily suspended in HFA 134a with the aid of cineole and/or n-heptane to form physically stable pMDI formulations, and more than 98% of the labeled amount of thymopentin and over 50% of the fine particle fraction (FPF) of the pMDIs were achieved. During storage, it was found that for all pMDIs more than 97% of the labeled amount of thymopentin and FPF greater than 47% were achieved. Moreover, the size of thymopentin nanoparticles in propellant containing cineole and n-heptane showed little change. It is, therefore, concluded that the pMDIs comprising thymopentin nanoparticles developed in this study were stable and suitable for inhalation therapy for systemic action. PMID:22343132

Tan, Yinhe; Yang, Zhiwen; Pan, Xin; Chen, Meiwan; Feng, Min; Wang, Lili; Liu, Hu; Shan, Ziyun; Wu, Chuanbin

2012-05-10

270

Fuel-Specific Effect of Exhaust Gas Residuals on HCCI Combustion: A Modeling Study  

SciTech Connect

A modeling study was performed to investigate fuel-specific effects of exhaust gas recirculation (EGR) components on homogeneous charge compression ignition (HCCI) combustion at conditions relevant to the negative valve overlap (NVO) strategy using CHEMKIN-PRO. Four single-component fuels with well-established kinetic models were chosen: n-heptane, iso-octane, ethanol, and toluene. These fuels were chosen because they span a wide range of fuel chemistries, and produce a wide compositions range of complete stoichiometric products (CSP). The simulated engine conditions combined a typical spark ignition engine compression ratio (11.34) and high intake charge temperatures (500-550 K) that are relevant to NVO HCCI. It was found that over the conditions investigated, all the fuels had overlapping start of combustion (SOC) phasing, despite the wide range in octane number (RON = 0 to 120). The effect of the EGR components CO2 and H2O was to suppress the compression temperature because of their higher heat capacities, which retarded SOC. For a concentration of O2 higher than the stoichiometric amount, or excess O2, there was an effect of advancing SOC for n-heptane, iso-octane, and toluene, but SOC for ethanol was not advanced. Low temperature heat release (LTHR) for n-heptane was also found to be highly dependent on excess O2, and mild endothermic reaction was observed for cases when excess O2 was not present.

Szybist, James P [ORNL

2008-01-01

271

In-vitro cytotoxicity (LC 50 ) of extracts obtained from the seeds of Zea mays  

Microsoft Academic Search

Zea mays was tested for cytotoxicity (LC50) efficacy against brine shrimp via extracts obtained from soxhlation using methanol, ethyl aectate, n-hexane, n-butanol solvent and one pure fraction. The in-vitro cytotoxicity (LC50) activity was performed by brine shrimp lethality bioassay. Among these extracts, ethyl acetate, hexane and pure compounds have been found to be effective.

M. Amzad Hossain; Taslim Ferdous; S. M. Salehuddin; A. K. Das

2009-01-01

272

New Perspectives for light alkanes isomerization. Robert Hubaut*  

E-print Network

palladium (or nickel)-cerium oxides and silica-supported HPAs have been realized and tested for the n-hexane isomerization. The solids were characterized before and after tests. Presence of Pt, Pd (or nickel) and Ce gives, the activity is in the same order as the acid strength. 1 H and 31 P solid-state NMR of trimethyl phosphine

Paris-Sud XI, Université de

273

Protective effect of tomato against adrenaline-induced myocardial infarction in rats  

Microsoft Academic Search

Lycopene, a carotenoid rich in tomato fruit (ripe), is an effective antioxidant and free radical scavenger. In this study n-hexane extract of tomato was evaluated for its protective action against oxidative stress in experimental myocardial infarction induced by administration of adrenaline in rats. Adrenaline produced significant elevation of malondialdehyde content of heart, an indicator of lipid peroxidation, with a significant

Roksana Parvin; Nargis Akhter

2008-01-01

274

Cancer-suppressive potential of extracts of endemic plant Helichrysum zivojinii: effects on cell migration, invasion and angiogenesis.  

PubMed

Helichrysum zivojinii Cernjavski & Soska is an endemic plant species that grows in the National Park Galicica in Macedonia. Five extracts were isolated as fractions from the aerial parts of the plant: a n-hexane extract (1), a dichloromethane extract (2), an ethyl-acetate extract (3), a n-butanol extract (4) and a methanol extract (5). A dose-dependent cytotoxic activity of the extracts on MDA-MB-231 and EA.hy926 cells was observed. Extracts exhibited more pronounced cytotoxic actions on MDA-MB-231 cells than on EA.hy926 cells. The n-hexane extract (1), at a non-toxic concentration, exhibited an inhibitory effect on the migration as well the invasiveness of MDA-MB-231 cells. The dichloromethane extract (2), at a non-toxic concentration, demonstrated inhibition of MDA-MB-231 cells invasion. Each of the five extracts applied at non-toxic concentrations inhibited migration of EA.hy926 cells. The prominent inhibitory effect of the n-hexane extract on EA.hy926 cells migration was associated with a notable anti-angiogenic action of this extract. The other four tested extracts demonstrated mild anti-angiogenic activity. Our data highlight the prominent anticancer potential of n-hexane (1) and dichloromethane (2) extracts, which could be attributed to their very pronounced and selective cytotoxic activities as well as their anti-invasive and anti-angiogenic properties. PMID:24273869

Mati?, Ivana Z; Aljanci?, Ivana; Vajs, Vlatka; Jadranin, Milka; Gligorijevi?, Nevenka; Milosavljevi?, Slobodan; Jurani?, Zorica D

2013-09-01

275

Identification of an anticancer compound against HT-29 cells from Phellinus linteus grown on germinated brown rice  

PubMed Central

Objective To isolate and identify the anticancer compound against proliferation of human colon cancer cells from ethyl acetate (EtOAC) extract of Phellinus linteus grown on germinated brown rice (PB). Methods EtOAC extract of PB was partitioned with n-hexane, EtOAC, and water-saturated n-butanol. Anticancer compound of n-hexane layer was isolated and identified by HPLC and NMR, respectively. Cytotoxicity against HT-29 cells was tested by SRB assay. Results The n-hexane layer obtained after solvent fractionation of PB EtOAC extracts showed a potent anticancer activity against the HT-29 cell line. Atractylenolide I, a eudesmane-type sesquiterpene lactone, a major anticancer substance of PB, was isolated from the n-hexane layer by silica gel column chromatography and preparative-HPLC. This structure was elucidated by one- and two-dimensional NMR spectroscopic data. Atractylenolide I has not been reported in mushrooms or rice as of yet. The isolated compound dose-dependently inhibited the growth of HT-29 human colon cancer cells. Conclusions Atractylenolide I might contribute to the anticancer effect of PB. PMID:24075343

Jeon, Tae-Il; Jung, Chang-Hwa; Cho, Jeong-Yong; Park, Dong Ki; Moon, Jae-Hak

2013-01-01

276

Coumarins from Zosima absinthifolia seeds, with allelopatic effects  

Microsoft Academic Search

Zosima absinthifolia belongs to the Apiaceae family and is found in Iran, Turkey, Iraq and different countries of the Caucasus, Middle East and Central Asia. The fruits are used as food flavoring and as a food spice in Iran. In the present work, an n-hexane extract of the plant seeds was purified by vacuum liquid chromatography and preparative TLC for

Seyed Mehdi RAZAVI; Gholamhassan IMANZADEH; Mahdi DAVARI

2010-01-01

277

UNIVERSITE DE BOURGOGNE Equipe EMMA EA 581-IUVV Institut Jules Guyot  

E-print Network

-forming matrices based on iota-carrageenan or sodium alginate. Microstructure, emulsion granulometry, thermal, alcohols, keton) have been measured. When n-hexanal is added in the carrageenan matrix, it modifies to the interaction between aldehyde group of the aroma compound and OH and sulphate groups of the carrageenans which

Paris-Sud XI, Université de

278

Solution scattering studies of the hierarchical assembly of porphyrin trimers based on benzene triscarboxamide.  

PubMed

The self-assembly of achiral and chiral porphyrin trimers based on benzene triscarboxamide in solution is studied with the help of NMR, FT-IR, UV-vis, and CD spectroscopy. These studies revealed that in apolar solvents the porphyrin trimers self-assembled in columnar stacks via a combination of hydrogen bonding and ?-? stacking interactions. While the critical aggregation constant is about 0.2 mM in chloroform, aggregation already occurs at micromolar concentrations in n-hexane. Small angle neutron scattering (SANS) studies in chloroform, toluene, and n-hexane confirmed aggregation of the trimers into columnar stacks. In chloroform and n-hexane, but not in toluene, the trimers gelated the solvent. In chloroform the stacks of the achiral trimer were found to contain on average about 70 molecules, while in toluene the stacks were much smaller and contained on average 7-9 molecules. In n-hexane the SANS studies revealed that the chiral trimer formed a gel with an average mesh size of the transient network of chains of approximately 90 nm, with chains being built up from effective cylindrical aggregates with an average length of 20 nm. PMID:25363515

van Hameren, Richard; van Buul, Arend M; Visser, Dirk; Heenan, Richard K; King, Stephen M; Rowan, Alan E; Nolte, Roeland J M; Pyckhout-Hintzen, Wim; Elemans, Johannes A A W; Feiters, Martin C

2014-11-19

279

Nature and reactivity of hexane soot  

Microsoft Academic Search

Soot produced from the combustion of fossil fuels, widely distributed in the atmosphere, is significantly different from most carbons for which the surface structure and\\/or reactivity have been studied. Soot derived from the combustion of reagent n-hexane has been chosen as a laboratory model of petroleum fuel for the purpose of this study. The composition and surface structure of hexane

Akhter

1984-01-01

280

Human Polymorphonuclear Leukocyte Chemotaxis as a Tool in Detecting Biological Early Effects in Workers Occupationally Exposed to Low Levels of n-HeXane  

Microsoft Academic Search

Human polymorphonuclear leukocytes (PMN) were chosen to measure two cellular end points- chemotaxis and respiratory burst - and to verify whether they could function as biomarkers of early effect in detecting occupational exposure to n-hexane of apparently healthy shoe workers, without any electroneuromyographic (ENMG) abnormality.Chemotaxis, but not respiratory burst, was found to be impaired. A negative linear correlation between chemotaxis

Mario Governa; Matteo Valentino; Isabella Visanà; Francesca Monaco

1994-01-01

281

Solubility and Flory Huggins parameters of SBES, poly(styrene-b-butene\\/ethylene-b-styrene) triblock copolymer, determined by intrinsic viscosity  

Microsoft Academic Search

Solubility parameter and Flory Huggins interaction parameter of a triblock SBES have been obtained from intrinsic viscosity measurements. The solubility of the block copolymer in all solvents (methyl-cyclohexane, cyclohexane, cyclopentane, toluene and benzene) was found good except in the case of n-hexane. The results obtained are similar to other found in literature for SBR and SBS rubbers, and indicate that

G. Ovejero; P. Pérez; M. D. Romero; I. Guzmán; E. D?´ez

2007-01-01

282

VANADIUM PHOSPHORUS OXIDE AS AN EFFICIENT CATALYST FOR HYDROCARBON OXIDATIONS USING HYDROGEN PEROXIDE  

EPA Science Inventory

Calcined vanadium phosphorus oxide (VPO) prepared by an organic route is found to be an efficient catalyst for the oxidation of various alkanes such as cyclopentane, cyclohexane, n-hexane, cycloheptane, cyclooctane, cyclodecane and adamantane in acetonitrile solvent using the env...

283

One-dimensional channels constructed from per-hydroxylated pillar[6]arene molecules for gas and vapour adsorption.  

PubMed

Per-hydroxylated pillar[6]arene molecules formed highly ordered one-dimensional channels with a diameter of 6.7 Å. The channels can capture various gases, such as CO2, N2 and n-butane, and vapours of saturated hydrocarbons such as n-hexane and cyclohexane. PMID:25339195

Ogoshi, Tomoki; Sueto, Ryuta; Yoshikoshi, Kumiko; Yamagishi, Tada-Aki

2014-11-01

284

Molecular mechanism of hydrocarbons binding to the metal–organic framework  

SciTech Connect

The adsorption and diffusivity of methane, ethane, n-butane, n-hexane and cyclohexane in a metal organic framework (MOF) with the organic linker tetrakis[4-(carboxyphenyl)oxamethyl]methane, the metal salt, Zn2+, and organic pillar, 4,4’-bipyridin was studied using molecular dynamics simulations. For the n-alkanes, the longer the chain, the lower the free energy of adsorption, which was attributed to a greater number of contacts between the alkane and MOF. Cyclohexane had a slightly higher adsorption free energy than n-hexane. Furthermore, for cyclo- and n-hexane, there were no significant differences in adsorption free energies between systems with low to moderate loadings. The diffusivity of the n-alkanes was found to strongly depend on chain length with slower diffusion for longer chains. Cyclohexane had no effective diffusion, suggesting that the selectivity the MOF has towards n-hexane over cyclohexane is the result of kinetics instead of energetics. This work was supported by the U.S. Department of Energy's (DOE) Office of Basic Energy Sciences, Chemical Sciences program. The Pacific Northwest National Laboratory is operated by Battelle for DOE.

Sun, Xiuquan; Wick, Collin D.; Thallapally, Praveen K.; McGrail, B. Peter; Dang, Liem X.

2011-01-07

285

Surface Pressure, Hysteresis, Interfacial Tension, and CMC of Four Sorbitan Monoesters at Water-Air, Water-Hexane, and Hexane-Air Interfaces.  

PubMed

The purpose of this study was to investigate the interfacial properties of sorbitan monoesters (Span 20, 40, 60, and 80). The surface pressure was investigated at the water-air interface using a Langmuir-Blodgett apparatus. Interfacial tensions at n-hexane-air and water-n-hexane interfaces were measured by a du Nouy tensiometer. The effects of different surface-active agents and their concentrations on the interfacial properties of surfactant films were determined. With saturated sorbitan monoesters the lengthening of the hydrocarbon chain increases the collapse pressure and molecular area at the water-air interface. Unsaturated Span 80 had a lower collapse pressure and a larger molecular area than its saturated counterpart Span 60. Under compression-expansion cycles, all sorbitan monoesters showed hysteresis effects. At the n-hexane-air interface there were no differences in the interfacial tension between different sorbitan monoesters. At the water-n-hexane interface, differences in CMCs were small, but the surface excess of Span 80 was markedly smaller and the molecular area larger than the corresponding values of other sorbitan monoesters. Copyright 2000 Academic Press. PMID:10860587

Peltonen; Yliruusi

2000-07-01

286

Frying Stability of Moringa stenopetala Seed Oil  

Microsoft Academic Search

The frying performance of Moringa stenopetala seed oil (extracted with cold press or n-hexane) was studied especially as regards repeated frying operations. The oils were used for intermittent frying of potato slices and cod filets at a temperature of 175 C for 5 consecutive days (5 fryings per day). The chemical changes occurring in oils were evaluated. Free fatty acid content,

Stavros Lalas; Olga Gortzi; John Tsaknis

2006-01-01

287

In search for active non-precious metal catalyst for VOC combustion  

Microsoft Academic Search

The study is devoted to the evaluation of the cobalt and copper doped cobalt catalysts deposited on the structured carriers for VOC combustion. The catalysts have been tested in n-hexane oxidation in the jet-stirred gradientless reactor at various temperatures. As the reactor has occurred not to provide sufficient mixing conditions a model has been proposed which allowed to discriminate between

Joanna Lojewska; Andrzej Kolodziej; Ryszard Kapica; Arkadiusz Knapik; Jacek Tyczkowski

2009-01-01

288

RATE CONSTANTS FOR THE REACTION OF OH RADICALS WITH A SERIES OF ALKENES AND DIALKENES AT 295 + OR - 1 K  

EPA Science Inventory

Using a relative rate technique, rate constants for the gas phase reactions of the OH radical with n-butane, n-hexane and a series of alkenes and dialkenes, relative to that for propene, have been determined in one atmosphere of air at 295 + or - 1K. The resulting rate constant d...

289

Chemical composition, antimicrobial and antioxidant activities of Centaurea ensiformis Hub.Mor. (Asteraceae), a species endemic to Mugla (Turkey)  

Microsoft Academic Search

The n-hexane, chloroform, ethyl acetate and ethyl alcohol extracts of the aerial parts of Centaurea ensiformis, endemic to Turkey, have been assessed for antimicrobial and antioxidant activities. The chemical composition of the hexane extract of this plant was determined. The antimicrobial activities on microorganisms, including multiple antibiotic resistant bacteria, were evaluated using the disc diffusion method. The antioxidant activities were

Aysel Ugur; Mehmet Emin Duru; Ozgur Ceylan; Nurdan Sarac; Omer Varol; Ibrahim Kivrak

2009-01-01

290

Control of charcoal rot fungus Macrophomina phaseolina by extracts of Datura metel.  

PubMed

Methanolic leaf and fruit extracts of Datura metel were found highly effective in suppressing against Macrophomina phaseolina, the cause of charcoal rot disease. These extracts were further subjected to successive fractionation with n-hexane, chloroform, ethyl acetate and n-butanol. All the concentrations (3.125-200?mg?mL?¹) of chloroform, ethyl acetate and n-butanol fractions of leaf extract, and n-hexane fraction of fruit extract completely inhibited the target fungal growth. Two compounds A and B from the n-hexane fraction of fruit extract and compound C from n-butanol fraction of leaf extract were obtained by TLC. Compound B exhibited the best antifungal activity with an MIC value of 7.81?µg?mL?¹ that was at par with that of commercial fungicide mancozeb (80% w/w). This study concludes that M. phaseolina can be effectively controlled by natural antifungal compounds in n-hexane fraction of methanolic fruit extract of D. metel. PMID:22004473

Javaid, Arshad; Saddique, Amna

2012-01-01

291

Stability During Frying of Moringa oleifera Seed Oil Variety “Periyakulam 1”  

Microsoft Academic Search

The frying performance of the Moringa oleifera seed oil variety Periyakulam 1 (PKM 1) from India, extracted using cold press (CP) and n -hexane (H), during frying of potatoes and cod was studied especially as regards repeated frying operations. The oils were used for intermittent frying of potato slices and cod filets at a temperature of 175±5°C for 5 consecutive

John Tsaknis; Stavros Lalas

2002-01-01

292

Screening seeds of Scottish plants for antibacterial activity  

Microsoft Academic Search

Based on ethnopharmacological and taxonomic information, seeds of 21 Scottish plant species from 14 different families were obtained from authentic seed suppliers. Their n-hexane, dichloromethane and methanol extracts were assessed for antibacterial activity against 11 pathogenic bacterial species. Methanol extracts of 11 plant species showed significant antibacterial activity. Malva moschata and Prunus padus were active against five bacterial species, Reseda

Yashodharan Kumarasamy; Philip John Cox; Marcel Jaspars; Lutfun Nahar; Satyajit Dey Sarker

2002-01-01

293

Separation of hydrocarbon isomer vapors with silicalite zeolite membranes  

SciTech Connect

The permeation behavior of n-octane, isooctane, and n-hexane vapors through continuous, silicalite zeolite membranes on porous alumina supports was investigated between 383 and 523 K. For binary and ternary mixtures, n-octane permeated through the membrane faster than either n-hexane or isooctane, and a selectivity for n-octane over isooctane of 40 was obtained in a ternary mixture at 413 K. Selectivity was a function of temperature, however, and lower selectivities were obtained above and below 413 K. The n-octane/n-hexane selectivity was 9 at 413 K and decreased with increasing temperature. Permeances were a strong function of other organics present in the feed. The permeance of n-octane increased a factor of 16 in the presence of isooctane and n-hexane. The pure component permeances thus could not be used to predict separations for mixtures. Whereas N-octane was always the faster permeating compound in mixtures, pure isooctane permeated up to 5 times faster than pure n-octane, and pure n-hexane permeated faster than pure isooctane. That is, the largest molecule did not have the lowest permeance for pure components, and the smallest molecule did not have the highest permeance in mixtures. Thus relative permeances could not be predicted on the basis of size of shape alone. The permeances of the pure compounds were activated with activation energies between 18 and 45 kJ/mol. The mixed feed permeances also increased with temperature but did not follow an exponential relationship. Transport limitations caused by membrane saturation, diffusion through boundary layers on the feed side, and diffusion through the alumina support were not important.

Funke, H.H.; Kovalchick, M.G.; Falconer, J.L.; Noble, R.D. [Univ. of Colorado, Boulder, CO (United States). Dept. of Chemical Engineering] [Univ. of Colorado, Boulder, CO (United States). Dept. of Chemical Engineering

1996-05-01

294

Investigation of Molecular Exchange Using DEXSY with Ultra-High Pulsed Field Gradients  

SciTech Connect

Diffusion exchange spectroscopy has been employed for the investigation of water exchange between different regions of a cosmetic lotion as well as for the exchange of n-pentane between the inter- and intra-crystalline space in zeolite NaX. We successfully combined this two-dimensional (2D) NMR experiment with methods for the application of ultra-high pulsed field gradients of up to 35 T/m, resulting in observation times and mixing times as short as 2 ms and 2.8 ms, respectively.

Gratz, Marcel; Galvosas, Petrik [Faculty of Physics and Earth Sciences, University of Leipzig (Germany)

2008-12-05

295

Intermolecular stretching vibrations of H-complexes in solution at low temperatures  

SciTech Connect

The long-wave IR spectra were measured in the study in solutions of Xe and n-pentane in the region of the frequency of intramolecular stretching vibrations nu/sub sigma/ for a series of complexes with an H bond, previously investigated in the nu(AH) frequency region in solutions of liquid xenon and freons to determine whether the nu/sub sigma/ band is as sensitive to the type of solvent as nu(AH). The spectra of H complexes of perfluoro-tert-butanol (PFTB), trifluoroethanol, and HCl with dimethyl ether, HCl with acetonitrile, and stronger complexes of PFTB with di- and trimethylamines were recorded.

Iskanderov, T.A.; Kazaryan, S.G.; Kimel'fel'd, Ya.M.; Lokshin, B.V.; Smirnova, E.M.

1987-05-01

296

Comparative study of choleretic agents in anesthetized rats as well as in restrained and and unrestrained rats, with or without compensation for biliary loss  

NASA Technical Reports Server (NTRS)

Tests were conducted on Wistar rats by using 3 control choleretic agents: 1-phenyl-1-hydroxy n-pentane, dehydrocholic acid, and phenyl-dimethylacetic acid. The effects of these agents were compared in different experimental conditions. The comparative study of choleretic agents in anesthetized rats, in restrained and unrestrained rats, with or without compensation for biliary loss by the biliary secretion of restrained or unrestrained rats does not show, in systematic pharmecodynamic investigations, an obvious superiority over the methods based on the simple technique.

Labrid, C.; Dureng, G.; Tachon, J.; Duchene-Marullaz, P.

1980-01-01

297

Theoretical study of binding and permeation of ether-based polymers through interfaces.  

PubMed

We present a molecular dynamics simulation study on the interactions of poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO), and their ABA-type block copolymer, poloxamers, at water/n-heptane and 1,2-dimyristoyl-sn-glycero-3-phospatidycholine (DMPC) lipid bilayer/water interfaces. The partition coefficients in water/1-octanol of the linear polyethers up to three monomers were calculated. The partition coefficients evidenced a higher hydrophobicity of the PPO in comparison to PEO. At the water/n-heptane interface, the polymers tend to adopt elongated conformations in agreement with similar experimental ellipsometry studies of different poloxamers. In the case of the poloxamers at the n-heptane/water interface, the stronger preference of the PPO block for the hydrophobic phase resulted in bottle-brush-type polymer conformations. At lipid bilayer/water interface, the PEO polymers, as expected from their hydrophilic nature, are weakly adsorbed on the surface of the lipid bilayer and locate in the water phase close to the headgroups. The free energy barriers of permeation calculated for short polymer chains suggest a thermodynamics propensity for the water phase that increase with the chain length. The lower affinity of PEO for the hydrophobic interior of the lipid bilayer resulted in the spontaneous expulsion within the simulation time. On the contrary, PPO chains and poloxamers have a longer residence time inside the bilayer, and they tend to concentrate in the tail region of the bilayer near the polar headgroups. In addition, polymers with PPO unit length comparable to the thickness of the hydrophobic region of the bilayer tend to span across the bilayer. PMID:24219592

Samanta, Susruta; Hezaveh, Samira; Roccatano, Danilo

2013-11-27

298

Molecular dynamics simulation study of solvent effects on conformation and dynamics of polyethylene oxide and polypropylene oxide chains in water and in common organic solvents  

NASA Astrophysics Data System (ADS)

In this paper, the conformation and dynamics properties of polyethylene oxide (PEO) and polypropylene oxide (PPO) polymer chains at 298 K have been studied in the melt and at infinite dilution condition in water, methanol, chloroform, carbon tetrachloride, and n-heptane using molecular dynamics simulations. The calculated density of PEO melt with chain lengths of n = 2, 3, 4, 5 and, for PPO, n = 7 are in good agreement with the available experimental data. The conformational properties of PEO and PPO show an increasing gauche preference for the O-C-C-O dihedral in the following order water>methanol>chloroform>carbon tetrachloride = n-heptane. On the contrary, the preference for trans conformation has a maximum in carbon tetrachloride and n-heptane followed in the order by chloroform, methanol, and water. The PEO conformational preferences are in qualitative agreement with results of NMR studies. PEO chains formed different types of hydrogen bonds with polar solvent molecules. In particular, the occurrence of bifurcated hydrogen bonding in chloroform was also observed. Radii of gyration of PEO chains of length larger than n = 9 monomers showed a good agreement with light scattering data in water and in methanol. For the shorter chains the observed deviations are probably due to the enhanced hydrophobic effects caused by the terminal methyl groups. For PEO the fitting of end-to-end distance distributions with the semi-flexible chain model at 298 K provided persistence lengths of 0.375 and 0.387 nm in water and methanol, respectively. Finally, the radius of gyration of Pluronic P85 turned out to be 2.25 +/- 0.4 nm at 293 K in water in agreement with experimental data.

Hezaveh, Samira; Samanta, Susruta; Milano, Giuseppe; Roccatano, Danilo

2012-03-01

299

Autoignition of toluene reference fuels at high pressures modeled with detailed chemical kinetics  

SciTech Connect

A detailed chemical kinetic model for the autoignition of toluene reference fuels (TRF) is presented. The toluene submechanism added to the Lawrence Livermore Primary Reference Fuel (PRF) mechanism was developed using recent shock tube autoignition delay time data under conditions relevant to HCCI combustion. For two-component fuels the model was validated against recent high-pressure shock tube autoignition delay time data for a mixture consisting of 35% n-heptane and 65% toluene by liquid volume. Important features of the autoignition of the mixture proved to be cross-acceleration effects, where hydroperoxy radicals produced during n-heptane oxidation dramatically increased the oxidation rate of toluene compared to the case when toluene alone was oxidized. Rate constants for the reaction of benzyl and hydroperoxyl radicals previously used in the modeling of the oxidation of toluene alone were untenably high for modeling of the mixture. To model both systems it was found necessary to use a lower rate and introduce an additional branching route in the reaction between benzyl radicals and O{sub 2}. Good agreement between experiments and predictions was found when the model was validated against shock tube autoignition delay data for gasoline surrogate fuels consisting of mixtures of 63-69% isooctane, 14-20% toluene, and 17% n-heptane by liquid volume. Cross reactions such as hydrogen abstractions between toluene and alkyl and alkylperoxy radicals and between the PRF were introduced for completion of chemical description. They were only of small importance for modeling autoignition delays from shock tube experiments, even at low temperatures. A single-zone engine model was used to evaluate how well the validated mechanism could capture autoignition behavior of toluene reference fuels in a homogeneous charge compression ignition (HCCI) engine. The model could qualitatively predict the experiments, except in the case with boosted intake pressure, where the initial temperature had to be increased significantly in order to predict the point of autoignition. (author)

Andrae, J.C.G. [Department of Chemical Engineering and Technology, Royal Institute of Technology, SE-100 44 Stockholm (Sweden); Shell Global Solutions, P.O. Box 1, Chester CH1 3SH (United Kingdom); Bjoernbom, P. [Department of Chemical Engineering and Technology, Royal Institute of Technology, SE-100 44 Stockholm (Sweden); Cracknell, R.F.; Kalghatgi, G.T. [Shell Global Solutions, P.O. Box 1, Chester CH1 3SH (United Kingdom)

2007-04-15

300

A comprehensive detailed chemical kinetic reaction mechanism for combustion of n-alkane hydrocarbons from n-octane to n-hexadecane  

SciTech Connect

Detailed chemical kinetic reaction mechanisms have been developed to describe the pyrolysis and oxidation of nine n-alkanes larger than n-heptane, including n-octane (n-C{sub 8}H{sub 18}), n-nonane (n-C{sub 9}H{sub 20}), n-decane (n-C{sub 10}H{sub 22}), n-undecane (n-C{sub 11}H{sub 24}), n-dodecane (n-C{sub 12}H{sub 26}), n-tridecane (n-C{sub 13}H{sub 28}), n-tetradecane (n-C{sub 14}H{sub 30}), n-pentadecane (n-C{sub 15}H{sub 32}), and n-hexadecane (n-C{sub 16}H{sub 34}). These mechanisms include both high temperature and low temperature reaction pathways. The mechanisms are based on previous mechanisms for the primary reference fuels n-heptane and iso-octane, using the reaction classes first developed for n-heptane. Individual reaction class rules are as simple as possible in order to focus on the parallelism between all of the n-alkane fuels included in the mechanisms. These mechanisms are validated through extensive comparisons between computed and experimental data from a wide variety of different sources. In addition, numerical experiments are carried out to examine features of n-alkane combustion in which the detailed mechanisms can be used to compare reactivities of different n-alkane fuels. The mechanisms for these n-alkanes are presented as a single detailed mechanism, which can be edited to produce efficient mechanisms for any of the n-alkanes included, and the entire mechanism, with supporting thermochemical and transport data, together with an explanatory glossary explaining notations and structural details, is available for download from our web page. (author)

Westbrook, Charles K.; Pitz, William J.; Herbinet, Olivier; Silke, Emma J. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Curran, Henry J. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); University College of Ireland, Galway (Ireland)

2009-01-15

301

Low and intermediate temperature oxidation of ethanol and ethanol-PRF blends: An experimental and modeling study  

SciTech Connect

In this brief communication, we present new experimental species profile measurements for the low and intermediate temperature oxidation of ethanol under knock-prone conditions. These experiments show that ethanol exhibits no global low temperature reactivity at these conditions, although we note the heterogeneous decomposition of ethanol to ethylene and water. Similar behavior is reported for an E85 blend in n-heptane. Kinetic modeling results are presented to complement these experiments and elucidate the interaction of ethanol and primary reference fuels undergoing cooxidation. (author)

Haas, Francis M.; Chaos, Marcos; Dryer, Frederick L. [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544 (United States)

2009-12-15

302

Fluorescent spectra of chromatographic fractions of crude oils  

E-print Network

rb. t this particul:. ? exude al. o gave the l"rgest fr'. ction in this cut. Seyond 4600 Ao onl, y los intensities are observ?. d, "he second n-heptar? c, t, Figure 7? ~=. ble No. 9? di fera from the first cut, in th;:t, the fluore... Number 4 exhibits the j400 Ao peak. Again all Fig. 7 0 Fluorescent Spectra of n-heptane Fraction, Cut No. 2 ()) 0 fE 30 ( 3) / (lI I I I I (&) )/ I 000 travelength in Ao significant intensity ranges from 3400 A to 4600 A...

Dixon, William Samuel

2012-06-07

303

Effect of several uncouplers of cell-to-cell communication on gap junction morphology in mammalian heart  

Microsoft Academic Search

Summary  Electrical conduction in sheep Purkinje fibers has been blocked by three different procedures: (I) 1mm 2–4-dinitrophenol, (II) 3.5mm\\u000a n-Heptan-1-ol (heptanol), and (III) treatment by a hypotonic (120 mOsmoles) Ca2+-free solution for half an hour, followed by return to normal conditions. The gap junction morphology was analyzed quantitatively\\u000a in freezefracture replicas and compared in electrically conducting and nonconducting fibers. It is

J. Délèze; J. C. Hervé

1983-01-01

304

Superbenzene-porphyrin conjugates.  

PubMed

A free-base porphyrin carrying two hexabenzocoronene (HBC) substituents in a trans arrangement and its zinc complex have been prepared. The compounds were characterized extensively and found to form tricationic dimers in the gas phase. X-ray crystallography confirms for the zinc complex a profound ?-stacking of the HBC moieties. In contrast, the free-base porphyrin incarcerates n-heptane which essentially prevents ?-stacking. Upon excitation of the HBC substituents, efficient energy transfer to the central porphyrin is observed. PMID:25244699

Lungerich, Dominik; Hitzenberger, Jakob F; Marcia, Mario; Hampel, Frank; Drewello, Thomas; Jux, Norbert

2014-11-01

305

Premixed ignition behavior of alternative diesel fuel-relevant compounds in a motored engine experiment  

SciTech Connect

A motored engine study using premixed charges of fuel and air at a wide range of diesel-relevant equivalence ratios was performed to investigate autoignition differences among surrogates for conventional diesel fuel, gas-to-liquid (GTL) diesel fuel, and biodiesel, as well as n-heptane. Experiments were performed by delivering a premixed charge of vaporized fuel and air and increasing the compression ratio in a stepwise manner to increase the extent of reaction while monitoring the exhaust composition via Fourier transform infrared (FTIR) spectrometry and collecting condensable exhaust gas for subsequent gas chromatography/mass spectrometry (GC/MS) analysis. Each fuel demonstrated a two-stage ignition process, with a low-temperature heat release (LTHR) event followed by the main combustion, or high-temperature heat release (HTHR). Among the three diesel-relevant fuels, the magnitude of LTHR was highest for GTL diesel, followed by methyl decanoate, and conventional diesel fuel last. FTIR analysis of the exhaust for n-heptane, the conventional diesel surrogate, and the GTL diesel surrogate revealed that LTHR produces high concentrations of aldehydes and CO while producing only negligible amounts of CO{sub 2}. Methyl decanoate differed from the other two-stage ignition fuels only in that there were significant amounts of CO{sub 2} produced during LTHR; this was the result of decarboxylation of the ester group, not the result of oxidation. GC/MS analysis of LTHR exhaust condensate for n-heptane revealed high concentrations of 2,5-heptanedione, a di-ketone that can be closely tied to species in existing autoignition models for n-heptane. GC/MS analysis of the LTHR condensate for conventional diesel fuel and GTL diesel fuel revealed a series of high molecular weight aldehydes and ketones, which were expected, as well as a series of organic acids, which are not commonly reported as products of combustion. The GC/MS analysis of the methyl decanoate exhaust condensate revealed that the aliphatic chain acts similarly to n-paraffins during LTHR, while the ester group remains intact. Thus, although the FTIR data revealed that decarboxylation occurs at significant levels for methyl decanoate, it was concluded that this occurs after the aliphatic chain has been largely consumed by other LTHR reactions. (author)

Szybist, James P.; Boehman, Andre L.; Haworth, Daniel C. [Pennsylvania State University, Fuel Science Program, 405 Academic Activities Building, University Park, PA 16802 (United States); Koga, Hibiki [Honda R and D Company, Ltd., Asaka-shi, Saitama 351-0024 (Japan)

2007-04-15

306

Identification of geochemical polycyclic aromatic hydrocarbons from terpenes by high-resolution Shpol'skii effect fluorescence spectrometry  

SciTech Connect

High-resolution spectrofluorimetry (HFR) at 4.2/sup 0/K in n-alkane matrices is reported as a method for the identification of polycyclic aromatic hydrocarbons (PAH) derived from triterpene, which occurs in the orgainic matter of marine and terrestrial sediments. The marine sediments studied were cored from the Sea of Oman at water depths varying between 200 and 4000 m in an area where the organic matter is mainly of authochthonous origin. The series of chrysene derivatives were extracted from the total aromatic fraction by high performance liquid chromatography on ..mu..-silica-NH/sub 2/ stationary phase with n-heptane as an elutant.

Ewald, M.; Moinet, A.; Saliot, A.; Albrecht, P.

1983-01-01

307

Molecular interactions in alcohol-ethyl methacrylate mixtures  

NASA Astrophysics Data System (ADS)

Molecular interaction between alcohols (1-propanol, 1-butanol, s-butanol, t-butanol, 1-pentanol, 1-heptanol, 1-octanol and 1-decanol) with ethyl methacrylate has been studied in n-heptane, CCl 4 and benzene at 298 K using FTIR spectroscopic and dielectric methods. The result obtained from both the methods indicates only the existence of most likely 1:1 complex formation between the alcohol and ethyl methacrylate in these systems. The alkyl chain length of alcohol and the solvent used play a significant role in the strength of hydrogen bond (O sbnd H:O dbnd C) determined on the basis of spectral and dielectric parameters.

Dharmalingam, K.; Ramachandran, K.; Sivagurunathan, P.; Kalamse, G. M.

2008-02-01

308

Frequency response of a vaporization process to distorted acoustic disturbances  

NASA Technical Reports Server (NTRS)

The open-loop response properties expressed as the mass vaporized in phase and out of phase with the pressure oscillations were numerically evaluated for a vaporizing n-heptane droplet. The evaluation includes the frequency dependence introduced by periodic oscillation in droplet mass and temperature. A given response was achieved over a much broader range of frequency with harmonically distorted disturbances than with sinusoidal disturbances. The results infer that distortion increases the probability of incurring spontaneous and triggered instability in any rocket engine combustor by broadening the frequency range over which the vaporization process can support an instability.

Heidmann, M. F.

1972-01-01

309

Hydrogenation of Aromatics with [Ru( ? 5 -C 5 H 5 )Cl(TPPDS) 2 ] in Biphasic Medium  

Microsoft Academic Search

[Ru(?5-C5H5)Cl(TPPDS)2], [TPPDS=P(C6H5)(C6H4SO3?)2] in biphasic (n-heptane\\/water) medium hydrogenates toluene, benzene and m-xylene (105 C, 1400 psig H2, substrate\\/catalyst=600:1, 4 h) and in toluene hydrogenation gives methylcyclohexane. Catalytic activity increases with temperature,\\u000a H2 pressure, ionic strength, and pH lower than 10. The catalytic water solution can be reused several times with little activity\\u000a loss.

Trino Suárez; Angie Guzmán; Bernardo Fontal; Marisela Reyes; Fernando Bellandi; Ricardo R. Contreras; Pedro Cancines; Gustavo León; Loguard Rojas

2006-01-01

310

Kinetic modelling of a surrogate diesel fuel applied to 3D auto-ignition in HCCI engines  

E-print Network

The prediction of auto-ignition delay times in HCCI engines has risen interest on detailed chemical models. This paper described a validated kinetic mechanism for the oxidation of a model Diesel fuel (n-decane and ?-methylnaphthalene). The 3D model for the description of low and high temperature auto-ignition in engines is presented. The behavior of the model fuel is compared with that of n-heptane. Simulations show that the 3D model coupled with the kinetic mechanism can reproduce experimental HCCI and Diesel engine results and that the correct modeling of auto-ignition in the cool flame region is essential in HCCI conditions.

Bounaceur, Roda; Fournet, René; Battin-Leclerc, Frédérique; Jay, S; Da Cruz, A Pires

2007-01-01

311

Testing of high-octane fuels in the single-cylinder airplane engine  

NASA Technical Reports Server (NTRS)

One of the most important properties of aviation fuels for spark-ignition engines is their knock rating. The CFR engine tests of fuels of 87 octane and above does not always correspond entirely to the actual behavior of these fuels in the airplane engine. A method is therefore developed which, in contrast to the octane number determination, permits a testing of the fuel under various temperatures and fuel mixture conditions. The following reference fuels were employed: 1) Primary fuels; isooctane and n-heptane; 2) Secondary fuels; pure benzene and synthetic benzine.

Seeber, Fritz

1940-01-01

312

Analysis of aromatic constituents in multicomponent hydrocarbon mixtures by infrared spectroscopy using multiple linear regression  

NASA Astrophysics Data System (ADS)

Absorption spectra of multicomponent hydrocarbon mixtures based on n-heptane and isooctane with addition of benzene (up to 1%) and toluene and o-xylene (up to 20%) were investigated experimentally in the region of the first overtones of the hydrocarbon groups (? = 1620-1780 nm). It was shown that their concentrations could be determined separately by using a multiple linear regression method. The optimum result was obtained by including four wavelengths at 1671, 1680, 1685, and 1695 nm, which took into account absorption of CH groups in benzene, toluene, and o-xylene and CH3 groups, respectively.

Vesnin, V. L.; Muradov, V. G.

2012-09-01

313

Velocity profiles in laminar diffusion flames  

NASA Technical Reports Server (NTRS)

Velocity profiles in vertical laminar diffusion flames were measured by using laser Doppler velocimetry (LDV). Four fuels were used: n-heptane, iso-octane, cyclohexane, and ethyl alcohol. The velocity profiles were similar for all the fuels, although there were some differences in the peak velocities. The data compared favorably with the theoretical velocity predictions. The differences could be attributed to errors in experimental positioning and in the prediction of temperature profiles. Error in the predicted temperature profiles are probably due to the difficulty in predicting the radiative heat losses from the flame.

Lyons, Valerie J.; Margle, Janice M.

1986-01-01

314

Chemical kinetic mechanism for the oxidation of paraffinic hydrocarbons needed for primary reference fuels  

SciTech Connect

A detailed chemical kinetic reaction mechanism is described which simulates the oxidation of the primary reference fuels n-heptane and iso-octane. The high temperature subset of these mechanisms is identified, and the extensions to deal with low temperature conditions are also explained. The algorithms used to assign reaction rates to elementary steps in the reaction mechanism are described, and the means of identifying the different chemical species and the relevant reactions are outlined. Finally, we show how interested kinetic modeling researchers can obtain copies of this reaction mechanism.

Westbrook, C.K.; Pitz, W.J.

1993-03-01

315

The upgrading of Fischer-Tropsch liquids over ZSM-5 using model compounds  

E-print Network

the Department of Energy, Pittsburgh Energy Technology Center for their financial support and advice. I would also like to thank Eugene Flipse for his cesigning ana manufacture of certain electronic components, and Dr. C. V. Philip for his expertise extended... and 3 hr-1 63 67 68 69 22. 23. 24. 26. 27. 28. 30. 31. Product Distribution of F-T liquid over Hi-ZSM-5 at WHSV of 1 ana 3 hr-1 Effect of Space Velocity on Proauct Distribution of n-heptane over Zn-ZSN-5 Effect df Pressure on Conversion...

Smith, David Duane

2012-06-07

316

Homogeneous catalysts supported on soluble polymers: biphasic Sonogashira coupling of aryl halides and acetylenes using MeOPEG-bound phosphine-palladium catalysts for efficient catalyst recycling.  

PubMed

The Sonogashira coupling of various aryl bromides and iodides with different acetylenes was studied under biphasic conditions with soluble, polymer-modified catalysts to allow the efficient recycling of the homogeneous catalyst. For this purpose, several sterically demanding and electron-rich phosphines of the type R(P)PR(2) were synthesised. They are covalently linked to a monomethyl polyethylene glycol ether with a mass of 2000 Dalton (R(P)=MeOPEG(2000)) R(P)PR(2): -PR(2)= -CH(2)C(6)H(4)CH(2)P(1-Ad)(2), -C(6)H(4)-P(1-Ad)(2), -C(6)H(4)-PPh(2). To couple aryl iodides and acetylenes, the catalyst [(MeCN)(2)PdCl(2)]/2 R(P)-C(6)H(4)-PPh(2) was used in CH(3)CN/Et(3)N/n-heptane (5/2/5). The combined yields of coupling product over five reaction cycles are between 80-95 percent. There is no apparent leaching of the catalyst into n-heptane, as evidenced by (1)H NMR spectroscopy. The new catalyst [(MeCN)(2)PdCl(2)]/2 (1-Ad)(2)PBn can be used for room-temperature coupling of various aryl bromides and acetylenes in THF with HNiPr(2) as a base. A closely related catalyst Na(2)[PdCl(4)]/2 R(P)-CH(2)C(6)H(4)CH(2)P(1-Ad)(2) linked to the polymer was used to couple aryl bromides and acetylenes in DMSO or DMSO/n-heptane at 60 degrees C with 0.5 mol percent Na(2)[PdCl(4)], 1 mol percent R(P)PR(2) and 0.33 mol percent CuI. The combined yield of coupling products over five cycles is always greater than 90 percent, except for sterically hindered aryl bromides. The determination of the turnover frequency (TOF) of the catalyst indicates only a small decrease in activity over five cycles. Leaching of the catalyst into the product containing n-heptane solution could not be detected by means of (1)H NMR and TXRF; this is indicative of >99.995 percent catalyst retention in the DMSO solvent. PMID:12645031

Köllhofer, Axel; Plenio, Herbert

2003-03-17

317

Long Duration Exposure Facility (LDEF) low-temperature Heat Pipe Experiment Package (HEPP)  

NASA Technical Reports Server (NTRS)

The flight test results are discussed obtained with the Heat Pipe Experiment Package (HEPP). The HEPP was designed to demonstrate the performance of an ethane constant conductance heat pipe (CCHP) and an ethane heat pipe diode in microgravity. These heat pipes have a nominal operating temperature range of 140 to 250 K. Also, included in the HEPP is a Phase Change Material (PCM) canister which provides temperature stability through melting and freezing of the n-heptane PCM. A comparison of pre-flight, flight, and post-flight thermal performance is also presented.

Mcintosh, Roy; Brennan, Patrick J.

1991-01-01

318

The preparation and characterization of Li 4Ti 5O 12\\/carbon nano-tubes for lithium ion battery  

Microsoft Academic Search

Li4Ti5O12\\/carbon nano-tubes (CNTs) composite was prepared by sol–gel method while Ti(OC4H9)4, LiCH3COO·2H2O and the n-heptane containing CNTs were used as raw materials. The characters of Li4Ti5O12\\/CNTs composite were determined by XRD, SEM, and TG methods. Its electrochemical properties were measured by charge–discharge cycling and impedance tests. It was found that the prepared Li4Ti5O12\\/CNTs presented an excellent rate capability and capacity

Junjie Huang; Zhiyu Jiang

2008-01-01

319

Hydrocarbon fuel cooling technologies for advanced propulsion  

SciTech Connect

Storable hydrocarbon fuels that undergo endothermic reaction provide an attractive heat sink for future high-speed aircraft. An investigation was conducted to explore the endothermic potential of practical fuels, with inexpensive and readily available catalysts, under operating conditions simulative of high-speed flight applications. High heat sink capacities and desirable reaction products have been demonstrated for n-heptane and Norpar 12 fuels using zeolite catalysts in coated tube reactor configurations. The effects of fuel composition and operating condition on extent of fuel conversion, product composition, and the corresponding endotherm have been examined. The results obtained in this study provide a basis for catalytic-reactor/heat-exchanger design and analysis.

Sobel, D.R.; Spadaccini, L.J. [United Technologies Research Center, East Hartford, CT (United States)

1997-04-01

320

Preliminary antioxidant profile of Pistacia integerrima Stewart.  

PubMed

To explore the free radical scavenging properties of crude ethanolic extract of galls, bark, leaves, roots of Pistacia integerrima and its subsequent solvent fractions viz., n-hexane, chloroform, ethyl acetate and methanol against 1, 1-diphenyl-2-picrylhydrazyl (DPPH) stable. In vitro DPPH based free radical was employed using querceitin as standard antioxidant while methanol as negative control. Different parts of P. integerrima showed marked scavenging on DPPH in a concentration dependent manner. The ethanolic extract exhibited 60.51 88.51% scavenging effect on DPPH which differentiated upon fractionation. of the part used, leaves of the plant were the least effective while n-hexane was the least dominant fraction. However, the rest of the parts and fractions demonstrated profound scavenging potential. This in-vitro study revealed an outstanding free radical scavenging potential of various solvent fractions of different parts of whole plant P. integerrima. PMID:25015451

Rauf, Abdur; Uddin, Ghias; Khan, Haroon; Roohullah

2014-07-01

321

Antimalarial activity of Artemisia annua flavonoids from whole plants and cell cultures.  

PubMed

Cell suspension cultures developed from Artemisia annua exhibited antimalarial activity against Plasmodium faldparum in vitro both in the n-hexane extract of the plant cell culture medium and in the chloroform extract of the cells. Trace amounts of the antimalarial sesquiterpene lactone artemisinin may account for the activity of the n-hexane fraction but only the methoxylated flavonoids artemetin, chrysoplenetin, chrysosplenol-D and cirsilineol can account for the activity of the chloroform extract. These purified flavonoids were found to have IC50 values at 2.4 - 6.5 × 10(-5)M against P. falciparum in vitro compared with an IC50 value of about 3 × 10(-8)M for purified artimisinin. At concentrations of 5 × 10(-6)M these flavonoids were not active against P. falciparum but did have a marked and selective potentiating effect on the antiplasmodial activity of artemisinin. PMID:24213368

Liu, K C; Yang, S L; Roberts, M F; Elford, B C; Phillipson, J D

1992-11-01

322

Cobalt and nickel supported on HY zeolite: Synthesis, characterization and catalytic properties  

SciTech Connect

Bifunctional catalysts consisting of cobalt and nickel supported on HY zeolite were synthesized by solvent excess impregnation and characterized by X-ray diffraction, Fourier-transformed infrared spectroscopy, scanning electron microscopy, atomic absorption spectroscopy, thermogravimetric analysis and nitrogen adsorption. The profiles of metal reduction on zeolite were obtained by temperature-programmed reduction. The catalytic properties of the bifunctional catalysts were verified by n-hexane hydroconversion. X-ray diffraction and microstructural analyses showed the presence of crystalline phases in HY zeolite and in samples after impregnation. A decrease in the micropore surface area was observed by nitrogen adsorption experiments and attributed to a reduction in the accessibility to micropores. The catalysts showed catalytic activity in the hydroconversion of n-hexane with selectivity to branched hydrocarbons. Such catalytic activity was related to the acid and metallic properties of the bifunctional catalysts used.

Garrido Pedrosa, Anne M. [Federal University of Rio Grande do Norte, Department of Chemistry, CP 1692, 59078-970 Natal-RN (Brazil)]. E-mail: annemgp@yahoo.com; Souza, Marcelo J.B. [Federal University of Sergipe, Department of Chemical Engineering, 49100-000 Sao Cristovao-SE (Brazil); Melo, Dulce M.A. [Federal University of Rio Grande do Norte, Department of Chemistry, CP 1692, 59078-970 Natal-RN (Brazil); Araujo, Antonio S. [Federal University of Rio Grande do Norte, Department of Chemistry, CP 1692, 59078-970 Natal-RN (Brazil)

2006-06-15

323

Phenomenological model of fungal biofilters for the abatement of hydrophobic VOCs.  

PubMed

This work describes the growth of filamentous fungi in biofilters for the degradation of hydrophobic VOCs. The study system was n-hexane and Fusarium solani B1. The system is mathematically described and the main physical, kinetic data and morphological parameters were obtained by independent experiments and validated with data from laboratory experiments. The model describes the increase in the transport area by the growth of the filamentous cylindrical mycelia and its relation with n-hexane elimination in quasi-stationary state in a biofilter. The model describing fungal growth includes Monod-Haldane kinetic and hyphal elongation and ramification. A specific surface area of transport (SSAT) of 1.91 x 10(5) m(2) m(-3) and a maximum elimination capacity (EC) of 248 g m(-3) h(-1) were obtained by the mathematical model simulation, with a 10% of error with respect to the experimental EC. PMID:18781682

Vergara-Fernández, Alberto; Hernández, Sergio; Revah, Sergio

2008-12-15

324

[High performance preparation and structural confirmation of lignans from Schisandrae chinensis fructus by using HSCCC combined with ESI-MSn method].  

PubMed

High-speed counter-current chromatography (HSCCC) was used to high performance separate and prepare lignans from Schisandrae chinensis fructus. The solvent system is composed of n-hexane-ethyl acetate-methanol-water (9 : 1 : 5 : 5) and n-hexane-ethyl acetate-methanol-water (9 : 1 : 9 : 5), speed is at 900 r.min-1, and flow rate is at 2.0 mL.min-1. Five fractions from Schisandrae chinensis fructus extract were separated and prepared with one HSCCC process. They were identified as schisandrin, gomisin J, schisandrol B, schisantherin A and deoxyschizandrin by electrospray ionization-multiple tandem mass spectrometry (ESI-MSn), respectively. Their contents were obtained in 98.74%, 94.32%, 99.53%, 94.23% and 98.68% by ultra high performance liquid chromatography (UPLC), separately. The rapid and simple method can be applied for the preparation of lignans from Schisandrae chinensis fructus. PMID:24783510

Yu, Xiao-Li; Pi, Zi-feng; Hu, Xiu-Li; Song, Feng-Rui; Liu, Zhi-Qiang

2014-01-01

325

Neurotoxic metabolites of ''commercial hexane'' in the urine of shoe factory workers  

SciTech Connect

Urinary metabolites were tested in 41 shoe-factory workers exposed to a mixture of 10 solvents among which ''commercial hexane'' was the prevailing component. Cyclohexanol, 2-methyl-2-pentanol, 3-methyl-2-pentanol, and trichloroethanol were determined in connection with exposure to cyclohexane, 2-methylpentane, 3-methylpentane, and trichloroethylene, respectively. 2-Hexanol, 2,5-hexanedione, 2,5-dimethylfuran, and gamma-valerolactone were all determined in connection with n-hexane exposure only. 2,5-Hexanedione was the principal n-hexane metabolite found in the workers' urine. This finding of the experimentally proven neurotoxin 2,5-hexanedione in the urine of shoe-factory workers exposed to ''commercial hexane'' is consistent with the idea that this compound is responsible for the development of neuropathy in this group of individuals.

Perbellini, L.; Brugnone, F.; Gaffuri, E.

1981-12-01

326

Pressurized liquid extraction of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and coplanar polychlorinated biphenyls from contaminated soil.  

PubMed

Extraction solvents for pressurized liquid extraction (PLE) used to extract polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans (PCDD/PCDFs), and coplanar polychlorinated biphenyls (Co-PCBs) from contaminated soil were investigated. The PCDD/PCDFs and Co-PCBs in Certified Reference Material: CRM 0422 (Forest soil) were extracted using toluene, n-hexane, acetone, acetone/toluene and acetone/n-hexane (1:1, v/v). Soxhlet extraction was the reference method. Results demonstrated that PLE using mixed solvents produced better analyte recoveries than the single solvents. However, these results were lower than those for Soxhlet extraction. Additional extraction cycles using mixed solvents achieved better recovery results. Mixed solvents and several extraction cycles were necessary for satisfactory extraction of more tightly bound PCDD/PCDFs and Co-PCBs from soil. PMID:16457831

Kiguchi, Osamu; Kobayashi, Takashi; Saitoh, Katsumi; Ogawa, Nobuaki

2006-03-10

327

Solvent effect on the size of platinum nanoparticle synthesized in microemulsion systems  

NASA Astrophysics Data System (ADS)

In this research work, the effect of solvent on the size of paltinum nanoparticles synthesized by microemulsion method was investigated. Platinum nanoparticles have been prepared by the reduction of H2PtCl6 with hydrazine in water-in-oil (w/o) microemulsions consisting of sodium bis(2-ethylhexyl) sulfo-succinate (AOT) and solvents n-hexane, cyclohexane and n-nonane. The size of the platinum nanoparticles was measured using transmission electron microscopy (TEM). It was verified that, for reduction of H2PtCl6 by hydrazine in microemulsion with different organic solvents, the solvents are arranged by their influence on nanoparticle sizes as follows: n-nonane > cyclohexane > n-hexane.

Salabat, Alireza; Far, Mina Rahmati

2012-05-01

328

Grafting of polyethylene by ?-radiation grafting onto conductive carbon black and application as novel gas and solute sensors  

NASA Astrophysics Data System (ADS)

?-Ray radiation grafting of polyethylene (PE) onto conductive carbon black under various conditions was investigated. In the case of 400 kGy dose of irradiation of PE-adsorbed carbon black at high temperatures near or above the melting point of PE, the grafting of PE onto the carbon black surface was successfully proceeded and the percentage of grafting exceeded 90%. Using the PE-grafted carbon black and PE, conductive composite prepared from PE-grafted carbon black and PE was prepared. The electric resistance of the composite largely increased when it was transferred from dry air to solvent vapor, such as carbon tetrachloride and cyclohexane. The electric resistance also clearly increased when the composite was immersed in n-hexane solution of tetrahydrofuran, chloroform and cyclohexane. Therefore, it was concluded that the conductive composite could be used as a novel sensor of solvent vapor and solute in n-hexane.

Chen, J.; Iwata, H.; Maekawa, Y.; Yoshida, M.; Tsubokawa, N.

2003-06-01

329

Biological activity of Spatoglossum asperum: a brown alga.  

PubMed

Chloroform and methanol fractions of an ethanol extract of Spatoglossum asperum showed antifungal activity against the highly destructive plant pathogen, Macrophomina phaseolina while the n-hexane fraction showed activity against Rhizoctonia solani and Fusarium solani. n-Hexane and methanol fractions also showed nematicidal activity against the plant parasitic nematode, Meloidogyne javanica. Column chromatography of the ethanol extract of seaweed yielded oily fractions named SA-I to SA-VI. GC-MS data of these oily fractions showed the presence of various fatty acid esters. Some of these oily fractions exhibited strong antifungal and nematicidal activities. Oily fractions of S. asperum also showed hypolipidaemic activity in normal, triton-induced and high fat diet-induced hyperlipidaemic rats without producing any ill effect on cardiac and liver enzymes. PMID:16161033

Ara, Jehan; Sultana, Viqar; Qasim, Rashida; Ehteshamul-Haque, Syed; Ahmad, Viqar Uddin

2005-07-01

330

Investigations of adsorbed organic molecules in Na-Y zeolite by xenon-129 NMR  

SciTech Connect

The adsorption of n-hexane, benzene, and trimethylbenzene in Na-Y zeolite supercages has been investigated by use of xenon-129 NMR. As shown by Fraissard and co-workers, xenon-129 is an excellent probe of its environment in zeolites and is sensitive to the number of adsorbed guest molecules. The xenon-129 chemical shift, when extrapolated to zero effective xenon pressure, is 89.7 {plus minus} 0.1 ppm for benzene, 89.0 {plus minus} 1.3 ppm for trimethylbenzene, and 107.7 {plus minus} 1.2 ppm for n-hexane at a concentration of two guest molecules per zeolite supercage compared to 58.9 {plus minus} 0.5 ppm for empty Na-Y zeolite supercages. This approach is useful for determining the number of adsorbed molecules inside zeolite supercages and given information about their arrangement within the supercages.

de Menorval, L.C.; Raftery, D.; Liu, S.B.; Takegoshi, K.; Ryoo, R.; Pines, A. (Lawrence Berkeley Lab., CA (USA))

1990-01-11

331

Preliminary characterization of anhydrous ethanol used in Brazil as automotive fuel.  

PubMed

This work reports preliminary studies on the characterisation of anhydrous ethanol (AEA) used as an automotive fuel mixed with gasoline in Porto Alegre (South Brazil). Pre-concentration of the impurities contained in 1000 ml of AEA was carried on through solid-phase extraction using XAD4 resin. The main compounds in the extract were identified by means of spectral data from the library of the equipment. The concentrate was then fractionated using a preparative liquid chromatographic column filled with activated silica gel and the elution procedure was carried out with, n-hexane, n-hexane-benzene (1:1, v/v) and dichloromethane. Prior to analysis by GC-MS, each fraction was reduced to 1 ml with a gentle stream of nitrogen. Saturated linear hydrocarbons and aromatic hydrocarbons eluted in the first fraction and oxygenated compounds such as aldehydes. ketones and alcohols, eluted in the second one. were the main compounds detected in the sample. PMID:12580505

Vilar, Rossana B C; da Silva, Rosângela; Schossler, Patricia; Cataluña Veses, Renato; Piatnicki, Clarisse; Samios, Dimitrios; Caramão, Elina B

2003-01-24

332

Evaluation of a locally homogeneous flow model of spray combustion  

NASA Technical Reports Server (NTRS)

A model of spray combustion which employs a second-order turbulence model was developed. The assumption of locally homogeneous flow is made, implying infinitely fast transport rates between the phase. Measurements to test the model were completed for a gaseous n-propane flame and an air atomized n-pentane spray flame, burning in stagnant air at atmospheric pressure. Profiles of mean velocity and temperature, as well as velocity fluctuations and Reynolds stress, were measured in the flames. The predictions for the gas flame were in excellent agreement with the measurements. The predictions for the spray were qualitatively correct, but effects of finite rate interphase transport were evident, resulting in a overstimation of the rate development of the flow. Predictions of spray penetration length at high pressures, including supercritical combustion conditions, were also completed for comparison with earlier measurements. Test conditions involved a pressure atomized n-pentane spray, burning in stagnant air at pressures of 3, 5, and 9 MPa. The comparison between predictions and measurements was fair. This is not a very sensitive test of the model, however, and further high pressure experimental and theoretical results are needed before a satisfactory assessment of the locally homogeneous flow approximation can be made.

Mao, C. P.; Szekely, G. A., Jr.; Faeth, G. M.

1980-01-01

333

Seasonal behavior of non-methane hydrocarbons in the firn air at Summit, Greenland  

NASA Astrophysics Data System (ADS)

Non-methane hydrocarbons (NMHC) were measured in the ambient air and in the snowpack interstitial firn air at ?1 m depth continuously for nearly two years at Summit, Greenland, from fall 2008 through summer 2010. Additionally, five firn air depth profiles were conducted to a depth of 3 m spanning winter, spring, and summer seasons. Here we report measurements of ethane, ethene, ethyne, propane, propene, i-butane, n-butane, i-pentane, n-pentane, and benzene and discuss the seasonal behavior of these species in the ambient and firn air. The alkanes, ethyne, and benzene in the firn air closely reflect the ambient air concentrations during all the seasons of the year. In spring and summer seasons, ethene and propene were enhanced in the near-surface firn over that in the ambient air, indicating a photochemical production mechanism for these species within the snowpack interstitial air. Evaluation of the NMHC ratios of i-butane/n-butane, i-pentane/n-pentane, and benzene/ethyne in both ambient and firn air does not provide evidence for chlorine or bromine radical chemistry significantly affecting these gases, except in a few summer samples, where individual data points may suggest bromine oxidation influence.

Helmig, D.; Stephens, C. R.; Caramore, J.; Hueber, J.

2014-03-01

334

Coupled-cluster, Möller Plesset (MP2), Density Fitted Local MP2, and Density Functional Theory Examination of the Energetic and Structural Features of Hydrophobic Solvation: Water and Pentane  

SciTech Connect

The interaction potentials between immiscible polar and non-polar solvents are a major driving force behind the formation of liquid:liquid interfaces. In this work, the interaction energy of water–pentane dimer has been determined using coupled-cluster theory with single double (triple) excitations [CCSD(T)], 2nd order Möller Plesset perturbation theory (MP2), density fitted local MP2 (DF-LMP2), as well as density functional theory using a wide variety of density functionals and several different basis sets. The M05-2X exchange correlation functionals exhibit excellent agreement with CCSD(T) and DF-LMP2 after taking into account basis set superposition error. The gas phase water–pentane interaction energy is found to be quite sensitive to the specific pentane isomer (2,2- dimethylpropane vs. n-pentane) and relative orientation of the monomeric constituents. Subsequent solution phase cluster calculations of 2,2-dimethylpropane and n-pentane solvated by water indicate a positive free energy of solvation that is in good agreement with available experimental data. Structural parameters are quite sensitive to the density functional employed and reflect differences in the two-body interaction energy calculated by each method. In contrast, cluster calculations of pentane solvation of H2O solute are found to be inadequate for describing the organic solvent, likely due to limitations associated with the functionals employed (B3LYP, BHandH, and M05-2X).

Ghadar, Yasaman; Clark, Aurora E.

2012-02-02

335

On sub-T(g) dewetting of nanoconfined liquids and autophobic dewetting of crystallites.  

PubMed

The glass transition temperature (T(g)) of thin films is reduced by nanoconfinement, but it is also influenced by the free surface and substrate interface. To gain more insights into their contributions, dewetting behaviors of n-pentane, 3-methylpentane, and toluene films are investigated on various substrates as functions of temperature and film thickness. It is found that monolayers of these molecules exhibit sub-T(g) dewetting on a perfluoro-alkyl modified Ni substrate, which is attributable to the evolution of a 2D liquid. The onset temperature of dewetting increases with film thickness because fluidity evolves via cooperative motion of many molecules; sub-T(g) dewetting is observed for films thinner than 5 monolayers. In contrast, monolayers wet substrates of graphite, silicon, and amorphous solid water until crystallization occurs. The crystallites exhibit autophobic dewetting on the substrate covered with a wetting monolayer. The presence of premelting layers is inferred from the fact that n-pentane crystallites disappear on amorphous solid water via intermixing. Thus, the properties of quasiliquid formed on the crystallite surface differ significantly from those of the 2D liquid formed before crystallization. PMID:22337324

Souda, Ryutaro

2012-03-28

336

Separation and Simultaneous Determination of Enantiomers of Tau-fluvalinate and Permethrin in Drinking Water  

Microsoft Academic Search

The chiral liquid chromatographic separation of two pyrethroid insecticides, tau-fluvalinate and permethrin, on different polysaccharide-based chiral stationary phases (CSPs) has been investigated. Complete separation of these compounds was achieved with Chiralcel OJ under normal phase mode and a mobile phase of n-hexane:ethanol (90:10, v\\/v). This method has been used for determining these compounds in drinking water at ppb levels after

Guo-Sheng Yang; P. Parrilla Vázquez; A. Garrido Frenich; J. L. Martínez Vidal; H. Y. Aboul-Enein

2004-01-01

337

Simple solid-phase extraction method for determination of polychlorinated biphenyls and selected organochlorine pesticides in human serum  

Microsoft Academic Search

A simple off-line solid-phase extraction (SPE) method for isolation of polychlorinated biphenyls (PCBs) and selected organochlorine pesticides (OCPs) from human serum has been developed. The procedure includes denaturation of serum proteins by a mixture of water–1-propanol, application of the sample by aspiration twice repeatedly through the SPE column and elution with a mixture of n-hexane–dichlormethane. After final clean-up the compounds

K. ?onka; B. Drobná; A. Ko?an; J. Petrík

2005-01-01

338

Comparative bioactivity studies on two Mimosa species (Estudios comparativos de dos especies de Mimosa)  

Microsoft Academic Search

Comparative antioxidant, antibacterial activities and general toxicity studies on the n-hexane, dichloromethane (DCM) and methanol (MeOH) extracts of Mimosa pudica and Mimosa rubicaulis, two Bangladeshi medicinal plants, were carried out, using the 2,2-diphenyl- 1-picryl-hydrazyl (DPPH) assay, the resazurin microtitre plate based assay, and the brine shrimp lethality assay, respectively. The DCM and MeOH extracts of both M. pudica and M.

Samuel GENEST; Conor KERR; Ankit SHAH; M. Mukhlesur RAHMAN; Gadria M. M. SAIF-E-NASER; Poonam NIGAM; Lutfun NAHAR; Satyajit D. SARKER

2008-01-01

339

Phytochemical and biological studies on Nephelium longan (Estudios fitoquímicos y biológicos sobre Nephelium longan)  

Microsoft Academic Search

Extensive chromatographic separation and purification of the organic solvent extracts of Nephelium longan (Sapindaceae) stem bark afforded two compounds; scopoletin and stigmasterol. The structures of these compounds were determined by spectroscopic analyses, including 1H and 13C NMR. Different crude extracts (n-hexane, carbon tetrachloride, chloroform and methanol) were tested for antimicrobial activity by standard disc diffusion method known as the Kirby-Bauer

Khondaker M. RAHMAN; Kamrun NAHAR; Mohammad Gias; Uddin KHAN; Choudhury M. HASAN

340

A chemical extraction method for mimicking bioavailability of polycyclic aromatic hydrocarbons to wheat grown in soils containing various amounts of organic matter  

SciTech Connect

Severe contamination of agricultural soils by polycyclic aromatic hydrocarbons (PAHs) occurs in many places in China mainly as a result of coal and biomass combustion. Because ingestion is the main source of human exposure to PAHs and vegetables are basic ingredients for the Chinese diet, it is important to know how and to what extent PAHs are accumulated in vegetables produced in contaminated soils. This study, evaluated the extent to which organic matter contents in soils influence the accumulation of PAHs by the roots of wheat plants and have developed a rapid chemical method for determining the bioavailability of PAH. Four PAHs, naphthalene, acenaphthylene, fluorene, and phenanthrene, were added to natural soil samples with different amounts of organic matter for pot experiments to evaluate apparent bioavailability of PAHs to wheat roots (Triticum aestivum L.). The extractabilities of PAHs in the soil were tested by a sequential extraction scheme using accelerated solvent extraction with water, n-hexane, and a mixture of dichloromethane and acetone as solvents. The water or n-hexane-extractable PAHs were positively correlated to dissolved organic matter (DOM) and negatively correlated to total organic matter (TOM), indicating mobilization and immobilization effects of DOM and TOM on soil PAHs, respectively. The apparent accumulation of PAHs by wheat roots was also positively and negatively correlated to DOM and TOM, respectively. As a result, there are positive correlations between the amounts of PAHs extracted by water or n-hexane and the quantities accumulated in plant roots, suggesting the feasibility of using water- or n-hexanes-extractable fractions as indicators of PAH availability to plants. 19 refs., 8 figs., 1 tab.

Shu Tao; Fuliu Xu; Wenxin Liu; Yanhong Cui; Raymond M. Coveney, Jr. [Peking University, Beijing (China). Laboratory for Earth Surface Processes, College of Environmental Sciences

2006-04-01

341

Preparation of an efficient sorbent by washing then pyrolysis of olive wood for simultaneous solid phase extraction of chloro-phenols and nitro-phenols from water  

Microsoft Academic Search

Simultaneous preconcentration of phenol, 2-chlorophenol, 3-chlorophenol, 4-chlorophenol, 2-nitrophenol, 4-nitrophenol, and 2,4-dinitrophenol was improved by using olive wood (OW) washed with ethanol then pyrolyzed at 200°C as preconcentrating sorbent. Various OW sorbents were prepared by either washing OW (with ethanol, ether, dichloromethane, tetrahydrofuran or n-hexane); or by pyrolysis (at 100, 150, 200, 250 or 300°C); or by combined pyrolysis\\/washing. The adsorbents

Amjad H. El-Sheikh; Abdullah M. Alzawahreh; Jamal A. Sweileh

2011-01-01

342

A comparison of extraction and adsorption methods for the recovery of accelerants from arson debris  

Microsoft Academic Search

Two different methods of recovering arson accelerants from fire debris are compared: distillation with addition of n-hexane and adsorption onto activated charcoal. Both procedures involve the use of the gas chromatography\\/mass spectrometry (GC\\/MS) utilizing specific mass ion programs. Some casework examples have been analyzed and the results show that, in spite of the advantages of short application times in the

Luis Frontela; Jose A Pozas; Leandro Picabea

1995-01-01

343

Influence of Crystal Expansion/Contraction on Zeolite Membrane Permeation  

SciTech Connect

X-ray diffraction was used to measure the unit cell parameters of B-ZSM-5, SAPO-34, and NaA zeolite powders as a function of adsorbate loading at 303 K, and in one case, at elevated temperatures. Most adsorbates expanded the zeolite crystals below saturation loading at 303 K: n-hexane and SF6 in B-ZSM-5, methanol and CO2 in SAPO-34, and methanol in NaA zeolite. As the loadings increased, the crystals expanded more. Changes in the unit cell volumes of B-ZSM-5 and SAPO-34 zeolite powders correlated with changes in permeation through zeolite membranes defects. When the zeolite crystals expanded or contracted upon adsorption, the defect sizes decreased or increased. In B-ZSM-5 membranes, the fluxes through defects decreased dramatically when n-hexane or SF6 adsorbed. In contrast, i-butane adsorption at 303 K contracted B-ZSM-5 crystals at low loadings and expanded them at higher loadings. Correspondingly, the flux through B-ZSM-5 membrane defects increased at low i-butane loadings and decreased at high loading because the defects increased in size at low loading and decreased at high loadings. At 398 K and 473 K, n-hexane expanded the B-ZSM-5 unit cell more as the temperature increased from 303 to 473 K. The silicalite-1 and B-ZSM-5 unit cell volumes expanded similarly upon n-hexane adsorption at 303 K; boron substitution had little effect on volume expansion.

Sorenson, Stephanie G [University of Colorado, Boulder; Payzant, E Andrew [ORNL; Noble, Richard D [University of Colorado, Boulder; Falconer, John L. [University of Colorado, Boulder

2010-01-01

344

Optimierung der dünnschichtchromatographischen Trennung der Inhaltsstoffe der Extrakte von Digitalis purpurea auf Kieselgelschichten  

Microsoft Academic Search

The separation of the glycosides of Digitalis purpurea by thin-layer chromatography (TLC) on dry silica gel plates has been optimized. It was found that a complete assessment of the extracts can only be obtained if the polar primary glycosides are developed with ethylmethylketone; water (94.6?5.4) and the lower polar secondary glycosides and the aglycones with ethyl acetate: n-hexane: ethanol (65?15?10).

A. Janßen; D. Sopczak

1980-01-01

345

HPLC analysis of PCBs on porous graphitic carbon: Retention behavior and gradient elution  

Microsoft Academic Search

Summary  The fractionation of PCB congeners into classes according to their planarity (i.e. amount of ortho substitution) by HPLC on\\u000a porous graphitic carbon (PGC) as stationary phase has been investigated as a preliminary step before GC analysis, indispensable\\u000a for a complete separation of PCB congeners. A systematic study of retention behavior on PGC eluted with different n-hexane-dichloromethane\\u000a mixtures made it possible

M. C. Pietrogrande; A. Benvenuti; S. Previato; F. Dondi

2000-01-01

346

Sorption of Phthalates on Molecularly Imprinted Polymers  

Microsoft Academic Search

Porous type styrene\\/divinylbenzene (S\\/DVB) copolymer beads with dimethyl phthalate (DMP) imprinted footprints were obtained. The sorbents were prepared in two-step process: i) membrane emulsification, and ii) suspension polymerization. The average diameters of synthesised spheres were 40 µm for samples prepared in the presence of n-octane, and 30 µm for samples synthesized using n-hexane as a solvent. It was noted various sorption properties

Joanna Wolska; Marek Bryjak

2012-01-01

347

Isolation of anti-ulcerogenic sesquiterpene lactones from Centaurea solstitialis L. ssp. solstitialis through bioassay-guided fractionation procedures in rats  

Microsoft Academic Search

The fresh spiny flowers of Centaurea solstitialis ssp. solstitialis (CSS) are used for the treatment of peptic ulcers in Turkey. Ethanol (80%) extract of CSS exhibited significant anti-ulcerogenic effect on the ethanol-induced ulcerogenesis model in rats. The ethanol extract was further fractionated by successive solvent extractions with n-hexane, chloroform, ethyl acetate and n-butanol. All fractions showed significant anti-ulcerogenic activity, however,

Erdem Yesilada; Ilhan Gürbüz; Erdal Bedir; Irem Tatli; Ikhlas A. Khan

2004-01-01

348

Preparative isolation and purification of astaxanthin from the microalga Chlorococcum sp. by high-speed counter-current chromatography  

Microsoft Academic Search

High-speed counter-current chromatography was applied to the isolation and purification of astaxanthin from microalgae. The crude astaxanthin was obtained by extraction with organic solvents after the astaxanthin esters were saponified. Preparative high-speed counter-current chromatography with a two-phase solvent system composed of n-hexane–ethyl acetate–ethanol–water (5:5:6.5:3, v\\/v) was successfully performed yielding astaxanthin at 97% purity from 250 mg of the crude extract

Hua-Bin Li; Feng Chen

2001-01-01

349

Comparison of different extraction procedures for organic?fraction toxicity testing of urban sewages  

Microsoft Academic Search

n?Hexane microextraction, C18 solid?phase extraction (SPE) columns, liquid?liquid extraction, rotaevaporation, Kuderna?Danish concentration and Semi?Permeable Membrane Devices with triolein (SPMD), were used to extract the organic (lipophilic) fraction of 22 municipal effluent samples. The fractions were tested on a three?bioassay battery consisting of the short?term Daphnia magna immobilisation test, the microplate Chlorella vulgaris growth inhibition test, and the in vitro cytotoxicity

M Victoria Pablos; Carlos Férnandez; Carlos Valdovinos; Jose V. Tarazona

1999-01-01

350

Effects of temperature and mobile-phase composition on retentions in column liquid chromatography. [Hydroxyl-terminated polybutadiene  

Microsoft Academic Search

Binary-additive mobile phase systems were investigated for a more exact control over chromatography. If the mobile phase was nonpolar binary solvents (e.g., n-hexane and dichloromethane), trace amounts of THF and\\/or ACN could be added to control solute retentions as a function of solvent composition. Temperature also plays an important role in the coverage of modifier molecules on the surface of

1982-01-01

351

Role of rhenium and sulfur in platinum-based hydrocarbon-conversion catalysts  

Microsoft Academic Search

The effect of sulfiding on the structure and the activity of silica-supported platinum, rhenium, and platinum\\/rhenium was studied by ESCA, X-ray diffraction, adsorption and IR spectroscopy of carbon monoxide and hydrogen, and the activity and selectivity for n-hexane hydrogenolysis, isomerization, and aromatization at 200°⁻⁵°°sup 0\\/C. The platinum catalyst had a low-temperature (approx. 350°C) activity maximum for cracking, isomerization, and aromatization

P. Biloen; J. N. Helle; H. Verbeek; F. M. Dautzenberg; W. M. H. Sachtler

1980-01-01

352

High-performance liquid chromatographic method for the determination and pharmacokinetic study of oxypeucedanin hydrate and byakangelicin after oral administration of Angelica dahurica extracts in mongrel dog plasma  

Microsoft Academic Search

A high-performance liquid chromatographic method was developed and validated for the determination and pharmacokinetic study of oxypeucedanin hydrate and byak-angelicin after oral administration of Angelica dahurica extracts in mongrel dog plasma. The coumarin components and the internal standard isopsoralen were extracted from plasma samples with the mixture of tert-butyl methyl ether and n-hexane (4:1, v\\/v). Chromatographic separation was performed on

Ying Xie; Yi Chen; Mei Lin; Jun Wen; Guorong Fan; Yutian Wu

2007-01-01

353

Isolation of Imperatorin, Oxypeucedanin, and Isoimperatorin from Angelica dahurica (Fisch. ex Hoffm) Benth. et Hook by Stepwise Flow Rate High?Speed Countercurrent Chromatography  

Microsoft Academic Search

Stepwise flow rate preparative high?speed countercurrent chromatography (HSCCC) was successfully used for isolation and purification of imperatorin, oxypeucedanin, and isoimperatorin from a crude root extract of Angelica dahurica (Fisch. ex Hoffm) Benth. et Hook. The separation was performed with a two?phase solvent system composed of n?hexane?ethyl acetate?methanol?water at volume ratio of 5:5:4:6, v\\/v\\/v\\/v, which had been selected by analytical HSCCC.

Yun Wei; Yoichiro Ito

2006-01-01

354

Preparative isolation and purification of bergapten and imperatorin from the medicinal plant Cnidium monnieri using high-speed counter-current chromatography by stepwise increasing the flow-rate of the mobile phase  

Microsoft Academic Search

A high-speed counter-current chromatography (HSCCC) method was developed for the preparative separation and purification of bergapten and imperatorin from the Chinese medicinal plant Cnidium monnieri (L.) Cusson. The crude extract was obtained by extraction with ethanol from the dried fruits of Cnidium monnieri (L.) Cusson under sonication. Preparative HSCCC with a two-phase solvent system composed of n-hexane–ethyl acetate–ethanol–water (5:5:5:5, v\\/v\\/v\\/v)

Hua-Bin Li; Feng Chen

2004-01-01

355

Offline coupling of high-speed counter-current chromatography and gas chromatography\\/mass spectrometry generates a two-dimensional plot of toxaphene components  

Microsoft Academic Search

High-speed counter-current chromatography (HSCCC), a separation technique based solely on the partitioning of solutes between two immiscible liquid phases, was applied for the fractionation of technical toxaphene, an organochlorine pesticide which consists of a complex mixture of structurally closely related compounds. A solvent system (n-hexane\\/methanol\\/water 34:24:1, v\\/v\\/v) was developed which allowed to separate compounds of technical toxaphene (CTTs) with excellent

Thomas Kapp; Walter Vetter

2009-01-01

356

Comprehensive separation of secondary metabolites in natural products by high-speed counter-current chromatography using a three-phase solvent system  

Microsoft Academic Search

High-speed counter-current chromatography (HSCCC) using the three-phase solvent system n-hexane–methyl acetate–acetonitrile–water at a volume ratio of 4:4:3:4 was applied to the comprehensive separation of secondary metabolites in several natural product extracts. A wide variety of secondary metabolites in each natural product was effectively extracted with the three-phase solvent system, and the filtered extract was directly submitted to the HSCCC separation

Akio Yanagida; Yutaka Yamakawa; Ryoko Noji; Ako Oda; Heisaburo Shindo; Yoichiro Ito; Yoichi Shibusawa

2007-01-01

357

Preparative separation of rhein from Chinese traditional herb by repeated high-speed counter-current chromatography  

Microsoft Academic Search

High-speed counter-current chromatography (HSCCC) was repeatedly used for isolation and purification of rhein from Rheum officinale Baill (Dahuang) with a two-phase solvent system composed of n-hexane–ethyl acetate–methanol–water (3:7:5:5, v\\/v), which had been selected by analytical (HSCCC). Using two preparative units of the HSCCC centrifuge, about a 500mg amount of the crude extract was separated, yielding 6.7mg of rhein at a

Yun Wei; Tianyou Zhang; Yoichiro Ito

2003-01-01

358

Separation and Purification of dl-Tetrahydropalmatine from Corydalis Yanhusuo W. T. Wang by HSCCC with a New Solvent System Screening Method  

Microsoft Academic Search

A fast and simple solvent system screening method was established based on average polarity, which was much easier to find a suitable solvent system for high speed countercurrent chromatography separation. Dl-tetrahydropalmatine was separated and purified in one step with n-hexane-ethyl acetate-methanol-water (4-6-5-5) on high speed countercurrent chromatography. Acetic acid was successfully used to adjust the pH value of the sample

Shaojun Zhang; Xiaolei Wang; Fan Ouyang; Zhiguo Su; Changhai Wang; Ming Gu

2008-01-01

359

Preparative isolation and purification of lutein from the microalga Chlorella vulgaris by high-speed counter-current chromatography  

Microsoft Academic Search

High-speed counter-current chromatography (HSCCC) was applied to the isolation and purification of lutein from microalgae. Analytical HSCCC was used for the preliminary selection of a suitable solvent system composed of n-hexane–ethanol–water (4:3:1, v\\/v). Using the above solvent system, preparative HSCCC was successfully performed yielding lutein at 98% purity from 200 mg of the crude extract in a one-step separation.

Hua-Bin Li; Feng Chen; Tian-You Zhang; Fu-Quan Yang; Guo-Qing Xu

2001-01-01

360

Preparative isolation and purification of three rotenoids and one isoflavone from the seeds of Millettia pachycarpa Benth by high-speed counter-current chromatography  

Microsoft Academic Search

Both analytical and preparative high-speed counter-current chromatography (HSCCC) were used to isolate and separate chemical bioactive constituents from the seeds of Millettia pachycarpa Benth, a famous traditional Chinese medicine. Three rotenoids and one isoflavone were successfully purified for the first time by HSCCC with a two-phase solvent system composed of n-hexane–ethyl acetate–methanol–water (HEMWat) (1:0.8:1:0.6, v\\/v\\/v\\/v). The separation parameters were first

Haoyu Ye; Lijuan Chen; Yanfang Li; Aihua Peng; Afu Fu; Hang Song; Minghai Tang; Houding Luo; Youfu Luo; Yongbin Xu; Jianyou Shi; Yuquan Wei

2008-01-01

361

SEPARATION AND PURIFICATION OF MYRICITRIN FROM BAYBERRY TREE BARK BY HIGH-SPEED COUNTER-CURRENT CHROMATOGRAPHY  

Microsoft Academic Search

Myricitrin is a strong antioxidant agent and abundantly present in bayberry tree bark. The separation and purification of myricitrin from the crude extract of bayberry tree bark was achieved by high-speed counter-current chromatography (HSCCC) in the present study. An analytical HSCCC was used to screen the solvent system, and a two-phase solvent system composed of n-hexane–ethyl acetate– methanol–water (3:4:4:3, v\\/v)

Ying Fu; Zongyang Li; Jianyong Si; Qi Chang; Zhan Li; Ruile Pan

2012-01-01

362

Simultaneous determination of triclabendazole and its sulphoxide and sulphone metabolites in bovine milk by high-performance liquid chromatography  

Microsoft Academic Search

A simple method has been developed for the simultaneous determination of triclabendazole and its metabolites (sulphoxide and sulphone) in bovine milk by reversed-phase high-performance liquid chromatography (HPLC). A milk sample was homogenized with sodium sulfate anhydrous and acetonitrile, and centrifuged. The supernatant was isolated, rinsed with n-hexane saturated with acetonitrile, and evaporated. The residue was dissolved with 0.1 M potassium

Kazue Takeba; Kenji Fujinuma; Miho Sakamoto; Tomoyuki Miyazaki; Hisao Oka; Yuko Itoh; Hiroyuki Nakazawa

2000-01-01

363

Antimycotic activities of Cinnamon-derived compounds against Rhizoctonia solani in vitro  

Microsoft Academic Search

In this study, the effects of medicinal plant extracts on the development of mycelium in the following phytopathogenic fungi\\u000a were evaluated: Phytophthora capsici, Rhizoctonia solani, Fusarium solani, Colletotrichum gloeosprorioides, and Botrytis cinera. Of the 26 medicinal plants tested, six plant extracts showed antifungal activity against phytopathogenic fungi. The highest\\u000a antifungal activity was exerted against R. solani by the n-hexane fraction

Van-Nam Nguyen; Dang-Minh-Chanh Nguyen; Dong-Jun Seo; Ro-Dong Park; Woo-Jin Jung

2009-01-01

364

Application of preparative high-speed counter-current chromatography\\/preparative high-performance liquid chromatography mode in rapid separation of saponins  

Microsoft Academic Search

Combined with preparative high-performance liquid chromatography, high-speed counter-current chromatography was employed for isolation and purification of saponins from Gypsophila paniculata L. n-Hexane–n-butanol–methanol–0.02% TFA (1:9:1:9, v\\/v) was employed as solvent system and 210nm was chosen as the wavelength of ultraviolet detection for the first time. The research tried to compare HSCCC with prep-HPLC, and further integrated their advantages to improve separation

Shun Yao; Jianguang Luo; Xuefeng Huang; Lingyi Kong

2008-01-01

365

Bestimmung von Vitamin A in Lebensmitteln mittels Hochleistungs-Flüssigchromatographie (HPLC)  

Microsoft Academic Search

Summary A standard method using HPLC for the quantitative determination of vitamin A in food is described. The test material is saponified with aqueous ethanolic potassion hydroxide, and the vitamin A alcohol liberated is extracted with n-hexane. After concentration of the extract, the residue is dissolved in methanol and the vitamin A content determined, after HPLC separation on a RP-C-18

Antal Bognar

1986-01-01

366

An optimized and validated RP-HPLC\\/UV detection method for simultaneous determination of all-trans-Retinol (Vitamin A) and ?-Tocopherol (Vitamin E) in human serum: Comparison of different particulate reversed-phase HPLC columns  

Microsoft Academic Search

A novel, simple and fast reversed-phase HPLC\\/UV method was developed, optimized for various chromatographic conditions, and validated according to international guidelines for simultaneous determination of all-trans-retinol and ?-tocopherol in human serum using retinyl acetate as internal standard in the concentration of 0.5?g\\/ml. A liquid-phase extraction was applied to the 250?l of serum with n-hexane–dichloromethane mixture (70:30, v\\/v), in two steps,

Abad Khan; Muhammad I. Khan; Zafar Iqbal; Yasar Shah; Lateef Ahmad; David G. Watson

2010-01-01

367

Determination of Vitamin E in Coffee Beans by HPLC Using a Micro-extraction Method  

Microsoft Academic Search

This work reports a solid—liquid micro-extraction method for vitamin E quantification in coffee beans (before and after roasting) with normal-phase HPLC\\/diode-array\\/fluorescence detection. The compounds were extracted after protein precipitation and overnight maceration (4°C) in n-hexane, in the presence of butylated hydroxytoluene, using tocol as internal standard. The extraction method precision was inferior to 5% with mean recoveries near 100%. Chromatographic

R. C. Alves; S. Casal; M. B. P. P. Oliveira

2009-01-01

368

Process optimization studies on solvent extraction with naphthalene-2-boronic acid ion-pairing with trioctylmethylammonium chloride in sugar purification using design of experiments  

Microsoft Academic Search

The extraction of xylose and glucose from aqueous solution with naphthalene-2-boronic acid (N2B) in diluents of n-hexane:1-octanol (85:15 v\\/v) was investigated. The influence of pH, N2B concentration and phase ratio (O\\/W) (organic phase volume to aqueous phase volume) were investigated for an optimized condition of xylose and glucose extraction from the aqueous solution. The optimization process was analyzed using Central

H. Abdul Aziz; A. H. Kamaruddin; M. Z. Abu Bakar

2008-01-01

369

Microwave-induced combustion of volatile organic compounds in an industrial flue gas over the magnetite fixed-bed  

Microsoft Academic Search

A modified domestic microwave oven was applied to heat a magnetite (Fe3O4) fixed-bed for continuous decomposition of volatile organic compounds (VOCs), such as acetone, n-hexane, and dichloromethane (DCM), in a simulated flue gas which contains VOCs equivalent to 2000ppmv as DCM. Experimental results revealed that effect of the addition of water to the inlet stream on decomposition of DCM in

Bing-Nan Lee; Wai-Tsen Ying; Yao-Ting Shen

2007-01-01

370

Pervaporation characteristics of cross-linked poly(dimethylsiloxane) membranes for removal of various volatile organic compounds from water  

Microsoft Academic Search

The permeation and separation characteristics of volatile organic compounds (VOCs), such as chloroform, benzene, and toluene, from water by pervaporation through cross-linked poly(dimethylsiloxane) membranes prepared from poly(dimethylsiloxane) dimethylmethacrylate macromonomer (PDMSDMMA) and divinyl compounds, such as ethylene glycol dimethylmethacrylate (EGDM), divinyl benzene (DVB), divinyl siloxane (DVS), and divinyl perfluoro-n-hexane (DVF) are described. When aqueous solutions containing 0.05wt.% VOCs were permeated through

Tadahiro Ohshima; Yoshihisa Kogami; Takashi Miyata; Tadashi Uragami

2005-01-01

371

Stain Removal from a Silicone Maxillofacial Elastomer  

Microsoft Academic Search

In this study, environmental stains were removed from maxillofacial elastomers by solvent extraction. Silastic 44210, an RTV silicone with proven color and physical property stability, was stained with lipstick, disclosing solution, and methylene blue. These stains were then removed by solvent extraction with each of four chemically dissimilar solvents, namely: toluene, benzene, 1,1,1-trichloroethane, and n-hexane. An additional series of samples

R. Yu; A. Koran; C. N. Raptis; R. G. Craig

1981-01-01

372

Microwave roasting effects on the physico-chemical composition and oxidative stability of sunflower seed oil  

Microsoft Academic Search

The purpose of the present study was to explore the influences of microwave heating on the composition of sunflower seeds\\u000a and to extend our knowledge concerning the changes in oxidative stability, distribution of FA, and contents of tocopherols\\u000a of sunflower seed oil. Microwaved sunflower seeds (Helianthus annuus L.) of two varieties, KL-39 and FH-330, were extracted using n-hexane. Roasting decreased

Fozia Anjum; Farooq Anwar; Amer Jamil; M. Iqbal

2006-01-01

373

Study of complex formation between aluminum bromide and benzene by 27Al NMR spectroscopy  

Microsoft Academic Search

The reaction of aluminum bromide with benzene in n-hexane was studied by 27Al NMR spectroscopy in the temperature range from –80 to +20 °C. The formation of C6H6·Al2Br6 (1 : 2) complexes is accompanied by broadening of the resonance line with d 178. No peak splitting following a decrease in the temperature was observed but the temperature dependence of the

V. B. Murachev; A. I. Nesmelov

2001-01-01

374

Brown alga Sargassum muticum inhibits proinflammatory cytokines, iNOS, and COX2 expression in macrophage RAW 264.7 cells  

Microsoft Academic Search

The present study was designed to elucidate the pharmacological and biological effects of Sargassum muticum extracts on the production of inflammatory mediators in macrophages. S. muticum was extracted with 80% EtOH. The extract was then successively partitioned with n-hexane, CH2Cl2, EtOAc, BuOH, and water. The results indicate that the CH2Cl2 fraction of S. muticum extract was an effective inhibitor of

Weon-Jong YOON; Young Min HAM; Wook Jae LEE; Nam Ho LEE; Chang-Gu HYUN

375

Cold?start and chemical characterization of emissions from mobile sources in Mexico  

Microsoft Academic Search

In this work tailpipe and evaporative emissions from a set of normal and high emitter vehicle models, year 2006–2008 (low mileage) certified when new to meet the Tier 1 emission standard, were characterized for criteria pollutants (carbon monoxide, nitrogen oxides and hydrocarbons), and a suite of unregulated emissions including aliphatic and aromatic aldehydes, monocyclic aromatic compounds, 1,3 butadiene, n?hexane and

I. Schifter; L. Díaz; R. Rodríguez

2010-01-01

376

Microextraction of Chlorinated Benzenes and Selected Organochlorines from Environmental Water  

Microsoft Academic Search

This study describes the extraction of CBs and OCs from water by conventional means using only a few millilitres of solvent. The parameters investigated were volume of n-hexane versus time of extraction. The results clearly show several alternatives to the analyst, i.e., smaller volume-longer time or larger volume-shorter time. Typically, good recoveries could be achieved with as little as 5

C. Samson; V. N. Mallet; J. Doull; G. Brun

1996-01-01

377

The surface structure and reactivity of black carbon  

Microsoft Academic Search

Fourier transform infrared (FT-IR) spectroscopy has been the most definitive analytical tool in a comprehensive program on the structure and reactivity of black carbon (in the form of n-hexane soot). In combination with other techniques, it has revealed the soot structure, as produced by high temperature incomplete combustion, to be predominantly aromatic with a surface coverage by oxygen-containing functional groups

D. M. Smith; A. R. Chughtai

1995-01-01

378

Catalytic studies with ruthenium clusters substituted with diphosphines  

Microsoft Academic Search

The catalytic precursor Ru3(CO)10(Ph2PCH2PPh2)(dppm) (dppm=Ph2PCH2PPh2) isomerizes 1-hexene mainly to the kinetic product cis-2-hexene at low H2 pressure, and to n-hexane at higher hydrogenation conditions. The overall first order rate constant on substrate is 0.11 min?1. The compound hydrogenates other unsaturated groups in good yield. Turnover frequency studies indicate cluster catalysis.

Bernardo Fontal; Marisela Reyes; Trino Suárez; Fernando Bellandi; Juan Carlos D??az

1999-01-01

379

Heteropteran chemical repellents identified in the citrus odor of a seabird (crested auklet: Aethia cristatella ): evolutionary convergence in chemical ecology  

Microsoft Academic Search

The exogenous application of chemical repellents is widespread in birds, but endogenous production is exceedingly rare. We herein report a new class of avian defensive compounds isolated from the feathers and volatile odor of the crested auklet (Aethia cristatella). Mass spectra indicate that n-hexanal, n-octanal, n-decanal, Z-4-decenal and a 12-carbon unsaturated aldehyde comprise the auklet odorant. Octanal and hexanal are

H. D. Douglas; J. E. Co; T. H. Jones; W. E. Conner

2001-01-01

380

A Comparative Study of the Properties of Selected Melon Seed Oils as Potential Candidates for Development into Commercial Edible Vegetable Oils  

Microsoft Academic Search

A comprehensive compositional and characterization study was carried out on five seed oils from varieties of the melons Citrullus lanatus and C. colocynth in order to evaluate their suitability for large-scale exploitation as edible vegetable oils. The oils were extracted by\\u000a Soxhlet with a 3:1 mixture of n-hexane\\/2-propanol with yields that ranged from 24.8 to 30.0% (wt\\/wt). The refractive indices

M. B. Mabaleha; Y. C. Mitei; S. O. Yeboah

2007-01-01

381

Production of singlet molecular oxygen from the Oâ quenching of the lowest excited singlet state of rubrene  

Microsoft Academic Search

The efficiencies of the rubrene-sensitized photooxidation of 1,3-diphenylisobenzofuran in benzene, acetone, cyclohexane, n-hexane, and isooctane have been measured. The measured efficiencies are analyzed with data from the oxygen quenching of the rubrene fluorescence in the same solvents. It is shown that about 1.5 molecules of singlet oxygen are produced as a result of the primary process in which a rubrene

K. C. Wu; A. M. Trozzolo

1979-01-01

382

Pyrene-POSS nanohybrid as a dispersant for carbon nanotubes in solvents of various polarities: its synthesis and application in the preparation of a composite membrane  

NASA Astrophysics Data System (ADS)

In this study we report the preparation of nanohybrid dispersant molecules based on pyrene and polyhedral oligomeric silsesquioxanes for non-covalent functionalization of multi-walled carbon nanotubes (MWCNTs). The prepared dispersant improves the dispersion of MWCNTs in organic solvents with very different polarities such as tetrahydrofuran, toluene, and n-hexane. The functionalized MWCNTs were used to introduce conductivity into polydimethylsiloxane membranes which can be used for electrostatic discharge applications.

Majeed, Shahid; Filiz, Volkan; Shishatskiy, Sergey; Wind, Jan; Abetz, Clarissa; Abetz, Volker

2012-06-01

383

Enhanced enantioselectivity of lipase from Pseudomonas sp. at high temperatures and fixed water activity in the ionic liquid, 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide  

Microsoft Academic Search

The water activity equilibration over saturated salt solutions was monitored in the ionic liquid 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide and in two organic solvents (methyl tert-butylether and n-hexane). Water uptake by the ionic liquid was comparable to that in polar organic solvents. Furthermore, the kinetic resolution of (R,S)-1-phenylethanol catalysed by a lipase from Pseudomonas sp. had a higher selectivity in the ionic liquid

Marrit Eckstein; Peter Wasserscheid; Udo Kragl

2002-01-01

384

Pentacarbonyl(? 2-vinylferrocene)metal(0) complexes of Group 6 elements: synthesis and characterization  

Microsoft Academic Search

Photolysis of hexacarbonylmetal(0) complexes of the Group 6 elements in the presence of vinylferrocene in an n-hexane solution at ?15°C yields pentacarbonyl (?2-vinylferrocene)metal(0) complexes as the sole photo-substitution product, different from the general reaction pattern observed for the same Group 6 metal carbonyls with other olefins. M(CO)5(?2-vinylferrocene) complexes (M=Cr, Mo, W) could be isolated from the solution and characterized by

Saim Özkar; Ceyhan Kayran; Nazlan Demir

2003-01-01

385

Solvent effects on the electronic spectrum of Cââ  

Microsoft Academic Search

UV-vis absorption spectra of Cââ have been measured in 15 different organic solvents. There are substantial shifts in λ{sub max} values between gas phase spectra, n-hexane, aromatic solvents, and CSâ. The solvatochromic shifts of two of the bands due to the symmetry-allowed transitions, the HOMO-LUMO Aâ transition (1¹T{sub 1u} - 1¹Ag) around 405 nm and the C transition (3¹T{sub 1u}

Sean H. Gallagher; Robert S. Armstrong; Peter A. Lay; Christopher A. Reed

1995-01-01

386

Plasma patterning of carbon nanotubes  

Microsoft Academic Search

We have prepared micropatterns of carbon nanotubes on a wide range of substrates either by patterned growth of aligned nanotubes on surfaces prepatterned with plasma polymers (e.g., n-hexane plasma polymer) or through region-specific adsorption of certain chemically modified carbon nanotubes (e.g., -COOH substituted nanotubes) onto surfaces prepatterned with various plasma-generated functionalities (e.g., -NH2). Micropatterns of carbon nanotubes prepared in both

Qidao Chen; Liming Dai

2000-01-01

387

Determination of perospirone by liquid chromatography\\/electrospray mass spectrometry: Application to a pharmacokinetic study in healthy Chinese volunteers  

Microsoft Academic Search

Perospirone is a novel atypical antipsychotic with a unique combination of 5-HT1A receptor agonism as well as 5-HT2A and D2 receptor antagonism. A simple rapid and selective LC–MS method utilizing a single quadrupole mass spectrometer was developed and validated for the determination of perospirone hydrochloride in human plasma. N-hexane was used to extract perospirone hydrochloride and amlodipine benzenesulfonate (internal standard

Ning Ma; Wen-Ying Liu; Huan-De Li; Yun-Gui Zhu; Bi-Kui Zhang; Feng Wang; Rong-Hua Zhu; Da-Xiong Xiang

2007-01-01

388

The Effect of Air\\/Fuel Ratio on Properties and Reactivity of Combustion Soots  

Microsoft Academic Search

The dependence of specific properties of black carbon (BC) soots on fuel type and combustion conditions has been studied, and the effects of these properties on soot particle hydration and reaction with ozone determined. Series of soots were prepared from n-hexane, diesel and JP8 aircraft fuels, utilizing a flow combustion system designed for accurate control of the air\\/fuel ratio in

A. R. Chughtai; J. M. Kim; D. M. Smith

2002-01-01

389

Isolation and characterisation of some antifouling agents from the brown alga Sargassum confusum.  

PubMed

Fats and phthalic acid derivatives were isolated and characterised based on their spectral analysis from the antifouling activity guided fractions of n-hexane and methanol extract of the brown alga Sargassum confusum. The fractions, as well as the isolated compounds, demonstrated significant antifouling activity against spores of a major fouling alga Ulva pertusa with 50-75% decrease of spore attachment on agar-coated slides. PMID:16864441

Ganti, V S; Kim, K H; Bhattarai, H D; Shin, H W

2006-06-01

390

Attraction of the Parasitic Mite Varroa to the Drone Larvae of Honey Bees by Simple Aliphatic Esters  

Microsoft Academic Search

An important parasitic threat to honey bees, the mite Varroa jacobsoni, is attracted to its major prey, drone larvae, by methyl and ethyl esters of straight-chain fatty acids, in particular methyl palmitate. These esters were extracted from drone larvae with n-hexane and were identified by gas chromatography-mass spectrometry. Their behavioral effect was evaluated with the use of a four-arm airflow

Yves Le Conte; Gerard Arnold; Jerome Trouiller; Claudine Masson; Bertrand Chappe; Guy Ourisson

1989-01-01

391

Attraction of the Parasitic Mite Varroa to the Drone Larvae of Honey Bees by Simple Aliphatic Esters  

NASA Astrophysics Data System (ADS)

An important parasitic threat to honey bees, the mite Varroa jacobsoni, is attracted to its major prey, drone larvae, by methyl and ethyl esters of straight-chain fatty acids, in particular methyl palmitate. These esters were extracted from drone larvae with n-hexane and were identified by gas chromatography-mass spectrometry. Their behavioral effect was evaluated with the use of a four-arm airflow olfactometer.

Le Conte, Yves; Arnold, Gerard; Trouiller, Jerome; Masson, Claudine; Chappe, Bertrand; Ourisson, Guy

1989-08-01

392

Biosurfactants from Acinetobacter calcoaceticus BU03 enhance the solubility and biodegradation of phenanthrene  

Microsoft Academic Search

A thermophilic bacterial strain, Acinetobacter calcoaceticus BU03, with a biosurfactant?producing capability, was isolated from petroleum?contaminated soil with an improved procedure which employed the solubilization of polycyclic aromatic hydrocarnons (PAHs), i.e. naphthalene in agar plate, as a selection criterion. Crude biosurfactant was recovered from the culture of BU03 by extraction with n?hexane, and its properties were investigated. Biosurfactants from A. calcoaceticus

Zhenyong Zhao; Jonathan W. C. Wong

2009-01-01

393

Excited-state Raman spectroscopy with and without actinic excitation: S1 Raman spectra of trans-azobenzene  

NASA Astrophysics Data System (ADS)

We show that femtosecond stimulated Raman spectroscopy can record excited-state spectra in the absence of actinic excitation, if the Raman pump is in resonance with an electronic transition. The approach is illustrated by recording S1 and S0 spectra of trans-azobenzene in n-hexane. The S1 spectra were also measured conventionally, upon n?* (S0 ? S1) actinic excitation. The results are discussed and compared to earlier reports.

Dobryakov, A. L.; Quick, M.; Ioffe, I. N.; Granovsky, A. A.; Ernsting, N. P.; Kovalenko, S. A.

2014-05-01

394

Heat transfer enhancement resulting from induction electrohydrodynamic pumping  

E-print Network

pump and one designed specifically for efficient pumping at high tilt angles were tested to examine the heat transfer enhancement that occurs as a result of induction pumping. Two fluids, Dodecylbenzene and n-Hexane, were tested in the pumps... in designing an induction EHD pump. Forced convection cooling of underground power cables using EHD pumping was investigated by Crowley et al. (1983). Kuo (1982) applied finite element techniques to induction EHD pumping in a horizontal pipe. The numerical...

Margo, Bryan David

2012-06-07

395

High-performance liquid chromatography method to measure ?- and ?-tocopherol in leaves, flowers and fresh beans from Moringa oleifera  

Microsoft Academic Search

A high-performance liquid chromatography method for the microscale determination of ?- and ?-tocopherol in leaves, flowers and fresh beans from Moringa oleifera is reported. The method includes microscale saponification and extraction with n-hexane. Optimized conditions for reversed-phase HPLC with UV detection were as follows: column, 25cm×0.46cm, Exil ODS 5-?m; column temperature, 25°C; mobile phase, a 20:80 (v\\/v) mixture of methanol:acetonitrile;

D. I. Sánchez-Machado; J. López-Cervantes; N. J. Ríos Vázquez

2006-01-01

396

Antimicrobial and Cytotoxic Activities of Turbinaria conoides  

Microsoft Academic Search

Brown alga, Turbinaria conoides was successively extracted with n-hexane, cyclohexane, methanol and ethanol:water (1:1). The extracts were evaluated for antibacterial and antifungal activities by disc diffusion method. Minimal inhibitory concentration was determined for active extracts by broth dilution method. The antiviral activity and cytotoxicity of the extracts were tested in human embryonic lung (HEL) cells (herpes simplex virus-1, herpes simplex

J. Agardh; Sadish Kumar Shanmugam; Yatendra Kumar; Khan Mohammad Sardar Yar; Erik De Clercq

397

Trypanocidal, leishmanicidal and antifungal potential from marine red alga Bostrychia tenella J. Agardh (Rhodomelaceae, Ceramiales)  

Microsoft Academic Search

Specimens of the red alga Bostrychia tenella J. Agardh (Rhodomelaceae, Ceramiales) were collected from the São Paulo coast and submitted to room temperature solvent extraction. The resulting extract was fractionated by partitioning with organic solvent. The n-hexane (BT-H) and dichloromethane (BT-D) fractions showed antiprotozoal potential in biological tests with Trypanosoma cruzi and Leishmania amazonensis and presented high activity in an

Rafael de Felício; Sérgio de Albuquerque; Maria Cláudia Marx Young; Nair Sumie Yokoya; Hosana Maria Debonsi

2010-01-01

398

Extraction of epicuticular wax and nonacosan-10-OL from Ephedra herb utilizing supercritical carbon dioxide  

Microsoft Academic Search

Experimental results concerning the processing feasibility of using supercritical CO2 were reported for the extraction of epicuticular wax fromEphedra herb. Subsequently the isolability of nonacosan-10-ol from the total extract of epicuticular wax was evaluated by TLC and\\u000a gas chromatography. Also, Soxhlet extractions ofEphedra herb by n-hexane and chloroform were performed and these results were compared with those obtained by supercritical

Young Hae Choi; Jinwoong Kim; Min Jeong Noh; Eun Mee Park; Ki-Pung Yoo

1996-01-01

399

Treatment of dynamic mixture of hexane and benzene vapors in a Trickle Bed Air Biofilter integrated with cyclic adsorption/desorption beds.  

PubMed

One of the main challenges that face successful biofiltration is the erratic loading pattern and long starvation periods. However, such patterns are common in practical applications. In order to provide long-term stable operation of a biofilter under these conditions, a cyclic adsorption/desorption beds system with flow switching was installed prior to a biofilter. Different square waves of a mixture containing n-hexane and benzene at a 2:1 ratio were applied to the cyclic adsorption/desorption beds and then fed to a biofilter. The performance of this integrated system was compared to a biofilter unit receiving the same feed of both VOCs. The cyclic adsorption/desorption beds unit successfully achieved its goal of stabilizing erratic loading even with very sharp peaks at the influent concentration equalizing influent concentrations ranging from 10-470 ppmv for n-hexane to 30-1410 ppmv for benzene. The study included different peak concentrations with durations ranging from 6 to 20 min. The cyclic beds buffered the fluctuating influent load and the followed biofilter had all the time a continuous stable flow. Another advantage achieved by the cyclic adsorption/desorption beds was the uninterrupted feed to the biofilter even during the starvation where there was no influent in the feed. The results of the integrated system with regard to removal efficiency and kinetics are comparable to published results with continuous feed studies at the same loading rates. The removal efficiency for benzene had a minimum of 85% while for n-hexane ranged from 50% to 77% according to the loading rate. The control unit showed very erratic performance highlighting the benefit of the utilization of the cyclic adsorption/desorption beds. The biofilter was more adaptable to concentration changes in benzene than n-hexane. PMID:21074825

Aly Hassan, Ashraf; Sorial, George A

2011-01-01

400

Enzymatic esterification in organic media: role of water and organic solvent in kinetics and yield of butyl butyrate synthesis  

Microsoft Academic Search

The respective roles of organic solvent and of water in butyl butyrate synthesis from n-butanol and n-butyric acid in n-hexane by Mucor miehei lipase have been investigated by analysis of the kinetics and the reaction balances. Esterificaton was found to take place in both low water systems containing solid enzyme in hexane and in biphasic aqueous enzyme solution\\/hexane systems. In

Frédéric Monot; Frédérique Borzeix; Marc Bardin; Jean-Paul Vandecasteele

1991-01-01

401

Characterization of Moringa oleifera Seed Oil Variety “Periyakulam 1”  

Microsoft Academic Search

The oil from Moringa oleifera seeds variety Periyakulam 1 (PKM 1) from India was extracted using three different procedures including cold press (CP), extraction with n-hexane (H) and extraction with a mixture of chloroform:methanol (1:1) (CM). The oils were compared with those of a commercial virgin olive oil and Moringa oleifera var. Mbololo seed oil. The oil concentration ranged from

Stavros Lalas; John Tsaknis

2002-01-01

402

Characterization of Moringa oleifera Variety Mbololo Seed Oil of Kenya  

Microsoft Academic Search

The oil from Moringa oleifera variety Mbololo seeds from Kenya was extracted using three different procedures including cold press (CP), extraction with n-hexane (H), and extraction with a mixture of chloroform\\/methanol (50:50) (CM). The oil concentration ranged from 25.8% (CP) to 31.2% (CM). The density, refractive index, color, smoke point, viscosity, acidity, saponification value, iodine value, fatty acid methyl esters,

J. Tsaknis; S. Lalas; V. Gergis; V. Dourtoglou; V. Spiliotis

1999-01-01

403

Alkaline Titrations of poly(dG-dC)·poly(dG-dC): Microemulsion Versus Solution Behavior  

Microsoft Academic Search

PolyGC was titrated with a strong base in the presence of increasing concentrations of NaCl (from 0.00 to 0.60M) either in water solution or with the polynucleotide solubilized in the aqueous core of reverse micelles, i.e., the cationic quaternary water-in-oil microemulsion CTAB\\/n-hexane\\/n-pentanol\\/water. The results for matched samples in the two media were compared. CD and UV spectroscopies and, for the

Marta Airoldi; Giuseppe Gennaro; Marcello Giomini; Anna Maria Giuliani; Mauro Giustini

2007-01-01

404

Antimicrobial Activity and Brine Shrimp Lethality Bioassay of the Leaves Extract of Dillenia indica Linn  

PubMed Central

The crude methanolic extract of Dillenia indica Linn. (Dilleniaceae) leaves has been investigated for the evaluation of antimicrobial and cytotoxic activities. Organic solvent (n-hexane, carbon tetrachloride and chloroform) fractions of methanolic extract and methanolic fraction (aqueous) were screened for their antimicrobial activity by disc diffusion method. Besides, the fractions were screened for cytotoxic activity using brine shrimp (Artemia salina) lethality bioassay. Among the four fractions tested, n-hexane, carbon tetrachloride, and chloroform fractions showed moderate antibacterial and antifungal activity compared to standard antibiotic, kanamycin. The average zone of inhibition was ranged from 6 to 8 mm at a concentration of 400 µg/disc. But the aqueous fraction was found to be insensitive to microbial growth. Compared to vincristine sulfate (with LC50 of 0.52 µg/ ml), n-hexane and chloroform fractions demonstrated a significant cytotoxic activity (having LC50 of 1.94 µg/ml and 2.13 µg/ml, respectively). The LC50 values of the carbon tetrachloride and aqueous fraction were 4.46 µg/ml and 5.13 µg/ ml, respectively. The study confirms the moderate antimicrobial and potent cytotoxic activities of Dillenia indica leaves extract and therefore demands the isolation of active principles and thorough bioassay. PMID:21331191

Apu, AS; Muhit, MA; Tareq, SM; Pathan, AH; Jamaluddin, ATM; Ahmed, M

2010-01-01

405

Computational study of hydrocarbon adsorption in metal-organic framework Ni2(dhtp)  

SciTech Connect

Molecular dynamic simulations were carried out to study the sorption, structural properties, and diffusivities of n-hexane and cyclohexane adsorbed in Ni2(dhtp). The results indicated strong interactions between the alkanes and the host material. The free energy perturbation method was employed to investigate the adsorption free energies of methane, ethane, n-butane, n-hexane and cyclohexane. For linear alkanes, the free energy lowered as the length of the carbon chain increased. Also, the adsorption of n-hexane was preferred over cyclohexane, due to its ability to rearrange its structure to maximize contacts with the host. Furthermore, due to the large pore size of Ni2(dhtp), higher loadings of alkanes did not significantly affect the alkane structure, and enhanced the free energy of adsorption for subsequent alkanes being loaded. According to our studies, Ni2(dhtp) has a very promising potential for adsorption and storage of alkanes. This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

Sun, Xiuquan; Wick, Collin D.; Thallapally, Praveen K.; McGrail, B. Peter; Dang, Liem X.

2011-03-31

406

Antidiabetic effect of Equisetum arvense L. (Equisetaceae) in streptozotocin-induced diabetes in male rats.  

PubMed

In view of alleged antidiabetic potential effect of the methanol, n-hexan and dichloromethane extracts of Equisetum arvense of blood sugar and body weight in streptozotocin-induced (50 mg kg(-1), i.p. dissolved in normal saline) diabetic rats were investigated. The blood glucose lowering activity of the methanol, n-hexan and dichloromethane extracts was determined in steptozotocin-induced diabetic rats; after oral administration in doses of 50, 100, 250 and 500 mg kg(-1) daily for 5 weeks. The data was compare statistically using one-way ANOVA tukey test. The results showed that in different doses of methanolic extract, dichloromethane extract at doses of 50 and 250 mg kg(-1) and n-hexan extract (50 mg kg(-1)), blood sugar decreased significantly in comparison with the treatment and control groups of diabetic rats. Also the weights of methanolic-extract treatment group were higher than the other treatment groups. The present studies clearly indicate a significant antidiabetic effect with the methanolic extract of Equisetum arvense and lend support for its traditional usage. Further investigation on identification of the active principles and their mode of action are needed to unravel the molecular mechanisms involved in the observed effects. PMID:19086514

Safiyeh, Soleimani; Fathallah, Fathiazar Baijani; Vahid, Nejati; Hossine, Nazemiyeh; Habib, Shojaei Sadee

2007-05-15

407

Blood pressure-lowering and vascular modulator effects of Acorus calamus extract are mediated through multiple pathways.  

PubMed

This investigation was aimed to provide a pharmacologic basis to the medicinal use of Acorus calamus in cardiovascular disorders. In normotensive anesthetized rats, crude extract of Acorus calamus and its ethylacetate and nHexane fractions caused a fall in mean arterial pressure. In rabbit aorta rings, crude extract was more potent against high K (80 mM), ethylacetate against phenylephrine (1 microM), whereas nHexane fraction was equipotent against both precontractions. Crude extract exhibited a vasoconstrictor effect on baseline. Pretreatment of aortic rings with crude extract and its fractions shifted Ca concentration-response curves to the right, similar to verapamil. Crude extract and ethylacetate fraction suppressed phenylephrine peak formation in Ca-free medium. In rat aorta preparations, crude extract exhibited endothelium-independent relaxation with a vasodilatory effect against high K. nHexane fraction caused an endothelium-dependent Nomega-nitro-l-arginine methyl ester-sensitive vasorelaxant along with ryanodine-sensitive vasoconstrictor effect on baseline tension and partially inhibited high K, although ethylacetate fraction caused an endothelium-independent relaxant and endothelium-dependent vasoconstrictor effect. These data indicate that crude extract possesses a combination of effects, relaxant effects mediated possibly through Ca antagonism in addition to a nitric oxide pathway, although the associated vasoconstrictor effects may be meant by nature to offset excessive vasodilatation, thus providing a pharmacologic rationale to its cardiovascular medi-cinal uses. PMID:19528816

Shah, Abdul Jabbar; Gilani, Anwarul Hassan

2009-07-01

408

Antimicrobial Activity and Brine Shrimp Lethality Bioassay of the Leaves Extract of Dillenia indica Linn.  

PubMed

The crude methanolic extract of Dillenia indica Linn. (Dilleniaceae) leaves has been investigated for the evaluation of antimicrobial and cytotoxic activities. Organic solvent (n-hexane, carbon tetrachloride and chloroform) fractions of methanolic extract and methanolic fraction (aqueous) were screened for their antimicrobial activity by disc diffusion method. Besides, the fractions were screened for cytotoxic activity using brine shrimp (Artemia salina) lethality bioassay. Among the four fractions tested, n-hexane, carbon tetrachloride, and chloroform fractions showed moderate antibacterial and antifungal activity compared to standard antibiotic, kanamycin. The average zone of inhibition was ranged from 6 to 8 mm at a concentration of 400 µg/disc. But the aqueous fraction was found to be insensitive to microbial growth. Compared to vincristine sulfate (with LC(50) of 0.52 µg/ ml), n-hexane and chloroform fractions demonstrated a significant cytotoxic activity (having LC(50) of 1.94 µg/ml and 2.13 µg/ml, respectively). The LC(50) values of the carbon tetrachloride and aqueous fraction were 4.46 µg/ml and 5.13 µg/ ml, respectively. The study confirms the moderate antimicrobial and potent cytotoxic activities of Dillenia indica leaves extract and therefore demands the isolation of active principles and thorough bioassay. PMID:21331191

Apu, As; Muhit, Ma; Tareq, Sm; Pathan, Ah; Jamaluddin, Atm; Ahmed, M

2010-01-01

409

In vitro antimicrobial activity on clinical microbial strains and antioxidant properties of Artemisia parviflora  

PubMed Central

Background Artemisia parviflora leaf extracts were evaluated for potential antimicrobial and antioxidant properties. Antimicrobial susceptibility assay was performed against ten standard reference bacterial strains. Antioxidant activity was analyzed using the ferric thiocyanate and 2, 2-Diphenyl-1-Picrylhydrazyl (DPPH) assays. Radical scavenging activity and total phenolic content were compared. Phytochemical analyses were performed to identify the major bioactive constitution of the plant extract. Results Hexane, methanol and ethyl acetate extracts of A. parviflora leaves exhibited good activity against the microorganisms tested. The n-hexane extract of A. parviflora showed high inhibition of the growth of Pseudomonas aeruginosa, Escherichia coli and Shigella flexneri. Methanol extract showed strong radical scavenging and antioxidant activity, other extracts showed moderate antioxidant activity. The major derivatives present in the extracts are of terpenes, steroids, phenols, flavonoids, tannins and volatile oil. Conclusions The results obtained with n-hexane extract were particularly significant as it strongly inhibited the growth of P. aeruginosa, E. coli and S. flexneri. The major constituent of the n-hexane extract was identified as terpenes. Strong antioxidant activity could be observed with all the individual extracts. The antimicrobial and antioxidant property of the extracts were attributed to the secondary metabolites, terpenes and phenolic compounds present in A. parviflora and could be of considerable interest in the development of new drugs. PMID:23171441

2012-01-01

410

Anticonvulsive activity of Butea monosperma flowers in laboratory animals.  

PubMed

The bioassay-guided fractionation of dried flowers of Butea monosperma (BM) was carried out to isolate the active principle responsible for its anticonvulsant activity. The petroleum ether extract was fractionated by column chromatography using solvents of varying polarity such as n-hexane, n-hexane:ethyl acetate, ethyl acetate, and methanol. The anticonvulsive principle of B. monosperma was found to be a triterpene (TBM) present in the n-hexane:ethyl acetate (1:1) fraction of the petroleum ether extract. TBM exhibited anticonvulsant activity against seizures induced by maximum electroshock (MES) and its PD(50) was found to be 34.2+/-18.1 mg/kg. TBM also inhibited seizures induced by pentylenetetrazol (PTZ), electrical kindling, and the combination of lithium sulfate and pilocarpine nitrate (Li-Pilo). However, TBM was not effective against seizures induced by strychnine and picrotoxin. TBM exhibited depressant effect on the central nervous system. After repeated use for 7 days, the PD(50) (MES) of TBM increased to 51.5+/-12.1 mg/kg. Similarly, after repeated use of TBM, the duration of sleep induced by pentobarbital was not reduced significantly. Further studies are required to investigate its usefulness in the treatment of epilepsy. PMID:12062587

Kasture, Veena S; Kasture, S B; Chopde, C T

2002-07-01

411

Profile of volatile components of hydrodistilled and extracted leaves of Jacaranda acutifolia and their antimicrobial activity against foodborne pathogens.  

PubMed

Volatile constituents of the essential oil and n-hexane extract of Jacaranda acutifolia Humb. and Bonpl. (Bignoniaceae) leaves were determined, and their antimicrobial activities were investigated using an agar diffusion method. The minimum inhibitory concentrations (MIC) were determined and compared with those of standard antibiotics (penicillin, gentamicin and nystatin). The chemical composition of the oils was analyzed by capillary gas chromatography (GLC-FID) and gas chromatography-mass spectrometry (GLC-MS). Thirty-four components, comprising almost 93.8% of the total peak area, were identified in the leaf essential oil. The main components were methyl linolenate (26.7%), 1-octen-3-ol (10.8%), methyl phenyl acetate (9.9%), beta-linalool (5.5%) and palmitic acid (4.7%). The n-hexane extract revealed similar oil constituents, but also p-benzoquinone, phenyl acetic acid, resorcinol and homogentisic acid. The oil showed some activity against Staphylococcus aureus and Escherichia coli with MIC values of 2.2 and 2.9 mg/mL, respectively, and moderate activity against Candida albicans, Salmonella typhimurium and Shigella flexneri. The n-hexane extract showed moderate activities against all tested microorganisms, with MIC values ranging from 3.5 to 10.2 mg/mL. The antimicrobial activities of the hydrodistilled and extracted leaves make their local traditional uses rational. PMID:25230515

Singab, Abdel Nasser B; Mostafa, Nada M; Eldahshan, Omayma A; Ashour, Mohamed L; Wink, Michael

2014-07-01

412

Simultaneous extraction of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and coplanar polychlorinated biphenyls from contaminated soil using pressurized liquid extraction.  

PubMed

Pressurized liquid extraction (PLE) was studied for simultaneous extractions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/PCDFs), and of coplanar polychlorinated biphenyls (Co-PCBs) from a tightly bounded condition in the soil matrix. Temperatures were maintained at 175 and 200 degrees C, respectively, and two or three static cycles for single PLE with toluene and acetone/n-hexane were studied using a certified reference material to compare the effects of those conditions on recoveries. A single PLE with two static cycles at 150 degrees C and the repeated single PLE (additional PLE) were reference methods. Satisfactory recoveries were not obtained using tested single PLE (2,3,7,8-substituted PCDD/PCDFs and Co-PCBs average, average (avg.) 79-103%), but they were achieved using additional PLE (acetone/n-hexane, avg. 115-128%; toluene, avg. 111-132%). In addition, these methods and additional PLE of the reference method using acetone/n-hexane were not markedly different (avg. 123-128%). That fact suggests that the use of mixed solvents and additional PLE were more important factors than temperatures and static cycles of single PLE for quantitative and simultaneous extractions of those compounds from the soil. PMID:17306281

Kiguchi, Osamu; Saitoh, Katsumi; Ogawa, Nobuaki

2007-03-16

413

Determination of 2,5-hexanedione in urine by headspace solid-phase microextraction and gas chromatography.  

PubMed

2,5-Hexanedione (2,5-HD) is the most important metabolite of n-hexane and methyl ethyl ketone in human urine. Urinary 2,5-HD is used as a biomarker for biological monitoring of workers exposed to n-hexane. A simple method using headspace solid-phase microextraction (HS-SPME) and gas chromatography (GC) equipped with a flame-ionization detector (FID) was developed. The parameters that affect the HS-SPME-GC-FID process were optimized (i.e., fiber coating, sample volume, adsorption and heating time, salt addition, and extraction temperature). The assay presented linearity in the range of 0.075 to 20.0 mg/L, precision (coefficient of variation < 7.0%), and detection limit of 0.025 mg/L for 2,5-HD in urine. The method was successfully applied to the analysis of 2,5-HD in urine samples from eight workers occupationally exposed to n-hexane in shoemaker's glue. PMID:19470226

Oliveira, Antônio Felipe F; Maia, Patrícia P; Paiva, Maria José N; Siqueira, Maria Elisa P B

2009-05-01

414

Para rubber seed oil: new promising unconventional oil for cosmetics.  

PubMed

Para rubber seed was macerated in petroleum ether and n-hexane, individually, for 30 min. The extraction was additionally performed by reflux and soxhlet for 6 h with the same solvent and proportion. Soxhlet extraction by petroleum ether afforded the greatest extractive yield (22.90 ± 0.92%). Although antioxidant activity by means of 1, 1-diphenyl-2-picrylhydrazyl (DPPH) assay was insignificantly differed in soxhleted (8.90 ± 1.15%) and refluxed (9.02 ± 0.71%) by n-hexane, soxhlet extraction by n-hexane was significantly (p < 0.05) potent scavenged 2,2'-azino-bis(3-ethylbenzothaiazoline)-6-sulfonic acid) or ABTS radical with trolox equivalent antioxidant capacity (TEAC) of 66.54 ± 6.88 mg/100 g oil. This extract was non cytotoxic towards normal human fibroblast cells. In addition, oleic acid and palmitic acid were determined at a greater content than in the seed of para rubber cultivated in Malaysia, although linoleic and stearic acid contents were not differed. This bright yellow extract was further evaluated on other physicochemical characters. The determined specific gravity, refractive index, iodine value, peroxide value and saponification value were in the range of commercialized vegetable oils used as cosmetic raw material. Therefore, Para rubber seed oil is highlighted as the promising ecological ingredient appraisal for cosmetics. Transforming of the seed that is by-product of the important industrial crop of Thailand into cosmetics is encouraged accordingly. PMID:24976614

Lourith, Nattaya; Kanlayavattanakul, Mayuree; Sucontphunt, Apirada; Ondee, Thunnicha

2014-01-01

415

In vitro antiprotozoal activity of extracts of five Turkish Lamiaceae species.  

PubMed

The in vitro antiprotozoal activities of crude methanolic extracts from the aerial parts of five Lamiaceae plants (Salvia tomentosa, S. sclarea, S. dichroantha, Nepeta nuda subsp. nuda and Marrubium astracanicum subsp. macrodon) were evaluated against four parasitic protozoa, i.e. Trypanosoma brucei rhodesiense, T. cruzi, Leishmania donovani and Plasmodium falciparum. The cytotoxic potentials of the extracts on L6 cells were also evaluated. Melarsoprol, benznidazole, miltefosine, chloroquine and podophyllotoxin were used as reference drugs. All crude MeOH extracts showed antiprotozoal potential against at least three parasites, so they were dispersed in water and partitioned against n-hexane and chloroform to yield three subextracts that were screened in the same test systems. The n-hexane extract of N. nuda was the most active against T. brucei rhodesiense while the CHCl3 extracts of S. tomentosa and S. dichroantha showed significant activity against L. donovani. All organic extracts displayed in vitro antimalarial and moderate trypanocidal activities against T. cruzi with the n-hexane extract of S. sclarea being the most active against the latter. The extracts displayed low or no cytotoxicity towards mammalian L6 cells. PMID:22224291

Kirmizibekmez, Hasan; Atay, Irem; Kaiser, Marcel; Yesilada, Erdem; Tasdemir, Deniz

2011-11-01

416

KEY COMPARISON: International comparison CCQM-K54: Primary standard gas mixtures of hexane in methane  

NASA Astrophysics Data System (ADS)

The aim of this comparison is to evaluate the gravimetry and purity verification of gas mixtures prepared by introducing a liquid into a gas cylinder. This type of preparation is well known from, e.g., ethanol in nitrogen/air (CCQM-K4), and n-hexane in synthetic natural gas (CCQM-K16). The choice for n-hexane in methane is based on the relevance of natural gas primary standard mixtures and higher hydrocarbons in synthetic natural gas (for, e.g., dew point calibrations). Furthermore, n-hexane is relatively straightforward to analyse using a GC/FID (gas chromatograph equipped with a flame ionisation detector) with good repeatability. Eight laboratories participated. After the data evaluation, the result of one laboratory was eliminated to arrive at a consistent subset. The quality of the fitted line was not overly good, leading to small discrepancies in the degrees-of-equivalence calculated for three other laboratories. Only four laboratories are consistent with the KCRV. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

van der Veen, Adriaan M. H.; Chander, Hima; Ziel, Paul R.; Wessel, Rob M.; de Leer, Ed W. B.; Smeulders, Damian; Besley, Laurie; Kato, Kenji; Watanabe, Takuro; Seog Kim, Jin; Woo, Jin-Chun; Bae, Hyun Kil; Doo Kim, Yong; Pérez Castorena, Alejandro; Rangel Murillo, Francisco; Serrano Caballero, Victor M.; Ramírez Nambo, Carlos; de Jesús Avila Salas, Manuel; Konopelko, Leonid A.; Popova, Tatjana A.; Pankratov, V. V.; Kovrizhnih, M. A.; Kuzmina, T. A.; Efremova, O. V.; Kustikov, Yury A.; Milton, Martin J. T.; Vargha, Gergely; Guenther, Frank R.; Rhoderick, George C.

2010-01-01

417

Effects of additives on prebreakdown phenomena in liquid cyclohexane: II. Streamer propagation  

NASA Astrophysics Data System (ADS)

Streamer propagation in cyclohexane with various additives have been studied with fast impulses applied to a point-to-plane gap. The additives are perfluoro-n-hexane, N,N-dimethylaniline, 1-methylnaphthalene, di-n-propylether, 1,1-difluorocyclopentane and 1,4-benzoquinone, representing molecules with different electrochemical properties. We have used shadowgraphic imaging and a differential charge-measurement technique with a sensitivity of 0.1 pC to integrate currents induced to the point electrode during streamer propagation. The propagation is to various degrees facilitated by the additives. Perfluoro-n-hexane affects point cathode streamers, N,N-dimethylaniline and di-n-propylether affect point anode streamers, while 1-methylnaphthalene and 1,4-benzoquinone affect both point anode and point cathode streamers. 1,1-difluorocyclopentane is the only additive without a measurable effect in either point polarity. Largest effects are found for perfluoro-n-hexane, N,N-dimethylaniline and 1-methylnaphthalene, which are the only additives to produce a visible change in streamer appearances. In these cases, filaments become thinner and fewer, while propagating faster and sometimes further. The results follow expectations, considering point cathode streamers to be governed mainly by injection of thermal electrons from a gaseous phase, and point anode streamers to be governed mainly by more energetic electrons, extracted from the liquid at higher electric fields.

Ingebrigtsen, S.; Lundgaard, L. E.; Åstrand, P.-O.

2007-09-01

418

Combined nitrogen, hexane, and benzene adsorption characterization of pores and surfaces of lyophobic mesoporous silicas.  

PubMed

For lyophobic porous surfaces, structural analysis by vapor adsorption is complicated due to weak adsorbate-adsorbent interactions and limited wetting of the pores (nonzero contact angles). To investigate further, adsorption isotherms of three distinct adsorbates (nitrogen - 77 K, n-hexane and benzene - 298 K) were studied for SBA-15 ordered mesoporous silica where the surface was functionalized with lyophobic perfluoroalkyl groups (C6F13 termini). The results demonstrated a clear advantage of the combined use of the adsorption isotherms of less surface sensitive (nitrogen) and more surface sensitive (hydrocarbons) adsorbates. The adsorption of nitrogen provided basic structural characteristics like surface area, pore volume, and pore size distribution, while the isotherms of benzene and n-hexane were used to characterize wetting (contact angles) and surface energy of the C6F13 surfaces within the pores. For the first time, the statistical film thickness for nitrogen, benzene, and n-hexane are being reported for the adsorption on fluorinated surfaces, thereby providing critical data for the pore size and the contact angle determination of the lyophobic materials. PMID:25040549

Roshchina, T M; Shonija, N K; Bernardoni, F; Fadeev, A Y

2014-08-12

419

Interaction forces between asphaltene surfaces in organic solvents.  

PubMed

The colloidal interactions between asphaltene surfaces in heptol, a mixture of n-heptane and toluene, were studied for the first time by colloidal force measurements using an atomic force microscope (AFM). Asphaltenes were deposited on silica wafers and silica spheres using the Langmuir-Blodgett upstroke technique. The results showed that the ratio of toluene to heptane can significantly change solvent quality in terms of the ability to solubilize asphaltenes and hence the nature and the magnitude of the interaction forces between asphaltene surfaces. In pure toluene, there is a steric long-range repulsion which can be well fitted by the scaling theory of polymer brushes. As toluene volume fraction in heptol (Phi(T)) is gradually decreased from Phi(T) = 1 (pure toluene) to Phi(T) = 0 (pure n-heptane), the steric repulsion reduced and changed to weak attraction when Phi(T) < 0.2. The attraction in heptane can be fitted by van der Waals forces alone which are thus believed to promote asphaltene aggregation, leading to asphaltene precipitation. The results obtained in this study provide an insight into interactions that determine asphaltene behavior in an organic medium and hence in crude oils. PMID:19645456

Wang, Shengqun; Liu, Jianjun; Zhang, Liyan; Masliyah, Jacob; Xu, Zhenghe

2010-01-01

420

Spectroscopic Studies of Intramolecular Proton Transfer in 2-(4-Fluorophenylamino)-5-(2,4-Dihydroxybenzeno)-1,3,4-Thiadiazole  

PubMed Central

Spectroscopic studies of the biologically active compound 2-(4-fluorophenylamino)-5-(2,4-dihydroxybenzeno)-1,3,4-thiadiazole (FABT), have been performed. Absorption studies in the UV-Vis region for FABT in polar solvents, like water or ethanol, exhibit the domination of the enol form over its keto counterpart, with a broad absorption band centered around 340 nm. In non-polar solvents such as n-heptane or heavier alkanes the 340 nm absorption band disappears and an increase of the band related to the keto form (approximately 270 nm) is observed. Fluorescence spectra (with 270 nm and 340 nm excitation energies used) show a similar dependence: for FABT in 2-propanol a peak at about 400 nm dominates over that at 330 nm while in n-heptane this relation is reversed. The solvent dependent equilibrium between the keto and enol forms is further confirmed by FTIR and Raman spectroscopies. As can be expected, this equilibrium also shows some temperature dependences. We note that the changes between the two tautomeric forms of FABT are not related to the permanent dipole moment of the solvent but rather to its dipole polarizability. PMID:20535632

Matwijczuk, Arkadiusz; Kaminski, Daniel; Niewiadomy, Andrzej; Kowalski, Radoslaw; Karwasz, Grzegorz P.

2010-01-01

421

Isolation of terpenoids from Pimpinella anisum essential oil by high-performance counter-current chromatography.  

PubMed

High-performance counter-current chromatography was successfully used for the isolation and purification of terpenoid compounds from the essential oil of Pimpinella anisum L. A two-phase solvent system composed of n-heptane/methanol/ethyl acetate/water (5:2:5:2, v/v/v/v) was suitable for the purification of linalool, terpinen-4-ol, ?-terpineol, p-anisaldehyde, while n-heptane/methanol (1:1, v/v) was used for the isolation of anethole and foeniculin. A scale-up process from analytical to preparative was developed. Additionally, a stepwise gradient elution was applied and instead of two different runs, 40 min each, one 80 min separation was performed; although the time of separation remains the same, it was possible to repeat the efficiency even if the water-containing mobile phase was changed to a nonaqueous system. The obtained essential oil, as well as purified compounds, was analyzed by GC. A total of 0.64 mg of linalool, 0.52 mg of terpinen-4-ol, 0.10 mg of ?-terpineol, 0.62 mg of p-anisaldehyde, 15 mg of anethole, and 2.12 mg of foeniculin were obtained from 210 mg of the essential oil of P. anisum L. in a short time with purities of 99, 98, 94, 93.54, 93, and 93.6%, respectively. PMID:23749680

Skalicka-Wo?niak, Krystyna; Walasek, Magdalena; Ludwiczuk, Agnieszka; G?owniak, Kazimierz

2013-08-01

422

Isolation and purification of series bioactive components from Hypericum Perforatum L. by high-speed counter-current chromatography  

PubMed Central

High-speed counter-current chromatography (HSCCC) combined with pre-separation by ultrasonic solvent extraction was successively used for the separation of series bioactive compounds from the crude extract of Hypericum perforatum L. The petroleum ether extract was separated by the solvent system of n-heptane-methanol-acetonitrile (1.5:0.5:0.5, v/v) and n-heptane-methanol (1.5:1, v/v) in gradient elution, yielding a phloroglucinol compound, hyperforin with HPLC purity over 98%. The ethyl acetate extract was separated by using the solvent system composed of hexane-ethyl acetate-methanol-water (1:1:1:1 and 1:3:1:3, v/v) in gradient through both reverse phase and normal phase elution mode, yielding a naphthodianthrone compound, hypericin with HPLC purity about 95%. The n-butanol extract was separated with the solvent system composed of n-butanol-ethyl acetate–water (1:4:5 and 1.5:3.5:5, v/v) in elution and back-extrusion mode, yielding two of flavones, rutin and hyperoside, with HPLC purity over 95%. HPLC-MS, reference sample and UV spectrum were selectively used in separation to search for target compounds from HPLC-DAD profiles of different sub-extracts. The structures of isolated compounds were further identified by ESI-MS, 1HNMR and 13CNMR. PMID:21306961

Cao, Xueli; Wang, Qiaoe; Li, Yan; Bai, Ge; Ren, Hong; Ito, Yiochiro

2011-01-01

423

Toward understanding the influence of ethylbenzene in p-xylene selectivity of the porous titanium amino terephthalate MIL-125(Ti): adsorption equilibrium and separation of xylene isomers.  

PubMed

The potential of the porous crystalline titanium dicarboxylate MIL-125(Ti) in powder form was studied for the separation in liquid phase of xylene isomers and ethylbenzene (MIL stands for Materials from Institut Lavoisier). We report here a detailed experimental study consisting of binary and multi-component adsorption equilibrium of xylene isomers in MIL-125(Ti) powder at low (?0.8 M) and bulk (?0.8 M) concentrations. A series of multi-component breakthrough experiments was first performed using n-heptane as the eluent at 313 K, and the obtained selectivities were compared, followed by binary breakthrough experiments to determine the adsorption isotherms at 313 K, using n-heptane as the eluent. MIL-125(Ti) is a para-selective material suitable at low concentrations to separate p-xylene from the other xylene isomers. Pulse experiments indicate a separation factor of 1.3 for p-xylene over o-xylene and m-xylene, while breakthrough experiments using a diluted ternary mixture lead to selectivity values of 1.5 and 1.6 for p-xylene over m-xylene and o-xylene, respectively. Introduction of ethylbenzene in the mixture results however in a decrease of the selectivity. PMID:22260425

Moreira, Mariana A; Santos, João C; Ferreira, Alexandre F P; Loureiro, José M; Ragon, Florence; Horcajada, Patricia; Yot, Pascal G; Serre, Christian; Rodrigues, Alírio E

2012-02-21

424

The effect of azeotropism on combustion characteristics of blended fuel pool fire.  

PubMed

The effect of azeotropism on combustion characteristics of blended fuel pool fire was experimentally studied in an open fire test space of State Key Laboratory of Fire Science. A 30 cm × 30 cm square pool filled with n-heptane and ethanol blended fuel was employed. Flame images, burning rate and temperature distribution were collected and recorded in the whole combustion process. Results show that azeotropism obviously dominates the combustion behavior of n-heptane/ethanol blended fuel pool fire. The combustion process after ignition exhibits four typical stages: initial development, azeotropic burning, single-component burning and decay stage. Azeotropism appears when temperature of fuel surface reaches azeotropic point and blended fuel burns at azeotropic ratio. Compared with individual pure fuel, the effect of azeotropism on main fire parameters, such as flame height, burning rate, flame puffing frequency and centerline temperature were analyzed. Burning rate and centerline temperature of blended fuel are higher than that of individual pure fuel respectively at azeotropic burning stage, and flame puffing frequency follows the empirical formula between Strouhal and Froude number for pure fuel. PMID:24632362

Ding, Yanming; Wang, Changjian; Lu, Shouxiang

2014-04-30

425

Tubular metal-organic framework-based capillary gas chromatography column for separation of alkanes and aromatic positional isomers.  

PubMed

In this work, a tubular metal-organic framework, MOF-CJ3, with a large one-dimensional channel was chosen as stationary phase to prepare a capillary gas chromatographic column via a verified dynamic coating procedure. The column offered good separations of linear and branched alkanes, as well as aromatic positional isomers (ethylbenzene, xylene, cresol, hydroquinone, dichlorobenzene, bromobenzonitrile, chloronitrobenzene, and nitrotoluene) based on a combination of host-guest interactions and adsorption effects. Elution sequence of most of the analytes followed an increasing order of their boiling points, except for the separation of n-heptanes/isooctane, cresol, and hydroquinone isomers. Separation behavior of the column upon different organic substances may be related to the tubular pore structure of MOF-CJ3, in which the van der Waals forces between the alkanes and the hydrophobic inner surfaces might have great effect on separation of n-heptanes and isooctane, whereas the separation of cresol and hydroquinone isomers were affected by (OH?O) hydrogen bonds formed between the analytes and the 1,3,5-benzenetricarboxylate ligands on the pore wall. The effects of temperature on separation of aromatic positional isomers were investigated to elucidate entropy and enthalpy controlling of the separation process. PMID:23473507

Fang, Zhi-Li; Zheng, Sheng-Run; Tan, Jing-Bo; Cai, Song-Liang; Fan, Jun; Yan, Xia; Zhang, Wei-Guang

2013-04-12

426

Laminar burning velocities at high pressure for primary reference fuels and gasoline: Experimental and numerical investigation  

SciTech Connect

Spherical flames of n-heptane, iso-octane, PRF 87 and gasoline/air mixtures are experimentally investigated to determine laminar burning velocities and Markstein lengths under engine-relevant conditions by using the constant volume bomb method. Data are obtained for an initial temperature of 373 K, equivalence ratios varying from {phi}=0.7 to {phi}=1.2, and initial pressures from 10 to 25 bar. To track the flame front in the vessel a dark field He-Ne laser Schlieren measurement technique and digital image processing were used. The propagating speed with respect to the burned gases and the stretch rate are determined from the rate of change of the flame radius. The laminar burning velocities are obtained through a linear extrapolation to zero stretch. The experimentally determined Markstein numbers are compared to theoretical predictions. A reduced chemical kinetic mechanism for n-heptane and iso-octane was derived from the Lawrence Livermore comprehensive mechanisms. This mechanism was validated for ignition delay times and flame propagation at low and high pressures. In summary an overall good agreement with the various experimental data sets used in the validation was obtained. (author)

Jerzembeck, S.; Peters, N. [RWTH, Aachen (Germany); Pepiot-Desjardins, P.; Pitsch, H. [Department of Mechanical Engineering, Stanford University, CA (United States)

2009-02-15

427

A path flux analysis method for the reduction of detailed chemical kinetic mechanisms  

SciTech Connect

A direct path flux analysis (PFA) method for kinetic mechanism reduction is proposed and validated by using high temperature ignition, perfect stirred reactors, and steady and unsteady flame propagations of n-heptane and n-decane/air mixtures. The formation and consumption fluxes of each species at multiple reaction path generations are analyzed and used to identify the important reaction pathways and the associated species. The formation and consumption path fluxes used in this method retain flux conservation information and are used to define the path indexes for the first and the second generation reaction paths related to a targeted species. Based on the indexes of each reaction path for the first and second generations, different sized reduced chemical mechanisms which contain different number of species are generated. The reduced mechanisms of n-heptane and n-decane obtained by using the present method are compared to those generated by the direct relation graph (DRG) method. The reaction path analysis for n-decane is conducted to demonstrate the validity of the present method. The comparisons of the ignition delay times, flame propagation speeds, flame structures, and unsteady spherical flame propagation processes showed that with either the same or significantly less number of species, the reduced mechanisms generated by the present PFA are more accurate than that of DRG in a broad range of initial pressures and temperatures. The method is also integrated with the dynamic multi-timescale method and a further increase of computation efficiency is achieved. (author)

Sun, Wenting; Ju, Yiguang [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544 (United States); Chen, Zheng [State Key Laboratory for Turbulence and Complex Systems, College of Engineering, Peking University, Beijing 100871 (China); Gou, Xiaolong [School of Power Engineering, Chongqing University, Chongqing 400044 (China)

2010-07-15

428

Kinetic modelling of the oxidation of large aliphatic hydrocarbons using an automatic mechanism generation.  

PubMed

A mechanism generator code to automatically generate mechanisms for the oxidation of large hydrocarbons has been successfully modified and considerably expanded in this work. The modification was through (1) improvement of the existing rules such as cyclic-ether reactions and aldehyde reactions, (2) inclusion of some additional rules to the code, such as ketone reactions, hydroperoxy cyclic-ether formations and additional reactions of alkenes, (3) inclusion of small oxygenates, produced by the code but not included in the handwritten C(1)-C(4) sub-mechanism yet, to the handwritten C(1)-C(4) sub-mechanism. In order to evaluate mechanisms generated by the code, simulations of observed results in different experimental environments have been carried out. Experimentally derived and numerically predicted ignition delays of n-heptane-air and n-decane-air mixtures in high-pressure shock tubes in a wide range of temperatures, pressures and equivalence ratios agree very well. Concentration profiles of the main products and intermediates of n-heptane and n-decane oxidation in jet-stirred reactors at a wide range of temperatures and equivalence ratios are generally well reproduced. In addition, the ignition delay times of different normal alkanes was numerically studied. PMID:17687471

Muharam, Yuswan; Warnatz, Jürgen

2007-08-21

429

[Migrants from disposable gloves and residual acrylonitrile].  

PubMed

Disposable gloves made from polyvinyl chloride with and without di(2-ethylhexyl) phthalate (PVC-DEHP, PVC-NP), polyethylene (PE), natural rubber (NR) and nitrile-butadiene rubber (NBR) were investigated with respect to evaporation residue, migrated metals, migrants and residual acrylonitrile. The evaporation residue found in n-heptane was 870-1,300 ppm from PVC-DEHP and PVC-NP, which was due to the plasticizers. Most of the PE gloves had low evaporation residue levels and migrants, except for the glove designated as antibacterial, which released copper and zinc into 4% acetic acid. For the NR and NBR gloves, the evaporation residue found in 4% acetic acid was 29-180 ppm. They also released over 10 ppm of calcium and 6 ppm of zinc into 4% acetic acid, and 1.68-8.37 ppm of zinc di-ethyldithiocarbamate and zinc di-n-butyldithiocarbamate used as vulcanization accelerators into n-heptane. The acrylonitrile content was 0.40-0.94 ppm in NBR gloves. PMID:11775358

Wakui, C; Kawamura, Y; Maitani, T

2001-10-01

430

Oxides of Nitrogen Emissions from the Combustion of Monodisperse Liquid Fuel Sprays. Ph.D. Thesis  

NASA Technical Reports Server (NTRS)

A study of NO sub x formation in a one dimensional monodisperse spray combustion system, which allowed independent droplet size variation, was conducted. Temperature, NO and NO sub x concentrations were measured in the transition region, encompassing a 26 to 74 micron droplet size range. Emission measurements of hydrocarbons, carbon monoxide, carbon dioxide and oxygen were also made. The equivalence ratio was varied between 0.8 and 1.2 for the fuels used, including methanol, isopropanaol, n-heptane and n-octane. Pyridine and pyrrole were added to n-heptane as nitrogen-containing additives in order to simulate synthetic fuels. Results obtained from the postflame regions using the pure fuels indicate an optimum droplet size in the range of 43 to 58 microns for minimizing NO sub x production. For the fuels examined, the maximum NO sub x reductions relative to the small droplet size limit were about 10 to 20% for lean and 20 to 30% for stoichiometric and rich mixtures. This behavior is attributed to droplet interactions and the transition from diffusive to premixed type of burning. Preflame vaporization controls the gas phase stoichiometry which has a significant effect on the volume of the hot gases surrounding a fuel droplet, where NO sub x is formed.

Sarv, H.

1985-01-01

431

Group type analysis of asphalt by column liquid chromatography  

SciTech Connect

An improved analysis method for characterization of asphalt was established. The method is based on column chromatography technique. The asphalts were separated into four groups: saturates, aromatics, resins, and asphaltenes, quantitatively. About 0.1 g of sample was required in each analysis. About 20 mL of n-heptanes was used to separate out saturates first. Then about 35 mL of n-heptanes/dichloromethane (.5, v/v) mixture was used to separate out aromatics. About 30 mL of dichloromethane/tetrahydrofuran (1/3, v/v) mixture was used to separate out resin. The quality of the separation was confirmed by infrared spectra (IR) and {sup 1}H NMR analysis. The model compounds, tetracosan for saturates, dibenz(o)anthracen for aromatics, and acetanilide for resins were used for verification. The IR and {sup 1}H NMR analysis of the prepared fractions from the column liquid chromatography were in good agreement that of pure reagents.

Zhang, C.; Yang, J.; Xue, Y.; Li, Y. [Chinese Academy of Science, Taiyuan (China)

2008-07-01

432

Perinaphthenone phototransformation in a model of leaf epicuticular waxes.  

PubMed

Perinaphthenone (1H-phenalen-1-one, PN) is a reference photosensitizer producing singlet oxygen with a quantum yield close to one in a large variety of solvents. It is also the basic structure of a class of phototoxic phytoalexins. In this work, the PN photoreactivity was studied for the first time in a paraffinic wax, used as model of leaf epicuticular waxes. The PN photodegradation was monitored by UV-Vis spectroscopy. The triplet excited state, singlet oxygen and the hydroxyperinaphthenyl radical were detected by diffuse reflectance laser flash photolysis, near infrared phosphorescence and by EPR spectroscopy, respectively. The PN phototransformation was found to be fivefold faster in the wax than in n-heptane under steady-state irradiation. The hydroxyperinaphthenyl radical formation was observed in aerated irradiated paraffin wax while in n-heptane solution the radical was observed only in the absence of oxygen. These results show that under continuous irradiation, PN is much more easily phototransformed in a solid environment than in solution. Several photoproducts were identified, in particular phenalanone, PN dimers, and oxidized PN-alkanes adducts. Finally, when pyrethrum extract is added into the wax along with PN, the hydroxyperinaphthenyl radical concentration was increased by a factor of 2.4. Such photochemical reactions may occur when systemic pesticides enter the plant cuticle. PMID:24300996

Trivella, Aurélien S; Monadjemi, Shirin; Worrall, David R; Kirkpatrick, Iain; Arzoumanian, Emmanuel; Richard, Claire

2014-01-01

433

Microgravity Droplet Combustion in CO2 Enriched Environments at Elevated Pressures  

NASA Technical Reports Server (NTRS)

Microgravity droplet combustion experiments were performed in elevated concentrations of CO2 at pressures of 1.0 atm, 3.0 atm, and 5.0 atm to examine the effects of a radiatively participating suppression agent in space applications. Methanol and n-heptane droplets, with an initial diameter of 2.0 mm supported on a quartz fiber, were used in these experiments. The ambient O2 concentration was held constant at 21% and the CO2 concentrations ranged from 0% to a maximum of 70%, by volume with the balance consisting of N2 . Results from the methanol tests showed slight decreases in burning rates with increased CO2 concentrations at all ambient pressures. The n-heptane tests show slight increases in burning rates with increasing CO2 concentrations at each pressure level. Instantaneous radiative heat flux was also measured using both a broadband radiometer (i.e., wavelengths from 0.6 microns to 40.0 microns) and a narrowband radiometer (i.e., centered at 5.6 microns with a filter width at half maximum of 1.5 microns). Radiative exchanges between the droplet and surrounding gases as well as the soot field produce departures from the classical quasisteady theory which would predict a decrease in burning rates with increasing CO2 concentrations in microgravity.

Hicks, Michael C.; Nayagam, V.; Williams, F. A.

2007-01-01

434

Structural and diffusion characterizations of steam-stable mesostructured zeolitic UL-ZSM-5 materials.  

PubMed

A series of mesoporous UL-ZSM-5 materials (Si/Al = 50) with different micro- and mesoporosity as well as crystallinity was prepared following the procedure proposed in one of our recent studies (Trong-On, D.; Kaliaguine, S. Angew. Chem. Int. Ed. 2001, 40, 3248-3251. Trong-On, D.; Kaliaguine, S. U.S. Patent 6,669,924, B1, 2003). These materials have zeolitic structure in the form of nanoparticles intergrown in the walls of the amorphous wormhole-like aluminosilicate mesopores of Al-Meso-50, which was used as a precursor in the synthesis. The structure, crystallinity, and textural properties of the synthesized materials, as well as a reference ZSM-5 zeolite sample, were determined by X-ray diffraction (XRD), transmission electron microscopy (TEM)/scanning electron microscoy (SEM) analyses, Fourier transform infrared spectroscopy (FTIR), 27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR), and nitrogen adsorption/desorption techniques. The acid properties were examined by FTIR of adsorbed pyridine. UL-ZSM-5 materials were shown to be highly hydrothermally stable. The diffusion of two C7 hydrocarbons, i.e., n-heptane and toluene, in four UL-ZSM-5 materials with different microporosities, related acidities, and crystallinities were investigated using the zero-length column (ZLC) method. Furthermore, the wormhole-like mesostructured aluminosilicate precursor (Al-Meso-50) and a reference MFI zeolite sample were also investigated using the same technique. A theoretical model considering a combination of mesopore diffusion (with surface slip in the main channels) with an activated, mainly surface diffusion mechanism in the intrawall biporous structure, was proposed and employed to interpret the experimental ZLC results. A classical Knudsen type of diffusion was replaced by an activated surface slip type of diffusion mechanism in the mesopores. The transport of n-heptane in UL-ZSM-5 materials was found to be mainly controlled by mesopore diffusion in the main-channel structure, while that of toluene was dominated by the intrawall diffusion process. Diffusion activation energies of n-heptane are about 2 times higher in comparison to toluene, which has a larger kinetic diameter. The main mesopore channel structure seems to appreciably contribute to the overall mass transport. Furthermore, the effect of hydrothermal treatment (20% steam at 800 degrees C for 24 h) on the diffusion of these two sorbates on UL-ZSM-5 materials was also evaluated. PMID:16649795

Vinh-Thang, Hoang; Huang, Qinglin; Ungureanu, Adrian; Ei?, Mladen; Trong-On, Do; Kaliaguine, Serge

2006-05-01

435

The Impact of Low Octane Hydrocarbon Blending Streams on Ethanol Engine Optimization  

SciTech Connect

Ethanol is a very attractive fuel from an end-use perspective because it has a high chemical octane number and a high latent heat of vaporization. When an engine is optimized to take advantage of these fuel properties, both efficiency and power can be increased through higher compression ratio, direct fuel injection, higher levels of boost, and a reduced need for enrichment to mitigate knock or protect the engine and aftertreatment system from overheating. The ASTM D5798 specification for high level ethanol blends, commonly called E85, underwent a major revision in 2011. The minimum ethanol content was revised downward from 68 vol% to 51 vol%, which combined with the use of low octane blending streams such as natural gasoline introduces the possibility of a lower octane E85 fuel. While this fuel is suitable for current ethanol tolerant flex fuel vehicles, this study experimentally examines whether engines can still be aggressively optimized for the resultant fuel from the revised ASTM D5798 specification. The performance of six ethanol fuel blends, ranging from 51-85% ethanol, is compared to a premium-grade certification gasoline (UTG-96) in a single-cylinder direct-injection (DI) engine with a compression ratio of 12.9:1 at knock-prone engine conditions. UTG-96 (RON = 96.1), light straight run gasoline (RON = 63.6), and n-heptane (RON = 0) are used as the hydrocarbon blending streams for the ethanol-containing fuels in an effort to establish a broad range of knock resistance for high ethanol fuels. Results show that nearly all ethanol-containing fuels are more resistant to engine knock than UTG-96 (the only exception being the ethanol blend with 49% n-heptane). This knock resistance allows ethanol blends made with 33 and 49% light straight run gasoline, and 33% n-heptane to be operated at significantly more advanced combustion phasing for higher efficiency, as well as at higher engine loads. While experimental results show that the octane number of the hydrocarbon blend stock does impact engine performance, there remains a significant opportunity for engine optimization when considering even the lowest octane fuels that are in compliance with the current revision of ASTM D5798 compared to premium-grade gasoline.

Szybist, James P [ORNL] [ORNL; West, Brian H [ORNL] [ORNL

2013-01-01

436

A Detailed Chemical Kinetic Reaction Mechanism for n-Alkane Hydrocarbons From n-Octane to n-Hexadecane  

SciTech Connect

Detailed chemical kinetic reaction mechanisms have been developed to describe the pyrolysis and oxidation of nine n-alkanes larger than n-heptane, including n-octane (n-C{sub 8}H{sub 18}), n-nonane (n-C{sub 9}H{sub 20}), n-decane (n-C{sub 10}H{sub 22}), n-undecane (n-C{sub 11}H{sub 24}), n-dodecane (n-C{sub 12}H{sub 26}), n-tridecane (n-C{sub 13}H{sub 28}), n-tetradecane (n-C{sub 14}H{sub 30}), n-pentadecane (n-C{sub 15}H{sub 32}), and n-hexadecane (n-C{sub 16}H{sub 34}). These mechanisms include both high temperature and low temperature reaction pathways. The mechanisms are based on our previous mechanisms for the primary reference fuels n-heptane and iso-octane, using the reaction class mechanism construction first developed for n-heptane. Individual reaction class rules are as simple as possible in order to focus on the parallelism between all of the n-alkane fuels included in the mechanisms, and these mechanisms will be refined further in the future to incorporate greater levels of accuracy and predictive capability. These mechanisms are validated through extensive comparisons between computed and experimental data from a wide variety of different sources. In addition, numerical experiments are carried out to examine features of n-alkane combustion in which the detailed mechanisms can be used to compare reactivities of different n-alkane fuels. The mechanisms for all of these n-alkanes are presented as a single detailed mechanism, which can be edited to produce efficient mechanisms for any of the n-alkanes included, and the entire mechanism, with supporting thermochemical and transport data, together with an explanatory glossary explaining notations and structural details, will be available for download from our web page.

Westbrook, C K; Pitz, W J; Herbinet, O; Curran, H J; Silke, E J

2008-02-08

437

Electron localization in liquid hydrocarbons: The Anderson model  

NASA Astrophysics Data System (ADS)

Anderson's model is applied for initial localization in liquid hydrocarbons (particularly n-alkanes) in conjunction with certain results of scaling theory. Medium connectivity is calculated using experimental X-ray data on liquid structure, from which critical disorder ( W/ V) c is computed, where W is diagonal disorder and V is the transfer energy. Actual W prevailing in the liquid is computed from anisotropic molecular polarizability. V is estimated by a heuristic procedure originating in scaling theory. These values are used to compute the percentage of initially delocalized states available for low-energy electrons in alkane liquids. This percentage decreases monotonically from methane (100%) to n-pentane and beyond (0%). In ethane and propane, the initial states are highly delocalized (97.6% and 83.9%, respectively). Subsequent trapping changes the situation as evidenced in mobility studies. Butane presents a partially, intermediate delocalized case (53.2%).

Hug, Gordon L.; Mozumder, A.

2008-10-01

438

Fischer Tropsch synthesis in supercritical fluids. Quarterly technical progress report, April 1, 1995--June 30, 1995  

SciTech Connect

Our objective for this quarter was to study the effect of co-feeding a 1-olefin on the Ruhrchemie catalyst activity and selectivity, during-both conventional Fisher-Tropsch synthesis (FTS) and FTS under supercritical conditions. We used propane as the supercritical fluid and 1-dodecene (1-C{sub 12}H{sub 24}) in this test. Motivation for this study was the work of Fujimoto and co-workers who reported that suppression of methane and enhancement of high molecular weight hydrocarbons selectivities occurs with co-feeding of 1-olefins (1-heptene, 1-tetradecene, or 1-hexadecene) during FTS under supercritical conditions, but not during the conventional FTS (Co-La catalyst supported on silica in supercritical n-pentane).The diffusion coefficients of products in supercritical fluids is discussed.

Akgerman, A.; Bukur, D.B.

1996-05-01

439

Pool boiling on a large horizontal flat resistance heater  

SciTech Connect

Results are presented of experiments on n-pentane/Freon-113 system, carried out to investigate the film-transition boiling region where liquid-solid contacts contribute significantly to the local heat flux, using a large flat horizontal resistance heater mounted on a ceramic insulating substrate. After steady film boiling was reached, the heat flux was decreased and recorded simultaneously with the temperature measured by thermocouples attached to the lower side of the heater surface. It is shown that the observed data on the quasi-linear film boiling regime are better represented by Berenson's (1960) correlation than by Klimenko's (1981) correlation. Burnout values measured for Freon-113 compared reasonably well to available correlations for the flat plate geometry. 10 refs.

Reguillot, F.; Witte, L.; Lienhard, J.; Poniewski, M. (Houston, University, TX (United States) Kielce University of Technology, (Poland))

1992-08-01

440

Biodegradation of petroleum by Chesapeake Bay sediment bacteria.  

PubMed

Chesapeake Bay sediment bacteria from oil-contaminated and oil-free environments were compared for their ability to utilize a South Louisiana crude oil. Preferential solubility, column chromatography, gas-liquid chromatography, and computerized mass spectrometry were used to provide new and useful information regarding biodegradation of fractions and components of the crude oil. Vibrio, Pseudomonas, and Acinetobacter spp. were isolated from the culture inoculated with oil-contaminated sediment, whereas coryneforms and Pseudomonas spp. were isolated from the culture inoculated with oil-free sediment. Microorganisms from the oil-free sediment produced greater quantities of polar n-pentane-insoluble components (asphaltenes) after degradation, whereas microorganisms from the oil-contaminated sediments provided greater degradation of saturated and aromatic hydrocarbons. PMID:814987

Walker, J D; Colwell, R R; Petrakis, L

1976-03-01

441

A time-accurate algorithm for chemical non-equilibrium viscous flows at all speeds  

NASA Technical Reports Server (NTRS)

A time-accurate, coupled solution procedure is described for the chemical nonequilibrium Navier-Stokes equations over a wide range of Mach numbers. This method employs the strong conservation form of the governing equations, but uses primitive variables as unknowns. Real gas properties and equilibrium chemistry are considered. Numerical tests include steady convergent-divergent nozzle flows with air dissociation/recombination chemistry, dump combustor flows with n-pentane-air chemistry, nonreacting flow in a model double annular combustor, and nonreacting unsteady driven cavity flows. Numerical results for both the steady and unsteady flows demonstrate the efficiency and robustness of the present algorithm for Mach numbers ranging from the incompressible limit to supersonic speeds.

Shuen, J.-S.; Chen, K.-H.; Choi, Y.

1992-01-01

442

Temperature and moisture effect on spore emission in the fungal biofiltration of hydrophobic VOCs.  

PubMed

The effect of temperature and moisture on the elimination capacity (EC), CO(2) production and spore emission by Fusarium solani was studied in biofilters packed with vermiculite and fed with n- pentane. Three temperatures (15, 25 and 35°C) were tested and the highest average EC (64 g m(-3) h(-1)) and lower emission of spores (2.0 × 10(3) CFU m(-3) air) were obtained at 25°C. The effect of moisture content of the packing material indicates that the highest EC (65 g m(-3) h(-1)) was obtained at 50 % moisture. However, lowest emission (1.3 × 10(3) CFU m(-3) air) was obtained at 80 % moisture. Furthermore, the results show that a slight decrease in spore emission was found with increasing moisture content. In all cases, the depletion of the nitrogen source in the biofilter induced the sporulation, a decay of the EC and increased spore emission. PMID:22375544

Vergara-Fernández, Alberto; Salgado-Ísmodes, Vanida; Pino, Miguel; Hernández, Sergio; Revah, Sergio

2012-01-01

443

Design and testing of a passive, feedback-controlled, variable conductance heat pipe  

NASA Technical Reports Server (NTRS)

A passive feedback system, which stabilizes the heat source temperature (T sub s) of a gas loaded heat pipe, was designed and tested. The control of T sub s is accomplished by an auxiliary liquid that senses the heat source and actuates a metal bellows system due to the liquid's thermal expansion. The movement of the bellows varies the gas reservoir volume and leads to a corresponding change of the condensation area of the heat pipe. With methanol as the heat pipe working fluid and perfluoro-n-pentane as the auxiliary liquid, the control capability was found to be T sub s = 31.5 + or - 1.5 C in a power range from 3 to 30 W, compared to T sub s = 33 + or - 3 C with methanol as auxiliary liquid. The change in T sub s was 35 + or - 5.5 C with the bellows held in the closed position.

Schlitt, K. R.

1973-01-01

444

Microbial removal of alkanes from dilute gaseous waste streams: kinetics and mass transfer considerations.  

PubMed

Treatment of dilute gaseous hydrocarbon waste streams remains a current need for many industries, particularly as increasingly stringent environmental regulations and oversight force emission reduction. Biofiltration systems hold promise for providing low-cost alternatives to more traditional, energy-intensive treatment methods such as incineration and adsorption. Elucidation of engineering principles governing the behavior of such systems, including mass transfer limitations, will broaden their applicability. Our processes exploit a microbial consortium to treat a mixture of 0.5% n-pentane and 0.5% isobutane in air. Since hydrocarbon gases are sparingly soluble in water, good mixing and high surface area between the gas and liquid phases are essential for biodegradation to be effective. One liquid-continuous columnar bioreactor was operated for more than 30 months with continued degradation of n-pentane and isobutane as sole carbon and energy sources. The maximum degradation rate observed in this gas-recycle system was 2 g of volatile organic compounds (VOC)/(m3.h). A trickle-bed bioreactor was operated continuously for over 24 months to provide a higher surface area (using a structured packing) with increased rates. Degradation rates consistently achieved were approximately 50 g of VOC/(m3.h) via single pass in this gas-continuous columnar system. Effective mass transfer coefficients comparable to literature values were also measured for this reactor; these values were substantially higher than those found in the gas-recycle reactor. Control of biomass levels was implemented by limiting the level of available nitrogen in the recirculating aqueous media, enabling long-term stability of reactor performance. PMID:9413140

Barton, J W; Klasson, K T; Koran, L J; Davison, B H

1997-01-01

445

Pressure Effects in Droplet Combustion of Miscible Binary Fuels  

NASA Technical Reports Server (NTRS)

The objective of this research is to improve understanding of the combustion of binary fuel mixtures in the vicinity of the critical point. Fiber-supported droplets of mixtures of n-heptane and n-hexadecane, initially 1 mm in diameter, were burned in room-temperature air at pressures from 1 MPa to 6 MPa under free-fall microgravity conditions. For most mixtures the total burning time was observed to achieve a minimum value at pressures well above the critical pressure of either of the pure fuels. This behavior is explained in terms of critical mixing conditions of a ternary system consisting of the two fuels and nitrogen. The importance of inert-gas dissolution in the liquid fuel near the critical point is thereby re-emphasized, and nonmonotonic dependence of dissolution on initial fuel composition is demonstrated. The results provide information that can be used to estimate high-pressure burning rates of fuel mixtures.

Mikami, Masato; Habara, Osamu; Kono, Michikata; Sato, Jun-Ichi; Dietrich, Daniel L.; Williams, Forman A.

1997-01-01

446

Hydrocarbons identified in extracts from estuarine water accommodated no. 2 fuel oil by gas chromatography-mass spectrometry  

NASA Technical Reports Server (NTRS)

Results are presented on a computerized gas chromatograph-mass spectrometer analysis of methylene chloride and n-heptane extracts of a No. 2 fuel oil accommodated estuarine water sample. The analytical method is briefly described, and the limitations on the identifications are categorized. Some attempt was made to determine major and trace constituents in the water accommodate. Altogether 66 hydrocarbon compounds were identified specifically, and 75 compounds were partially identified. Seven compounds could be recognized as major constituents of the water accommodated oil and ten were present only as traces. The aromatic compounds found were alkyl benzenes, naphthalene, tetralin, indane, biphenyl, fluorene, anthracene, and some of their alkyl substituted isomers in the range of carbon numbers C7 to C15. Four n-alkanes, C10 to C13, were found along with four other assorted hydrocarbons.

Lewis, B. W.; Walker, A. L.; Bieri, R. H.

1974-01-01

447

Soot agglomeration in isolated, free droplet combustion  

NASA Technical Reports Server (NTRS)

Under the conditions of an isolated, free droplet experiment, hollow, carbonaceous structures, called soot spheres, were observed to form during the atmospheric pressure, low Reynolds number combustion of 1-methylnaphthalene. These structures which are agglomerates composed of smaller spheroidal units result from both thermophoretic effects induced by the envelope flame surrounding each drop and aerodynamic effects caused by changes in the relative gas/drop velocities. A chemically reacting flow model was used to analyze the process of sootshell formation during microgravity droplet combustion. The time-dependent temperature and gas property field surrounding the droplet was determined, and the soot cloud location for microgravity combustion of n-heptane droplets was predicted. Experiments showed that the sooting propensity of n-alkane fuel droplets can be varied through diluent substitution, oxygen-index variations, and ambient pressure reductions.

Choi, M. Y.; Dryer, F. L.; Green, G. J.; Sangiovanni, J. J.

1993-01-01

448

Extraction kinetics of rare earth metals with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester using a hollow fiber membrane extractor  

SciTech Connect

A kinetic study concerning chemical complexation-based solvent extraction of rare earth metals with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester dissolved as an extractant in n-heptane was carried out using a microporous hydrophobic hollow fiber membrane extractor. The effects of concentration of chemical species in aqueous and organic feed solutions on the apparent permeabilities of metal species for extraction and stripping, respectively, were investigated to clarify the permeation mechanism. From the experimental results it was predicted that the permeation rate is controlled by diffusion of the chemical species in aqueous and organic phases and by interfacial chemical reaction. The experimental data were analyzed by the diffusion model accompanied with an interfacial reaction, taking into account the velocity distributions of the aqueous and organic phases through the inner and outer sides of the hollow fiber.

Kubota, Fukiko; Goto, Masahiro; Nakashio, Fumiyuki [Kyushu Univ., Fukuoka (Japan); Hano, Tadashi [Oita Univ. (Japan)

1995-03-01

449

Extraction of rare earth metals with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester in the presence of diethylenetriaminepentaacetic acid in aqueous phase  

SciTech Connect

The extraction equilibria of rare earth metals with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (commercial name, PC-88A, henceforth abbreviated as HR) dissolved in n-heptane were measured at 303 K. It was found that rare earth metals are extracted with the dimer of the extractant, (HR){sub 2}, as follows. M{sub aq}{sup 3+} + 3(HR){sub 2 org} MR{sub 3} {center_dot} 3HR{sub org} + 3H{sub aq}{sup +} The extraction equilibrium constants of metals were obtained and compared with the extraction equilibrium constants obtained by di(2-ethylhexyl)phosphoric acid (henceforth DZEHPA). Furthermore, the extraction equilibria of rare earth metals with PC-88A in the presence of diethylenetriaminepentaacetic acid (henceforth DTPA) in an aqueous phase were also measured to discuss the effect of DTPA on the extraction of rare earth metals. 13 refs., 8 figs., 2 tabs.

Kubota, Fukiko; Goto, Masahiro; Nakashio, Fumiyuki [Kyushu Univ., Fukuoka (Japan)

1993-07-01

450

Average structural analysis of tar obtained from pyrolysis of wood.  

PubMed

Conventional analytical methods such as (1)H NMR, vapor pressure osmometry (VPO) and elemental analysis were used to characterize the tar obtained from pyrolysis of pine. The major fraction of tar obtained during pyrolysis of pine at different temperatures was the insoluble fraction in n-heptane which corresponds to asphaltenes; this fraction was characterized and analyzed using average structural parameters. The structural unit of the tar is composed of one aromatic ring substituted by aliphatic chains, olefinic groups and the presence of oxygenated groups. Two of such average structures determined with this methodology corresponds to 4-formyl-2,6-dimethoxy-3-[(1E)-prop-1-en-1-yl]-5-propylbenzoic acid and 2,3,5-trimethoxy-6-[(1E)-prop-1-en-1-yl]-4-propylbenzaldehyde. PMID:19962881

López, Diana; Acelas, Nancy; Mondragón, Fanor

2010-04-01

451

Characterization of four potential laser-induced fluorescence tracers for diesel engine applications.  

PubMed

Four potential laser-induced fluorescence (LIF) tracers, 1-phenyloctane, 1-phenyldecane, 1-methylnaphthalene, and 2-methylnaphthalene, are characterized for diesel engine applications. These tracers, embedded in the diesel primary reference fuels n-C??H?? and iso-C??H??, match the relevant physical properties of commercial diesel fuel much better than the commonly used toluene/iso-octane/n-heptane tracer-fuel system does. The temperature and pressure dependencies of the fluorescence intensities and spectra were measured in a flow cell in nitrogen for each candidate tracer molecule. The results show that the signal intensities of the methylnaphthalenes are about two orders of magnitude higher than for 1-phenyloctane and 1-phenyldecane and show a strong temperature but no pressure, dependence. An analysis of the fluorescence spectrum of 1-methylnaphthalene shows that it also can be used for two-color detection LIF thermometry by choosing appropriate optical filters. PMID:24513750

Trost, Johannes; Zigan, Lars; Leipertz, Alfred; Sahoo, Dipankar; Miles, Paul C

2013-11-20

452

Ignition Quality Tester (IQT): An Alternative for Characterizing the Combustion Kinetics of Low Volatility Fuels  

SciTech Connect

The Ignition Quality Tester (IQT) is a constant volume spray combustion system that can be heated and pressurized to conditions that are similar to a diesel engine at top dead center. With no moving parts and the ability to handle low volatility fuels, the IQT can be a bridge between engines and traditional methods for studying chemical kinetics. By comparing experimental data with model predictions, the IQT has been used to validate skeletal kinetic models of ignition. CFD modeling of the IQT using KIVA-3V was used to predict ignition of n-heptane accurately. Operating the IQT in a regime where chemical kinetics dominates (long ignition delays) allowed NTC behavior to be observed for some isomers of heptane. Experimental results with the low volatility fuel heptamethylnonane also show NTC behavior. At long ignition delays, experimental results can be compared with 0-D detailed chemical mechanisms.

Osecky, E.; Bogin, G.; Ratcliff, M.; Luecke, J.; Chen, J. Y.; Zigler, B. T.

2013-01-01

453

Solution-phase photochemistry of a [FeFe]hydrogenase model compound: Evidence of photoinduced isomerisation  

SciTech Connect

The solution-phase photochemistry of the [FeFe] hydrogenase subsite model ({mu}-S(CH{sub 2}){sub 3}S)Fe{sub 2}(CO){sub 4}(PMe{sub 3}){sub 2} has been studied using ultrafast time-resolved infrared spectroscopy supported by density functional theory calculations. In three different solvents, n-heptane, methanol, and acetonitrile, relaxation of the tricarbonyl intermediate formed by UV photolysis of a carbonyl ligand leads to geminate recombination with a bias towards a thermodynamically less stable isomeric form, suggesting that facile interconversion of the ligand groups at the Fe center is possible in the unsaturated species. In a polar or hydrogen bonding solvent, this process competes with solvent substitution leading to the formation of stable solvent adduct species. The data provide further insight into the effect of incorporating non-carbonyl ligands on the dynamics and photochemistry of hydrogenase-derived biomimetic compounds.

Kania, Rafal; Hunt, Neil T. [Department of Physics, University of Strathclyde, SUPA, Glasgow G4 0NG (United Kingdom); Frederix, Pim W. J. M. [Department of Physics, University of Strathclyde, SUPA, Glasgow G4 0NG (United Kingdom); WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow G1 1XL (United Kingdom); Wright, Joseph A.; Pickett, Christopher J. [Energy Materials Laboratory, School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ (United Kingdom); Ulijn, Rein V. [WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow G1 1XL (United Kingdom)

2012-01-28

454

Emulsion liquid membrane extraction of lactic acid from aqueous solutions and fermentation broth.  

PubMed

Studies on the batch extraction of lactic acid using an emulsion liquid membrane system are reported. The membrane phase consists of the tertiary amine carrier Alamine 336 and the surfactant Span 80 dissolved in n-heptane/paraffin and aqueous solutions of sodium carbonate in the internal phase. The effects of internal phase reagent, extraction temperature, and initial external phase pH on the extraction efficiency and the emulsion swelling are examined. A statistical factorial experiment on extraction from clarified lactic acid fermentation broth was carried out to obtain knowledge of the performance of the extraction system from a broth. The extraction efficiency from the fermentation broth is found to be lower as compared to aqueous solutions of pure lactic acid. The effect of pH and the presence of other ionic species on selectivity are discussed. PMID:18609647

Schöller, C; Chaudhuri, J B; Pyle, D L

1993-06-01

455

Figure S1. Relative contribution to total OH reactivity (a), of observed VOCs to calculated OH reactivity (b) and alkyl nitrate production (c,d) in the afternoon (12pm  

E-print Network

.223 5.61E-12(5) 0.0065 0.045 n-Heptane 0.073 0.28 7.15E-12(2) 0.0029 0.015 Cis-2-butene 0.020 0.037 5(1) 0 0.14 1-butene 0.040 0.025 3.17E-11(3) 0.00056 0.043 #12;3 1-pentene 0.023 0.05 3.18E-11(3) 0.00068 0.026 2-methyl-1-butene 0.022 0.03 6.10E-11(6) 0.00083 0.054 3-methyl-1-butene 0.0055 0.025 3.22E-11

Meskhidze, Nicholas

456

The thermal conductivity of liquid mixtures at elevated pressures  

SciTech Connect

This paper reports new, absolute measurements of the thermal conductivity of liquid mixtures of n-heptane and isooctane in the pressure range 0.1 to 430 MPa for temperatures of 307.85 and 337.15 K. The results represent a preliminary investigation of the advantages of attempting to describe the isothermal composition dependence of the thermal conductivity of liquid mixtures along isochores, rather than isobars as has been traditional. However, no significant differences were found between the composition dependences in the two circumstances, possibly due to the lack of experimental data on the density of these mixtures. The availability of a theoretical description of the isochoric composition dependence suggests that this is the most appropriate description which reinforces the need for further high-pressure measurements of the thermal conductivity and density.

Fareleira, J.M.N.A. (Instituto Superior Tecnico, Lisbon (Portugal)); Li, S.F.Y. (National Univ. of Singapore (Singapore)); Wakeham, W.A. (Imperial College, London (England))

1989-09-01

457

Solution-phase photochemistry of a [FeFe]hydrogenase model compound: evidence of photoinduced isomerisation.  

PubMed

The solution-phase photochemistry of the [FeFe] hydrogenase subsite model (?-S(CH(2))(3)S)Fe(2)(CO)(4)(PMe(3))(2) has been studied using ultrafast time-resolved infrared spectroscopy supported by density functional theory calculations. In three different solvents, n-heptane, methanol, and acetonitrile, relaxation of the tricarbonyl intermediate formed by UV photolysis of a carbonyl ligand leads to geminate recombination with a bias towards a thermodynamically less stable isomeric form, suggesting that facile interconversion of the ligand groups at the Fe center is possible in the unsaturated species. In a polar or hydrogen bonding solvent, this process competes with solvent substitution leading to the formation of stable solvent adduct species. The data provide further insight into the effect of incorporating non-carbonyl ligands on the dynamics and photochemistry of hydrogenase-derived biomimetic compounds. PMID:22299905

Kania, Rafal; Frederix, Pim W J M; Wright, Joseph A; Ulijn, Rein V; Pickett, Christopher J; Hunt, Neil T

2012-01-28

458

Extraction and separation of thorium(IV) from lanthanides(III) with room-temperature ionic liquids containing primary amine N{sub 1923}  

SciTech Connect

The extraction behavior of Th(IV) by primary amine N{sub 1923} in imidazolium-based ionic liquid namely 1-octyl-3-methylimidazolium hexafluorophosphate (N{sub 1923}/IL) was studied in this paper. Results showed that N{sub 1923}/IL had poorer extraction ability for Th(IV) than N{sub 1923} in n-heptane (N{sub 1923}/HEP). The separation coefficients between Th(IV) and lanthanides(III) ({beta}{sub Th/Ln}) were obtained and compared with those in the N{sub 1923}/HEP system. On this basis, we made a preliminary assessment for the possibility of using ionic liquids as solvents for the separation of Th(IV) from lanthanides(III) sulfate in a clean process. (authors)

Zuo, Y. [Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Graduate School of Chinese Academy of Sciences, Beijing (China); Chen, J.; Bai, Y.; Li, D.Q. [Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)

2008-07-01

459

Preparation and characterization of polyethylene glycol diacrylate microgels using electron beam radiation  

NASA Astrophysics Data System (ADS)

The use of microemulsion in the development of nanosized gels based on polyethylene glycol diacrylate (PEGDA) is demonstrated. PEGDA was solubilized in n-heptane with use of sodium docusate (AOT) at 0.15M concentration to form reverse micelles. These micelles were than irradiated at 5, 10, 15, 20 and 25 kGy using electron beam (EB) to crosslink the entrapped polymer in the micelles. Ionizing radiation was imparted to the emulsions to generate crosslinking reaction in the micelles formed. The nanosized gels were evaluated in terms of particle diameter using dynamic light scattering (DLS) and the images of the nanosized gels were studied using transmission electron microscopy (TEM). Results show that the size and shape of the particles are influenced by concentration of PEGDA and radiation dose. This study showed that this method can be utilized to produce nanosized gels.

Hamzah, Mohd Yusof; Isa, Naurah Mat; Napia, Liyana M. Ali

2014-02-01